Epitaxial silicon growth between scylla and charybdis

The progress of the microelectronics industry depends on ever better control of the surface morphology of the deposited film. This is important for the deposition of both epitaxial and polycrystalline silicon layers. The former is used to obtain high quality semiconductor substrates, while the latter is needed to control the diffusion of impurities towards active layers. In the present work, the CVD of silicon films is examined with the aim of providing evidence of the correlation between process conditions and mechanisms of surface formation. In particular, attention has been focused on the process of terrace-step growth. In this framework, the conditions of cluster formation (preceding the polycrystalline growth), and those of terrace instability (preceding the transition to amorphous film growth), are both investigated. The calculated results are consistent with known information on industrially produced films, and with available pictures of Si surfaces obtained by atomic force microscopy (AFM)-in particular, the increase in cluster dimension when the partial pressure of silane is reduced.