PFC gases and liquids are traditionally used in several electronics industry processes ranging from semiconductor front-end manufacturing, IC-components quality control testing to direct contact dielectric cooling of e.g. power electronics assembly.
With the phase-out of ozone-depleting substances, PFCs have been introduced into extremely specialised, high demanding applications only. This low level of conversion is based on the condition that PFCs are only selected if ”high-end” performance, system efficiency and worker safety are mandatory as typical market prices are extremely high for these speciality chemicals (>60 Euro/l, due to the high cost manufacturing these compounds e.g. by electrochemical fluorination).
Manufactures and users have a clear understanding of the atmospheric properties of perfluorocarbons. In adhering to product stewardship principles, suppliers provide PFCs only where they are necessary on the basis of performance and safety and uses limit emissions from those applications.
The following segmentation is documenting typical applications for each compound reviewed with emission relevant specifics information:
Used by the semiconductor industry – CF4 is converted into radicals in plasma with a typical utilisation of 19%. The unconverted portion is intended to be reacted with off-gas treatment methods. Estimated European sales to semiconductor manufacturing companies amount to <105t for 1997. Compared with an emission rate of max. 80%, the CO2 equivalent emissions are estimated as <0,5 Mt.
Used by the semiconductor industry primarily for in-situ chamber cleaning of CVD/PECVD tools. Typical conversion rates in plasma have been around 32% utilisation; however, recent development work has suggested that higher utilisation levels are possible.
Abatement technology is introduced to treat the off-gas stream. Besides direct emission reduction efforts, other technologies are being pursued like optimisation and replacement by other, not-in-kind gases (like NF3 – having a “PFC-like” global warming potential of 10800 (ITH 100a, WMO 1998), but offering the potential for utilisation levels around 85%).
Estimated European sales to semiconductor manufacturing companies <175t for 1997. Compared with an emission rate of max. 70%, the CO2 equivalent emissions are estimated as <1,4 Mt.
C3F8 is being introduced into the semiconductor PECVD process as alternative to CF4 and C2F6 with a utilisation factor of typically 56%.3 The use of perfluorinated gases and optimisation of these processes for existing equipment is preferred by the semiconductor industry as not-in-kind solutions are generally considered less feasible from a performance, safety and cost point of view.
Estimated European sales to semiconductor manufacturing companies are <1t for 1997. A typical emission rate without abatement would be of max. 44%; the CO2 equivalent emissions are estimated <0,01 Mt.
PFC-3-1-10 is used by a few leading physics research institutes across Europe. Key feature here are again the inert characteristic as well as non-flammability providing good operation conditions and equipment reliability. The total European volume in this application is estimated < 5t/a.
PFC-c318 is used by the semiconductor manufacturing industry with estimated European sales volume of <4t for 1999. The product is converted into radicals in a plasma.
PFC-5-11-14 is mainly used as heat transfer fluid. This highly demanding application require good dielectric characteristic at optimum material compatibility and thermal stability. The use as coolant fluid in very specialized applications ensures a close to zero emission into the environment.
Typically, C6F14 was used as interim solution to apply or remove highly fluorinated grease (e.g. PFPE) in the computer hard disk manufacturing. Industry is running an active fluid return and recycling program for above listed applications as part of a product stewardship program, working closely with users to minimise emissions. Nowadays, new solutions are being introduced for all speciality polymer solvent applications.
The total European market for Perfluorohexane is estimated as <200t for 1999 with a downward trend.