Abstract: The influence of edge taper angle and edge roughness on transferred wafer image was investigated by computer simulation for sub-half-micron space and hole patterns on the wafer. The exposure latitude for a 0.3- $mu@m space pattern on the wafer is almost unchanged for angles exceeding 60 degrees. The exposure latitude for 0.3-, 0.35-, and 0.4- $mu@m hole patterns remains almost unchanged unless the edge roughness exceeds 0.04 $mu@m. However, when shifter thickness on the pattern edge decreases 50%, a particularly bad case, and edge roughness of 0.01 $mu@m results in 25% degradation of exposure latitude. Taking simulation results into consideration, we optimized the mask manufacturing process using wet etching for CrO-based phase shifters and obtained an edge roughness of approximately 0.01 $mu@m and an edge taper angle greater than 60 degrees. Experiment showed that wet-etched mask performance is equivalent to that of the dry-etched mask.!3
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