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.
In optical maskless lithography in concern, a digital micromirror device plays the role of a digital mask. Due to the spatial/temporal configuration of micromirror arrays/response or the specification of illumination/projection optics, the irradiance may be influenced by diffraction effects. In present study, an investigation of various optical maskless lithography models based on binary micromirror reflections is performed in consideration of the diffraction effect. To evaluate lithographic parameters dissolved in the lithography models, parametric studies are performed focusing on pattern fidelity and line edge roughness. To reduce corner rounding phenomena due to an image size and further to a reflection criterion, the auxiliary corner reflection adjusting feature (ACRAF) analogous to conventional serif are employed and the effectiveness of ACRAFs is analyzed. The potential of utilizing the adjusted parameters for enhancing pattern fidelity and line edge roughness under diffraction effects is demonstrated through simulations and experiments.
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