Gradient-based inverse extreme ultraviolet lithography

Abstract

Extreme ultraviolet (EUV) lithography is the most promising successor of current deep ultraviolet (DUV) lithography. The very short wavelength, reflective optics, and nontelecentric structure of EUV lithography systems bring in different imaging phenomena into the lithographic image synthesis problem. This paper develops a gradient-based inverse algorithm for EUV lithography systems to effectively improve the image fidelity by comprehensively compensating the optical proximity effect, flare, photoresist, and mask shadowing effects. A block-based method is applied to iteratively optimize the main features and subresolution assist features (SRAFs) of mask patterns, while simultaneously preserving the mask manufacturability. The mask shadowing effect may be compensated by a retargeting method based on a calibrated shadowing model. Illustrative simulations at 22 and 16 nm technology nodes are presented to validate the effectiveness of the proposed methods.

Thick-mask model based on multi-channel U-Net for EUV lithography

“…The components of EUV lithography system include the illumination system, reflective mask, reflective projection optics system and wafer platform. However, the very short wavelength of EUV light, the high aspect ratio of mask absorber layer, fully reflective optics and off-axis illumination used in EUV lithography system produce pronounced mask three-dimensional (M3D) effects [1]. The M3D effects include focusdependent pattern shift, deviation of phase-shift value and critical dimension (CD) difference [2]- [3].…”