Electron energy distributions in electron cyclotron resonance discharges for materials processing

Abstract

Electron cyclotron resonance (ECR) reactors are now being investigated for use in the plasma processing of semiconductors. The attractive feature of ECR excitation is that high plasma densities (1010–1012 cm−3) can be obtained at low pressures (0.1–a few mTorr). In this paper, we present results from a computer simulation of the electron kinetics in ECR reactors. The model is a multidimensional Monte Carlo simulation coupled with a fluid simulation with which the electron energy distribution (EED) may be calculated. We find that the electron temperature (Te =2/3〈ε〉) in Ar plasmas (0.1–10 mTorr, 100s W) is 10–20 eV in the ECR zone, falling to a few to 5 eV downstream of the ECR zone, in general agreement with experiments. The EED can be described as being multitemperature with a low energy component (5–10 eV) and a high energy tail extending to many 10s to 100s eV. Predicted ambipolar potentials are 10–30 V, increasing with decreasing pressure and increasing power deposition.