Production of a large-area argon microwave plasma by a ring slot antenna

Abstract

A large-area, uniform, low-temperature and high-density microwave argon plasma is produced using a simple flat ring slot antenna without a magnetic field. The plasma production is based on the absorption of the energy of microwave propagating in the dielectric plate (quartz glass) along the plasma surface. The power is coupled to the dielectric plate by azimuthal symmetrical mode. An electron density of >10 11/cm 3 with an electron temperature <2 eV, and a floating potential with respect to the vacuum chamber wall of <4 V are obtained at 5 mTorr with 2.45 GHz, peak input power of 500 W (duty ratio t/ T=0.5; pulse width t=50 μs, and period T=100 μs). A high ion current density (over 10 mA/cm 2) of uniformity (standard deviation/average) within ±3% over 24 cm diameter is achieved.