Silicon-carbide semiconductor device and manufacturing method thereof

• US 9,954,072 B2
• Filed: 09/05/2013
• Issued: 04/24/2018
• Est. Priority Date: 10/18/2012
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Tanaka, Rina, Kagawa, Yasuhiro, Hino, Shiro, Miura, Naruhisa, Imaizumi, Masayuki
• Primary Examiner(s): Maldonado, Julio J
• Assistant Examiner(s): ISAAC, STANETTA D
• Application Number:
  US14/428,840
• Publication Number:
  US 20150236119A1
• Time in Patent Office: 1,692 Days
• CPC Class Codes: H01L 21/26586 characterised by the angle between the ion beam and the crystal planes or the main crystal surface
• CPC Class Codes: H01L 29/0623 Buried supplementary region, e.g. buried guard ring multi-RESURF H01L29/0634
• 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 29/66068 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 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

A silicon-carbide semiconductor device that relaxes field intensity in a gate insulating film, and that has a low ON-resistance. The silicon-carbide semiconductor device includes: an n-type silicon-carbide substrate; a drift layer formed on a topside of the n-type silicon-carbide substrate; a trench formed in the drift layer and that includes therein a gate insulating film and a gate electrode; a p-type high-concentration well region formed parallel to the trench with a spacing therefrom and that has a depth larger than that of the trench; and a p-type body region formed to have a depth that gradually increases when nearing from a position upward from the bottom end of the trench by approximately the thickness of the gate insulating film at the bottom of the trench toward the lower end of the p-type high-concentration well region.

Claims

1. A manufacturing method of a silicon-carbide semiconductor device, the method comprising:

a step of forming a drift layer made of silicon carbide of a first conductivity-type on a silicon-carbide semiconductor substrate of a first conductivity-type by an epitaxial growth method;

a step of forming a trench on a surface of the drift layer;

a step of forming a high-concentration well region of a second conductivity-type with a predetermined spacing from the trench by ion implantation so that the high-concentration well region has a depth larger than that of the trench;

a step of embedding the trench with an embedding material;

a step of forming a body region of the second conductivity-type by performing oblique ion implantation through the trench embedded with the embedded material to form the body region of the second conductivity-type such that the body region has a depth that increases as the bottom end of the high-concentration well region of the second conductivity-type is approached from a position upward from the bottom of the trench;

a step of removing the embedded material after having formed the body region;

a step of forming a gate insulating film on an inner wall surface of the trench; and

a step of forming a gate electrode within the gate insulating film.

2. The manufacturing method of a silicon-carbide semiconductor device according to claim 1, wherein

the body region forming step is a step of forming a body region in which an impurity concentration is higher on a side of the high-concentration well region than on a side of the trench.

3. The manufacturing method of a silicon-carbide semiconductor device according to claim 2, wherein

the step of forming the body region is a step of forming a body region that includes a grading layer in which the impurity concentration gradually increases as the high-concentration well region is approached.

4. The manufacturing method of a silicon-carbide semiconductor device according to claim 1, wherein

the step of forming the body region is a step of forming a body region such that a bottom of the body region that makes contact with the side of the trench is positioned upward from a bottom of the trench by a distance within ±

50 nanometers relative to a thickness of the gate insulating film at the bottom of the trench.

5. The manufacturing method of a silicon-carbide semiconductor device according to claim 1, wherein

the silicon-carbide semiconductor substrate of the first conductivity-type is a silicon-carbide semiconductor substrate an n-type, and

the step of forming the body region is a step of forming a body region of p-type of which acceptor concentration is 1×

10¹⁶/cm³ to 1×

10¹⁸/cm³.

6. The manufacturing method of a silicon-carbide semiconductor device according to claim 1, wherein:

the step of removing the embedded material comprises dissolving the embedded material.

7. A manufacturing method of a silicon-carbide semiconductor device, the method comprising:

a step of forming a drift layer made of silicon carbide of a first conductivity-type on a silicon-carbide semiconductor substrate of a first conductivity-type by an epitaxial growth method;

a step of forming a trench on a surface of the drift layer;

a step of forming a high-concentration well region of a second conductivity-type with a predetermined spacing from the trench by ion implantation so that the high-concentration well region has a depth larger than that of the trench;

a step of forming a body region of a second conductivity-type by oblique ion implantation through the trench so that the body region has a depth which increases, when nearing, from a position upward from a bottom of the trench toward a bottom end of the high-concentration well region of the second conductivity-type;

a step of forming a high-concentration layer of a first conductivity-type, of which impurity concentration is higher than that of the drift layer, in a region making contact with a bottom of the trench in the drift layer;

a step of forming a gate insulating film on an inner wall surface of the trench; and

a step of forming a gate electrode within the gate insulating film.

8. The manufacturing method of a silicon-carbide semiconductor device according to claim 7, wherein

the step of forming the body region is a step of forming a body region such that a bottom of the body region that makes contact with the side of the trench is positioned upward from a bottom of the trench by a distance within ±

50 nanometers relative to a thickness of the gate insulating film at the bottom of the trench.

9. The manufacturing method of a silicon-carbide semiconductor device according to claim 7, wherein

the silicon-carbide semiconductor substrate of the first conductivity-type is a silicon-carbide semiconductor substrate an n-type, and

the step of forming the body region is a step of forming a body region of p-type of which acceptor concentration is 1×

10¹⁶/cm³ to 1×

10¹⁸/cm³.

10. A silicon-carbide semiconductor device comprising:

a silicon-carbide semiconductor substrate of a first conductivity-type;

a drift layer formed on a first surface of the silicon-carbide semiconductor substrate, the drift layer being made of silicon carbide of a first conductivity-type of which concentration is lower than that of the silicon-carbide semiconductor substrate;

a trench that is formed in the drift layer;

a gate insulating film that is formed on an inner wall surface of the trench;

a gate electrode that is formed within the gate insulating film;

a high-concentration well region formed with a predetermined spacing from the trench, the high-concentration well region being formed so as to have a depth larger than that of the trench and being made of silicon carbide of a second conductivity-type;

a body region, made of silicon carbide of the second conductivity-type, that

is formed from an end of the gate electrode at a bottom side of the trench and surrounds the trench, and

is formed such that a depth of the body region increases as a bottom of the high-concentration well region is approached; and

a source region

formed in an upper-layer portion of the body region,

formed of silicon carbide of a first conductivity-type of which concentration is higher than that of the drift layer, and

formed so as to make contact with a side of the trench;

wherein

a high-concentration layer of a first conductivity-type, of which impurity concentration is higher than that of the drift layer, is formed in a region of the drift layer, the region making contact with the bottom surface of the trench.

11. The silicon-carbide semiconductor device according to claim 10, wherein

a thickness of the high-concentration layer of the first conductivity-type is 0.1 micrometer to 0.3 micrometer.

12. The silicon-carbide semiconductor device according to claim 10, wherein

the high-concentration layer of the first conductivity-type has an impurity concentration twice to 10 times as high as that of the drift layer.