Atmospheric-pressure plasma jet system for silicon etching without fluorocarbon gas feed

We developed an atmospheric-pressure plasma jet (APPJ) system with a tungsten rod electrode coated with C2F4 particles of approximately 0.3 mu m diameter for the surface treatment of a silicon wafer. The APPJ was generated by dielectric barrier discharge with a driving frequency of 22 kHz using a He gas flow. The characteristics of the APPJ were examined under various experimental conditions. The plasma jet length increased proportionally to the electric field. It was found that the treatment area of the silicon wafer was approximately 1 mm in diameter. By atomic force microscopy analysis, minute irregularities with a maximum length of about 600 nm and part of a ring-shaped trench were observed. A Si etching rate of approximately 400 nm/min was attained at a low power of 6 W and a He flow rate of 1 L/min without introducing molecular gas including F atoms. (c) 2018 The Japan Society of Applied Physics