Resist material for negative tone development process

Methods for improving lithography performance with optimization of resist materials and formulation for negative tone development (NTD) process are discussed. Narrow pitch lithography performance comparison with NTD and PTD process for initial platform for NTD revealed the not enough maturity of the resist for NTD. Dissolution rate study suggested the optimizations of molecular weight and solvent parameter to NTD process are important to improve dissolution property. Larger dissolution rate and larger γ value in contrast curve gave larger process window at 40 nm half pitch dense contact hole pattern with double exposure and single development step.