Feasibility using ethanol-added argon instead of helium as the carrier gas used in atmospheric-pressure plasma chemical vaporization machining

Abstract

As a highly efficient noncontact chemical ultraprecise figuring technique, atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) using helium as a carrier gas has been practically applied to improve the thickness uniformity of quartz crystal wafer. Because of the high cost and limited supply of helium, it is necessary to find a substitute for helium. As is well known, argon plasma at atmospheric pressure form arc streamers easily due to the high breakdown voltage. But it has been reported that the addition of a small amount of ethanol makes it possible to generate a stable glow discharge atmospheric-pressure argon plasma. In this report, feasibility of using ethanol-added argon instead of helium as the carrier gas used in AP-PCVM was investigated. A uniform, stable glow discharge CF4 plasma was generated by applying the ethanol-containing process gas. Comparative experiment was conducted on quartz crystal wafer by AP-PCVM using helium and ethanol-added argon as carrier gas. As the result, using ethanol-added argon as the carrier gas in AP-PCVM instead of helium, the same etching rate was obtained and the operation cost was reduced.