Adjustment of image decomposition mode and reflection criterion focusing on critical dimension uniformity and exposure dose effectiveness under diffraction effects in optical microlithography using a digital micromirror device

摘要

In the optical microlithography in concern, a digital micromirror device plays the role of a digital mask, and the diffraction effect due to reflections off of a square micromirror may not be negligible. The projected beam image may not be a typical uniform square or pointed circular beam. Therefore, existing image decomposition modes and reflection criteria developed for a typical beam may not be appropriate for lithography under the diffraction effect. In this study, to improve the critical dimension uniformity and the exposure dose effectiveness, a novel image decomposition mode based on the proxy delta configuration is proposed. A successive set of proxy delta parameters which produce a honeycomb decomposed structure is utilized to implement a proxy delta lithography system that allows the usage of a typical square image array without the hassle of projecting a square mirror array into a rectangular image array using an aspheric micro lens array. A reflection criterion employing intensity weighted occupancy patterns that account for the diffracted beam profile is utilized to adjust the binary reflections. The potential for a honeycomb decomposition mode based on the proposed proxy delta configuration to improve the critical dimension uniformity and the exposure dose effectiveness is demonstrated.