Atomic Force Microscopy Investigation of Tensile-Stressed Silicon Grown by Rapid Thermal Chemical Vapour Deposition on Si0.68Ge0.32 Relaxed Pseudo-substrates

Abstract

Rapid thermal chemical vapour deposition (RTCVD) has been applied to the growth of silicon layers under tensile stress on relaxed Si0.68Ge0.32 buffer layers at 610 and 810°C. Their surface morphology was characterised with atomic height resolution by Tapping-mode atomic force microscopy (TM-AFM). While a uniform isotropic nanoroughness is revealed on pseudo-substrates, a quite different roughness can be observed for silicon films. For high temperature grown films, high surface diffusion rates of adsorbed species enable an extended reconstruction of the Si (100) surface: large domains showing terraces as well as faceted planes appear; the resulting non-uniform silicon film exhibits early mechanical failure. In contrast, low temperature grown Si films exhibit almost the same morphology as pseudo-substrates for thicknesses up to 15 nm with no apparent mechanical failure. For thicknesses beyond 20 nm, terraces form on the steepest part of the slopes, whereas beyond 80 nm <110> slip lines indicate the plastic yield of the film.