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We have examined in detail the role of the Xe additive in microwave plasma-assisted {CH4+H2} chemical vapor deposition (CVD) of diamond film. Effects of Xe addition were evident in the increased growth rate (about 50% increase for 1% Xe), without degradation of the crystallinity, and in the morphological change from the cubic to platelet grain structures. Based on the results of measuring the plasma emission spectra, Raman shift, and microwave plasma impedance, the favorable effects of Xe addition were attributed to its low dissociation and excitation energies (8.28 eV for Xe radicals), which are sufficient for the formation of CH3 but not CH2 radicals. Namely, the addition of Xe caused the CVD plasma to have higher density and lower temperature. This resulted in a large amount of atomic hydrogen and CH3 (precursors for diamond crystallization) and also a smaller amount of CH2, leading to the growth of a good-quality diamond film with a high deposition rate.

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An automatic microwave stub tuner (AST) has been developed and used to characterize and stabilize an electron-cyclotron resonance (ECR) plasma source. The tuner provides a new method for measuring plasma impedance dynamically without disturbing the plasma. The Ar ECR plasmas were excited by a 2.45 GHz microwave (<800 W) in the presence of the static axial magnetic fields ranging from 875 to 2000 G, and the characteristics were investigated using a double probe and the AST. Results of these measurements indicated that the Ar ECR plasma had discrete stable modes where the plasma parameters and impedance varied continuously. For certain operating conditions, slight shifts of microwave power and/or magnetic-field strength brought about discontinuous mode transitions. In the transition regions, the drastic changes of plasma characteristics were observed, resulting in the instability of the plasma. It was quite effective for stabilizing the unstable plasmas to control the reflection coefficient of the microwave transmission line.

The Ar-electron-cyclotron-resonance (ECR) microwave (MW) plasma has been applied on GaAs surfaces for investigating the effects of radio-frequency bias on etching reaction and radiation damage. The etch depths as a function of the etching time gave a linear profile with etch rates of 75 and 100 Å/min for 150- and 300-W MW powers under a 4-W rf bias, respectively, but for the etch rates an exponential profile is obtained as a function of the square root of the rf bias power. The electrical characteristics of Schottky barriers fabricated on the etched surface show strong rf bias dependence. Increasing the rf bias power, the donor concentration near surface and the barrier height decrease but the ideality factor and the depletion layer width increase monotonically. The changes are attributed to the radiation damage induced by the Ar ECR plasma which becomes gradually deeper in the damage layer and higher in concentration with increasing rf bias power. The rf biasing in the ECR plasma (which has the exceptional characteristic of being applicable to semi-insulating specimens) is very similar in effect to dc biasing.