Photoresist residue defect by etch byproduct on PIP etch process

Abstract

This paper shows the study of the effect of etch by product towards photoresist residue defect found in Polysilicon-Insulator-Polysilicon (PIP) processes. Initial finding show the correlation with the big size poly PIP capacitor structure. Therefore, the challenge was to focus on big size PIP structure. But during partition check, we found the weakness of the photoresist stripping during O2 plasma ashing. The weakness show not only big size pattern but also small size area. Through EDX analysis, we found Si byproduct block oxygen reaction with photoresist. As a consequence, following sulfuric clean has no margin to remove all photoresist which cause photoresist residue on big size of pattern. Several approaches were carried out to identify the optimal solution for defect removal. And, it was found that the additional sulfuric clean without HF is best solution. The photoresist residue defect was then eliminated completely with the new cleaning condition.