| 摘要 |
PURPOSE:To manufacture a primary lambda/4 shift type diffraction grating having different depth values of the diffraction grating on both the sides of a shifted position with high reproducibility by selectively forming a film having a prescribed transmissivity on the upper part of a photoresist and then executing interference exposure. CONSTITUTION:After selectively forming the film 22 having the prescribed transmissivity on the upper part of the photoresist 21, interference exposure is executed by means of a phase conjugate mirror. Namely, the photoresist 21 on an area 23 forming no film 22 is more exposed than that of an area 24 formed under the film 22 having the prescribed transmissivity. Thereby, an overexposure state and proper exposure time can be respectively set up in the areas 23, 24 by properly controlling the thickness of the film 22 and the exposure time. The depth of the diffraction grating in the overexposure state is thinner than that of the proper exposure time. Consequently, the lambda/4 shift type diffraction grating having difference depth values on both the sides of a shifted position can be formed. |
