Method of characterizing partial coherent light illumination and its application to serif mask design

摘要

A method and structure for serif mask design for correcting optical proximity effects in photolithography first characterizes a partial coherent light illumination from a photolithographic system and then utilizes the characterization results to perform serif mask design for the purpose of optical proximity corrections. The characterization of a partial coherent light illumination includes identifying an effective range of optical proximity effects for the photolithographic system, and focusing on slow-varying angle dependent terms in mutual intensity function, etc. The method and structure for serif mask design starts from ideal serif and hole design that work perfectly under a complete coherent illumination or under a complete incoherent illumination. For an outer corner, the initial design is a quarter-circle serif centered at the outer corner and located at the opposite quadrant of outer corner itself. The method then adjusts the size and shape of the serif until the image intensity at a point along the edge. For an inner corner, the initial design is a quarter-circle hole centered at the inner corner and located symmetrically inside the mask. The method then adjusts the size and shape of the serif until the aerial image intensity at the outer corner equals the aerial image intensity at a point along the edge.