Low-temperature reaction of CH4 on Si(100)

Surface reaction of CH4 on the Si(1 0 0) epitaxial surface was investigated in the low-temperature region of 500-750 degrees C at 50-1600 Pa for 7-240 min using an ultraclean vertical-type hot-wall LPCVD system. In the case of the CH4 exposure at greater than or equal to 650 degrees C, the reacted C atom diffused into Si and a SIC layer was formed. At less than or equal to 550 degrees C, CH4 reacted with Si only at the surface without apparent diffusion, and the 4-fold periodic structure toward the [0 0 1] azimuth was formed on the surface. At 600 degrees C, with increasing exposure time, the 4-fold periodic structure was initially formed and then disappeared and the diffraction spots of SiC appeared, which indicates substantial diffusion of the reacted C atom into Si. Furthermore, at less than or equal to 600 degrees C, the reacted C atom concentration at the outermost surface was normalized with the product of the CH4 pressure and the exposure time, and was expressed by the Langmuir-type rate equation. (C) 1998 Elsevier Science B.V. All rights reserved.