CHARACTERIZATION OF SIO2 LAYERS ON SI WAFERS USING ATOMIC-FORCE MICROSCOPY

The surface roughness, infrared absorption, and index of refraction ch aracteristics of SiO2 films prepared with various commonly used techni ques are discussed. According to the atomic force microscopy images, t hin oxides (100 angstrom or less) have smooth surfaces with an rms sur face roughness of about 4 angstrom. The roughness increases slightly w ith the increase of the film thickness to about 1000 angstrom. Oxide f ilms prepared by low-pressure chemical vapor deposition pyrolytic deco mposition of SiH4/O2 mixtures, electron-beam (e-beam) evaporation, and microwave plasma decomposition of SiH4/O2 gas mixtures exhibit roughe r surfaces with an rms surface roughness exceeding 20 angstrom. In par ticular, the atomic force microscopy images obtained in films prepared by e-beam evaporation and microwave plasma decomposition reveal the p resence of microvoids and pinholes which probably facilitate the diffu sion of water vapor into the oxide after film deposition. This later a spect was inferred from infrared absorption data which show absorption bands associated with atomic motions of Si-OH and H-0-H groups.