Radial segmentation approach for contact hole patterning in 193 nm immersion lithography

Abstract

In this paper, a novel optical proximity correction (OPC) method for contact hole patterning is demonstrated. Conventional OPC for contact hole patterning involves dimensional biasing, addition of serifs, and sub resolution assist features (SRAF). A square shape is targeted in the process of applying conventional OPC. As dimension of contact hole reduces, features on mask appear to be circular due to strong diffraction effect. The process window enhancement of conventional OPC approach is limited. Moreover, increased encounters of side lobes printing and missing contact holes are affecting the process robustness. A new approach of changing the target pattern from square to circular is proposed in this study. The approach involves a change in shape of mask openings and a radial segmentation method for proximity correction. The contact holes patterns studied include regular contact holes array and staggered contact holes. Process windows, critical dimension (CD) and aerial image contrast is compared to investigate the effectiveness of the proposed contact holes patterning approach relative to conventional practice.