Silicon carbide semiconductor device and method of manufacturing silicon carbide semiconductor device

Patent metadata

Field	Value
Publication number	US-2016254393-A1
Application number	US-201615152522-A
Country	US
Kind code	A1
Filing date	May 11, 2016
Priority date	Nov 22, 2013
Publication date	Sep 1, 2016
Grant date	—

Abstract

In forming an ohmic electrode on a back surface of an n-type SiC substrate, an n + -type semiconductor region is formed in a surface layer of the back surface of an n-type epitaxial substrate by ion implantation. In this ion implantation, the impurity concentration of the n + -type semiconductor region is a predetermined range and preferably a predetermined value or less, and an n-type impurity is implanted by acceleration energy of a predetermined range such that the n + -type semiconductor region has a predetermined thickness or less. Thereafter, a nickel layer and a titanium layer are sequentially formed on the surface of the n + -type semiconductor region, the nickel layer is heat treated to form a silicide, and the ohmic electrode formed from nickel silicide is formed. In this manner, a back surface electrode that has favorable properties can be formed while peeling of the back surface electrode can be suppressed.

First claim

What is claimed is:

1 . A method of manufacturing a silicon carbide semiconductor device, comprising:
implanting an impurity into a back surface of a semiconductor substrate formed from silicon carbide to thereby form in a surface layer of the back surface of the semiconductor substrate a high-concentration semiconductor region that has an impurity concentration that is higher than that of the semiconductor substrate; forming a metal electrode on a surface of the high-concentration semiconductor region; and performing a heat treatment to form an ohmic contact of the metal electrode and the high-concentration semiconductor region, wherein the impurity concentration of the high-concentration semiconductor region is a range from 1×10 19 /cm 3 to 8×10 20 /cm 3 , a thickness of the high-concentration semiconductor region is a first thickness of 200 nm or less, and the impurity is implanted by acceleration energy of 150 keV or less.

2 . The method according to claim 1 , wherein
the high-concentration semiconductor region is formed to have a second thickness greater than the first thickness, and the thickness of the high-concentration semiconductor region is reduced to the first thickness of 200 nm or less.

3 . The method according to claim 1 , wherein
the impurity concentration of the high-concentration semiconductor region is 4×10 20 /cm 3 or less.

4 . The method according to claim 1 , wherein
one of aluminum, phosphorus, arsenic, nitrogen, boron, magnesium, and gallium is implanted as the impurity.

5 . The method according to claim 1 , wherein
when forming the metal electrode comprises sequentially forming a nickel layer and a titanium layer on the surface of the high-concentration semiconductor region, and forming the ohmic contact comprises heat-treating the nickel layer and the high-concentration semiconductor region to form a nickel silicide layer as the metal electrode.

6 . The method according to claim 1 , further comprising: forming a front surface semiconductor device structure in a front surface side of the semiconductor substrate.

7 . The method according to claim 6 , wherein forming the front surface semiconductor device structure includes performing ion implantation in the front surface of the semiconductor substrate to form a plurality of semiconductor regions having an impurity concentration different than the semiconductor substrate, the plurality of semiconductor regions spaced apart from each other.

8 . The method according to claim 7 , further comprising:
forming a Schottky electrode on the plurality of semiconductor regions.

9 . The method according to claim 8 , wherein forming the Schottky electrode comprises:
forming an insulating film on the semiconductor substrate and the plurality of semiconductor regions; removing a portion of the insulating film over an active region of the semiconductor substrate including the plurality of semiconductor regions; and depositing a conductive material on the insulating film and the active region to form the Schottky electrode.

10 . The method according to claim 9 , wherein the conductive material is titanium.

11 . A silicon carbide semiconductor device comprising:
a high-concentration semiconductor region located in a surface layer of a back surface of a semiconductor substrate formed of silicon carbide and having an impurity concentration higher than that of the semiconductor substrate; and a metal electrode located on a surface of the high-concentration semiconductor region and forming an ohmic contact with the high-concentration semiconductor region, wherein the impurity concentration of the high-concentration semiconductor region is a range from 1×10 19 /cm 3 to 8×10 20 /cm 3 , a thickness of the high-concentration semiconductor region is 200 nm or less, and the high-concentration semiconductor region is formed by implantation of one of aluminum, magnesium, and gallium.

12 . The silicon carbide semiconductor device according to claim 11 , wherein
the impurity concentration of the high-concentration semiconductor region is 4×10 20 /cm 3 or less.

13 . The silicon carbide semiconductor device according to claim 11 , wherein
the metal electrode is a nickel silicide layer.

14 . The silicon carbide semiconductor device according to claim 11 , wherein
a front surface semiconductor device structure is disposed in a front surface side of the semiconductor substrate.

15 . The silicon carbide semiconductor device of claim 14 , wherein the front surface semiconductor device structure includes a plurality of semiconductor regions having an impurity concentration different than the semiconductor substrate, the plurality of semiconductor regions spaced apart from each other.

16 . The silicon carbide semiconductor device of claim 15 , further comprising:
a Schottky electrode on the plurality of semiconductor regions.

17 . The silicon carbide semiconductor device of claim 16 , further comprising:
an insulation layer on the semiconductor substrate and including an opening to expose an active region including the plurality of semiconductor regions, wherein the Schottky electrode comprises titanium located on the insulating layer and the active region.

Assignees

• Fuji Electric Co Ltd

Inventors

• Ohse Naoyuki
• Imai Fumikazu
• Nakajima Tsunehiro
• Fukuda Kenji
• Harada Shinsuke
• Okamoto Mitsuo

Classifications

• H10P30/2042

  into crystalline silicon carbide · CPC title

• H10P30/21

  of electrically active species · CPC title

• H10D64/0123

  to silicon carbide · CPC title

• H10D8/051

  of Schottky diodes · CPC title

• H10D62/129

  Cathode regions of diodes · CPC title