Pattern collapse mitigation in inorganic resists via a polymer freeze technique

Abstract

As the lithography feature sizes continue to shrink, the aspect ratios of the patterned resist structures tend to increase as the thickness of the resist cannot be scaled down at the same pace with the resolution. This trend has resulted in the performance of leading photoresists often being limited by pattern collapse rather than their resolution. Even though several pattern collapse mitigation strategies have been successfully introduced, their performance is not sufficient to completely mitigate the issue. Here, we present a pattern collapse mitigation technique for inorganic resists, where the root cause of pattern collapse, the capillary forces present during the drying of the wafers, is circumvented by encapsulating the resist in a polymer film instead of drying it and removal of the polymer in a subsequent dry etch process. We demonstrate how the technique increases the aspect ratio of freestanding resist structures, expanding the process window towards smaller doses for resist patterned both via extreme ultraviolet interference lithography and electron beam lithography.