Negative resist corner rounding. Envelope volume modeling

Abstract

A pronounced feature of negative resist developed profiles is corner rounding. Almost all of the current resists are composed of polymeric materials and negative resists depend on cross-linking during exposure for feature delineation after development. The envelope sphere polymer molecule modeling describes the creation of the rounded profile at corners of resist lines during dissolution. A cellular automata dissolution model incorporates the envelope model, simulates the mechanics of the etching process, and predicts the corner rounding. We used Shipley SNR-248 negative resist for the experimental profiles. The experimental results confirm the dependence of the dissolution rate Eri,j on the differential etch rate between exposed and unexposed regions (volumes) of the resist. High postexposure bake temperatures and higher development environment temperatures modify the profiles.