Characterization of SiO2 layers on Si wafers using atomic force microscopy layers on Si wafers using atomic force microscopy

The surface roughness, infrared absorption, and index of refraction characteristics of Si02 films prepared with various commonly used techniques are discussed. According to the atomic force microscopy images, thin oxides (100 A or less) have smooth surfaces with an rms surface roughness of about 4 A. The roughness increases slightly with the increase of the film thickness to about 1000 A. Oxide films prepared by low-pressure chemical vapor deposition pyrolytic decomposition of SiH4/02 mixtures, electron-beam (e-beam) evaporation, and microwave plasma decomposition of SiH4/02 gas mixtures exhibit rougher surfaces with an rms surface roughness exceeding 20 A. In particular, the atomic force microscopy images obtained in films prepared by e-beam evaporation and microwave plasma decomposition reveal the presence of microvoids and pinholes which probably facilitate the diffusion of water vapor into the oxide after film deposition. This later aspect was inferred from infrared absorption data which show absorption bands associated with atomic motions of Si-OH and H-O-H groups. © 1994, American Vacuum Society. All rights reserved.

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