Patent ID: 8138002

Claim:
A convex part formation method of forming a convex part, which extends in parallel with a <110> direction of a backing, on the backing having a {100} face as the top surface thereof, comprising the steps of: (a) forming a mask layer, which extends in parallel with the <110> direction, on the backing; (b) etching the backing according to a wet etching method, which employs an etching solution, using the mask layer as an etching mask so as to form a convex-part upper layer whose sectional shape on a cutting plane corresponding to a {110} face is an isosceles trapezoid, the base of which is longer than the upper side thereof, and the side surface of which has an inclination of θ U ; and (c) further etching the backing according to the wet etching method at a different temperature of the etching solution and using the mask layer and the side surface of the convex-part upper layer as an etching mask so as to form a convex-part lower layer whose sectional shape on the cutting plane corresponding to the {110} face is an isosceles trapezoid, the base of which is longer than the upper side thereof, and the side surface of which has an inclination of θ D (where θ D ≠θ U ), wherein: the base of the sectional shape of the convex part upper layer cut on the {110} face corresponds to the upper side of the sectional shape of the convex-part lower layer cut on the {110} face; and assuming that θ 111B denotes the inclination of the flank of the convex part which is a (111) B face, θ U ≦θ 111B ≦θ D (where θ D ≠θ U ) is satisfied, wherein the temperature of the etching solution employed at the step (b) is lower than the temperature of the etching solution employed at the step (c).