ELECTRON-CYCLOTRON-RESONANCE PLASMA ION-BEAM EFFECTS ON THE FORMATIONOF SIC ON SI(001) CHARACTERIZED BY IN-SITU PHOTOEMISSION

Nanometric SiC overlayer synthesis has been performed via an ultrahigh vacuum-compatible microwave electron cyclotron resonance plasma sourc e. The H-2 plasma streaming onto a Si(001) substrate, whose temperatur e T(s) could be varied from room temperature to 850-degrees-C, activat es and dissociates CH4 molecules. The films are characterized in situ by angle-resolved photoemission techniques. Without the H-2 plasma, no surface reaction of CH4 is observed with the Si irrespective of T(s) up to 850-degrees-C and exposures up to 10(6) L. H-2 plasma excitation leads to the rapid formation of a thin SiC overlayer in the whole T(s ) range. For temperatures below a threshold of about 700-degrees-C whe re thermal interdiffusion between Si and C is negligible, the SiC over layer thickness rapidly saturates in the nanometric range and the SiC formed is not structured. This thickness is essentially determined by ion penetration in the substrate which can be increased by negative bi asing. Above this T(s), SiC growth increases rapidly and the film beco mes textured near 800-degrees-C, as the growth of beta-SiC(001) aligne d with Si(001) can be observed. The SiC topmost-layer structure is cri tically dependent on the plasma conditions with respect to the thermal processing at the film growth interruption. When the plasma is switch ed off before heating, the surface is essentially Si rich and oxidizab le. In the opposite case, the H-2 plasma etches the Si-terminated over layer and passivates the surface.