Wide band gap semiconductor device

• US 9,761,705 B2
• Filed: 04/12/2016
• Issued: 09/12/2017
• Est. Priority Date: 11/29/2012
• Status: Active Grant

• Current Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Original Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Kumagai, Naoki
• Primary Examiner(s): Sefer, A.
• Application Number:
  US15/096,801
• Publication Number:
  US 20160225894A1
• Time in Patent Office: 518 Days
• CPC Class Codes: H01L 29/0696 of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
• CPC Class Codes: H01L 29/0865 Disposition
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/1095 Body region, i.e. base region, of DMOS transistors or IGBTs cell layout H01L29/0696
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• 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 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

A semiconductor device comprises an n+ type SiC semiconductor substrate, an n type low concentration drift layer of an SiC semiconductor on the substrate, p type channel regions selectively arranged in the drift layer with a specified distance between the channel regions, an n type source region selectively arranged in the channel region, a source electrode in common contact with the source region and the channel region, and a gate electrode disposed over the drift layer between two channel regions, and over a part of the channel region positioned between the drift layer and the source region intercalating a gate oxide film therebetween. The drift layer has a low concentration of at most 70% of the concentration that is required to exhibit a specified withstand voltage at a minimum ON resistance.

Claims

1. A wide band gap semiconductor device comprising:

a wide band gap semiconductor substrate of a first conductivity type with a high impurity concentration;

a drift layer of the first conductivity type with a low impurity concentration composed of a wide band gap semiconductor material on the substrate;

a channel region of a second conductivity type selectively formed in a surface region of the drift layer;

a source region of the first conductivity type selectively arranged in a surface region of the channel region of the second conductivity type;

a source electrode in common contact with a surface of the source region and a surface of the channel region;

a plurality of gate trenches formed from a surface of the source region of the first conductivity type through the channel region reaching the drift layer; and

a gate electrode embedded in each of the gate trenches interposing a gate oxide film on an inner surface of the gate trench;

wherein an impurity concentration of the drift layer of the first conductivity type with a low impurity concentration composed of a wide band gap semiconductor material is in a range from 33% to 60% of an impurity concentration that is 1.3×

10¹⁶ cm<sup>−

3</sup> in an element with a withstand voltage of 1200 V and 8.0×

10¹⁶ cm<sup>−

3</sup> in an element with a withstand voltage 1700 V.

2. The wide band gap semiconductor device according to claim 1, wherein the gate oxide film is thicker on a bottom of the trench than on a side wall of the trench.

3. The wide band gap semiconductor device according to claim 1, wherein the wide band gap semiconductor material is selected from the group consisting of silicon carbide (SiC) semiconductor, gallium nitride (GaN) semiconductor, and diamond.

4. A wide band gap semiconductor device comprising:

a wide band gap semiconductor substrate of a first conductivity type with a high impurity concentration;

a drift layer of the first conductivity type with a low impurity concentration composed of a wide band gap semiconductor material on the substrate;

a channel region of a second conductivity type selectively formed in a surface region of the drift layer;

a source region of the first conductivity type selectively arranged in a surface region of the channel region of the second conductivity type;

a source electrode in common contact with a surface of the source region and a surface of the channel region;

a plurality of gate trenches and a plurality of source trenches, each of the gate trenches and the source trenches being formed from a surface of the source region of the first conductivity type through the channel region reaching the drift layer and being arranged alternately;

a gate electrode embedded in each of the gate trenches interposing a gate oxide film on an inner surface of the gate trench; and

a base region of the second conductivity type with a high impurity concentration disposed at a bottom of each of the source trenches;

wherein the source electrode that is in common contact with the base region and the source region both exposing to a side wall of the source trench is embedded in the source trench, and

wherein an impurity concentration of the drift layer of the first conductivity type with a low impurity concentration composed of a wide band gap semiconductor material is in a range from 33% to 60% of an impurity concentration that is 1.3×

10¹⁶ cm<sup>−

3</sup> in an element with a withstand voltage of 1200 V and 8.0×

10¹⁶ cm<sup>−

3</sup> in an element with a withstand voltage 1700 V.

5. The wide band gap semiconductor device according to claim 4, wherein the wide band gap semiconductor material is selected from the group consisting of silicon carbide (SiC) semiconductor, gallium nitride (GaN) semiconductor, and diamond.