| 摘要 |
PURPOSE:To obtain a simple diffraction grating having excellent mass productivity by removing a sepn. film on one photoresist film subjected to two-beam interference exposure of two kinds of the photoresists which are reversed in photosensitive characteristic from each other via the sepn. film then removing the layer deteriorated in property on the surface. CONSTITUTION:After the positive type photoresist 2 (P film) is coated on a substrate 1, said film is made to remain only in the region A and an SiN film 3 is formed over the entire surface; furthermore, the negative type photoresist film 4 (N film) is coated over the entire surface. The P film 2 can be simultaneously exposed if the entire surface of the substrate 1 is subjected to the uniform two-beam interference exposure. The developing time of the N film 4 is adjusted to form the diffraction grating of the N film 4 in the region B an to hold the SiN film 3 exposed in the region A; thereafter the SiN film 3 is etched by a buffer hydrofluoric acid. The P film 2 is exposed in the region A and the surface is etched by oxygen plasma to remove the layer deteriorated in property. Chemical etching is executed with the diffraction grating obtd. by developing the P film of the region A and the diffraction grating by the sepn. film 3 of the region B respectively as masks, by which the diffraction grating having the ruggedness inverted in phases at the center and the good shape of the ruggedness is formed to the substrate 1. |
