1Limitations on Continuous EmissionMonitors (CEMs) for QuantifyingSemiconductor Greenhouse Gas (GHG)Emissions6thISMI Symposium on Manufacturing EffectivenessOctober, 2009T. Higgs, IntelBackgroundyFluorinated compounds a key focus in emergingclimate programs–PFCs, HFCs, HFEs–High global warming potential (GWP), widely usedin semiconductor industryyPending GHG reporting rule covers all fluorinatedmaterials w/GWP>1yAmerican Clean Energy and Security Act `09(Waxman-Markey) proposes wide use of CEMs–Requires use of CEMs or “alternative systems that aredemonstrated as providing data with the same precision,reliability, accessibility and timeliness . . . as data provided bycontinuous monitoring systems.”Problem StatementyCEMs assumed to be a superior measurementmethod, without supporting datayCEMs well established, work well forsomeapplications–Single pollutant, constant exhaust streams–e.g. SOx monitoring for power plantsyNot proven for SC industry, likely not feasible–Multi-pollutant exhaust; many individual speciesmake up total GHGs–Low concentrations - often < detectable levelsCEMs may be lessaccurate than simpler, lessexpensive methodsPFCsinPFCsinMany individual emission sources- CEMS on all tools not feasible;only option is final exhaust pointTypical Fab LayoutCase Study – IntelManufacturing SiteyScrubber stacks monitored for 8 hrs w/FTIR–FTIR widely used to measure fab tool emissions–Discrete, short term tests on single tools–If CEMs required, FTIR is likely technology used–To date, not demonstrated in a CEM applicationy3 fabs on site, 30 scrubber stacks–Combined flow 534,000 cfmy7 PFCs/HFCs monitoredObjective: determine total PFC CO2e mass error–Extrapolate to determine annual error if used as CEMError Source 1: Detection LimitsyEmissions highly variableyBelow detection levels for much of test period,even with w/FTIR’s low detection limitsMaterialDet Limit,ppb% of readings belowdet. limitCF4343.7CH3F6491.3CH2F25688.1C2F64463.6SF6649.2CHF3674.8NF32970.5Result: significant error from periods of nondetectTotal Detection Limit ErroryEmissions during ND readings somewherebetween 0 and MDLLbs./hrat 0Lbs./hrat MDLAnnualmtCO2e at 0Annual mtCO2eat MDLCF41.521.5344,65245,033CH3F0.250.083196CH2F20.350.13354926C2F62.281.7182,878110,521SF60.670.5246,90161,077CHF30.110.0848306701NF30.570.4530,98338,959Total210,629263,313Average: 236,971 mtCO2Error range: +/- 26,342 (11%)Error Source 2: Instrument MeasurementErroryDetectable readingshave a stated +/-margin of erroryTotal error permaterial calculatedby adding sum ofsquares of errorsacross all 30 stacksError,lbs./hrTotal annualerror, mtCO2eCF4.004122CH3F.0135CH2F2.0253C2F6.083921SF6.0131208CHF3.003165NF3.032030Total+/- 7504Combined error,1 + 226,342 + 7504 =33,846Total error: 236,971+/- 33,846 (14.3%)Error Source 3: CEM downtime•Existing CEM regs, 40CFR75 typically allow 10% DT•Assume emissions during downtime = overall average•Assess error if actual emissionsvary from avg. by 1 std. dev.Std. Dev.measuredAnn error,10% DTmtCO2eCF424 – 192%2761CH3F29 – 41%1.3CH2F222 – 83%20C2F69 – 239%9672SF69 – 102%2640CHF326 – 68%257NF317 – 154%3122+/- 18,473Combined error, 1+2+333,846 + 18,473 = 52,319Totalerror,236,971+/- 52,319,(22.1%)Other Potential ErrorsyFugitive emissions–Fluorinated heat transfer fluids, HFEs, used outside process–Don’t pass through stack, can’t be measured by CEM–Industry emissions data lacking, but use is substantialyWide range of materials regulated as F-gases–Do FTIR standards, cal gases exist for all?–Knowledge of process required to ID F-gases to measureyDetection limits likely higher in CEM use–Result: higher error from non-detect readingsyKnown errors +/- 22%; likely > +/- 25% when othersconsidered–Stack emissions only; CEMswon’t account for fugitivesExisting Tier 3 MethodsCF4CH3FCH2F2C2F6SF6CHF3NF3EF = 0.5EF = 0.1EF = 0.3TotalchemicalusemeasuredUse byprocessestimatedIndividualEFsmeasuredOverall EFby chemicalcalculatedTotal Error Unquantified – use by process likelylargest sourceAnnual Tier 3 result: 284,000 mtCO2CostyFTIR instrument cost ~$100K–adapting to use as CEM adds cost–Permanent source of power, temp controlledenvironment–Data logging system to capture continuousdata feedy30 stacks = $3M for upfront instrument cost–Excluding upgrades needed to use as CEMyLikely installed cost - $5-10M–Excluding maintenance, calibration and laborcostsConclusionsyNo existing proven CEM for semiconductor PFCsyFTIR widely used for short term monitoring–Typically at point of use, discrete time periodsyNot readily adaptable to use as CEM–End of stack emissions mixed, very dilute–Some emissions fugitive, so “invisible” to CEM–Estimated best case accuracy +/- 25%–Case study result w/CEMs: 185k – 289k mtCO2e–Tier 3 result: 284k mtCO2e; error uncertainResult: requiring CEMs for PFCs would result insubstantial cost, error larger than +/- 25%AcknowledgementsyKurt Parker, Environmental Resources Management