The use of Taguchi method for process design of experiment to resolve gate oxide integrity issue

This paper discusses the process improvements for resolving gate oxide integrity (GOI) issue using the Taguchi method through reliability engineering for eliminating shallow trench isolation (STI) edge failure mode. The selected process parameters are narrowed down to STI/ILD stress, silicide residue, nitride residue, and other surface contaminants. The analysis of S/N ratio show that the most GOI improvement comes from skipped N₂ sacrificial oxide annealing. A systematic process of identifying and assessing the effect on GOI is done through evaluating the characteristic in the optimum condition analysis, whereas typical GOI defect density analysis or its cumulative V_BD distribution plot could not identify the solution. This is because the signal-to noise (S/N) ratio can reflect both the average and variation in quality characteristic. The results suggest that the proposed Taguchi method is an efficient, disciplined approach that can assist a process optimization in improving reliability, particularly gate oxide integrity.