TECHNICAL SUPPORT DOCUMENT FOR PROCESS 

EMISSIONS FROM ELECTRONICS MANUFACTURE 

(e.g., MICRO-ELECTRO-MECHANICAL SYSTEMS, 

LIQUID CRYSTAL DISPLAYS, PHOTOVOLTAICS, 

AND SEMICONDUCTORS ): 

 PROPOSED RULE FOR MANDATORY REPORTING 

OF GREENHOUSE GASES 

REVISED – NOVEMEBER 2010 

 Office of Air and Radiation 

U.S. Environmental Protection Agency 
Subpart I Technical Support Document 

DISCLAIMER 

The Environmental Protection Agency (EPA) regulations cited in this technical support document (TSD) contain legallybinding requirements. 

In several chapters this TSD offers illustrative examples for complying with the minimum requirements indicated by the 

regulations. This is done to provide information that may be helpful for reporters’ implementation efforts. Such 

recommendations are prefaced by the words “may” or “should” and are to be considered advisory. They are not required 

elements of the regulations cited in this TSD. Therefore, this document does not substitute for the regulations cited in this 

TSD, nor is it a regulation itself, so it does not impose legally-binding requirements on EPA or the regulated community. It 

may not apply to a particular situation based upon the circumstances. Mention of trade names or commercial products does 

not constitute endorsement or recommendation for use. 

While EPA has made every effort to ensure the accuracy of the discussion in this document, the obligations of the regulated 

community are determined by statutes, regulations or other legally binding requirements. In the event of a conflict between 

the discussion in this document and any statute or regulation, this document would not be controlling.
Subpart I Technical Support Document 

TABLE OF CONTENTS 

1 SOURCE DESCRIPTION 1 

1.1 TOTAL U.S. EMISSIONS ................................................................................................................................ 2

1.2 GHGS TO BE REPORTED .............................................................................................................................. 2

2 OPTIONS FOR AND SELECTION OF REPORTING THRESHOLD 3 

2.1 OPTIONS CONSIDERED FOR REPORTING THRESHOLDS ............................................................................ 3

2.2 EMISSIONS-BASED THRESHOLD CALCULATIONS ...................................................................................... 4

2.3 REPORTER THRESHOLD APPLICABILITY DETERMINATIONS.................................................................... 5

3 OPTIONS FOR EMISSIONS CALCULATION AND MONITORING METHODS 7 

3.1 OPTIONS FOR ESTIMATING FLUORINATED GHG EMISSIONS FROM ETCHING AND CLEANING............. 7

3.1.1 2006 IPCC TIER 1 METHOD........................................................................................................................ 8

3.1.2 2006 IPCC TIER 2A METHOD...................................................................................................................... 9

3.1.3 2006 IPCC TIER 2B METHOD...................................................................................................................... 9

3.1.4 MODIFIED TIER 2B METHOD..................................................................................................................... 10

3.1.5 TIER 2C METHOD (DEFAULTS FOR 5 PROCESS TYPES/SUBTYPES) ........................................................... 10

3.1.6 THE REFINED METHOD (DEFAULTS FACTORS FOR 9 PROCESS TYPES/SUBTYPES) .................................. 10

3.1.7 TIER 2D METHOD (DEFAULTS FOR 4 PROCESS TYPES/SUBTYPES, RECIPE-SPECIFIC EMISSION FACTORS 

FOR 1 PROCESS TYPE) ............................................................................................................................... 11

3.1.8 2006 IPCC TIER 3 METHOD...................................................................................................................... 12

3.1.9 HYBRID APPROACH A............................................................................................................................... 13

3.1.10 HYBRID APPROACH B ............................................................................................................................. 13

3.1.11 CONTINUOUS EMISSIONS MONITORING SYSTEMS (CEMS).................................................................... 13

3.2 OPTIONS FOR ESTIMATING FACILITY GAS CONSUMPTION .................................................................... 13

3.2.1 IPCC DEFAULT HEEL FACTOR.................................................................................................................. 14

3.2.2 GAS-AND FACILITY-SPECIFIC HEEL FACTORS.......................................................................................... 14

3.3 OPTION FOR APPORTIONING GAS CONSUMPTION................................................................................... 15

3.3.1 EXAMPLE OF FACILITY-SPECIFIC ENGINEERING MODEL BASED ON WAFER PASS.................................. 16

3.4 OPTIONS FOR ESTIMATING NITROUS OXIDE (N2O) EMISSIONS ............................................................. 17

3.5 OPTIONS FOR ESTIMATING HEAT TRANSFER FLUIDS (HTFS) EMISSIONS ............................................ 18

3.5.1 IPCC TIER 1 APPROACH ........................................................................................................................... 18

3.5.2 IPCC TIER 2 APPROACH ........................................................................................................................... 18

3.6 OPTIONS FOR REPORTING CONTROLLED EMISSIONS FROM ABATEMENT SYSTEMS............................ 19

3.6.1 PROPER INSTALLATION, OPERATION, AND MAINTENANCE...................................................................... 19

3.6.2 MONITORING ABATEMENT SYSTEM UPTIME............................................................................................ 19

3.6.3 EPA DEFAULT DRE VALUE ..................................................................................................................... 20

3.6.4 PROPER MEASUREMENT OF ABATEMENT SYSTEM DRE .......................................................................... 22

4 QA/QC REQUIREMENTS 22 
Subpart I Technical Support Document 

5 PROCEDURES FOR ESTIMATING MISSING DATA 23 

6 REPORTING AND RECORDKEEPING PROCEDURES 23 

7 REFERENCES 27 

APPENDIX A - DEFAULT EMISSION FACTORS FOR THRESHOLD APPLICABILITY 

DETERMINATION AND ETCH AND CLEAN EMISSION ESTIMATION METHODS 29 

APPENDIX B - DEVELOPMENT OF EPA PUBLISHED EMISSION FACTORS FOR THE 

TIER 2C AND TIER 2D METHODS 34 

APPENDIX C – EVALUATION OF UNCERTAINTY ASSOCIATED WITH ALTERNATIVE 

EMISSION ESTIMATION METHODS 39 

APPENDIX D - SUPPORT FOR EPA’S DEFINITION OF SIMILAR RECIPE 45 
Subpart I Technical Support Document 

TABLE OF FIGURES 

FIGURE 3-1. TYPOLOGY FOR CALCULATING FLUORINATED GHG EMISSIONS FROM ELECTRONICS 

MANUFACTURING....................................................................................................................................................... 8

FIGURE 3-2. EXPECTED SEMICONDUCTOR FACILITY CONTRIBUTIONS TO TOTAL EMISSIONS ..................... 8

FIGURE B-1. DATA FORM SUBMITTED BY SEMICONDUCTOR DEVICE MANUFACTURERS AND EQUIPMENT 

MANUFACTURERS TO SEMI.................................................................................................................................... 37

FIGURE D-1. RIE ETCHING SHOWING (A) SPUTTERING, (B) CHEMICAL ETCHING AND (C) SPUTTERING 

AND CHEMICAL ETCHING....................................................................................................................................... 46

FIGURE D-2. ILLUSTRATION OF HYSICAL AND CHECMIAL PROCESSES AND INTERATCTION DURING CF4 

PLASMA ETCHING OF SINX FILM ........................................................................................................................... 48

FIGURE D-3. C2F6 EMISSIONS VS C2F6 INLET FLOW RATE & PRESSURE AT 1:1 OXYGEN: C2F6 RATIO........... 51

TABLE OF TABLES 

TABLE 1-1. SELECTED FLUORINATED GREENHOUSE GASES USED BY THE ELECTRONICS INDUSTRY ....... 1

TABLE 2-1. EMISSIONS-BASED THRESHOLD FOR ELECTRONICS MANUFACTURE (1,000, 10,000, 25,000 AND 

100,000 MT CO2E) .......................................................................................................................................................... 3

TABLE 2-2. RULE APPLICABILITY UNDER THE PROPOSED EMISSIONS-BASED THRESHOLDS....................... 4

TABLE 3-1. ILLUSTRATIVE CALCULATION FOR NF3 EXAMPLE AT ONE FACILITY........................................... 17

TABLE 3-2. ILLUSTRATIVE VERIFICATION FOR HYPOTHETICAL FACILITY-SPECIFIC GAS APPORTIONING 

MODEL.......................................................................................................................................................................... 17

TABLE 3-3. DATA SET TO DEVELOP EPA DEFAULT DRE VALUE ........................................................................... 21

TABLE 3-4. SUMMARY STATISTICS AND DEFAULT DRE (LOWER ONE-SIDED TOLERANCE INTERVAL) .... 22

TABLE A-1. DEFAULT EMISSION FACTORS FOR THRESHOLD APPLICABILITY DETERMINATION. .............. 29

TABLE A-2. DEFAULT EMISSION FACTORS (1-UIJ) FOR GAS UTILIZATION (UIJ) AND BY-PRODUCT 

FORMATION RATES (BIJK) FOR MEMS, LCD, AND PV MANUFACTURING..................................................... 30

TABLE A-3. DEFAULT EMISSION FACTORS (1-UIJ) FOR GAS UTILIZATION (UIJ) AND BY-PRODUCT 

FORMATION RATES (BIJK) FOR SEMICONDUCTOR MANUFACTURING FOR 150 MM AND 200 MM 

WAFER SIZES .............................................................................................................................................................. 31

TABLE A-4. DEFAULT EMISSION FACTORS (1-UIJ) FOR GAS UTILIZATION S (UIJ) AND BY-PRODUCT 

FORMATION RATES (BIJK) FOR SEMICONDUCTOR MANUFACTURING FOR 300 MM WAFER SIZE ..... 32

TABLE C-1. ANALOGIES MADE FOR EFS AND ERS FOR VARIOUS FLUORINATED GHGS FOR THE 

ALTERNATIVE 

METHODOLOGIES...................................................................................................................40

TABLE C-2. COMPARISON OF NOMINAL AND SIMULATED MEAN EMISSIONS (MMTCE) AND NORMALIZED 

ESTIMATES OF PEE FOR FIVE ALTERNATICE EMISSION ESTIMATION METHODS............................42

TABLE D-1 CHANGES IN NF3 EMISSIONS (KGCE) AND UTILIZATION FOR VARIOUS INDICATED CHANGES 

IN PARAMETERS FOR IN-SITU CHAMBER-CLEANING PROCESS.................................................................... 52

TABLE D-2. AFFECT OF ±10 PERCENT CHANGES IN O2 AND N2O FLOW RATES ON C3F8 UTILIZATION AND 

CF4 BY-PRODUCT FORMATION DURING NITRIDE AND OXIDE IN SITU PLAMSA CHAMBER CLEANING

........................................................................................................................................................................................ 52
Subpart I Technical Support Document 

November 2010 1

1 Source Description 

The electronics industry uses multiple long-lived fluorinated greenhouse gases (fluorinated GHGs), as well as nitrous oxide 

(N2O) during manufacturing of electronic devices, including, but not limited to, liquid crystal displays (LCDs), microelectro-mechanical systems (MEMS), photovoltaic cells (PV), and semiconductors (including light-emitting diodes 

(LEDs)1). Fluorinated GHGs are used mainly for plasma etching of silicon materials, cleaning deposition tool chambers, 

and wafer cleaning, but may be used in other types of electronics manufacturing processes. Besides dielectric film etching 

and chamber cleaning, much smaller quantities of fluorinated GHGs are used to etch polysilicon films and refractory metal 

films like tungsten. Additionally, some electronics manufacturing equipment may employ fluorinated GHG liquids as heat 

transfer fluids (HTFs). The most common fluorinated GHGs in use are trifluoromethane (HFC-23 or CHF3), 

perfluoromethane (CF4), perfluoroethane (C2F6), nitrogen trifluoride (NF3), and sulfur hexafluoride (SF6), although other 

compounds such as perfluoropropane (C3F8) and perfluorocyclobutane (c-C4F8) are also used (EPA, 2008a). Table 1-1 

presents examples of fluorinated GHGs known to be used during manufacture of different types of electronics. N2O, 

another GHG used in the manufacture of electronics, is used in depositing certain films and other manufacturing processes. 

Table 1-1. Selected Fluorinated Greenhouse Gases Used by the Electronics Industry 

Product Type Fluorinated GHGs Used During Manufacture 

Semiconductor CF4, C2F6, C3F8, c-C4F8, c-C4F8O, C4F6, C5F8, CHF3, CH2F2, NF3, SF6, and HTFs.a

MEMSb CF4, c-C4F8, and SF6

LCD CF4, CHF3, c-C4F8, NF3, and SF6

PV CF4, C2F6, CHF3, C3F8, NF3, SF6 a For commonly used heat transfer fluids please refer to the U.S. EPA report entitled “Uses and Emissions of Liquid PFC Heat Transfer Fluids” 

available at: http://www.epa.gov/semiconductor-pfc/documents/pfc_heat_tranfer_fluid_emission.pdf. b IPCC guidelines do not specify the fluorinated GHGs used by the MEMS industry. Literature reviews revealed that among others, CF4, SF6, and the 

Bosch process (e.g., Bosch process consists of alternating steps of SF6 and C4F8) are used to manufacture MEMS. 

Source: IPCC, 2006; Lyshevshi, S., 2001; Gaitan, M. & Takacs, M., 2008. 

The electronics manufacture source category consists of the five production processes described below. 

• The etching process uses plasma-generated fluorine atoms and other reactive fluorine-containing fragments, which 

chemically react with exposed thin-films (e.g., dielectric, metals) or substrate (e.g., silicon), to selectively remove 

the desired portions of the material. The material removed, as well as undissociated fluorinated gases, flow into 

waste streams and, unless abatement systems are employed, into the atmosphere. 

• Chambers used for depositing dielectric films are cleaned periodically using plasma-generated fluorine atoms and 

other reactive fluorine-containing fragments and other gases, such as N2O. During the cleaning cycle the gas is 

converted to fluorine atoms in plasma, which etches away residual material from chamber walls, electrodes, and 

chamber hardware. Undissociated fluorinated gases and other products pass from the chamber to waste streams 

and, unless abatement systems are employed, are emitted into the atmosphere. 

• During wafer processing, any residual photoresist material can be removed through an ashing process, which 

consists of placing partially processed wafers in an oxygen plasma to which CF4 may be added. The edges of 

wafers (the bevel) may also require cleaning to remove yield-reducing residual material. Bevel cleaning may also 

use a plasma process with fluorinated GHG chemistry. In both of these wafer cleaning processes, unused 

fluorinated GHGs are emitted unless abated. 

• Deposition is a fundamental step in the fabrication of a variety of electronic devices. During deposition, layers of 

dielectric, barrier, or electrically conductive films are deposited or grown on a wafer or other substrate. Chemical 

vapor deposition (CVD) enables the deposition of dielectric or metal films. During the CVD process, gases that 

contain atoms of the material to be deposited react on the wafer surface to form a thin film of solid material. Films 

deposited by CVD may be silicon oxide, single-layer crystal epitaxial silicon, amorphous silicon, silicon nitride, 

 

1 LEDs are a semiconductor light source. When a LED is switched on electrons are able to recombine with holes within the device, 

releasing energy in the form of light whose color is governed by the nature of the semiconductor. Many LEDs are manufactured on a 

wafer (usually different than silicon) using methods that are similar to the manufacture of integrated circuits. 
Subpart I Technical Support Document 

November 2010 2

dielectric anti-reflective coatings, low-k dielectric, aluminum, titanium, titanium nitride, polysilicon, tungsten, 

refractory metals or silicides. N2O may be the oxidizer of choice during deposition of silicon oxide films. 

• Additionally, fluorinated GHG liquids are frequently used as HTFs at semiconductor facilities to cool process 

equipment, to control temperature during device testing, to clean substrate surfaces and other parts, and for 

soldering, and their high vapor pressures can lead to evaporative losses during use (EPA, 2008b; IPCC, 2006). 

Other electronics manufacturing facilities may also employ HTFs for similar uses. HTFs commonly used in 

electronics manufacturing include those sold under the trade names “Galden®” and “FluorinertTM.” 

1.1 Total U.S. Emissions 

Emissions of fluorinated GHGs from 216 electronics manufacturing facilities were estimated to be 6.0 Tg CO2e in 

2006. Below is a breakdown of emissions by electronics product type. 

• Semiconductor: Emissions of fluorinated GHGs, including emissions from the use of HTFs, from 175 facilities 

were estimated to be 5.74 Tg CO2e in 2006 (EPA, 2008a; Burton, C.S., & Beizaie, R., 2001; ITRS, 2008; SEMI, 

2008; VLSI Research, Inc., 2008).2 Of the total semiconductor emissions 5.19 Tg CO2e are from etching/chamber 

cleaning at full-scale facilities and 0.55 Tg CO2e are from HTF usage from all facilities.3 Only etching/cleaning 

emissions from full-scale facilities are accounted for in the U.S. Inventory of GHG Emissions and Sinks (EPA, 

2008a). Partners of the PFC Reduction/Climate Partnership for Semiconductors comprise approximately 80 

percent of U.S. semiconductor production capacity. These Partners have committed to reduce their emissions 

(exclusive of HTF emissions) to 10 percent below their 1995 levels by 2010, and their emissions have been on a 

general decline toward attainment of this goal since 1999. 

• MEMS: Emissions of fluorinated GHGs from 12 facilities were estimated to be 0.15 Tg CO2e in 2006 (SEMI, 

2008.4 

• LCD: Emissions of fluorinated GHGs from 9 facilities were estimated to be 0.02 Tg CO2e in 2006 (DisplaySearch, 

2007).5

• PV: Emissions of fluorinated GHGs from 20 PV facilities were estimated to be 0.07 Tg CO2e in 2006 (Burton, 

2006; Roedern, B.V. & Ullal, H.S., 2008; Earth Policy Institute, 2007).6

1.2 GHGs to be Reported 

EPA is requiring the electronics industry to report emissions and consumption from the following processes and activities: 

• Fluorinated GHGs emitted from plasma etching. 

• Fluorinated GHGs emitted from chamber cleaning. 

• Fluorinated GHGs emitted from wafer cleaning. 

• N2O emitted from chemical vapor deposition or other electronics manufacturing processes. 

• Fluorinated GHGs emitted from use of HTFs. 

 

2 Total semiconductor facilities include both full-scale, pilot, and R&D facilities. 

3 All full scale facilities are assumed to have the same utilization. 

4 The estimated total number of MEMS facilities in the U.S. is an underestimate. The estimate was based on the World Fab Watch 

database, which provides an incomplete listing of total U.S. MEMS facilities (SEMI, 2007). 

5 Estimated total LCD facilities include LCOS, a-Si TFT-LCDs, OLEDs (assuming active matrix), HTPS, TFT, Single Crystal AMLCD, 

LTPS facilities. Where, TFT = Thin Film Transistor; LCOS = Liquid Crystal on Silicon; a-Si = amorphous silicon; OLED = Organic

Light Emitting Diode; HTPS = High Temperature Polysilicon; and AMLCD = Active Matrix Liquid Crystal Display. 

6 Estimated total PV facilities includes only silicon based PV facilities (both crystalline and amorphous silicon based PV facilities are 

included). 
Subpart I Technical Support Document 

November 2010 3

• Consumption of all fluorinated GHGs and N2O, including gases used for manufacturing processes other than those 

listed above. 

• CO2, CH4, and N2O combustion emissions from stationary combustion units by following the requirements of 40 

CFR part 98, subpart C (General Stationary Fuel Combustion Sources).7

2 Options for and Selection of Reporting Threshold 

2.1 Options Considered for Reporting Thresholds 

EPA evaluated a range of emissions threshold options for electronics manufacturing facilities.8 This range included 

emissions thresholds of 1,000, 10,000, 25,000, and 100,000 metric tons CO2e per year for each type of electronics device 

manufacturing facility. Table 2-1 shows these emissions-based threshold options and the number of electronics 

manufacturing facilities that are expected to be captured by the respective emissions thresholds. EPA selected 25,000 

metric tons CO2e per year threshold, which covers 44 percent of electronics manufacturing facilities and 94 percent of the 

industry’s national emissions, thereby maximizing emissions reporting while excluding small facilities that do not 

contribute significantly to the overall GHG emissions. 

Table 2-1. Emissions-Based Threshold for Electronics Manufacture (1,000, 10,000, 25,000 and 100,000 Mt CO2e) 

Emissions Covered Facilities Covered 

Emission Threshold 

Level 

(Metric tons CO2e/yr) 

Total 

National 

Emissions 

(MtCO2e) 

Total National 

Facilities 

Metric tons 

CO2e/yr Percent Facilities Percent 

1,000 5,984,463 216 5,962,091 99.6% 165 76% 

10,000 5,984,463 216 5,813,200 97% 114 53% 

25,000 5,984,463 216 5,622,570 94% 94 44% 

100,000 5,984,463 216 4,737,622 79% 55 26% 

Table 2-2 shows the estimated emissions that would be covered and number of facilities that would report for each type of 

electronics manufacturing facility; semiconductors, MEMS, LCD, and PV, under the 25,000 metric tons CO2e emissionsbased threshold. The emissions-based threshold is estimated to include approximately 50 percent of facilities that 

manufacture semiconductors and approximately 17 percent and 5 percent of the facilities manufacturing MEMS and PV, 

respectively. At the same time, the threshold is expected to cover 96 percent of fluorinated GHG emissions from facilities 

that manufacture semiconductors, 66 percent of fluorinated GHG emissions from facilities manufacturing MEMS, and 47 

percent of fluorinated GHG emissions from facilities manufacturing PVs. 

 

7 On-site combustion emissions from electronics manufacturing facilities are not addressed within this document; please see the 

Technical Support Document for Stationary Combustion (EPA-HQ-OAR-2008-0508-046) for more information. 

8 For more details on the subpart I threshold analysis, please see the Subpart I Detailed Threshold Analysis available in the docket, EPAHQ-OAR-2009-0927. 
Subpart I Technical Support Document 

November 2010 4

Facilities that manufacture LCDs are not expected to meet the 25,000 Mt CO2e threshold; however, the information 

available and used in the analysis at this time is limited and incomplete. Facilities that manufacture LCDs are nonetheless 

covered by the rule because they use similar fluorinated GHG and N2O manufacturing processes as semiconductor 

manufacturing, and because emissions are expected to increase due to high growth in the LCD manufacturing. 

As part of this analysis, EPA also evaluated facilities that manufacture LEDs in the US. There are only a few facilities that 

manufacture LEDs in the US; however, the data that was used at this time is dated, limited, and incomplete. With a strong 

demand for energy efficient lighting, LED manufacturing is poised for high growth in the coming years. According to 

recent industry trade association reports, LED manufacturing is expected to grow significantly. “LED and solid state 

lighting (SSL) are two markets in the spotlight that attract a lot of attention and new investments. Driven mostly by the 

surge of LED-backlight demand for LCD TV panels and the huge potential market in general lighting, demand for LED is 

set to explode in the coming years. In view of supply tightness and market potential, new facility and capacity addition 

plans have suddenly emerged all over the world in the past year.” (Tsang, Clark, 2010). Therefore production processes 

used to manufacture LEDs are covered under the electronics manufacturing source category as one specific type of 

semiconductor device. 

Table 2-2. Rule Applicability under the Proposed Emissions-Based Thresholds 

Emissions Covered Facilities Covered 

Emissions 

Source Threshold 

Total 

National 

Facilities 

Total 

Emissions of 

Source (metric 

tons CO2e) 

metric tons 

CO2e/yr Percent Facilities Percent 

Semiconductors 25,000 Mt CO2e. 175 5,741,676 5,492,066 96% 91 52% 

MEMS 25,000 Mt CO2e 12 146,115 96,164 66% 2 17% 

LCD 25,000 Mt CO2e 9 23,632 0 0% 0 0% 

PV 25,000 Mt CO2e. 20 73,039 34,340 47% 1 5% 

2.2 Emissions-Based Threshold Calculations 

Emissions-based threshold estimations for each electronics manufacturing sector were derived in the following ways: 

Semiconductors emissions-based threshold estimations were derived using outputs from the EPA PFC Emissions Vintaging 

Model (PEVM), as well as EPA PFC Reduction/Climate Partnership for Semiconductors partner and non-partner shares of 

U.S. emissions. Additionally, the semiconductor emissions threshold estimations determined accounted for heat transfer 

fluid emissions by assuming that these emissions were equivalent to 11 percent of total clean and etch emissions at a 

facility. 

MEMS emissions-based threshold estimations were derived using an emission factor developed by EPA. EPA estimated an 

emission factor because no IPCC Tier 1 default emission factor exists. Assuming that MEMS are manufactured using the 

Bosch etching process, the utilization of SF6 in the production of MEMS was assumed to be the same as the utilization of 

SF6 in the etching of semiconductors due to the similarity between both of the manufacturing processes.9 However, 

because SF6 is used in only about 20 percent of semiconductor processes, the majority of which are etching processes, and 

 

9 Although the Bosch etching process uses both SF6 and C4F8, C4F8 was not included because it has a high utilization rate (i.e., a high 

fraction of C4F8 is dissociated during the etching or cleaning process). 
Subpart I Technical Support Document 

November 2010 5

it is assumed in this analysis that SF6 is used in all MEMS processes, the 2006 IPCC Tier 1 SF6 semiconductor emission 

factor (per area of substrate) was multiplied by five to estimate the MEMS emission factor per area of substrate. 

Additionally, the MEMS emission factor was scaled up by an additional factor of 1.2 to account for increased SF6 usage in 

MEMS manufacturing as compared to semiconductor manufacturing . 

LCD and PV emissions-based threshold estimations were derived using 2006 IPCC Tier 1 emission factors. 

Emissions reductions from the use of abatement systems were not accounted for in the any of the threshold analyses. 

2.3 Reporter Threshold Applicability Determinations 

Presented below are the methods reporters are required to use to determine whether their electronics manufacturing 

facility(ies) meets or exceeds the threshold of 25,000 metric tons CO2e. 

Facilities that Manufacture Semiconductor and LCD: To determine whether a facility that manufactures semiconductors 

(including LEDs) or LCDs meets the threshold, the facility would use the IPCC Tier 1 approach and IPCC Tier 1 emission 

factors. To account for heat transfer fluid use at semiconductor facilities, a facility would add an additional 10 percent of

their clean and etch emissions to their total facility emissions.10 

Facilities that Manufacture MEMS: To determine whether a facility that manufactures MEMS meets the threshold, the 

facility would use the IPCC Tier 1 approach and the EPA estimated emission factor for MEMS. 

Facilities that Manufacture PV: To determine whether a facility that manufactures PV meets the threshold, the facility 

would multiply annual fluorinated GHG purchases or consumption by the gas-appropriate 100-year GWPs (as defined in 

Table A-1 to subpart A of part 98). This method for PV facilities is expected to provide a more representative estimate of 

emissions than the IPCC Tier 1 approach and emission factors. IPCC Tier 1 factors for PV are highly uncertain because 

they were developed based on analogy to the IPCC Tier 1 factors for LCD due to limited PV data availability. 

Calculations to determine threshold applicability are presented below. Note that the equations below are to be used only for 

determining whether an electronics manufacturing facility falls above or below the threshold of 25,000 metric tons CO2e. 

For calculating emissions of each fluorinated GHG i, for facilities that manufacture semiconductors or MEMS: 

Ei = S *EFi*GWPi*0.001 (Eq. 1) 

Where: 

Ei = Annual production process emissions of input gas i (metric tons CO2e). 

S = 100% of annual manufacturing capacity of a facility (m2

). (see Eq. 5) 

EFi = Emission factor for input gas i (kg/m2

) (see Appendix A). 

GWPi = Gas-appropriate GWP (see Table A-1 to subpart A, Global Warming 

 Potentials). 

0.001 = Conversion factor from kg to metric tons. 

i = Input gas. 

For calculating emissions of each fluorinated GHG i, for facilities that manufacture LCDs: 

 

10 For simplicity, semiconductor facilities would estimate HTF emissions as 10% of total clean and etch emissions, as 

opposed to 11% which was used in our threshold analyses as presented above. 
Subpart I Technical Support Document 

November 2010 6

Ei = S *EFi*GWPi*0.000001 (Eq. 2) 

Where: 

Ei = Annual production process emissions of input gas i (metric tons CO2e). 

S = 100% of annual manufacturing capacity of a facility (m2

). (see Eq. 5) 

EFi = Emission factor for input gas i (g/m2

) (see Appendix A). 

GWPi = Gas-appropriate GWP (see Table A-1 to subpart A, Global Warming 

 Potentials). 

0.000001 = Conversion factor from g to metric tons. 

i = Input gas. 

For calculating emissions of each fluorinated GHG i, for facilities that manufacture PVs: 

Ei = Ci*GWPi* 0.001 (Eq. 3) 

Where: 

Ei = Annual production process emissions of input gas i (metric tons CO2e). 

Ci = Annual fluorinated GHG (gas i) purchases or consumption (kg). 

GWPi = Gas-appropriate GWP (see Table A-1 to subpart A, Global Warming 

 Potentials). 

0.001 = Conversion factor from kg to metric tons. 

i = Input gas. 

To sum emissions of all input gases i for all facilities: 

= ∑

i

ET δ * Ei (Eq. 4) 

Where: 

ET = Annual production process emissions of all fluorinated GHGs (metric tons CO2e). 

δ = Factor accounting for heat transfer fluid emissions, estimated as 10 percent of total annual production 

process emissions at a semiconductor facility. Set equal to 1.1 when calculating total annual production 

process emissions from semiconductor manufacturing. Set equal to 1 calculating total annual production 

process emissions from MEMS, LCD, or PV manufacturing. 

Ei = Annual production process emissions of input gas i (metric tons CO2e), as calculated Eqs. 1, 2, or 3. 

i = Input gas. 

For calculating a facility’s annual manufacturing capacity: 

To determine 100 percent of annual manufacturing capacity, facilities would sum the maximum designed substrate starts of 

a facility over each month of a year as presented in Equation 5 below. Maximum designed substrate starts is defined as the 

maximum quantity of substrates, expressed as surface area, that could be started each month during a reporting year if the 

facility were fully equipped as defined in the facility design specifications and if the equipment were fully utilized. It 

denotes 100 percent of annual manufacturing capacity of a facility. 
Subpart I Technical Support Document 

November 2010 7

= ∑

12

S xWx (Eq. 5) 

Where: 

S = 100 percent of annual manufacturing capacity of a facility (m2

). 

Wx = Maximum designed substrate starts of a facility in month x (m2 per month). 

x = Month. 

None of the methods for determining threshold applicability account for controlled emissions by abatement systems. EPA 

is not permitting accounting for emissions reductions from abatement systems because while electronics manufacturers may 

employ emissions abatement systems (e.g., thermal oxidizers) to lower their emissions and use the manufacturer published 

destruction or removal efficiency (DRE) for the system, abatement systems may fail to achieve their rated DREs for two 

reasons. First, the equipment may not be properly operated and maintained. Second, the DRE itself may have been 

incorrectly measured due to a failure to account for the effects of dilution (e.g., CF4 can be off by as much as a factor of 20 

to 50 and C2F6 can be off by a factor of up to 10 because of failure to properly account for dilution [Burton, 2007].) In 

either event, the actual emissions from facilities employing abatement systems may exceed estimates based on the rated 

DREs of the systems and may therefore exceed the MtCO2e threshold without the knowledge of the facility operators. 

Hence, accounting for reductions in emissions from the use of abatement systems when determining if a facility exceeds the 

proposed 25,000 metric ton CO2e threshold limit is not permitted because the DRE used in such a calculation cannot be 

verified. 

3 Options for Emissions Calculation and Monitoring Methods 

EPA evaluated a range of options for estimating process emissions from productions processes used in electronics 

manufacturing. Each one of these options is briefly described below. 

3.1 Options for Estimating Fluorinated GHG Emissions from Etching and Cleaning 

To estimate and report fluorinated GHGs from etching and cleaning, EPA evaluated the 2006 IPCC Tier 1, Tier 2a, Tier 2b, 

and Tier 3 methods, as well as hybrids, refinements of, and modifications to those methods.11 Lastly, EPA evaluated the 

use of continuous monitoring emissions systems (CEMS). 

Many of the options described below, including the IPCC Tier 2b, Modified Tier 2b, Refined Method, Tier 2c, Tier 2d, and 

the IPCC Tier 3 methods use the typology presented in Figure 3-1 below. At the top of the typology figure are process 

types, which are broad groups of manufacturing steps used at a facility associated with substrate (e.g., wafer) processing 

during device manufacture for which fluorinated GHG emissions and fluorinated GHG usages are calculated and reported. 

The process types are plasma etching, chamber cleaning, and wafer cleaning. Process types for various methods include 

etching and chamber cleaning, and for some methods, wafer cleaning. 

The second level in the figure consists of process sub-types. Process sub-types are sets of similar manufacturing steps, more 

closely related within a broad process type. (Note, for clarity, EPA is referring to what was previously termed process 

categories in the April 2010 proposed rule (75 FR 18652) as process sub-types). Figure 3-1 only identifies process subtypes for the chamber cleaning process type, however in an option described below (mainly the Refined Method) process 

sub-types could be established for any process type. For example, under the plasma etching process type either film-based 

(e.g., oxide etch, nitride etch) or feature-based (e.g., gate etch, deep trench etch) process sub-types could be established; 

under the wafer cleaning process type, the sub-types of ashing and bevel cleaning could be established. At the lowest level 

of the typology tree in Figure 3-1 are production process recipes (“recipes”). The recipe typology is discussed further in 

section 3.1.7.1 below. 

 

11 It is important to note that the IPCC methods were developed to estimate national averages of emissions for specific sources (e.g. 

national emissions from semiconductor manufacturing) and not for facility-specific emissions. 
Subpart I Technical Support Document 

November 2010 8

Figure 3-1. Typology for Calculating Fluorinated GHG Emissions from Electronics Manufacturing 

For some of the methods for estimating emissions from etching and cleaning discussed below, a distinction is made for 

facilities that manufacture semiconductors (see Tier 2c, Tier 2d, and Hybrid Approaches). Semiconductor manufacturing 

facilities would select the appropriate etch and clean emission estimation methods based upon facility size expressed in 

terms of annual manufacturing capacity. 

The largest semiconductor manufacturing facilities are defined as those with a capacity of greater than 10,500 m2

 of 

substrate (e.g., silicon), as calculated using Equation 5 above. The largest semiconductor manufacturing facilities account 

for nearly two-thirds of uncontrolled emissions from semiconductor manufacturing while accounting for less than 20 

percent of all semiconductor facilities expected to report under subpart I. Applying this distinction, EPA expects that 29 of 

the estimated 175 semiconductor facilities will be classified as “large” facilities. These results were based on the analysis 

illustrated in Figure 3-2 below.12 

Figure 3-2. Expected Facility Contributions to Total Emissions from Semiconductor Manufacturing 

3.1.1 2006 IPCC Tier 1 Method 

For the Tier 1 approach, the surface area of substrate (e.g., silicon, LCD or PV-cell) produced during electronics 

manufacture is multiplied by default gas-specific emission factors. The advantages of the Tier 1 approach lie in its 

 

12 See footnote 8. 
Subpart I Technical Support Document 

November 2010 9

simplicity. However, this method does not account for the differences among process types (i.e., etching versus cleaning), 

individual processes, recipes, or tools, which leads to uncertainties in the default emission factors of up to 200 percent at 

the 95 percent confidence interval (IPCC, 2006).13 Moreover, facilities routinely monitor gas consumption in the ordinary 

course of business, making it technically feasible to employ a method with the complexity of at least the 2006 IPCC Tier 2a 

approach without additional data collection efforts. 

3.1.2 2006 IPCC Tier 2a Method 

For the Tier 2a approach, chemical-specific gas consumption is multiplied by default emission factors for utilization, and 

by-product formation. The Tier 2a approach is relatively simple, given that gas consumption data is collected in the 

ordinary course of business. However, due to variation in gas utilization between etching and cleaning processes, the 

emissions estimated using the Tier 2a approach have greater uncertainty than emissions estimated using the Tier 2b 

approach. 

3.1.3 2006 IPCC Tier 2b Method 

For the Tier 2b approach, chemical-specific gas consumption by process type (etch or chamber clean) is multiplied by 

default emission factors for utilization and by-product formation.14 This approach requires facilities to determine gas 

consumption by process type (etch and clean). Equation 6 below is used to estimate fluorinated GHG emissions for process 

type (j) for input gas (i), and Equation 7 below is used to estimate byproduct gas (k) that results from input gas (i) 

utilization during process type (j).15

Eij = Cij*(1− Uij) *(1− aij*dij)*0.001 (Eq. 6)

Where: 

Eij = Annual emissions of input gas i from process type j (metric tons). 

Cij = Amount of input gas i consumed for process type j (kg). (see Eq. 8) 

Uij = Process utilization for input gas i for process type j (decimal fraction). 

aij = Fraction of input gas i used in process type j with abatement systems (decimal fraction). 

dij = Fraction of input gas i destroyed or removed in abatement systems connected to process tools 

where process type j is used (decimal fraction). (see Eq. 13) 

0.001 = Conversion factor from kg to metric tons. 

i = Input gas. 

j = Process type. 

BEijk = Bijk*Cij* (1− aij* d jk ) * 0.001 (Eq. 7)

Where: 

BEijk = Annual emissions of by-product k formed from input gas i from process type j (metric tons). 

Bijk = Amount of gas k created as a by-product per kg of input gas i consumed for process type j (kg). 

Cij = Amount of input gas i consumed for process type j (kg). (see Eq. 8) 

 

13 This uncertainty refers only to semiconductors and LCDs. Tier 1 emission factor uncertainty for PV was not estimated in the IPCC 

Guidelines (IPCC, 2006). Additionally, emissions from MEMS are not addressed in the 2006 IPCC Guidelines.

14 For all methods based on default emission factors specified in the final rule (e.g., the Tier 2b, Tier 2c, and Tier 2d methods), a facility 

must use the default factors provided by EPA; the only exception is if a facility uses a fluorinated GHG for a particular process type or 

sub-type for which default emission factors are not provided. Where defaults are not provided, the facility must either use utilization and 

by-product formation rates of 0 or, in that particular instance, use directly measured recipe-specific emission factors following the 

methods outlined in section 3.1.7.1. 

15 Note the 2006 IPCC Guidance for National Greenhouse Gas Inventories equations for estimating emissions and by-product emissions 

in the electronics industry (Equations 6.7 through 6.11) include a term for the heel of gas cylinders/containers. However, the heel term 

has been excluded in Equations 6 and 7 because it is already accounted for when overall gas consumption is estimated (shown in 

Equations 8 and 9). 
Subpart I Technical Support Document 

November 2010 10

aij = Fraction of input gas i used in process type j with abatement systems. 

djk = Fraction of input gas i destroyed in abatement systems connected to process tools where process 

type j is used (decimal fraction). (see Eq. 13) 

0.001 = Conversion factor from kg to metric tons. 

i = Input gas. 

j = Process type. 

k = By-product gas. 

Although the uncertainty relative to Tier 2a is reduced, the Tier 2b approach also does not account for variation among 

individual recipes, processes or tools and, therefore, the estimated emissions will have greater uncertainty compared to Tier 

3 emissions estimates. The Tier 2b method, as shown in the uncertainty analysis performed by EPA, may understate actual 

emissions. (see Appendix C) 

3.1.4 Modified Tier 2b Method 

The Modified IPCC Tier 2b approach is based on the 2006 IPCC Tier 2b method (as described above). However, the 

Modified Tier 2b approach takes into account gas- and facility- specific heel factors, as opposed to utilizing a default value 

for heel factor as suggested in the IPCC Guidelines. Emission estimations using the Modified IPCC Tier 2b approach are 

assumed to be less uncertain than estimations determined using the 2006 IPCC Tier 2b method. This is because when using 

a default heel factor, gas consumption is likely to be less representative of actual gas consumption, and hence emissions, in 

comparison to using gas- and facility- specific heel factors. (see section 3.2 for more discussion on the use of default versus

gas- and facility- specific heel factors)

3.1.5 Tier 2c Method (Defaults for 5 Process Types/Subtypes) 

The Tier 2c Method expands on the Modified Tier 2b method for facilities that manufacture semiconductors. In the Tier 2c 

method, emissions would be estimated for five process type/subtypes: plasma etching, chamber cleaning (including in-situ 

plasma, remote plasma, and in-situ thermal), and wafer cleaning. For the Tier 2c Method, gas consumption apportioned to 

process types or sub-types is multiplied by default emission factors for utilization and by-product formation, (dependent on 

the size of wafer manufactured at a facility)16, using Equations 6 and 7, respectively.17 EPA considered the Tier 2c method 

for facilities that manufacture semiconductor facilities and that have annual manufacturing capacities of 10,500 m2 or less 

(ass calculated using Equation 5).18 Because the Tier 2c method is more granular than the IPCC and Modified Tier 2b 

methods,19 EPA anticipates that its use will result in more accurate emission estimates. 

3.1.6 The Refined Method (Defaults Factors for 9 Process Types/Subtypes) 

The Refined Method, which was evaluated as part of the April 2010 proposal, expands on the two process types (etch and 

clean) of the IPCC Tier 2b method by requiring that emissions be estimated from the etch, chamber clean and wafer clean 

process types by summing emissions from various process sub-types For the Refined Method, gas consumption 

apportioned by process sub-type is multiplied by default emission factors for utilization and by-product formation20, using 

Equations 6 and 7, respectively.21 

While process sub-types can be defined in many ways, the Refined Method utilizes nine process sub-types which include 

four sub-types for etching, three sub-types for chamber cleaning, and two sub-types for wafer cleaning. The etching 

categories include oxide etch, nitride etch, silicon etch, and metal etch; the chamber cleaning categories include in situ 

 

16 See Appendix A for the default factors, and Appendix B for background on how the default factors were developed. 

17 When using Equations 6 and 7 for the Tier 2c method “j” indexes process sub-types or process types. 

18 The Tier 2c method was finalized as part of the final rule, and all semiconductor facilities with annual manufacturing capacities of 

10,500 m2

 substrate of less are required to calculate and report process emissions using this method. See the preamble for a discussion

why EPA selected this method. 

19 For the Tier 2c method emissions must be estimated for three chamber cleaning process sub-types as opposed to just the broad 

chamber cleaning process type used in the Tier 2b methods. 

20 EPA did not finalize default emission factors for the etch subtypes presented in the Refined Method. 

21 When using Equations 6 and 7 for the Refined Method “j” indexes process sub-types as opposed to process types. 
Subpart I Technical Support Document 

November 2010 11

plasma cleaning, remote plasma cleaning, and in situ thermal cleaning; and the wafer cleaning categories include bevel 

cleaning and ashing. 

For the Refined Method EPA considered additional potential process sub-types for etching and chamber cleaning to replace 

or complement the process sub-types defined above. For etching, in addition to the four thin-film based sub-types defined 

above, EPA considered the use of the feature-based sub-types contact etch, self-alignment contact etch, gate etch, deep 

trench etch, isolation trench etch, through silicon vias and regular vias. Each of these represents a specific feature achieved 

through etching (instead of subcategories based on the type of thin film etched). For chamber clean, alternative sub-types 

may distinguish between the types of films being removed from the chamber during cleaning. These might include 

distinguishing between chambers coated with tungsten and silicon-based films, or distinguishing between thin-film 

deposition equipment manufacturers. 

There are no published emission factors for the refined process categories as defined in the Refined Method, therefore to 

obtain emission factors (i.e., utilization and by-product formation rates) for each process category, EPA undertook a 

process to collect data from industry, and evaluated its robustness and usefulness for creating emission factors through an 

averaging scheme, either simple or weighted depending on information received. This process is further discussed in the 

TECHNICAL SUPPORT DOCUMENT (UPDATED) FOR PROCESS EMISSIONS FROM ELECTRONICS 

MANUFACTURE (e.g., SEMICONDUCTORS, LIQUID CRYSTAL DISPLAYS, PHOTOVOLTAICS, AND MICROELECTRO-MECHANICAL SYSTEMS): PROPOSED RULE FOR MANDATORY REPORTING OF GREENHOUSE 

GASES (March 22, 2010) and the Subpart I Notice of Data Availability (75 FR 26904).22 EPA obtained a sufficient 

amount of information to establish default emissions factors for multiple chamber clean process sub-types, but there was an 

insufficient amount of information to support establishing default emission factors for multiple etch process sub-types. 

Therefore the Refined Method was not adopted for the final rule.23 

EPA considered the Refined Method for semiconductor facilities only, as semiconductor manufacturing is understood to be 

more variable and complex than other electronics manufacturing. The goal in establishing process sub-types under each 

process type is to account for variability in emission factors across processes to reduce uncertainty in emission estimates, 

while limiting the total number of process sub-types for which gas usage must be tracked. EPA expects that estimating 

emissions based on process sub-types for etch with robust default factors would result in more accurate facility-level 

emission estimates as compared to estimating emissions using a single broad etch process type as presented in the IPCC 

and Modified Tier 2b methods. 

3.1.7 Tier 2d Method (Defaults for 4 Process Types/Subtypes, Recipe-specific emission factors 

for 1 Process Type) 

For the Tier 2d method, 24 which uses the same process types/sub-types as the Tier 2c method, gas consumption is 

apportioned to the chamber cleaning process sub-types (including in-situ plasma, remote plasma, and in-situ thermal) and 

the wafer cleaning process type and is multiplied by various default emission factors for utilization and by-product 

formation, (dependent on the size of wafer manufactured at a facility, see Appendix A), using Equations 6 and 7, 

respectively.25 However, for the plasma etching process type, emissions are estimated by apportioning gas consumption to 

etch recipes, each with directly measured recipe-specific emissions factors for utilization and by-product formation. Based 

on an uncertainty analysis conducted by EPA, the Tier 2d method appears to be more precise than the Tier 2c method (see 

Appendix C). EPA evaluated the Tier 2d method for the largest semiconductor manufacturing facilities because, as 

discussed above, the largest facilities are expected to account for nearly 2/3 of all potential emissions, while accounting for

less than 20 percent of all covered semiconductor facilities.26 

The Tier 2d method is focused on recipe-specific emission factors for etching processes because of the apparent gaps in the 

available emission factor knowledge base for etching processes used in the industry. While more than half of the gas 

consumed in semiconductor manufacturing is for chamber cleaning, most of the variability in gas consumption, and hence 

 

22 Both documents are available in the docket at EPA-HQ-OAR-2009-0927. 

23 Please see the preamble for more discussion on the reasons why the Refined Method was not finalized. 

24 The Tier 2d method was finalized as part of the final rule, and all large semiconductor facilities (semiconductor facilities with annual 

manufacturing capacities greater than 10,500 m2

 substrate) are required to calculate and report process emissions using this method. See 

the preamble for a discussion why EPA selected this method. 

25 When using Equations 6 and 7 for the Tier 2d method “j” indexes recipes, process sub-types, or process types. 

26 See the preamble for further discussion of EPA’s considerations for the Tier 2d method and steps taken to reduce burden. 
Subpart I Technical Support Document 

November 2010 12

emissions, across many facilities is found for recipes used for etching. Semiconductor etch recipes utilize approximately 

six or more fluorinated GHGs, either alone or in combination and in various mixtures. Process recipes may vary between 

facilities because they are considered a function of company competitiveness and innovation. 

3.1.7.1 Development of Recipe-Specific Emission Factors 

Recipe-specific emission factors would be developed for each individual recipe, or for a set of similar recipes. An 

individual recipe refers a specific combination of gases, under specific conditions of reactor temperature, pressure, flow, 

radio frequency (RF) power and duration, used repeatedly to fabricate a specific feature on a specific film or substrate. 

Recipe-specific emissions factors developed for measurements already made for an individual recipe may be applied to a 

set of similar recipes, where similar, with respect to recipes means those recipes that are composed of the same set of 

chemicals and have the same flow stabilization times and where the documented differences, considered separately, in 

reactor pressure, individual gas flow rates, and applied radio frequency (RF) power are less than or equal to plus or minus 

10 percent. For purposes of comparing and documenting recipes that are similar, facilities may use either the best known 

method provided by an equipment manufacturer or the process of record, for which emission factors for either have been 

measured. (Technical support for the definition of similar recipes can be found in Appendix D) 

This definition of similar recipe applies to in-situ and RPS chamber cleaning as well as etching. It applies to in-situ 

chamber cleaning by virtue of the representative in situ chamber cleaning studies reviewed in Appendix D, which show that 

for changes in individual recipe variables of 10 percent or less results in corresponding changes in emissions of less than 10 

percent. The recipes considered in Appendix D used NF3, C2F6 and C3F8. The definition remains valid for contemporary 

RPS chamber cleaning recipes. As shown by Chen et. Al (2003), NF3 utilization, which together with duration of cleaning 

time governs emissions during NF3-based RPS chamber cleaning, is relatively insensitive to changes in flow rate (over the 

wide range 2 to 6 lpm) and pressure (over the relatively wide range of 3 to 10 torr). Over these ranges, Chen et. al (2003) 

report NF3 utilization efficiencies at 99 percent or above. 

In a given reporting year, a facility must develop new recipe-specific emission factors only for recipes that are not similar to 

any recipe used in a previous reporting year. Three examples of how a facility may develop (or obtain) recipe-specific 

emission factors are presented below: 

1. Make direct measurements on-site at the facility. 

2. Obtain measurement information, and hence emission factors, from tests performed by a third-party, such as a tool 

supplier. (Any measurements made by a third-party are required to have been made for recipes that are similar 

recipes (as defined above) to those used at the facility. 

3. Use factors from another facility that uses similar recipes. (For example, there are instances where a company 

operating multiple facilities will use the same or similar recipes in more than one facility; in this instance, 

measured recipe-specific emission factors for a recipe used at one facility may also be used for estimating 

emissions from the use of a similar recipe at another facility.) 

All recipe-specific emission factors must be measured using the International SEMATECH Technology Transfer 

(#06124825A-ENG) (December 2006). A facility may use recipe-specific emission factors that were developed prior to 

January 1, 2007, provided they were measured using the International SEMATECH Technology Transfer (#01104197AXFR) (December 2001). 

3.1.8 2006 IPCC Tier 3 Method 

The Tier 3 method uses the same equations as the IPCC Tier 2b, Refined Method, Tier 2c and Tier 2d approaches 

(Equations 6 and 7)27, but requires facility-specific data on (1) gas consumption, (2) gas utilization, (3) by-product 

formation, rather than applying any default values. The 2006 IPCC Guidelines state that for the Tier 3 method, plantspecific values should be used for each individual process or for each small sets of processes. There may be various ways 

processes or sets of processes could be defined, for instance by process platforms, processes or recipes. The Tier 3 method 

in the context of this rule uses gas consumption to be apportioned to recipes, multiplied by requires facility-specific, recipespecific emission factors for utilization and by-production formation, developed for each individual recipe or set of similar 

 

27 When using Equations 6 and 7 for the IPCC Tier 3 approach “j” indexes recipes as opposed to process types. 
Subpart I Technical Support Document 

November 2010 13

recipes as discussed above in section 3.1.7.1. The use of the Tier 3 method is estimated to result in the least uncertain 

estimates amongst the methods presented by IPCC (IPCC 2006). 

3.1.9 Hybrid Approach A 

Hybrid Approach A, which was evaluated as part of the April 2009 proposal, requires the largest semiconductor facilities 

(facilities with production capacities of greater than 10,500 m2

 silicon) to estimate their etching and cleaning emissions 

using an approach based on the IPCC Tier 3 method; all other facilities (including other semiconductor manufacturing and 

other electronics manufacturing facilities) would be required to use the IPCC Tier 2b method. 

3.1.10 Hybrid Approach B 

Hybrid Approach B, which was evaluated as part of the April 2009 proposal, requires Tier 3 reporting for all semiconductor 

facilities, but only for the top three gases emitted at each facility. For all other gases, the Tier 2b approach is required. The 

top three gases emitted, based on data in the Inventory of U.S. GHG Emissions and Sinks, are C2F6, CF4, and SF6 (EPA, 

2008a). These top three gases accounted for approximately 80 percent of total fluorinated GHG emissions from 

semiconductor manufacturing during etching and chamber cleaning in 2006. 

3.1.11 Continuous Emissions Monitoring Systems (CEMS) 

CEMS requires facilities to install and operate CEMS to measure process emissions. A typical electronics manufacturing 

facility may have many individual process tools that influence emissions. Process tool exhaust is managed within the 

facility using stainless steel plumbing and ductwork. Due to the complexity of the manufacturing layout, CEMS would 

either need to be attached to every tool or to a final exhaust point (e.g., scrubber stacks). One possible option is to use 

Fourier Transform Infrared Spectrometers (FTIRs) in scrubber stacks to measure facility emissions. FTIR spectroscopy is 

presently used to conduct short-term fluorinated GHG emission measurements on single tools. Another option would be to 

either continuously or intermittently bring a gas sample to one or more centrally located FTIRs, in which case any dilution 

issues that may arise when measuring fluorinated GHGs in stacks may be avoided. 

3.2 Options for Estimating Facility Gas Consumption 

Several of the estimation methods described above require gas consumption to be used to estimate emissions. Equations 8 

and 9 below are used to estimate gas consumption for any input gas i used at an electronics manufacturing facility. 

Ci = (IBi – IEi + Ai – Di) (Eq. 8) 

Where: 

Ci = Annual consumption of input gas i (kg). 

IBi = Inventory of input gas i stored in containers at the beginning of the reporting year, including heels 

(kg).28

IEi = Inventory of input gas i stored in cylinders or other containers at the end of the reporting year, 

including heels (kg).29 

Ai = Acquisitions of input gas i during the reporting year through purchases or other transactions, including 

heels in containers returned to the electronics manufacturing facility (kg). 

Di = Disbursements of input gas i through sales or other transactions during the year, including heels in 

containers returned by the electronics manufacturing facility to the chemical supplier (kg). (see Eq. 9) 

i = Input gas.

 

28 For containers in service at the beginning of a reporting year, account for the quantity in these containers as if they were full. 

29 For containers in service at the end of a reporting year, account for the quantity in these containers as if they were full. 
Subpart I Technical Support Document 

November 2010 14

( ) i

M

l

Di = ∑ hil Nil Fil + X =1* * (Eq. 9)

Where: 

Di = Disbursements of input gas i through sales or other transactions during the reporting year, including 

heels in containers returned by the electronics manufacturing facility to the gas distributor (kg). 

hil = Facility-wide gas-specific heel factor for input gas i and container size and type l (expressed as a 

decimal fraction), as determined in §98.94(b).30 

Nil = Number of containers of size and type l returned to the gas distributor containing the standard heel of 

input gas i. 

Fil = Full capacity of containers of size and type l containing input gas i (kg). 

Xi = Disbursements under exceptional circumstances of input gas i through sales or other transactions during 

the reporting year, including those measured in exceptional circumstances (kg). 

i = Input gas. 

l = Size and type of gas container. 

M = The total number of different sized container types. If only one size and container type is used for an 

input gas i, M=1. 

For the heel factor31 (hil) used in Equation 9, EPA evaluated two options including the IPCC default heel factor and gas-and 

facility-specific heel factors. Both of these options are described below. 

3.2.1 IPCC Default Heel Factor 

The IPCC default value for the fraction of gas remaining in the shipping container (i.e. the “heel”) is 10 percent (IPCC, 

2006). This value is intended to be applicable to all gas containers, regardless of the gas type or container size or shape. 

However, heels may vary among gases and container sizes and shapes. Differences in gas usage practices may also exist 

between facilities which would not be accounted for when using the IPCC default heel factor. Therefore, the use of the 

IPCC default heel factor may result in misestimating gas consumption and emissions. 

3.2.2 Gas-and Facility-Specific Heel Factors 

Facility-specific heel factors for each gas and container type and size are based on the residual weight or pressure of the gas

container, or trigger point for change out, that a facility uses to change out that container for each container type for each 

gas used. By using these trigger points, along with the initial mass of the container, gas-and facility-specific heel factors 

can be calculated.32 

To account for exceptional circumstances33 when gas containers are not changed precisely when they reach the targeted 

trigger points, EPA evaluated the option of requiring reporters to weigh or determine the pressure of the gas container as 

opposed to using the facility-wide gas-specific heel factor as part of determining the net amount of gas used at a facility. To

account for changes in gas consumption practices, EPA considered two situations in which facility-wide gas-specific heel 

 

30 If a facility uses less than 50 kg of a fluorinated GHG or N2O in one reporting year, the facility may assume that any hil for that 

fluorinated GHG or N2O is equal to zero. 

31 Heel is defined as the amount of gas that remains in a gas cylinder or container after it is discharged or off-loaded. 

32 The initial mass of a container may be determined through gas supplier documents; however the reporter remains responsible for the 

accuracy of these records. 

33 EPA is requiring an exceptional circumstance be defined as one in which a cylinder/container is changed at a residual mass or pressure 

that differs by more than 20 percent from the “trigger point for change out.” When using mass based trigger points for change, it should 

be determined if exceptional circumstances have occurred based on the net weight of gas in containers, excluding the tare weight of the 

container. 
Subpart I Technical Support Document 

November 2010 15

factors would have to be recalculated; both when the trigger point for change out used to establish a heel factor for a gas 

and container type differs by more than one percent or five percent from the previously used trigger point for change out. 

The use of a gas-and facility-specific heel factor is expected to produce more accurate estimates of gas consumption in 

comparison to the use of the IPCC default value of 10 percent. This is because the amount of gas that remains in a gas 

container after it is discharged or off-loaded is not the same for every gas and container type, and the default value does not

account for exceptional circumstances or variations in gas consumption practices within or between facilities. Therefore 

applying a broad default value to every gas container will lead to estimations that may not be representative of actual 

facility gas consumption, and hence facility emissions. 

3.3 Option for Apportioning Gas Consumption 

When estimating emissions using methods such as the Modified IPCC Tier 2b or the Tier 2c or Tier 2d methods, and a 

fluorinated GHG is used in more than one process type or sub-type (e.g., C2F6 used for both etch and clean processes), 

facility-wide gas consumption must be apportioned to the appropriate process types, process sub-types, or recipes through 

the use of Equation 10. The product of that apportioned gas usage and the corresponding emission factor (either default or 

recipe-specific) will equate to a facility’s uncontrolled emissions for a specific process type, process sub-type, or recipe . 

These emissions can be summed within and over all process types and categories at a facility to determine total facilitywide uncontrolled emissions. 

Cij= fij * Ci (Eq. 10) 

Where: 

Cij = Annual amount of input gas i consumed for recipe, process subtype, or process type j (kg). 

fij = Recipe-specific, process sub-type-specific, or process type-specific gas apportioning factor (decimal 

fraction).34

Ci = Annual consumption of input gas i (kg). (see Eq. 8) 

i = Input gas. 

j = Recipe, process sub-type or process type. 

Apportioning factors (fij) used in Equation 10, would be developed using facility-specific engineering models based on a 

quantifiable metric selected by a facility (such as wafer passes or wafer starts).35 This model, utilizing measurable process 

information, may be based on the most appropriate quantifiable metric for each facility. Such a model utilizes facility 

process information to determine apportioning factors using the ratio of the amount of input gas i used per recipe (process 

category, process type) multiplied by the number of times that recipe is used on a tool and the number of tools that recipe is 

used on over the total amount of gas i used. 

Given that facilities may select how to construct, and on which quantifiable metric to base facility-specific engineering 

models for gas apportioning, EPA considered various documentation and verification steps for facilities to take. 

Documentation

As part of recordkeeping requirements, in site GHG Monitoring Plans (required in §98.3(g)(5)), specific information about 

their facility-specific engineering model, including definitions of variables, derivations of equations and formulas, and 

example calculations to ensure apportioning factors are repeatable36 would be documented and updated annually. This 

 

34 See Section 3.3 discussion on apportioning. 

35 Wafer passes is a count of the number of times a wafer substrate is processed in a specific process recipe, sub-type, or type. The total 

number of wafer passes over a reporting year is the number of wafer passes per tool multiplied by the number of operational process tools 

in use during the reporting year. Wafer starts means the number of fresh wafers that are introduced into the fabrication sequence each 

month. It includes test wafers, which means wafers that are exposed to all of the conditions of process characterization, including but not 

limited to actual etch conditions or actual film deposition conditions. 

36 Repeatable means that the variables used in the formulas for the facility’s engineering model for gas apportioning factors are based on 

observable and measurable quantities that govern gas consumption rather than engineering judgment about those quantities or gas

consumption. 
Subpart I Technical Support Document 

November 2010 16

information would be updated each year for each facility to account for changes to tools or process at a facility between 

reporting years. 

Verification

To verify engineering models used to apportion gas consumption, EPA requires facilities to demonstrate that the results 

from the model are repeatable and to compare the difference between modeled gas usage and actual gas usage. Facilities 

would verify a facility-specific engineering model through the following: 

1. Analyzing at least a 30-day period of operation during which the capacity utilization of the facility equals or 

exceeds 60 percent of its design capacity.37 

2. Comparing the actual gas consumed of input gas i to the modeled gas consumed of input gas i for one fluorinated 

GHG used for the plasma etching process type and one fluorinated GHG used for the chamber cleaning process 

type. The fluorinated GHGs selected for comparison would be the ones used in the largest quantities, on a mass 

basis, for each of the identified process types. 

3. Ensuring that the comparison performed for the gas used in the largest quantity for the plasma etching process type 

does not result in a difference between the actual and modeled gas consumption that exceeds five percent relative 

to actual gas consumption, reported to one significant figure using standard rounding conventions. 

3.3.1 Example of Facility-Specific Engineering Model Based on Wafer Pass 

One example of a quantifiable metric on which a facility may base an engineering model to apportion gas consumption is 

wafer pass. During semiconductor device manufacturing, counts of wafer passes for each manufacturing step, over the 

course of a year, carry information about fab productivity and fluorinated GHG usage. The design and profitable operation 

of a modern fab entails detailed considerations of the functional performance of the equipment and its cost-of-ownership. 

Cost of ownership is governed in large part by its productivity—the number of wafers processed per hour, the time to 

maintain and time to failure. 

Fab managers use information about counts of wafer passes to reduce variable costs by identifying practices that increase 

fab throughput and that reduce material costs. Wafer pass counts in modern fabs are typically available through the 

manufacturing execution software (MES) that comes with process equipment. MES is capable of tracking the activities 

associated with each piece of manufacturing equipment. In older fabs that may not employ MES, wafer pass counts are 

available through process flow information for each product manufactured. 

While wafer-pass-count information is available, it is not routinely gathered. Instead, it’s gathered at the request of fab and

product line managers for purposes of managing work-in-process load, reducing fab cycle time, reducing product cycle 

time, identifying and removing process bottlenecks, etc. 

For estimating gas usage, wafer pass counts could be collected either electronically or physically. For those fabs with 

MES, wafer pass counts could be collected electronically, either continuously or intermittently. In those fabs without MES, 

wafer pass counts would be collected intermittently at periods chosen to be representative of manufacturing over the 

reporting period. 

The example following is a demonstration of the use of wafer pass in apportioning NF3 consumption at a hypothetical 

facility for the following three process sub-types defined by the Refined Method: oxide etch, silicon etch, and remote 

plasma clean. For simplicity and demonstration purposes, it is assumed that at the hypothetical facility NF3 is the gas used 

in the largest quantity, on a mass basis, for the plasma etching process type and the chamber cleaning process type. 

An illustrative case for a semiconductor facility that can be considered where wafer passes are the quantifiable metric of gas 

usage activity used, in a facility-specific engineering model, is a facility that uses NF3 for chamber cleaning with remote 

plasma systems and for etching polysilicon and oxide films. With knowledge of the NF3-specfic heel and the number of 

NF3 containers used, the facility knows the amount of NF3 consumed. To estimate emissions the facility must now 

apportion NF3 usage between the chamber cleaning, polysilicon etching, and oxide etching process sub-types. To do this it 

might use the total number of wafer passes through each and every NF3-cleaning system together with the time and nominal

(not measured actual) gas flow rate for each and every NF3-cleaning system and the corresponding figures for polysilicon 

 

37 If a facility operates below 60 percent of its design capacity during the reporting year, the period during which the facility experiences 

its highest 30-day average utilization would be used for model verification. 
Subpart I Technical Support Document 

November 2010 17

etch processes and oxide etch processes to arrive at the proportion of NF3 used for cleaning chambers and etching 

polysilicon and oxide films. Once developed, these apportioning factors could be used to estimate NF3 gas usage for the 

cleaning and etching process sub-types proposed in our method. This example is illustrated further in Table 3-1 below. 

Table 3-1. Illustrative Calculation for NF3 Example at One Facility 

Gas Type – Annual Usage, 

kg. 

Process Sub-type Apportioning Factor Process sub-type gas usage, 

kg. 

RPS Chamber 

Cleaning 

82% 46,202 

Polysilicon Etch 17% 9,561 

NF3 – 56,286 kg 

Oxide Etch 1% 523 

Note: Annual gas usage presented is the modeled usage not the nominal usage. 

For the example presented in Table 3-1, the annual nominal gas usage is 56,009 kg of NF3, with 520 kg of NF3 used for 

oxide etch, 9,514 kg of NF3 use for polysilicon etch, and 45,974 kg of NF3 used for RPS chamber clean. Using this 

information, as well as the modeled amount of gas consumed for each of the three process sub-types considered, an 

example verification is presented in below in Table 3-2. 

Table 3-2. Illustrative Verification for Hypothetical Facility-Specific Gas Apportioning Model 

Process Sub-Type Nominal Usage Modeled Usage 

Chamber Clean Process Type 

RPS 45,974 46,202 

Comparison 0.5% 

Etch Process Type 

Oxide etch process 520 523 

Silicon etch process 9,514 9,561 

Total 10,034 10,084 

Verification Comparison 0.5% 

While the manufacturing process for other electronics manufacturers are less complex as compared to semiconductor 

manufacturing as most gases are used for a single process type, facilities that manufacture LCDs, MEMS and PV may also 

use engineering models based on quantifiable metrics of manufacturing activity for apportioning gas consumption by 

process type. The approach of using a facility-specific model may also be applied to apportion consumption of N2O. 

3.4 Options for Estimating Nitrous Oxide (N2O) Emissions 

EPA evaluated two methods to estimate emissions of N2O during CVD or other N2O-using manufacturing processes, such 

as chamber cleaning, both of which would utilize Equation 11. The first option is the use of two facility-specific N2O 

utilization factors for each CVD and other N2O-using manufacturing processes. These factors would be developed by 

directly measuring N2O utilization at a facility using the 2006 ISMI Guidelines or the 2001 ISMI Guidelines, provided the 

measurements were made prior to January 1, 2007.38 Gas consumption used in Equation 11 would be determined using the 

estimation and apportioning methods discussed above in sections 3.2 and 3.3. 

E(N2O)j N , *(1 UN , ) * (1 a N , *d N , )*0.001 2 2 2 2 = C O j − O j − O j O j (Eq.11) 

Where: 

E(N2O)j = Annual emissions of N2O for N2O-using process j (metric tons). 

CN2O,j = Amount of N2O consumed for N2O-using process j and apportioned to N2O processes (kg). 

UN2O,j = Process utilization factor for N2O-using process j. 

 

38 If a third party has measured facility-specific N2O utilization factors, the conditions under which the measurements were made must 

be representative of the facility’s N2O-emitting processes. 
Subpart I Technical Support Document 

November 2010 18

a N2O,j = Fraction of N2O used in N2O-using process j with abatement systems. 

dN2O,j = Fraction of N2O for N2O-using process j destroyed by abatement devices connected process j. 

0.001 = Conversion factor for kg to metric tons. 

j = Type of N2O-using process. 

Alternatively, default N2O utilization factors for CVD and other N2O-using manufacturing processes would be applied in 

Equation 11. The default N2O utilization factor for CVD used is 20 percent (emission factor of 0.8), which is the midpoint 

of the utilization range of 0 percent to 40 percent. EPA determined the upper bound of this range through information 

collected in an industry survey presented in a comment received in response to the April 2009 rule proposal. This industry 

survey concluded that on average the utilization of N2O for all processes at a fab is ~40 percent. In the industry survey, the 

measured utilization factors were largely from newer 300 mm manufacturing equipment. EPA did not consider the 40 

percent as representative because N2O utilization of older manufacturing equipment, such as 150 mm and 250 mm tools is 

not fully represented. In addition, the information provided did not fully identify the specific processes from which the 

average N2O utilization factor was calculated. EPA understands that the majority of N2O is used in CVD processes; 

therefore 40 percent was considered the upper bound of the range for the CVD default N2O utilization factor. To be 

conservative and to avoid the potential for underestimation of emissions the lower bound of ~0 percent was considered. 

For other manufacturing processes, such as chamber cleaning, the default N2O utilization factor applied would be 0 percent 

(emission factor of 1.0), which is equivalent to assuming that all N2O used in manufacturing processes, other than CVD, is 

emitted. EPA took this approach because of a lack of information about N2O utilization for other N2O-using process. 

3.5 Options for Estimating Heat Transfer Fluids (HTFs) Emissions 

3.5.1 IPCC Tier 1 Approach 

The Tier 1 approach for HTF emissions is based on the utilization capacity of a semiconductor facility multiplied by a 

default emission factor. Although, the Tier 1 approach has the advantages of simplicity, it relies on a default emissions 

factor to estimate HTF emissions and has relatively high uncertainty compared to the Tier 2 approach (IPCC, 2006). 

3.5.2 IPCC Tier 2 Approach 

The IPCC Tier 2 approach, which is a mass-balance approach, uses company-specific data and accounts for differences 

among electronics manufacturing facilities’ HTFs (which vary in their global warming potentials), leak rates, and service 

practices, and has an uncertainty on the order of ±20 percent at the 95 percent confidence interval (IPCC, 2006). Equation 

12 below shows the company-specific mass-balance equation for estimating HTF emissions. Facilities are required to 

provide the total nameplate capacity (HTF charge) of equipment that contains fluorinated heat transfer fluids “newly 

installed” during the reporting period. 

*( )*0.001 i i iB i i i iE Di EH = density I + P − N + R − I − (Eq. 12)

Where: 

EHi = Emissions of fluorinated GHG heat transfer fluid i (metric tons/year). 

densityi = Density of fluorinated heat transfer fluid i (kg/l). 

IiB = Inventory of fluorinated heat transfer fluid i in containers other than equipment at the beginning of 

the reporting year (in stock or storage) (l). 

Pi = Acquisitions of fluorinated heat transfer fluid i during the reporting year (l). Includes amounts 

purchased from chemical suppliers, amounts purchased from equipment suppliers with or inside of 

equipment, and amounts returned to the facility after off-site recycling. 

Ni = Total nameplate capacity (full and proper charge) of equipment that uses fluorinated heat transfer 

fluid i and that is newly installed during the reporting year (l). 

Ri = Total nameplate capacity (full and proper charge) of equipment that uses fluorinated heat transfer 

fluid i and that is removed from service during the current reporting year (l). 
Subpart I Technical Support Document 

November 2010 19

IiE = Inventory of fluorinated heat transfer fluid i (in containers other than equipment) at the end of the 

reporting year (in stock or storage) (l). 

Di = Disbursements of fluorinated heat transfer fluid i during the reporting year (l). Includes amounts 

returned to chemical suppliers, sold with or inside of equipment, and sent off site for verifiable 

recycling or destruction. 

0.001 = Conversion factor from kg to metric tons. 

i = Heat transfer fluid. 

3.6 Options for Reporting Controlled Emissions from Abatement Systems 

While the 2006 IPCC Guidelines offer gas-specific default DREs, these values were optimized for specific processes and 

tools, and are not expected to be representative for all tools and gas flow rates. The IPCC default DRE values are also not 

applicable to abatement systems which cannot abate CF4 at DREs greater than 85 percent (IPCC, 2006). Because of the 

aforementioned reasons and to ensure the accuracy of controlled emissions39 estimations, EPA evaluated the following two 

options for the reporting of controlled emissions: the use of an EPA developed DRE default value and the direct, proper 

measurement of DRE values using EPA’s Protocol for Measuring Destruction or Removal Efficiency of Fluorinated 

Greenhouse Gas Abatement Equipment in Electronics Manufacturing (EPA 430-R-10-003) (EPA DRE Protocol) (EPA, 

2010). As part of both of these options, EPA evaluated requiring certification of proper installation, maintenance, and 

operation of abatement systems, as well as monitoring the uptime of abatement systems. 

3.6.1 Proper Installation, Operation, and Maintenance 

There are many abatement system manufacturers, all of whom manufacture many models of systems that are marketed as 

fluorinated GHG-destruction capable (Beu, L. 2005). While some of these systems may be capable of destroying some 

fluorinated GHGs, they may not be effective in abating CF4 (Beu, L., 2005), which in some processes can constitute 10 

percent – 20 percent (by volume) of fluorinated GHG exhaust composition (EPA, 2008d). This variability may be partially 

attributable to installation as well as operating and maintenance practices (Beu, L. 2005), although variations in how 

destruction is measured may also contribute to this variability (Beu, L., 2005). Additionally it is well known across the 

industry that abatement system performance varies greatly depending on a variety of abatement device and process 

parameters such as temperature, flow and exhaust composition (Beu, L., 2005, EPA 2008c, 2008d)). 

Therefore, ensuring that abatement systems are properly installed, operated, and maintained according to manufacturers’ 

specifications is important to reduce the likelihood of inaccurate estimations of DREs. It should be noted that this is also in 

line with 2006 IPCC applicability requirements for reporting controlled emissions due to abatement system use 

(IPCC,2006). 

3.6.2 Monitoring Abatement System Uptime 

Applying a DRE value that is not discounted for the time an abatement system at a facility is being operated within the 

range of parameters as specified in the operations manual provided by the system manufacturer (or is on “operational 

mode”), would result in an underestimation of total facility emissions. Uptime refers to the ratio of the total time during 

which the abatement system is in an operational mode with fluorinated GHGs or N2O flowing through production process 

tool(s) connected to that abatement system, to the total time during which fluorinated GHGs or N2O are flowing through 

production process tool(s) connected to that abatement system. An exception to this is time during which exhaust flows are 

passed through a redundant abatement system40 that is in the same abatement system class41 as the primary abatement 

system. Such time may be included in the uptime of the primary system. 

 

39 Controlled emissions are defined as the quantity of emissions that are released to the atmosphere after application of an emission 

control device (e.g., abatement system). 

40 A redundant abatement system is defined as a system that is specifically designed, installed and operated for the purpose of destroying 

fluorinated GHGs and N2O gases. A redundant abatement system is used as a backup to the main fluorinated GHGs and N2O abatement 

system during those times when the main system is not functioning or operating in accordance with design and operating specifications. 

41 Class means a category of abatement systems grouped by manufacturer model number(s) and by the gas that the system abates, 

including N2O and carbon tetrafluoride (CF4) direct emissions and by-product formation, and all other fluorinated GHG direct emissions 

and by-product formation. Classes may also include any other abatement systems for which the reporting facility wishes to report 
Subpart I Technical Support Document 

November 2010 20

Equation 13 below can be used to calculate the fraction of input gas destroyed or removed in abatement systems connected 

to process tools where a recipe, process sub-type, or process type is used. This number is used to calculate the annual 

emissions from input gas and by-product in the above Equations 6 and 7, respectively. Equation 14 below is used to 

calculate the uptime. 

∑

∑

=

p

ijp

p

ijp ijp p

i j C

C d u

d

* *

, (Eq. 13) 

dij = Fraction of input gas i destroyed or removed in abatement systems connected to process tools where 

recipe, process sub-type, or process type j is used (decimal fraction). 

Cijp = Amount of input gas i consumed for recipe, process sub-type, or process type j fed into abatement system 

p (kg). 

dijp = Destruction or removal efficiency for input gas i in abatement system p connected to process tools where 

recipe, process sub-type, or process type j is used (decimal fraction). 

up = Uptime of abatement system (decimal fraction). (see Eq. 14) 

i = Input gas. 

j = Recipe, process sub-type, or process type. 

p = Abatement system. 

p

p

p T

t

u = (Eq. 14) 

up = The uptime of abatement system p (decimal fraction). 

tp = The total time in which abatement system p is in an operational mode when fluorinated GHGs or N2O are 

flowing through production process tool(s) connected to abatement system p (hours). 

Tp = Total time in which fluorinated GHGs or N2O are flowing through production process tool(s) connected 

to abatement system p (hours). 

p = Abatement system. 

EPA considered two options for values for dijp expressed in Equation 13 above, the use of an EPA developed DRE factor, 

or properly measured DREs. Both of these options are discussed in the following sections. 

3.6.3 EPA Default DRE Value 

As discussed previously, the 2006 IPCC gas-specific default DRE values were optimized for specific processes and tools. 

However DREs are expected to vary across abatement systems and gas flow rates. For this reason, EPA estimates that the 

use of the IPCC default DRE value will result in controlled emissions estimates that are not representative of actual facility 

operations. Manufacturer supplied DREs may also result in emissions estimates that are not representative of actual facility 

operations because the DRE itself may have been incorrectly measured due to a failure to account for the effects of dilution 

(e.g., CF4 can be off by as much as a factor of 20 to 50 and C2F6 can be off by a factor of up to 10 [Burton, 2007].) This 

understanding is supported by industry assessments as presented in Beu, 2005. Therefore, EPA developed a default DRE to 

be used to report controlled emissions provided that the abatement system for which the default value is representing is 

properly installed, operated, and maintained and is specifically designed for fluorinated GHG and N2O abatement. 

 

controlled emissions provided that class is identified. 
Subpart I Technical Support Document 

November 2010 21

EPA developed the DRE default value using data from the EPA DRE measurement program, in which measurements have 

been made at three separate facilities.42 All of the data collected through the measurement program properly took into 

account the effects of dilution. Using the DRE data set from these measurement studies, the following data selection 

criteria were applied to determine values to include in the development of the default DRE. 

• Data must be from abatement devices that were properly installed, operated, and maintained, as well as 

designed to abate fluorinated GHGs and N2O. 43 This is consistent with the requirements for all abatement 

systems for which emissions are reported. In cases where this criterion was not met, the DRE values measured 

were often indistinguishable from zero. 

• Data must be in the form of a discrete value. Under the EPA DRE measurement program, some DRE 

measurements taken exceeded 99 percent. In these instance the measured data was expressed as a non-discrete 

value, (i.e. ≥ 99 percent (e.g. for CHF3, NF3, SF6)), which could not be applied to a method to determine a default 

DRE value. 

After evaluating the data based on these criteria, a set with a population of 11 measured DREs was used to develop the EPA 

default DRE value. These 11 DREs in the set were for CF4, and were measured on two thermal abatement systems each 

attached to two etch tools, which, in turn, had four chambers. This data set, which can be referenced in Table 3-3 contains 

results from two measurement conditions: (a) DRE measurement when the process tool plasma is off, when just CF4 and 

diluent gas from each chamber enters the abatement system, and (b) measurement of DRE during wafer processing, when 

CF4 together with other waste effluents leave the tool during actual wafer processing enters the abatement system. 

Measured DREs are shown for each etch tool. These are regarded as independent measurements of the DRE for abating 

CF4 for each abatement system. 

Table 3-3. Data Set Used to Develop EPA Default DRE Value 

Experiment ID Comment about experiment Measured CF4 DRE Source of dataa

FK15 #1 No plasma 87.5 Table IV 

FK15 #2 No plasma 63.1 Table IV 

FK15 #3 No plasma 79.4 Table IV 

FK15 #4 No plasma 77.4 Table IV 

FE05#1 No plasma 84.5 Table IV 

FE05#2 No plasma 82.2 Table IV 

FE05#3 No plasma 91.7 Table IV 

FE05#4 No plasma 96.0 Table IV 

Additional data from wafer tests, all chambers 

FK15 Trench etch, #1 & #3 only 83 Table VIII 

FK15 Via etch, #1 & #3 only 85 Table VIII 

FE05 FE etch #3 & #4 only 90 Table IX 

a Source: EPA, 2009. 

The summary statistics of the data set is presented in Table 3-3 is presented in 

Table 3-4. Also presented in 

 

42 For more information about the three studies, please see the following reports: Developing a Reliable Fluorinated Greenhouse Gas (FGHG) Destruction or Removal Efficiency (DRE) Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with

IBM (EPA 430-R-10-004); Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) 

Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with NEC Electronics, Inc. (EPA 430-R-10-005); and 

Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) Measurement Method for

Electronics Manufacturing: A Cooperative Evaluation with Qimonda (EPA 430-R-08-017).

43 While the EPA DRE measurement program only looked at abatement systems performance for fluorinated GHGs, it was assumed, for 

this use, that abatement systems that were designed to treat fluorinated GHGs were also designed to treat N2O. 
Subpart I Technical Support Document 

November 2010 22

Table 3-4 is the default DRE determined under the assumption that the measured DREs are distributed normally, and under 

the condition that 95 percent of the population will be above the value of 59% (i.e. the lower one-sided tolerance interval). 

For simplicity the value was rounded to one significant figure, equating to a default DRE of 60 percent. 

Table 3-4. Summary Statistics and Default DRE (Lower One-Sided Tolerance Interval) 

Mean of Measured Values Stdev of Measured Values Lower One-Sided 

Tolerance Interval 

No Plasma Measured DRE 82.73 10.054 - 

All Measured DRE 83.62 8.70 59 

3.6.4 Proper Measurement of Abatement System DRE 

For purposes of this rule, proper measurement of DRE values are those measured in accordance EPA’s DRE Protocol. The 

EPA DRE Protocol provides a practical and reliable method for measuring DREs of POU abatement devices while also 

providing flexibility to users. In addition, the use of the EPA DRE Protocol will ensure dilution is properly accounted for 

when determining DREs. (Please refer to the EPA DRE Protocol for a more detailed discussion on the justification for the 

development and application of the Protocol). 

A representative random sampling approach can be used to reduce burden associated with directly and properly measuring 

DREs of each abatement system at a facility. Therefore, EPA evaluated the use of a random sampling abatement system 

testing program (RSASTP) that would span all classes of abatement systems for which controlled emissions are reported. 

(Class means a category of abatement systems grouped by manufacturer model number(s) and by the gas that the system 

abates, including N2O and carbon tetrafluoride (CF4) direct emissions and by-product formation, and all other fluorinated 

GHG direct emissions and by-product formation. Classes may also include any other abatement systems for which the 

reporting facility wishes to report controlled emissions provided that class is identified.44) 

EPA qualitatively evaluated a range of options, from 10 percent to 100 percent, for what would constitute an appropriate 

annual representative sample of abatement systems to be tested in a reporting year. EPA selected 20 percent as it would 

balance the annual measurement burden for reporters and anticipate reliable maintenance periods and useful lifetimes of 

abatement systems. The RSASTP, with the selected 20 percent sample size, is described below. 

An annual representative sample would consist of three or 20 percent of installed abatement devices, whichever is greater, 

for each model type each year. In the case that 20 percent of total abatement systems at a facility does not equal a whole 

number, the number of devices to be tested should be rounded up.45 Each reporting period the DRE for a different three or 

20 percent set of devices would be measured. For systems for which a DRE has not been measured in a reporting period, a 

simple average of the measured DREs for systems of that specific class of abatement system is used. If redundant 

abatement systems are tested during periods of maintenance or repair, then the most recently measured or class average 

DRE for that system may be used. 

Using the RSASTP, as outlined in the paragraph above, would ensure the eventual measurement of each device but over the 

course of several years. The importance of measuring the DRE for each abatement device lies in the fact that the robustness 

of installed abatement systems varies by gas and operating principle. Therefore, while some abatement devices may 

receive regular maintenance and perform optimally, others may, because of the specific nature of the exhaust they treat, not 

be functioning properly. As well, it is well known across the industry that abatement system performance varies greatly 

depending on a variety of abatement device and process parameters such as temperature, flow and exhaust composition. 

(Beu, 2005) Facilities often develop and ultimately use new processes potentially every year, and the parameters of these 

processes vary, hence the use of the RSASTP will capture these changes over time. 

 

44 CF4 is a very stable chemical and especially difficult to effectively abate. It may be used as an input gas and generated as a byproduct 

of other fluorinated GHG process reactions. 

45 For example, 16 abatement devices, 20 percent of which equals 3.2; therefore, four abatement devices would be measured each year, 

which exceeds three. 
Subpart I Technical Support Document 

November 2010 23

4 QA/QC Requirements 

QA/QC methods for reporting fluorinated GHG and N2O emissions include: 

• Following the 2006 ISMI Guidelines for QA/QC procedures when measuring and calculating facility-specific, 

recipe specific fluorinated GHGs and N2O utilization and by-product formation rates. 

• Where facility-specific, recipe-specific fluorinated GHG and N2O utilization and by-product formation rates were 

measured prior to January 1, 2007, verify that the QA/QC procedures in International SEMATECH #01104197AXFR (2001 ISMI Guidelines) were followed when the factors were measured and calculated. 

• Following the QA/QC procedures in the EPA DRE Protocol when calculating abatement system DREs. 

• Demonstrating that as part of normal facility operations the inventory of gas stored in containers at the beginning 

of a reporting year is the same as the inventory of gas stored in containers at the end of the previous reporting year. 

QA/QC methods for reporting emissions from HTFs use and annual gas consumption for each fluorinated GHG and N2O 

used include: 

• Reviewing inputs to the gas consumption equation and HTF mass balance equation (Eqs. 8 and 12), to ensure 

inputs and outputs are all accounted for. 

• Ensuring no negative inputs are entered in the gas consumption equation and HTF mass balance equation (Eqs. 8 

and 12) and negative emissions are not calculated. 

• Ensuring that the beginning of year inventory is identical to the end of year inventory from previous year. 

• Ensuring that the total quantity of gas in containers in service at the end of the reporting year is accounted for as if 

the in-service containers were full. Ensuring also that the same quantity is accounted for in the inventory of gas 

stored in containers at the beginning of the subsequent reporting year. 

General QA/QC methods include: 

• Ensuring all flowmeters, weigh scales, pressure gauges, and thermometers used to measure quantities that are used 

to meet requirements of subpart I have an accuracy and precision of one percent of full scale or better. 

5 Procedures for Estimating Missing Data 

It is expected that collecting gas consumption data and quantifiable metrics for apportioning gas consumption will always 

be feasible for facilities, with the exception of the time period facilities are permitted to use Best Available Monitoring 

Methods (BAMM).46 When estimating HTF emissions, the use of the mass-balance approach requires correct records for 

all inputs. Therefore facilities that use HTFs and have missing data for one or more of the inputs for the mass-balance 

equation (see Eq. 12) can estimate HTF emissions using the arithmetic average of the emission rates for the reporting year 

immediately preceding the period of missing data and the months immediately following the period of missing data. 

Alternatively, missing information may be estimated from the heat transfer fluid supplier’s records. All methods and values 

used for all missing data values must be documented. 

6 Reporting and Recordkeeping Procedures 

The following data, which is additional to the information generally required to be reported and/or retained as records for 

all facilities covered under the MRR (see §98.3(c) and §98.3(g) (74 FR 56379, October 2009), would be useful for 

confirming emissions calculations and/or calculating emission factors that could be compared across facilities for quality 

control purposes: 

• For each facility report: 

 

46 See the Electronics Manufacturing section of the preamble to the Final Rule for a discussion on the use of Best Available Monitoring 

Methods under subpart I. 
Subpart I Technical Support Document 

November 2010 24

o Annual manufacturing capacity of a facility. 

o For facilities that manufacture semiconductors, the diameter of wafers manufactured at the facility. 

o Annual emissions of: 

 Each fluorinated GHG emitted from each process type for which the facility is required to 

calculate emissions. 

 Each fluorinated GHG emitted from each individual recipe (including those in a set of similar 

recipes), or process sub-type. 

 N2O emitted from each chemical vapor deposition processes and from other N2O-using 

manufacturing processes. 

 Each HTF emitted. 

o The method used to calculate fluorinated GHG emissions. 

o Annual production in terms of substrate surface area (e.g., silicon, PV-cell, glass). 

o When factors for fluorinated GHG process utilization and by-product formation rates and/or N2O 

utilization factors other than the default values provided in the appendices are used, the 

following: 

 The recipe-specific utilization and by-product formation rates for each individual recipe 

(or set of similar recipes) and/or facility-specific N2O utilization factors. 

 For recipe-specific utilization and by-product formation rates, the film or substrate that 

was etched/cleaned and the feature type that was etched, as applicable. 

 Certification that the recipes included in a set of similar recipes are similar. 

 Certification that the measurements for all reported recipe-specific utilization and byproduct formation rates and/or facility specific N2O utilization factors were made using 

the 2006 ISMI Guidelines, or the 2001 ISMI Guidelines if measurements were made 

prior to January 1, 2007. 

 Source of the recipe-specific utilization and by-product formation rates and/or facilityspecific-N2O utilization factors. 

 Certification that the conditions under which the measurements were made for facilityspecific N2O utilization factors are representative of the facility’s N2O-emitting 

production processes. 

o Annual gas consumption for each fluorinated GHG and N2O, including where the facility used 

less than 50 kg of a particular fluorinated GHG or N2O used at the facility. For all fluorinated 

GHGs and N2O used at the facility for which emissions have not been calculated, the chemical 

name of the fluorinated GHG used, the annual consumption of the gas, and a brief description of 

its use. 

o All inputs used to calculate gas consumption of each fluorinated GHG and N2O used. 

o Disbursements of each fluorinated GHG and N2O during the reporting year. 

o All inputs used to calculate disbursements for each fluorinated GHG and N2O used, including all facilitywide gas-specific heel factors used for each fluorinated GHG and N2O. If the facility used less than 50 kg 

of a particular fluorinated GHG during the reporting year, facility-wide gas-specific heel factors do not 

need to be reported for those gases. 

o Annual amount of each fluorinated GHG consumed for each recipe, process sub-type, or process type, as 

appropriate, and the annual amount of N2O consumed for each chemical vapor deposition and other 

electronics manufacturing production process. 

o All apportioning factors used to apportion fluorinated GHG and N2O consumption. 

o For the facility-specific apportioning model used to apportion fluorinated GHG and N2O consumption the 

following: 

 Identification of the quantifiable metric used in the facility-specific engineering model to 

apportion gas consumption. 

 The start and end dates selected to monitor for verification of the model. 
Subpart I Technical Support Document 

November 2010 25

 Certification that the gases selected for comparisons correspond to the largest quantities 

consumed on a mass basis, at the facility in the reporting year for the plasma etching process 

type and the chamber cleaning process type. 

 The result of the calculations comparing the actual and modeled gas consumptions. 

o Fraction each fluorinated GHG or N2O fed into a recipe, process sub-type, or process type that is fed into 

tools connected to abatement systems. 

o Fraction of each fluorinated GHG or N2O destroyed or removed in abatement systems connected to 

process tools where a recipe, process sub-type, or process type is used, as well as all inputs and 

calculations used to determine the inputs to calculate this fraction. 

o Inventory and description of all abatement devices through which fluorinated GHGs or N2O 

flow at the facility, including the number of devices of each manufacturer, model numbers, 

manufacturer claimed fluorinated GHG and N2O DREs, if any, and records of DRE 

measurements over their in-use lives. The inventory of abatement systems must describe the 

tools with model numbers and the recipe(s), process sub-type, or process type for which these 

systems treat exhaust. 

o For each abatement system through which fluorinated GHGs or N2O flow at the facility, for which 

controlled emissions are reported, the following: 

 Certification that the abatement device has been installed, maintained, and operated in 

accordance with manufacturers’ specifications. 

 All inputs and results of calculations made accounting for the uptime of abatement systems used 

during the reporting year. 

 The default DRE value or properly measured DREs for each abatement system used in that 

reporting year. 

 Where the default DRE value is used to report controlled emissions, certification that the 

abatement systems for which emissions are being reported were specifically designed for 

fluorinated GHG and N2O abatement. Documentation stating that the system was designed for 

fluorinated GHG and N2O abatement should be provided to show this. 

 Where properly measured DREs or class averages of DREs are used, the following must be 

reported: 

• A description of the class, including the abatement system manufacturer and model 

number, and the fluorinated GHG and N2O in the process effluent stream. 

• The total number of systems in that class for the reporting year. 

• The total number of systems for which DREs were properly measured in that class for 

the reporting year. 

• A description of the calculation used to determine the class average, including all inputs 

of the calculation. 

• A description of method of randomly selecting class members for testing. 

o For HTF emissions, inputs used in the mass-balance equation for each fluorinated GHG used. 

o Where missing data procedures were used to estimate inputs into the HTF mass-balance 

equation, the number of times missing data procedures were followed in the reporting year, the 

method used to estimate the missing data, and the estimates of those data. 

o A brief description of each “best available monitoring method” used, the parameter measured or 

estimated using the method, and the time period during which the “best available monitoring 

method” was used. 

• Retain records of: 

o All data used and copies of calculations made as a part of estimating gas consumption and 

emissions. 
Subpart I Technical Support Document 

November 2010 26

o Documentation for the values used for fluorinated GHG and N2O utilization and by-product 

formation rates. Where facility-specific, recipe-specific gas utilization and by-product formation 

rates were used, the following records must also be retained: 

 Complete documentation and final report for measurements for recipe-specific 

utilization and by-product formation rates demonstrating that the values were measured 

using the 2006 ISMI Guidelines, provided the measurements were made prior to 

January 1, 2007. 

 Documentation that recipe-specific utilization and by-product formation rates 

developed for the facility are measured for recipes that are similar to those used at the 

facility. Included in the documentation, recorded to two significant figures, should be 

reactor pressure, flow rates, chemical composition, applied RF power, direct current 

(DC) bias, temperature, flow stabilization time, and duration. 

 Documentation that the facility’s N2O measurements are representative of the N2Oemitting processes at the facility. 

 The date and results of the initial and any subsequent tests to determine utilization and 

by-product formation rates. 

o Documentation for the facility-specific engineering model used to apportion fluorinated GHG 

and N2O consumption. This documentation must be part of the site GHG Monitoring Plan. At a 

minimum, the following must be retained: 

 A clear, detailed description of the facility-specific model, including how it was 

developed; the quantifiable metric used in the model; all sources of information, 

equations, and formulas, each with clear definitions of terms and variables; and a clear 

record of any changes made to the model while it was used to apportion fluorinated 

GHG and N2O consumption across individual recipes (including those that are similar 

recipes), process sub-types, and/or process types. 

 Sample calculations used for developing a recipe-specific, process sub-type-specific, or 

process type-specific gas apportioning factor for the fluorinated GHG used at a facility 

in the largest quantity, on a mass basis, during the reporting year for each individual 

recipe (including those that are similar recipe), process sub-type, or process type. 

o For each abatement device through which fluorinated GHGs or N2O flows at the facility, for 

which the facility is reporting controlled emissions, the following: 

 Documentation to certify that the abatement device is installed, maintained, and 

operated in accordance with manufacturers’ specifications. 

 Abatement system calibration and maintenance records. 

 Where the default DRE value is used, documentation from the abatement system 

supplier describing the equipment’s designed purpose and emission control capabilities 

for fluorinated GHG and N2O. 

 Where properly measured DRE is used to report emissions, dated certification by the 

technician who made the measurement that the DRE was calculated according to 

methods in the EPA’s DRE Protocol, complete documentation of the results of any 

initial and subsequent tests, and final reports as specified in the EPA DRE Protocol. 

o Purchase records for gas purchased. 

o Invoices for gas purchases and sales. 

o Documents and records used to monitor and calculate abatement system uptime. 
Subpart I Technical Support Document 

November 2010 27

7 References 

Beu, L. (2005). “Reduction of Perfluorocarbon (PFC) Emissions: 2005 State-of-the-Technology Report”, TT#0510469AENG, International SEMATECH Manufacturing Initiative (ISMI), December 2005. Available at: 

http://www.epa.gov/highgwp/semiconductor-pfc/documents/final_tt_report.pdf. 

Burton, C.S., & Beizaie, R. (2001). EPA’s PFC Emissions Model (PEVM) v. 2.14: Description and Documentation. 

Prepared for Office of Global Programs, U. S. Environmental Protection Agency, Washington, DC. November 2001. 

Available at: http://www.epa.gov/highgwp/semiconductor-pfc/documents/pevm_draft.pdf. 

Burton (2006). PV Emissions during Photovoltaic (PV) Cell Fabrication: A Scoping Report. Available in EPA docket 

EPA-HQ-OAR-2009-0927. 

Burton (2007). Assessing the need for FC abatement standards, Solid State Technology, January 2007. Available at: 

http://www.electroiq.com/index/display/semiconductors-article-display/281422/articles/solid-state-technology/volume50/issue-1/departments/industry-forum/assessing-the-need-for-fc-abatement-standards.html. 

Chen et. Al (2003). Chen, Xing, W. Holber, P. Loomis, E. Sevillano, S-Q Shao, S. Bailey and M. Goulding. Advances in 

Remote Plasma Sources for Cleaning 300 mm and Flat Panel CVD Systems. Semiconductor Magazine, August 2003, 6 pp. 

Available at: http://www.mksinst.com/docs/r/PRGcvdcleanTP.pdf. 

DisplaySearch (2007). Flat Panel Fabs on a Disk. Q2 2007 Edition. Available for purchase at: 

http://www.displaysearch.com/cps/rde/xchg/displaysearch/hs.xsl/index.asp. 

Earth Policy Institute (2007). Solar Cell Production Jumps 50 Percent in 2007. Author: Jonathan G. Dorn. Available at: 

http://www.earth-policy.org/index.php?/indicators/C47/. 

EPA (2008a) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007. U.S. Environmental Protection Agency, 

Washington, DC. 

EPA (2008b). Uses and Emissions of Liquid PFC Heat Transfer Fluids from the Electronics Sector. Office of Air and 

Radiation Office of Atmospheric Programs, Climate Change Division, U.S. Environmental Protection Agency, 

Washington, DC. Available at: http://www.epa.gov/semiconductor-pfc/documents/pfc_heat_tranfer_fluid_emission.pdf. 

EPA (2008c). Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) 

Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with NEC Electronics, Inc. (EPA 430-R10-005). Office of Air and Radiation Office of Atmospheric Programs, Climate Change Division, U.S. Environmental 

Protection Agency, Washington, DC. Available at: http://www.epa.gov/highgwp/semiconductorpfc/documents/nec_report.pdf47. 

EPA (2008d). Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) 

Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with Qimonda (EPA 430-R-08-017). 

Office of Air and Radiation Office of Atmospheric Programs, Climate Change Division, U.S. Environmental Protection 

Agency, Washington, DC. Available at: http://www.epa.gov/highgwp/semiconductorpfc/documents/qimonda_report.pdf.47

EPA (2009). Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) 

Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with IBM (EPA 430-R-10-004), Office of 

Air and Radiation Office of Atmospheric Programs, Climate Change Division, U.S. Environmental Protection Agency, 

 

47 The NEC and Qinonda studies were conceived and conducted over the course of 2006 through 2007, and are referenced as such in the 

Electronics Manufacture preamble. 
Subpart I Technical Support Document 

November 2010 28

Washington, DC. Available at: http://www.epa.gov/highgwp/semiconductor-pfc/documents/ibm_report.pdf. 

EPA (2010). Protocol for Measuring Destruction or Removal Efficiency (DRE) of Fluorinated Greenhouse Gas Abatement 

Equipment in Electronics Manufacturing (EPA 430-R-10-003), Office of Air and Radiation Office of Atmospheric 

Programs, Climate Change Division, U.S. Environmental Protection Agency, Washington, DC. Available in EPA docket 

EPA-HQ-OAR-2009-0927. 

Gaitan, M. & Takacs, M. (2008). The state of standards. Solid State Technology, February 2008. Available at: 

http://www.electroiq.com/index/display/semiconductors-article-display/319143/articles/solid-state-technology/volume51/issue-2/departments/mems/the-state-of-standards.html. 

International Sematech (2006). Guideline for Characterization of Semiconductor Process Equipment. International 

Sematech, Technology Transfer # 06124825A-ENG, December 22, 2006. Available in EPA docket EPA-HQ-OAR-2009-

0927. 

International Sematech (2001). Guideline for Characterization of Semiconductor Process Equipment. International 

Sematech, Technology Transfer #01104197A-XFR, 2001. Available in EPA docket EPA-HQ-OAR-2009-0927. 

International Sematech (2004). Specification for Definition and Measurement of Equipment Reliability, Availability, and 

Maintainability. SEMI Standard E10-0304, March 2004. Available for purchase at: http://www.semi.org/en/index.htm . 

Contact the EPA Docket Center (EPA docket EPA-HQ-OAR-2009-0927) for more information. 

IPCC (2006) 2006 IPCC Guidelines for National Greenhouse Gas Inventories. The National Greenhouse Gas Inventories 

Programme, The Intergovernmental Panel on Climate Change, H.S. Eggleston, L. Buendia, K. Miwa, T Ngara, and K. 

Tanabe (eds.). Hayama, Kanagawa, Japan. Available at: http://www.ipccnggip.iges.or.jp/public/2006gl/pdf/3_Volume3/V3_6_Ch6_Electronics_Industry.pdf. 

ITRS (2008) International Technology Roadmap for Semiconductors: 2007 Update. January 2008. This and earlier 

editions and updates are available at <http://public.itrs.net> Information about the number of interconnect layers for years 

1990 – 2010 is contained in Burton and Beizaie, 2001. PEVM is updated using new editions and updates of the ITRS, 

which are published annually. 

Lee et al. (2007). Evaluation Method on Destruction and Removal Efficiency of Perfluorocompounds from Semiconductor 

and Display Manufacture. Bull. Korean Chem. Soc. 28 (8), 1383-1388 (2007). Available at: 

http://newjournal.kcsnet.or.kr/main/j_search/j_download.htm?code=B070824. 

Li et al., (2001). Improved Technique for Evaluating Point-of-use Abatement Systems. Semiconductor Fabtech, 14th 

Edition, June 2001. Available at: http://www.fabtech.org/. 

Lyshevshi, S. (2001). MEMS and NEMS System, Devices, and Structures, CRC Press. Available for purchase at: 

http://www.crcpress.com/ecommerce_product/product_detail.jsf?catno=1262&isbn=0000000000000. 

Roedern, B.V. & Ullal, H.S. (2008). Critical issues for commercialization of thin-film PV technologies. Solid State 

Technology, February 2008. Available at: http://www.electroiq.com/index/display/semiconductors-articledisplay/319149/articles/solid-state-technology/volume-51/issue-2/features/thin-film-technology/critical-issues-forcommercialization-of-thin-film-pv-technologies.html. 

Semiconductor Equipment and Materials Industry (SEMI) (2008). World Fab Watch, January 2007 Edition. Available for 

purchase at: http://www.semi.org/en/index.htm. 

VLSI Research, Inc. (2008). Document 327028, V6.12.1—Worldwide Silicon Demand by Wafer Size, by Linewidth and 

by Device Type. January 2007. Available for purchase at: http://www.vlsiresearch.com. 
Subpart I Technical Support Document 

November 2010 29

Appendix A - Default Emission Factors for Threshold Applicability Determination and Etch and 

Clean Emission Estimation Methods 

Table A-1. Default Emission Factors for Threshold Applicability Determination 

Emission Factors EFi

Product Type CF4 C2F6 CHF3 C3F8 NF3 SF6

Semiconductors (kg/m2) 0.90 1.00 0.04 0.05 0.04 0.20 

LCD (g/m2) 0.50 NA NA NA 0.90 4.00 

MEMS (kg/m2) NA NA NA NA NA 1.02 

Notes: NA denotes not applicable based on currently available information. 

Source: IPCC, 2006 
Subpart I Te

November 2010 

Table A-2. Default Emission Factors (1-Uij) for Gas Utilization (Uij) and By-Product Formation Rates (Bijk) for MEMS, LCD, 

Greenhouse Gases with TAR GWP Gree

witho

Process Gas 

CF4 C2F6 CHF3 CH2F2 C3F8 c-C4F8 NF3 Remote NF3 SF6 C4F6 

Etch 1-Ui 0.7* 0.4* 0.4* 0.06* NA 0.2* NA 0.2 0.2 0.1 CVD 1-Ui 0.9 0.6 NA NA 0.4 0.1 0.02 0.2 NA NA Etch BCF4 NA 0.4* 0.07* 0.08* NA 0.2 NA NA NA 0.3* Etch BC2F6 NA NA NA NA NA 0.2 NA NA NA 0.2* CVD BCF4 NA 0.1 NA NA 0.1 0.1 0.02† 0.1† NA NA CVD BC2F6 NA NA NA NA NA NA NA NA NA NA 

MEMS MANUFACTURINGa

CVD BC3F8 NA NA NA NA NA NA NA NA NA NA 

Etch 1-Ui 0.6 NA 0.2 NA NA 0.1 NA NA 0.3 NA CVD 1-Ui NA NA NA NA NA NA 0.03 0.3 0.9 NA Etch BCF4 NA NA 0.07 NA NA 0.009 NA NA NA NA Etch BCHF3 NA NA NA NA NA 0.02 NA NA NA NA Etch BC2F6 NA NA 0.05 NA NA NA NA NA NA NA CVD BCF4 NA NA NA NA NA NA NA NA NA NA CVD BC2F6 NA NA NA NA NA NA NA NA NA NA 

LCD MANUFACTURING 

CVD BC3F8 NA NA NA NA NA NA NA NA NA NA 

Etch 1-Ui 0.7 0.4 0.4 NA NA 0.2 NA NA 0.4 NA CVD 1-Ui NA 0.6 NA NA 0.1 0.1 NA 0.3 0.4 NA Etch BCF4 NA 0.2 NA NA NA 0.1 NA NA NA NA Etch BC2F6 NA NA NA NA NA 0.1 NA NA NA NA CVD BCF4 NA 0.2 NA NA 0.2 0.1 NA NA NA NA CVD BC2F6 NA NA NA NA NA NA NA NA NA NA 

PV MANUFACTURING 

CVD BC3F8 NA NA NA NA NA NA NA NA NA NA 

Notes: NA denotes not applicable based on currently available information ‡ The default emission factors for F2 and COF2 may be applied to cleaning low-k CVD reactors with ClF3. * Estimate includes multi-gas etch processes a MEMS manufacturing EFs are consistent with the 2006 IPCC Tier 2b EFs for the manufacture of semiconductors. † Estimate reflects presence of low-k, carbide and multi-gas etch processes that may contain a C-containing FC additive 

Source: IPCC, 2006
Subpart I Te

November 2010 

Table A-3. Default Emission Factors (1-Uij) for Gas Utilization (Uij) and By-Product Formation Rates (Bijk) for Semiconductor 

mm and 200 mm Wafer Sizes 

Process Gas i 

Process Type/Sub-type CF4 C2F6 CHF3 CH2F2 C3F8 c-C4F8 NF3 SF6 C

Plasma Etching 

 1-Ui 0.69 0.56 0.38 0.093 NA 0.25 0.038 0.20 0 BCF4 NA 0.23 0.026 0.021 NA 0.19 0.0040 NA 0 BC2F6 NA NA NA NA NA 0.08 NA NA 0 BC3F8 NA NA NA NA NA NA NA NA N

Chamber Cleaning 

In situ plasma cleaning  1-Ui 0.92 0.55 NA NA 0.40 0.10 0.18 NA N BCF4 NA 0.19 NA NA 0.20 0.11 0.011 NA N BC2F6 NA NA NA NA NA NA NA NA N BC3F8 NA NA NA NA NA NA NA NA NRemote plasma cleaning  1-Ui NA NA NA NA NA NA 0.018 NA N BCF4 NA NA NA NA NA NA 0.0047 NA N BC2F6 NA NA NA NA NA NA NA NA N BC3F8 NA NA NA NA NA NA NA NA NIn situ thermal cleaning  1-Ui NA NA NA NA NA NA NA NA N BCF4 NA NA NA NA NA NA NA NA N BC2F6 NA NA NA NA NA NA NA NA N BC3F8 NA NA NA NA NA NA NA NA N

Wafer Cleaning 

 1-Ui 0.77 NA NA 0.24 NA NA 0.23 0.20 N BCF4 NA NA NA NA NA NA NA NA N
Subpart I Te

November 2010 

Process Gas i 

Process Type/Sub-type CF4 C2F6 CHF3 CH2F2 C3F8 c-C4F8 NF3 SF6 C

 BC2F6 NA NA NA NA NA NA NA NA N BC3F8 NA NA NA NA NA NA NA NA NNotes: NA denotes not applicable based on currently available information. 

Table A-4. Default Emission Factors (1-Uij) for Gas Utilization (Uij) and By-Product Formation Rates (Bijk) for Semiconductor 

mm Wafer Size 

Process Gas i 

Process Type/Sub-type CF4 C2F6 CHF3 CH2F2 C3F8 c-C4F8 NF3 SF6 C

Plasma Etching 

 1-Ui 0.80 0.80 0.48 0.14 NA 0.29 0.32 0.37  BCF4 NA NA 0.0018 0.0011 NA 0.079 NA NA  BC2F6 NA NA 0.0011 NA NA 0.12 NA NA  BC3F8 NA NA NA NA NA NA NA NA 

Chamber Cleaning 

In situ plasma cleaning  1-Ui NA NA NA NA NA NA 0.23 NA  BCF4 NA NA NA NA NA NA 0.0046 NA  BC2F6 NA NA NA NA NA NA NA NA  BC3F8 NA NA NA NA NA NA NA NA Remote Plasma Cleaning 1-Ui NA NA NA NA 0.063 NA 0.018 NA  BCF4 NA NA NA NA NA NA 0.040 NA  BC2F6 NA NA NA NA NA NA NA NA  BC3F8 NA NA NA NA NA NA NA NA In Situ Thermal Cleaning 1-Ui NA NA NA NA NA NA 0.28 NA 
Subpart I Te

November 2010 

Process Gas i 

Process Type/Sub-type CF4 C2F6 CHF3 CH2F2 C3F8 c-C4F8 NF3 SF6 C

 BCF4 NA NA NA NA NA NA 0.010 NA  BC2F6 NA NA NA NA NA NA NA NA  BC3F8 NA NA NA NA NA NA NA NA 

Wafer Cleaning 

 1-Ui 0.77 NA NA 0.24 NA NA 0.23 0.20  BCF4 NA NA NA NA NA NA NA NA  BC2F6 NA NA NA NA NA NA NA NA  BC3F8 NA NA NA NA NA NA NA NA Notes: NA denotes not applicable based on currently available information. 
Subpart I Technical Support Document 

November 2010 34

Appendix B - Development of EPA Published Emission Factors for the Tier 2c and Tier 2d 

Methods 

To develop the default emission factors (EFs) for semiconductor manufacturing presented in Tables A-3 and A-4, EPA 

used industry data provided in cooperation with the Semiconductor Equipment and Materials International (SEMI), which 

redacted identifying company information prior to sharing the data with EPA.48 An example of the form in which EPA 

received data is presented in Figure B-1. All of the data EPA received was compiled in an EF development database. The 

complete database is presented in Table 5 of the report Draft Emission Factors for Refined Semiconductor Manufacturing 

Process Categories (EPA-HQ-OAR-2009-0927-0073) (“NODA database”).49 The EF data in the NODA database, which is 

identified by process sub-types and wafer technology, includes single- and multi-gas process chemistries. EF information 

is provided for single and multi-gas emission factors for utilization rates and by-product formation rates. The table denotes 

the dominant gas, the mass fraction emitted and the by-product formation rates expressed as a mass fraction of the 

dominant gas. The table also denotes the mass-emitted fractions of the other gases used when multiple gases are employed 

in either chamber cleaning or film etching emission processes. 

Some providers of data identified a broad process type (i.e., chamber cleaning, etching and wafer cleaning) as well as a 

process sub-type. For example, information pertaining to the chamber cleaning process type was identified by a chamber 

cleaning process sub-type (in-situ plasma, remote plasma, or in-situ thermal) as well. The NODA database identifies all 

information by the process sub-types of the Refined Method (see section 3.1.6), as the data collected by EPA was originally 

intended to be used to develop default emission factors for the Refined Method. Although the Refined Method was not 

included in the final rule, the emission factor data could be used to developed the default factors for the Tier 2c and Tier 2d

methods because the information in the database is on a more granular level than is required for these two methods. EFs 

were developed by wafer technology for the broad etch process type and the broad wafer cleaning process types using all 

relevant information in the NODA database (e.g., all etch information, regardless of the identified sub-type was used to 

develop the etch EFs). EFs were also developed for the three chamber cleaning process sub-types (in-situ plasma, remote 

plasma, and in-situ thermal) for each wafer technology. These EFs are presented in Tables A-3 and A-4. 

The EFs presented in Tables A-3 and A-4 are simple (unweighted) averages developed employing an approach similar to 

that used for the 2006 IPCC Guidelines. Each EF represents an average of the appropriate values in the NODA database 

with each entry given equal weight. The exact methods used to develop the EFs are further discussed in the report Draft 

Emission Factors for Refined Semiconductor Manufacturing Process Categories (EPA-HQ-OAR-2009-0927-0073). 

Measures Taken to Overcome Data Gaps

As evident by the “NA” entries in Tables A-3 and A-4 (NA denotes not applicable based on currently available 

information) and the information presented in the NODA database, there are still gaps in the EF data that are available to 

EPA. Using the rationale described below EPA has addressed these gaps.

 

48 See TECHNICAL SUPPORT DOCUMENT (UPDATED) FOR PROCESS EMISSIONS FROM ELECTRONICS MANUFACTURE 

(e.g., SEMICONDUCTORS, LIQUID CRYSTAL DISPLAYS, PHOTOVOLTAICS, AND MICRO-ELECTRO-MECHANICAL 

SYSTEMS): PROPOSED RULE FOR MANDATORY REPORTING OF GREENHOUSE GASES (March 22, 2010) and the Subpart I 

Notice of Data Availability (75 FR 26904) for more information on the data collection process and initiation. 

49 EPA initially intended to use the data provided in cooperation with SEMI to develop emission factors for the Refined Method. 

Therefore the data in the NODA database was originally used to develop draft emission factors for the Refined Method; however, EPA 

decided not to include the Refined Method in the final rule. 
Subpart I Technical Support Document 

November 2010 35

150 mm 

EPA received only one value for fluorinated GHG usage during device manufacture on 150 mm wafers. In the absence of 

additional emission data for 150 mm wafers, EPA assumed that the EFs for 200 mm technologies apply for 150 mm as 

well. EPA based this assumption on the belief that EFs for 150 mm processing technology are closer to 200 mm processing 

technologies than to 300 mm processing technologies [see Beu (2005)]. Moreover, EPA understands that a portion of the 

EFs for 200 mm processing in the NODA database were developed on early 200 mm equipment prior to efforts by device 

and equipment manufacturers to reduce fluorinated GHG usage, which occurred during the latter half of the 200 mm wafer 

era. The average draft EFs in Table A-3 reflect emission measurements made in the earlier and later portions of the 200 mm 

wafer era.50 To apply EFs for 300 mm wafer processing equipment to 150 mm might result in reported emissions being 

understated when EFs for 300 mm are smaller than those for 200 mm [see Beu (2005)]. This concern is supported by 

comparing the chamber cleaning EFs for 200 mm and 300 mm technologies. Reports in the 200 mm wafer era indicated 

that chamber cleaning accounted for the majority of fluorinated GHG usage. 

Wafer Cleaning 

300 mm Wafers

EPA received minimal information about emissions resulting from wafer cleaning in the semiconductor industry for 300 

mm wafers. In the available patent literature for plasma based bevel cleaning, a process was identified under the wafer 

cleaning process type that used two gases, CF4 and SF6. [e.g., see Kim et al. (2009)] EPA’s EF database, the NODA 

database, does not contain gas utilization information for SF6 for wafer cleaning, or any chamber cleaning process that may 

be analogous for wafer cleaning. EPA filled this gap in SF6 data by using a draft value based on the SF6 utilization for in 

situ chamber cleaning provided in the IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse 

Gas Inventories (Chapter 3, Table 3.15). (see IPCC, 2000) 

150/200 mm Wafers

No information for the wafer cleaning process type was available for 150 mm or 200 mm in the NODA database. As EPA 

understands, wafer cleaning processes were not used in the 150 mm and early 200 mm eras, but these processes began to 

phase into the industry in the late 200 mm era and the 300 mm era (F. Burkeen, et al, 2007). Therefore, to make it feasible 

for a facility processing 200 mm wafers to estimate emissions from any wafer cleaning activities EPA drew an analogy 

between the 300 mm and 150/200 mm wafer cleaning EFs. 

SF6 Emission Factor for 150/200 mm Etch 

The NODA database does not contain any information for SF6 for etching for the 150 mm or 200 mm wafer technologies. 

However, based on the information presented in the 2006 IPCC Guidelines, it is known that SF6 is used for etching 

processes for these technologies. To fill this gap in information, for the 150/200mm SF6 etch EF, EPA used the etch SF6

EF presented in the 2006 IPCC Guidelines. 

Modifications to the NF3 Emission Factor

EPA learned, through discussions with a major supplier of equipment, that its experience suggests that the utilization 

efficiency, U, of NF3 in contemporary units for cleaning chambers that process 200 mm and 300 mm wafers are similar, 

despite the latter having higher NF3 flow rates. RPS units, both 200 mm and 300 mm, carry the same guaranteed utilization 

efficiency of 95 percent; RPS units emit 5 percent or less of the NF3 used during chamber cleaning. Achieving similar 

utilization efficiencies in the two systems is accomplished by increasing the plasma power to the RPS units with higher 

flow rates. For 200 and 300 mm systems, the manufacturer’s measurement experience indicates that the NF3 utilization is of 

the order of 99 percent when operated under manufacturer’s specifications. The manufacturer also posited that utilization 

efficiencies should exceed 95 percent for typical, reasonably maintained RPS units. 

 

50 In using the term “200 mm era” EPA is referring to the period during which the majority of R&D expenditures by device and 

equipment manufacturers were directed to 200 mm wafers. Toward the end a wafer technology era, R&D attention shifted to the next 

generation of wafer technology, 300 mm wafers. 
Subpart I Technical Support Document 

November 2010 36

EPA’s review of the NODA database showed that the mean complement of utilization efficiencies, 〈(1- U)〉 or mean EFs, 

associated with 200 mm and 300 mm wafer processing for NF3 RPS were 0.0285 ±0.0390 and 0.0174 ±0.0285, 

respectively. Statistically, it is evident that the population means are equal, and that all the NF3 emission factor data in 

EPA’s NODA database may be considered as one population. EPA’s analysis is consistent with the manufacturer’s 

expectations although the mean utilizations for both wafer sizes fall below the tool manufacture’s measurement experience 

of 99 percent (EF = 0.01) but is also well above the performance expectation of 95 percent utilization (EF = 0.05). 

Review of NF3 RPS emission factors contained in EPA’s NODA database shows values that approach 0.20—80 percent 

utilization efficiencies, substantially below the expected performance utilization efficiency of 95 percent. Providers of NF3

utilization data to EPA did not describe the robustness or representativeness of the submitted data. EPA viewed in as 

reasonable to consider the possibility that the higher EFs might be outliers or anomalously high, that they might reflect one 

or more of four circumstances: (1) poorly measured EFs, (2) poorly maintained systems, (3) older RPS technologies, (4) 

operation outside manufacturer’s specifications. While the manufacturer agreed such high values could be outliers—

especially for values above 0.1 or utilization efficiencies below 90 percent—EPA was uncomfortable with removing such 

values without further consideration. 

EPA combined the 200 mm and 300 mm data points for NF3 RPS and posed the question whether the resulting distribution 

was better described with or without the larger values. For this analysis EPA assumed the variability in the set of emission 

factors could be described by a beta distribution, a distribution that (1) accounts for the skewness of the observations and 

(2) constrains values between zero and one, 0 ≤ (1 – Ui) < s, where s < 1. 

EPA’s analysis showed that a reasonable fit (p-value = 0.0037, chi-squared test) was obtained with s = 0.09 and removal of 

the top four EF values (0.1933, 0.1900, 0.1720 and 0.1120), which correspond to utilization efficiencies between 89 and 81 

percent, considerably below the manufacturer’s expected performance of 95 percent. The mean and standard deviation in 

emission factor of the reduced dataset was 0.0182 ± 0.0191 (1 standard deviation). A somewhat higher mean emission 

factor (5 percent) and standard deviation of 0.0191± 0.0211 (1 standard deviation) and somewhat poorer fit (p-value = 

0.0096, chi-squared) was obtained with s < 0.115 and removal of the top three values. 

Consideration of the information gleaned through industry together with EPA’s statistical analysis led EPA to choose the 

slightly lower mean value for the default EF (=0.0182 ± 0.0191 (1 standard deviation)) for RPS chamber cleaning with NF3

for both 200 and 300 mm wafer processing systems. After removal of the four highest values, the mean EFs for 200 mm 

and 300 mm RPS units remained statistically indistinguishable: 0.0204 ± 0.0202 and 0.0141 ± 0.0144, respectively. 

References

Beu (2005), “Reduction of Perfluorocompound (PFC) Emissions: 2005 State-of-the-Technology Report” (Technology 

Transfer #05104693A-Eng), December 2005. Available at: http://www.epa.gov/highgwp/semiconductorpfc/documents/final_tt_report.pdf. 

F. Burkeen, et al (2007), "Visualizing the Wafer's Edge," KLA-Tencor YMS Magazine, Winter 2007. Available in EPA 

docket (EPA-HQ-OAR-2009-0927) and at: 

http://208.194.225.108/company/magazine/spring07/YMS_Sp07_Visualizing.pdf. 

IPCC (2000), Intergovernmental Panel on Climate Change (IPCC 2000), “IPCC Good Practice Guidance and Uncertainty 

Management in National Greenhouse Gas Inventories” (Chapter 3, Table 3.15), 2000. Available at: http://www.ipccnggip.iges.or.jp/public/gp/english/. 

IPCC (2006) 2006 IPCC Guidelines for National Greenhouse Gas Inventories. The National Greenhouse Gas Inventories 

Programme, The Intergovernmental Panel on Climate Change, H.S. Eggleston, L. Buendia, K. Miwa, T Ngara, and K. 

Tanabe (eds.). Hayama, Kanagawa, Japan. Available at: http://www.ipccnggip.iges.or.jp/public/2006gl/pdf/3_Volume3/V3_6_Ch6_Electronics_Industry.pdf. 

Kim et al (2009). Patent 20070068900A1, March 29, 2007 and Kim et al. Patent 20090272402A1, November 5, 2009. 

Available at: http://www.google.com/patents/about?id=LYCbAAAAEBAJ&dq=20070068900A1 and 

http://www.google.com/patents/about?id=YJjJAAAAEBAJ&dq=20090272402A1. 
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November 2010 

Figure B-1. Data Form Submitted by Semiconductor Device Manufacturers and Equipment Manufacturers t

Information for Developing EPA’s Refined FLUORINATED GHG Emission Process Categories and Corresponding E

(one form per process of record)

Source/Contact (TBR)1 (For SEMI use, information redacted) Date of measurement Location of study (TBR) (For SEMI use, information redacted)Emission process category and subcategory (s) of process category2 

Emission Process Category Subcategory of Process Category Alternative P

Equipment (Manufacturer name/model number) (TBR)3

Letter denotes each reporting entity. 

(Information redacted, it is sought to facilitate sufficient consideration of equipment manufacturer wequipment usage in device manufacture.)

Patterning/etching subcategories (Check preference and explain each). Specify both film type and etched feature regardless of preference. 

Film Etch Feature Etch

Explanation: Specify/describe film type: Specify/describe etched feature: 

Substrate size (Si wafer) Measurement method/protocol4 (Either ISMI Guidelines or equivalent alternative measurement protocol with brief explanation rega

equivalent to ISMI Guidelines.)

Achieved ISMI Fluorine target mass balance >90%? Check answer.5

YES NO (Explain) 

Corresponding Emission Factors for Emission Process Categories 

Process Gases (i) CF4 C2F6 C3F8 c-C4F8 CHF3 SF6 NF3 C4F6 C5F8 C4F8O Measured emissions: 1-Ui6 Standard deviation: 
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November 2010 

Meas. CF4 byproduct, Bip7 CF4 B standard deviation: Meas. C2F6 byproduct, Bip7 C2F6 B standard deviation: Meas. C3F8 byproduct, Bip7 C3F8 B standard deviation: Unit of measurement (mass): No. of wafers in study (number of wafers measured) Comments 

Information for developing average emission factors 

Estimate of U. S. share of selected process usage category, % (Check answer) 

10% 20% 30% 40% 50% 60% 70% 80

Notes: 

1. TBR denotes To Be Redacted by SEMI. 2. Distinguish between four emission process categories: 1. Chamber Cleaning; 2. Wafer Cleaning; 3. Patterning/etching; and 4. Deposition. With

distinguish between the subcategories remote plasma cleaning and in situ cleaning. Within Wafer Cleaning category distinguish between the subca

Within Deposition category (N2O only) distinguish between the subcategories thermal and PECVD. There are two candidate Patterning/etching cat

Etch and Feature Etch. The process subcategories under the Film Etch alternative are: silicon, oxide, nitride and metal. The process subcategories 

are: Contact, SAC, Gate, Capacitor, Deep Trench, Isolation Trench, Regular Via, Through-silicon via and Metal etch. Select one subcategory from 

Etch categories and enter onto Data Form in the Subcategory and Alternative Subcategory spaces. Distinguishing between Film Etch and Feature E

3. SEMI will assign a separate letter for each entity that provides emission factor data. 4. Provide a brief explanation that supports using an alternative to ISMI Guidelines for characterizing process emissions. 5. Provide a brief explanation that supports the reliability of the reported emission factors despite not achieving the F mass balance target of >90% ma6. Ui denotes gas utilization, i.e., fraction of gas destroyed or transformed during the process step. Many etch recipes use multiple fluorinated GHG. 

those gases and the measured utilization of each. In this instance also note the convention adopted for reporting the by-product formation factor, Bip 

7. Bi denotes fraction of gas i transformed into other fluorinated GHGs such as CF4 formed from C2F6 or CHF3, C2F6 and C3F8 formed from other fl

product such as CF4 is formed in recipes containing multiple fluorinated GHGs (e.g., CHF3, c-C4F8 and C4F6) Bi, by convention, is the ratio of meof largest quantity of fluorinated GHG comprising the recipe.
Subpart I Technical Support Document 

November 2010 39

Appendix C – Evaluation of Uncertainty Associated with Alternative Emission Estimation 

Methods 

EPA examined estimates of semiconductor facility fluorinated GHG emissions obtained using alternative emissions 

estimation methods and one distribution of annual fluorinated GHG gas-usages for a hypothetical facility processing 300-

mm substrates that employing nine fluorinated GHGs. The five methods compared in this analysis were the: 

(1) IPCC Tier 2b, 

(2) Tier 2bM - emission factors modified/updated using the NODA Database, 

(3) EPA’s Tier 2c -five fluorinated GHG-using process types/sub-types consisting of three chamber 

cleaning sub-types, one wafer cleaning type and one aggregated etching type, 

(4) EPA’s Refined Method -the same cleaning sub-types as in Tier 2c but the single aggregated etching type 

is expanded to four film-based sub-types, and 

(5) a proxy for EPA’s Tier 2d -the same chamber and wafer cleaning types/sub-types as in Tier 2c but 

assuming as many groups of similar etching recipes as etching sub-types as there are for the Refined 

Method. 

For each alternative methodology, EPA compared the similarity between simulated emissions and the magnitudes of the 

spread in the 95 percent Confidence Interval (CI) of the relative error (RE) for the simulated emissions. This spread is the 

range in the probable error in emissions (PEE) and is calculated as the sum of the absolute value of the estimated lower 

bound of the RE and the corresponding upper bound. Higher PEE estimates mean higher uncertainties. In the absence of 

measured emissions, similar nominal emissions and PEE estimates are the only available measures of “goodness.” 

Methodologies and Sources of Information 

Plant Distribution of Fluorinated GHG Usage 

In this analysis one gas usage distribution comprised of nine fluorinated GHGs was used. This assumed plant distribution 

was based on one sample gas use distribution from a fabrication plant of indeterminate industry representativeness. The 

nine fluorinated GHGs in this analysis in decreasing usage rank order were: NF3, CF4, SF6, C2F6, C4F8, CH2F2, C5F8, CHF3

and C4F6. NF3 comprised 63 percent of total [mass basis] used for chamber and wafer cleaning, with 99.99 percent of total 

NF3 used for chamber cleaning. All of the NF3 used for chamber cleaning was assumed to be used in remote plasma 

cleaning. CF4 was used for etching and wafer cleaning [99 percent for etching]. The rest of the gases were used to etch 

oxide, nitride, silicon, and metal films. (Emissions of HTFs or N2O were ignored in this analysis.) 

Emission Factors and Relative Errors 

The IPCC Tier 2b emission factors (both utilization and by-product formation rates) that were used were taken directly 

from the 2006 IPCC Guidelines. The IPCC published 95 percent CI values for the emission factors were multiplied by two 

and converted to percent values to obtain relative errors for the IPCC Tier 2b emission factors. Emission factors (EFs) (both 

utilization and by-product formation rates) and REs for all other methods were developed using data in the NODA 

database. However, data was sparse for etching sub-types specifically, and the implementation of an analysis required EFs 

and their REs to be estimated by analogy to other gases in some instances. In cases where gas usage data was available, but 

a related EF was not available either in the IPCC or NODA database, EFs, and hence REs, were assigned by analogy based 

on the identical gas used in another process sub-type for which information was available. These analogies are presented in 

Table C-1 below. For the Tier 2d (proxy) method, because it was not feasible to estimate emissions for “similar recipes” 

specifically used at the hypothetical fab due to limited available data, EPA elected to estimate emissions for the Tier 2d 

method by modifying the REs for the four etching film-based sub-types used in the Refined Method analysis. The relative 

error for each the four etching sub-types for the Tier 2d method was assumed to be 20 percent. 
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Table C-1. Analogies Made for EFs and REs for Various Fluorinated GHGs for the Alternative 

Methodologies. 

Methodology Gas Process Sub-Type Analogous EF Analogous RE Other Notes 

EFs for Gas Utilization 

CF4 Metal Etch Average of Silicon Etch, Nitride 

Etch, and Oxide etch 

Oxide Etch 

CF4 Nitride Etch -- Oxide Etch 

c-C4F8 Nitride Etch Oxide Etch Oxide Etch 

SF6 Silicon Etch -- Average of all available 

REs for EFs in database 

SF6 Oxide Etch/ Nitride Etch Silicon Etch Average of all available 

REs for EFs in database 

C4F6 Nitride Etch Oxide Etch Oxide Etch 

CH2F2 Silicon Etch average of Oxide Etch and Nitride 

Etch 

Oxide Etch 

CH2F2 Nitride Etch -- Oxide Etch 

CHF3 Metal Etch/ Silicon Etch -- Average of Oxide Etch 

and Nitride Etch 

NF3 Ashing -- In-situ Plasma 

Refined Method 

C5F8 Oxide Etch c-C4F8 Oxide Etch c-C4F8 Oxide Etch See note 2.b 

SF6 Etch Silicon Etch Average of all available 

REs for EFs in database 

Tier 2bM C5F8 Etch c-C4F8 Etch c-C4F8 Etch See note 2.b/ The numbers for C4F8

Oxide Etch was assumed for the larger 

etch category 

SF6 Etch Silicon Etch 100% 

Tier 2c C5F8 Etch 0 0 See note 5 

NF3 Ashing -- 100% 

CF4 By-Product 

C4F6 Nitride Etch Oxide Etch Oxide Etch 

CH2F2

Silicon Etch average of oxide and nitride etch 

average of oxide and 

nitride etch 

C5F8 Oxide Etch C4F8 Oxide etch C4F8 Oxide etch 

CHF3

Silicon Etch/ Metal Etch average of oxide and nitride etch 

average of oxide and 

nitride etch 

Refined Method

NF3 Ashing In-situ plasma In-situ plasma 

Tier 2bM C5F8 Etch C4F8 etch C4F8 etch 

C5F8 Etch 0 0 See note 5 

Tier 2c NF3 In-situ Thermal -- 200% 

NF3 Ashing 0 0 See note 5 

C2F6 By-Product
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C4F8 Nitride Etch Oxide etch Oxide etch See note 2.b 

C5F8 Oxide Etch C4F8 Oxide etch C4F8 Oxide etch 

C4F6 Nitride Etch Oxide Etch Oxide Etch 

Refined Method

CHF3 Metal Etch/ Nitride Etch/ 

Silicon Etch Oxide Etch Oxide Etch 

Tier 2bM C5F8 Etch C4F8 etch C4F8 etch 

Tier 2c C5F8 Etch 0 0 See note 5 

Notes: 

1) – = Analogy not required 2) Analogies for process categories for each gas were made according to the following overarching steps: 

a. If, for a gas, an EF/RE did not exist for a sub-type under a specific process type, but existed for another process sub-type under 

the same process type, the EF/RE that existed for that one specific sub-type was assumed to be analogous for the sub-type with no 

existing EF/RE. (i.e., if an EF/RE for CF4 existed for nitride etch but not oxide etch, the EF/RE for CF4 for oxide etch was 

assumed to be analogous to the CF4 EF/RE for nitride etch.) If an EF or an RE for that gas category was missing, a proxy gas was 

used as an analogy for these estimates. Of note, Table 5 does not have any information for gas C5F8. Hence C4F8 was assumed as 

a proxy for all associated values. 

b. In the case of SF6, no such gas analogies could be made, therefore, an average of all REs for the gas distribution was used. 

3) Analogies for the overarching process categories of Tier 2c and Tier 2d methods were based on the analogies made for each individual 

gas and process category for the refined method. 

4) Additionally, where no EF information was available but gas utilization took place, the IPCC Tier 2b EF and RE were used in those 

rare instances. 

5) For the Tier 2c method only REs were assumed based on analogies, in situations where no emission actor existed for a given gas 

within the database, the related EF for calculations was assumed to be 0. 
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Type of Emissions Probability Distribution

A beta distribution was assumed for emissions of the gases and their by-products for practical and theoretical reasons. The 

beta probability distribution constrains the random variable (EFs in this work) in each trial to values between 0 and 1. 

Alternatives to the beta distribution—normal, lognormal or gamma—would permit trial EFs that are physically impossible, 

i.e., EFs that could be negative or greater than one (depending on which of those three distributions were used in a 

simulation), which would require truncating negative values or values greater than one. The number of EFs in the NODA 

database for any gas and process type/sub-type was insufficient to test the appropriateness of the beta distribution. 

Parameters for the beta distribution were estimated using information from the 2006 IPCC Guidelines and using the mean 

and REs estimated from the May 2010 NODA information, as appropriate. 

Location and shape parameters of the beta distributions were estimated for each emissions estimation method using the 

corresponding means and variances from either IPCC tables (converting the IPCC reported 95 percent CI value to a 

percentage and multiplying by two to obtain REs for the fluorinated GHGs) or the NODA database. EFs for all gases 

utilized were constrained between 0 and 1, but the by-product emissions were constrained between 0 and the highest value 

for that specific gas and process type available in the NODA database. 

Uncertainty Analysis using @RISK 

Monte Carlo simulations were performed for each of the five methods using @Risk software and beta distributions to 

characterize the variability in EFs. Through @Risk, 10,000 iterations were completed for each simulation. The results of 

these trials provided estimates of the mean of simulated emissions, and the corresponding upper and lower bound 

confidence intervals (95 percent) in emissions, and, therefore, PEE estimates, for each of the five methods. 

Results

Estimating “Goodness” of Calculated Emissions: 

This analysis adopted two measures of goodness: (1) the inter-comparability of nominal emissions for the IPCC Tier 2b, 

Tier 2bM, Tier 2c, Refined, and Tier 2d methods (i.e., the similarity of emissions calculated using, for the single 

distribution of fluorinated GHG usage, the total emissions [MMTCE]), and (2) variability in the corresponding nominal 

emissions for each method as measured by the 95 percent CI. The PEE is used for comparing the variability in reported 

emissions among methods, because the PEE—a single number— is more convenient than using two numbers, the lower 

and upper bound of the 95 percent CI of the RE. 

Results in detail 

The outcome of an uncertainty analysis such as this one may presume that the simulation for each method employed (a) 

robust estimates for emissions factors and reasonable estimates for the variability in those factors for each gas used and 

each fluorinated GHG-using process type/sub-type, and (b) a distribution representative of fluorinated GHG usage in 

semiconductor manufacturing. However, those presumptions don’t hold in this analysis as it relies on a paucity of available 

EF data and only one fluorinated GHG usage distribution whose representativeness is unknown. Therefore, how much 

weight should be given to the observations below is affected by the concerns about the scarcity of available EF and gas 

usage information. 

Nominal and simulated mean emissions for the IPCC Tier 2b, Tier 2bM, Tier 2c, Refined, and Tier 2d methods are shown 

in Table C-2 below. This table also illustrates the PEE for each methodology. All the PEE values have been normalized to 

Tier 2b PEE for ease of comparison. 

Table C-2. Comparison of nominal and simulated mean emissions (MMTCE) and normalized estimates of PEE for 

five alternative emission estimation methods 

 Simulated results after 10,000 iterations with @Risk 

Method Nominal emissions 

(MMTCE) 

Mean Emissions 

(MMTCE) 

Normalized spread in 95% 

CI of RE or PEE 

Tier 2b 0.011 0.011 1 

Tier 2bM 0.014 0.014 1.72 
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Tier 2c 0.014 0.014 1.68 

Refined Method 0.014 0.014 1.88 

Proxy Tier 2d 0.014 0.014 1.39 

As shown in Table C-2,the nominal and simulated emissions are equivalent at up to two significant figures for all the 

alternative methods evaluated. This supports EPA’s use of a beta distribution to quantify variability in EFs for this 

uncertainty analysis. 

Inter-comparability of Emission Estimates:

The results (to two significant figures) provided in Table C-2 show that total nominal emissions obtained using the IPCC 

Tier 2b method are understated. All of the emission estimates from the other four methods are the same (up to two 

significant figures); with emissions being 27 percent higher than the corresponding emissions estimated using IPCC Tier 2b 

method (0.014 MMTCE for each of the four updated alternatives vs. 0.011 MMTCE for Tier 2b method). Conversely, Tier 

2b emissions are understated by approximately 21 percent relative to the methods based on updated EFs. 

Variability of Nominal Emissions/PEE:

The methods vary in their respective probability distribution spreads around the mean as shown by the normalized PEEs 

presented in Table C-2. Results show that the PEEs for the Tier 2bM, Tier 2c, Refined and proxy Tier 2d methods are 

greater relative to the PEE for the IPCC Tier 2b method. Of the non-IPCC methods evaluated, the PEE for the proxy Tier 

2d method is the lowest, but as noted prior it is higher than the PEE for the IPCC Tier 2b method (see Table C-2). Based on 

this analysis, the IPCC Tier 2b method appears to produce an understated, but the most precise, estimate with the proxy 

Tier 2d method being a close second in precision. 

It is noteworthy that the higher emissions and variability, calculated for the updated methods compared to the IPCC Tier 2b 

method for the distribution of gas usage used, appears to be attributable to higher CF4 by-product formation EFs and REs 

for the updated methods compared to the IPCC Tier 2b method. For instance, the CF4 by-product formation EF for NF3

remote plasma clean for the Tier 2bM is twice as large as the corresponding EF for the IPCC Tier 2b. Similarly, the CF4

by-product formation RE for the Tier 2bM exceeds the corresponding RE for the IPCC Tier 2b by a factor of 7.2 for NF3

RPS. It seems that the updated EF information contained in the NODA reflects the increased recent manufacturing trend of 

using carbon-based low-k dielectrics. This increased use of C-films would be expected to lead to higher EFs in both etching 

and chamber cleaning due to reaction of carbon with F-atoms to form CF4. Further, the greater REs in EFs developed from 

the NODA database may be attributable to increase variability in both etching recipes and film C-content that is reflected in 

the NODA database. Without more information regarding the EF data and gas usages this explanation cannot be explored. 

Findings and Conclusions

The results of comparing the PEEs for all methods are both unexpected and expected. On the one hand, these results are 

unexpected because one anticipates, in principle, that, as the information used to develop EFs improves and as a method’s 

comminution increases, simulated estimates of PEE would decrease. Therefore, in moving from the IPCC Tier 2b to the 

Proxy Tier 2d method, the normalized estimates of PEEs should decrease, corresponding to a reduction in uncertainty. On 

the other hand, that outcome presumes that each simulation employed (a) robust estimates for emissions factors and 

reasonable estimates for the variability in those factors for each gas used and each fluorinated GHG-using technology, and 

(b) a distribution representative of fluorinated GHG usage in semiconductor manufacturing. Because these presumptions 

don’t hold—the analysis instead relies on a paucity of available EF data and only one fluorinated GHG usage distribution 

whose representativeness is unknown—the balance tips toward the unexpected. That there is a reduction in the spread of 

estimates of PEEs from the Refined Method to the proxy Tier 2d method seems noteworthy (see Table C-2). However, how 

much weight should be given to this observation is affected by the concerns regarding the paucity of available EF and gas 

usage information mentioned earlier. 

Despite the ambiguity in these results, they do point to two reasons for moving away from the IPCC Tier 2b method: (a) 

emissions estimated with the IPCC Tier 2b methods are understated, and (b) there is a void in facility-level, emissionsrelevant information and a need to revise the IPCC Tier 2b EFs. The results of this evaluation also show that moving from 

the use of a default factor(s) for etch sub-types to the use of recipe-specific measurements appears to increase certainty in 

emission calculations. 
Subpart I Technical Support Document 

November 2010 44

More facility-level, emissions-relevant information would permit an uncertainty analysis to be performed with more 

meaningful and robust results. However, additional information about facility-level gas usage and EFs is needed before one 

can have confidence in facility-level reported emissions. While using properly weighted default EFs would yield reliable 

estimates of total U. S. emissions from semiconductor manufacturing, considerable uncertainty in facility-level emissions 

would remain. 

Given the lack of available facility-level gas usage and emission information, particularly for the etching process type, as 

made apparent by this analysis, EPA is requiring that larger facilities report EFs for etching technologies and use verified 

gas apportioning models. 
Subpart I Technical Support Document 

November 2010 45

Appendix D - Support for EPA’s Definition of Similar Recipe 

Accurately tracking fluorinated greenhouse gas (fluorinated GHG) emissions during semiconductor manufacturing 

is a complex endeavor. Out of as many as seven hundred or so distinctly different manufacturing steps required to 

simultaneously produce as many as 500 electronic devices or so on a single substrate, which are completed within 

the course of approximately a month, many of those steps use as many as six fluorinated GHGs, either alone or in 

various combinations for plasma etching. (Boyd et al., 2009; Linx-consulting, 2010) 

Estimating annual facility-level fluorinated GHG emissions can be simplified by grouping manufacturing steps into 

process types or sub-types and using emission factors within each type or sub-type Accuracy in a facility’s annual 

estimate of emissions would be maintained with this approach provided the variability in the factors that govern 

emissions across each process type or sub-type is sufficiently small and, ideally, random. 

For purposes of estimating and reporting facility-level fluorinated GHG emissions, EPA defines three process 

types—chamber cleaning, wafer cleaning and etching. The chamber cleaning type is further subdivided into three 

process sub-types: in situ plasma, remote plasma and in situ thermal. For each sub-type, EPA developed default 

emission factors—figures for gas utilization and by-product formation, as appropriate—for each gas that all facilities 

may use. 

EPA provides no process sub-types for (plasma) etching. EPA differentiates, for this process type only, the 

emissions calculating and reporting requirements for large and other semiconductor manufacturing facilities. For 

other semiconductor facilities, EPA developed a default emission factor for each gas that may be used to estimate 

and to report emissions for plasma etching. For large facilities, EPA requires that, for each gas used, facilities 

measure and report emission factors for each plasma etching recipe, that is not included in a set of similar recipes, as 

well as to report facility-level emissions for each of the recipes. Because there may be scores of plasma etching 

recipes used during device manufacture EPA expects grouping similar recipes will simplify and reduce the burden 

of emissions reporting with but a relatively small effect on the overall accuracy of reported facility-level emissions. 

For recipes and associated gases that meet EPA’s definition of similar recipe, a large facility may measure the 

emission factor(s) for one of those recipes, as well as report, using the measured emission factors, the corresponding 

emissions associated with gases used in those similar recipes. 

This appendix provides technical support for EPA’s definition of “similar recipe”. The appendix begins with a brief 

description—a primer—of the physics and chemistry that govern fluorinated GHG-based plasma etching during 

semiconductor manufacture. This discussion serves two purposes: (1) to identify the experimental parameters that 

govern current practice of fluorinated GHG plasma etching, and (2) to bring into clear view the influence that 

variations in those parameters have on etch efficacy. Following this primer is a summary of the parameters that 

define plasma-etching practices during semiconductor manufacturing and, therefore, that potentially influence the 

concomitant fluorinated GHG emissions. The appendix then turns to a review of publicly available studies that 

investigate fluorinated GHG emissions as functions of those plasma-etching parameters. The appendix concludes 

with a definition for similar recipes, a definition that specifies the parameters as well as allowable ranges in those 

parameters—an allowable parameter space. EPA expects increases or decreases in these parameters within the 

specified ranges that define this space would result in acceptably small emission increases or decreases. 

Plasma Etching— A Primer

In semiconductor manufacturing, plasma etching practice is predominantly empirical, augmented by rules-of-thumb 

and heuristics. As Hills and Cook (2000) state, “The complexity encountered in actual processing requires much 

more information than is available experimentally or that can be derived by even the most complex calculations...A 

practical plasma etching process involves interacting factors or species production and control in the gas phase, a 

multitude of chemical pathways inherent to the complexity of the molecules used, many poorly understood 

interactions with the complex (and ‘dirty’) wafer surfaces and many device structure specifics...Plasma chemistries 

are thus chosen by a combination of experience, first principles and to some extent empirical ‘lore’.” 

A phenomenological discussion is sufficient to establish a relationship between etching, emissions and controllable 

process parameters. In what follows, only as much of the physics and chemistry as needed is presented: the 

boundary is chosen in order to frame EPA’s definition of similar recipes. 

Plasma etching—specifically reactive ion etch (RIE), also called dry etch, is most simply defined as “the removal of 

material from a wafer surface with gaseous reactants to produce gaseous products, which are then pumped away and 
Subpart I Technical Support Document 

November 2010 46 

appropriately disposed” (Hills and Cook, 2000). The objective of dry etching is to reproducibly produce a pattern 

into a substrate with certain precision, across a substrate and from one substrate to the next. RIE takes place in 

specifically designed reactors, of many designs, into which reactants flow, substrates are placed, and power is 

supplied (to sustain the plasma).51 The scholarly and patent literature show that developing practical plasma etching 

recipes involves, for a given reactor design, experimentally identifying the reactor pressure, reactant composition 

and flow rate, and power that produces suitable etch rates, feature dimension and profile, selectivity, etc. RIE is 

characterized by two concurring phenomena: physical sputtering and chemical reaction, which result, to varying 

degrees, material selectivity52 and etch anisotropy (directionality). 

Figure D-1. RIE Etching showing (a) sputtering, (b) chemical etching and (c) sputtering and chemical etching. 

Top (dark layer) is mask and lower layer is material being removed (etched) 

Figure D-1 illustrates these two concurring phenomena; it also shows how the image of a mask is reproducibly 

transferred into the film (substrate). Physical sputtering describes the dislodging of material, which occurs when 

sufficiently energetic but chemically inert ions hit a surface and “kick out” atoms or molecular fragments. As the 

momentum carried by particles transfers energy to surface atoms (which is generally most effective under an angle 

of ≈60o

 measured from vertical), material removal leads to positively inclined sidewalls. Sputtering also erodes the 

photoresist mask (See Figure D-1a) (Rossnagel, 2000). 

Chemical etching results from reactive species created in the plasma, formed from a mixture of gaseous materials 

that breakdown into reactive components. These reactants form volatile products upon reacting with the substrate 

material. Reactants are chosen in part for their selectivity to either not react with the mask material or react at a 

much slower rate than with the underlying substrate. Chemical etching, however, is isotropic (multidirectional) and, 

without counterbalancing effects, results in under-etching and rounded profiles (See Figure D-1 b) (Hills and Cook, 

2000). 

Balanced physical and chemical material removal leads to vertical etch profiles. Additionally, in situ chemistry leads 

to formation of sidewall passivation layers, which achieves etch directionality. Chemically formed, etch-inhibiting 

films (e.g., polymer, oxide, etc.) occur on the sidewalls but not on horizontal surfaces where they are continuously 

removed by ion-bombardment (See Figure D-1 c) (Hills and Cook, 2000). 

Etching reagents include fully fluorinated carbon- or non-carbon-containing compounds (e.g., CF4, C2F2, C2F4, C2F6, 

C3F8, C4F6, C4F8, C5F8, SF6, NF3, BF3) and hydrofluorocarbon compounds (e.g., CHF3, CH3F, CH2F2, C2H2F2). 

Characterizing Fluorocompound RIE Processes Using the Film SiNx Example 

Plasma etching of Si, SiO2, SiNx films, for example, with fluorocarbon and hydrofluorocabon gases is well studied 

(Oehrlein,1990; Lehman and Widmer,1978; Booth, 1999; and Standaert, et al., 2004, Lieberman and Lichtenberg, 

2005). Argon appears to be a preferred diluent gas. To achieve the proper etch characteristics (e.g., etch rates, 

 

51 Because of the numerous loss processes that occur during plasma etching, plasmas are not self-sustaining and therefore, to 

achieve steady-state, require continuous power input, in the form of high frequency electromagnetic energy. In semiconductor 

manufacturing, the electromagnetic radiation is in the radio frequency (RF) spectral region. For simplicity of discussion, the term 

power is used in this report rather than RF power. 

52 Etch selectivity measures the differential etching between photoresist material and silicon-based film. The photoresist forms 

the pattern to be transferred to the substrate via the etching process (Garza et al., 2000).
Subpart I Technical Support Document 

November 2010 47 

verticality, selectivity, uniformity, critical dimension (CD) control, to name an important few53) additives such as 

O2, H2 or N2 are common and patent literature points to the use of H2O2, CO, CO2 and perhaps N2O (Zhu et al., 

2005). 

 While Kushner and co-workers have successfully modeled the chemical and physical factors that govern etch rates 

for relatively simple systems such as C2F6 (Zhang and Kushner 1999, 2000a, 2000b) that success falters with C4F8

(Sankaran, A., A. Vasenkov and M. J. Kushner, 2002). A brief description of the well-studied combination of the 

SiNx-PMMA (polymethylmethacrylate, resist) combination will illustrate this complexity. 

In CF4 or CHF3 plasma, F atoms and CFx (x = 1-3) radicals as well as ions, formed by the transfer of the kinetic 

energy of electrons to reactants, are generated and transported to the substrate surface via diffusive processes or 

accelerated by the electric field of the DC bias applied to the power electrode of the RF plasma. (The DC bias 

improves directionality but if too high can result in unwanted increase in substrate temperature, so the DC-bias 

usually remains fixed; chillers are used to control the substrate temperature.)54 

Higher reactor pressure may increase or reduce the dissociation (emissions and etch rate) of CF4 into CF3, CF2, CF 

and F. Higher reactor pressure means higher reactor gas density and therefore increased dissociation (but perhaps 

lower by-product formation depending on the dominant etching reactant). The etch rate, however may drop because 

the increased rate of polymer (CxFy) formation (vide infra).55 Decreasing pressure leads to a decrease in ion 

scattering (ion energy is lost through collisions) leading to higher ion bombardment energies, and, in turn, higher 

physical etching. 

Changes in reactant flow rate affect etching rate and emissions depending on reactor conditions. Under very low 

flow rates, increasing flow increases etching rate and emissions because reaction rates are limited by the supply of 

reactants. In this regime, increasing the flow rate would increase etching and emissions. At flows above the reactantsupply-limited regime, reaction rates are limited by the reaction time compared to the reactor residence time. 

Shortening the residence time (by increasing the flow rate) compared to the reaction time would decrease etching 

rate and emissions. Increasing the residence time (by decreasing flow rate) would increase etching rate and 

emissions. 

As previously noted, etching rate is the net of competing physical and chemical phenomena. Gas phase 

oligomerization of CFx radical results in large CxFy molecule formation (Booth, 1999), which forms a fluorocarbon 

polymer film on all surfaces (Standaert et al., 2004). The main etchant of SiNx is the F atom (Li et al., 1995). 

Volatile etch products (SiFx, CNF, NO, N2) are generated and pumped away (See Figure D-2). Formed CxFy is 

removed by etching and bombardment leading to reformation of CF4 (or by-product CF4 formation when the virgin 

etchant is only CHF3). 

 

53 It will become evident later in this report that fluorinated GHG emissions have not been a major consideration when 

characterizing the manufacturability of plasma etching processes. 

54 A sufficiently high DC voltage assures net transport of positive ions to the surface of the substrate. 

55 By-product formation and polymer formation may be reduced because both are second order in reactants resulting in 

formation rates changing in proportion to the square of reactant gas densities.
Subpart I Technical Support Document 

November 2010 48 

Figure D-2. Illustration of physical and chemical processes and interactions during CF4 plasma etching of 

SiNx film 

Much of this complex chemistry can be qualitatively explained by the F-to-C ratio (F/C), where a larger ratio favors 

etching and a smaller ratio favors CxFy formation/deposition (Miyata et al., 1997). The balance between polymer 

formation and etching also shifts with other process parameters such as pressure and power, although higher power 

adversely affects etching selectivity via photoresist removal due to increased ion bombardment. In general, it 

appears that increasing pressure favors CxFy formation and more intense ion bombardment (power) favors CxFy

formation, and concomitantly, SiNx etching (Dulak et al., 1991), albeit with lower selectivity (vide supra). Recently, 

Rabilland et al. (2007) provided additional evidence that supports this mechanism for Si, SiCH, SiO2 and SiOCH 

films using pulsed plasma. 

Adding O2, H2 or N2 gases can achieve some fine control of the chemical aspects of the etching characteristics of 

fluorocarbon plasmas: 

• H2 extracts fluorine atoms from the plasma via the reaction (H+F→HF),which suppresses SiNx etching and 

CxFy formation (Oehrlein, 1990) 

• O2 scavenges H and carbon (H+O →OH ad C+xO→COx), which suppresses CxFy formation and increases F, 

which, in turn, increases SiNx etching (Oehrlein, 1990)56

• CO scavenges F (CO+xF→COFx), which enhances polymer formation and suppresses etching (Zhu et al., 2005) 

• Argon and N2 principally cause more intense ion bombardment and a dilution of CFx radicals, both resulting in 

thinner CxFy layers and therefore enhanced SiNx etching. N2 is also responsible for promoting the etch rate 

enhancing the reaction (2N +2 SiN → 2Si +2N2) (Li et al., 1995) 

If CHF3 were used with or instead of CF4, the affect of hydrogen on etch rate comes with the etchant, which would 

lower the F/C ratio relative to a pure CF4 plasma. If required, the etch rate could be adjusted upward by adding a 

small amount of O2 to the gas composition, which would lower H via the H+O→OH reaction. 

 

56 See also Reid and Hughes (2007) who demonstrate a similar effect of increasing O2 flow on plasma etching of carbon doped 

ultra-low-k dielectric layers. 
Subpart I Technical Support Document 

November 2010 49 

The description of this relatively simple etching chemistry provides a qualitative model for the chemistry for more 

complex molecules. A principle difference between CF4 and, say, C2F6 system, is by-product formation: CF4 is 

formed when C2F6 is the etchant. CF4 formation is postulated to be the result of the branching reaction 

 C2F6 + e- → C2F5 + F + e-

 C2F6 + e- → CF3 + F + e-

 

where the latter leads to CF4 formation by recombination of CF3 and F. It is the exponential increase in these 

branching reactions that rapidly complicates the chemistry of etchants like C3F8, C4F8, etc. (Sankaran, Vasanov and 

Kushner, 2002). 

Another essential feature of plasma etching is allowance for flow stabilization. Patent literature (see, for example, 

Hudson and Tietz, 2005) and EPA experience (EPA, 2008) indicates plasma etching processes allow for periods of 

<1 second to a few seconds to assure pressure and flows are stable and uniform prior to striking plasma. Because 

there is no destruction of fluorinated GHG during this period, which can represent a consequential fraction of total 

process time and, therefore, a substantial part of total emissions for plasma-etching recipes when fluorinated GHG 

destruction is high (plasma on), this flow stabilization time is also an essential feature of a plasma etch recipe and, in 

turn, included in EPA’s definition of a similar recipe. EPA has demonstrated that because correcting measured 

emissions for changing recipe time can be made, only stabilization time and not total etching time is relevant when 

defining similar recipes. 

A Precise Definition for Similar Recipes: Defining the Parameter Space for the Purpose of Estimating and 

Reporting Emissions

As illustrated in the plasma etching primer, the parameters that equipment and electronic device manufacturers 

manipulate to achieve commercially successful plasma etching recipes are power, reactor pressure, chemical 

composition, constituent flow rates and flow stabilization time. Anecdotal reports indicate that device manufacturers 

manipulate these parameters for a variety of reasons and in degrees that are understandably proprietary when 

developing the manufacturing process steps for a specific electronic device. These, then, are the parameters EPA 

considered in formulating a definition for similar recipes. 

EPA unsuccessfully searched publicly available literature for studies that examined the influence of variations in 

these process parameters on fluorinated GHG emissions. What emerged were studies on how variations in plasmaetch parameters influence manufacturing benchmarks such as etch rate and etch selectivity as well as dimensional 

control and uniformity across a surface film of an etch feature. EPA did not identify published studies of fluorinated 

GHG utilization or fluorinated GHG by-product formation, expressed as functions of plasma etching process 

variables (vide supra). 57

Precisely defining “similar recipe” for plasma etching presents challenges because of the absence of published 

studies of fluorinated GHG emissions as functions of the required process parameters (vide supra). EPA met this 

challenge by recognizing the parallel between plasma etching, which selectively removes portions of a film in order 

to transfer a pattern to a substrate, and plasma cleaning, which uniformly removes unwanted film that had been 

previously and unavoidably deposited on chamber walls. In situ plasma chamber cleaning relies on the same physics 

and chemistry that produces precise features (which was described in the previous section) to remove (etch-away) 

undesirable silicon-containing films from chemical reactor surfaces following the chemical deposition of films on 

substrates. 

The practical parallels between plasma patterning and plasma cleaning are many. Both are driven by entangled 

productivity and performance objectives. Manufacturing productivity—substrate throughput—means film etch rate 

is an important benchmark in both substrate patterning and chamber cleaning; manufacturers relentlessly pursue 

increasing substrate processing rates. Performance—device functionality and yield—means feature and defect 

control are important benchmarks in both substrate patterning and chamber cleaning. Reactor pressures, chemical 

 

57 This is not an argument for manufactures’ ignoring emissions of fluorinated GHGs with high GWPs when developing plasma 

etch processes. Considerable work has been expended in searching for alternative gases and chemistries, with some success 

(Johnson et al., 2004). While celebrating these successes is not the main purpose of this report, the industry’s increasing adoption 

of CH2F2, C4F6 and C5F8, each having lower emissions per unit of input gas (albeit somewhat offset by CxHyFz by-product 

formation) as well as lower GWPs, has lowered CO2e emissions compared to alternatives like, for example, CF4, CHF3 and C2F6

(ISMI, 2005). 
Subpart I Technical Support Document 

November 2010 50 

composition, flow rate and power affect achieving these objectives. While reactor pressures and flow rates differ in 

plasma etching and plasma cleaning recipes, the differences can be explained, in large part, by differences in surface 

area (substrate area being patterned is much smaller, requiring smaller flows, than reactor surface area being 

cleaned, requiring higher flows) and reactor design (high density, lower pressure reactors for patterning vs. low 

density, higher pressure for chamber cleaning). While plasma etch patterning seeks anisotropy chamber cleaning 

seeks isotropy; both can be controlled by the addition of oxygen (higher oxygen decreases polymer formation, which 

improves the efficacy of chamber cleaning and substrate patterning).58 Both plasma patterning and chamber cleaning 

recipes also seek to limit ion bombardment because in plasma patterning ion bombardment reduces selectivity and 

increases substrate temperature (vide supra) and in chamber cleaning it increases the damage to reactor surfaces. 

These parallels between plasma cleaning and plasma patterning together with consideration of the basic physics and 

chemistry that govern plasma cleaning and plasma patterning, suggest that studies that provide information on 

fluorinated GHG emissions when parameters of in situ plasma chamber cleaning recipes are varied can inform 

EPA’s considerations about how fluorinated GHG emissions might change were those same parameters varied in 

plasma etching recipes. 

EPA’s search of the publicly available in situ plasma chamber cleaning literature identified three studies with 

sufficient information to estimate the effect that changes in recipe parameters have on emissions. These were 

optimization studies in which the authors identified the conditions (pressure and flow rate for example) that, for the 

same cleaning time, resulted in lower emissions and usually lower gas usage. The three studies involved different 

films and three different recipes: C2F6/O2 (Daniels and Cheng, 1998), NF3 (Bing et al., 2003) and C3F8 with O2 or 

N2O (Kesari et al., 1999). These fluorinated GHGs are also used in plasma etching. Changes in emissions were 

reported in terms of absolute emissions (e.g., kg carbon equivalent, fluorinated GHG utilization, or both). 

C2F6/O2: Daniels and Cheng (1998) 

It appears Daniels and Cheng (1998) were the first to report optimizing a popular C2F6/O2 chamber cleaning process 

for fluorinated GHG emissions. Their study sought identification of the conditions that would give the lowest C2F6

emissions for the shortest chamber-cleaning time. Daniels and Cheng reported that Applied Materials (AMAT’s) 

standard process at the time was 600 sscm of C2F6 and O2, 4 torr reactor pressure and 1000 watts power. By 

increasing the reactor pressure to 6 torr (a 33 percent increase) and reducing the C2F6 flow rate to 550 sccm (an 8.3 

percent decrease) while keeping the C2F6:O2 ratio 1, Daniels and Cheng reported a 35 percent reduction in C2F6

emissions and a 5 percent reduction in chamber-cleaning time. 

Daniels and Cheng provide data that permits estimation of the changes in C2F6 emissions from separate changes in 

reactor pressure and C2F6 flow rate. The data given Figure D-3 of this appendix, which is adopted from Daniels and 

Cheng’s Figure 3, shows that a +10 percent change in pressure—from 4 torr to 4.4 torr—results in a 2.3 percent 

reduction in C2F6 emissions. Four torr is chosen because it was the pressure for AMAT’s (best known) process (vide 

supra). Four torr was also the lowest pressure for which Daniel and Cheng reported emissions (Their studies showed 

that lower pressures would increase emissions and clean times which was counter to their aim.). The authors, 

however, do provide data for 5 torr. For a 10 percent reduction in pressure (5 torr to 4.5 torr) C2F6 emissions 

increased 5 percent. 

 

58 Note also that adding oxygen to in situ plasma chamber cleaning recipes decreases the occurrence of particles that can 

interfere with waste stream management.
Subpart I Technical Support Document 

November 2010 51 

Figure D-3. C2F6 Emissions vs C2F6 Inlet Flow Rate & Pressure at 1:1 Oxygen:C2F6 Ratio (Extracted from 

Daniels and Cheng, 1998) 

A similar analysis for C2F6 flow rates follows from the authors’ data provided in Figure D-3. For a 10 percent 

increase in C2F6 flow (from the flow of 600 sccm for the best known method [BKM] to 660 sscm) Daniels and 

Cheng observed a 4.8 percent increase in C2F6 emissions while a 10 percent decrease in the BKM flow rate 

produced a 7.9 decrease in C2F6 emissions. The authors did not vary power as the BKM chamber cleaning process 

called for the highest power setting on the AMAT 5200 DCVD Centura. 

Other authors (See Sistern et al., 2004 and references therein) report process optimization studies that result in 

reducing emissions and chamber-cleaning times for C2F6/O2 process (as well as for C3F8 and C4F8). However, those 

studies do not report experimental details. The summary results reported by Sistern et al. (2004) for C2F6/O2

chamber cleaning process are very similar if not identical to those reported by Daniels and Cheng (1998). Sistern et 

al. (2004) use FTIR and QMS methods for quantifying emissions while Daniels and Cheng (1998) used only QMS. 

NF3: Bing et al. (2003) 

Bing et al. (2003) studied optimization of NF3 in situ PECVD chamber cleaning. Using a design of experiment 

methodology, Bing et al. observed NF3 emissions for a range of operating parameters: chamber/reactor pressure (2 – 

4 torr), NF3 flow rate (200 – 350 sccm), and NF3 fraction in the diluent gas (11.5 – 14.5 mole-percent). Power was 

fixed at 950 W. Similar to the work of Daniels and Cheng (1998), Bing et al. (2003) showed that, over this range in 

process parameters, there’s a trade-off between cleaning times and NF3 emissions. Shorter cleaning times are 

economically beneficial because more equipment time is available for wafer processing, which cannot occur during 

chamber cleaning. 

Bing et al. (2003) provide results for both emissions (kgCE) and gas utilization (U). Table D-1summarizes their 

results. The percentage changes in NF3 emission are given for a range percent change in each process variable that 

EPA incorporates in its definition of similar recipe. Examination of the information presented in Table D-1 shows 

that, in general, a change of ±10 percent around the process variables that define the BKM results in a corresponding 

change of 10 percent or less in fluorinated GHG emissions. 
Subpart I Technical Support Document 

November 2010 52 

Table D-1. Changes in NF3 emissions (kgCE) and utilization for various indicated changes in parameters for 

in situ chamber-cleaning process 

Variable 

Name Nominal value for 

BKM, except as noted1 

Change, %, except as 

noted 

Emissions, % change in kgCE, 

except as noted 

+10 +3.62 

Pressure, torr 3 

-10 -4.62 

+10 -4.62 

NF3, mole% 13 

-10 +10.12 

+22 (Faster clean) 0.91 kgCE3

NF3 flow, sccm 300 (Balanced) 

-17 (Lower emissions) 0.29 kgCE3 

Faster clean 0.79 kgCE4 (-8.1% from balanced) Utilization, 

dimensionless 0.86 (Balanced) 

Lower emissions 0.94 kgCE4

 (+9.3% from balanced) 

Notes: 

1

 BKM denotes best-known method. 

2

 Values estimated from Fig. 10 of Bing et al. (2003). 3

 Values taken from Table 6 of Bing et al. (2003); 0.91 kgCE represents an increase of 69 percent in kgCE compared to 0.54 

kgCE, what Bing et al. call the balanced process vs. 0.29 kgCE, which represents a decrease of 46 percent in kgCE 

compared to balanced process (0.54 kgCE). 

4

 Values taken from Bing et al. (2003) Table 6. These values denote NF3 utilization, which Bing et al. call NF3 destruction 

efficiency. 

C3F8/O2/N2O: Kesari et al. (1999) 

Kesari et al. (1999) reported results from studies that examined optimization of in situ C3F8 chamber cleaning 

processes for several kinds of films. These are the only reported results found for the affect of changing O2 and N2O 

flow on fluorinated GHG utilization (for two film types, nitride and oxide). Kesari et al. also provide results of CF4

formation as a function of O2 flow when cleaning oxide-coated chambers. 

The results from Kesari et al. are summarized in Table D-2. It is evident that, for ±10 percent change in nominal 

process flow, the corresponding changes in emissions parameters range from 3.3 to 12.8 percent. Kesari et al. did 

not offer explanations for why C3F8 utilization and CF4 formation rates decreased when either N2O or O2 flows were 

increased or why CF4 product formation decreased, in the case of oxide film removal, when the O2 flow was 

increased. The average change in the nominal emission parameter reported by Kesari et al., disregarding the sign, is 

8.3 percent for a ±10 percent changes in O2 or N2O flow rates. 

Table D-2. Affect of ±10 percent changes in O2 and N2O flow rates on C3F8 utilization and CF4 by-product 

formation during nitride and oxide in situ plasma chamber cleaning. 

Process Process parameter Emission parameter 

 Name Nominal value Change, % Name Change, % 

Nitride film N2O flow rate 400 sscm +10 Gas utilization1 +6.3 
Subpart I Technical Support Document 

November 2010 53 

-10 -12.8 

+10 -3.3 

-10 

Gas utilization2 

+3.3 

+10 -12 

Oxide film O2 flow rate 450 sscm 

-10 

CF4 formation3 

+12 

Note 1. Nominal C3F8 utilization for nitride film chamber clean = 0.47 

 2. Nominal C3F8 utilization for oxide film chamber clean = 0.60 

 3. Nominal CF4 formation per clean = 0.25 grams 

Each of these studies indicates that changes in pressure, flow rate and relative chemical composition of ±10 percent 

produces changes in emissions of the order of 10 percent. The results of Bing et al. (2003) and of Daniels and 

Cheng (1998) also shed light on the magnitude of emissions changes from changes in process parameters greater 

than 10 percent. Their results point to nonlinear relationship between fluorinated GHG emissions and variations in 

process parameters. The results of Bing et al. (2003), for example, show that substantial reductions in emissions can 

result from optimizing chamber-cleaning processes. This suggests EPA’s definition of similar recipes should not 

permit changes in process parameters beyond 10 percent. 

Summary and Conclusions

EPA’s review of plasma etching practices during semiconductor manufacturing revealed both the complexity of dry 

etching processes and the parameter space that govern today’s commercial success and fluorinated GHG emissions. 

EPA’s review also revealed an absence of publicly available information about the influence of plasma etching 

process parameters on fluorinated GHG emissions for commercially efficacious plasma etching recipes. This 

absence, while restricting the scope of EPA’s review, did not restrict its ability to develop a practical definition for 

similar recipes. To overcome this information gap and to identify the parameters for a practical definition of similar 

recipes, EPA used an analogy between (in situ) plasma etching and in situ plasma chamber cleaning. 

EPA’s review confirmed that what influences commercial performance of RIE plasma etching processes is power, 

DC bias, reactor pressure, chemical composition and flow rate(s). All of these parameters except DC bias influence 

fluorinated GHG emissions.59

EPA’s review of three experimental studies of optimizing in situ plasma chamber cleaning showed that changes of 

the order of 10 percent in reactor pressure, reactant flow rates and relative chemical composition resulted in 

observed changes in emissions (including emissions of by-products) and gas utilization of the order of 10 percent or 

less. All of the studies reviewed suggested that changing power would influence emissions but none explicitly 

presented results. The one study (Liu et al. 2000) that reported measuring the influence on power noted, while not 

reporting specific measurements, that the optimized recipe conditions “were observed using similar power...as the 

original manufacturing recipe.” This result suggests that changing power is of lesser importance than changes in 

other parameters in improving recipe performance.60

EPA interprets the results of its review as supporting a definition of similar recipe provided that definition does not 

allow for changes in either the chemical composition and allows changes in power, reactor pressure, gaseous flow 

 

59 The DC bias contributes to the removal of material via sputtering, which appears to comprise solid particles rather than 

gaseous particles. In this manner fluorinated GHG emissions are not affected by changing DC bias. In certain instances if those

particles contain carbon, CF4 might be formed. However, even if this mode for forming CF4 were occurring in some instances, 

CF4 emissions would not change except in response to a change in DC bias, which appears not be a prevalent practice. 

60 Note also that the largest change in power incorporated into the experimental design of Liu et al. (2008) was 10 percent (from

2500 to 2750 watts), which did not evidently, improve chamber cleaning compared to changes in reactor pressure and C3F8 and 

O2 flow rates. 
Subpart I Technical Support Document 

November 2010 54 

rates and relative composition of 10 percent or less. Moreover, that definition would not permit change in time for 

stabilizing gas flows. 

It is also worth noting that this definition also applies to in situ chamber cleaning recipes by virtue of the three 

studies on in situ chamber cleaning presented here. These three studies showed that changes of the order of 10 

percent in reactor pressure, reactant flow rates and relative chemical composition resulted in observed changes in 

emissions (including emissions of by-products) and gas utilization of the order of 10 percent or less. 

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