Epitaxial silicon growth between scylla and charybdis

The progress of the microelectronics industry depends on ever better contro l of the surface morphology of the deposited film. This is important for th e deposition of both epitaxial and polycrystalline silicon layers. The form er is used to obtain high quality semiconductor substrates, while the latte r is needed to control the diffusion of impurities towards active layers. I n the present work, the CVD of silicon films is examined with the aim of pr oviding evidence of the correlation between process conditions and mechanis ms of surface formation. In particular, attention has been focused on the p rocess of terrace-step growth. In this framework, the conditions of cluster formation (preceding the polycrystalline growth), and those of terrace ins tability (preceding the transition to amorphous film growth), are both inve stigated. The calculated results are consistent with known information on i ndustrially produced films, and with available pictures of Si surfaces obta ined by atomic force microscopy (AFM)-in particular, the increase in cluste r dimension when the partial pressure of silane is reduced.