TECHNICAL SUPPORT DOCUMENT FOR PROCESS
EMISSIONS FROM ELECTRONICS MANUFACTURE
(SEMICONDUCTORS, MEMs, LIQUID CRYSTAL
DISPLAYS, AND PHOTO VOLT AICS):
PROPOSED RULE FOR MANDATORY REPORTING
OF GREENHOUSE GASES
Office of Air and Radiation
U.S. Environmental Protection Agency
January 29, 2009
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Contents
1. Source Description 3
a. Total U.S. Emissions 3
b. Emissions to be Reported 4
2. Options for Reporting Threshold 5
3. Options for Monitoring Methods 6
a. Etching and Cleaning 6
b. Nitrous Oxide (N20) Emissions 9
c. Heat Transfer Fluids (HTFs) 9
4. Procedures for Estimating Missing Data 10
5. Q A/QC Requirements 10
6. Reporting Procedures 10
7. References 11
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1. Source Description
The electronics industry uses multiple long-lived fluorocarbons (FCs) during manufacturing of electronic devices, including
semiconductors, liquid crystal displays (LCD), microelectromechanical systems (MEMs), and photovoltaic (PV) products.1
FC gases are used for plasma etching of silicon materials, and cleaning silicon deposits on deposition tool chamber walls.
Additionally, semiconductor manufacturing employs FC liquids as heat transfer fluids (HTFs). The most common FC gases
in use are trifluoromethane (HFC-23 or CHF3), perfluoromethane (CF4), perfluoroethane (C2F6), nitrogen trifluoride (NF3),
sulfur hexafluoride (SF6), and nitrous oxide (N20), although other compounds such as perfluoropropane (C3F8) and
perfluorocyclobutane (c-C4F8) are also used (EPA, 2008a). Besides dielectric film etching and chamber cleaning, much
smaller quantities of fluorinated gases are used to etch polysilicon films and refractory metal films like tungsten. PFCs may
also be used during dry photoresist stripping, a process also known "ashing." Table 1 presents the FCs used during
manufacture of each of these electronics.
Table 1. FCs Used by the Electronics Industry
Product Type
FCs Used During Manufacture
Semiconductor
CF4, C2F6, C3F8, c-C4F8, c-C4F80, c4f6, c5f8, chf3,
CH2F2, NF3, SF6, and HTFs.3
MEMsb
CF4, c-C4F8, and SF6
LCD
CF4, CHF3, c-C4F8, NF3, and SF6
PV
cf4, c2f6, chf3, c3f8, nf3, sf6
aFor commonly used heat transfer fluids please refer to the U.S. EPA report entitled "Uses and Emissions of Liquid PFC
Heat Transfer Fluids" available at: http://www.epa.gov/semiconductor-pfc/documents/pfc heat tranfer fluid emission.pdf.
b IPCC guidelines do not specify the FCs used by the MEMs industry. Literature reviews revealed that CF4, SF6, and the
Bosch process (e.g., Bosch process consists of alternating steps of SF6 and C4F8) are used to manufacture MEMs.
Source: IPCC, 2006; Lyshevshi, S., 2001; Gaitan, M. & Takacs, M., 2008.
The etching process uses plasma-generated fluorine atoms, which chemically react with exposed dielectric film, to
selectively remove the desired portions of the film. The material removed as well as undissociated fluorinated
gases flow into waste streams and, unless emission abatement systems are employed, into the atmosphere.
Chambers used for depositing dielectric films are cleaned periodically using fluorinated and other gases. During
the cleaning cycle the gas is converted to fluorine atoms in plasma, which etches away residual material from
chamber walls, electrodes, and chamber hardware. Undissociated fluorinated gases and other products pass from
the chamber to waste streams and, unless abatement systems are employed, into the atmosphere.
In addition to emissions of unreacted gases, some fluorinated compounds can also be transformed in the plasma
processes into different fluorinated compounds which are then exhausted, unless abated, into the atmosphere. For
example, when C2F6 is used in cleaning or etching, CF4 is generated and emitted as a process by-product.
Additionally, FC liquids are used as heat transfer fluids (HTFs) at several semiconductor facilities to cool process
equipment, control temperature during device testing, and solder semiconductor devices to circuit boards, and their
high vapor pressures can lead to evaporative losses during use (EPA, 2008b; IPCC, 2006).
a. Total U.S. Emissions
Emissions of FCs from an estimated 216 electronics facilities were estimated to be 6.0 Tg C02 Eq. Below is a
breakdown of emissions by electronics product type.
1 The electronics industry as defined here does not include light emitting diodes (LEDs). LED manufacturers do not use silicon
semiconductor substrates; therefore it is reasonable to conclude that LED manufacturers do not use PFCs.
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Semiconductor: Emissions of FCs, including heat transfer fluids, from 175 facilities were estimated to be 5.7 Tg
C02 Eq. in 2006 (Burton, C.S., & Beizaie, R., 2001; ITRS, 2007; SEMI, 2007; VLSI Research, Inc., 2007).2 Of
the total semiconductor emissions 5.1 Tg C02 Eq. are from etching/chamber cleaning at full-scale facilities, 0.1 Tg
C02 Eq. are from etching/chamber cleaning at R&D and pilot facilities and 0.5 Tg C02 Eq. are from HTF usage
from all facilities.3 Only etching/cleaning emissions from full-scale facilities are accounted for in the U.S.
Inventory of GHG Emissions and Sinks (EPA, 2008a). Partners of the PFC Reduction/Climate Partnership for
Semiconductors comprise approximately 80% of U.S. semiconductor production capacity. These Partners have
committed to reduce their emissions (exclusive of HTF emissions) to 10% below their 1995 levels by 2010, and
their emissions have been on a general decline toward attainment of this goal since 1999.
MEMs: Emissions of FCs from 12 facilities were estimated to be 0.1 Tg C02 Eq. in 2006 (SEMI, 2007).4 5
LCD: Emissions of FCs from 9 facilities were estimated to be 0.02 Tg C02 Eq. in 2006 (DisplaySearch, 2007).6
PV: Emissions of FCs from 20 PV facilities were estimated to be 0.07 Tg C02 Eq. in 2006 (Burton, 2006;
Roedern, B.V. & Ullal, H.S., 2008; Earth Policy Institute, 2007).7
b. Emissions to be Reported
On-site combustion emissions from electronics manufacturing facilities are not addressed within this document; see the
background Technical Support Document for Stationary Combustion (EPA-HQ-OAR-2008-0508-004). EPA is requiring
the electronics industry report direct FC emissions from the following two processes.
Plasma etching.
Chamber cleaning.
Additionally, the EPA is proposing to require that facilities report direct FC emissions from the following activity.
Heat Transfer Fluid Use.
2 Total semiconductor facilities include both full-scale, pilot, and R&D facilities.
3 All full scale facilities are assumed to have the same utilization. R&D and pilot facilities are also assumed to have the same utilization
but are assumed to be 175th the utilization of full scale facilities.
4 The estimated total number of MEMs facilities in the U.S. is an underestimate. The estimate was based on the World Fab Watch
database, which provides an incomplete listing of total U.S. MEMs facilities (SEMI, 2007).
5 Because no IPCC Tier 1 default emission factor relative to the area of the substrate for MEMs exists, one was estimated. Assuming
that MEMs are made from using the Bosch etching process, the utilization of SF6 in the production of MEMs was assumed to be the same
as the utilization of SF6 in the etching of semiconductors due to the similarity between the two processes. Although the Bosch etching
process uses both SF6 and C4F8, C4F8 was not included because C4F8 has a high utilization rate, i.e., a high fraction of C4F8 is dissociated
during the etching or cleaning process. The vast majority (86%) of SF6 used in semiconductor manufacturing process is used in the
etching process. The Tier 1 emission factor (per area of substrate) for each electronics product is related both to the utilization and
quantity of each type of gas used to make that product. Because SF6 is used in only about 20% of semiconductor processes but it is
assumed here that it is used in all MEMs processes, the semiconductor emission factor (per area of substrate) was multiplied by five to
estimate the MEMs emission factor per area of substrate.
6 Estimated total LCD facilities include LCOS, a-Si TFT-LCDs, OLEDs (assuming active matrix), EITPS, TFT, Single Crystal AMLCD,
LTPS facilities. Where, TFT = Thin Film Transistor; LCOS = Liquid Crystal on Silicon; a-Si = amorphous silicon; OLED = Organic
Light Emitting Diode; FITPS = Fligh Temperature Polysilicon; and AMLCD = Active Matrix Liquid Crystal Display.
7 Estimated total PV facilities includes only silicon based PV facilities (both crystalline and amorphous silicon based PV facilities are
included).
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2. Options for Reporting Threshold
EPA evaluated a range of threshold options for electronics manufacture. These included emission thresholds of 1,000,
10,000, 25,000, and 100,000 metric tons C02e and equivalent production capacity-based thresholds for each type of
electronics device. (The capacities equivalent to 25,000 mtC02e are listed in Table 2 below.) Annual production capacity
thresholds were derived using IPCC Tier 1 default emissions factors. Where IPCC Tier 1 default factors were unavailable
(i.e., MEMs), the emissions factor was estimated based on those of semiconductors for the relevant FCs.
Table 2 shows the capacity-based thresholds equivalent to 25,000 mtC02e for each electronics sector. These thresholds are
estimated to cover about 50% of semiconductor facilities and between 5% and 17% of the facilities manufacturing other
types of electronics. At the same time, the thresholds are expected to cover over 96% of FC emissions from semiconductor
facilities, and between 47% and 66% of FC emissions from facilities manufacturing other types of electronics. Combined,
these emissions are estimated to account for close to 94% of FC emissions from electronics as a whole.
Table 2. Capacity-Based Threshold (25,000 mtCQ2e)
Threshold Level
Total
National
Emissions
(mtC02e)
Total
National
Facilities
Emissions Covered
Facilities Covered
mtC02e/yr
Percent
Facilities
Percent
Semiconductors
1,080 m2 silicon
5,741,676
175
5,492,066
95.7%
91
52.0%
MEMs
1,020 m2 silicon
146,115
12
96,164
65.8%
2
16.7%
Flat Panel Displays
235,700 TFT-FPD m2
23,632
9
0
0%
0
0%
Photovoltaics
728,000 PV-cell m2
73,038
20
34,340
47%
1
5.0%
Table 3 shows emissions and facilities that would be captured by capacity-based thresholds equivalent to 1,000, 10,000,
25,000, and 100,000 metric tons of C02e.
Table 3. Capacity-Based Thresholds for Electronics Manufacture (1,000,10,000,25,000, and 100,000 mtCQ2e)
Threshold Level
(mtC02e)a
Total
National
Emissions
(mtC02e)
Total
National
Facilities
Emissions Covered
Facilities Covered
mtC02e/yr
Percent
Facilities
Percent
1,000
5,984,463
216
5,951,863
99.5%
163
75.5%
10,000
5,984,463
216
5,744,213
96.0%
113
52.3%
25,000
5,984,463
216
5,622,570
94.0%
94
43.5%
100,000
5,984,463
216
4,698,665
78.5%
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25.0%
" Capacity based threshold equivalents to the 1,000, 10,000, 25,000, and 100,000 mtC02e for the semiconductor industry are 40, 430, 1,080, 4,310 m2 Si,
for MEMs manufacture are 40, 410, 1,020, 4,100 m2 Si, for FPD manufacture are 9,430, 94,300, 235,700, 943,000 m2 TFT-FPD substrate, and for PV
manufacture are 29,120, 291,200, 728,00, 2,912,100 m2 PV-cell respectively.
Table 4 shows emissions and facilities that would be captured by emissions thresholds of 1,000, 10,000, 25,000, and
100,000 metric tons of C02e.
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Table 4. Emissions-Based Thresholds for Electronics Manufacture (1,000,10,000, 25,000, and 100,000 mtC02e)
Threshold Level
(mtC02e)a
Total
National
Emissions
(mtC02e)
Total
National
Facilities
Emissions Covered
Facilities Covered
mtC02e/yr
Percent
Facilities
Percent
1,000
5,984,463
216
5,966,476
99.7%
157
72.7%
10,000
5,984,463
216
5,681,001
94.9%
83
38.4%
25,000
5,984,463
216
5,324,624
89.0%
61
28.2%
100,000
5,984,463
216
2,799,814
46.8%
15
6.9%
Capacity-based thresholds would permit facilities to quickly determine whether or not they must report under this rule. In
addition, semiconductor manufacturers in particular may employ emissions abatement equipment (e.g., thermal oxidizers)
to lower their FC emissions. When abatement equipment is used, semiconductor manufacturers often estimate their
emissions using the manufacturer published Destruction or Removal Efficiency (DRE) for the equipment. However,
abatement equipment may fail to achieve its rated DRE for two reasons. First, the equipment may not be properly operated
and maintained. Second, the DRE itself may have been incorrectly measured due to a failure to account for the effects of
dilution (e.g., CF4 can be off by as much as a factor of 20 to 50 and C2F6 can be off by a factor of up to 10 because of
failure to properly account for dilution [Burton, 2007].) In either event, the actual emissions from facilities employing
abatement equipment may exceed estimates based on the rated DREs of this equipment and may therefore exceed the
mtC02e threshold without the knowledge of the facility operators. Reporting is therefore important for verifying the
performance of abatement equipment where it is used.
3. Options for Monitoring Methods
EPA reviewed a range of protocols for estimating fluorinated GHG emissions from electronics manufacturing. These
included the 2006IPCC Guidelines, EPA's PFC Reduction/Climate Partnership for the Semiconductor Industry, the
Technical Guidelines for the Voluntary Reporting of Greenhouse Gases (1605(b) Program), EPA's Climate Leaders
Program, The Climate Registry, the WRI/WBCSD Greenhouse Gas Protocol, and the World Semiconductor Council
methods.
The methods described in these protocols and guidelines coalesce around the methods described by the 2006 IPCC
guidelines. For monitoring emissions of fluorinated GHGs from etching and cleaning, EPA evaluated the IPCC Tier 1,
Tier 2a, Tier 2b, and Tier 3 approaches, as well as hybrids of these approaches, as described below. For monitoring
emissions of heat transfer fluids, EPA evaluated the IPCC Tier 1 and Tier 2 approaches.
None of the IPCC methods require a standard protocol to estimate DREs of abatement equipment. Given that the actual
DRE of the abatement equipment can be significantly smaller (by up to a factor of 50) compared to the manufacturer rated
DRE, the EPA is considering requiring verification of the DREs using a standard reporting protocol (Burton, 2007). A
draft of such a standard protocol is under development by the EPA (not yet published).
a. Etching and Cleaning
In the Tier 1 approach, the surface area of substrate (e.g., silicon, LCD or PV-cell) produced during manufacture is
multiplied by a default gas-specific emission factor. The advantages of the Tier 1 approach lie in its simplicity. However,
this method does not account for the differences among process types (i.e., etching versus cleaning), individual processes,
or tools, leading to uncertainties in the default emission factors of up to 200% at the 95% confidence interval (IPCC,
2006).8 Moreover, facilities routinely monitor gas consumption in the ordinary course of business, making it technically
feasible to employ a method with the complexity of at least the IPCC Tier 2a approach without additional data collection
efforts.
8 This uncertainty refers only to semiconductors and LCDs. Tier 1 emission factor uncertainty for PV were not estimated in the IPCC
Guidelines (IPCC, 2006).
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In the Tier 2a approach, chemical-specific gas consumption is multiplied by default factors for utilization, by-product
formation, and destruction. The Tier 2a approach is relatively-simple, given that gas consumption data is collected in the
ordinary course of business. However, due to variation in gas utilization between etching and cleaning processes, the
emissions estimated using the Tier 2a approach have greater uncertainty than emissions estimated using the Tier 2b
approach.
In the Tier 2b approach, chemical-specific gas consumption by process type (i.e. etch or chamber clean) is multiplied by
default factors for utilization, by-product formation, and destruction. The Tier 2b approach requires facilities to determine
gas consumption by process-type (i.e., etch versus clean). Equation 1 below is used to estimate FC emissions during
process (j) for gas (i), and Equation 2 below is used to estimate byproduct gas (p) that results from gas (i) utilization during
process (j).
Equation 1) E(FC)i,j = FCi,j (1 - Ui,j) x (1 - ai,j x di,j)
where,
E(FC)i,j = emissions of gas (i) used in process (j), kg
FCi,j = consumption of gas (i) for process (j), kg
Ui,j = process utilization rate for gas (i) during process (j)
ai,j = fraction of gas (i) used in process (j) with abatement devices
di,j = fraction of gas (i) destroyed in abatement devices connected to process (j)
Equation 2) B(FC)i,j = Bp,i,j x FCi,j x (1 - ai,j x dp,j)
where,
B(FC)p,i,j = by-product gas (p) emissions from gas (i) used in process (j), kg
Bp,i,j = fraction of gas (p) created during gas (i) in process (j)
FCi,j = consumption of gas (i) for process (j), kg
ai,j = fraction of gas (i) used in process (j) with abatement devices
dp,j = fraction of gas (p) destroyed in abatement devices connected to process (j)
The heel "h" has been removed from the equation here, since it is assumed that facilities will estimate their FC usage using
flow meters or process recipes (and duration of the process) when estimating their emissions. In this case, heel estimates
are not required. However, if gas consumption is estimated using gas cylinders, both Equations 1 and 2 must be multiplied
by one minus a heel factor to account for gas remaining in cylinders at the end of life. The IPCC 2006 default for the heel
factor is 0.1 (IPCC, 2006).
Although the uncertainty relative to Tier 2a is reduced, the Tier 2b approach does not account for variation among
individual processes or tools and, therefore, the estimated emissions have approximately 3-4 times as high uncertainty
compared to Tier 3 estimates. The Tier 2b total FC emissions estimate uncertainty is approximately ±51%. For a typical
large fab with emissions of approximately 113,000 mtC02e, this relative uncertainty equates to an absolute uncertainty of
±58,000 mtC02e.
The Tier 3 approach uses the same equations as the Tier 2b approach, but requires company-specific data on (1) gas
consumption, (2) gas utilization, (3) by-product formation, and (4) DRE for all processes at the facility. The use of the Tier
3 method will result in the least uncertain estimates. Information on gas consumption by process is sometimes gathered in
the ordinary course of business, and information on gas utilization and by-product formation is readily available from tool
manufacturers. In addition, gas utilization and byproduct formation can be experimentally measured on-site at the facility
(International Sematech, 2006). To obtain accurate estimates of these parameters, the guidance prepared by International
SEMATECH Technology Transfer (#0612485A-ENG) should be followed when conducting gas utilization and by-product
formation measurements (December 2006).
The total facility-level FC emissions estimate from etching/cleaning using Tier 3 analysis is estimated to have an
uncertainty on the order of ±15% at the 95% confidence interval (IPCC, 2006). For a typical large fab with emissions of
approximately 113,000 mtC02e, this relative uncertainty equates to an absolute uncertainty of ±17,000 mtC02e.
Hybrid Approach A would require large facilities (defined as facilities with capacities of greater than 10,500 m2 silicon) to
estimate their etching and cleaning emissions using an approach based on the IPCC Tier 3 method; all other facilities would
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be required to use the IPCC Tier 2b method. Under these approaches, EPA estimates that 17% of all semiconductor
manufacturing facilities would be required to report using a Tier 3 approach (equivalent to 29 entities out of 175 total
entities) and that 58% of total semiconductor emissions (equivalent 3.3 Tg C02 Eq out of a total 5.7 Tg C02 Eq emissions)
would be reported using the Tier 3 approach.
Hybrid Approach B would require Tier 3 reporting for all facilities, but only for the top three gases emitted at each facility.
For all other gases, the Tier 2b approach would be required. The top three gases emitted, based on data in the Inventory of
U.S. GHG Emissions and Sinks, are C2F6, CF4, and SF6 (EPA, 2008a). These top three gases accounted for approximately
80% of total FC emissions from semiconductor manufacturing during etching and chamber cleaning in 2006. The
uncertainty associated with the Tier 2b/3 hybrid approach has not been developed, but is assumed to be between the
uncertainty for a Tier 2b and Tier 3 approach.
Verifying the PRE of Abatement Equipment. As mentioned above, EPA has evaluated additional requirements for
verifying the DRE of abatement equipment. Both of the approaches evaluated would require that the DRE be verified using
an industry standard or protocol, such as the one being developed by the EPA as part of the PFC Reduction/Climate
Partnership for Semiconductors. (This standard has not yet been published). This draft protocol requires the person
verifying the DRE to experimentally determine the effective dilution of the waste stream as it travels through the abatement
device and to measure the DRE during representative actual or simulated process conditions. The following measurements
and calculations are critical to the protocol:
(1) Experimentally determine the effective dilution through the abatement device and measure abatement DRE during
actual or simulated process conditions by following the procedures of this paragraph.
(i) Measure the concentrations of F-GHGs exiting the process tool and entering and exiting the abatement system under
operating process and abatement system conditions that are representative of those for which F-GHG emissions are
estimated and abatement-system DRE is used for the F-GHG reporting period9;
(ii) Measure the dilution through the abatement system and calculate the dilution factor under the representative operating
conditions given in paragraph (c)(i) of this section by using the tracer method. This method consists of injecting known
flows of a non-reactive gas (such as krypton) at the inlet of the abatement system, measuring the time-averaged
concentrations of krypton entering ([Kr]m) and exiting ([Kr]out) the abatement system, and calculating the dilution factor
(DF) as the ratio of the time-averaged measured krypton concentrations entering and exiting the abatement system, using
equation I-10 of this section.
DF = fcj"
[*>L
(iii) Measure the F-GHG concentrations in and out of the device with all process chambers connected to the F-GHG
abatement system and under the production and abatement system conditions for which F-GHG emissions are estimated for
the reporting period10;
(iv) Calculate abatement system DRE using Equation 1-11 of this section, where it is assumed that the measurement
pressure and temperature at the inlet and outlet of the abatement system are identical and where the relative precision (e) of
the quantity c1.0ut*DF/c1.in shall not exceed ±10% (two standard deviations) using proper statistical methods.
DF*c .
d =1
V C,-,n
Where:
9 Abatement system means a point-of-use (POU) abatement system whereby a single abatement system is attached to a single process
tool or single process chamber of a multi-chamber tool.
10 Most process tools have multiple chambers. For combustion-type abatement systems, the outlets of each chamber separately enter the
destruction-reactor because premixing of certain gaseous mixtures may be conducive to fire or explosion. For the less-frequently used
plasma-type POU abatement systems, there is one system per chamber.
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Destruction or removal efficiency (DRE)
Concentration of gas i in the inflow to the abatement system (ppm).
Concentration of gas i in the outflow from the abatement system (ppm).
Dilution Factor calculated using Equation 1-10.
(v) The DF should not be obtained by calculation from flows other than those obtained by using the tracer method
described in paragraph (ii).
The difference between the two approaches lies in who performs the test. In the first approach, each facility would perform
the test on site for each piece of abatement equipment. In the second approach, a third party (e.g., Underwriters Labs)
would perform the test on behalf of the manufacturer of the abatement equipment, testing representative samples of the
abatement equipment. Under this approach, electronics manufacturing facilities would be required to buy equipment that
had been certified under this third-party testing. Because testing would not need to be obtained for every piece of
equipment sold, this approach would probably be less expensive than in-house testing by electronics manufacturers, but it
may not capture the full range of conditions under which the abatement equipment would actually be used. Facilities
pursuing either DRE verification method would also be required to use the equipment within the manufacturer's specified
equipment lifetime, operate the equipment within manufacturer specified limits for the gas mix intended for destruction,
and maintain the equipment according to the manufacturer guidelines.
b. Nitrous Oxide (N20) Emissions
A simple mass-balance approach is proposed to estimate emissions of N20 during chemical vapor deposition, as shown in
Equation 4. This methodology assumes N20 is not utilized during this process, due to lack of N20 utilization data.
Equation 3) E(N20) = FCN2o x (1-h)
where,
E(N20) = Emissions of N20, kg
FCN20 = Consumption of N20, kg
h = heel fraction of gas in cylinders
c. Heat Transfer Fluids (HTFs)
The Tier 1 approach for HTF emissions is based on the utilization capacity of the semiconductor facility multiplied by a
default emission factor. Although, the Tier 1 approach has the advantages of simplicity, it relies on a default emissions
factor to estimate HTF emissions and has relatively high uncertainty compared to the Tier 2 approach (IPCC, 2006).
The IPCC Tier 2 approach, which is a mass-balance approach, uses company-specific data and accounts for differences
among facilities' HTFs (which vary in their global warming potentials), leak rates, and service practices, and has an
uncertainty on the order of ±20% at the 95% confidence interval (IPCC, 2006). Equation 3 below shows the company-
specific mass-balance equation for estimating HTF emissions.
Equation 4) E(HTFi) = density x [Ii,o + Pi,t - Ni,t + Ri,t - Ii,t - Di,t]
where,
E(HTFi) = Emissions of heat transfer fluid (i) (HTFi), kg
density = density of HTFi, kg/1
Ii,o = Inventory of HTFi at the end of previous period, 1
Pi,t = Net purchases of HTFi during the current period, 1
Ni,t = Total nameplate capacity [charge] of installed liquid HTFi equipment, 1
Ri,t = Total nameplate capacity [charge] on retired liquid HTFi equipment, 1
Ii,t = Inventory of liquid HTFi at the end of current period, 1
Di,t = Amount of liquid HTFi recovered and sent offsite during current period, 1
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4.
Procedures for Estimating Missing Data
When estimating etching/cleaning emissions and company-specific process gas utilization rates and by-product gas
formation rates are missing, companies could apply defaults from next lower Tier (e.g., IPCC Tier 2b or Tier 2a) to
estimate missing data. However, companies should limit their use of using defaults from the next lower Tier to less than 5
percent of their emissions estimate. Additionally, default values for estimating DRE will not be permitted, and DREs must
be estimated as zero in the absence of facility-specific DREs that have been third-party verified and/or use a standard
protocol. Gas consumption is collected as BAU and is not expected to be missing; therefore, it should not be necessary to
revert to the Tier 1 approach for estimating emissions. When estimating HTF emissions during semiconductor
manufacture, the use of the mass-balance approach requires correct records for all inputs. Should the facility be missing
records for a given input, it may be possible that the HTF supplier has information in their records for the facility.
5. QA/QC Requirements
QA/QC methods for reporting emissions from etching and cleaning include:
Following the SEMATECH guidelines for QA/QC procedures when estimating gas process utilization and by-
product gas formation (International Sematech, 2006).
Keeping record logs of abatement device maintenance.
Tracking gas consumption is done as BAU to a high-degree of precision, and further QA/QC is not being required.
QA/QC methods for reporting emissions from HTFs from semiconductors include:
Reviewing inputs to the mass balance equation to ensure inputs and outputs to the facility's system are all
accounted for in all appropriate sections.
Ensuring no negative inputs are entered and negative emissions are not calculated. However, the change in
storage inventory and nameplate capacity may be calculated as negative numbers.
Ensuring that beginning of year inventory matches end of year inventory from previous year.
6. Reporting Procedures
The following supplemental data would be useful for confirming emissions calculations and/or calculating emission rates
that could be compared across facilities for quality control purposes:
Report:
o Method used (i.e. 2b or 3)
o Mass of each gas fed into each process type (kg)
o GWPs for each FC used/created as a by-product
o Production capacity in terms of substrate surface area (e.g., silicon, PV-cell, LCD)
o Factors used for gas utilization, by-product formation and their sources/uncertainties
o Emission control technology DREs and their uncertainties
o Fraction of gas fed into each process type with emission control technologies
o Abatement device calibration/maintenance records
o Description of abatement controls
o Inputs in the mass-balance equation (for HTF emissions)
o Example calculation
o Description of QA/QC plan
o Emissions uncertainty estimate
Keep records of:
o Data actually used to estimate emissions
o Records supporting values used to estimate emissions
o The initial and any subsequent tests of the abatement equipment's destruction or removal
efficiency (DRE)
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o The initial and any subsequent tests to determine emission factors for process
7. References
Burton, C.S., & Beizaie, R. (2001). EPA's PFC Emissions Model (PEVM) v. 2.14: Description and Documentation.
Prepared for Office of Global Programs, U. S. Environmental Protection Agency, Washington, DC. 20001 November 2001.
Burton (2006). PV Emissions during Photovoltaic (PV) Cell Fabrication: A Scoping Report.
Burton (2007). Assessing the need for FC abatement standards, Solid State Technology, January 2007. Available at:
http://sst.pennnet.com/displav article/281422/5/ARTCL/none/none/l/Assessing-the-need-for-FC-abatement-standards/
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Appendix A
Greenhouse Gases with TAR GWP
Greenhouse Gases
without TAR GWP
Non-GHGs
Producing
FC By-
prod uctsf
Process Gas
CF4
C2F6
CHF3
CH2F2
C3F8
c-
C4F8
NF3
Remote
NF3
SF6
C4F6
C5F8
C4F80
F2
COF2
Etch 1-Ui
0.7*
0.4*
0.4*
0.06*
NA
0.2*
NA
0.2
0.2
0.1
0.2
NA
NA
NA
CVD 1-Ui
0.9
0.6
NA
NA
0.4
0.1
0.02
0.2
NA
NA
0.1
0.1
NA
NA
Etch BCF4
NA
0.4*
0.07*
0.08*
NA
0.2
NA
NA
NA
0.3*
0.2
NA
NA
NA
SEMICONDUCTOR
Etch BC2F6
NA
NA
NA
NA
NA
0.2
NA
NA
NA
0.2*
0.2
NA
NA
NA
MANUFACTURING
CVD BCF4
NA
0.1
NA
NA
0.1
0.1
0.02f
0.1 f
NA
NA
0.1
0.1
0.02f
0.02f
CVD BC2F6
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
CVD BC3F8
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.04
NA
NA
Etch 1-Ui
0.6
NA
0.2
NA
NA
0.1
NA
NA
0.3
NA
NA
NA
NA
NA
CVD 1-Ui
NA
NA
NA
NA
NA
NA
0.03
0.3
0.9
NA
NA
NA
NA
NA
Etch BCF4
NA
NA
0.07
NA
NA
0.009
NA
NA
NA
NA
NA
NA
NA
NA
LCD
Etch BCHF3
NA
NA
NA
NA
NA
0.02
NA
NA
NA
NA
NA
NA
NA
NA
MANUFACTURING
Etch BC2F6
NA
NA
0.05
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
CVD BCF4
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
CVD BC2F6
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
CVD BC3F8
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Etch 1-Ui
0.7
0.4
0.4
NA
NA
0.2
NA
NA
0.4
NA
NA
NA
NA
NA
CVD 1-Ui
NA
0.6
NA
NA
0.1
0.1
NA
0.3
0.4
NA
NA
NA
NA
NA
PV
MANUFACTURING
Etch BCF4
NA
0.2
NA
NA
NA
0.1
NA
NA
NA
NA
NA
NA
NA
NA
Etch BC2F6
NA
NA
NA
NA
NA
0.1
NA
NA
NA
NA
NA
NA
NA
NA
CVD BCF4
NA
0.2
NA
NA
0.2
0.1
NA
NA
NA
NA
NA
NA
NA
NA
CVD BC2F6
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
CVD BC3F8
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Notes: NA denotes not applicable based on currently available information
t The default emission factors for F2 and COF2 may be applied to cleaning low-k CVD reactors with CIF3.
* Estimate includes multi-gas etch processes
t Estimate reflects presence of low-k, carbide and multi-gas etch processes that may contain a C-containing FC additive
Source: IPCC, 2006
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