NEW TECHNIQUE OF VAR INVESTIGATIONS OF THIN-FILMS ON THICK SUBSTRATES

A new technique of variable angle reflectometry (VAR) investigations o f thin firms on thick, transparent, parallel-sided substrates is prese nted. This technique uses spatial distribution of intensity of reflect ed radiation of a sample illuminated with a light beam of finite diame ter. The experimental results obtained for amorphous silicon (a-Si) we re fitted with theoretical dependencies taking into account the optica l inhomogeneity over the film thickness. This inhomogeneity was descri bed by values nf, af, nb and ab Of the real part of the refractive ind ex and absorption coefficient at the surfaces of the film. The investi gated film was also characterized by the average over its thickness va lues of the real part of the refractive index (n) over bar and absorpt ion coefficient <(alpha)over bar>. For the investigated a-Si n(b) < n( f) < (n) over bar and <(alpha)over bar> > alpha(f) > alpha(b). It can be suggested that the presented investigations of optical inhomogeneit y of thin films of a-Si should be taken into serious consideration for optimized technological conditions. (C) 1998 Elsevier Science Ltd. Al l rights reserved.