IN-SITU RHEED AND AFM INVESTIGATION OF GROWTH FRONT MORPHOLOGY EVOLUTION OF SI(001) GROWN BY UHV-CVD

We have successfully demonstrated the applicability of in-situ reflect ion high-energy electron diffraction (RHEED) to investigate the atomic -scale growth mechanisms in chemical vapor deposition (CVD). Measureme nts of surface structure and morphology of Si(100) films have been mad e in-situ by differentially pumped RHEED and compared ex-situ with ato mic force microscopy (AFM). We use RHEED to examine the film morpholog y and structure; such as to distinguish two-dimensional growth (2D) fr om three-dimensional growth, and for the latter the formation of facet s, twins, and polycrystalline morphology, all of which have been obser ved during CVD grown Si from SiH4. In the temperature range of 550 to 650 degrees C, the silicon epitaxial growth was found to be initiated either by the formation of three-dimensional (3D) islands, which coale sce 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 o f a disordered 2 X 1 reconstruction and a c(4 X 4) reconstruction. Ato mic force microscopy (AFM) measurements performed ex-situ on the epita xial films confirm the RHEED observations and give the morphology evol ution at various growth conditions.