Outstanding Questions / Topics from SIA / EPA Discussions as of April 24, 2012

Response as of April 26, 2012

The following represents the list of questions / topics EPA believes still need to be resolved as 

part of our discussions and workplan with SIA leading to a rule proposal revising subpart I. We 

ask that SIA review this document and add any additional questions / topics SIA believes are 

still unresolved. The goal of this document is to cover all outstanding questions / topics by 

Monday, April 30th.

Outstanding questions for SIA from 4/19 call:

Apportioning model verification:

1. Please provide a suggested definition of "representative of normal operation". 

Industry response in progress.

DRE summary paper:

1. Please provide an outline / bullet points that describe what content from the ISMI 

guidelines SIA is proposing to include in subpart I with regard to measurement of sitespecific DRE values. Please also provide the purpose / use of each guideline method in 

the context of subpart I.

Responded to in prior submittal “Questions for 4-19-12...”

2. Can SIA provide, for the chamber clean NF3 DRE tests, which abatement system tests 

operated outside of the manufacturer's recommendations and which ones did not? 

Please also provide information on what caused the unit to operate outside of allowed 

parameters (i.e. high flow) for the cases where manufacturer's recommendations were 

not observed.

Responded to in prior submittal “Questions for 4-19-12...”

Outstanding question for SIA from 4/23 call:

1. N2O default emission factor – EPA has noted the average N2O emission factor from 

data submitted by SIA is above 1, which suggests N2O is being generated as a 

byproduct. Would SIA prefer to use one default EF for all N2O emissions, which would 

theoretically be above 1, or use two default EFs – one for input N2O and one for 

byproduct N2O? The industry prefers one default factor. If the latter, can SIA 

elaborate on which semiconductor processes are expected to generate N2O as a 

byproduct? The industry is uncertain whether or not emission factor values above 

1.0 are due to measurement errors or N2O byproduct formation; however, we are 

unaware of semiconductor manufacturing processes that generate N2O as a 

byproduct. 

In our March 7, 2012 response to EPA’s Stack Question 1, we indicated that the 

measured stack N2O EF for the fabs were universally anomalous, that N2O Limits 

of Detection are relatively high because the FTIR’s used for stack testing have 

largely been tuned to optimize for F-GHG, and because the ambient concentration

of N2O is high. Consequently we recommended the use of a default EF for N2O. 
Based upon the data that we have, the cause for the large range in N2O EF is not 

clear. Analysis of multiple years of one semiconductor company’s (Company A) 

N2O stack measurement data shows an anomalous high emission factor in 2005. 

This high emission factor is believed to be due to incorrectly recorded N2O usage 

data (2005 usage is 3-4X lower than usage in 2004 and 2006). If calculated N2O EF 

for 2006-2011 are averaged, the Intel EF=1.2. A second semiconductor company B 

tested for N2O in accordance with Method 320 and submitted data showing Fab 1 

EF=0.34 in March and EF=0.66 in August. Company B’s Fab 1 average EF=0.5. 

The average of Company A’s and B’s EF=1.02.

Because it is not clear that the large N2O EF are due to byproducts, and also 

because there doesn’t seem to be any data supporting a technical approach for 

assigning a distinct EF for feed N2O vs. byproduct N2O, we recommend a single 

factor. 

Based on fact that the average EF for Company A and B is 1.02 and because there 

is doubt that N2O is generated as a byproduct, we would propose: 

a) Assume a default EF=1.0; 

b) If industry develops additional data to support an alternative N2O emission 

factor, it will be introduced before the end of the comment period or as part of 

an emission factor update report.

Summary of other outstanding topics & current status/task:

1. DRE

a. Infrequently used gas threshold / clause – EPA to send feedback to SIA for 

review

b. Revisit clean NF3 default DRE – SIA to send revised data; EPA to review

c. Process to validate an alternative DRE measurement method – EPA to send 

draft to SIA for feedback

d. Recordkeeping, requirements suggestions on page 1 of DRE summary response

– EPA to provide response to SIA’s feedback

2. Stack method – Process to validate an alternative stack testing method – SIA to provide 

comments on EPA draft text

3. Etch / Default EFs method – no outstanding issues