Evolution of Negative Tone Development Photoresists for ArF Lithography

The negative tone development process enables the printing of dark field features on wafer using bright field masks with a manufacturing capability for back-end-of-line processing. The performance of NTD photoresist has advanced along two fronts: namely common process window for dense and semi-dense contacts and the resolution and line width roughness of isolated trenches. Furthermore, the chemistry has evolved by the convergence of capability for printing line/space and contact hole using a single photoresist formulation. The process performance of a series of NTD photoresist is reported. Particular focus is placed on process latitude, CDU, thickness control, LWR and resolution limit.