Multiple-field-point pupil wavefront optimization in computational lithography.

Some pupil wavefront optimization (PWO) approaches were studied to compensate the thick mask effects considering only a field point, and these PWO methods neglect the inherent wave aberration in a realistic lithography system. Particularly, the wave aberration of lithography projection optics is exposure field dependent, and the wave aberrations at different fields of view (FOVs) would seriously and unevenly impact the results and effects of PWO. The current PWO method for single FOV cannot match full FOV. In this paper, we propose a multiple-field-point PWO (MPWO) method to improve lithography imaging quality for full FOV. A multiple-field-point cost function is built including the uneven impact of multiple aberrations on lithography imaging at full FOV. The comprehensive simulations demonstrate that the proposed MPWO method can effectively improve consistency of lithography imaging and enlarge the overlapped process window for full FOV. The most important point is that the optimized wavefront attained by MPWO can be realized via pupil wavefront manipulator FlexWave in lithography equipment, which is significant in holistic lithography for the next technology node.