Patent ID: 7312019
Filing Date: 2007-12-25
Classification: G02B,G03F

Abstract:
1. A method of forming a linear grating with a stair-like structure by using in order a plurality of mask patterns for exposure to form resist patterns on a silicon substrate through photolithographic techniques, and etching the silicon substrate, said method comprising: selecting a mask pattern such that, when a shift in position of a resist pattern occurs due to a shift in exposure, an edge portion of the resist pattern at which a protrusion defect will occur on said silicon substrate is limited to an uppermost step of said stair-like structure, and the edge portion exists only on a predetermined side of the resist pattern; adjusting a position of the selected mask pattern and forming said resist pattern on said silicon substrate with the selected mask pattern such that the resist pattern completely covers a surface of the substrate at which said protrusion defect will occur; etching an entire surface of the resist pattern formed on said silicon substrate until a height of the resist pattern becomes the same height as the surface of the silicon substrate before processing, thereby leaving the resist pattern as a lower resist pattern; adjusting the position of the selected mask pattern and exposure dose, and forming an upper resist pattern such that an edge portion of the upper resist pattern at which a protrusion defect will occur is positioned on said lower resist pattern, and an opposite edge portion of the upper resist pattern is formed in a predetermined position; and, etching said silicon substrate while using said lower resist pattern and said upper resist pattern as a mask.