The Influence of Processes on Composition of Thermally Nitrided SiO2 Film

Abstract

The influence of process conditions, involving both oxidation and nitridation, on the results of nitridation of have been investigated. The initial oxides grown by LP, dry and wet oxidations to 200–500Å have been nitrided in either a directly heated reactor or an RF‐heated reactor. Systematic AES analyses show that by utilizing appropriate processing techniques, different distributions of nitrogen and nitrogen‐oxygen ratios can be obtained. The results demonstrate that both a low oxidation rate and a low initial nitridation rate will give a higher amount of nitrogen and a higher nitrogen‐oxygen ratio in the nitrided film. The Auger results also indicated that at the early stage of nitridation Si‐O bonds were partially broken and reactions between pure and/or partially unbonded Si and nitridizing agents had occurred. The results of post nitridation annealing show that the nitrogen in a nitrided oxide film can be further redistributed at an elevated temperature, and the nitridation reactions in the surface and bulk regions are reversible. A multilayer model is proposed to explain the kinetics of nitridation. With this model, the different nitrogen profiles and nitrogen‐oxygen ratios for different process conditions are clarified and the influence of the processes can be predicted qualitatively.