Patent ID: 8082524

Claim:
A computer-implemented method for determining mask patterns to be used on photo-masks in a multiple-exposure photolithographic process, comprising: receiving a target pattern; identifying, using the computer, a critical region in an initial mask pattern, wherein an initial photo-mask corresponding to the initial mask pattern is configured to print a wafer pattern, which corresponds to the target pattern, during a single-exposure photolithographic process, and wherein the critical region includes a location in the initial mask pattern that can be difficult to print in the wafer pattern during the single-exposure photolithographic process; and determining a first mask pattern and a second mask pattern based on the initial mask pattern and the target pattern, wherein the first mask pattern and the second mask pattern have at least one decreased spatial frequency relative to the initial mask pattern along at least one direction in the initial mask pattern; wherein the first mask pattern includes a first feature and the second mask pattern includes a second feature, and the first feature and the second feature overlap an intersection between features proximate to the critical region in the initial mask pattern; and wherein a first photo-mask corresponding to the first mask pattern and a second photo-mask corresponding to the second mask pattern are to print another wafer pattern, which corresponds to the target pattern, during the multiple-exposure photolithographic process.