April 9, 2012

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Response to EPA on the Mechanism to Update the Subpart I Emissions Factors

Outstanding Questions from Work Plan Appendices – Question #1

Over the past year, SIA has been working with its member companies and ISMI to develop a robust etch 

emissions factor database. Our efforts have greatly improved the database by significantly increasing 

the number of emission factor data points, verifying that the collected data provides coverage of the gas 

and tool types in use in the industry, and generating additional test data to improve the coverage where 

necessary. 

With these improvements, the database should now provide a sufficient basis for EPA to amend Subpart 

I to include an emissions factor reporting option. Notably, the database now covers the majority of gas 

use for the wafer size/gas using combinations of etch processing with emissions factors covering over 

99% of 2010 gas use at 12 representative fabs. It is representative of the current US manufacturing base 

for all four or five process types designated for use in the 2-factor model. 

EPA and SIA have been discussing approaches for periodically updating the database to capture new 

technology developments which either introduce new gases, new gas uses, or new equipment. One 

approach would involve SIA -- working with its member companies -- to prepare and deliver a report to 

EPA periodically – perhaps every three years. This report would address matters such as whether and 

how the gases and technologies used in 200mm and 300mm manufacturing in the U.S. have changed 

and whether any of the identified changes are likely to have changed the emissions characteristics of 

fabs compared to the conditions when the current Subpart I factors were finalized. The analysis will 

consider, but not be limited to, factors such as the implementation of new process technologies and/or 

finer line width processes in 300 mm and 200 mm technologies, the introduction of new tool platforms, 

and the introduction of new process types on previously tested platforms. 

If there is an engineering reason to believe that the emissions may have changed, the report will lay out 

a data gathering and analysis plan focused on the areas of potential change. Under such a plan, tools 

would be tested and the current factors then would be adjusted to reflect the new conditions. The 

overall significance of the changes to emissions factors would be tested by applying a provisional set of 

new factors to a representative gas use profile for a 200mm or 300mm fab (depending on which of the 

two is under reconsideration). 

SIA would envision cooperative engagement with EPA after delivering the report and before proceeding 

with the implementation of any such data gathering plan. After receiving the data, EPA would then 

need to determine whether to revise Subpart I to update the etch emissions factors. As a general rule of 

thumb, SIA believes that a revision will be appropriate if the application of the new factors to a 

representative gas use in comparison to the application of the current factors to that same gas use, 

results in a 10% or greater shift in the expected fab emissions. If EPA initiates an emissions factor 

update, SIA will work with its member companies to collect any additional emissions test data needed to 

complete the update.

The report also would address the status of the industry’s efforts to implement 450 mm technology. As 

450mm tool emissions test data become available, this report will compare the emissions of 450mm 

tools to the comparable factors in Subpart I for 300mm. In SIA’s view, derivation of new factors specific 

to 450mm should not be initiated until 450mm is in use in several fabs to avoid undue burden on a 

single facility and to assure data are more representative of the industry (rather than a single fab or 
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company). If EPA initiates action to create separate 450mm factors, SIA will work with its member 

companies to collect any additional emissions test data needed to establish the 450mm factors.

EPA will need to include several provisions in Subpart I to facilitate compliance during implementation of 

the data gathering plan and evaluation of the need for Subpart revisions:

 New Gas Default Factors: To address the possibility that a new gas is introduced before EPA is 

able to adopt applicable emissions factors, we want to have conservative default factors 

available for use. Therefore, when a new fluorinated greenhouse gas is introduced in 

semiconductor manufacturing which does not have specific emission factors in Subpart I, we 

recommend that the highest emission factor for an F-gas in the wafer size/use category that is in 

Subpart I be applied to any new gas until Subpart I emission factors are adopted for that gas.

 450 mm Technology Default Factors Based on 300 mm: While the industry’s effort to develop 

and commercialize 450mm technology is intense, commercial application of 450mm technology 

is unlikely to occur before 2017. While 450mm is a major advancement for the semiconductor 

industry, the advancement is more related to the scale of production rather than the gases and 

processes used in production. When 300mm manufacturing was introduced, both the scale and 

the process chemistries were changed. The outlook for 450mm is that the change is in scale 

rather than process chemistry. Therefore, we propose that the rule indicate that the 300mm 

factors will be applied to 450mm fab operations until such time as the agency determines that 

450mm is becoming significant in the US and its emissions are sufficiently different from 300mm 

such that new factors for 450mm need to be adopted. This approach is rational based on 

industry experience with the transition from 200 to 300 mm manufacturing, where the 

emissions factor data set shows that 300 mm emissions factors were either consistent with 200 

mm factors or were reduced through gas processing improvements. Extrapolating to 450mm, it 

is expected that initial use of 300 mm emissions factors for 450 mm manufacturing will provide 

a conservative estimate of F-gas emissions. 

SIA is open to exploring with EPA the best mechanism for memorializing this periodic report approach to 

etch emissions factors. We recognize that it would be possible to include a requirement in Subpart I for 

each covered facility to provide data which then could be satisfied on a facility’s behalf via the SIA 

report. Crafting such a requirement, however, would pose potentially significant challenges in terms of 

scope and enforceability. Thus, reliance on a different, non-rulemaking mechanism, such as a 

memorandum of understanding, may prove the better option.