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 mere used to study oxide edge shapes during the lo cal oxidation of silicon. Upon reducing the pad oxide thickness, local retardation of oxide growth, resulting in pinched shapes, was observe d at field oxide edges at oxidation temperatures below 1000 degrees C, and {111} interfaces between silicon dioxide and silicon were found t o be formed at temperatures above 1000 degrees C. These characteristic shapes were discussed in terms of the viscous how of oxide, the simul ated uniaxial stress in oxide during oxidation and the distortion ener gy of the interface. It was concluded that pinched shapes were formed by the anisotropic diffusion of oxidants and {111} interfaces resultin g from the reaction of minimizing the distortion energy of the interfa ce.