Simulation of negative tone development (NTD) resist has become a challenge for physical resist modeling. Traditionally, resist modeling was mainly limited to reaction-diffusion models for post exposure bake (PEB) and standard development rate models for simulating the pattern formation during the final development step. With some minor extensions, this simulation approach sufficiently predicted resist CDs and resist profile shapes that were in agreement with experimental data.3 For the latest NTD resists, this situation has changed. In contrast to positive tone development (PTD) resists, resist shrinkage is strongly impacting resist profile shapes. Furthermore, NTD resists induce strong proximity effects that require consideration of additional chemical resist properties in modeling and model calibration. In this paper we experimentally characterize and model the main properties of NTD photo-resists.
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