The Influence of Frequency and Pressure on the Material Quality of PECVD A-SI:H

Abstract

ABSTRACTA systematic study of material quality has been performed for a-Si:H layers deposited by plasma enhanced chemical vapour deposition at frequencies between 30–80 MHz. The effect of frequency variation was studied in combination with the variation of pressure and power density. The process conditions were optimised not only for ‘device quality’ opto-electronic properties but also for a uniformity in layer thickness better than 5 %. For every frequency an optimum pressure exists for which the properties of the deposited layer satisfy the ‘device quality’ requirements. A clear correlation is observed between the transition from the so-called α- to the γ-regime of the plasma and the dependence of the deposition rate γd with pressure pand frequency ƒ: γ d ∝ pƒ2/3.