关键词: 相移掩模, 二次曝光, 铬残留, 相位角

Abstract: To reduce the number of chromium residue repairs in the fabrication of Phase Shift Masks (PSM) and achieve controllable phase angle adjustment, a repeated double exposure process is proposed. This study aims to evaluate the impact of the improved process on the deviation of critical dimension mean to target (CD MTT) and uniformity (CDU), as well as further analyze the effects of phase angle adjustment and chromium residue count control. Experimental results show that after two rounds of double exposure, the maximum variation in CD MTT of the PSM substrate is only 0.8 nm, with minimal change in CDU, indicating that the process maintains high precision while ensuring stability. Additionally, the phase angle can be adjusted within a range of approximately 1°, providing a new approach for further optimization of the lithography process. The study demonstrates that the repeated double exposure process offers advantages in phase angle adjustment and significantly reduces the number of chromium residue defects, showcasing its broad potential for application in PSM manufacturing.

Key words: phase shift mask, double exposure process, chromium residue, phase angle