# Technical Support for Accounting for Destruction or Removal Efficiency for Electronics Manufacturing Facilities under Subpart I Office of Air and Radiation, U.S. Environmental Protection Agency
August 2012August 2012 Subpart I DRE Technical Support

Page 2 of 14 **1. Introduction**  This document provides technical support for the proposed changes to the provisions to account for controlled emissions associated with point
-of
- use (POU) abatement systems under subpart I, Electronics Manufacturing, of the Greenhouse Gas Reporting Program (GHGRP)
. Specifically, the Environmental Protection Agency (the EPA) is proposing t he following changes to subpart I : 1) revising the default destruction or removal efficiency (DRE) value for semiconductor manufacturing facilities to establish new default DREs grouped by gases and process types (etch and chamber cleaning) ; 2) providing facilities multiple options to directly measure abatement system DRE s ; 3) revising the provisions that specify the number of abatement systems that must be tested, and the required frequency of abatement system testing to determine fa b
- specific DRE values (i.e., the random sampling abatement system testing program , or the RSASTP ) ; and 4) expanding the provisions for ensuring proper abatement systems installation, operation, and maintenance to include a n on - site a maintenance plan for abatement systems
. Th is document was developed using information from two sources. The first is the 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 ( hereafte r, the N ovember 2010 TSD ) , available in docket EPA- HQ
- OAR
- 2009
-0927 . The second is non - confidential materials submitted to the EPA by the Semiconductor Industry Association (SIA). These materials are listed at the end of this document. **2. Revised Default DRE**  **Values** The December 2010 subpart I rule provided all electronics manufacturing facilities the option to use a default DRE value (60 percent) so long as abatement systems for which the default DRE was being applied were designed to abate fluorinated greenhouse gases (F
- GHGs) and/or nitrous oxide (N 2 O) and the systems were properly installed, operated, and maintained (see Section 4). The default DRE of 60 percent was developed using data from the EPA DRE measurement studies done through the EPA PFC Red uction/Climate Partnership for the Semiconductor Industry . The data set from these studies was limited and relatively small in comparison to the DRE data set SIA submitted to the EPA after subpart I was finalized (see November 2010 TSD and SIA, 2012a for t he data sets ) . The SIA data set represents the most comprehensive DRE database the EPA has seen to date . The DREs provided by SIA were based on measurements made by two semiconductor device manufacturers. The DRE measurements for the most part (126 tests) were done in 2011 by one company according to Method 1 of the EPA Protocol for Measuring Destruction or Removal Efficiency (DRE) of Fluorinated Greenhouse Gas Abatement Equipment in Electronics Manufacturing (hereafter the EPA DRE Protocol, available in docket EPA
- HQ
OAR
- 2009
- 0927)
. A small portion of the DRE data (19 tests) submitted by SIA represents tests done over the time period 2003 to 2011, using a method comparable to Method 2 in the EPA DRE Protocol. SIA analyzed its DRE data to determine if the re were differences in DREs due to the measurement method used. Based on this analysis the SIA concluded that “at most, any test method difference would appear to be very small.” (SIA, 2012a)August 2012 Subpart I DRE Technical Support

Page 3 of 14 Using the SIA DRE dataset and available EPA DRE data , the EPA is proposing to revise the subpart I default DRE for semiconductor manufactur ing processes . The revision would provide multiple default DREs grouped by gas and process type as opposed to one default factor for all gases and process types
. 1 The EPA is proposi ng this change for several reasons . First, the EPA now has access to a larger DRE database that covers more gas and process combinations . Second , some gases are more difficult to abate than others due to differences in the strength of chemical bonds, which can now be reflected in the default DREs due to the broader DRE database . For example CF 4 is known to be harder to abate in combustion systems (the most commonly used abatement systems per SIA, 2012a) than other F - GHG s, which will typically result in a lo wer DRE for CF 4 (Beu, 2005). Finally, abatement system DREs are dependent on inlet and outlet system flows and i t is known that process flow rates are higher for chamber clean processes than etch processes (larger precursor flows and dilution factors) , which — for a given type of abatement system — will typically result in lower DREs for chamber cleaning than for etch
. 2 To assess how to establish new default DREs for semiconductor manufacturers the EPA analyzed the DRE data and supporting information submitt ed by SIA and data from the November 2010 TSD
. Etch Process Type Default DREs Table 1 presents a summary and analysis of the available etch DRE data SIA submitted to the EPA and DRE data available through the EPA DRE measurement studies (SIA, 2012a and November 2010 TSD ). The EPA analyzed the etch DRE data by looking at the mean and the standard deviations of the data by gas. To analyze potential default DREs the EPA evaluated the value of arithmetic mean minus two standard deviations of the population. This conservative method was employed to account for the limited representativeness of the SIA DRE dataset: while the number of data points is relatively large, the data comes almost exclusively from one abatement system manufacturer (i.e. a pproximately 97 percent of the systems tested were manufactured by one abatement system supplier )
. B ased on SIA abatement systems inventory information , the EPA estimated that over 70 percent of systems installed in the US are manufactured by that one supplier . F ive othe r suppliers are also in the market in the US; about three percent of the field DRE performance data are for systems from some combination of these five manufacturers (SIA, 2012a). DRE performance can vary depending on the specific design of each manufacturer, which is often proprietary. Consequently, a conservative approach was used to estimate the DRE.

1 The EPA does not have information to support a revised default DRE(s) for electronics manufacturers outside of semiconductor manufacturing; however, the EPA is specifically seeking comment in this proposal on additional information that ma y be available to revise default DREs. Any new data provided would be analyzed in a similar manner to the data analysis provided in this memo. 2 See SIA, 2012c and SIA, 2012d.August 2012 Subpart I DRE Technical Support

Page 4 of 14 **Table 1. Summary and Analysis of All Available**  **Etch DRE Measurement Data (SIA, 2012a**  **and 2012e and November 2010 TSD**  **) Gas**  **Mean**

**(Percent) Standard**  **Deviation**

**(Percent) Number of Data** 

**Points Available Mean Less Two** 

**Standard Deviations (Percent)**  Etch CF 4 63.93 32.19 34 - 0.45 C 2 F 6 99.00 NA 1 99.00 C4 F 6 99.06 0.28 5 98.50 C4 F 8 98.85 0.66 14 97.53 NF 3 99.27 0.47 14 98.32 SF 6 99.14 0.53 4 98.08 CH 2 F 2 98.94 0.73 16 97.49 CHF 3 99.18 1.54 19 96.09 NA: Standard deviation could not be calculated because only one data point was available. Due to the similarities of the calculated etch DREs (as seen in Table 1) for many gases used in etch processes 3, the EPA is proposing to group C 4 F 6, CHF 3, C4 F 8, NF 3, SF 6, and CH 2 F 2 used in etching into one DRE category and assign one average DRE of 98 percent. A DRE of 98 percent was selected as it was the approximate average of all of the aforementioned gas DREs. The a vailable DRE measurements for CF 4 emissions from etch processes varied across a wide range of values as indicated by the large standard deviation for the total available CF 4 etch DRE data set seen in Table 1. This variability was due to underperforming aba tement systems resulting from operating outside manufacturers’ specifications. Following the same guidelines used to establish the initial subpart I DRE (see November 2010 TSD), the EPA is proposing to remove some of the available data from the CF 4 etch d ata set because the data represent the DREs of systems that were not properly installed, operated, and/or maintained. 4 Based on an EPA request, SIA identified the CF 4 measured DREs that were associated with systems that were not properly operated. A pproxim ately half of the available CF 4 measured DREs were removed from the dataset based on SIA input (SIA, 2012f). T his resulted in 15 of the 34 CF 4 etch DRE measurements summarized in Table 1 being removed from the dataset that could be used to develop a default DRE . Given that such a high percentage of data were collected under operating conditions that do not meet the requirements in the current subpart I (i.e., systems that were not abating CF 4 as expected because of improper operation and maintenance) , the EPA has concerns about the reliability of the entire data set. Therefore , the EPA is proposing to maintain the current DRE of 60 percent for CF 4 for the etch process type.

3 Etch DREs would apply to the combined wafer clean/etch process type. Please refer to Technical Support for Modifications to the Fluorinated Greenhouse Gas Emission Estimation Method Option for Semiconductor Facilities under Subpart I for a discussions on the combining of these process types. 4 Subpart I contains requirements for p roper installation, operation, and maintenance of abatement systems, so the default DREs needs to also represent DREs of properly installed, operated, and maintained systems.August 2012 Subpart I DRE Technical Support

Page 5 of 14 Little (i.e., one data point) or no DRE data were available for four gases emi tted from etch processes, C 2 F 6, CH 3 F, C 3 F 8 and C 5 F 8 . Therefore, the EPA is proposing to assign default DREs for these gases used in the etch process type on the following basis:
 C 2 F 6 : one DRE measurement of 99.0 percent is available for this F
- GHG; however, in the absence of additional DRE measurements, the EPA is proposing to assign a default DRE of 60 percent to C 2 F 6, the same DRE for CF 4, because C 2 F 6, like CF 4, is also known to be difficult to abate
. B oth are highly fluorinated with no C
- H bonds or C = C double bonds (Tsang et. al., 1998) , making t hese compounds relatively harder to abate than most other F
- GHGs .  CH 3 F, C 3 F 8, and C 5 F 8 : no DRE data are available for these F
- GHGs, so the EPA is proposing to maintain the previous subpart I DRE value of 60 pe rcent. Chamber Clean Process Type Default DREs As can be seen by the large standard deviations in Table 2 , a wide range of NF 3 DREs for chamber clean were measured due to underperforming abatement systems that were not properly installed, operated, and/or maintained (SIA, 2012e)
. 5 T he EPA analyzed the chamber clean DRE data to determine a default DRE using the mean DRE less two standard deviations for the same reasons as stated above for the etch default DREs
. **Table 2. Summary and Analysis of All**  **Available NF 3**  **Chamber Clean DRE Measurement Data (SIA,**  **2012a) Gas**  (Cleaning Sub
-type) **Mean**

**(Percent) Standard Deviation** 

**(Percent) Number of Data** 

**Points Available Mean Less Two**  **Standard Deviations**  **(Percent)** Chamber Clean NF 3 ( All sub
-types combined ) 88.72 14.61 49 62.22 NF 3 (I n - Situ Plasma) 88.67 16.71 22 61.04 NF 3 (I n - S itu Thermal) 98.90 NA 1 NA NF 3 (R emote Plasma ) 88.37 13.08 26 62.22 NA: Only one data point available, standard deviation could not be calculated. As was done for CF 4 etch DREs, the EPA requested that SIA identify the NF 3 chamber clean DREs that were associated with abatement systems that were not properly installed, operated, and/or maintained. Removing the four DRE data points that represent ed underperforming systems (as detail ed in SIA, 2012e) resulted in the DRE values shown in Table 3 below.

5 Subpart I contains requirements for proper installation, operation, and mainten ance of abatement systems, so the default DREs should represent DREs of properly installed, operated, and maintained systems.August 2012 Subpart I DRE Technical Support

Page 6 of 14 **Table 3. Analysis of Revised NF 3**  **Chamber Clean DRE Dataset (SIA, 2012a and SIA, 2012e)**

**Gas** (Cleaning Sub
-type) **Mean**

**(Percent) Standard Deviation** 

**(Percent) Mean Less Two** 

**Standard Deviati**  **ons (Percent)**  NF 3 (All sub
-types combined) 92.18 8.63 74.93 NF 3 (In
- Situ Plasma) 93.23 7.94 77.35 NF 3 (In
- Situ Thermal) 98.90 NA NA NF 3 (Remote Plasma) 91.03 9.27 72.48 NA: Only one data point available, standard deviation could not be calculated. In reviewing the results displayed in Table 3 , the EPA decided to propose a default DRE for NF 3 of 75 percent for the entire chamber clean process type , and to not propose specific default DREs for process sub
-types . This was done for simplicity and becau se of the close proximity of the DREs for in
- situ plasma and remote plasma clean, which are the most commonly used chamber clean processes in the industry. For all other gases used in chamber clean , the EPA is proposing to maintain the previous subpart I default DRE of 60 percent because no other data are available to support proposing revised DREs. N 2 O Default DRE Because no data are available to support establishing a default DRE for N 2 O used in chemic al vapor deposition or other processes, the EPA is proposing to maintain the previous subpart I default DRE of 60 percent for N 2 O emissions . If additional DRE data are submitted to the EPA in response to this proposal , they will be evaluated in a similar manner to the DRE analyses above. Revised Default DRE Summary A summary of the proposed, expanded semiconductor manufacturing default DREs is provided in Table 4 . **Table 4**  **. Proposed DRE Default Values**  **for Semiconductor Manufa cturing Facilities**  **Process Type/Gas Proposed Default**  **DREs Etch**  CF 4, C 2 F 6, C 3 F 8, C 5 F 8, CH 3 F (and all other F
- GHGs not listed in the subsequent row ) 60% CHF 3, CH 2 F 2, C4 F 8, NF 3, SF 6, C4 F 6 98 % **Chamber Clean** NF 3 75 % All other gases 60 % **N 2** **O** CVD and all other N 2 O
- using processes 60 %August 2012 Subpart I DRE Technical Support

Page 7 of 14 The EPA is proposing that the revised default DRE values only apply to semiconductor manufacturing facilities because the EPA did not receive any additional data for other electronics manufacturing facilities to support a change. For the use of abatement systems at other electronics manufacturing facilities, the EPA is proposing to maintain the previous subpart I default DRE of 60 percent. **3. Measurement of**  **Fab -** **Specific DREs** As an alternative to using default DREs, the Dec ember 2010 subpart I provides all electronics manufacturing facilities the option to measure and develop fab
- specific DREs to use in place of the default DREs
. The EPA is proposing to amend the provisions for measuring DRE to be more flexible and to require less frequent abatement system testing. **3.1. Methods for Measuring**  **Fab -** **Specific DREs** The November 2010 TSD and the EPA DRE Protocol contain detailed discussions on the justification for the required adherence to the EPA DRE Protocol for proper measurement of fab
- specific DREs. However, based on new information that SIA submitted to the EPA on an alternate method for measuring total volume flow (TVF) of an abatement system , the EPA is proposing to amend the provisions for measuring fab
- specific DREs for all facilities covered under subpart I
. 6 The EPA is proposing to allow facilities to use a method for determining TVF of gas through the abatement system that is an alternative to the method outlined in the EPA DRE Protocol which suggests the use of quadrupole mass spectroscopy (QMS) . The proposed alternat ive method would consist of injecting a non - native polar tracer gas in to the abatement system outlet stream and measuring the downstream tracer gas concentration using Fourier transform infrared (FT IR) spectroscopy to determine TVF . This proposed alternative , which is a lower cost option than using a QMS
- based method (ISMI, 2010) , was tested by SIA on three abatement systems at one semiconductor manufacturing facility. The results of the tests compar ing the use of the FTIR
- based and QMS
- based methods are presented in the International SEMATECH Manufacturing Initiative (ISMI) Technology Transfer #10095115A
- ENG Comparison of Fourier Transform Infrared (FTIR) and Quadrupole Mass Spectroscopy (QMS) Method s for Determining POU Abatement System Effluent Flow
. The EPA reviewed th e method comparison and concluded that t he results of these tests adequately showed that using the suggested alternat ive FTIR method was suitable for determining dilu tion across an abatement system , provided that the injected tracer gas is well
- mixed at the abatement system exit stream sampling location (ISMI, 2010) , or that the sampling procedure accounts for any stratification (lack of mixing)
. Therefore t he EPA is proposing to inc lude this alternate FTIR method as an option in Appendix A to subpart I , with an additional procedure to ensure that the sampling location and procedures account for the fact that the tracer gas may not be well mixed . As discussed above , e nsuring adequate mixing is essential to provide accurate results, but can sometimes be difficult to achieve due to the short duct lengths commonly found downstream of abatement systems . Ideally, sampling would be done well downstream of the abatement system to ensure compl ete mixing . 6 Total volume flow is a parameter used to calculate the dilution across an abatement system. Taking into account dilution is crit ical to properly measuring abatement system DREs. Failure to account for the effects of dilution may lead to DREs for CF 4 that can be off by as much as a factor of 20 to 50 and DREs for C 2 F 6 that can be off by a factor of up to 10 (Burton, 2007).August 2012 Subpart I DRE Technical Support

Page 8 of 14 To demonstrate complete mixing in the abatement system exhaust stream , or to account for any stratification in the exhaust if it is present, the EPA is proposing that facilities using the alternat ive method to determine dilution should use an adaptation of section 8.1.2 of EPA Method 7E, Determination of Nitrogen Oxides Emissions From Stationary Sources (Instrumental Analyzer Procedure), in 40 CFR part 60, Appendix A
-4 . 7 This adaptation , which is also included in the proposed Appendix A to subp art I, includes the following requirements :
 The concentration of the tracer would be measured at three traverse points at 16.7, 50.0, and 83.3 percent of the diameter of the duct.  If the tracer gas concentration at each traverse point differs from the me an concentration for all three traverse points by no more than ±5.0 percent of the mean concentration, the gas stream would be considered un
- stratified and the facility would be allowed to collect samples of the tracer gas from a single point that most closely matches the mean.  If the 5.0 percent criterion were not met, but the concentration of the tracer gas at each traverse point differed from the mean concentration for all traverse points by no more than ±10.0 percent of the mean, a facility would be able to take samples from two points and use the average of the two measurements. The sampling could be performed at any two of the three points spaced at 16.7, 50.0, or 83.3 percent of the line.  If the concentration at each traverse point differed from t he mean concentration for all traverse points by more than ±10.0 percent of the mean but less than ±20.0 percent, the fa cility would take samples of the tracer gas from three points at 16.7, 50.0, and 83.3 percent of the measurement line and use the averag e of the three measurements.  If the gas stream were found to be stratified because the ±20.0 percent criterion for a three
point test were not met, the fa cility would be required to locate and sample the tracer gas from traverse points in accordance with Sections 11.2 and 11.3 of EPA Method 1 in Appendix A
- 1 to Part 60. The tracer gas concentration used for measuring flow would be determined from the average of the concentrations measured at each of the traverse points. This method has not been used in pra ctice at an electronics manufacturing facility, but it is expected to be sufficient for demonstrating complete mixing and ensuring that a concentration value used in calculations is representative of a well
- mixed stream. This is because the method outlined above is based on the EPA’s Method 7E, which has been used in practice in other applications. Also the method includes thresholds for differences in measured concentrations and contingencies for when a threshold cannot be met. This structure help s ensure that the effluent stream concentration used is representative of a well
- mixed stream at a sampling location. In addition, the EPA is also proposing to allow fa cilities to request approval to use an alternative sampling and analysis method that is not included in subpart I to measure abatement system DRE . The EPA is proposing that alternative test methods would have to be validated according to EPA Method 301 ( Field Validation of Pollutant Measurement Methods From Various Waste Media ). 8 Under this propo sal,

7 This method is based on suggestions from SIA regarding the use of the alternate methods for measuring site
- specific DREs. See SIA, 2012g. 8 Method 301 can be access at: http://www.epa.gov/ttn /emc/methods/method301.htmlAugust 2012 Subpart I DRE Technical Support

Page 9 of 14 p rior to using an alternate test method, the facility would be required to submit the method along with a proposed test plan to the EPA for review and receive approval from the EPA. This process would ensure that any method outside of those specified in subpart I are viable and appropriate. Once the EPA approves an alternate method, the method could be used by other fabs that meet the same conditions under which the alternative method was approved. The EPA would specify those conditions in the approval of the alternative method. The regulatory language that addresses this option is included in the body of the text, not in the proposed Appendix A to subpart I. Regardless of the method used to determine dilution (either using krypton and a QMS as specifie d in the EPA DRE Protocol , a polar species and a FTIR (as proposed in Appendix A of subpart I) , or an alternat ive method a pproved by the EPA ) , facilities would still be required to meet the EPA DRE Protocol performance benchmark, which is that the relative error of the true fraction emitted must be less than or equal to five percent, and to follow all other aspects of the EPA DRE Protocol with one exception. That exception is that fa cilities may use the FTIR and QMS Protocols specified in the proposed Appendix A of subpart I in lieu of the 2006 ISMI Guideline for Environmental Characterization of Semiconductor Process Equipment FTIR and QMS Protocol as required in the EPA DRE Protocol. The FTIR and QMS protocols contained in the proposed Appendix A to subpart I are modeled after the FTIR and QMS Protocols in Appendix A of the 2009 ISMI Guideline for Environmental Characterization of Semiconductor Process Equipment and reflect advancements in experience in using FTIR/QMS in the industry. Although ISMI
- SEMATECH is a common source of best practices for the semiconductor manufacturing industry, the EPA does not have any information on whether, and in what way, the modifications to the FTIR and QMS protocols in Appendix A of the 2009 ISMI Guideline would impact DRE measurements, compared to the 2006 ISMI Guideline . Therefore, the EPA is specifically seeking comment on the appropriateness of using th e 2009 ISMI G uideline as the basis for the proposed Appendix A to subpart I . **3.2. Abatement System Sampling Protocol**  The EPA is proposing to modify the random sampling abatement system testing program ( RSASTP ) in 40 CFR 98.94(f)(4)(ii) to make the required testing frequency less burdensome for faci lities that elect to measure fab
- specific DREs. Table 5 below summarizes the elements of the RSASTP as finalized in the December 2010 version of subpart I, the proposed changes to the RSASTP, and the technical justification for the modifications. **Table 5**  **. Summary of Proposed Revisions to the RSASTP**  **December 2010 Provisions Proposed Revised Provisions**  **Justification for Modification** **/Addition Required Testing Frequency**   Each year, test three systems or 20% of installed abatement systems for each class
.  Do not repeat measurements for systems measured in the previous year.  For each process type/sub
-type and gas combination , test 10% of systems in each fab annually for two years (20% total) or 20% in the first year to set a baseline average DRE for that process type/sub
-type and gas combination. The EPA is proposing to modify the RSASTP because:  The previous definition of “class” combined with the permutations of process and abatement type resulted in testing requirements representing an average of 45 percent of the total number ofAugust 2012 Subpart I DRE Technical Support

Page 10 of 14  If a DRE was measured for a particular system during the previous 2 years, the facility must use the most recently measured DRE .  If the DRE was not measured for a particular system during the previous 2 years, use the simple average of the measured DRE s for that class .  Use default DREs until DRE s have been measured for 20% of systems .  For every 3
-year period after, test 15% of the systems in the fab for each process type/sub
-type and gas combination . A fab can choose to test 15% in the first year of a 3 year period but must test at least 5 percent of the systems each year until 15 percent are tested .  The fab
- specific DRE would be calculated as the average of the first 2 years ( or first year if 20% are teste d ) and thereafter as the average of the most recent t 30% tested . abatement systems in a fab, which is higher than the 20 percent required to be tested by the RSASTP . (SIA, 2012 a)  The proposed changes would reduce testing burden by requirin g fewer tests compared to current subpart I , yet provid e sufficient information to ensure that the DRE values used represent current system performance as abatement systems age (see DRE versus abatement system age information in SIA, 2012a)
. **Definition of Class**  Class means a c ategory of abatement systems grouped by manufacturer model number(s) and by the gas that the system abates, including N 2 O and CF 4 direct emissions and by
- product formation , and all other F 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. Delete the definition of “class
. ” R equire that DRE s be determined for abatement systems based on the gas(es) that the systems abate and the process type connected to the systems, including etch/wafer clean , chamber clean, and all N 2 O using processes. The EPA is proposing to delete the definition of class because:  Testing by gas and process type/sub
-type combination would simplify apportionment and uptime calculations, and recordkeeping, and hence reduce burden.  Abatement system categories based on gas and process type combinations would be consistent with calculation methods for subpart I default emission factor based methods .  Broader categories of abatement systems would reduce the number of systems that need to be tested. **Accounting for Under** 

**- Performing**  **Abatement Systems**  **in Calculating Emissions or Ave** **rage DRE** Not specifically addressed. (If a facility uses the default DRE of 60%, the facility must certify that the system is installed, operated, and maintained according to the manufacturer’s specifications. If a facility measures the DRE of a system, they must use  If proper maintenance and operation procedures are followed, and the measured DRE of an abatement system is below the manufacturer
- claimed DRE, the data from the low DRE test would be included in calculating the fab
- specific average DRE for that gas and process combination .  If proper maintenance and operation procedures are not These provisions would be added as part of requirements for DRE measurement because they would :  Ensure that the DREs used in calculations reflect actual performance
.  Ensures measured values are used by not allowing a reporter to select the higher of the default or the measured DRE .August 2012 Subpart I DRE Technical Support

Page 11 of 14 that measurement in calculating emissions. ) followed, then the appropriate operational change or system maintenance (per th e manufacturer instructions or the fab maintenance plan) would need to be implemented, and a retest would be required that year to replace the measured value . Alternatively, the fab could use the measured value in the DRE determination and then include the same system in next year’s abatement system testing in addition to the testing of randomly selected systems . **Testing of Systems T** 

**hat May Be**  **Disruptive to Production** Not addressed. (No provisions to allow deferring testing of abatement systems if the testing would be disruptive to production.) Where testing of systems randomly selected for testing would be disruptive to production, such systems could be (a) replaced by another randomly selected system for testing, and (b) retur ned to the sampling pool for subsequent testing. If testing of a system is deferred, that system could be chosen for testing in one of the next two sampling years
. The EPA is proposing that a system cannot be returned to the pool in more than three consecu tive selections . This provision would be added to a ddress situations where testing of a specific abatement system would disrupt manufacturing productivity . IF deferred, a system could be specifically selected for testing so that production and testing could be coordinated to avoid disrupting production.

**4. Ensuring Proper Abatement System Installation, Operation, and Maintenance**  As discussed in Section 3.6.1 (Proper Installation, Operation, and Maintenance) of the November 2010 TSD, proper installation, operation, and maintenance of the abatement systems in accordance with manufacturer specifications is essential to ensuring that abatement systems are performing as expected. This concept is supported by the circumstances described in S ection 2 of this doc ument for CF 4 and NF 3, in which some DREs were lower than expected as a result of system operational and/or maintenance issues . The wide range of measured values for CF 4 used in etching and NF 3 used in chamber cleaning from the complete available DRE data set, which includes data that was removed in the Section 2 analysis, can be seen in Figure 1 below ( where ‘IS’ denotes the In
- Situ chamber cleaning technology and ‘RPS’ the Remote Plasma System, a.k.a. the remote cleaning process). The broad ranges were not typical of the DRE data provided by SIA, but were not wholly unexpected due to issues the EPA has seen with CF 4 DREs during measurement studies (see EPA 2008a and 2008b) and because of the known high flow rates of NF 3 used during remote chamber clean pro cesses (SIA, 2012c and SIA, 2012e )
.August 2012 Subpart I DRE Technical Support

Page 12 of 14 **Figure 1. Range in Measured DREs for CF 4**  **Etch and NF 3**  **Chamber Clean (SIA, 2012a)** SIA suggests the variation in flows through the abatement system that was outside of manufacturer specifications were the primary reason for the observed variation in NF 3 DREs for chamber clean processes (SIA, 2012a and SIA, 2012b). Low CF 4 DREs resulted from operating and maintaining the abatement systems outside the manufacturer specifications ; for example, system inlet/outlet volumetric flows were at higher levels than recommended by the manufacturer (SIA, 2012b). 9 More specifically, for the low CF 4 DREs associated with etch processes, it was found that operators were not complying with the manufacturers’ recommended set points for flow rate and/or pressure for fuel, oxygen, and air that should have been verified during abatement installation , and that ongoing maintenance to ensure that the systems performed as expected was not being performed . For systems that were operating as expected d uring testing for CF 4, it was determined that the flow, fuel, and oxygen settings were properly set and the flow out of the abatement system was within the recommended manufacturer range (SIA, 2012b). Abatement system manufacturers provide general guidance on operation and maintenance of their products. However, lessons learned from the EPA DRE measurement studies and from SIA’s experiences highlight the need to expand the subpart I provisions to require facilit ies to take more specific actions to ensure abatement systems are properly operated and maintained over time. Therefore, the EPA is proposing to add a requirement for facilities to develop, follow, and keep on
- site a maintenance plan for abatement systems. The EPA is proposing to require that the plan must include a defined preventive maintenance process and checklist (built on the manufacturer’s recommended maintenance program) and a corrective action process to follow whenever an abatement system fails t o operate properly.

9 High inlet flows can be caused by incorrectly setting the abatement system vacuum pump purge flows, while a high V(out) can result from several high inlet flows or from high fuel and /or combustion air flows to the combustion burner .August 2012 Subpart I DRE Technical Support

Page 13 of 14 **5. References**  Beu, L. (2005). Reduction of Perfluorocarbon (PFC) Emissions: 2005 State
-of
- the
- Technology Report, TT#0510469A
- ENG, International SEMATECH Manufacturing Initiative (ISMI), December 2005. Available at: http://www.epa.gov/hig hgwp/semiconductor
- pfc/documents/final_tt_report.pdf. 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/volume
- 50/issue
- 1/departments/industry
forum/assessing
-the
- need
-for
-fc
- abatement
- standards.html. EPA (2008a). 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). Office of Air and Radiation Office of Atmospheric Program s, Climate Change Division, U.S. Environmental Protection Agency, Washington, DC. Available at: http://www.epa.gov/highgwp/semiconductor
- pfc/documents/nec_report.pdf. EPA (2008b). Developing a Reliable Fluorinated Greenhouse Gas (F
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. CVD Abatement units with flow data
. March 6, 2012. Available in EPA docket EPA
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. Etch DRE testing with flow data
. March 6, 2012. Available in EPA docket EPA- HQ
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