Proximity effect correction for the chemical shrink process of different type contact holes

Abstract

Small contact hole patterning had become the most difficult task in optical lithography as design rule of semiconductor continuously shrinks below 65nm. Conventional contact hole scheme need to avoid side-lobe and conduct complicated dense-isolated bias for resolution enhancement and depth of focus (DOF) improvement. To overcome this issue, some RETs (Resolution Enhancement Techniques) by process had been investigated, like RELACS (resolution enhancement lithography assisted by chemical shrink). RELACS is one of feasible procedures which could provide enough improvement in resolution, photo-resist profile, DOF, and CD uniformity (CDU). Proximity effect is one of significant topics to evaluate chemical shrink bias of different type contacts. Research of shrink bias of different size and pitch contacts had been investigated broadly in the past. In general, the constant bias of shrinkage for difference pattern sizes was an assumption. However, according to our evaluative results, we had characterized the correlation about the shrink bias versus pattern size. In this paper, we not only show DOF, CDU, shrink bias of RELACS, but also present chemical shrink bias of different size and different pitch contact holes and then we could follow this correlation rule to define general rule for proximity effect correction.