Silicon carbide semiconductor device and method of manufacturing silicon carbide semiconductor device

1. A silicon carbide semiconductor device, comprising:

a silicon carbide semiconductor structure;

an insulated gate structure including

a gate insulating film, which is a silicon dioxide film, contacting the silicon carbide semiconductor structure, and

a gate electrode formed on the gate insulating film;

an interlayer insulating film covering the insulated gate structure;

a metal layer provided on the interlayer insulating film for absorbing or blocking hydrogen;

a main electrode provided on the metal layer and electrically connected to the silicon carbide semiconductor structure, and

an alloy film provided between the metal layer and the main electrode, the alloy film containing titanium and aluminum.

2. The silicon carbide semiconductor device according to claim 1 , wherein the metal layer is a titanium film.

3. The silicon carbide semiconductor device according to claim 1 , wherein the metal layer covers an entire top surface of the interlayer insulating film.

4. The silicon carbide semiconductor device according to claim 1 , wherein the interlayer insulating film covers the insulated gate structure and contacts the gate insulating film.

5. The silicon carbide semiconductor device according to claim 1 , wherein the main electrode is free of direct contact with the interlayer insulating film and the gate insulating film.

6. The silicon carbide semiconductor device according to claim 1 , wherein a thickness of the metal layer is 10 nm to 1.0 μm.

7. The silicon carbide semiconductor device according to claim 1 , wherein the metal layer has an absorbed hydrogen molecule concentration of 1×10 16 /cm 2 or higher.

8. The silicon carbide semiconductor device according to claim 1 , wherein

the metal layer is a first metal layer, and

the silicon carbide semiconductor device further includes a second metal layer provided between the first metal layer and the main electrode, the second metal layer being chemically stable with respect to the first metal layer.

9. The silicon carbide semiconductor device according to claim 1 , wherein a thickness of the alloy film is 10 nm to 50 nm.

10. The silicon carbide semiconductor device according to claim 1 , wherein

the main electrode is a first main electrode;

the silicon carbide semiconductor device further includes

a silicon carbide semiconductor substrate, and

an n-type drift layer and a second main electrode respectively provided on two opposite surfaces of the silicon carbide semiconductor substrate;

the silicon carbide semiconductor structure includes

a p-type semiconductor region selectively formed in the n-type drift layer, and

an n-type semiconductor region selectively provided in the p-type semiconductor region;

the gate insulating film covers a surface of a portion of the p-type semiconductor region between the n-type drift layer and the n-type semiconductor region; and

the first main electrode is electrically connected to the n-type semiconductor region.

11. The silicon carbide semiconductor device according to claim 6 , wherein the thickness of the metal layer is 80 nm to 150 nm.

12. The silicon carbide semiconductor device according to claim 8 , further comprising

a third metal layer, provided between the second metal layer and the main electrode, for absorbing or blocking the hydrogen.

13. The silicon carbide semiconductor device according to claim 12 , wherein the third metal layer is a titanium film.

14. The silicon carbide semiconductor device according to claim 12 , further comprising

an alloy film provided between the third metal layer and the main electrode, the alloy film containing titanium and aluminum.

15. The silicon carbide semiconductor device according to claim 10 , wherein the silicon carbide semiconductor substrate is of an n-type and has an impurity concentration that is higher than that of the n-type drift layer.

16. A silicon carbide semiconductor device comprising:

a silicon carbide semiconductor structure;

an insulated gate structure including

a gate insulating film, which is a silicon dioxide film, contacting the silicon carbide semiconductor structure, and

a gate electrode formed on the gate insulating film;

an interlayer insulating film covering the insulated gate structure;

a metal layer provided on the interlayer insulating film for absorbing or blocking hydrogen; and

a main electrode provided on the metal layer and electrically connected to the silicon carbide semiconductor structure, wherein

the metal layer is a first metal layer, and

the silicon carbide semiconductor device further includes a second metal layer provided between the first metal layer and the main electrode, the second metal layer being a titanium nitride film and being chemically stable with respect to the first metal layer.

17. A method of manufacturing a silicon carbide semiconductor device, comprising:

providing a silicon carbide semiconductor base having a silicon carbide semiconductor structure formed thereon;

forming an insulated gate structure, including

thermally oxidizing the silicon carbide semiconductor structure to form a silicon dioxide film on a surface thereof, and

forming a gate electrode on the silicon dioxide film;

forming an interlayer insulating film covering the insulated gate structure;

forming a titanium film on the interlayer insulating film;

forming an alloy film on the titanium film, the alloy film containing titanium and aluminum; and

forming on the alloy film a main electrode that is electrically connected to the silicon carbide semiconductor structure.

18. The method of manufacturing a silicon carbide semiconductor device according to claim 17 , comprising performing heat treating at a temperature of 450 degrees C. or less after forming the main electrode.