Diamond growth in and above trenches in silicon

Abstract We have investigated the deposition of diamond films onto trench structures in silicon substrates with different aspect ratios (i.e. depth to width ratios). Deposition has been performed by microwave plasma-assisted CVD preceded by an in situ bias pretreatment to support nucleation. For comparison, bias pretreated samples have been coated ex situ by hot filament CVD and a hollow cathode arc discharge technique, respectively. The experimental observations suggest that diamond grows in the trenches with a nearly constant deposition rate until the moment when the diamond film above the trench is completely closed. Cross-sectional Raman spectroscopy has been applied to get a view inside trenches. These measurements have revealed differences in phase purity of diamond which has been deposited at distinct stages of growth. In general, very similar results have been achieved with the three different deposition techniques applied. Differences in film structure can be explained, assuming that diamond growth is controlled by the diffusion of hydrocarbons and atomic hydrogen from the plasma to the bottom side of the trench.