Enablement of 0.55NA EUV bright field mask stitching

The new high numerical aperture (0.55NA) Extreme Ultraviolet Lithography (EUVL) machine is using an anamorphic projection system, with the demagnification of 4× in x-direction and 8× in y-direction. Due to this 8× demagnification in y-direction and the unchanged six-inch reticle size, 0.55NA EUVL reduces the exposure field size to half-field (26 × 16.5mm²). Therefore, the in-die stitching between two exposures might be needed for the applications requiring larger than half-field size. In this paper, we will investigate the feasibility of in-die stitching by using bright field masks (both low-n attenuated phase shift mask and Ta-based mask are considered). The impact of decomposition rules, sub-resolution gratings as well as the mask quality on stitching patterning fidelity will be discussed and evaluated.