DIAMOND GROWTH IN AND ABOVE TRENCHES IN SILICON

We have investigated the deposition of diamond films onto trench struc tures in silicon substrates with different aspect ratios (i.e. depth t o width ratios). Deposition has been performed by microwave plasma-ass isted CVD preceded by an in situ bias pretreatment to support nucleati on. For comparison, bias pretreated samples have been coated ex situ b y hot filament CVD and a hollow cathode are discharge technique, respe ctively. The experimental observations suggest that diamond grows in t he trenches with a nearly constant deposition rate until the moment wh en the diamond film above the trench is completely closed. Cross-secti onal Raman spectroscopy has been applied to get a view inside trenches . These measurements have revealed differences in phase purity of diam ond which has bees deposited at distinct stages of growth. In general, very similar results have been achieved with the three different depo sition techniques applied. Differences in film structure can be explai ned, assuming that diamond growth is controlled by the diffusion of hy drocarbons and atomic hydrogen from the plasma to the bottom side of t he trench. (C) 1997 Elsevier Science S.A.