Questions Generated from SIA/EPA Conference Calls and
Outstanding Questions from Work Plan Appendices
The following are questions raised during recent SIA/EPA conference calls or remaining
questions from the SIA/EPA work plan appendices for which EPA is awaiting a response from
SIA. Please note that only outstanding questions are listed below. This list does not include
questions that have been resolved.
Questions / Clarifications:
1. Updating emission factors: Can SIA outline the mechanism and timing they propose
EPA use to collect a representative data set to inform emissions factor updates for their
industry?
2. CHF3 emission factors: In Table 1-3 of the 3/7/12 stack response, SIA identifies CHF3
as one of the principal gases, but EPA notes that emission factors are not listed for this
gas. Can SIA provide emission factors for CHF3 in Table 1-3? If not, please provide an
brief explanation regarding why CHF3 emission factors are not available.
3. Appendix A remaining question: From the “G. Abatement System Uptime” section of
Appendix A in the work plan – Question 2 - EPA understands that SIA would like to
address interlocked abatement systems explicitly in Subpart I. Please provide a
proposed definition for “interlocked abatement systems”, and describe how a facility
would document that it has such systems.
SIA did not directly respond to EPA’s request for a definition of and method to document
interlocked systems in its February 3, 2012 response to the Appendix A questions due to the
fact that SIA member fabs use several approaches to managing abatement system failures,
of which one approach is represented by interlocked systems. Instead, SIA has proposed a
definition for abatement system down time (tpd) and manufacturing equipment uptime (top)
which allows fabs to account for the type of abatement system failure management used at
their respective fab and accurately represent the time that manufacturing equipment are
operating with the attendant abatement system in operation or off-line. In the case of
systems where the abatement system is interlocked with the manufacturing equipment, the
manufacturing equipment operating time will be reduced by the time the tool is not operating
due to the abatement system being inoperative. Where the systems are not interlocked,
there will be no reduction in the tool operating time and the abatement system downtime will
be the full period of time that the abatement system is inoperable. In all cases, abatement
system downtime events can be tracked using fab monitoring systems and data collected
and reported as required in 98.97(g).
A definition of an interlocked abatement system is provided below to assist EPA in
understanding how the interlocked system operates, but SIA does not feel that this definition
needs to be included in the revised rule.
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Interlocked Abatement System: An abatement system defined as being “interlocked” with
the manufacturing tool or tools that it is abating when a failure of the abatement system
causes either immediate cessation of wafer processing on the tool or shutdown of the tool
upon completion of the processing of the wafer(s) currently in the chamber. When an
Interlocked Abatement System is present, the tool will not be available for processing until
the abatement system alarm has been cleared and the abatement system is operational.
4. Appendix C remaining questions:
a. Question 1a - Can SIA explain why the CF4 and NF3 DREs were low on the
malfunctioning units?
To provide some perspective for the answer to this question, SIA wants to reiterate
the findings detailed in the abatement briefing paper (120110 SIA abatement briefing
paper.pdf) and provide some details on how the tested abatement units in question
are configured. Relative to performance, the tested abatement units did perform to
the expected DREs for F-gases used in etch, with the exception of CF4, and for the
abatement of NF3 from chamber clean processes. For NF3, only three of 36 units
had a low DRE, with a significant majority of the units were performing in accordance
with the manufacturer’s expected DREs.
EXPLANATION OF COMBUSTION SYSTEM OPERATION AT THE TESTING
FACILITY
In order to understand the analysis of the low DREs, it is helpful to provide a brief
explanation on the configuration of the combustion systems on the tested abatement
units. Each etch abatement unit can support up to six etch chambers, and each
chamber has an individual exhaust line which flows to the abatement unit. The
exhaust from each individual chamber is mixed with fuel and O2 and combustion is
initiated just prior to the main combustion chamber of the abatement unit. Most
abatement units support three or four chambers. Each of the individual chamber
exhaust lines feed into the main combustion chamber, which has a burner which
receives fuel and combustion air (as opposed to O2) to maintain a combustion flame.
Each process chamber has an exhaust gas flow which consists of the process
gases, the purge nitrogen and eventually, the added fuel and O2 flows. This total
flow in each individual chamber line, of which there can be a total of six, is the V(in)
discussed below. Additional flow is generated in the combustion chamber through
the addition of the fuel and combustion air in the burner. The sum of the V(in) of the
chamber lines and the fuel and combustion air flow to the combustion chamber
burner constitute V(out).
SIA v. EPA, (D.C. Cir. No. 1024) Privileged and Confidential, For Settlement Purposes Only
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This description is specific to the configuration of the abatement systems installed at
the testing facility. Other facilities may use this configuration where abatement units
support multiple chambers, but a facility may also use a different configuration which
supports a single process chamber. Other manufacturer’s equipment may only
support a single chamber or use a different system configuration to support multiple
chambers. There are also abatement units which use plasma technology, which will
have different flows and a different set of control parameters. As such, it is not
possible to extrapolate the specifics of the corrective action analysis below to the full
inventory of abatement systems installed at US fabs.
CORRECTIVE ACTION ANALYSIS
As discussed in the March 5, 2012 document submitted to EPA, the low DREs in the
abatement units at the one testing facility were primarily the result of high inlet and/or
outlet flow at the abatement unit. High inlet flows are typically caused by incorrectly
set vacuum pump purge flows, while a high V(out) can result from several high inlet
flows or from high fuel/combustion air flows to the combustion burner. For the
abatement units used at the testing facility, both for NF3 and etch gases, the
problems were corrected by setting the various flows and/or pressures to the
manufacturer’s recommended settings.
Specifically where low DRE was found for NF3, the primary cause was high inlet
flows in the individual chamber lines into the abatement unit.
For CF4 units, in addition to the impacts of the high inlet and outlet flows, it was also
determined that manufacturer recommended set points for flowrate and/or pressure
for fuel, oxygen and air need to be verified during set-up and ongoing maintenance
to assure that the unit operates at the expected DRE for CF4.
For the abatement units that had tested CF4 DREs at or above the manufacturer’s
expected performance of 90% destruction, the corrective action investigation found
that the flow, fuel and O2 settings were properly set and the flow out of the
abatement unit was within the required range.
After a full assessment of the results of the abatement testing, it was determined that
modifications were required in the maintenance procedures to validate that the fuel,
O2, and combustion air flows and/or pressure settings were in accordance with the
manufacturer’s recommended requirements. Maintenance checklists and the training
for technicians servicing the units have been improved to more clearly define set-up
requirements that apply at the completion of initial system installation and to the
regular maintenance checks.
The equipment maintenance contractor for this facility is now able to certify that all
units will perform to specification, as required under 98.96(q)(1) and 98.97(d) of the
subpart I rule, based on the implementation of the revised procedures.
SIA v. EPA, (D.C. Cir. No. 1024) Privileged and Confidential, For Settlement Purposes Only
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It is important to note that the testing facility was in the process of performing DRE
testing and validation of the maintenance procedures to enable the facility to use site
specific DREs for emissions reporting and to be in a position to certify the
performance of the abatement units as required in the Subpart I regulations. Prior to
this testing, these abatement units were not covered by a specific set of regulatory
requirements.
b. Question 1b - Can SIA indicate whether there are any general criteria that could
be applied to ascertain whether a unit is under performing or needs service
without having to measure the abatement system DRE?
After discussions and evaluation of available information from fabs with abatement
units and abatement unit equipment manufacturers, SIA has determined that there
are not any general criteria that can be applied to validate that abatement units made
by different manufacturers or based on different technologies are performing to their
expected DRE. As discussed in 7a, systems using the same technology but
manufactured by different companies will have different control indicators based on
how the system technology and their set-up requirements. The common
denominator amongst these different systems is that the manufacturers of the
equipment have established set-up and maintenance procedures to maintain system
operation at their expected DREs as required by Subpart I certification requirements
under 98.96(q)(1) and 96.97(d)(1).
The installation and maintenance of the abatement units, performed in accordance
with the manufacturer’s recommended requirements, coupled with the certification
mandated in the two sections of Subpart I, provide a repeatable, robust process for
validating that the abatement units should be operating to the expected DREs.
As discussed above, with the exception of the CF4 DRE, the tested units operated at
the expected DREs for abatement of NF3 from in-situ and remote plasma cleans and
all of the tested F-gases used in etch over a range of abatement unit types. These
results indicate that installing and maintaining the units in accordance with the
manufacturer’s recommended procedures provides an effective means to validate
that the abatement units are performing to the expected DREs for the gases being
treated.
The test data indicated that CF4 abatement systems at this one facility required a
more detailed maintenance procedure than the current one being executed at the
facility prior to testing. The need for more precise procedures is driven by the fact
that CF4 is difficult to breakdown, as exhibited by the low process utilization rates for
CF4. As discussed in the answer to 7a, supplier recommended modifications have
been made to the procedures and are being implemented at the facility.
SIA v. EPA, (D.C. Cir. No. 1024) Privileged and Confidential, For Settlement Purposes Only
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SIA recommends that the manufacturer’s recommended installation and
maintenance procedures serve as the generic criteria to validate that the abatement
units are performing at the expected DREs.
ENDING OPTION #1
The subpart I requirements can be strengthened by adding a section between
98.97(c) and 98.97(d) that requires the facility to establish and maintain a
maintenance plan for the abatement units, which includes 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 unit is found to not be operating properly.
Recommended Language:
98.97( ): The facility will establish and maintain an abatement unit maintenance and
corrective action plan which will define the required maintenance procedure for each
type of abatement units in use at the facility and a corrective action process that will
be followed whenever an abatement unit is found to not be operating properly.
This language would provide clarity to the requirements behind the certification. This
will enable a facility to set the maintenance procedures appropriate to its inventory of
abatement systems and will be an underpinning to the certification requirement in
98.96(q)(1) and 98.97(d)(1).
5. Additional abatement / DRE submission: SIA references additional information /
responses on abatement and DRE that will be submitted in March in the recent 3/6/12
submission to EPA.
One SIA member company intends to complete DRE testing of 20% of their installed
abatement units used for the removal of C2F6 and C3F8 from 200 mm chamber clean
processes in accordance with the requirements of the Subpart I rule. This represents
approximately 8 abatement units for C2F6 and 3 abatement units for C3F8. Because
they are still arranging scheduling with the testing firm and the fab, we expect that DRE
data will not be available for submittal to EPA until July or August of 2012. In addition,
there may be additional, limited DRE testing for 200 mm CVD C2F6 abatement from
another SIA member company. If done, these results should be available in April.
It is SIA’s intent to collect and analyze the results of this testing utilizing the same
methodology used to analyze the 300 mm NF3 CVD abatement and 300 mm etch
abatement data and propose an industry level DREs for abatement of 200 mm C2F6
and C3F8 CVD clean processes. Our intent is to have the industry level DRE results
available for incorporation into the re-proposed rule. If that is not possible, we intend to
SIA v. EPA, (D.C. Cir. No. 1024) Privileged and Confidential, For Settlement Purposes Only
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submit the data and associated statistical analysis for consideration as part of our
comments on the re-proposed Subpart I rule.
6. Gas consumption over time data: SIA has presented comparisons of short- and longterm consumption rates for two gases, NF3 (“SIA response to EPA stack Questions feb
2012”) and c-C4F8 (“Response to EPA’s Stack Test Question 1”). Can SIA provide
equivalent data for several other gases?
7. Threshold for infrequently used gases: EPA is considering setting a consumption limit for
gases that are used during the reporting period but not included (i.e. flowing) during a
stack test. If a gas goes over that limit, it would trigger a retest. Can SIA suggest a
threshold and metric (i.e. % estimated CO2e, kg/yr) for this limit?
8. Use of different methods at the same facility: Would SIA prefer to be able to choose a
method (i.e. etch or stack) per fab, as opposed to per facility? For facilities that have
gas cylinders/tanks feeding more than one fab, is this option possible or would those
facilities need to use one method for all fabs?
SIA v. EPA, (D.C. Cir. No. 1024) Privileged and Confidential, For Settlement Purposes Only
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