Semiconductor device and fabrication method of the same

Abstract

A fabrication method of a semiconductor device includes forming a silicon nitride layer on a compound semiconductor layer with a plasma CVD method and selectively treating the compound semiconductor layer with use of the silicon nitride layer for a mask. The silicon nitride layer has a refraction index of less than 1.85. The compound semiconductor layer includes Ga.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described in detail with reference to the following drawings, wherein:

FIG. 1 illustrates a perspective view of a semiconductor laser in accordance with a first embodiment;

FIG. 2A and FIG. 2B illustrate a cross sectional view of the semiconductor device in accordance with the first embodiment;

FIG. 3A through FIG. 3D illustrate a fabrication process of the semiconductor device in accordance with the first embodiment;

FIG. 4A through FIG. 4D illustrate a fabrication process of the semiconductor device in accordance with the first embodiment;

FIG. 5A through FIG. 5C illustrate a fabrication process of the semiconductor device in accordance with the first embodiment; and

FIG. 6 illustrates a relationship between a refraction index of a silicon nitride layer and an element resistance of the semiconductor device in accordance with the first embodiment.

Claims

1. A fabrication method of a semiconductor device comprising: forming a silicon nitride layer on a compound semiconductor layer with a plasma CVD method,the silicon nitride layer having a refraction index of less than 1.85,the compound semiconductor layer including Ga; andselectively treating the compound semiconductor layer with use of the silicon nitride layer for a mask.

2. The method as claimed in claim 1, wherein the step of selectively treating is an etching process.

3. The method as claimed in claim 1, wherein the step of selectively treating is a process where an impurity is doped into the compound semiconductor layer.

4. The method as claimed in claim 1, wherein the step of selectively treating is a process where a ridge of a semiconductor luminescent device is formed by etching a part of the compound semiconductor layer exposed in an area except for the mask area.

5. The method as claimed in claim 4 further comprising eliminating at least a part of the mask on the ridge and forming a contact electrode.

6. The method as claimed in claim 1, wherein the silicon nitride layer is formed in a condition where a flow ratio of SiH4, NH3 and N2 is 3 to 10:5 to 10:1000 and an RF frequency is more than 2 MHz.

7. The method as claimed in claim 1, wherein the compound semiconductor layer including Ga is one of GaN, AlGaN, GaAs, AlGaInP and InGaP.

8. A fabrication method of a semiconductor device comprising: forming a silicon nitride layer on a compound semiconductor layer with a plasma CVD method,the silicon nitride layer having a refraction index of less than 1.85,the compound semiconductor layer including Ga; andforming a protective layer denser than the silicon nitride layer on the silicon nitride layer.

9. The method as claimed in claim 8, wherein a refraction index of the protective layer is more than 2.0.

10. The method as claimed in claim 8 further comprising forming a ridge of a semiconductor luminescent device by etching a part of the compound semiconductor layer exposed in an area except for a mask area, the mask being composed of the silicon nitride layer only or being composed of laminating of the silicon nitride layer and the protective layer.

11. The method as claimed in claim 10 further comprising eliminating at least a part of the mask on the ridge and forming a contact electrode.

12. The method as claimed in claim 8, wherein the silicon nitride layer is formed in a condition where a flow ratio of SiH4, NH3 and N2 is 3 to 10:5 to 10:1000 and an RF frequency is more than 2 MHz.

13. The method as claimed in claim 8, wherein the compound semiconductor layer including Ga is one of GaN, AlGaN, GaAs, AlGaInP and InGaP.

14. A semiconductor device comprising: a compound semiconductor layer that includes Ga and that is provided on a substrate;a silicon nitride layer that is provided on the compound semiconductor layer and that has a refraction index of less than 1.85;a protective layer that is provided on the silicon nitride layer and that is denser than the silicon nitride layer.

15. The semiconductor device as claimed in claim 14 wherein the protective layer has a refraction index of more than 2.0.

16. The semiconductor device as claimed in claim 14 wherein the compound semiconductor layer including Ga is one of GaN, AlGaN, GaAs, AlGaInP and InGaP.

17. The semiconductor device as claimed in claim 14 further comprising a ridge of a semiconductor luminescent device that is formed by etching a part of the compound semiconductor except for a mask area, the mask being composed of the silicon nitride layer or being composed of laminating of the silicon nitride layer and the protective layer.

18. The semiconductor device as claimed in claim 17 further comprising a contact electrode formed after elimination of at least a part of the mask on the ridge.