Mask innovations on the eve of High NA EUV lithography

Abstract We are on the eve of the next big step in lithography technology with the introduction of High numerical aperture EUV. The change from NA 0.33 to 0.55 in EUV lithography is an increase of 67%, which is the largest jump in the last decades, and puts tight requirements on focus and edge placement. Moreover, the lithography system has changed from fully isomorphic, i.e., same demagnification in all directions, to an anamorphic system, i.e., the demagnification in scan direction has doubled with respect to the slit direction. 
At imec we are fostering the ecosystem surrounding the lithography tool. In this paper we focus on the imaging and mask innovations supporting the EUV ecosystem, which are categorized into four areas: novel absorber masks, stitching, mask variability, and innovative imaging solutions. 
The current drivers of IC manufacturers implementing (High NA) EUVL are reduction of the EUV exposure dose and decrease in wafer stochastics. We discuss how these four areas have the potential to deliver in EUVL an increase in productivity, an improvement in the process window and a reduction in stochasticity at wafer level.