Method for manufacturing silicon carbide semiconductor device

• US 8,927,368 B2
• Filed: 08/02/2013
• Issued: 01/06/2015
• Est. Priority Date: 09/12/2012
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Saitoh, Yu, Masuda, Takeyoshi, Hayashi, Hideki
• Primary Examiner(s): Wilczewski, Mary
• Assistant Examiner(s): Peterson, Erik T
• Application Number:
  US13/958,151
• Publication Number:
  US 20140073101A1
• Time in Patent Office: 522 Days
• Field of Search: 438/138, 438/197, 438/212, 438/268, 438/270, 438/589, 438/931, 257/329, 257/330, 257/440
• US Class Current: 438/270
• CPC Class Codes: H01L 21/02236 group IV semiconductor
• CPC Class Codes: H01L 21/02255 formation by thermal treatment H01L21/02252 takes precedence; after treatment of an insulating film H01L21/3105 and subgroups
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 29/045 by their particular orientation of crystalline planes
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/401 Multistep manufacturing processes
• CPC Class Codes: H01L 29/4236 within a trench, e.g. trench gate electrode, groove gate electrode
• CPC Class Codes: H01L 29/42364 characterised by the insulating layer, e.g. thickness or uniformity H01L29/42324 and H01L29/4234 take precedence
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/66068 the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
• CPC Class Codes: H01L 29/66666 Vertical transistors H01L29/66712, H01L29/66742 take precedence
• CPC Class Codes: H01L 29/7397 and a gate structure lying on a slanted or vertical surface or formed in a groove, e.g. trench gate IGBT
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/7827 Vertical transistors H01L29/7802, H01L29/78642 take precedence
• CPC Class Codes: Y10S 438/931 Silicon carbide semiconductor

Abstract

A trench having a side wall and a bottom portion is formed in a silicon carbide substrate. A trench insulating film is formed to cover the bottom portion and the side wall. A silicon film is formed to fill the trench with the trench insulating film being interposed therebetween. The silicon film is etched so as to leave a portion of the silicon film that is disposed on the bottom portion with the trench insulating film being interposed therebetween. The trench insulating film is removed from the side wall. By oxidizing the silicon film, a bottom insulating film is formed. A side wall insulating film is formed on the side wall.

Claims

1. A method for manufacturing a silicon carbide semiconductor device comprising the steps of:

preparing a silicon carbide substrate including a first layer that has first conductivity type, a second layer that is provided on said first layer and that has second conductivity type, and a third layer that is provided on said second layer, that is separated from said first layer by said second layer, and that has said first conductivity type;

forming a trench in said silicon carbide substrate, said trench having a side wall and a bottom portion, said side wall extending through said third layer and said second layer and reaching said first layer, said bottom portion being formed of said first layer;

forming a trench insulating film to cover each of said bottom portion and said side wall;

forming a silicon film to fill said trench with said trench insulating film being interposed therebetween;

partially etching said silicon film so as to expose a portion of said trench insulating film that covers said second layer on said side wall and so as to leave a portion of said silicon film that is disposed on said bottom portion with said trench insulating film being interposed therebetween;

exposing said second layer on said side wall by removing the portion of said trench insulating film that covers said second layer on said side wall, after the step of partially etching said silicon film;

forming a bottom insulating film which contacts said trench insulating film covering said bottom portion of said trench by entirely converting said silicon film on said trench insulating film into an oxide film, after the step of exposing said second layer;

forming a side wall insulating film to cover said second layer on said side wall, after the step of exposing said second layer; and

forming a gate electrode on said side wall with said side wall insulating film being interposed therebetween.

2. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of forming said side wall insulating film is performed by thermal oxidation.

3. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of forming said trench insulating film is performed by thermal oxidation.

4. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of partially etching said silicon film includes the step of performing etching having a physical etching effect.

5. The method for manufacturing the silicon carbide semiconductor device according to claim 1, further comprising the step of flattening said silicon film before the step of partially etching said silicon film.

6. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of forming said bottom insulating film includes the step of oxidizing said silicon film by thermally oxidizing silicon at not less than 900°

C. and not more than 1100°

C.

7. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of forming said side wall insulating film includes the step of heating said silicon carbide substrate so as to thermally oxidize said silicon carbide substrate, and the step of heating said silicon carbide substrate includes the step of supplying oxygen to said silicon carbide substrate while increasing a temperature of said silicon carbide substrate.

8. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of partially etching said silicon film includes the step of performing dry etching using a gas containing sulfur hexafluoride.

9. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of partially etching said silicon film is performed to provide said silicon film with a thickness of less than 300 nm.

10. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein a thickness of the bottom insulating film is greater than a thickness of the trench insulating film.

11. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of forming said bottom insulating film includes converting said silicon film into said oxide film across an entire thickness of said silicon film.

12. The method for manufacturing the silicon carbide semiconductor device according to claim 1, wherein the step of forming said bottom insulating film includes the step of forming said bottom insulating film on said trench insulating film without leaving said silicon film between said trench insulating film and said bottom insulating film.