An Approach to Improve Distortion with High-Aspect-Ratio Cryogenic Etching Using BORON-Containing Gases

Cryogenic etching is building a "high-speed railway" in high-aspect-ratio (HAR) channel hole patterning due to its enhanced etch rates and improved profile. However, shape-deformation or circularity distortion of holes appears with increased aspect ratio. Here, we report a novel process associated with boron-containing gas, such as BCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> or BF<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, provide a positive effect on maintaining hole circularity from top to bottom. By tuning addition mode and amount of B-based gas, the hole distortion can be significantly improved even if the temperature is as low as -60C. The findings can provide guidance for process optimization in very high-aspect-ratio etch to meet advanced memory devices.