Wet Etching Inside Advanced High Aspect Ratio Structures: Impact of Dissolved Oxygen

摘要

The etch of poly-Si by aqueous tetramethylammonium hydroxide (TMAH) was investigated and how the etch rate is affected by the dissolved oxygen (DO) concentration in the solution was modeled. The model shows an excellent capability to predict the DO in the TMAH at different positions on the wafer and to estimate the silicon etch rate at a given location. Experimental results confirm the model predictions. However, DO consumption within high aspect ratio (HAR) features causes different etch rates between the top and bottom of the structure. This difficulty can be solved by controlling the DO concentration inside the HAR features.