Real-time monitoring of the growth and decomposition of SiO2 layers on Si(001) by a combined method of RHEED and AES

The growth and decomposition of SiO2 layers on a Si(001) surface were inves tigated by a real-time monitoring method of Auger electron spectroscopy com bined with reflection high energy electron diffraction (RHEED-AES). Using t he RHEED-AES method, the SiO2 coverage and SiO2/Si interface roughness were observed simultaneously in addition to the surface structure and morpholog y. The time evolution of O KLL Auger electron intensity at an O, pressure o f 2X10(-7) Torr shows that passive oxidation (SiO2 growth) is divided into two regions of Langmuir-type adsorption and two-dimensional island growth a t about 630 degreesC, and that passive oxidation changes to active oxidatio n (etching) at about 750 degreesC. In the two-dimensional island growth reg ion of 630-750 degreesC, RHEED spots of Si bulk diffraction appear, indicat ing that the SiO2/Si interface is roughened to form protrusions under SiO2 islands. During SiO2 decomposition in vacuum, the interface is further roug hened, resulting in a formation of depressions. Based on the correlation be tween the time evolutions of SiO2 coverage and interface roughness, a surfa ce reaction model of Si thermal oxidation is discussed. (C) 2001 Elsevier S cience B.V. AU rights reserved.