MEMORANDUM

TO: Docket EPA-HQ-OAR-2011-0028

FROM: Alexis McKittrick, EPA/Climate Change

DATE: August 16, 2013

SUBJECT: Final Technical Documentation - Revision of Default Utilization Rates and 

By-Product Formation Rates; Revision of Default Destruction and Removal 

Efficiencies for Semiconductor Facilities under Subpart I; and Revision of 

Maximum Field Detection Limits for the Stack Test Method

This memo documents the updates to the analyses that EPA performed for the proposed 

amendments to subpart I published on October 16, 2012 (77 FR 63538). EPA updated these 

analyses to account for additional data and comments that EPA received in response to the 

proposed amendments. 

Section 1 of this memo documents the updated analysis of the revised etch emission 

factors, originally documented in “Technical Support for Modifications to the Fluorinated 

Greenhouse Gas Emission Estimation Method Option for Semiconductor Facilities under 

Subpart I” (docket item EPA-HQ-OAR-2011-0028-0083).

Section 2 of this memo documents the updated analysis of the revised default factors for 

abatement system destruction or removal efficiency, originally documented in “Technical 

Support for Accounting for Destruction or Removal Efficiency for Electronics Manufacturing 

Facilities under Subpart I” (docket item EPA-HQ-OAR-2011-0028-0082).

Section 3 of this memo documents the updated analysis of the maximum allowed field 

detection limits (FDLS) used in the stack test method, originally documented in “Technical 

Support for the Stack Testing Option for Estimating Fluorinated Greenhouse F-GHG Emissions 

from Electronics Manufacturing Facilities under Subpart I” (docket item EPA-HQ-OAR-2011-

0028-0085).

1.0 REVISION OF DEFAULT UTILIZATION RATES AND BY-PRODUCT 

FORMATION RATES FOR SEMICONDUCTOR FACILITIES UNDER 

SUBPART I

1.1 Introduction

On October 16, 2012, The U.S. Environmental Protection Agency (EPA) proposed 

amendments to the calculation and monitoring methodologies for Subpart I, Electronics 

Manufacturing, of the Greenhouse Gas Reporting Rule (see 77 FR 63538). As part of that action, 

EPA proposed revisions to the default plasma etch and chamber cleaning gas utilization rates and 

by-product formation rates for semiconductor manufacturing facilities. Please refer to the 

memorandum entitled “Technical Support for Modification to the Fluorinated Greenhouse Gas 
2

Emissions Method Option for Semiconductor Facilities under Subpart I, August 2012,” (Docket 

ID EPA-HQ-OAR-2011-0028-0083) for details regarding the development of revised factors.

In response to the proposed rulemaking, the Semiconductor Industry Association (SIA) 

submitted additional utilization and by-product formation rate data from semiconductor 

manufacturing facilities. This part briefly describes the additional data submitted by SIA and the 

incorporation of those data into the calculation of the revised utilization and by-production 

formation rates for the final rulemaking. This part also summarizes the results of the revised 

utilization and by-production formation rate calculations using the new data and presents noted 

differences between EPA calculated factors and those calculated by SIA. This part is organized 

as follows:

1.2 Description of Newly Submitted Data

1.3 Incorporation of New Data into Emission Factor Calculations

1.4 Summary of Revised Default Utilization and By-product Formation Rates

1.2 Description of Newly Submitted Data

As part of their public comment submission (Docket ID: EPA-HQ-OAR-2011-0028-

0095), SIA provided EPA with 168 additional gas utilization and by-product formation rate data 

sets for 200 millimeter (mm) and 300 mm plasma etch equipment. SIA noted in their comment 

submission that the data were provided by semiconductor process equipment suppliers and 

device manufacturers. SIA provided the data in PDF and Microsoft Excel format. SIA’s 

comment letter and the associated attachments can be found in the subpart I rulemaking docket, 

Docket ID: EPA-HQ-OAR-2011-0028.

On May 8, 2013, EPA conducted a meeting with SIA where EPA asked clarifying 

questions regarding possible typographical errors in the data submitted by SIA. SIA 

acknowledged the errors and submitted a corrected version of the data in question, but did not 

include any new data or information. The corrections are located in the document entitled 

“EPA/SIA Meeting – May 8, 2013,” Docket ID: EPA-HQ-OAR-2011-0028-0101. 

For semiconductor manufacturing using 200 mm wafers, the data provided by SIA 

included one gas utilization rate for which no data were previously available (C5F8) and revised 

the utilization rates of four fluorinated greenhouse gases (F-GHGs). For semiconductor 

manufacturing using 300 mm wafers, the new data included two new gas utilization rates for 

C3F8 and CH3F, and additional utilization rates for nine F-GHGs. The new data also provided 75 

revised by-product formation rates, including three new by-products not previously identified 

(C5F8, CH3F, and CH2F2).

1.3 Incorporation of New Data into Emission Factor Calculations

Upon receipt of the additional data from SIA, EPA combined the new utilization and byproduct formation rates with the existing data set used to develop revised emission factors at 

proposal. We then reorganized all of the available emission factors for analysis. This 

reorganization consisted of separating the database into two separate worksheets, one for default 

utilization rates and the other for by-product formation rates. The by-product formation rate 
3

worksheet was further modified such that each row represented a single by-product emission 

factor for each input gas. We reorganized the data sets in such fashion as to calculate revised 

factors using Microsoft Excel Pivot Tables.

EPA used the emission factor calculation methodology outlined in the proposed rule to 

evaluate the new and revised emission factors. Specifically, EPA: 1) Used a simple arithmetic 

averaging method to develop default utilization and by-product emission factors by gas for the 

etch process type; and 2) Used the “all inputs gas” convention for assigning by-product 

formation rates (emission factors) for etch gases. This convention assigns by-product emission to 

input F-GHGs used in a process by dividing the measured mass emitted of a specific by-product 

by the total mass of all input F-GHGs for that process and assigning this by-product factor to 

each input F-GHG used in that process. These methods were described in detail at proposal in 

the memorandum entitled “Technical Support for Modification to the Fluorinated Greenhouse 

Gas Emissions Method Option for Semiconductor Facilities under Subpart I, August 2012,” 

(Docket ID EPA-HQ-OAR-2011-0028-0083). Based on their public comment submission 

(Docket ID: EPA-HQ-OAR-2011-0028-0095), SIA used the same approach described here, and 

in the aforementioned memorandum, to calculate the revised default utilization and byproduction formation rates presented in Tables I.1, I.2, and I.3 of their public comments, and in 

their subsequent corrections to those tables (Docket ID: EPA-HQ-OAR-2011-0028-0101) 

submitted to EPA following the May 8, 2013 meeting between EPA and SIA.

EPA also calculated revised Tier 2a emission factors for semiconductor manufacturing 

facilities for use with the stack testing alternative using the additional data submitted by SIA. Per 

SIA’s recommendation on page 18 of their public comments, EPA calculated revised Tier 2a 

factors for semiconductors using a consumption weighted average where gas usage data were 

available, and an arithmetic (i.e., sample weighted) average where gas usage data were not 

available. To perform these calculations, EPA used the gas consumption weighting factors from 

the Microsoft Excel Workbook entitled “Tier_2a_NF3_and_C2F6_Emission_Factor_ 

Calculations.xls” (Docket ID: EPA-HQ-OAR-2011-0028-0090). The weighting factors presented 

in the workbook were originally obtained from the document entitled “Report to EPA on Etch 

Factor Proposal for Fab GHG Emissions Reporting” (Docket ID: EPA-HQ-OAR-2011-0028-

0074). To address SIA’s suggestion that EPA rework the NF3 emission factors to incorporate 

weighting for the remote clean process sub-type, EPA revised the Tier 2a factors for 

semiconductors to include a separate NF3 remote clean factor. For consistency with previous 

rulemakings, EPA selected the same default emission factor for NF3 remote clean as described in 

the November 2010 TSD (Docket ID: EPA-HQ-OAR-2009-0927-0195) .

1.4 Summary of Revised Default Utilization and By-production Formation Rates

Tables 1.1 through 1.8 summarize the new and revised default utilization and by-product 

formation rates that are included in the final subpart I rule amendments. 

Table 1-1. Revised Default Emission Factors (1-Uij) for Gas Utilization Rate (Uij) for 

Semiconductor Manufacturing for 150 mm and 200 mm Wafer Sizes for the Plasma 

Etching/Wafer Cleaning Process Type

Input Gas Proposal Presented by SIA Revised Final

No. Of Data Sets (1-Uij) No. Of Data Sets (1-Uij) No. Of Data Sets (1-Uij)

C2F6 40 0.76 43 0.72 43 0.72
4

Input Gas Proposal Presented by SIA Revised Final

No. Of Data Sets (1-Uij) No. Of Data Sets (1-Uij) No. Of Data Sets (1-Uij)

C2HF5 31 0.064 31 0.064 31 0.064

C4F6 14 0.17 14 0.17 14 0.17

C4F8 44 0.14 53 0.14 53 0.14

C5F8 0 NA 1 0.072 1 0.072

CF4 126 0.81 134 0.81 134 0.81

CH2F2 43 0.13 44 0.13 44 0.13

CH3F 1 0.66 3 0.70 3 0.70

CHF3 131 0.50 136 0.51 136 0.51

NF3 22 0.20 23 0.19 23 0.19

SF6 129 0.55 132 0.55 132 0.55

Table 1-2. Revised Default Emission Factors (1-Uij) for Gas Utilization Rate (Uij) and for 

Semiconductor Manufacturing for 300 mm and 450 mm Wafer Sizes for the Plasma 

Etching/Wafer Cleaning Process Type

Input Gas Proposal Presented by SIA Revised Final

No. Of Data Sets (1-Uij) No. Of Data Sets (1-Uij) No. Of Data Sets (1-Uij)

C2F6 2 0.80 1 0.81 2 0.80

C4F6 37 0.18 46 0.15 45 0.15

C4F8 77 0.17 90 0.19 90 0.18

C5F8 12 0.13 16 0.10 16 0.10

CF4 78 0.63 101 0.65 104 0.65

CH2F2 39 0.15 56 0.20 57 0.21

CH3F 0 NA 13 0.33 13 0.33

CHF3 66 0.39 90 0.43 91 0.42

NF3 52 0.17 66 0.16 66 0.15

SF6 37 0.23 46 0.32 46 0.32

C3F8 0 NA 4 0.30 4 0.30

Bold values indicate a difference between the SIA presented value and the final EPA value.

Some differences in Table 1-2 are noted between the values presented by SIA and the 

final values determined by EPA for C2F6, C4F6, C4F8, CF4, CH2F2, and CHF3. EPA was able to 

identify the source of all the differences except for one, as explained in the following paragraphs.

In Table I.2 on page 8 of SIA’s public comment submission (Docket ID: EPA-HQ-OAR2011-0028-0095), SIA indicates that only one data set was available in 2011 for C2F6 for 

300mm, and lists an emission factor of 0.811 kg per kg. However, in the October 16, 2012 

proposal (77 FR 63538), EPA proposed a default emission factor for C2F6 of 0.80 kg per kg 

based on two data sets (0.779 kg per kg and 0.811 kg per kg), which were included in the 

document “Draft Emission Factors for Refined Semiconductor Manufacturing Process 

Categories,” (Docket ID: EPA-HQ-OAR-2009-0927-0073). The latter document was referenced 

by the May 13, 2010 Federal Register notice, “Mandatory Reporting of Greenhouse Gases: 

Notice of Data Availability; Default Emission Factors for Semiconductor Manufacturing Refined 

Process Categories” (75 FR 26904). Additionally, these two data sets were used to develop the 

default emission factor for C2F6 for 300 mm in Table I-4 to subpart I in the final rule 

promulgated on December 1, 2010 (75 FR 74774). In the final rule, the EPA is using the two 

data sets instead of the single data set cited by SIA.
5

SIA indicated in Table I.2 of their public comment submission that 46 data sets are now 

available for C4F6 for 300 mm fabs. EPA believes that SIA may be counting an emission factor 

for C4F6 of “N/A,” which was provided by SIA in the document “International SEMATECH 

Manufacturing Initiative Environmental Safety and Health Technology Center Etch Process 

Equipment Emissions Characterization Data,” (Docket ID: EPA-HQ-OAR-2011-0028-0071). 

EPA did not include this “N/A” emission factor in the final count of data sets presented in Table 

1-2 above.

The difference in the final emission factor for C4F8 shown in Table 1-2 above as 

calculated by SIA and EPA appears to be due to a transcription error of the factor 0.0581 kg per 

kg. In “Attachment A” to SIA’s public comment submission, the last 13 emission factors were 

offset one column to the left. EPA believes SIA may have included the line item for this factor in 

their count of data sets, but did not include the actual value in their calculation of the average for 

C4F8. Similarly, for CF4, EPA believes SIA included the three values that were offset (0.0891, 

0.85, 0.7304 kg per kg) in their final calculation of the average, but not in their final count of 

data sets.

The difference in the data set count and emission factor for CH2F2 shown in Table 1-2 

above appears to originate from an inadvertent omission of one emission factor data set by SIA. 

In Table I.2 on page 8 of SIA’s public comment submission, SIA indicated that for the total 

number of data sets available at proposal, 38 data sets were available for CH2F2, and calculated 

an emission factor of 0.144961 kg per kg. Based on the data available to EPA, 39 data sets were 

available at proposal for a calculated emission factor of 0.147397 kg per kg. EPA is able to 

reproduce the count and emission factor calculated by SIA by excluding the wafer clean factor of 

0.24 kg per kg provided on page 16 of 29 of the document “Draft Emission Factors for Refined 

Semiconductor Manufacturing Process Categories,” (Docket ID: EPA-HQ-OAR-2009-0927-

0073). Because EPA is able to reproduce SIA’s count and average emission factor by omitting 

this value, we believe SIA may have inadvertently omitted the value from their emission factor 

calculations for CH2F2. 

The difference in the data set count and emission factor for CHF3 shown in Table 1-2 

above also appears to originate from an inadvertent omission of one emission factor data set by 

SIA. In Table I.2 on page 8 of SIA’s public comment submission, SIA indicates that for the total 

number of data sets available at proposal, 65 data sets were available for CHF3, and calculated an 

emission factor of 0.386291 kg per kg. Based on the data available to EPA, 66 data sets were 

available at proposal for a calculated emission factor of 0.387029 kg per kg. EPA is able to 

reproduce the count and emission factor calculated by SIA by excluding the emission factor for 

an oxide film type and via feature type of 0.435 kg per kg provided on page 6 of 15 of 

“International SEMATECH Manufacturing Initiative Environmental Safety and Health 

Technology Center Etch Process Equipment Emissions Characterization Data,” (Docket ID: 

EPA-HQ-OAR-2011-0028-0071). Because EPA is able to reproduce SIA’s count and average 

emission factor by omitting this value, we believe SIA may have inadvertently omitted the value 

from their emission factor calculations.

EPA was unable to determine the origin of the discrepancy between SIA’s calculated 

emission factor for NF3 and EPA’s calculated factor shown in Table 1-2 above. We note that in 

Table I.2 on page 8 of SIA’s public comment submission, SIA indicated, at proposal, a count of 
6

52 data sets for NF3 and a calculated emission factor of 0.171608 kg per kg. Based on the data 

available to EPA, we confirmed that at proposal, a total of 52 data sets were available, all of 

which originated from the document “International SEMATECH Manufacturing Initiative 

Environmental Safety and Health Technology Center Etch Process Equipment Emissions 

Characterization Data,” (Docket ID: EPA-HQ-OAR-2011-0028-0071). However, using the 

same 52 data sets used to calculate the proposed emission factor, EPA calculated an emission 

factor of 0.16766 kg per kg, which agrees with the previous emission factor calculation. The 

difference between the previously calculated value and the SIA value from the data at proposal is 

0.003948 kg per kg. Though the source of this discrepancy is unclear, we believe that this 

difference was carried forward and led to SIA calculating a value of 0.15503 (rounded to 0.16) 

and EPA a value 0.15048 (rounded to 0.15) for the emission factor for NF3. Because EPA was 

able to confirm the previous calculation of the proposed emission factor, we are using the results 

of our current analysis in the final rule.

Table 1-3. Revised Default Emission Factors for By-Product For mation Rates (Bijk) for 

Semiconductor Manufacturing for 150 mm and 200 mm Wafer Sizes for the Etching/Wafer 

Cleaning Process Type

Input Gas By-Product Proposal Presented by SIA Revised Final

No. Of Data Sets (Bijk) No. Of Data Sets (Bijk) No. Of Data Sets (Bijk)

C2F6

CF4 36 0.10 39 0.10 39 0.10

CHF3 0 NA 3 0.047 3 0.047

C2HF5

C2F6 31 0.024 31 0.024 31 0.024

CF4 31 0.077 31 0.077 31 0.077

C4F6

C2F6 12 0.11 12 0.11 12 0.11

CF4 12 0.13 12 0.13 12 0.13

CHF3 1 0.066 1 0.066 1 0.066

C4F8

C2F6 38 0.037 44 0.037 44 0.037

CF4 41 0.12 47 0.11 47 0.11

CHF3 0 NA 5 0.040 5 0.040

C5F8 0 NA 2 0.0086 2 0.0086

C5F8

C2F6 0 NA 1 0.014 1 0.014

CHF3 0 NA 1 0.0039 1 0.0039

CF4

C2F6 96 0.048 102 0.046 102 0.046

CHF3 60 0.11 63 0.10 63 0.10

C5F8 0 NA 1 0.0012 1 0.0012

CH2F2

C2F6 34 0.025 35 0.025 35 0.025

CF4 40 0.081 41 0.079 41 0.079

CHF3 1 0.066 2 0.049 2 0.049

CH3F C2F6 0 NA 2 0.0034 2 0.0034

CHF3

C2F6 65 0.031 70 0.030 70 0.030

CF4 72 0.085 72 0.085 72 0.085

C5F8 0 NA 1 0.0012 1 0.0012

NF3

C2F6 0 NA 1 0.025 1 0.025

CF4 1 0.0040 1 0.0040 1 0.0040

SF6

C2F6 1 0.17 2 0.11 2 0.11

CF4 2 0.15 3 0.13 3 0.13

CHF3 0 NA 1 0.0012 1 0.0012
7

Table 1-4. Revised Default Emission Factors for By-Product For mation Rates (Bijk) for 

Semiconductor Manufacturing for 300 mm and 450 mm Wafer Sizes for the Etching/Wafer 

Cleaning Process Type

Input 

Gas

ByProduct

Proposal Presented by SIA Revised Final

No. Of Data

Sets (Bijk) No. Of Data Sets (Bijk) No. Of Data Sets (Bijk)

C2F6 CF4 1 0.21 0 NA 1 0.21

C4F6

C2F6 22 0.090 27 0.074 27 0.074

CF4 33 0.066 37 0.059 37 0.059

CHF3 30 0.022 34 0.019 34 0.019

CH2F2 0 NA 4 0.000030 4 0.000030

C4F8

C2F6 50 0.030 57 0.031 57 0.031

C4F6 2 0.018 2 0.018 2 0.018

CF4 71 0.046 80 0.045 80 0.045

CHF3 65 0.028 73 0.027 73 0.027

CH2F2 0 NA 4 0.0015 4 0.0015

C5F8

C2F6 9 0.083 9 0.083 9 0.083

CF4 12 0.15 16 0.11 16 0.11

CHF3 8 0.010 12 0.0069 12 0.0069

C3F8 0 NA 4 0.00012 4 0.00012

CF4

C2F6 60 0.092 75 0.079 75 0.079

C4F8 3 0.00063 3 0.00063 3 0.00063

CHF3 40 0.011 41 0.011 41 0.011

CH3F 0 NA 1 0.0080 1 0.0080

CH2F2

C2F6 15 0.068 22 0.052 22 0.052

CF4 27 0.059 34 0.049 34 0.049

CHF3 27 0.052 34 0.050 34 0.050

CH3F 0 NA 1 0.0080 1 0.0080

CH3F

C2F6 0 NA 4 0.00087 4 0.00087

CF4 0 NA 5 0.045 5 0.045

CHF3 0 NA 5 0.0057 5 0.0057

CH2F2 0 NA 4 0.0023 4 0.0023

CHF3

C2F6 47 0.078 64 0.064 64 0.064

C4F6 1 0.00010 1 0.00010 1 0.00010

C4F8 2 0.00080 2 0.00080 2 0.00080

CF4 48 0.10 54 0.10 54 0.10

CH3F 0 NA 1 0.0080 1 0.0080

CH2F2 0 NA 3 0.0036 3 0.0036

NF3

C2F6 11 0.057 14 0.045 14 0.045

CF4 31 0.052 36 0.046 36 0.046

CHF3 9 0.035 13 0.025 13 0.025

CH3F 0 NA 1 0.0080 1 0.0080

CH2F2 0 NA 4 0.00086 4 0.00086

SF6

C2F6 8 0.067 13 0.044 13 0.044

CF4 15 0.045 19 0.040 19 0.040

CHF3 0 NA 5 0.0037 5 0.0037

CH2F2 0 NA 2 0.000029 2 0.000029

C3F8

C2F6 0 NA 4 0.18 4 0.18

CF4 0 NA 4 0.21 4 0.21

CHF3 0 NA 4 0.012 4 0.012

CH3F 0 NA 3 0.00073 3 0.00073
8

Table 1-5. Revised Tier 2a Default Emission Factors (1-Uij) for 

Gas Utilization Rate (Uij) for Semiconductor Manufacturing for 150 mm and 200 mm Wafer Sizes

Input Gas Proposed Tier 2a 

Emission Factor

Final Tier 2a Emission 

Factor Calculation Note

C2F6 0.71 0.56 Consumption weighted

C2HF5 0.064 0.064 Arithmetic average – Emission factor data available for etch only

C4F6 0.17 0.17 Arithmetic average – Emission factor data available for etch only

C4F8 0.14 0.13 Consumption weighted

C5F8 NA 0.072 Arithmetic average – Emission factor data available for etch only

CF4 0.81 0.85 Consumption weighted

CH2F2 0.13 0.13 Arithmetic average – Emission factor data available for etch only

CH3F 0.66 0.70 Arithmetic average – Emission factor data available for etch only

CHF3 0.50 0.51 Arithmetic average – Emission factor data available for etch only

NF3 0.19 0.16 Consumption weighted – outliers removed[A]

NF3 Remote Clean [B] 0.018 [C]

SF6 0.55 0.55 Arithmetic average – Emission factor data available for etch only

C3F8 0.40 0.40 Arithmetic average – Emission factor data available for in-situ plasma cleaning only

C4F8O 0.14 0.14 Arithmetic average – Emission factor data available for in-situ plasma cleaning only

[A] – Three NF3 emission factor values under remote plasma cleaning were identified as outlier values. These outlier values were identified in 

“Tier_2a_NF3_and_C2F6_Emission_Factor_Calculations.xls” (Docket ID: EPA-HQ-OAR-2011-0028-0090).

[B] – An Tier 2a NF3 remote clean factor was not included in the October 16, 2012 proposed amendments (see 77 FR 63538).

[C] – The remote clean beta distribution emission factor (CVD Remote) was not developed using a simple averaging method. Please refer to the analysis in the November 

2010 TSD (Docket ID: EPA-HQ-OAR-2009-0927-0195) of the NF3 Remote Clean emission factor, which states that emission factor values with utilization efficiencies 

between 81 percent and 89 percent were removed after a statistical analysis was performed on the data. A mean value of 0.018 was chosen by EPA after removing the 

outliers for remote plasma chamber cleaning with NF3 for both 200 and 300 mm wafer processing systems by fitting the data to a beta distribution.
9

Table 1-6. Revised Tier 2a Default Emission Factors (1-Uij) for 

Gas Utilization Rate (Uij) for Semiconductor Manufacturing for 300 mm and 450 mm Wafer Sizes

Input Gas Proposed Tier 2a 

Emission Factor

Final Tier 2a Emission 

Factor Calculation Note

C2F6 0.80 0.80 Arithmetic average – Emission factor data available for etch only

C4F6 0.18 0.15 Arithmetic average – Emission factor data available for etch only

C4F8 0.17 0.18 Arithmetic average – Emission factor data available for etch only

C5F8 0.13 0.10 Arithmetic average – Emission factor data available for etch only

CF4 0.63 0.65 Arithmetic average – Emission factor data available for etch only

CH2F2 0.15 0.21 Arithmetic average – Emission factor data available for etch only

CH3F NA 0.33 Arithmetic average – Emission factor data available for etch only

CHF3 0.39 0.42 Arithmetic average – Emission factor data available for etch only

NF3 0.17 0.20 Consumption weighted

NF3 Remote Clean [A] 0.018 [B]

SF6 0.23 0.32 Consumption weighted

C3F8 0.063 0.20 Arithmetic average – Consumption data available for etch only[C]

[A] – A Tier 2a NF3 remote clean factor was not included in the October 16, 2012 proposed amendments (see 77 FR 63538).

[B] – The remote clean beta distribution emission factor (CVD Remote) was not developed using a simple averaging method. Please refer to the analysis in the November 

2010 TSD (Docket ID: EPA-HQ-OAR-2009-0927-0195) of the NF3 Remote Clean emission factor, which states that emission factor values with utilization efficiencies 

between 81 percent and 89 percent were removed after a statistical analysis was performed on the data. A mean value of 0.018 was chosen by EPA after removing the 

outliers for RPS chamber cleaning with NF3 for both 200 and 300 mm wafer processing systems by fitting the data to a beta distribution.

[C] – Emission factor data available for both etch and remote plasma cleaning, however, consumption data are only available for etch.
10

Table 1-7. Revised Tier 2a By-product For mation Rates (Bijk) for 

Semiconductor Manufacturing for 150 mm and 200 mm Wafer Sizes

Input Gas By-Product Proposed Tier 2a 

Emission Factor

Final Tier 2a 

Emission Factor Calculation Note

C2F6

CF4 0.13 0.19 Consumption weighted

CHF3 NA 0.047 Arithmetic average – Emission factor available for etch only

C2HF5

C2F6 0.024 0.024 Arithmetic average – Emission factor available for etch only

CF4 0.077 0.077 Arithmetic average – Emission factor available for etch only

C4F6

C2F6 0.11 0.11 Arithmetic average – Emission factor available for etch only

CF4 0.13 0.13 Arithmetic average – Emission factor available for etch only

CHF3 NA 0.066 Arithmetic average – Emission factor available for etch only

C4F8

C2F6 0.037 0.037 Arithmetic average – Emission factor available for etch only

C5F8 NA 0.0086 Arithmetic average – Emission factor available for etch only

CF4 0.12 0.11 Consumption weighted

CHF3 NA 0.040 Arithmetic average – Emission factor available for etch only

C5F8

C2F6 NA 0.014 Arithmetic average – Emission factor available for etch only

CHF3 NA 0.0039 Arithmetic average – Emission factor available for etch only

CF4

C2F6 0.048 0.046 Arithmetic average – Emission factor available for etch only

C5F8 NA 0.0012 Arithmetic average – Emission factor available for etch only

CHF3 0.11 0.10 Arithmetic average – Emission factor available for etch only

CH2F2

C2F6 0.025 0.025 Arithmetic average – Emission factor available for etch only

CF4 0.081 0.079 Arithmetic average – Emission factor available for etch only

CHF3 0.066 0.049 Arithmetic average – Emission factor available for etch only

CH3F C2F6 NA 0.0034 Arithmetic average – Emission factor available for etch only

CHF3

C2F6 0.031 0.030 Arithmetic average – Emission factor available for etch only

C5F8 NA 0.0012 Arithmetic average – Emission factor available for etch only

CF4 0.085 0.085 Arithmetic average – Emission factor available for etch only

NF3

C2F6 NA 0.025 Arithmetic average – Emission factor available for etch only

CF4 0.021 0.045 Consumption weighted

NF3 Remote Clean CF4 [A] 0.015 [B]

SF6

C2F6 0.17 0.11 Arithmetic average – Emission factor available for etch only

CF4 0.15 0.13 Arithmetic average – Emission factor available for etch only

CHF3 NA 0.0012 Arithmetic average – Emission factor available for etch only

C3F8 CF4 0.20 0.20 Arithmetic average – Emission factor available for in-situ plasma cleaning only

C4F8O C2F6 0.045 0.045 Arithmetic average – Consumption data unavailable for C4F8O

CF4 0.13 0.13 Arithmetic average – Consumption data unavailable for C4F8O

[A] – A Tier 2a NF3 remote clean factor was not included in the October 16, 2012 proposed amendments (see 77 FR 63538).

[B] – The remote clean beta distribution emission factor (CVD Remote) was not developed using a simple averaging method. Please refer to the analysis in the November 

2010 TSD (Docket ID: EPA-HQ-OAR-2009-0927-0195) of the NF3 Remote Clean emission factor, which states that emission factor values with utilization efficiencies 

between 81 percent and 89 percent were removed after a statistical analysis was performed on the data. A mean value of 0.018 was chosen by EPA after removing the 

outliers for remote plasma chamber cleaning with NF3 for both 200 and 300 mm wafer processing systems by fitting the data to a beta distribution.
11

Table 1-8. Revised Tier 2a By-product For mation Rates (Bijk) for 

Semiconductor Manufacturing for 300 mm and 450 mm Wafer Sizes

Input Gas By-Product Proposed Tier 2a Emission Factor Final Tier 2a Emission Factor Calculation Note

C2F6 CF4 0.21 0.21 Arithmetic average – Emission factor available for etch only

C4F6

C2F6 0.090 0.074 Arithmetic average – Emission factor available for etch only

CF4 0.066 0.059 Arithmetic average – Emission factor available for etch only

CH2F2 NA 0.000030 Arithmetic average – Emission factor available for etch only

CHF3 0.022 0.019 Arithmetic average – Emission factor available for etch only

C4F8

C2F6 0.030 0.031 Arithmetic average – Emission factor available for etch only

C4F6 0.018 0.018 Arithmetic average – Emission factor available for etch only

CF4 0.046 0.045 Arithmetic average – Emission factor available for etch only

CH2F2 NA 0.0015 Arithmetic average – Emission factor available for etch only

CHF3 0.028 0.027 Arithmetic average – Emission factor available for etch only

C5F8

C2F6 0.083 0.083 Arithmetic average – Emission factor available for etch only

C3F8 NA 0.00012 Arithmetic average – Emission factor available for etch only

CF4 0.013 0.11 Arithmetic average – Emission factor available for etch only

CHF3 0.010 0.0069 Arithmetic average – Emission factor available for etch only

CF4

C2F6 0.092 0.079 Arithmetic average – Emission factor available for etch only

C4F8 0.00063 0.00063 Arithmetic average – Emission factor available for etch only

CH3F NA 0.0080 Arithmetic average – Emission factor available for etch only

CHF3 0.011 0.011 Arithmetic average – Emission factor available for etch only

CH2F2

C2F6 0.068 0.052 Arithmetic average – Emission factor available for etch only

CF4 0.059 0.049 Arithmetic average – Emission factor available for etch only

CH3F NA 0.0080 Arithmetic average – Emission factor available for etch only

CHF3 0.052 0.050 Arithmetic average – Emission factor available for etch only

CH3F

C2F6 NA 0.00087 Arithmetic average – Emission factor available for etch only

CF4 NA 0.045 Arithmetic average – Emission factor available for etch only

CH2F2 NA 0.0023 Arithmetic average – Emission factor available for etch only

CHF3 NA 0.0057 Arithmetic average – Emission factor available for etch only

CHF3

C2F6 0.078 0.064 Arithmetic average – Emission factor available for etch only

C4F6 0.00010 0.00010 Arithmetic average – Emission factor available for etch only

C4F8 0.00080 0.00080 Arithmetic average – Emission factor available for etch only

CF4 0.10 0.10 Arithmetic average – Emission factor available for etch only

CH2F2 NA 0.0036 Arithmetic average – Emission factor available for etch only

CH3F NA 0.0080 Arithmetic average – Emission factor available for etch only

NF3

C2F6 0.057 0.045 Arithmetic average – Emission factor available for etch only

CF4 0.062 0.040 Consumption weighted

CH2F2 NA 0.00086 Arithmetic average – Emission factor available for etch only

CH3F NA 0.0080 Arithmetic average – Emission factor available for etch only

CHF3 0.035 0.025 Arithmetic average – Emission factor available for etch only

NF3 Remote Clean CF4 [A] 0.075 [B]

SF6

C2F6 0.067 0.044 Arithmetic average – Emission factor available for etch only

CF4 0.062 0.040 Arithmetic average – Emission factor available for etch only

CH2F2 NA 0.000029 Arithmetic average – Emission factor available for etch only

CHF3 NA 0.0037 Arithmetic average – Emission factor available for etch only

C3F8 C2F6 NA 0.18 Arithmetic average – Emission factor available for etch only
12

Input Gas By-Product Proposed Tier 2a Emission Factor Final Tier 2a Emission Factor Calculation Note

CF4 NA 0.21 Arithmetic average – Emission factor available for etch only

CH3F NA 0.00073 Arithmetic average – Emission factor available for etch only

CHF3 NA 0.012 Arithmetic average – Emission factor available for etch only

[A] - A Tier 2a NF3 remote clean factor was not included in the October 16, 2012 proposed amendments (see 77 FR 63538).

[B] – The remote clean beta distribution emission factor (CVD Remote) was not developed using a simple averaging method. Please refer to the analysis in the November 

2010 TSD (Docket ID: EPA-HQ-OAR-2009-0927-0195) of the NF3 Remote Clean emission factor, which states that emission factor values with utilization efficiencies 

between 81 percent and 89 percent were removed after a statistical analysis was performed on the data. A mean value of 0.018 was chosen by EPA after removing the 

outliers for remote plasma chamber cleaning chamber cleaning with NF3 for both 200 and 300 mm wafer processing systems by fitting the data to a beta distribution.
13

2.0 DERIVATION OF DEFAULT DRES USING VARIANCE COMPONENTS 

METHOD

2.1 Introduction

This part provides technical support for the changes to the derived default destruction and 

removal efficiencies (DREs) for point-of-use (POU) abatement systems under subpart I, 

Electronics Manufacturing, of the Greenhouse Gas Reporting Program (GHGRP). Specifically, 

this part provides EPA’s methodology for derivation of default DREs, which is based on a 

statistical method suggested by the Semiconductor Industry Association (SIA) in Attachment C 

of their comments to the proposed amendments to Subpart I (Docket Id. No. EPA-HQ-OAR2011-0028-0095), and using the data available for the final rule amendments. 

In their comments on the proposed amendments published on October 16, 2012 (77 FR 

63538), SIA indicated that it performed a Components of Variance Analysis, using a random 

effects model, to generate variance components to estimate how much of the overall variability is 

associated with the differences among fabs (σ2

Fabs) versus the differences among the devices in 

a fab (σ2

Devices). (See docket item EPA-HQ-OAR-2011-0028-0095, attachment C, for the 

SIA’s explanation of their methodology.) The SIA argued that this method was more appropriate 

for developing a default DRE value for all the devices in a fab and would result in higher default 

DRE values that the method used by EPA to develop the proposed values.

EPA has reproduced this analysis using the full DRE dataset that is based on the data 

used in the development of the final 2010 subpart I rule, the proposed amendments, and 

additional data provided during the public comment period for the proposed amendments. The 

EPA’s rationale for selecting the SIA’s method over the EPA method used for the proposed 

amendments is included in the preamble to the final rule amendments.

2.2 Overview for Estimation of Variance Components

Analysis of Variance (ANOVA) is a statistical analysis that can be used to test the 

hypothesis that the means among two or more groups are equal. In an ANOVA, the variation in 

the measurements is segregated into components that correspond to different sources of variation 

(i.e., the variation in the average DRE across fabs (σ

2

Fabs) versus the variation in DRE across 

individual devices in a fab (σ2

Devices). Individual fabs that provide DRE test data will have 

averages that are affected by both sources of variability. The mathematical model that describes 

the relationship between the response and treatment for the one-way ANOVA is given by:

Yij = μ + τi + εij

where Yij represents the j-th observation (j = 1, 2, ...ni) on the i-th treatment (i = 1, 2, ..., k

levels). The parameter μ represents the overall average DRE in the data for a gas, τi represents 

the i-th treatment effect (e.g., the differences between fabs) and εij represents the random error 

present in the j-th observation on the i-th treatment (the differences between the performance of 

device j from the average in its fab). For the DRE data, this may be conceptually written as:

DREFab I, Device J = DRE0 + ΔDREFab I + ΔDREFab I, Device J 
14

where DRE0 is equivalent to μ, ΔDREFab I is τi , and ΔDREFab I, Device J is εij.

Because the sampling of the DRE population is based on a random selection of fabs from 

the larger population, the model used is a random effects model, with errors εij assumed to be 

normally and independently distributed, with mean zero and variance σε

2

, and treatments τi

normally and independently distributed with mean zero and variance στ2. A random effects 

model is used because we do not know whether a particular fab or device is above or below the 

average for fabs or for devices within the fab. 

The random effects model is acceptable for the purpose of identifying the sources of 

variance in a sample and making inferences regarding the size (magnitude) of each source of 

variance, which are estimated as the variance components σε

2 and στ2

. These variance 

components are used to derive the default DREs for each gas (see Section 2.3 of this document).

2.3 Methodology

EPA performed the ANOVA on the available DRE dataset using data and information 

from the following:

• 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 – November 2010 , docket item EPA-HQ-OAR2009-0927-0195.

• Technical Support for Accounting for Destruction or Removal Efficiency for 

Electronics Manufacturing Facilities under Subpart I, docket item EPA-HQ-OAR2011-0028-0082.

• Data submitted by SIA during the public comment period and available in docket 

item EPA-HQ-OAR-2011-0028-0095, attachment B.

EPA followed a basic methodology to complete the ANOVA that was referenced by the 

commenters and is outlined in the NIST/SEMATECH e-Handbook of Statistical Methods.1

An alternative method to fit random-effects models is Maximum Likelihood Estimation 

(MLE). Unlike LSE, MLE requires no minimal distributional assumptions, and therefore can be 

used with data that are not normally distributed. MLE is a standard approach to parameter 

estimation and inference in statistics and econometrics. The principle of maximum likelihood 

estimation states that the desired probability distribution is the one that makes the available data 

Standard ANOVA uses a least-squares estimation (LSE) approach, which hinges on the 

assumption that the analyzed variable is normally distributed. However, for the available DRE 

data, observations are typically restricted in the interval between 0 and 100 and clustered towards 

the top end of the distribution.

 1 http://www.itl.nist.gov/div898/handbook/ (accessed May 18, 2013.)
15

“most likely” to be observed.2

EPA first performed an ANOVA on an individual-gas basis and calculated restricted 

maximum likelihood estimates of the variance components for all gases using Stata software. 

The variance components for the DRE data are defined as στ

2

= σ

2

(Fabs) and σε

2

= σ

2

(Devices). 

The variance components from this model are provided in Table 2-1 of this document and are 

used to calculate default DREs for each gas (see Section 2.3 of this document).

The MLE estimation method is known to be biased when the true 

population mean is unknown (e.g., for small sample sizes, the sample average is less likely to be 

a good predictor of the population mean). Therefore, a variant of MLE, the restricted maximum 

likelihood (REML) method, is used. REML is typically used for fitting mixed models that have 

both fixed-effect and random-effect portions. In contrast to the MLE method, the REML 

methodology produces less biased results. 

In the proposed amendments, EPA grouped together the non-CF4 carbon-based etch gases 

to set a group-average default of 98 percent. In their comments on the proposed rule, SIA 

recommended that EPA continue to group the non-CF4 carbon-based etch gases, and provided an 

analysis that augmented the random effects model to calculate the variance components for the 

combined gases, including a variance component for differences among the individual gases. 

This analysis assumed that the different carbon-based etch gases have the same DRE 

distributions. 

To determine a group-average for the non-CF4 carbon-based etch gases, EPA has 

calculated variance components using a joint model where the gas is treated as a fixed effect and 

the fab and individual device error are treated as random effects. Fixed effects are variables that 

do not change and are not based on a random sample. This model is more appropriate for 

estimating the variance components of the combined carbon-based gases because, in contrast to 

the SIA approach, as it does not treat the gas as a random effect of the sampling. The use of a 

joint model also avoids the limitations of the individual-gas approach that arise when only small 

sample sizes are available. Because MLE estimates are calculated as the best fit to the observed 

data, when fewer observations are available, there is a greater risk that the estimates will be 

further from the actual population parameters. Because the sample sizes of several carbon-based 

etch gases are quite small (less than 10 observations), the estimated variance components from 

the joint model may have better statistical power than those calculated using the individual gas 

method. 

For the same reasons, EPA also used the REML methodology discussed above to develop 

variance estimates in the joint model. In small samples, REML produces variance component 

estimates that are less biased because it takes into consideration the degrees of freedom from the 

fixed effects. The variance components for the combined carbon-based etch gases are provided 

in Table 2-2 of this document. These variance components are used to calculate a group-average 

default DRE as discussed in Section 2.3 of this document.

 2 For details on MLE estimation, see Myung, IJ. 2002. Tutorial on maximum likelihood estimation. Journal of Mathematical Psychology

47(2003), pp. 90–100. Available at: http://people.physics.anu.edu.au/~tas110/Teaching/Lectures/L3/Material/Myung03.pdf (accessed June 13, 

2013).
16

2.4 Derivation of Default DREs

The variance components derived in Section 2.2 are used in the derivation of the default 

DREs based on the method suggested by SIA, which uses the variance components to adjust the 

standard deviation of the fab average. In particular, if a fab is picked at random, and it contains N 

devices abating a particular gas, its average DRE would be expected to vary from the overall 

average for the gas by an amount governed by the standard deviation for fab averages: σ = sqrt 

(σ

2 (Fabs) + σ2 (Devices)/N). Therefore, the lowest average DRE for a fab is estimated using the 

formula:

Default DRE = DRE0 - 2 x sqrt [σ

2 (Fabs) + σ2 (Devices) / N ] (Equation 1)

where the mean DRE0 is the overall average DRE in the data for the gas, the variance 

components σ2

(Fabs) and σ2(Devices) are defined above, and N is based on the smallest number 

of abatement devices that one is expected to find in a fab. The values of N are based on the 

results of an SIA survey of its members and are as follows: 

Etch CF4: N = 20 

NF3: N = 15 

SF6: N = 10 

Other Carbon-based Gases: N = 5 

NF3 Chamber Cleaning: N = 20

Although SIA did not include singleton data points (i.e., data points from fabs in which 

only one DRE measurement is available) in calculating the fab average DRE for each gas, EPA 

has included the singleton data points in both the analysis of the variance components and in the 

calculation of the default DREs for consistency in the treatment of the available data from each 

fab. The calculation of the default DRE relies on the average of individual observations. 

Therefore, the singleton observations are not more likely to be outliers and would not affect the 

overall mean differently than a fab with more than one data point for a particular gas.

In Table 2-1, the default DRE is assigned for each gas on an individual-gas basis. This 

approach would allow for facilities to take advantage of the higher DREs for individual gases but 

may be more burdensome to reporters accounting for many of these gases in their abatementrelated calculations. EPA estimated variance components (σ(Fabs) and σ(Devices)) for the 

individual-gas approach, as described in Section 2.2, and developed the default DREs for each 

gas using Equation 1.

Table 2-1. Etch and Clean DRE, Analysis of Variance, 

Restricted Maximum Likelihood (Individual Gas Basis)

Input 

Gas

DRE 

Average

DRE 

Count Fabs σ(Fabs) σDevices) N Default DRE

SIA value 

included in 

comments

C2F6 98.8 5 3 1.849 0.497 5 95.12 97

C4F6 98.6 9 2 2.57E-09 2.541 5 96.28 96

C4F8 98.5 24 2 0.748 1.687 5 96.37 97

C5F8 96.6 1 1 0.000 0.000 5 96.59 97

CF4 83.6 66 7 4.79E-05 18.309 20 75.37 75
17

Input 

Gas

DRE 

Average

DRE 

Count Fabs σ(Fabs) σDevices) N Default DRE

SIA value 

included in 

comments

CH2F2 98.7 30 2 0.623 1.590 5 96.85 97

CH3F 99.2 4 3 7.83E-11 0.927 5 98.41 98

CHF3 99.1 43 4 0.691 1.140 5 97.38 98

NF3

(etch) 98.5 31 3 3.27E-07 4.205 15 96.34 96

NF3

(clean) 93.3 110 6 1.829 9.377 20 87.76 88

SF6 98.7 2 0 6 0.659 1.010 10 97.22 98

For the combined non-CF4 carbon-based etch gases, the default DRE is calculated 

similarly, with the exception that DRE0 (from Equation 1) is the modeled DRE Fixed Effect 

estimate for each gas. The DRE Fixed Effect estimate is derived from the REML methodology 

and is calculated in Stata. This estimate is used in lieu of the raw DRE average for each gas 

because the raw averages for each gas include variations between fabs, and are therefore less 

precise. For example, even if a high raw average is observed for an individual gas, this may be 

caused by the fact that a disproportionate amount of the observations are coming from a fab 

which has "above average" DRE.

EPA calculated the variance components (σ(Fabs) and σ(Devices)) for the non-CF4

carbon-based etch gases using Stata. The results are shown in Table 2-2 below. The variance 

components only describe the variability between fabs and between devices (any difference 

between gases is already accounted for by the gas effect, which is assumed to be fixed), thus, 

these values do not change for each gas. The default DRE may be averaged over all the gases to 

produce a group-average DRE of 96.71 percent for the non-CF4 carbon-based etch gases. 

Table 2-2. Etch DRE for non-CF4 carbon-based F-GHG, 

Joint Model, Restricted Maximum Likelihood 

Input 

Gas

DRE 

Fixed 

Effect

DRE 

Count Fabs σ(Fabs) σ(Devices) N Default DRE

GroupAverage 

DRE

SIA 

groupaverage 

value

C2F6 98.6 116 5 0.631 1.523 5 96.76

96.71 97

C4F6 98.6 116 5 0.631 1.523 5 96.74

C4F8 98.7 116 5 0.631 1.523 5 96.80

C5F8 96.8 116 5 0.631 1.523 5 94.97

CH2F2 98.9 116 5 0.631 1.523 5 97.00

CH3F 99.2 116 5 0.631 1.523 5 97.33

CHF3 99.2 116 5 0.631 1.523 5 97.35

In this final rule, EPA is adopting the single default DRE for all of the non-CF4 carbonbased F-GHG shown in Table 2-2. This approach should reduce burden on reporters with 

abatement systems while still reflecting the high DRE values expected for these gases. 

Therefore, the final table of default DRE values will be those listed below in Table 2-3.
18

Table 2-3. Final default DRE values using a single combined 

DRE for non-CF4 car bon-based F-GHGs

Process Type Input Gas Default DRE

Plasma Etch and Wafer 

Clean

CF4 75

C2F6

97

C4F6

C4F8

C5F8

CH2F2

CH3F

CHF3

All other carbon- based F-GHG 60

NF3 96

SF6 97

Chamber Clean NF3 88

All other chamber clean F-GHG 60

N2O Using Processes CVD and all other N2O-using processes 60

3.0 REVISION OF MAXIMUM FIELD DETECTION LIMITS FOR THE STACK 

TEST METHOD

3.1 Introduction

This part provides technical support for the changes to the proposed maximum field 

detection limits (FDLs) under subpart I, Electronics Manufacturing, of the Greenhouse Gas 

Reporting Program. Specifically, this part provides EPA’s methodology for developing revised 

maximum FDLS, based on comments on the proposed amendments to Subpart I and using the 

data available. 

The FDL is the lowest concentration at which an F-GHG can be detected during a 

specific field measurement. The maximum allowed FDL is the concentration at which an F-GHG 

should be detectable when the method is conducted properly and the analytical instruments are 

used correctly and of reasonable quality. Maximum FDLs are specified to ensure that the field 

measurements of F-GHG emissions are of adequate accuracy and precision, and that the fraction 

of total emissions that are below the FDL (and which have to be assumed to be one-half the 

FDL) is minimized. EPA Method 320 is greatly enhanced by the specification of maximum 

FDLs because the FDLs achieved by a method and analytical instruments can have a significant 

impact on the quality of the measurements. Maximum FDLs are necessary because if the FDL 

for a F-GHG is too high, measurements may miss a relatively large fraction of the fab’s 

emissions of that F-GHG that may occur at concentrations that are lower than what is detectable 

by the instrumentation. This results in the uncertainty of the emission estimates being

correspondingly high.

Commenters on the proposed amendments (77 FR 63538) indicated that the maximum 

FDL values in Table I-10 of the proposed amendments to subpart I have been achieved in very 

limited circumstances with specifically enhanced FTIR measurement systems. The commenters 
19

noted that stack testing at three fabs was completed in support of the proposed testing alternative 

and the emissions reports from these tests revealed that the proposed maximum FDLs were not 

always met. The commenters recommended that the maximum FDLs be increased by a factor of 

five to avoid limiting the number of available testing contractors with enhanced measurement 

equipment and to avoid rendering test results invalid if the FDLs exceeded the maximum 

allowed FDLs.

In light of these comments, EPA further examined the FDLs that have been achieved at 

three semiconductor facilities (see test reports for Intel, IBM, and Texas Instruments available in 

docket EPA-HQ-OAR-2011-0028) and correspondingly analyzed potential changes to the

maximum FDLs for subpart I.

3.2 Review of Proposed Maximum FDLs

EPA acknowledges the industry commenters’ assertion that two of the three facilities that 

submitted information on FDLs used enhanced FTIR technology during stack testing and that not 

all stack testing contractors have the capability to perform these enhanced FTIR measurements. 

The EPA re-analyzed the available information for the three semiconductor facilities to assess 

the FDL levels that were achievable by the facility using other accurate and well-maintained, but 

not enhanced, FTIR,. The FTIR equipment used by these three facilities is anticipated to be 

representative of what would be used by the field of reporters and represent accurate and wellmaintained equipment in the industry.

EPA first examined the FDLs achieved for each analyte based on data from the stack test 

reports for the three semiconductor facilities. Using these data, EPA considered the standard 

deviation between the FDLs achieved at each facility, as well as the percent differences between 

the two facilities using the enhanced FTIR method (Facilities A and B in Table 3-1) and the third 

facility, which used standard FTIR procedures (Facility C in Table 3-1). 

Table 3-1. Differences Between Facility Field Detection Limits 

Analyte

FDLs Achieved by Facility 

(ppbv)

Facility 

A and B 

Average 

FDL 

(ppbv)

Average 

FDL of 

All 

Facilities 

(ppbv)

St. Dev 

of All 

Facilities 

(ppbv)

Percent 

Differencec

(Facility A 

and B)

Percent 

Differenced

(Facility A and B 

Average & 

Facility C FDL)

Facility 

Aa

Facility 

Ba

Facility 

Cb

CF4 n/a 0.889 3 0.9 1.9 237%

C2F6 2 0.962 15.8 1.5 6.3 8.3 -52% 967%

C3F8 1.5 1.5 1.5

C4F6 2.6 4.7 2.6 3.65 81%

C5F8 0.8 0.8 0.8

cC4F8 0.8 1.249 7.2 1.0 3.1 3.6 56% 603%

CH2F2 3.5 29 3.5 16.25 729%

CH3F 34.7 34.7

CHF3 n/a 1.06 12.2 1.1 6.6 1051%

NF3 3 0.886 5.5 1.9 3.1 2.3 -70% 183%

SF6 0.1 0.802 1.7 0.5 0.9 0.8 702% 277% a Facilities A and B used enhanced FTIR measurement techniques.
20

b Facility C used standard FTIR measurement techniques.

c This is determined by the equation: [(Facility B FDL) –(Facility A FDL)/(Facility A FDL)*100% 

d This is determined by the equation: [(Facility C FDL) - (Facility A and B average FDL)]/(Facility A and B average 

FDL)*100%

Based on this analysis, EPA concluded that although there were some differences 

between the FDLs achieved by the two facilities using enhanced FTIR (Facilities A and B), there 

were generally significant differences between the FDLs achieved for specific F-GHGs by the 

facilities using enhanced FTIR equipment (Facilities A and B) and the facility using standard 

FTIR equipment (Facility C). As such, EPA determined that the proposed maximum FDLs could 

be too low to be achieved by facilities not using enhanced FTIR equipment. 

In the proposed rule, the GWP of the corresponding gases was used to determine the 

overall effect on emissions (in CO2e) of different maximum FDLs. To determine the maximum 

FDLs for the final rule, EPA also considered how the maximum FDLs in the October 16, 2012 

proposed rule and the FDLs achieved by Facility C translated into corresponding F-GHG 

emissions (in CO2e). To determine these emissions, the EPA used the known molecular weights 

for each gas, an assumed fab-wide gas stack flow rate, and simple unit conversions.

Table 3-2 presents the original analysis of how the proposed maximum FDLs translate 

into corresponding F-GHG emissions at the proposed maximum FDLs at an example facility. 

Table 3-3 presents EPA’s analysis of how the FDLs achieved by Facility C translate into 

corresponding F-GHG emissions.

Table 3-2. Emissions at Pr oposed Maximum Field Detection Limits

Analyte

Proposed

Maximum

FDLa (ppbv)

Molecular 

Weight 

(g/mole)

Assumed 

Fab-Wide 

Flow rate 

(scfm)

Emission 

rate (mt/yr) GWP

Emission 

rate 

(mtCO2e/yr)

CF4 5 88 150,000 0.041 6,500 266

C2F6 5 138 150,000 0.064 9,200 590

C4F8 5 200 150,000 0.093 8,700 808

CH2F2 10 52 150,000 0.048 675 33

CHF3 5 70 150,000 0.033 11,700 380

NF3 5 71 150,000 0.033 17,200 567

SF6 1 146 150,000 0.014 23,900 324

Total 2,968 a

From 77 FR 63538 (October 16, 2012). 

Table 3-3. Facility C Emissions at Achieved Field Detection Limits

Analyte Measured

FDL (ppbv)

Molecular 

Weight 

(g/mole)

Assumed 

Fab-Wide 

Flow rate 

(scfm)

Emission 

rate (mt/yr) GWP

Emission 

rate

(mtCO2e/yr)

CF4 3 88 150,000 0.025 6,500 159

C2F6 15.8 138 150,000 0.20 9,200 1,863

C4F8 7.2 200 150,000 0.13 8,700 1,163
21

Analyte Measured

FDL (ppbv)

Molecular 

Weight 

(g/mole)

Assumed 

Fab-Wide 

Flow rate 

(scfm)

Emission 

rate (mt/yr) GWP

Emission 

rate

(mtCO2e/yr)

CH2F2 29 52 150,000 0.14 675 95

CHF3 12.2 70 150,000 0.079 11,700 928

NF3 5.5 71 150,000 0.036 17,200 624

SF6 1.7 146 150,000 0.023 23,900 551

Total 5,383

It should be noted that the maximum FDLs included in the proposed rule were based 

primarily on the technical achievability of those detection levels. To determine maximum FDLs 

for the final rule that are achievable by facilities using standard FTIR techniques, EPA 

determined at what level the maximum FDLs would be achievable by Facility C. EPA examined 

maximum FDLs based on raising the proposed FDLs by three, four, and five times (shown in 

Table 3-4). Based on this review, EPA determined that Facility C could achieve maximum FDLs 

based on four times the proposed FDLs. 

Table 3-4. Comparison of Facility C Achieved FDLs with Proposed Values

Analyte Facility C 

Achieved FDLs Proposed FDLs Proposed FDLs x 3 Proposed FDLs x 4 ProposedFDLs x 5

CF4 3 5 15 20 25

C2F6 15.8 5 15 20 25

C3F8 Not Measured 5 15 20 25

C4F8 7.2 5 15 20 25

CH2F2 29 10 30 40 50

CHF3 12.2 5 15 20 25

NF3 5.5 5 15 20 25

SF6 1.7 1 3 4 5

C4F6 4.7 5 15 20 25

C5F8 Not Measured 5 15 20 25

EPA determined that it was not necessary to increase the maximum allowed FDLs by a 

factor of five to establish levels that could be achieved by testing companies using EPA Method 

320. The analysis of data and information provided to EPA on this topic demonstrates that an 

increase by a factor of four results in achievable maximum FDL values. These final FDLs

(shown in Table 3-5) achieve the necessary balance between achievable FDLs and minimum 

uncertainty in the emission measurements derived from stack testing. All of the final maximum 

FDLs are higher than the FDLs achieved at the three facilities during their stack testing and are 

expected to be achievable by sources using the stack test method.
22

Table 3-5. Final Maximum Field Detection Limits (Table I-10 in Subpart I)

Analyte CF4 C2F6 C3F8 C4F6 C5F8 c-C4F8 CH2F2 CH3F CHF3 NF3 SF6

Other Fully 

Fluorinated 

GHGs

Other 

Fluorinated 

GHGs

Maximum FDLs (ppbv) 20 20 20 20 20 20 40 40 20 20 4 20 40