CAP Í TULO II METODOLOG Í A
TABLA Nº 09 RESULTADO DE COMPLICACION SEGÚN DIAGNOSTICO POST OPERATORIO
4.27.1 Source Category Description
PFCs and SF6 are released from activities in this source sector.
The electronics industry is one of the largest sources of PFC emissions in the UK. The main uses of PFCs are as follows:
• Cleaning of chambers used for chemical vapour deposition (CVD) processes;
• Dry plasma etching;
• Vapour phase soldering and vapour phase blanketing;
• Leak testing of hermetically sealed components; and
• Cooling liquids, e.g. in supercomputers or radar systems.
In addition SF6 is used in etching processes for polysilicon and nitrite surfaces, and there is
some usage of CHF3 and NF3. The first two of these processes (cleaning and etching during
semiconductor manufacture) account for the majority of emissions from the sector, with cleaning accounting for around 70% and etching 30%.
4.27.2 Methodological Issues
Industrial Processes (CRF Sector 2)
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UK NIR 2012 (Issue 2) AEA Page 169
Emissions of PFC and SF6 emissions from electronics are based on data supplied by UK
MEAC – the UK Microelectronics Environmental Advisory Committee (in conjunction with the UK DTI). UK MEAC gave PFC consumption for the UK electronics sector based on purchases of PFCs as reported by individual companies. Emissions were then calculated using the IPCC Tier 1 methodology, which subtracts the amount of gas left in the shipping container (the “heel” amount, 10%), the amount converted to other products (between 20% and 80% depending on the gas) and the amount fed to abatement. The general equation used to calculate the emissions is given later in this section.
The estimates of HFC and SF6 emissions are based on consumption data (purchases) from
2001, which were supplied by the UK MEAC / DTI. The data supplied were the purchases, used by the semiconductor industry, of SF6 and NF3, and the following PFC species: C2F6,
CF4, CHF3, C3F8, and C4F8. Estimates of PFC and SF6 consumptions in the years before
and after 2001 are made from assumptions about the annual growth rates, and the annual rate of change of usage per unit consumption. Both these sets of data are supplied by MEAC.
Estimates of emissions in the time series are based on i) the consumption of gases in sector and ii) assumptions about growth rate in sector, gas use and abatement.
Emissions of PFCs for previous years were extrapolated backwards (to 1990) assuming an annual 15% growth in the production of semiconductors in the UK up until 1999. A sharp decline in growth is then assumed in 2001, and from 2006 onwards, a growth of 10% is assumed and this growth then declines slowly from 2013 onwards.
An annual increase in the amount of PFCs used per unit production is assumed. PFC specific usage data are used to estimate emissions. Across the time series C2F6
consumption dominates total PFC consumption. This figure is 3% from 1990 to 1996, as production methods required more PFCs for finer and more complex etching processes. A gradual decrease to 0% in 1999 and –1% in 2000 is assumed as measures to reduce use of PFCs begin to be implemented. The figure then declines to -2% until 2004, and then declines further to -8% until 2010 and is assumed constant at -1% into the future.
Emission estimates of PFC and SF6 emissions were calculated using modification of an
equation provided by the World Semiconductor Council (WSC). For example, the equation below is used for the estimation of CF4.
Emissions for PFCi = PFCi*(1-h)[(1-Ci)(1-Ai)*GWPi + Bi*GWPCF4*(1-ACF4)]
h = fraction of gasi remaining in container (heel)
PFCi = purchases of gasi = kgsi
kgsi = mass of gasi purchased
GWPi = 100 yr global warming potential of gasi
Ci = average utilization factor of gasi (average for all etch and CVD processes)
= 1-EFi
EFi = average emission factor of gasi (average for all etch and CVD processes)
Bi = mass of CF4 created per unit mass of PFCi transformed
Ai = fraction of PFCi destroyed by abatement = ai,j*Va
ACF4 = fraction of PFCi converted to CF4 and destroyed by abatement = aCF4*Va
ai,j = average destruction efficiency of abatement toolj for gasi
aCF4 = average destruction efficiency of abatement toolj for CF4
Industrial Processes (CRF Sector 2)
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UK NIR 2012 (Issue 2) AEA Page 170
Emissions of PFCs from semiconductor manufacturing are combined with emissions from training shoes in source category 2F9 for reasons of commercial confidentiality. This source category is described in Section 4.30.
Emissions of SF6 from semiconductor manufacturing are combined with emissions from
training shoes and electrical insulation in source category 2F9 for reasons of commercial confidentiality. This source category is described in Section 4.30.
A full description of the emissions and associated methodology used is contained in AEAT (2004). The estimates were reviewed in 2008 and last updated in 2004.
4.27.3 Uncertainties and Time-Series Consistency
Estimates of emissions are based on very limited data and are therefore uncertain.
Emissions of C2F6 dominate total PFC emissions, on a GWP basis, and are approximately
70% of total PFC emissions, across the time series. Emissions of SF6 are between 11% and
17% of total GWP weighted emissions (PFC and SF6) from semiconductor manufacture
across the time series
4.27.4 Source Specific QA/QC and Verification
This source category is covered by the general QA/QC of the greenhouse gas inventory in
Section 1.6. Details of verification of emissions are given in Annex 10.
Trilateral F-gas Peer Review
A trilateral meeting of F-gas sector experts from the UK, Austria and Germany was held in Vienna, February 2011. Although not a formal review, each country reviewed the completeness, consistency and transparency of the parts of the NIRs reporting F-gases. Some of the improvements that could be made to the transparency and completeness of the UK NIR identified in that review have been incorporated in this NIR, and others will be considered for future implementation.
4.27.5 Source Specific Recalculations
There have been no recalculations made to the emissions data for this sector since the previous submission.
4.27.6 Source Specific Planned Improvements
Activity data and emission factors will be kept under review.