The influence of reflectivity on EUV lithography performance of low-n and binary masks for random logic via implementation

Novel mask absorber materials have been explored to improve EUV imaging performance which includes a variation of film thickness, refraction index n and the extinction coefficient k. A few promising mask absorber candidates were fabricated and evaluated using imec patterning on random logic via design with minimum pitch of 36nm. This study compares the lithography performance of low-n EUV masks with different reflectivity to our Ta-based EUV mask reference. The masks are designed with resolution enhancement techniques (RET) including source-mask optimization (SMO), optical proximity correction (OPC) and sub-resolution assist feature (SRAF) to achieve optimum mask to imaging performance. This work discusses the random logic via patterning benefits and limitations using different low-n EUV masks, along with the potential to extend the resolution of NA0.33 EUV lithography to random logic via designs down to 32nm pitch.