Ceramic-metal composite structure and process of producing same

• US 5,561,321 A
• Filed: 11/08/1993
• Issued: 10/01/1996
• Est. Priority Date: 07/03/1992
• Status: Expired due to Fees

• Current Assignee: Noritake Company Limited (Noritake)
• Original Assignee: Noritake Company Limited (Noritake)
• Inventors: Hirano, Masanori, Yamauchi, Noriyoshi
• Primary Examiner(s): BROWN, PETER T
• Application Number:
  US08/146,086
• Time in Patent Office: 1,058 Days
• Field of Search: 257/701-703, 257/705, 257/706, 257/700, 257/675, 437/192, 437/218, 361/705, 361/708, 361/712, 428/610, 428/615, 428/618, 428/632, 428/620-623, 428/627-630, 428/660-665, 428/613
• US Class Current: 257/700
• CPC Class Codes: B32B 15/01 all layers being exclusively metallic making layered metal workpieces by pressure cladding B23K20/22; making coatings with a metallic material characterised by its composition C23C30/00
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
• CPC Class Codes: C04B 2235/5436 micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/6025 Tape casting, e.g. with a doctor blade
• CPC Class Codes: C04B 2235/6582 Hydrogen containing atmosphere
• CPC Class Codes: C04B 2235/72 Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics
• CPC Class Codes: C04B 2237/122 based on refractory metals
• CPC Class Codes: C04B 2237/123 based on iron group metals, e.g. steel
• CPC Class Codes: C04B 2237/124 based on copper
• CPC Class Codes: C04B 2237/125 based on noble metals, e.g. silver
• CPC Class Codes: C04B 2237/34 Oxidic
• CPC Class Codes: C04B 2237/341 Silica or silicates
• CPC Class Codes: C04B 2237/343 Alumina or aluminates
• CPC Class Codes: C04B 2237/348 Zirconia, hafnia, zirconates or hafnates
• CPC Class Codes: C04B 2237/36 Non-oxidic
• CPC Class Codes: C04B 2237/361 Boron nitride
• CPC Class Codes: C04B 2237/365 Silicon carbide
• CPC Class Codes: C04B 2237/366 : Aluminium nitride
• CPC Class Codes: C04B 2237/368 : Silicon nitride
• CPC Class Codes: C04B 2237/407 : Copper
• CPC Class Codes: C04B 2237/704 : of one or more of the ceramic layers or articles
• CPC Class Codes: C04B 2237/72 : Forming laminates or joined articles comprising at least two interlayers directly next to each other
• CPC Class Codes: C04B 35/111 : Fine ceramics
• CPC Class Codes: C04B 35/185 : Mullite 3Al2O3-2SiO2
• CPC Class Codes: C04B 35/581 : based on aluminium nitride
• CPC Class Codes: C04B 35/584 : based on silicon nitride
• CPC Class Codes: C04B 35/62655 : Drying, e.g. freeze-drying, spray-drying, microwave or supercritical drying
• CPC Class Codes: C04B 35/634 : Polymers C04B35/636 takes precedence
• CPC Class Codes: C04B 37/026 : consisting of metals or metal salts
• CPC Class Codes: H01L 2224/05599 : Material
• CPC Class Codes: H01L 2224/32014 : the layer connector being smaller than the bonding area, e.g. bond pad
• CPC Class Codes: H01L 2224/32225 : the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45099 : Material
• CPC Class Codes: H01L 2224/48091 : Arched
• CPC Class Codes: H01L 2224/48227 : connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48472 : the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
• CPC Class Codes: H01L 2224/49113 : the connectors connecting different bonding areas on the semiconductor or solid-state body to a common bonding area outside the body, e.g. converging wires
• CPC Class Codes: H01L 2224/73265 : Layer and wire connectors
• CPC Class Codes: H01L 23/3735 : Laminates or multilayers, e.g. direct bond copper ceramic substrates
• CPC Class Codes: H01L 24/48 : of an individual wire connector
• CPC Class Codes: H01L 24/49 : of a plurality of wire connectors
• CPC Class Codes: H01L 24/73 : Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 : Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01012 : Magnesium [Mg]
• CPC Class Codes: H01L 2924/01019 : Potassium [K]
• CPC Class Codes: H01L 2924/0102 : Calcium [Ca]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01057 : Lanthanum [La]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H05K 1/0306 : Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 3/38 : Improvement of the adhesion between the insulating substrate and the metal
• CPC Class Codes: Y10T 428/12458 : having composition, density, or hardness gradient
• CPC Class Codes: Y10T 428/12479 : Porous [e.g., foamed, spongy, cracked, etc.]
• CPC Class Codes: Y10T 428/12528 : Semiconductor component
• CPC Class Codes: Y10T 428/1284 : W-base component

Abstract

A composite substrate 30 is constituted by an alumina substrate 16, a metallic layer 34, and a copper sheet 26 bonded to the alumina substrate 16 via the metallic layer 34. The metallic layer 34 is constituted by a tungsten sub-layer 34a having a low coefficient of thermal expansion, a tungsten/silver-copper alloy mixture sub-layer 34b, and a silver-copper alloy sub-layer 34c having a high coefficient of thermal expansion. In the mixture sub-layer 34b, the ratio of the percentage content of the silver-copper alloy to that of the tungsten increases with distances from the alumina substrate 16.

Claims

1. A ceramic-metal composite structure comprising:

a sintered ceramic body;

a metallic layer bonded to a surface of at least a portion of said sintered ceramic body,

said metallic layer being formed of a metal having a high melting point such that porosity of said metallic layer continuously or stepwise increases with distances from said surface of said sintered ceramic body, said metallic layer having pores in which copper or a silver/copper-based alloy is contained, so that a ratio of a percentage content of said copper or said silver/copper-based alloy to a percentage content of the high-melting-point metal substantially continuously or stepwise increases with said distances from said surface of said sintered ceramic body; and

a nickel layer provided at an interface of said high-melting-point metal and said copper or said silver/copper-based alloy in said metallic layer.

11. The composite structure as set forth in claim 1, wherein said metallic body is formed of one selected from copper, copper alloys, copper-plated metals, copper-cladded metals, and nickel.

2. A process of producing a ceramic-metal composite structure, comprising the steps of:

a metalizing step of forming, on a surface of at least a portion of a ceramic body, a porous metallic layer using a high-melting-point metal such that porosity of said metallic layer continuously or stepwise increases with distances from said surface of said ceramic body, said metallic layer having a multiplicity of pores including externally open pores,

a forming step of forming a nickel layer on internal surfaces of said metallic layer which define the multiple pores including the externally open pores in said metallic layer, and

an impregnating step of impregnating copper or a silver/copper-based alloy in said multiple pores of said metallic layer through the externally open pores.

3. A ceramic-metal composite structure comprising:

a sintered ceramic body;

a first metallic layer which is formed of a metal having a high melting point such that porosity of said first metallic layer continuously or stepwise increases with distances from a first one of opposite surfaces of said sintered ceramic body, said first metallic layer having pores in which copper or a silver/copper-based alloy is contained, so that a ratio of a percentage content of said copper or said silver/copper-based alloy to a percentage content of the high-melting-point metal substantially continuously or stepwise increases with said distances from said first surface of said sintered ceramic body;

a second metallic layer which is formed of said high-melting-point metal such that porosity of said second metallic layer continuously or stepwise increases with distances from a second one of opposite surfaces of said sintered ceramic body, said second metallic layer having pores in which said copper or said silver/copper-based alloy is contained, so that a ratio of a percentage content of said copper or said silver/copper-based alloy to a percentage content of the high-melting-point metal substantially continuously or stepwise increases with said distances from said second surface of said sintered ceramic body;

a first metallic body bonded to said first surface of said sintered ceramic body via said first metallic layer; and

a second metallic body bonded to said second surface of said sintered ceramic body via said second metallic layer.

4. The composite structure as set forth in claim 3, wherein said high-melting-point metal is tungsten or molybdenum.

5. The composite structure as set forth in claim 3, wherein said sintered ceramic body provides a substrate for said first and second metallic bodies selected from the group consisting of a copper sheet or a copper-alloy sheet.

6. The composite structure as set forth in claim 3, wherein said sintered ceramic body is constituted by a sintered alumina body or a sintered aluminum nitride body.

7. A ceramic-metal composite structure comprising:

a sintered ceramic body;

a metallic layer;

a metallic body bonded via the metallic layer to a surface of at least a portion of the sintered ceramic body;

said metallic layer being formed of a metal having a high melting point such that porosity of said metallic layer continuously or stepwise increases with distances from said surface of said sintered ceramic body, said metallic layer having pores in which copper or a silver/copper-based alloy is contained, so that a ratio of a percentage content of said copper or said silver/copper-based alloy to a percentage content of the high-melting-point metal substantially continuously or stepwise increases with said distances from said surface of said sintered ceramic body;

said sintered ceramic body providing a substrate for said metallic body selected from the group consisting of a copper sheet or a copper-alloy sheet; and

a circuit pattern as at least a portion of said metallic body.

8. The composite structure as set forth in claim 7, further comprising a layer of said copper or said silver/copper-based alloy provided on a surface of said metallic layer.

9. The composite structure as set forth in claim 7, wherein said metallic layer comprises, adjacent to said sintered ceramic body, a lowermost sub-layer consisting essentially of said high-melting-point metal.

10. The composite structure as set forth in claim 7, wherein said metallic layer is formed of a composition containing, in addition to said high-melting-point metal, at least one of one or more constituents of said sintered ceramic body, said composition containing up to 30% by weight of said one constituent of said sintered ceramic body.

12. The composite structure as set forth in claim 7, further comprising a semiconductor chip bonded to at least a portion of said metallic body, for providing a power semiconductor module.

13. The composite structure as set forth in claim 12, further comprising, in addition to said metallic layer as a first metallic layer, a second metallic layer identical with said first metallic layer;

in addition to said metallic body as a first metallic body to which said semiconductor chip is bonded, a second metallic body bonded to said sintered ceramic body such that said first and second metallic bodies are bonded to opposite surfaces of said sintered ceramic body via said first and second metallic layers, respectively; and

a heat sink bonded to said second metallic body.

14. A process of producing a ceramic-metal composite structure including a sintered ceramic body, a metallic layer, and a metallic body bonded via the metallic layer to a surface of at least a portion of the sintered ceramic body, the process comprising the steps of:

a metalizing step of forming, on a surface of at least a portion of a ceramic body, a porous metallic layer using a high-melting-point metal such that porosity of said metallic layer continuously or stepwise increases with distances from said surface of said ceramic body, said metallic layer having a multiplicity of pores including externally open pores,

a step of forming a nickel layer on internal surfaces of said metallic layer which define said multiple pores including said externally open pores,

an impregnating step of impregnating copper or a silver/copper-based alloy in the multiple pores of said metallic layer through the externally open pores, and

a bonding step of bonding the metallic body to the ceramic body via the metallic layer.

15. The process as set forth in claim 14, wherein said metalizing step comprises

a laminating step of laminating at least two metallic sub-layers on a surface of a formed ceramic body or a ceramic body, by printing using at least two kinds of metal-based pastes each of which contains as an essential constituent thereof said high-melting-point metal and which have different porosities after being sintered, in an order that a paste having a lower porosity after being sintered is printed before a paste having a higher porosity after being sintered;

and

a sintering step of firing, after said laminating step, the laminated metallic sub-layers and said formed or ceramic body under prescribed conditions.

16. The process as set forth in claim 14, wherein said metalizing step comprises

a laminating step of laminating at least two metallic sub-layers on a surface of a formed ceramic body or a ceramic body, by superposing at least two green sheets each of which contains as an essential constituent thereof said high-melting-point metal and which have different porosities after being sintered, in an order that a paste having a lower porosity after being sintered is printed before a paste having a higher porosity after being sintered, and subsequently compressing the laminated metallic sub-layers;

and

a sintering step of firing, after said laminating step, said laminated metallic sub-layers and said formed or ceramic body under prescribed conditions.

17. The process as set forth in claim 14, wherein said impregnating step comprises

a step of forming a layer of said copper or said silver/copper-based alloy on a surface of said metallic layer opposite to the surface thereof bonded to said ceramic body;

and

a step of heating the layer of said copper or said silver/copper alloy on said metallic layer under prescribed conditions.

18. The process as set forth in claim 17, wherein said step of forming the layer of said copper or said silver/copper-based alloy comprises a step of placing a foil of said copper or said silver/copper-based alloy on the surface of said metallic layer opposite to the surface thereof bonded to said ceramic body.

19. A process of producing a ceramic-metal composite structure including a ceramic body, a metallic layer, and a metallic body bonded via the metallic layer to a surface of at least a portion of the ceramic body, the process comprising the steps of:

a metalizing step of forming, on a surface of at least a portion of a ceramic body, a porous metallic layer using a high-melting-point metal such that porosity of said metallic layer continuously or stepwise increases with distances from said surface of said ceramic body, said metallic layer having a multiplicity of pores including externally open pores,

an impregnating step of impregnating copper or a silver/copper-based alloy in the multiple pores of said metallic layer through the externally open pores, and

a bonding step of bonding the metallic body to the ceramic body via the metallic layer,

wherein said impregnating step comprises

a step of forming a layer of said copper or said silver/copper-based alloy, by printing using a paste of said copper or said silver/copper-based alloy, on a surface of said metallic layer opposite to the surface thereof bonded to said ceramic body, and

a step of heating the layer of said copper or said silver/copper-based alloy on said metallic layer under prescribed conditions.

20. A process of producing a ceramic-metal composite structure including a ceramic body, a metallic layer, and a metallic body bonded via the metallic layer to a surface of at least a portion of the ceramic body, the process comprising the steps of:

a metalizing step of forming, on a surface of at least a portion of a ceramic body, a porous metallic layer using a high-melting-point metal such that porosity of said metallic layer continuously or stepwise increases with distances from said surface of said ceramic body, said metallic layer having a multiplicity of pores including externally open pores,

an impregnating step of impregnating copper or a silver/copper-based alloy in the multiple pores of said metallic layer through the externally open pores, and

a bonding step of bonding the metallic body to the ceramic body via the metallic layer,

wherein said impregnating and bonding steps comprise

a step of forming a layer of said copper or said silver/copper-based alloy on a surface of said metallic layer opposite to the surface thereof bonded to said ceramic body,

a step of placing said metallic body in contact with a surface of the layer of said copper or said silver/copper-based alloy opposite to the surface thereof in contact with said metallic layer, and

a step of heating, under prescribed conditions, the layer of said copper or said silver/copper-based alloy in contact with said metallic body and said metallic layer.