Developer effect on the negative tone development process under low NILS conditions

The effect of solvent developers on the negative tone development process was studied in both dry and immersion 193 nm lithography. While acetate-based solvent developers yielded sharp thickness contrasts with a minimum resist thickness loss, severe missing contact holes were observed under lower image-log slope conditions. In contrast, ketone-based solvent developers yielded excellent contact hole performance under poor aerial image conditions without the formation of missing contact holes. However, it was observed that ketone-based solvent developers can cause poor thickness contrasts with more resist thickness loss. By using additives in the ketone-based developers, it was possible to tailor various resist performance parameters such as photospeeds, critical dimension uniformity, resist thickness retention, and dissolution rate contrasts. It was found that higher dissolution rate contrast can give better uniformity in the critical dimension, better thickness retention and less missing contact holes.