# US 6,294,444 B1 · Method for manufacturing silicon carbide semiconductor device

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- Number: US 6,294,444 B1
- Document ID: US6294444B1
- Status: Granted
- Kind: B1
- Application number: 09/359,362
- Filed: 1999-07-21
- Granted: 2001-09-25
- Earliest claimed: 1998-07-21
- Assignees: Fuji Electric Co., Ltd.
- Inventors: Katsunori Ueno
- Web page: https://patentgrep.com/patent/US6294444B1

## CPC

- H10P 30/21: {of electrically active species}
- H10P 30/2042: {into crystalline silicon carbide}
- H10P 30/28: characterised by an annealing step, e.g. for activation of dopants
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

In a method for manufacturing a silicon carbide semiconductor device, preliminary heat treatment is conducted after implanting impurity ions into a silicon carbide substrate, such that the silicon carbide substrate is heated at a temperature in a range of, for example, 800 to 1200° C., in a hydrogen atmosphere or a mixed gas ambient comprising hydrogen and inert gas. After the preliminary heat treatment, the silicon carbide substrate may be annealed at a high temperature.

## Claims

### Claim 1

A method for manufacturing a silicon carbide semiconductor device, comprising the steps of:
conducting preliminary heat treatment after implanting impurity ions into a silicon carbide substrate, said preliminary heat treatment comprising a step of heating the silicon carbide substrate in an atmosphere comprising hydrogen or a mixture of hydrogen and an inert gas at a temperature of at least 800° C.; and
annealing the silicon carbide substrate at a temperature greater than the temperature of said preliminary heat treatment.

### Claim 2 (depends on 1)

A method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the atmosphere comprising the mixture and hydrogen gas in which the preliminary heat treatment is conducted contains at least 20% of hydrogen.

### Claim 3 (depends on 1)

A method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the atmosphere in which the preliminary heat treatment is conducted further comprises a hydrochloric acid gas.

### Claim 4 (depends on 2)

A method for manufacturing a silicon carbide semiconductor device according to claim 2, wherein the atmosphere in which the preliminary heat treatment is conducted further comprises a hydrochloric acid gas.

### Claim 5 (depends on 3)

A method for manufacturing a silicon carbide semiconductor device according to claim 3, wherein the hydrochloric acid gas is contained in an amount of not larger than 5% of hydrogen.

### Claim 6 (depends on 4)

A method for manufacturing a silicon carbide semiconductor device according to claim 4, wherein the hydrochloric acid gas is contained in an amount of not larger than 5% of hydrogen.

### Claim 7 (depends on 1)

A method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the preliminary heat treatment is conducted at a temperature in a range of 800 to 1200° C.

### Claim 8 (depends on 2)

A method for manufacturing a silicon carbide semiconductor device according to claim 2, wherein the preliminary heat treatment is conducted at a temperature in a range of 800 to 1200° C.

### Claim 9 (depends on 7)

A method for manufacturing a silicon carbide semiconductor device according to claim 7, wherein the silicon carbide substrate is annealed at least 1200° C. immediately after the preliminary heat treatment.

### Claim 10 (depends on 8)

A method for manufacturing a silicon carbide semiconductor device according to claim 8, wherein the silicon carbide substrate is annealed at least 1200° C. immediately after the preliminary heat treatment.

### Claim 11 (depends on 7)

A method for manufacturing a silicon carbide semiconductor device according to claim 7, further comprising the step of conducting prior heat treatment at a temperature in a range of 800 to 1200° C. before the preliminary heat treatment.

### Claim 12 (depends on 8)

A method for manufacturing a silicon carbide semiconductor device according to claim 8, further comprising the step of conducting prior heat treatment at a temperature in a range of 800 to 1200° C. before the preliminary heat treatment.

### Claim 13 (depends on 1)

A method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the preliminary heat treatment is conducted for at least five minutes.

### Claim 14 (depends on 2)

A method for manufacturing a silicon carbide semiconductor device according to claim 2, wherein the preliminary heat treatment is conducted for at least five minutes.

### Claim 15 (depends on 1)

A method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the preliminary heat treatment is conducted after an oxide film is removed.

### Claim 16 (depends on 2)

A method for manufacturing a silicon carbide semiconductor device according to claim 2, wherein the preliminary heat treatment is conducted after an oxide film is removed.

### Claim 17 (depends on 1)

A method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein said silicon carbide substrate comprises one of 4H—SiC and 6H—SiC crystals.

### Claim 18 (depends on 2)

A method for manufacturing a silicon carbide semiconductor device according to claim 2, wherein said silicon carbide substrate comprises one of 4H—SiC and 6H—SiC crystals.