Trench Punch Study for Two Different Material Interface

Punch process is a method to etch high-aspect-ratio bottom layer without top damage. The structure of punch process is usually cyclic dep/etch/strip. People are more focused on pillar punch while the trench punch is rarely studied. This article studies trench punch with two different material interface, poly silicon and Silicon Nitride. It means that it is important to care not only what it is cared in pillar punch, but also the selectivity of poly and nitride. Moreover, boundary damage is studied in the article and two possible solutions are proposed.