Effects of mask absorber thickness on printability in EUV lithography with high resolution resist

Abstract:
The effects of mask absorber thickness on printability in EUV lithography was studied from the viewpoint of lithographic requirements which can give high imaging contrast and reduce shadowing effect. From lithography simulation, optimum thickness range of mask absorber (LR-TaBN) for exposure latitude was predicted, and the effect of absorber thickness on MEF and H-V (Horizontal - Vertical) printed CD difference was determined using resist blur model. From printability experiments with a Small Field Exposure Tool (SFET) and with high resolution resist, optimum thickness of LR-TaBN absorber was demonstrated. When thinner absorber mask is employed in EUVL for ULSI chip production, it becomes necessary to introduce EUV light shield area in order to suppress the leakage of EUV light from neighboring exposure shots. Resist pattern CD change from the neighboring exposure shots was estimated by lithography simulation.