Towards a multiscale approach to the growth of silicon films by chemical vapor deposition

The morphological control of the surface of deposited films is one of the key points in the development of the microelectronics technology, in the field of epitaxial as well as polycrystalline silicon growth. Nowadays, the growth rate profiles are almost optimized, while the surface morphology is still controlled almost empirically only. In this work, the growth of silicon films under CVD conditions is examined, in particular analyzing the terrace-step-growth mechanism. The growth process involves diffusive and kinetic steps, which obviously occur at different length scales. Our attention is focused on the processes occurring on the surface, ignoring the gas-phase reactions, and evaluating the mass transport implications through a simplified model. In this way, the micro- and macro-scale are investigated with two different approaches and afterwards they are linked together in a “toy reactor model”. It becomes then possible to evidence the correlation between the process conditions and the mechanism of surface formation. The conditions of cluster formation, preceding the polycrystalline growth and those of terrace instability, preceding the transition to amorphous film growth are both considered. The information on the industrially produced films and the available pictures of the surface obtained by atomic force microscope confirm the theoretical findings.