Negative resist corner rounding. Envelope volume modeling

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 Er-i,Er-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. (C) 1996 American Vacuum Society.