Evaluation of multilayer defect repair viability and protection techniques for EUV masks

摘要

A variety of repairs on EUV multilayer were conducted including protection against pattern degradation in manufactural use in order to evaluate feasibility of multilayer repair and the protection schemes. The efficacy of post-repair protection techniques are evaluated to determine the lifetime of multilayer repairs. Simulations were used to select the optimal material thicknesses for repair protection, and the simulation results are verified with the lithographic results. The results showed a high correlation coefficient. Finally, all repaired sites were cleaned multiple times to quantify repair durability and impact on wafer CD. Aerial imaging of the repair sites before and after cleans shows a dramatic degradation of wafer CD post-cleaning. However, we show that applying a surface protection material after multilayer repair successfully mitigates the influence of multilayer degradation during extensive manufacturing operations.