Effect of Stress on Oxide Edge Shape of Local Oxidation of Silicon for Various Oxidation Temperatures

Transmission electron microscopy and oxidation simulation based on the viscoelastic model were used to study oxide edge shapes during the local oxidation of silicon. Upon reducing the pad oxide thickness, local retardation of oxide growth, resulting in pinched shapes, was observed at field oxide edges at oxidation temperatures below 1000° C, and {111} interfaces between silicon dioxide and silicon were found to be formed at temperatures above 1000° C. These characteristic shapes were discussed in terms of the viscous flow of oxide, the simulated uniaxial stress in oxide during oxidation and the distortion energy of the interface. It was concluded that pinched shapes were formed by the anisotropic diffusion of oxidants and {111} interfaces resulting from the reaction of minimizing the distortion energy of the interface.