Composition and instabilities of Ar/SF/sub 6/ inductive plasma discharges

Summary form only given. We study low-pressure (2 to 10 mTorr), planar, inductive processing discharges operated with Ar/SF/sub 6/ gas mixtures. The plasma source is powered with up to 1 kW, 13.56 MHz radio frequency. Without a Faraday shield between the 3-turn spiral coil and the quartz window, large-amplitude plasma relaxation oscillations (5 to 20 kHz) are observed in an intermediate range of RF power (0.1 to 0.3 kW). Stable capacitive discharges are seen below 0.1 kW, and stable inductive (H) discharges are sustained above 0.3 kW. These observations suggest that the relaxation oscillations might be E-H transitions, a hypothesis supported by a global instability model. We report new data from Ar/SF/sub 6/ plasma discharges concerning plasma chemistry and instability phenomena. These data may permit to modify the instability model to obtain a more quantitative agreement with the experimental observations.