Silicon carbide semiconductor device and method for producing same

1 . A silicon carbide semiconductor device comprising:

an active portion; and

a breakdown voltage structure portion provided surrounding a periphery of the active portion in plan view, wherein

a first conductivity-type drift layer containing silicon carbide is provided over the active portion and the breakdown voltage structure portion,

the active portion has:

a second conductivity-type base region containing silicon carbide provided on an upper surface side of the drift layer;

a first conductivity-type main region containing silicon carbide provided on an upper surface side of the base region;

a second conductivity-type buried region containing silicon carbide provided in contact with the base region on the upper surface side of the drift layer;

a second conductivity-type base contact region containing silicon carbide provided in contact with the main region on an upper surface side of the buried region;

a gate electrode provided with a gate insulating film interposed inside a trench passing through the main region and the base region; and

a main electrode provided in contact with the main region and the base contact region,

the breakdown voltage structure portion has:

a second conductivity-type electric field relaxation region containing silicon carbide provided on the upper surface side of the drift layer; and

an insulating film provided on an upper surface of the electric field relaxation region,

the main region and the base contact region each contain a 3C-structure in at least a part in contact with the main electrode, and

the electric field relaxation region is composed of a 4H-structure.

2 . The silicon carbide semiconductor device according to claim 1 , wherein the buried region contains a 4H-structure.

3 . The silicon carbide semiconductor device according to claim 1 , wherein at least a part in contact with the main electrode of each of the main region and the base contact region contains an inert gas element.

4 . The silicon carbide semiconductor device according to claim 3 , wherein the inert gas element is helium or argon.

5 . The silicon carbide semiconductor device according to claim 1 , wherein a plurality of the electric field relaxation regions is a plurality of guard rings provided in the breakdown voltage structure portion.

6 . The silicon carbide semiconductor device according to claim 1 , comprising:

a second conductivity-type ring region containing silicon carbide provided surrounding the active portion on the upper surface side of the drift layer between the active portion and the breakdown voltage structure portion in plan view, wherein

the ring region has an upper surface in contact with the main electrode and contains a 3C-structure in at least a part in contact the main electrode.

7 . The silicon carbide semiconductor device according to claim 1 , wherein a dimension in a depth direction of each of the main region and the base contact region is 0.5 μm or less.

8 . The silicon carbide semiconductor device according to claim 1 , wherein each of the main region and the base contact region contains a 3C-structure and a 4H-structure.

9 . The silicon carbide semiconductor device according to claim 8 , wherein a proportion of the 3C-structure contained in a part from an upper surface to a depth of 0.3 μm of each of the main region and the base contact region is in a range of 50% or more and 100% or less.

10 . The silicon carbide semiconductor device according to claim 1 , wherein each of the main region and the base contact region has an impurity concentration in a range of 1×10 19 cm −3 or more and 3×10 21 cm −3 or less.

11 . The silicon carbide semiconductor device according to claim 1 , wherein the electric field relaxation region has an impurity concentration of 2×10 18 cm −3 or more in a part in contact with the insulating film.

12 . A method for producing a silicon carbide semiconductor device comprising:

forming a first conductivity-type drift layer containing silicon carbide over an active portion and a breakdown voltage structure portion surrounding a periphery of the active portion in plan view;

forming a second conductivity-type base region containing silicon carbide on an upper surface side of the drift layer in the active portion;

forming a first conductivity-type main region on an upper surface side of the base region, the main region containing silicon carbide and containing a 3C-structure in at least an upper surface side part;

forming a second conductivity-type buried region containing silicon carbide to be in contact with the base region on the upper surface side of the drift layer;

forming a second conductivity-type base contact region to be in contact with the main region on an upper surface side of the buried region, the base contact region containing silicon carbide and containing a 3C-structure in at least an upper surface side part;

forming a trench passing through the main region and the base region;

forming a gate electrode with a gate insulating film interposed inside the trench;

forming a main electrode to be in contact with upper surfaces of the main region and the base contact region;

forming a second conductivity-type electric field relaxation region composed of 4H-structure silicon carbide on the upper surface side of the drift layer in the breakdown voltage structure portion; and

forming an insulating film on an upper surface of the electric field relaxation region.

13 . The method for producing a silicon carbide semiconductor device according to claim 12 , wherein

the forming the main region includes ion-implanting a first conductivity-type impurity with a dose amount of 2×10 15 cm −2 or more,

the forming the base contact region includes ion-implanting a second conductivity-type impurity with a dose amount of 2×10 15 cm −2 or more, and

the forming the electric field relaxation region includes ion-implanting a second conductivity-type impurity with a dose amount less than 2×10 15 cm −2 .

14 . The method for producing a silicon carbide semiconductor device according to claim 12 ,

the forming the main region including ion-implanting a first conductivity-type impurity with a dose amount less than 2×10 15 cm −2 , and

the forming the base contact region and the forming the electric field relaxation region including simultaneously ion-implanting a second conductivity-type impurity with a dose amount less than 2×10 15 cm −2 ,

the method further comprising:

ion-implanting an inert gas element with a dose amount of 2×10 15 cm −2 or more in total with the dose amount of the first conductivity-type impurity or with the dose amount of the second conductivity-type impurity into the main region and the base contact region.

15 . The method for producing a silicon carbide semiconductor device according to claim 14 , wherein the inert gas element is helium or argon.

16 . The method for producing a silicon carbide semiconductor device according to claim 12 , wherein the first conductivity-type impurity is phosphorus or nitrogen.

17 . The method for producing a silicon carbide semiconductor device according to claim 12 , wherein the second conductivity-type impurity is aluminum.