7. Stress Dependent Oxidation

STRESS is essential for thermal oxidation, because the oxidation process is considerably influenced by stress. Stress is always built up, if the volume increase of the new oxide is prevented somewhere from expanding as desired. During the oxidation process there can be a lot of stress sources like nitride masks, adjacent structures or oxidation of concave corners.

The oxidation process is stress dependent, because stress has an impact on the oxidant diffusion and the chemical reaction, which are both strongly reduced with stress and so the oxidation rate is also decreased in areas with compressive stress. For high stresses the oxidation process can be de facto even stopped. Thereby, for the simulation of stress dependent oxidation the model from Chapter 3 must be extended. In this chapter also the influence of stress is investigated with this extended model and the simulation results of representative examples are shown.