Experimental study of Si3N4 viscosity for calibration of stress-dependent models of silicon oxidation

Basic parameters characterizing silicon nitride viscosity have been obtaine d from experiments on Si3N4 films. Changes in film thickness and intrinsic stress after various types of high-temperature annealing have been studied. A considerable stress increase during a temperature ramp-up is attributed to film structure densification. The contribution of the ramp-up and ramp-d own stages of annealing to film shrinkage was excluded from the calculation s of nitride viscosity. The resulting viscosity is higher than previously r eported. Based on the experimentally obtained viscosity values, the process of local oxidation of silicon (LOCOS) was simulated. The viscosity of ther mal oxide and stress-dependent parameters of the viscoelastic oxidation mod el were extracted by comparing the simulated boundary geometry of LOGOS str uctures with cross-sectional scanning electron microscopy images. It is fou nd that the enhancement of oxidant diffusion in oxide regions subjected to tensile stress is a major cause for the increase in pad oxide thickness und er a narrow nitride mask during field oxidation. (C) 1999 The Electrochemic al Society. S0013-4651(98)12-050-5. All rights reserved.