| 摘要 |
PROBLEM TO BE SOLVED: To realize an etching process which is capable of improving reliability in a protective film or a metal film. SOLUTION: A photoresist film 40 is applied onto a GaN layer 30 and subjected to proximity exposure. The parts A-B and E-F of the photoresist film 40 are completely exposed to light, but the part C-D is not at all exposed to light. The parts B-C and D-E are gradually decreased in exposure from a point B or E to a point C or D, due to a light diffraction phenomenon. As a result, the exposed part of the photoresist film 40 is represented by a region shaded with oblique lines, and the photoresist film 40 can be formed with peripheral part to be thinner as the edge is approached, in a taper when it is developed. The GaN layer 30 is dry-etched using a mask 42. The etched side wall of the GaN layer 30 is inclined at an angle smaller than 90 deg.. As a result, a protective film of SiO2 or the like can be continuously formed uniformly in thickness on a non-etched surface, a side wall surface and an etched surface. |
