Etching Characteristics of Quartz Crystal Wafers Using Argon-Based Atmospheric Pressure CF4 Plasma Stabilized by Ethanol Addition

Abstract

Atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) using helium as a carrier gas to achieve uniform thickness of quartz crystal wafers has been practically applied to the mass production of high-performance crystal units. However, because of the high cost and limited supply of helium, the proposed use of argon instead of helium has garnered interest. Argon plasma at atmospheric pressure tends to become unstable, but it has been reported that the addition of a small amount of ethanol makes it possible to generate a stable and uniformly spread glow discharge atmospheric-pressure argon plasma. In this study, an AP-PCVM experiment was conducted on quartz crystal wafers using an argon-ethanol mixture gas as the carrier gas and CF4 and O2 as process gases. A uniform, stable glow discharge plasma was generated by applying the ethanol-containing process gas, and satisfactory removal characteristics for correcting the thickness deviation of a quartz crystal wafer were obtained.