Limitations on Continuous EmisMonitors (CEMs) for Quantifying Semiconductor Greenhouse GaEmissions 6th ISMI Symposium on Manufacturi

October, 2009T. Higgs, Intel
Background

y Fluorinated compounds a key focus 

climate programs

– PFCs, HFCs, HFEs– High global warming potential (GW

in semiconductor industry

y Pending GHG reporting rule covers a

materials w/GWP>1

y American Clean Energy and Security 

(Waxman-Markey) proposes wide us

– Requires use of CEMs or “alternative system

demonstrated as providing data with the samreliability, accessibility and timeliness . . . as continuous monitoring systems.”
Problem Statement

y CEMs assumed to be a superior me

method, without supporting data

y CEMs well established, work well fo

applications

– Single pollutant, constant exhaus

– e.g. SOx monitoring for powe

y Not proven for SC industry, likely no

– Multi-pollutant exhaust; many ind

make up total GHGs

– Low concentrations - often < deteCEMs may be less accurate than sim

expensive methods
PFCs 

in

Many individual emission source

- CEMS on all tools not feasible; only option is fin

Typical Fab Layout
Case Study – Intel 

Manufacturing Site

y Scrubber stacks monitored for 8 hrs w

– FTIR widely used to measure fab to

– Discrete, short term tests on single to

– If CEMs required, FTIR is likely tec

– To date, not demonstrated in a CEM a

y 3 fabs on site, 30 scrubber stacks

– Combined flow 534,000 cfm

y 7 PFCs/HFCs monitoredObjective: determine total PFC CO2e m

– Extrapolate to determine annual error if u
Error Source 1: Detection Lim

y Emissions highly variabley Below detection levels for much of te

even with w/FTIR’s low detection lim

Material Det Limit, 

ppb

% of readings det. limit

CF4

3 43.7

CH3F 64 91.3

CH2F2 56 88.1

C2F6 44 63.6

SF6

6 49.2

CHF3

6 74.8

NF3 29 70.5

Result: significant error from pedetect
Total Detection Limit Error

y Emissions during ND readings some

between 0 and MDL

Lbs./hr at 0

Lbs./hr at MDL

Annual mtCO2e at 0

CF4 1.52 1.53 44,652 

CH3F 0.25 0.08 31 

CH2F2 0.35 0.13 354 

C2F6 2.28 1.71 82,878 

SF6 0.67 0.52 46,901 

CHF3 0.11 0.08 4830 

NF3 0.57 0.45 30,983 

Total 210,629 

Average: 236Error range: +
Error Source 2: Instrument M

Error

y Detectable readings 

have a stated +/-margin of error 

y Total error per 

material calculated by adding sum of squares of errors across all 30 stacks

Error, lbs./hr

CF4 .004 CH3F .013CH2F2 .02 C2F6 .08 SF6 .013 CHF3 .003 NF3 .03 Total Combined error, 1 + 2

Total error: 236,971 +/- 33,846 (14.3%)
Error Source 3: CEM dow

• Existing CEM regs, 40CFR75 typically allow 

• Assume emissions during downtime = over

• Assess error if actual emissions vary from avg. 

Std. Dev. measured

Ann error,10mtCO2e

CF4 24 – 192% 2761

CH3F 29 – 41% 1.3

CH2F2 22 – 83% 20

C2F6 9 – 239% 9672

SF6 9 – 102% 2640

CHF3 26 – 68% 257

NF3 17 – 154% 3122

+/- 18,473

Combined error, 1+2+3 33,846 + 18,473 
Other Potential Erro

y Fugitive emissions

– Fluorinated heat transfer fluids, HFEs, used – Don’t pass through stack, can’t be measure– Industry emissions data lacking, but use is 

y Wide range of materials regulated as F

– Do FTIR standards, cal gases exist for all?– Knowledge of process required to ID F-gas

y Detection limits likely higher in CEM us

– Result: higher error from non-detect readin

y Known errors +/- 22%; likely > +/- 25% w

considered

– Stack emissions only; CEMs won’t account 
Existing Tier 3 Methods

CF4

CH3F

CH2F2

C2F6

SF6

CHF3

NF3

EF = 0.5

EF = 0.1EF = 0.3

Total 

chemical 

use 

measured

Use by 

process 

estimated

Individua

EFs 

measured

Total Error Unquantified – use by plargest sourceAnnual Tier 3 result: 284,000 mtCO
Cost

y FTIR instrument cost ~$100K 

– adapting to use as CEM adds co

– Permanent source of power, 

environment

– Data logging system to captu

data feed

y 30 stacks = $3M for upfront instrum

– Excluding upgrades needed to u

y Likely installed cost - $5-10M 

– Excluding maintenance, calibrat

costs 
Conclusions

y No existing proven CEM for semicoy FTIR widely used for short term mo

– Typically at point of use, discrete time 

y Not readily adaptable to use as CEM

– End of stack emissions mixed, very dil– Some emissions fugitive, so “invisible– Estimated best case accuracy +/- 25%

– Case study result w/CEMs: 185k – – Tier 3 result: 284k mtCO2e; error u

Result: requiring CEMs for PFCs wo

substantial cost, error larger than +
Acknowledgements

y Kurt Parker, Environmental Resources Ma