Semiconductor device and method for fabricating the same

Abstract

A semiconductor device includes a substrate and a semiconductor layer formed on the substrate. The substrate has: a flat region provided in a main surface thereof; a first indentation region provided in a portion of the main surface different from the flat region and formed with first recesses; and a second indentation region provided between the first indentation region and the flat region, formed with second recesses, and having a lower probability of occurrence of growth nuclei than the first indentation region and a higher probability than the flat region in the case where a crystal of a semiconductor is grown on the main surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a substrate used in a semiconductor device according to a first embodiment of the present invention. FIG. 1A is a plan view thereof, and FIG. 1B is a sectional view thereof taken along the line Ib-Ib in FIG. 1A.

FIG. 2 is a graph showing the relation between the period of recesses formed in the substrate and abnormal growth of a semiconductor layer in the semiconductor device according to the first embodiment of the present invention.

FIG. 3 is a plan view showing another example of the substrate used in the semiconductor device according to the first embodiment of the present invention.

FIG. 4 is a plan view showing another example of the substrate used in the semiconductor device according to the first embodiment of the present invention.

FIG. 5 is a plan view showing another example of the substrate used in the semiconductor device according to the first embodiment of the present invention.

FIGS. 6A and 6B illustrate a substrate used in a semiconductor device according to one modification of the first embodiment of the present invention. FIG. 6A is a plan view thereof, and FIG. 6B is a sectional view thereof taken along the line VIb-VIb in FIG. 6A.

FIG. 7 is a sectional view showing another example of the substrate used in the semiconductor device according to one modification of the first embodiment of the present invention.

FIG. 8 is a sectional view showing a semiconductor device according to a second embodiment of the present invention.

FIG. 9 is a sectional view showing a semiconductor device according to a third embodiment of the present invention.

FIGS. 10A to 10D are sectional views showing a method for fabricating a semiconductor device according to the third embodiment of the present invention.

FIG. 11 is a sectional view showing the structure of a semiconductor layer formed on a conventional substrate, which is used to explain a challenge of the present invention.

Claims

1. A semiconductor device comprising: a substrate including a first indentation region and a second indentation region, the first indentation region being provided in a main surface thereof and formed with first recesses or protrusions, the second indentation region being provided to adjoin the first indentation region, formed with second recesses or protrusions, and having a lower probability of occurrence of growth nuclei than the first indentation region in the case where a crystal of a semiconductor is grown on the main surface; anda semiconductor layer formed on the substrate.

2. The device of claim 1, wherein the substrate includes a flat region which is provided in a portion of the main surface located on the side of the second indentation region opposite from the first indentation region, andin the substrate, the second indentation region has a higher probability of occurrence of growth nuclei than the flat region.

3. The device of claim 1, wherein the density of the second recesses or protrusions in the second indentation region is lower than the density of the first recesses or protrusions in the first indentation region.

4. The device of claim 3, wherein in the second indentation region, the density of the second recesses or protrusions is higher in an area located on the side thereof in contact with the first indentation region than in an area located on the opposite side from that area.

5. The device of claim 1, wherein the first recesses or protrusions are arranged in a lattice pattern, andthe second recesses or protrusions are arranged in a lattice pattern having a longer arrangement period than the lattice pattern with the first recesses or protrusions arranged therein.

6. The device of claim 1, wherein the first recesses or protrusions are arranged in a lattice pattern, andthe second recesses or protrusions are arranged at lattice points of a lattice pattern other than randomly-selected ones, respectively, the lattice pattern having the same period as the lattice pattern with the first recesses or protrusions arranged therein.

7. The device of claim 1, wherein the diameters of the second recesses or protrusions are smaller than the diameters of the first recesses or protrusions.

8. The device of claim 7, wherein the diameters of the second recesses or protrusions are larger in an area of the second indentation region located on the side thereof in contact with the first indentation region than in an area located on the opposite side from that area.

9. The device of claim 1, wherein the first recesses or protrusions are first recesses,the second recesses or protrusions are second recesses, andthe depths of the second recesses are equal to or smaller than the depths of the first recesses, and in the second indentation region, the depths of the second recesses are smaller in an area located on the side thereof in contact with the first indentation region than in an area located on the opposite side from that area.

10. The device of claim 9, wherein the second recesses have tapered shapes in which the upper diameters are larger than the bottom diameters, respectively.

11. The device of claim 1, wherein the first recesses or protrusions are first protrusions,the second recesses or protrusions are second protrusions, andthe heights of the second protrusions are equal to or smaller than the heights of the first protrusions, and in the second indentation region, the heights of the second protrusions are smaller in an area located on the side thereof in contact with the first indentation region than in an area located on the opposite side from that area.

12. The device of claim 11, wherein the second protrusions have tapered shapes in which the upper diameters are smaller than the bottom diameters, respectively.

13. A method for fabricating a semiconductor device, comprising: the step (a) of forming a substrate which includes a flat region provided in a main surface thereof, a first indentation region provided in a portion of the main surface different from the flat region and having first recesses or protrusions, and a second indentation region provided between the first indentation region and the flat region, formed with second recesses or protrusions, and having a lower probability of occurrence of growth nuclei than the first indentation region and a higher probability than the flat region in the case where a crystal of a semiconductor is grown on the main surface; andthe step (b) of growing a crystal of a semiconductor layer on the substrate.

14. The method of claim 13, wherein the step (a) is the step of etching the first indentation region and the second indentation region using different masks to form the first recesses or protrusions and the second recesses or protrusions, respectively, andthe first recesses or protrusions and the second recesses or protrusions are formed so that the density of the second recesses or protrusions in the second indentation region is lower than the density of the first recesses or protrusions in the first indentation region.

15. The method of claim 13, wherein the step (a) is the step of etching the first indentation region and the second indentation region using different masks to form first recesses and second recesses, respectively, andthe second recesses are formed so that the depths of the second recesses are equal to or smaller than the depths of the first recesses and that in the second indentation region, the depths of the second recesses are smaller in an area located on the side thereof in contact with the first indentation region than in an area located on the side thereof in contact with the flat region.

16. The method of claim 13, wherein the step (a) is the step of etching the first indentation region and the second indentation region using different masks to form first protrusions and second protrusions, respectively, andthe second protrusions are formed so that the heights of the second protrusions are equal to or smaller than the heights of the first protrusions and that in the second indentation region, the heights of the second protrusions are smaller in an area located on the side thereof in contact with the first indentation region than in an area located on the side thereof in contact with the flat region.

17. The method of claim 13, further comprising, after the step (b), the step of removing the substrate.

18. The method of claim 13, further comprising, after the step (b), the step of removing the flat region in the substrate.