In situ RHEED and AFM investigation of growth front morphology evolution of Si(001) grown by UHV-CVD

Abstract

We have successfully demonstrated the applicability of in-situ reflection high-energy electron diffraction (RHEED) to investigate the atomic-scale growth mechanisms in chemical vapor deposition (CVD). Measurements of surface structure and morphology of Si(100) films have been made in-situ by differentially pumped RHEED and compared ex-situ with atomic force microscopy (AFM). We use RHEED to examine the film morphology and structure, such as to distinguish two-dimensional growth (2D) from three-dimensional growth, and for the latter the formation of facets, twins, and polycrystalline morphology, all of which have been observed during CVD grown Si from SiH 4. In the temperature range of 550 to 650°C, the silicon epitaxial growth was found to be initiated either by the formation of three-dimensional (3D) islands, which coalesce and result in two-dimensional (2D) growth, or by the formation of 2D islands that continue to grow in a 2D mode. The 2D phase consists of a disordered 2 × 1 reconstruction and a c(4 × 4) reconstruction. Atomic force microscopy (AFM) measurements performed ex-situ on the epitaxial films confirm the RHEED observations and give the morphology evolution at various growth conditions.