WEE Residue Elimination for Cross-Link Prone Positive Tone DUV Photoresists

In DUV lithography process, some positive tone photoresists (PR) exhibit negative tone PR characteristics under certain exposure and baking process conditions. Such cross-link reactions cause PR residue on the Wafer Edge Exposure (WEE) zone of the wafer, which becomes a source of defects in downstream manufacturing steps, affecting the electrical performance and yield of products. This paper explores the effects of WEE illumination, post-exposure bake, and developing time on the formation of WEE PR residue. It was found that post-exposure bake temperature had the largest impact on the elimination of WEE residue while WEE illumination and developing time played smaller roles.