Method of manufacturing SiC semiconductor device having double oxide film formation to reduce film defects

Claim 1

A method of manufacturing a silicon carbide semiconductor device comprising the steps of: forming an epitaxial layer on a silicon carbide semiconductor substrate; forming a groove having a bottom surface and side surfaces on the surface of said epitaxial layer by means of dry etching; forming a first thermal oxidation film on said bottom surface and said side surfaces of said groove; removing said first thermal oxidation film by means of wet etching; and forming a second thermal oxidation film on said bottom surface and said side surfaces of said groove after said removal of said first thermal oxidation film; wherein the plane orientation of said semiconductor substrate composed of silicon carbide is one of a (0001) carbon face of a hexagonal system and a {111} carbon face of a cubic system, and wherein the plane orientation of said bottom surface of said groove in said step of forming a groove is substantially the same as that of said semiconductor substrate; and said second thermal oxidation film comprises a side surface oxidation film formed on said side surfaces of said groove and a bottom surface oxidation film having a thickness thicker than that of said side surface oxidation film and formed on said bottom surface of said groove.

Claim 2

A method of manufacturing a silicon carbide semiconductor device comprising the steps of: forming an epitaxial layer on a silicon carbide semiconductor substrate; forming a groove having a bottom surface and side surfaces on the surface of said epitaxial layer by means of dry etching; forming a first thermal oxidation film on said bottom surface and said side surfaces of said groove; removing said first thermal oxidation film by means of wet etching; and forming a second thermal oxidation film on said bottom surface and said side surfaces of said groove after said removal of said first thermal oxidation film; wherein the plane orientation of said semiconductor substrate composed of silicon carbide is one of a (0001) carbon face of a hexagonal system and a {111} carbon face of a cubic system, and wherein the plane orientation of said bottom surface of said groove in said step of forming a groove is substantially the same as that of said semiconductor substrate; and said second thermal oxidation film comprises a side surface oxidation film formed on said side surfaces of said groove and a bottom surface oxidation film having a thickness thicker than that of said side surface oxidation film and formed on said bottom surface of said groove.

Claim 6

A method of manufacturing a silicon carbide semiconductor device comprising the steps of: preparing a semiconductor substrate composed of single crystal silicon carbide which is constituted of a first resistance layer of a first conductivity type and having a first resistance and a second resistance layer of the first conductivity type, formed on said first resistance layer and having a second resistance less than said first resistance, and forming a semiconductor layer composed of silicon carbide of a second conductivity type on an upper surface of said semiconductor substrate; forming a semiconductor region of the first conductivity type in a region of said semiconductor layer; forming a groove to penetrate said semiconductor region and said semiconductor layer and to reach said second resistance layer of the first conductivity type; forming a first thermal oxidation film on inner surfaces of said groove; removing said first thermal oxidation film by means of etching; forming a second thermal oxidation film on said inner surfaces of said groove after said removing step; and forming a gate electrode layer on said second thermal oxidation film, a first electrode layer so as to contact both said semiconductor layer and said semiconductor region, and a second electrode layer on a lower surface of said semiconductor substrate to contact said first resistance layer; wherein the plane orientation of said upper surface of said semiconductor substrate composed of silicon carbide is one of a (0001) carbon face of a hexagonal system and a {111} carbon face of a cubic system, and wherein the plane orientation of said bottom surface of said groove in said step of forming a groove is substantially the same as that of said semiconductor substrate; and said second thermal oxidation film comprises a side surface oxidation film formed on said side surfaces of said groove and a bottom surface oxidation film having a thickness thicker than that of said side surface oxidation film an formed on said bottom surface of said groove.

Claim 7

A method of manufacturing a silicon carbide semiconductor device comprising the steps of: preparing a semiconductor substrate composed of single crystal silicon carbide which is constituted of a first resistance layer of a first conductivity type and having a first resistance and a second resistance layer of the first conductivity type, formed on said first resistance layer and having a second resistance less than said first resistance, and forming a semiconductor layer composed of silicon carbide of a second conductivity type on an upper surface of said semiconductor substrate; forming a semiconductor region of the first conductivity type in a region of said semiconductor layer; forming a groove to penetrate said semiconductor region and said semiconductor layer and to reach said second resistance layer of the first conductivity type; forming a first thermal oxidation film on inner surfaces of said groove; removing said first thermal oxidation film by means of etching; forming a second thermal oxidation film on said inner surfaces of said groove after said removing step; and forming a gate electrode layer on said second thermal oxidation film, a first electrode layer so as to contact both said semiconductor layer and said semiconductor region, and a second electrode layer on a lower surface of said semiconductor substrate to contact said first resistance layer; wherein the plane orientation of said upper surface of said semiconductor substrate composed of silicon carbide is one of a (0001) carbon face of a hexagonal system and a {111} carbon face of a cubic system, and wherein the plane orientation of said bottom surface of said groove in said step of forming a groove is substantially the same as that of said semiconductor substrate; and said second thermal oxidation film comprises a side surface oxidation film formed on said side surfaces of said groove and a bottom surface oxidation film having a thickness thicker than that of said side surface oxidation film an formed on said bottom surface of said groove.

Claim 8

The method of manufacturing a silicon carbide semiconductor device according to claims 5, wherein said step of forming a groove comprises the steps of: forming a local thermal oxidation film having a predetermined depth from the surface of said semiconductor layer in said groove forming region; and removing said local thermal oxidation film.

Claim 11

A method of manufacturing a silicon carbide semiconductor device comprising the steps of: forming an epitaxial layer on a silicon carbide semiconductor substrate; forming a groove having a bottom surface and side surfaces on the surface of said epitaxial layer by means of dry etching; forming a first thermal oxidation film on said bottom surface and said side surfaces of said groove; removing said first thermal oxidation film by means of wet etching; and forming a second thermal oxidation film on said bottom surface and said side surfaces of said groove after said removal of said first thermal oxidation film; wherein the plane orientation of said semiconductor substrate composed of silicon carbide is one of a substantially (0001) carbon face of a hexagonal system and a substantially {111} carbon face of a cubic system, and wherein the plane orientation of said bottom surface of said groove in said step of forming a groove is substantially the same as that of said semiconductor substrate; and said second thermal oxidation film comprises a side surface oxidation film formed on said side surfaces of said groove and a bottom surface oxidation film having a thickness thicker than that of said side surface oxidation film and formed on said bottom surface of said groove.

Claim 12

A method of manufacturing a silicon carbide semiconductor device comprising the steps of: forming an epitaxial layer on a silicon carbide semiconductor substrate; forming a groove having a bottom surface and side surfaces on the surface of said epitaxial layer by means of dry etching; forming a first thermal oxidation film on said bottom surface and said side surfaces of said groove; removing said first thermal oxidation film by means of wet etching; and forming a second thermal oxidation film on said bottom surface and said side surfaces of said groove after said removal of said first thermal oxidation film; wherein the plane orientation of said semiconductor substrate composed of silicon carbide is one of a substantially (0001) carbon face of a hexagonal system and a substantially {111} carbon face of a cubic system, and wherein the plane orientation of said bottom surface of said groove in said step of forming a groove is substantially the same as that of said semiconductor substrate; and said second thermal oxidation film comprises a side surface oxidation film formed on said side surfaces of said groove and a bottom surface oxidation film having a thickness thicker than that of said side surface oxidation film and formed on said bottom surface of said groove.

Claim 17

A method of manufacturing a silicon carbide semiconductor device comprising the steps of: preparing a semiconductor substrate composed of single crystal silicon carbide which is constituted of a first resistance layer of a first conductivity type and having a first resistance and a second resistance layer of the first conductivity type, formed on said first resistance layer and having a second resistance less than said first resistance, and forming a semiconductor layer composed of silicon carbide of a second conductivity type on an upper surface of said semiconductor substrate; forming a semiconductor region of the first conductivity type in a region of said semiconductor layer; forming a groove to penetrate said semiconductor region and said semiconductor layer and to reach said second resistance layer of the first conductivity type; forming a first thermal oxidation film on inner surfaces of said groove; removing said first thermal oxidation film by means of etching; forming a second thermal oxidation film on said inner surfaces of said groove after said removing step; and forming a gate electrode layer on said second thermal oxidation film, a first electrode layer so as to contact both said semiconductor layer and said semiconductor region, and a second electrode layer on a lower surface of said semiconductor substrate to contact said first resistance layer; wherein the plane orientation of said upper surface of said semiconductor substrate composed of silicon carbide is one of a substantially (0001) carbon face of a hexagonal system and a substantially {111} carbon face of a cubic system, and wherein the plane orientation of said bottom surface of said groove in said step of forming a groove is substantially the same as that of said semiconductor substrate; and said second thermal oxidation film comprises a side surface oxidation film formed on said side surfaces of said groove and a bottom surface oxidation film having a thickness thicker than that of said side surface oxidation film an formed on said bottom surface of said groove.

Claim 18

A method of manufacturing a silicon carbide semiconductor device comprising the steps of: preparing a semiconductor substrate composed of single crystal silicon carbide which is constituted of a first resistance layer of a first conductivity type and having a first resistance and a second resistance layer of the first conductivity type, formed on said first resistance layer and having a second resistance less than said first resistance, and forming a semiconductor layer composed of silicon carbide of a second conductivity type on an upper surface of said semiconductor substrate; forming a semiconductor region of the first conductivity type in a region of said semiconductor layer; forming a groove to penetrate said semiconductor region and said semiconductor layer and to reach said second resistance layer of the first conductivity type; forming a first thermal oxidation film on inner surfaces of said groove; removing said first thermal oxidation film by means of etching; forming a second thermal oxidation film on said inner surfaces of said groove after said removing step; and forming a gate electrode layer on said second thermal oxidation film, a first electrode layer so as to contact both said semiconductor layer and said semiconductor region, and a second electrode layer on a lower surface of said semiconductor substrate to contact said first resistance layer; wherein the plane orientation of said upper surface of said semiconductor substrate composed of silicon carbide is one of a substantially (0001) carbon face of a hexagonal system and a substantially {111} carbon face of a cubic system, and wherein the plane orientation of said bottom surface of said groove in said step of forming a groove is substantially the same as that of said semiconductor substrate; and said second thermal oxidation film comprises a side surface oxidation film formed on said side surfaces of said groove and a bottom surface oxidation film having a thickness thicker than that of said side surface oxidation film an formed on said bottom surface of said groove.