| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing the surface form of a diffraction grating having high diffraction efficiency although the grating is a multilevel binary type one. SOLUTION: In the manufacture of the surface form of a diffraction grating by etching a substrate a plurality of times, when the edge of the region reserved in the preceding step is to be processed in the succeeding step, the mask in the succeeding step is set in the position shifted from the position where the edge of the opening of the mask coincides with the edge of the reserved region in the preceding step to the direction where the region to be processed in the succeeding step overlaps the region processed in the preceding step. The slope produced in a part along the reserved region in the processed region in the preceding step is removed by the process of the succeeding step, which prevents the formation of projections by adjacent slopes in opposite directions. This results in improvement in the diffraction efficiency.
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