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# Assessing the need for FC abatement

standards Without a script, the semiconductor industry nonetheless appears well along the way toward a voluntary goal of the World Semiconductor Council (WSC) to limit atmospheric emissions of gaseous fluorinated compounds (FCs). The goal commits members to reduce c ertain FC emissions to 10% below base

- year amounts (which vary regionally) by 2010. However, we lack an industry standard for defining and measuring destruction or removal efficiency (DRE) of FC abatement systems, so the playing field isn’t level, and the veracity of reports and attainability of the goal can be questioned. Atmospheric FCs

- specifically CF 4 , CHF 3 , C 2 F 6 , C 3 F 8 , c - C 4 F 8 , NF 3 , and SF 6 , which may be emitted during CVD chamber

- clean and etch processes

- have high global warming potentials (GWPs). Expr essed as mass CO 2 - equivalents, these FCs have GWPs that are more than 3

- 4 orders of magnitude higher in trapping the earth’s reradiated heat compared to an equivalent amount of CO 2 . With the strong growth in semiconductor manufacturing, emission

- reducing t echnologies must achieve an average effectiveness of 90% compared to no control. For any particular company, the average FC

- reduction requirement could be as little as 70% or more than 90% depending on growth beyond the base

- year. Chip manufacturers, acco rding to International S EMATECH ’s latest (2005) State

- of

- the

Technology Report , can use various FC emission

- reducing solutions with 10

- 99% efficiencies. While favoring a “pollution prevention” approach that puts process optimization and/or alternative gase s ahead of abatement, post

- process FC

- destruction may still be needed according to the S EMATECH report. However, no industry

- standard definition and no standard protocol for the measurement of DRE exist. What matters is the amount of atmospheric FC emitte d

- the total mass CO 2 - equivalents of all relevant FC emissions. Yet, many fab ESH solutions merely lower FC wastes to safe concentrations. At issue are the effects of dilution and formation of FCs. Many abatementtechnologies use additives that dilute the e xhaust stream. So, defining and measuring DRE as a

difference between input and output FC

- concentrations, without accounting for the influence of dilution and the presence of other FCs, will overstate DREs and understate estimates of emissions. For exampl e, in popular thermal destruction systems, neglecting dilution can result in DREs being overstated for CF 4 by a factor of 20 to 50. A thermal system’s DRE for abating C 2 F 6 can be overstated by a factor of 10 if the effects of both dilution and CF 4 formatio n are neglected. We should build on the collaboratively developed, widely used Intel Emissions Protocol Revision 2.4b, which guides equipment manufacturers’ quantitative characterization of FC emissions. All estimates of FC

- process emissions can be traced to this protocol. Either the Intel protocol should be updated or a new protocol developed to explicitly address measuring DREs for all relevant abatement technologies that claim FC

- destruction capabilities: incineration

- type abatement with and without cat alytic assistance, heated

- tube type abatement with and without catalytic assistance, and plasma

- type abatement, both low

- and high

- pressure configurations. The new protocol should: Adopt the definition of DRE included in the just

- published IPCC FC emission s inventory guidance, which requires measurement of the total mass of all relevant FCs entering and leaving the system and so explicitly accounts for the effects of dilution. Adopt minimal as well as best

- methods for conducting representative sampling and for measuring total mass flow of all relevant FC effluents and all F

- containing effluents that enter and leave the abatement system. Provide standards for documenting and reporting. Identify the requirements for achieving and maintaining the measured DR E performance over an annual period. Assure that DREs quoted in purchase agreements are based on the new protocol and that the OEM requirements for achieving that DRE performance span an annual period. The time for completing and implementing the needed D RE

- measuring protocol is short. The effort will be significant, but the rewards will exceed the costs. Without such a protocol, the significant investment to attain the heralded WSC goal is threatened, as is the industry’s even larger investment to paint i tself green.

Click here to enlarge imageContact C. (Shep)herd Burton , an independent consultant serving clients in air quality management, at e

- mail: burtonentp@comcast.net To access this Article, go to: http://www.electroiq.com/content/eiq - 2/en/articles/sst/print/volume - 50/issue 1/departments/industry - forum/assessing - the - need - for - fc - abatement - standards.html