Geometric structure of thin SiOxNy films on Si(100)

Thin films of amorphous stoichometric SiOxNy are deposited on radiation-heated Si(100) by rapid thermal low-pressure chemical vapour deposition. We studied the whole range of possible compositions. In order to determine the geometric structure, we used EXAFS and photoelectron spectroscopy. Tetrahedrons constitute the short-range units with a central Si atom connected to N and O. The distribution of the possible tetrahedrons can be described by a mixture of the Random Bonding Model and the Random Mixture Model. For low oxygen contents x/(x+y) less than or equal to 0.3, the geometric structure of the film is almost the structure of a-Si3N4, with the oxygen preferably on top of Si-N-3 triangles. Higher oxygen contents induce changes in the bond lengths, bond angles and coordination numbers. (C) 1998 Elsevier Science B.V. All rights reserved.