High-Rate Deposition of a-Si:H Films in 55 kHz Glow Discharge: Growth Mechanisms and Film Structure

Abstract

ABSTRACTThe 55 kHz GD technique allowed the high-rate deposition of a-Si:H films (up to 30 A/s) with good electronic properties in spite of inhomogeneous structure. In this work, we investigated the growth mechanisms and the correlation between plasma parameters and film structure. The electrical parameters of discharge, the properties of plasma and of the films were investigated with using of wide range of methods (optical emission spectroscopy, mass-spectrometry, IR-spectroscopy, atomic force microscopy).The films were deposited in an industrial reactor of diode type with both non-grounded electrodes used as substrate holders. The deposition mechanism in this case includes the alternation of growth phases when the negatively charged particles reach the anode (at a moment) during the first half-period of an oscillation of electric field, and the improvement of growing surface under the influence of the bombardment by positive ions during the second half-period. It is shown that the increase of the power increases the ionic flux leading to the increase of the size of structural inhomogeneities. The pressure influences the energy of positive ions, and, therefore, the hydrogen content and its bonding form on the growing surface.