Hydrogen-mediated low-temperature epitaxy of Si in plasma-enhanced chemical vapor deposition

Low-temperature epitaxy LTE.of crystalline silicon in the plasma-enhanced chemical vapor deposition PECVD.was investigated using in situ observation of reflection high energy electron diffraction RHEED.. Source gases of SiH4and H2 mixture were decomposed by radio-frequency RF.glow discharge, and an epitaxial layer was grown on a p-type Si 001. substrate at a variety of hydrogen dilution ratios, R wH2xqwSiH4x.rwSiH4x4, ranging from 10 to 200, and at substrate temperatures, Ts , ranging from 278C to 5608C. Critical thickness of epitaxy above which polycrystalline growth starts to occur shows two peaks as a function of growth temperature at 1208C and 4308C. The lower temperature peak appeared at 1208C and the surface has a 1=1 structure covered by SiH2, while at the higher temperature peak of 4308C the surface has a 2=1 1=2.double domain structure along dimmer rows covered by SiH. In addition, at 4308C, RHEED intensity oscillation with an oscillation period of monolayer was observed. This implies a layer-by-layer growth in the PECVD, and suggests a presence of the surface diffusion of film precursors on the hydrogen-terminated surface. These results are explained in terms of the hydrogen-mediated enhancement of crystal growth corresponding to surface hydride mode. q2000 Published by Elsevier Science B.V.