Semiconductor light-emitting element, fabrication method thereof, convex part formed on backing, and convex part formation method for backing

1. 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).

2. A convex part formation method comprising:

a step of forming a convex-part upper layer of a semiconductor material by applying an etching solution to a principal surface of the semiconductor material, a cross-section of said convex-part upper layer being an isosceles trapezoid, and thereafter;

a step of forming a convex-part lower layer of the semiconductor material by applying said etching solution to a different portion of the semiconductor material and to a side surface of the convex-part upper layer, a cross-section of said convex-part lower layer being a different isosceles trapezoid,

wherein a temperature of the etching solution is higher during the step of forming the convex-part upper layer than during the step of forming the convex-part lower layer.

3. The convex part formation method according to claim 2 , wherein said semiconductor material is an element fabrication substrate.

4. The convex part formation method according to claim 2 , wherein said cross-section of said convex-part upper layer is a sectional shape of the convex-part upper layer on a cutting plane corresponding to a {110} face of the semiconductor material.

5. The convex part formation method according to claim 2 , wherein said cross-section of said convex-part lower layer is a sectional shape of the convex-part upper layer on a cutting plane corresponding to a {110} face of the semiconductor material.

6. The convex part formation method according to claim 2 , wherein said etching solution is citric acid/hydrogen peroxide water.

7. The convex part formation method according to claim 2 , wherein said etching solution contains citric acid, pure water, and hydrogen peroxide water at a volume ratio of 3:2:2.

8. The convex part formation method according to claim 2 , wherein:

H U /(H U +H D )≧0.5, with

“H U ” being the thickness of said convex-part upper layer,

“H D ” being the thickness of said convex-part lower layer.

9. The convex part formation method according to claim 2 , wherein:

(H U +H D )/W U ≧0.4, with

“W U ” being the width of said convex-part upper layer,

“H U ” being the thickness of said convex-part upper layer,

“H D ” being the thickness of said convex-part lower layer.

10. The convex part formation method according to claim 2 , wherein a mask layer is formed on said principal surface, said mask layer being an etching mask during the step of forming the convex-part upper layer and during the step of forming the convex-part lower layer.

11. The convex part formation method according to claim 10 , wherein said principal surface is a {100} face of the semiconductor material, said mask layer being in parallel with the <110> direction of said semiconductor material.

12. The convex part formation method according to claim 2 , wherein:

θ U ≦θ D , with

“θ U ” being an inclination of said side surface of the convex-part upper layer,

“θ D ” being an inclination of a surface of the convex-part lower layer.

13. The convex part formation method according to claim 12 , wherein:

θ U ≦θ 111B ≦θ D , with

“θ 111B ” being the inclination of the flank of a convex part corresponding to a {111}B face of the semiconductor material.

14. The convex part formation method according to claim 12 , wherein said etching solution applied to said principal surface exposes said different portion of the semiconductor material and said side surface of the convex-part upper layer.

15. The convex part formation method according to claim 12 , wherein said etching solution applied to said different portion of the semiconductor material and to said side surface of the convex-part upper layer exposes another portion of the semiconductor material and said side surface of the convex-part lower layer.

16. The convex part formation method according to claim 12 , wherein a base of the different isosceles trapezoid is longer than an upper side of the different isosceles trapezoid, said upper side of the different isosceles trapezoid being a base of the isosceles trapezoid.

17. The convex part formation method according to claim 16 , wherein said base of the isosceles trapezoid is longer than an upper side of the isosceles trapezoid, said upper side of the isosceles trapezoid being a portion of the principal surface.