# US 2014/0151719 A1 · Silicon carbide semiconductor element

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- Number: US 2014/0151719 A1
- Document ID: US20140151719A1
- Status: Published application
- Kind: A1
- Application number: 14/172,075
- Filed: 2014-02-04
- Published: 2014-06-05
- Earliest claimed: 2011-06-27
- Assignees: Panasonic Corporation
- Applicants: Panasonic Corporation
- Inventors: Kunimasa TAKAHASHI; Masahiko NIWAYAMA; Masao UCHIDA; Chiaki KUDOU
- Web page: https://patentgrep.com/patent/US20140151719A1

## CPC

- H10D 30/668: {having trench gate electrodes, e.g. UMOS transistors}
- H10D 12/031: {of IGBTs}
- H10D 12/038: {having a recessed gate, e.g. trench-gate IGBTs}
- H10D 30/025: {of vertical IGFETs (of VDMOS H10D30/0291; of vertical TFTs H10D30/0318)}
- H10D 30/0297: {using recessing of the gate electrodes, e.g. to form trench gate electrodes}
- H10D 30/63: Vertical IGFETs (H10D30/66 {, H10D30/6728, H10D30/689, H10D30/693} take precedence)
- H10D 30/635: {having no inversion channels, e.g. vertical accumulation channel FETs [ACCUFET] or normally-on vertical IGFETs}
- H10D 62/235: {of IGFETs (IGFETs having buried channels H10D30/637)}
- H10D 62/299: {having lateral doping variations (IGFETs having lightly doped source or drain extensions H10D30/601)}
- H10D 62/8325: {Silicon carbide}
- H10D 64/513: {within recesses in the substrate, e.g. trench gates, groove gates or buried gates}
- H10D 64/516: {the thicknesses being non-uniform}
- H10D 62/405: {Orientations of crystalline planes}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

This silicon carbide semiconductor element includes: a body region of a second conductivity type which is located on a drift layer of a first conductivity type; an impurity region of the first conductivity type which is located on the body region; a trench which runs through the body region and the impurity region to reach the drift layer; a gate insulating film which is arranged on surfaces of the trench; and a gate electrode which is arranged on the gate insulating film. The surfaces of the trench include a first side surface and a second side surface which is opposed to the first side surface. The concentration of a dopant of the second conductivity type is higher at least locally in a portion of the body region which is located beside the first side surface than in another portion of the body region which is located beside the second side surface.

## Claims

### Claim 1

A silicon carbide semiconductor element comprising:
a semiconductor substrate of a first conductivity type;
a drift layer of the first conductivity type which is located on the principal surface of the semiconductor substrate;
a body region of a second conductivity type which is located on the drift layer;
an impurity region of the first conductivity type which is located on the body region;
a trench which runs through the body region and the impurity region to reach the drift layer;
a gate insulating film which is arranged on surfaces of the trench;
a gate electrode which is arranged on the gate insulating film;
a first electrode which contacts with the impurity region;
a second electrode which is arranged on the back surface of the semiconductor substrate; and
a channel layer of the first conductivity type,
wherein the surfaces of the trench include a first side surface and a second side surface which is opposed to the first side surface,
wherein the channel layer is arranged between the first and second side surfaces of the trench and the gate insulating film,
wherein a portion of the channel layer which contacts with a part of the body region that is exposed on the first side surface is thicker than another portion of the channel layer which contacts with another part of the body region that is exposed on the second side surface, and
wherein the concentration of a dopant of the second conductivity type is higher at least locally in a portion of the body region which is located beside the first side surface than in another portion of the body region which is located beside the second side surface.

### Claim 2 (depends on 1)

The silicon carbide semiconductor element of claim 1, wherein a body concentration adjusting region including the dopant of the second conductivity type in a higher concentration than the body region is provided at least in some depth range of the portion of the body region which is located beside the first side surface.

### Claim 3 (depends on 1)

The silicon carbide semiconductor element of claim 1, wherein a body concentration adjusting region including the dopant of the second conductivity type in a lower concentration than the body region is provided at least in some depth range of the portion of the body region which is located beside the second side surface.

### Claim 4 (depends on 1)

The silicon carbide semiconductor element of claim 1, wherein the semiconductor substrate is a 4H—SiC substrate, of which the principal surface defines a tilt angle of 2 to 10 degrees with respect to either a (0001) Si plane or a (000-1) C plane.

### Claim 5 (depends on 1)

The silicon carbide semiconductor element of claim 1, wherein the first and second side surfaces are arranged substantially perpendicularly to the direction in which the principal surface of the semiconductor substrate tilts with respect to the (0001) Si plane or the (000-1) C plane.

### Claim 6 (depends on 1)

The silicon carbide semiconductor element of claim 1, wherein the principal surface of the semiconductor substrate tilts in a <11-20> direction with respect to the (0001) Si plane or the (000-1) C plane and wherein the first and second side surfaces are arranged substantially perpendicularly to the <11-20> direction.

### Claim 7 (depends on 1)

The silicon carbide semiconductor element of claim 1, wherein the channel layer of the first conductivity type has been formed by epitaxial growth.

### Claim 8 (depends on 1)

The silicon carbide semiconductor element of claim 1, wherein a difference in threshold voltage between the two opposing sidewall surfaces of the trench is equal to or smaller than 0.1 V.

### Claim 9 (depends on 1)

The silicon carbide semiconductor element of claim 1, wherein when viewed perpendicularly to the principal surface of the semiconductor substrate, the trench has the shape of a rectangle on a plan view, and
wherein the first and second side surfaces form the longer sides of the rectangle.