Method for manufacturing silicon carbide semiconductor device

• US 9,543,412 B2
• Filed: 06/16/2015
• Issued: 01/10/2017
• 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: Hayashi, Hideki, Masuda, Takeyoshi
• Primary Examiner(s): Wilczewski, Mary
• Assistant Examiner(s): Peterson, Erik T
• Application Number:
  US14/740,812
• Publication Number:
  US 20150279967A1
• Time in Patent Office: 574 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H01L 21/02529 Silicon carbide
• CPC Class Codes: H01L 21/02636 Selective deposition, e.g. simultaneous growth of mono- and non-monocrystalline semiconductor materials
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• CPC Class Codes: H01L 21/28255 the insulator being formed after the semiconductor body, the semiconductor belonging to Group IV and not being elemental silicon, e.g. Ge, SiGe, SiGeC
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/308 using masks H01L21/3063, H01L21/3065 take precedence
• 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 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• CPC Class Codes: H01L 29/4236 within a trench, e.g. trench gate electrode, groove gate electrode
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/511 with a compositional variation, e.g. multilayer structures H01L29/516 takes precedence
• 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 29/66734 with a step of recessing the gate electrode, e.g. to form a trench gate electrode
• 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

Abstract

A silicon carbide substrate including a first layer having first conductivity type, a second layer having second conductivity type, and a third layer having the first conductivity type is formed. A trench provided with an inner surface having a side wall surface and a bottom surface is formed, the side wall surface extending through the third layer and the second layer and reaching the first layer, the bottom surface being formed of the first layer. A silicon film is formed to cover the bottom surface. A gate oxide film is formed on the inner surface by oxidation in the trench. The gate oxide film includes a first portion formed by oxidation of the silicon carbide substrate, and a second portion formed by oxidation of the silicon film on the bottom surface. Accordingly, a method for manufacturing a silicon carbide semiconductor device having a high breakdown voltage is provided.

Claims

1. A silicon carbide semiconductor device, comprising:

a silicon carbide substrate having an epitaxial layer;

a trench formed at said epitaxial layer having a side wall surface, a bottom surface, and a first corner portion between said side wall surface and said bottom surface;

a gate oxide film on an inner surface of said trench, said gate oxide film including a first portion extending on both said side wall surface and said bottom surface and a second portion on said first portion located on said bottom surface; and

a gate electrode on said gate oxide film,

said first portion having a second corner portion, covered with said second portion, at an upper surface of said first portion, said second portion having a third corner portion at an upper surface of said second portion, and a radius of curvature of said third corner portion being greater than a radius of curvature of said second corner portion.

2. The silicon carbide semiconductor device according to claim 1, wherein a carbon atom concentration of said second portion is lower than a carbon atom concentration of said first portion.

3. The silicon carbide semiconductor device according to claim 1, wherein a total thickness of said first portion and said second portion above said bottom surface is larger than a thickness of said first portion above said side wall surface by 300 nm or more.

4. The silicon carbide semiconductor device according to claim 1, wherein said epitaxial layer includes a first layer of a first conductivity type, a second layer of a second conductivity type on said first layer, and a third layer of said first conductivity type on said second layer,

said first corner portion locates at said first layer, said first portion extends from on said first layer to on said third layer, said second portion lies covering said first layer and does not extend on said second layer.

5. The silicon carbide semiconductor device according to claim 1, wherein said second portion has a central part and a pair of side end parts on said bottom surface of said trench, said central part is located between said side end parts, a thickness of each of said side end parts is greater than a thickness of said central part.

6. The silicon carbide semiconductor device according to claim 5, wherein said side end parts extend from on said first portion located on said bottom surface of said trench to said first portion located on said side wall surface of said trench.

7. The silicon carbide semiconductor device according to claim 1, wherein said second portion has a central part and a pair of side end parts on said bottom surface of said trench, each of said side end parts has said third corner portion on an upper surface thereof.

8. A silicon carbide semiconductor device, comprising:

a silicon carbide substrate having an epitaxial layer;

a trench formed at said epitaxial layer having a side wall surface, a bottom surface, and a first corner portion between said side wall surface and said bottom surface;

a gate oxide film on an inner surface of said trench, said gate oxide film including a first portion extending continuously from on said side wall surface to on said bottom surface and a second portion extending from on said first portion located on said bottom surface to on a part of said first portion located on said side wall surface; and

a gate electrode on said gate oxide film to contact said second portion and said first portion located on said side wall surface;

said first portion covering said first corner portion and having a second corner portion at a side end part of an upper surface of said first portion located on said bottom surface, said second portion covering said second corner portion, said second portion having a third corner portion at a side end part of an upper surface of said second portion, said second portion having a central part, a thickness of said side end part of said second portion being greater than a thickness of said central part of said second portion, and a radius of curvature of said third corner portion being greater than a radius of curvature of said second corner portion.

9. The silicon carbide semiconductor device according to claim 8, wherein a carbon atom concentration of said second portion is lower than a carbon atom concentration of said first portion.