Time-resolved probe diagnostics of pulsed DC magnetron discharge during deposition of TiOx layers

Abstract

The paper presents an experimental study of a pulsed DC unbalanced magnetron discharge with Ti target. This system is being used for deposition of nanocrystalline TiOx thin films. The unbalanced magnetron was operated in pulsed regime with the low repetition frequency of modulation cycle νp=250 Hz and relatively short active part of modulation cycle Ta=150 μs. Low average discharge current was used with maximum value about 1 A. Maximum instant discharge current in the active part of modulation cycle was 20 A. Relatively high plasma density up to value ne≈1018 m−3 was achieved at these conditions but due the low average power absorbed in the plasma the heat load applied on the target and the substrate was low. Time-resolved and spatially resolved Langmuir probe diagnostics was used for the systematic and detailed experimental study of the system. Experimental conditions as the instant value of discharge current, gas pressure in the reactor, gas mixture ratio Ar/O2, etc. were varied in a broad range. The time evolutions of plasma parameters such as electron density, electron temperature, plasma potential and EEPF were determined during the modulation cycle of pulse discharge excitation.