Generation of 50-kHz large area induction thermal plasma for high rate, uniform processing

Numerical and experimental approaches were made to produce a large area induction thermal plasma as a basic technology for high rate, uniform processing of materials. A high-power 50-kHz magnetic field was applied to a small dc plasma as a source of charged particles and a transient expansion of it was initiated in the radial direction. The time necessary to reach a new steady state plasma with a larger diameter of 100 mm was found to be around 20 and 2 ms, and the minimum sustaining power for the plasma to be 65 and 25 kW under the plasma pressure of 100 and 10 kPa, respectively. Experiments were performed to produce a 100-mm diameter plasma under a soft vacuum condition of 10 kPa. At a plate power level of 60 kW, the 50-kHz magnetic field was coupled with a small source plasma and expanded it successfully to a wide plasma of 100 mm in diameter. The temperature of the induction plasma was uniformly distributed and estimated as around 10000 K by spectroscopic analysis.