The combination of two growth methods for the epitaxial deposition of silicon films on insulating substrates

Abstract

Thin epitaxial silicon films (0.5–3 μm) on spinel and sapphire are produced by using a combination of two growth methods. After complete coverage of the substrate surface with silicon by decomposition of silane with a high deposition rate (e.g. 2–3 μm/min), hydrogen chloride is added to the gas stream without changing the silane amount. By the first step reactions between silicon and the substrate surface are reduced to a minimum. During the second step the net growth rate decreases to ≈0.3 μm/min. Silicon layers grown by this process are more homogeneous and perfect than films of equal thickness grown with a constant rate. The better quality is connected with lower optical absorption coefficients and increase in silicon surface smoothness. The silicon growth rate as a function of the hydrogen chloride flow is in good agreement with theoretical and experimental results already published in literature.