Some growth peculiarities of a-C:H films in ECR microwave plasma

Abstract

The chemical vapor deposition (CVD) process of a-C:H films from methane and argon gas mixtures in an electron cyclotron resonance (ECR) microwave plasma has been studied. The formation of a-C:H films in a wide range of basic parameters has been investigated. The basic parameters are the following: the total pressure of the working gas mixture, the composition of the gas mixture, the magnitude of microwave power absorbed in a plasma, the location of the substrate L ECR-S with respect to the position of ECR and substrate material (Si, ceramic). We found that extremely low or zero growth rate of the a-C:H films takes place in the cases when (i) the substrate is placed in the ECR plane or its close vicinity and (ii) a high microwave power is used; the latter situation occurs when the power is about 300 W or greater. The increase in deposition rate takes place under the increase of the L ECR-S distance or under the decrease of the microwave power. The deposition rate of a-C:H films on the ceramic substrate was higher than that on the silicon substrate for all values of operating pressure. These peculiarities are explained in terms of additional heating of Si substrates by microwave power absorption outside the ECR region. A later (latent) parameter should be taken into account in the analysis of the deposition process and choice of the substrate material. The mechanism leading to a very high growth rate of a-C:H polymer-like films is discussed.