The Investigation of CF3I For High-Aspect-Ratio Cryogenic Dielectric Etch

Considering the high surface adsorption capacity in cryogenic condition, we can achieve high etch rate, good bottom circularity and less risk of chamber arcing for high-aspect-ratio etch, by using C1 gases and lower power. However, the strategy will cause top layer blowing out and sharp etch front. We here explore a specific gas, CF3I, to deposit on side-wall. It can significantly decrease bowing while results in the reduced etch rate and mask. By tuning source and bias power, we can further enlarge etch front and mitigate the negative effect of CF3I.