Bonding material, bonding method and semiconductor device for electric power

Patent metadata

Field	Value
Publication number	US-2016351523-A1
Application number	US-201415112078-A
Country	US
Kind code	A1
Filing date	Dec 26, 2014
Priority date	Feb 10, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

The present invention has an object to achieve bonding which satisfies both in heat resistivity and in stress-relaxation ability, and the bonding material according to this invention is a sheet-like bonding material 1 made of a silver-bismuth alloy which, when heated in a state being in contact with a metal material as a bonding target (for example, surface layers 2 f, 3 f ), forms in the metal material (as its material, for example, gold, silver or copper) a diffusion layer Ld 2 , Ld 3 of silver due to solid-phase diffusion reaction, so as to be bonded to the metal material, said bonding material being characterized by containing not less than 1 mass % but not more than 5 mass % of bismuth.

First claim

1 - 11 . (canceled)

12 . A bonding material comprising an alloy containing bismuth and composed mainly of silver, which, when heated in a state being in contact with a metal material as a bonding target, forms in the metal material a diffusion layer of silver due to solid-phase diffusion reaction, so as to be bonded to the metal material,
said bonding material containing not less than 1 mass % but not more than 5 mass % of bismuth.

13 . The bonding material according to claim 12 , wherein, in the silver-bismuth alloy, a grain size of bismuth-rich phase is 0.2 to 1.0 μm.

14 . The bonding material according to claim 12 , which is a plate material having a thickness of 50 μm to 100 μm.

15 . The bonding material according to claim 13 , which is a plate material having a thickness of 50 μm to 100 μm.

16 . A method of bonding by use of the bonding material according to claim 12 , comprising:
a heat treatment step of heat treating the bonding material at a temperature of not less than 150° C. but not more than 300° C.; and a diffusion-layer forming step of sandwiching the bonding material after subjected to the heat treatment step between two bonding targets, and heating them at a temperature lower than a melting point of the bonding material, to thereby form the diffusion layer of silver in each of said two bonding targets.

17 . A method of bonding by use of the bonding material according to claim 13 , comprising:
a heat treatment step of heat treating the bonding material at a temperature of not less than 150° C. but not more than 300° C.; and a diffusion-layer forming step of sandwiching the bonding material after subjected to the heat treatment step between two bonding targets, and heating them at a temperature lower than a melting point of the bonding material, to thereby form the diffusion layer of silver in each of said two bonding targets.

18 . The bonding method according to claim 16 , wherein a time period for heat treating is not less than 10 hours but not more than 100 hours.

19 . The bonding method according to claim 17 , wherein a time period for heat treating is not less than 10 hours but not more than 100 hours.

20 . The bonding method according to claim 16 , wherein the temperature in the diffusion-layer forming step is not less than 250° C. but not more than 300° C.

21 . The bonding method according to claim 17 , wherein the temperature in the diffusion-layer forming step is not less than 250° C. but not more than 300° C.

22 . The bonding method according to claim 16 , wherein the diffusion-layer forming step is performed in a reductive atmosphere.

23 . The bonding method according to claim 17 , wherein the diffusion-layer forming step is performed in a reductive atmosphere.

24 . A semiconductor device for electric power comprising:
a circuit board on which a circuit pattern is formed; and a semiconductor element for electric power bonded to the circuit pattern; wherein a bonding portion between the circuit board and the semiconductor element for electric power is formed of: a first diffusion layer formed in the side of the semiconductor element for electric power; a bonding material made of an alloy containing bismuth and composed mainly of silver; and a second diffusion layer formed in the side of the circuit board; and wherein the first diffusion layer and the second diffusion layer are provided by diffusion of silver from the bonding material to thereby be bonded to the bonding material.

25 . The semiconductor device for electric power according to claim 24 , wherein the first diffusion layer and the second diffusion layer are formed in such a manner that silver diffuses into a metal layer of any one of gold, silver and copper.

26 . The semiconductor device for electric power according to claim 24 , wherein the semiconductor element for electric power is formed of a wide bandgap semiconductor material.

27 . The semiconductor device for electric power according to claim 25 , wherein the semiconductor element for electric power is formed of a wide bandgap semiconductor material.

28 . The semiconductor device for electric power of claim 26 , wherein the wide bandgap semiconductor material is one of silicon carbide, a gallium nitride-series material or diamond.

29 . The semiconductor device for electric power of claim 27 , wherein the wide bandgap semiconductor material is one of silicon carbide, a gallium nitride-series material or diamond.

30 . An alloy that is predominantly silver and that comprises 1 mass % to 5 mass % bismuth, wherein said alloy when placed in contact with a metal material at a temperature ranging from 150° C. to 300° C. forms a diffusion layer of silver thus bonding it to the metal material.

31 . A method of bonding at least two metals together comprising contacting each metal with an intervening amount of the alloy according to claim 30 at a temperature ranging from 150° C. to 300° C.

Assignees

• Mitsubishi Electric Corp

Inventors

• Yamazaki Koji

Classifications

• H10W72/07653

  changes in shapes · CPC title

• H10W90/763

  between laterally-adjacent chips · CPC title

• H10W74/00

  Encapsulations, e.g. protective coatings · CPC title

• H10W72/0113

  Apparatus for manufacturing die-attach connectors · CPC title

• H10W72/944

  Dispositions of multiple bond pads · CPC title