JP2015012187A - Connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection structure for electric and electronic parts and various mechanical parts and others which can improve the life of joining by suppressing the occurrence of crack and delamination or the like and consequently increase the connection reliability.SOLUTION: A connection structure comprises: an object to be connected 3; a porous metal layer 8; and an object 7 to be connected. In the connection structure, the object 7 is connected onto the object 3 through the porous metal layer 8. The porous metal layer 8 has a porosity of 2-25 vol.%. In the porous metal layer 8, the ratio (V/H) of the average Feret vertical diameter (V) of pores of the porous metal layer 8 to the average Feret horizontal diameter (H) of the pores is from over 1 up to 1.5; and the average pore diameter is 30-600 nm.

Description

  The present invention relates to a connection structure for electrical / electronic components, various mechanical components, etc., in which a connected body such as a substrate or a lead frame and the other connected body such as a semiconductor element are joined via a porous metal layer. About the body.

  In general, a semiconductor device includes a step of forming a die mount material for joining a semiconductor element (chip) on an element carrying portion of a lead frame, and a semiconductor device having a semiconductor element mounted on the surface of the die mount material on the lead frame. A step of bonding the element carrying portion and the semiconductor element, a wire bonding step of electrically bonding the electrode portion of the semiconductor element and the terminal portion of the lead frame, and coating the semiconductor device thus assembled with resin It is manufactured through a molding process.

In Patent Document 1, a low melting point solder layer having a lower melting point than the melting point of the solder material is formed on at least one of the joining surfaces of the material to be joined and the solder material, and the low melting point solder layer A soldering method is disclosed in which the joining surfaces of the material to be joined and the solder material are joined to each other at a temperature within a range from the melting point of the solder material to the melting point of the solder material.
On the other hand, as the conductive resin paste, a paste in which metal particles such as silver and gold and a resin are mixed is used. In recent years, silver paste has been most widely used.

  In Patent Document 2, a lead frame having a metal layer on the front surface and a semiconductor element having a metal layer on the back surface are joined via a joining layer composed of three layers using a material not containing lead element, It is disclosed that metal bonding is performed at any adjacent interface of the semiconductor element and the bonding layer. Patent Document 3 contains metal powder, endothermic decomposable metal compound, and solvent for bonding to each other through exothermic densifiable metal paste to bond two structural elements. A metal paste is disclosed.

However, in the soldering method disclosed in Patent Document 1, when Pb-free solder is used, the ductility of the solder tends to be insufficient, and the bonding between the constituent material of the semiconductor element and the circuit wiring board mounted on the semiconductor element If the constituent materials are different, a stress strain is generated at the time of joining due to a difference in thermal expansion coefficient, or a defect is generated when an impact load is applied. This stress strain destroys the solder electrode and reduces the reliability life. As a means for solving such a problem, a porous body formed by firing a conductive paste containing metal fine particles is known.
In joining by sintering metal paste containing metal fine particles disclosed in Patent Documents 2 and 3, the problems of lead-free, heat resistance and thermal conductivity can be solved, but by making porous, the elastic modulus becomes low, Breakage due to connection stress can be prevented because it becomes easy to deform, but the voids may be the starting point of cracks, and cracks and peeling will expand in an environment where thermal stress is repeatedly applied due to heat generation of the semiconductor In some cases, however, problems may occur during long-term use.

JP 7-169908 A JP 2006-59904 A JP 2010-53449 A

  An object of the present invention is to provide a connection structure in which the opposite body to be connected such as a substrate and a lead frame and the other body to be connected such as a semiconductor element are joined via a porous metal layer. Alleviates stress generated at the joint surface between the connection body and the porous metal layer, or at the joint surface edge between the porous metal layer and one or both of the connected bodies, and suppresses the occurrence of cracks and peeling. It is an object of the present invention to provide a connection structure such as an electric / electronic component and various mechanical components that can improve the connection reliability by improving the bonding life.

  In the connection structure in which the one connected body and the other connected body are joined via a porous porous metal layer, the present inventors have provided pores in the porous porous metal layer. And a specific range in which the ratio (V / H) of the average value (V) of the hole ferret vertical diameter and the average value (H) of the hole ferret horizontal diameter is more than 1 As a result, the present inventors have found that the above problems can be solved, and have completed the present invention.

That is, the gist of the present invention is the invention described in the following (1) to (5).
(1) A connection structure in which a body to be connected (C) is joined to a body to be connected (B) via a porous metal layer (A),
The porosity of the porous metal layer (A) is 2 to 25% by volume,
The ratio (V / H) of the average value (V) of the pore ferret vertical diameter of the porous metal layer (A) and the average value (H) of the horizontal diameter of the pore ferret (V / H) is more than 1 and 1.5 or less. A connection structure having a pore diameter of 30 to 600 nm.
(2) Ratio (V / H) of average value (V) of pore ferret vertical diameter (V) and average value (H) of pore ferret horizontal diameter of porous metal layer (A) is 1.05-1.30. The connection structure according to (1) above, wherein

(3) The porous metal layer (A) is formed of one or more selected from gold, silver, copper, aluminum, chromium, nickel, titanium, cobalt, and indium. The connection structure according to (1) or (2).
(4) One type in which the joint portions of the body to be connected (B) and the body to be connected (C) with the porous metal layer (A) are each selected from gold, silver, copper, chromium, nickel, and titanium, Or the surface of the body to be connected (B) and the body to be connected (C) on the porous metal layer (A) side is surface-treated with these metals or alloys. The connection structure according to any one of (1) to (3).
(5) The heat-resistant resin (R) is filled in at least a part of the pores formed in the porous porous metal layer (A). (1) to (4) The connection structure according to any one of the above.

  In the connecting structure according to the present invention, the porous body having the total pore vertical diameter of the holes higher than the total horizontal diameter of the holes is higher than that of the opposite connected body (B) and the connected body (C). By joining with a metal layer (A), the joining interface edge part between a to-be-connected body (B) and a porous porous metal layer (A), and a porous porous metal layer (A) and a to-be-joined body (C ) Can be improved by reducing the stress generated at the end of the bonding interface, and it is possible to improve the bonding reliability by maintaining the heat dissipation and conductivity.

It is a conceptual diagram which shows the cross section of the sintering furnace used in Examples 1-9 and Comparative Examples 1-6. It is sectional drawing which shows typically the semiconductor device which concerns on 2nd Embodiment. It is explanatory drawing which illustrates typically the method to manufacture the semiconductor device which concerns on 2nd Embodiment. It is explanatory drawing which illustrates typically the method to manufacture the semiconductor device which concerns on 2nd Embodiment.

The [1] connection structure, which is the first embodiment of the present invention, and the [2] semiconductor device of the second embodiment, which is an application invention of the first embodiment, will be described below.
[1] Connection structure (first embodiment)
Hereinafter, a connection structure and a manufacturing method thereof according to the first embodiment of the present invention will be described.
[1-1] Connection Structure The connection structure of the present invention is a connection structure in which the connection target (C) is joined to the connection target (B) via the porous metal layer (A). And
The porosity of the porous metal layer (A) is 2 to 25% by volume,
The ratio (V / H) of the average value (V) of the pore ferret vertical diameter of the porous metal layer (A) and the average value (H) of the horizontal diameter of the pore ferret (V / H) is more than 1 and 1.5 or less. The pore diameter is 30 to 600 nm.

Hereinafter, (1) the connected body, (2) the porous metal layer (A), and (3) the connecting structure constituting the connection structure of the present invention will be described.
(1) Connected body (B), (C)
The connection structure of the present invention is a connection structure in which the body to be connected (B) and the body to be connected (C) are joined via the porous metal layer (A), and its use is particularly limited. Rather, it can be widely used for electrical / electronic parts and in-vehicle machine parts. In the case of in-vehicle mechanical parts, it can be suitably used particularly for a connection structure in which connected bodies used for heat generating parts such as engine parts are joined by a porous metal layer (A).
When the connection structure of the present invention is an electric / electronic component, for example, as described below, one connected body (B) is a substrate and the other connected body (C) is a semiconductor. It can be set as an element.

(I) Substrate (K) used for a substrate semiconductor device is formed by bonding a conductive pattern such as a copper plate on one surface of an insulating layer such as ceramics by plating, sputtering, or brazing material, ceramic A DBC (Direct Bonded Copper) substrate or the like in which an electrode plate is directly bonded to the substrate can be suitably used. A copper plate can be joined to the other surface for the purpose of heat dissipation or the like. Further, a metal plate can be bonded to the other surface of the substrate (K) for the purpose of heat dissipation or the like. Examples of the ceramic include alumina (Al ₂ O ₃ ), aluminum nitride (AlN), and silicon nitride (Si ₃ N ₄ ). In the present invention, a lead frame (L) can be used in addition to the substrate (K). When the semiconductor element (S) is mounted on the lead frame (L), it can be expected that heat dissipation is improved.

(Ii) Semiconductor element (S)
The semiconductor element (S) is a semiconductor electronic component or an element at the functional center of the electronic component. For example, a semiconductor wafer and a substrate (K) having an external connection electrode are bonded to each other and cut into chips ( (Dicing). The semiconductor element (S) is usually provided with a metal layer such as an alloy on the joint surface with the electrode or the like.

(2) Porous metal layer (A)
The porous metal layer (A) has a porosity of 2 to 25% by volume. The average value (V) of the pore ferret vertical diameter of the porous metal layer (A) and the average value of the horizontal diameter of the pore ferret ( The ratio (V / H) of H) is more than 1 and 1.5 or less, and the average pore diameter is 30 to 600 nm.
In the connection structure of the present invention, the opposite connected body (B) and the connected body (C) have the porosity and the average pore diameter in the specific ranges, and the average value of the ferret vertical diameter of the pores is By joining with a porous porous metal layer (A) that exceeds the average value of the ferret horizontal diameter of the pores, the joining interface end between the connected body (B) and the porous porous metal layer (A), and The stress generated at the joint interface edge between the porous metal layer (A) and the joined body (C) is relaxed, so that the joint life can be improved, and heat dissipation and conductivity are maintained. Thus, the bonding reliability can be improved.

(2-1) Porosity of Porous Porous Metal Layer (A), Method for Measuring Pore Ferret Horizontal Diameter / Vertical Diameter, Average Pore Diameter (i) Porosity of Porous Porous Metal Layer (A) , Measurement of average pore diameter, thickness of porous porous metal layer (A), and measurement of porosity of porous porous metal layer (A), the porous porous metal layer (A) is epoxy resin The cross section was polished and exposed, and observed with a scanning electron microscope.
The average pore diameter was determined by measuring the elliptical long axis diameter and the elliptical short axis diameter of all the pores using a soft tool, and obtaining the average value of the elliptical long axis diameters as the average pore diameter.

(Ii) Porous ferret horizontal diameter and vertical diameter of porous porous metal layer (A) The vertical and horizontal diameter of porous ferret of porous porous metal layer (A) is the vertical direction of the porous porous metal layer. The cut surface is observed with a scanning electron microscope (SEM, 5000 times), and the center side portion excluding the end portion is observed, binarized so that the metal portion in the SEM image appears white, and within the selected range (vertical The ferret horizontal diameter and fillet vertical diameter of all pores (10 μm × 20 μm wide) were measured using a soft tool, and the average of the fillet horizontal diameter and the average of the ferret vertical diameter were determined.

(2-2) Porosity The porosity in the porous metal layer (A) is 2 to 25% by volume.
When the porosity is 2% or more, the semiconductor element (S), the bonding interface between the semiconductor element (S) and the porous metal layer (A), and between the porous metal layer (C) and the substrate (P). It is preferable because the function of relaxing the stress concentration generated at the bonding interface is effectively exhibited. On the other hand, when the porosity is 25% or less, the necessary mechanical strength of the porous metal layer (A) is secured, Material destruction in the porous metal layer (A) can be suppressed. From this viewpoint, the porosity is preferably 10 to 20% by volume.

(2-3) Ratio (V / H) of average value (V) of vertical diameter of hole ferret and average value (H) of horizontal diameter
The ratio (V / H) of the average value (V) of the pore ferret vertical diameter of the porous metal layer (A) and the average value (H) of the horizontal diameter of the pore ferret is more than 1, preferably 1.5 or less. Is 1.05-1.30.
In the connection structure (A) of the present invention, the opposite connected body (B) and the connected body (C) are obtained by comparing the average value (V) of the ferret vertical diameter of the holes and the average value (H) of the horizontal diameter. By joining with the porous metal layer (A) having a ratio (V / H) of more than 1, the joined interface edge between the connected body (A) and the porous metal layer (A), and the porous metal layer ( The stress generated at the end of the interface between A) and the body to be bonded (C) is relieved, the bonding life can be improved, and the heat radiation and conductivity can be maintained and the bonding reliability can be improved. it can. On the other hand, by setting the ratio (V / H) to 1.5 or less, it is possible to suppress the generation of voids (defects) having a pore diameter of 10 μm or more in the porous metal layer (A) and improve the mechanical strength. become.

(2-4) Average pore diameter of the porous metal layer (A) The average pore diameter of the bonding layer (L) is 30 to 600 nm. When the average hole diameter is 30 nm or more, the connection reliability can be improved. On the other hand, when the average hole diameter is 600 nm or less, the occurrence of peeling is suppressed, the connection reliability is improved, and the decrease in thermal conductivity can be suppressed. From this viewpoint, the average pore diameter is preferably 50 to 500 nm.
(2-5) Thickness of porous metal layer (A) The thickness of the porous metal layer (A) is preferably 5 to 500 µm. When the thickness is less than 5 μm, when a component (power device) that generates a large amount of heat is mounted on the conductive metal plate (K), the thermal resistance when transferring the heat generated from the component to the lower metal plate is reduced, but the connection is reduced. Reliability may be reduced. On the other hand, if the thickness exceeds 500 μm, there is a risk that the thermal resistance increases.

(3) Heat bonding material (F)
As will be described later, the porous metal layer (A) is a heat bonding material (F) containing at least metal fine particles (M) and an organic dispersion medium (D) on a body to be connected (B) made of a metal layer. ) Is patterned or arranged, and the connected body (C) is further arranged on the heat bonding material (F), and then the heat bonding material (F) is heated and sintered.
The heat bonding material (F) is preferably 100 Pa · s or less, in which the metal fine particles (M) including the metal fine particles (M1) are dispersed in the organic dispersion medium (D) and have a relatively high viscosity.
The heat bonding material (F), which is a conductive metal paste, is supplied by, for example, a printing process, and considering the printing workability, the viscosity is preferably 100 Pa · s or less. When the viscosity is 100 Pa · s or more, there is a possibility that a print mark may be formed on the surface of the heat-bonding material after printing, or air may be trapped inside to cause void formation. The viscosity can be measured with a vibration viscometer according to JIS Z8803 (2011). Examples of the vibration viscometer include Seikonic Co., Ltd., vibration viscometer, model: VM100A.

For a heat-bonding material that has a viscosity of 100 Pa · s or less and requires a pressure during sintering, for example, when a pressure heating process is performed using a press after printing, the heat connecting material flows around the outer periphery of the connected body. Therefore, it is difficult to secure a desired connection thickness. Therefore, it is preferable that the heat-bonding material (F) having a low viscosity is preliminarily dried to remove the solvent and reduce the fluidity.
It is a dispersion material having a viscosity of 200 Pa · s or more. In order to maintain the viscosity of the heat-bonding material (F) at 200 Pa · s or more, 70 to 90% by mass of the metal fine particles (M) and 30 to 10% by mass (total of the mass%) of the organic dispersion medium (D) Is preferably 100% by mass, the same applies hereinafter), more preferably 75 to 85% by mass of the metal fine particles (M) and 25 to 15% by mass of the organic dispersion medium (D).

(B) Metal fine particles (M)
Unlike the case of the solder paste, the metal fine particles (M) used for forming the porous metal layer (A) can use at least one kind of high-purity metal fine particles as they are. An excellent joined body can be obtained. In general, in the case of a solder paste, it contains a flux (organic component) in order to remove the oxidation of the copper pad portion of the substrate to be mounted, and further, Al, Zn, Cd, Although metals such as As are often included, in the present invention, the influence of these organic components and impurities can be avoided.
As described later, the porous metal layer (A) may be obtained by sintering metal fine particles (M1) having an average particle diameter of 1 to 500 nm of primary particles dispersed in the organic dispersion medium (D). Also, a mixture of the metal fine particles (M1) dispersed in the organic dispersion medium (D) and metal fine particles (M2) having an average primary particle size of 0.5 to 50 μm may be sintered. Good.

The metal fine particles (M) are fine particles having high conductivity and thermal conductivity and having sinterability. From the viewpoint of conductivity, heat treatment (sinterability), availability on the market, etc., for example, gold, silver, Examples include copper, platinum, palladium, tungsten, nickel, iron, cobalt, tantalum, bismuth, lead, indium, tin, zinc, titanium, or aluminum. Among these, copper, gold, silver, nickel, and cobalt are included. Among these, copper is particularly preferable from the viewpoints of conductivity, thermal conductivity, workability, prevention of migration, cost reduction, and the like.
The metal fine particles (M) are fine particles having high conductivity and thermal conductivity and having sinterability, and those having an average primary particle size of nano-size (referring to particles having a size of less than 1 μm) are preferable. Specifically, metal fine particles (M1) having an average primary particle diameter of 1 to 500 nm are preferable. When the average particle size of the primary particles of the metal fine particles (M1) is 1 nm or more, it becomes possible to form a porous body having a uniform particle size and pores by firing, while forming a precise conductive pattern at 500 nm or less. can do.

When the metal fine particles (M2) having an average primary particle diameter of 0.5 to 50 μm are used in combination with the metal fine particles (M1) having an average primary particle diameter of 1 to 500 nm as the metal fine particles (M), Since the metal fine particles (M1) are dispersed and stably present in the metal particles, a difference in particle diameter from the average primary particle diameter of the metal fine particles (M1) can be secured, and the metal fine particles (M1) can be freely dispersed during the heat treatment. The movement can be effectively suppressed, and the dispersibility and stability of the metal fine particles (M1) can be improved. When the metal fine particles (M2) are mixed and used in the metal fine particles (M), the metal fine particles (M1) in the metal fine particles (M) are 80 to 95 volume%, and the metal fine particles (M2) are 20 to 5 volumes. % (Total of volume% is 100 volume%). As the metal fine particles (M2), it is preferable to use the same kind of metal particles as described in the metal fine particles (M1).
Here, the average particle diameter of the primary particles means the diameter of the primary particles of the individual metal fine particles constituting the secondary particles. The primary particle diameter is a measured value that can be measured from an image obtained using an electron microscope. The average particle diameter means the number average particle diameter of primary particles that can be observed using an electron microscope.

(B) Organic dispersion medium (D)
The organic dispersion medium (D) preferably contains one or more polyols having two or more hydroxyl groups in the molecule, and the melting point of the polyol is more preferably 30 to 280 ° C. preferable. Polyol has the effect of promoting the sintering by dispersing the metal fine particles (M) in the heat bonding material (F) and generating a hydrogen radical by receiving a dehydrogenation reaction during heating and sintering. To do.
Examples of such polyols include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2-butene. -1,4-diol, 2,3-butanediol, pentanediol, hexanediol, octanediol, glycerol, 1,1,1-trishydroxymethylethane, 2-ethyl-2-hydroxymethyl-1,3-propane Diol, 1,2,6-hexanetriol, 1,2,3-hexanetriol, 1,2,4-butanetriol, threitol, erythritol, pentaerythritol, pentitol, xylitol, ribitol, arabitol, hexitol, mannitol, Sorbitol, Zulu Toll, glyceraldehyde, dioxyacetone, threose, erythrulose, erythrose, arabinose, ribose, ribulose, xylose, xylulose, lyxose, glucose, fructose, mannose, idose, sorbose, gulose, talose, tagatose, galactose, allose, altrose , Lactose, xylose, arabinose, isomaltose, glucoheptose, heptose, maltotriose, lactulose, and trehalose.
As a component of the organic dispersion medium (D), an alcohol, an organic solvent having an amide group, an ether compound, a ketone compound, an amine compound, and the like can be blended in addition to the polyol. It is preferable to mix | blend dispersion media other than these polyols in an organic dispersion medium (D) so that it may become 30 volume% or less collectively.

(C) Organic binder After the organic binder is applied to the joined body (B), the aggregation of the metal fine particles (M) is suppressed in the heat bonding material (F), the viscosity of the heat bonding material (F) is adjusted, Demonstrate the function of maintaining the shape. The organic binder is selected from cellulose resin binder, acetate resin binder, acrylic resin binder, urethane resin binder, polyvinyl pyrrolidone resin binder, polyamide resin binder, butyral resin binder, and terpene binder. One type or two or more types are preferred. The organic dispersion medium (D) is preferably composed of the organic solvent (S) alone or the organic solvent (S) 80 to 100% by mass and the organic binder 20 to 0% by mass (the total of the mass% is 100% by mass). . When the blending ratio of the organic binder in the organic dispersion medium (D) exceeds 20% by mass, the rate at which the organic binder thermally decomposes and scatters when the conductive connection member precursor is heat-treated becomes low, and the conductive connection If the amount of residual carbon in the member increases, sintering is hindered, which may cause problems such as cracking and peeling.

(D) Organic dispersant The organic dispersant has an action of dispersing the metal fine particles (M) in the heat bonding material (F). A water-soluble polymer compound can be used as the organic dispersant. As such a water-soluble polymer compound, an amine polymer such as polyethyleneimine or polyvinylpyrrolidone; a carboxyl such as polyacrylic acid or carboxymethylcellulose can be used. Examples include hydrocarbon polymers having acid groups; acrylamides such as polyacrylamide; polyvinyl alcohol, polyethylene oxide, and starch and gelatin.
The concentration of the organic dispersant in the reduction reaction aqueous solution is preferably 0.01 to 30 in terms of the mass ratio of the organic dispersant to copper atoms and zinc atoms (organic dispersant / (metal fine particles (M))). 5-10 are more preferable. When the ratio is less than 0.01, the reduction reaction is remarkably slow, and when it exceeds 30, the effect of addition may be lost.

[1-2] Manufacturing Method of Connection Structure In the connection structure of the present invention, for example, a heating bonding material (F) such as a substrate is applied (or patterned) or disposed on the connection target (B), and further, After placing the connected body (C) such as the semiconductor element (S) on the heat bonding material (F), the heat bonding material (F) is heated and sintered to form the porous metal layer (A), The connected body (B) and the connected body (C) are formed by joining via the porous metal layer (A).
In this case, for example, by selecting the following conditions (1) to (3),
In the porous metal layer (A), the porosity is 2 to 25% by volume, the average value of the vertical diameter of the porous ferret (V) and the average value of the horizontal diameter of the porous ferret (H) It is possible to manufacture a connection structure having a ratio (V / H) of more than 1 and 1.5 or less and an average pore diameter of 30 to 600 nm.

(1) Component of Heat Bonding Material (F) As described above, the porous metal layer (A) is a metal fine particle (M1) having an average primary particle size of 1 to 500 nm dispersed in the organic dispersion medium (D). ), Or the metal fine particles (M1) dispersed in the organic dispersion medium (D) and the metal fine particles (M2) having an average primary particle size of 0.5 to 50 μm. A mixture of these may be sintered.
The organic dispersion medium (D) preferably contains one or more polyols having two or more hydroxyl groups in the molecule, and the melting point of the polyol is more preferably 30 to 280 ° C. preferable. As described above, the blending ratio of the metal fine particles (M) and the organic dispersion medium (D) in the heat bonding material (F) is adjusted so that the viscosity is 100 Pa · s or less and can be applied or printed. .
(2) Viscosity of heat-bonding material (F) The heat-bonding material (F) has a relatively high viscosity, in which metal fine particles (M) including metal fine particles (M1) are dispersed in an organic dispersion medium (D), 100 Pa · S or less is preferable.

(3) Firing conditions of the heat bonding material (F) (a) When sintering the heat bonding material (F), pressurizing condition heat bonding material (F) from above the connected body (C) It is preferable to sinter under pressure of 5 to 20 MPa from the upper side of C).
The pressure condition is 5 MPa or more, and the ratio (V / H) of the average value (V) of the pore ferret vertical diameter of the porous metal layer (A) to the average value (H) of the horizontal diameter of the ferret ferret is more than 1. On the other hand, if it exceeds 20 MPa, the semiconductor element may be damaged. The sintering apparatus shown in FIG. 1 was used. Using this apparatus, the porous metal layer precursor was sintered by the following operation to form a porous metal layer.
A press plate 42 for layup shown in FIG. 1A is prepared, and the work 41 is laid up on the press plate 42 and set on the lower heating plate 44 of the vacuum press machine 43. Thereafter, as shown in FIG. 1B, the chamber 45 is closed and the inside of the chamber 45 is evacuated. Then, as shown in FIG. 1 (c), the workpiece 41 is sandwiched between the upper heating plate 47 and the lower heating plate 44 with the pressure applied by the pressure cylinder 46 and heated. By the heating and firing, the porous metal layer precursor is sintered to form the porous metal layer (A).

(B) Heating conditions It is preferable that the heat-bonding material (F) is fired at a constant temperature after being heated at a rate of 5 to 20 ° C./min. By setting the heating rate within the above range, the porosity in the porous metal layer (A) is 2 to 25% by volume, the average pore diameter is 30 to 600 nm, and the average value of the pore ferret vertical diameter (V ) And the average value (H) of the hole ferret horizontal diameter (V / H) can be manufactured to be more than 1 and 1.5 or less.

(4) Filling at least a part of the porous metal layer (A) with a heat-resistant resin (R) When forming the porous metal layer (A) of the present invention, the heat-bonding material (F) is further heat-resistant. When the heat-resistant resin (R) is baked together with the organic dispersion medium (D) when it is baked under heating from the upper side of the connected body (C) by blending the conductive resin (R), At least a part of the outer peripheral side surface of the porous metal layer (A) and / or the body to be connected (C) is covered with a coating layer made of a heat resistant resin (R), and the side surface of the body to be connected (C). Therefore, it is possible to prevent the metal fine particles and the like from adhering and to obtain a semiconductor device with good characteristics.
Examples of the component forming such a heat resistant resin (R) include a prepolymer solution and a resin solution. Examples of the components of the prepolymer solution include an epoxy resin system having two or more epoxy groups in one molecule, a polyimide prepolymer solution, and the like. Examples of the resin solution include resins such as silicon resin, amideimide resin, maleimide resin, and polyvinylpyrrolidone. The heat-resistant resin (R) preferably has a deflection temperature under load of 150 ° C. or higher and a glass transition temperature (Tg) of 100 ° C. or higher.

[2] Semiconductor device (second embodiment)
Hereinafter, a semiconductor device and a method for manufacturing the semiconductor device according to the second embodiment using the first embodiment of the present invention will be described.
[2-1] Semiconductor Device A semiconductor device according to the second embodiment will be described below.
A ceramic substrate;
A metal circuit layer formed on one side of the ceramic substrate;
A sintered body layer formed on the metal circuit layer and made of a sintered body of metal particles;
A conductor layer formed on the sintered body layer and having a surface area opposite to the metal circuit layer smaller than the metal circuit layer;
A semiconductor device comprising: a semiconductor element bonded to the conductor layer through a die bond bonding layer.

The semiconductor device is
“Ceramics substrates,
A metal circuit layer formed on one side of the ceramic substrate;
A sintered body layer formed on the metal circuit layer and made of a sintered body of metal particles;
An electronic circuit board having a conductor layer formed on the sintered body layer and having a surface area opposite to the metal circuit layer that is smaller than the metal circuit layer ”is further interposed via a die bond bonding layer. The semiconductor elements are coupled.

Hereinafter, a second embodiment will be described in detail with reference to the drawings.
As shown in FIG. 2, the semiconductor device 1 according to the present embodiment includes a ceramic circuit board 2 and a metal circuit layer 3 (connected body (B of the first embodiment (B The same shall apply hereinafter) and a wiring substrate 5 provided with a metal layer 4 for heat diffusion and warpage prevention formed on the other surface of the ceramic substrate 2. On the upper surface of the metal circuit layer 3 of the wiring board 5, a sintered body layer 8 (corresponding to the connected body (B) of the first embodiment; the same applies hereinafter) made of a sintered body of metal particles is provided. On the sintered body layer 8, a conductor layer 7 (corresponding to the connected body (C) of the first embodiment; the same applies hereinafter) is provided. The area of the mutually facing surfaces of the metal circuit layer 3 and the conductor layer 7 is smaller in the conductor layer 7 than in the metal circuit layer 3. A semiconductor element 9 is bonded to the conductor layer 7 via a die bond bonding layer 6. Further, a terminal (not shown) formed on the upper surface of the semiconductor element 9 (surface not bonded to the die bond bonding layer 6) and the wiring 3 a of the wiring substrate 5 are connected by a wire 10.

Hereinafter, each component of the semiconductor device 1 according to the second embodiment will be described in detail.
(1) Wiring board 5
The wiring substrate 5 in the second embodiment is a DBC substrate in which a copper circuit board is bonded as the metal circuit layer 3 and a copper plate as the metal layer 4 is bonded to the ceramic substrate 2 by a eutectic reaction.
As the ceramic substrate 2, for example, a powder component of any of Al ₂ O ₃ , AlN, Si ₃ N ₄ , glass, two or more powder materials, or a powder material mainly composed of these, a binder component as necessary And the like, and after being formed into a sheet shape, a product prepared by firing can be used. In particular, Si ₃ N ₄ is preferably used because high strength can be expected. The substrate made of ceramics may be smoothed by polishing the surface with abrasive grains as appropriate.

The thickness of the ceramic substrate 2 can be designed as appropriate, but is preferably 100 to 1000 μm. In particular, when a heat dissipation device is provided on the surface of the wiring board 5 on the metal layer 4 side, the thermal resistance from the semiconductor element 9 to the heat dissipation device can be reduced by reducing the thickness of the ceramic substrate 2 to 100 to 300 μm. Is possible.
The thickness of the metal circuit layer 3 and the metal layer 4 is preferably 30 to 500 μm. It is particularly preferable that the thickness is 100 to 300 μm from the viewpoint of forming on a ceramic without wrinkles and the like and reducing thermal stress applied to the ceramic during use.

  In the second embodiment, a DBC substrate is used as the wiring substrate 5, but the invention is not limited to this, and as a material for the metal circuit layer 3 and the metal layer 4, in addition to Cu, Al, Ag, Au One metal selected from a group of metal elements having excellent electrical conductivity, two or more alloys, or an alloy containing one or more as a main component can be employed. In particular, Cu has a low electric resistance. Available in various thicknesses is easy and common. Moreover, Al has a low electrical resistance and is convenient for Al wire bonding. Moreover, you may use what joined the metal circuit layer 3 and the metal layer 4 on the ceramic substrate 2 through the brazing material which added active metals, such as Ti and Zr.

  Furthermore, you may use what laminated | stacked the metal circuit layer 3 and the metal layer 4 on the ceramic substrate 2 through the base layer. The underlayer is formed of a metal material, an organic material, or a material obtained by mixing a metal material and an organic material. As the metal material, Ti, Cr, Cu, Ni, Ag, and Au can be suitably used. In addition, as the organic material, materials such as polyamide, epoxy, polyimide, polyhydric alcohol and the like, and general materials obtained by imparting substitution plating property and photosensitivity thereto can be suitably used. In addition, as a material in which a metal material and an organic material are mixed, a material in which the above metal material and organic material are mixed in an arbitrary ratio can be suitably used. Furthermore, after the same material as that of the sintered body layer 8 described later is uniformly supplied to the ceramic substrate 2, it can be used as a base layer by firing or plasma treatment in an inert or reducing atmosphere. By performing the plasma treatment, the molding time can be shortened as compared with normal heating. The thickness of the underlayer can be appropriately designed, but is preferably 0.01 to 5 μm.

  Further, in the present embodiment, the ceramic substrate 2 is used as the substrate, but a substrate made of an organic material may be used instead. As the organic material, materials such as polyamide, epoxy, polyimide and the like, and general materials provided with displacement plating property and photosensitivity can be used. In addition, the material which can be used is not limited to these, If it suits the objective of this application, it can be used.

(2) Sintered body layer 8
The sintered body layer 8 is a sintered body of metal particles, and has a large number of pores therein. The void | hole here is a part in which the metal material formed in the sintered compact does not exist, and is formed of the clearance gap between metal microparticles. In the sintered body layer 8, the volume ratio of the metal material is preferably in the range of 50 to 99.999%. The pores may be filled with an organic material at an arbitrary ratio. More specifically, an organic material is filled in an arbitrary ratio with respect to one hole, and a plurality of such holes may exist in an arbitrary ratio. At this time, there may be holes that are completely filled with the organic material, and there may be holes that are not filled at all. The average maximum width of the pores is preferably 10 to 1000 nm. If the size of the pores is smaller than 10 nm, the difference in linear expansion coefficient between the ceramic substrate 2, the metal circuit layer 3, and the conductor layer 7 when the metal material constituting the sintered body layer 8 is about to expand due to heat. When stress due to the occurrence of stress occurs, the stress cannot be absorbed efficiently. If it is larger than 1000 nm, the conductivity will be low.

The metal fine particles are preferably composed mainly of one or more metals of Cu, Ag, Au, Al, Ni, Sn, In, and Ti. In particular, Cu is preferable because migration can be suppressed. Further, when the same material as the metal circuit layer 3 and the conductor layer 7 is used, it is easy to join. The metal fine particles preferably contain 50% by mass or more of particles having an average primary particle diameter of 1 nm to 500 nm and 50% by mass or less of particles having an average primary particle diameter of 0.5 μm to 50 μm.
Examples of the organic material filled in the pores include polyamides, epoxies, polyimides, polyhydric alcohols, and the like, and general materials obtained by imparting substitution plating properties and photosensitivity thereto. Further, in the state before sintering the metal fine particles, it is preferable to include a dispersing agent and a thickener in addition to the metal fine particles in order to facilitate handling. A polyhydric alcohol etc. can be used as a dispersing agent. Moreover, polyvinylpyrrolidone etc. can be used as a thickener.

The thickness of the sintered body layer 8 is preferably 5 to 500 μm. If the thickness is less than 5 μm, the crystal size of the circuit layer is large, so that the surface becomes rough and local voids may occur. If it exceeds 500 μm, the variation in supply thickness also increases, resulting in uneven connection. Moreover, it is especially preferable that it is 10-300 micrometers from a viewpoint of connecting reliably.
By providing the sintered body layer 8, when the metal material constituting the sintered body layer 8 is about to expand due to heat, or due to a difference in linear expansion coefficient between the ceramic substrate 2, the metal circuit layer 3, and the conductor layer 7. When stress is generated, the stress can be absorbed, so that the stress applied to the end of the metal circuit layer 3 is relaxed. Further, since the metal circuit layer and the conductor layer are joined by the sintered body layer, the thermal resistance is lowered and the heat dissipation is good.

(3) Conductor layer 7
The conductor layer 7 is preferably made of one type of metal selected from a metal element group consisting of Cu, Al, Ag, and Au, two or more types of alloys, or an alloy containing one or more types as a main component. It is preferable that the same material as the circuit layer is used from the viewpoint of thermal stress generated in the sintered body layer due to a difference in heat dissipation and linear expansion.
By providing the conductor layer 7, the heat capacity of the lower side of the semiconductor element 9 can be increased, so that the heat dissipation is excellent. The area of the conductor layer 7 facing the metal circuit layer 3 may be the same as the area of the metal circuit layer 3 facing the conductor layer 7, but the conductor layer 7 is opposed to the metal circuit layer 3. By making the area of the surface to be made smaller than the area of the surface of the metal circuit layer 3 facing the conductor layer 7, the end portion of the metal circuit layer 3 is connected to the sintered body layer 8 and the conductor layer 7 of the metal circuit layer 3. Since the thickness of the portion causing the difference in linear expansion coefficient with the ceramic substrate 2 is thinner than the laminated portion, the stress applied to the end of the metal circuit layer 3 due to the difference in linear expansion coefficient with the ceramic substrate 2 Is easily relaxed.

(4) Die bond bonding layer 6
As the die bond bonding layer 6, a sintered body of metal particles similar to the above-described sintered body layer 8 and having a melting point of 250 ° C. or higher after sintering can be used. In particular, a sintered body of Cu fine particles is preferable because of its bonding property with the conductor layer 7. By connecting the conductor layer 7 and the semiconductor element 9 through the sintered body of metal particles, even if the metal constituting the conductor layer 7 expands due to heat, it is absorbed into the pores, so that the apparent The elastic modulus decreases. Further, even if a stress caused by a difference in linear expansion coefficient among the semiconductor element 9, the wiring substrate 5, and the conductor layer 7 occurs, the stress is relieved because it is absorbed by the holes. Therefore, peeling and cracks that occur between the semiconductor element 9 and the conductor layer 7 can be reduced. The die bond bonding layer 6 is not limited to a sintered body of metal particles, and a brazing material (solder) having a melting point of 250 ° C. or higher may be used.

(5) Semiconductor element 9
For the semiconductor element 9, Si, SiC, GaN, GaAs, or the like can be employed, and SiC having excellent heat resistance is particularly suitable.

[2-2] Manufacturing Method of Semiconductor Device 1 Next, a manufacturing method of the semiconductor device 1 according to the second embodiment will be described.
First, as shown in FIG. 3A, a wiring substrate 5 is prepared in which a metal circuit layer 3 is bonded to the upper surface of the ceramic substrate 2 and a metal layer 4 is bonded to the lower surface.
Next, as shown in FIG. 3B, a mask 11 having an opening having a size corresponding to the size of the conductor layer 7 is provided at a position corresponding to the position where the semiconductor element 9 is mounted on the metal circuit layer 3. The paste 13 in which the metal particles are dispersed in the dispersant is printed using the squeegee 12. As the mask 11, a metal mask such as stainless steel can be used. The squeegee 12 is preferably made of metal. If the squeegee 12 is made of rubber, a higher hardness can suppress the deformation of the opening of the mask 11 due to the printing pressure, so that the supply amount can be easily controlled. After printing, it is dried in an air atmosphere.

  In the second embodiment, the paste 13 in which metal particles are dispersed in a dispersant is supplied onto the metal circuit layer 3 by printing. However, the present invention is not limited to this, and the paste 13 is supplied by a dispenser. Alternatively, a paste 13 in which metal particles are dispersed in a dispersant is previously formed in a sheet shape may be disposed at a predetermined position on the metal circuit layer 3. As a method for forming the paste 13 in which metal particles are dispersed in a dispersant in a sheet form in advance, a method described in JP2013-041895A can be used.

  Thereafter, as shown in FIG. 3C, the conductor layer 7 is disposed on the paste 13 in which the metal particles are dispersed in the dispersant, and is pressurized and heated in a reduced-pressure atmosphere using a vacuum press 14. Join. The conditions at this time are a temperature of 300 to 350 ° C., a pressure of 3 to 20 MPa, a time of about 5 to 30 minutes, and a longer time is preferable. The atmosphere may be an inert atmosphere or a reducing atmosphere. At this time, in order to equalize the pressure on the lower surface of the wiring board 5 and the upper surface of the conductor layer 7, and to prevent deformation due to local pressurization to the press panel and adhesion of organic substances such as a dispersant, The auxiliary material 15 may be arranged. As the auxiliary material 15, a heat-resistant material, for example, a sheet made of a resin material such as a polyimide film, a liquid crystal polymer, a Teflon (registered trademark) sheet, or a sheet made of a metal material such as copper foil or SUS is used. Can be used. If it is easy to follow the volume change of the sintered body when the pressure is applied, it is possible to reduce the pressure variation and unevenness in the product and between the products. Therefore, it is preferable to use a Teflon sheet.

  Next, as shown in FIG. 4A, after supplying the paste 13 in which the metal particles are dispersed in the dispersant to the position corresponding to the position on the conductor layer 7 where the semiconductor element 9 is mounted, The semiconductor element 9 is disposed thereon. As a supply method and a drying method, a method similar to the method of supplying and drying the paste 13 in which metal particles are dispersed in a dispersant on the metal circuit layer 3 described above can be used. Thereafter, as shown in FIG. 4B, the paste 13 and the semiconductor element 9 in which metal particles are dispersed in a dispersant are disposed on the conductor layer 7 provided on the wiring substrate 5 via the sintered body layer 8. The semiconductor element 9 and the conductor layer 7 are dispersed in the die-bonding bonding layer 6 (in this embodiment, metal particles are dispersed in a dispersing agent by using a vacuum press 14 to pressurize and heat in a vacuum press machine 14. It joins via the sintered body of the paste 13). The conditions at this time are a temperature of 300 to 350 ° C., a pressure of 3 to 20 MPa, a time of about 5 to 30 minutes, and a longer time is preferable. The atmosphere may be an inert atmosphere or a reducing atmosphere. Also in this case, the auxiliary material 15 may be disposed on the lower surface of the wiring board 5 and the upper surface of the semiconductor element 9. In addition, when using solder as the die-bonding bonding layer 6 instead of the sintered body of metal particles, it is preferable to mount with a reflow apparatus.

  Thereafter, a terminal (not shown) formed on the upper surface of the semiconductor element 9 (the surface not bonded to the die bond bonding layer 6) and the wiring 3a of the wiring substrate 5 are connected by wire bonding using the wire 10. The semiconductor device 1 according to the present embodiment is manufactured. In the present embodiment, a DBC substrate is used as the wiring substrate 5, and the sintered body layer 8, the conductor layer 7, the die bond bonding layer 6, and the semiconductor element 9 are mounted on the DBC substrate. A structure in which a sintered body layer 8 and a conductor layer 7 are formed on a DBC substrate may be prepared in advance, and this may be used as a wiring substrate to mount the semiconductor element 9 via the die bond bonding layer 6. .

The present invention will be described more specifically with reference to examples. The present invention is not limited to these examples.
Examples 1 to 9 and Comparative Examples 1 to 6 correspond to the first embodiment, and Examples 10 to 14 and Comparative Examples 7 to 9 correspond to the second embodiment.
[1] Examples 1 to 9 and Comparative Examples 1 to 6 according to the first embodiment
(1) Raw materials, (2) Sintering apparatus, and (3) Evaluation method used in Examples 1 to 9 and Comparative Examples 1 to 6 are described below.

(1) Raw material (a) Connected body As the connected body, the following semiconductor element (1) and Cu circuit (2) were used.
(I) Semiconductor element (1)
The semiconductor element (1) has a size of 7 mm × 7 mm and a thickness of 230 μm, and its joint surface is metallized with a Ti—Ni—Au alloy.
(Ii) Cu circuit (2)
The Cu circuit (2) is oxygen-free copper (C1020) and has a size of 20 mm × 20 mm and a thickness of 300 μm.

(B) Heat bonding material The following heat bonding materials (1) to (4) were used as the heat bonding material.
(I) Heat bonding material (1)
A copper fine particle dispersion (1) in which copper fine particles having an average primary particle diameter of 20 nm are dispersed in diethylene glycol at a concentration of 70% by mass was used. The copper fine particle dispersion (1) contains 2% by mass of polyvinylpyrrolidone as a polymer dispersant.
(Ii) Metal fine particle dispersion (2)
A copper fine particle dispersion (2) in which copper fine particles having an average primary particle diameter of 20 nm and copper fine particles having an average primary particle diameter of 5 μm were dispersed in diethylene glycol at a concentration of 70% by mass in a ratio of 1: 9 was used. In addition, 2 mass% of polyvinyl pyrrolidone is mix | blended with this copper fine particle dispersion material (2) as a polymer dispersing agent.

(Iii) Metal fine particle dispersion (3)
A copper fine particle dispersion (1) in which copper fine particles having an average primary particle diameter of 20 nm were dispersed in diethylene glycol at a concentration of 80% by mass was used. The copper fine particle dispersion (1) contains 2% by mass of polyvinylpyrrolidone as a polymer dispersant. The obtained heat connection material was sandwiched between PET fillets and pressed at 50 MPa to obtain a heat connection sheet having a thickness of 0.5 mm.
Since the metal fine particle dispersion is preformed (formed) at a pressure (50 MPa) higher than the pressure applied during pressure heating, the fluidity of the heat connecting material is extremely poor. When pressurizing and heating at a pressure lower than the pressure of the preform, no pre-drying is required.
(Iv) Metal fine particle dispersion (4)
A silver fine particle dispersion (3) in which silver fine particles having an average primary particle diameter of 20 nm are dispersed in octanediol at a concentration of 90% by mass was used. The copper fine particle dispersion (3) contains 2% by mass of polyethylene glycol as a polymer dispersant.

(2) Sintering apparatus The sintering apparatus shown in FIG. 1 was used. Using this apparatus, the porous metal layer precursor was sintered by the following operation to form a porous metal layer.
A press plate 42 for layup shown in FIG. 1A is prepared, and the work 41 is laid up on the press plate 42 and set on the lower heating plate 44 of the vacuum press machine 43. Thereafter, as shown in FIG. 1B, the chamber 45 is closed and the inside of the chamber 45 is evacuated. Then, as shown in FIG. 1 (c), the workpiece 41 is sandwiched between the upper heating plate 47 and the lower heating plate 44 with the pressure applied by the pressure cylinder 46 and heated.
By the heating and firing, the porous metal layer precursor is sintered to form a porous metal layer.

(3) Evaluation method (a) Measurement of viscosity of heat-bonding material The viscosity was measured according to JIS Z8803 (2011), using a vibration viscometer manufactured by Seconic Corporation, a vibration viscometer, model: VM100A. .
(B) The heat-bonding material after pre-drying has a low displacement viscosity of 100 Pa · s or less when heated at 10 MPa, and the heat-bonding material that needs to be pressurized at the time of sintering can be applied using a press machine after printing, for example. When the pressure heating step is performed, the heating connection material flows around the outer periphery of the connected body, and it is difficult to secure a desired connection thickness. Therefore, it is general that the heat-bonding material having a low viscosity is preliminarily dried so that the contained solvent is removed and the fluidity is lowered. The pre-dried heat-bonded material cannot be measured for viscosity using the vibration viscometer.
Then, the displacement amount of the heating connection material when the desired pressurization was given was measured as a viscosity alternative characteristic of the heat-bonding material after drying. For the measurement of the displacement amount, a flip chip bonder (DB200 manufactured by Kajitani Industry Co., Ltd.) capable of outputting the load and the displacement amount is used to bond the surface of the heated connecting material after pre-drying with a 3.2 mm □ rigid Si chip adsorbed. The amount of displacement was measured from indentation with a tool to application of 10 MPa. When the displacement amount when applying 10 MPa is 10 μm or less, the fluidity of the material is low, the metal particles are easy to bind in the direction parallel to the pressurizing direction during pressure heating, and the average value of the vertical diameter of the pore ferret is the pore It tends to be larger than the average value of the ferret horizontal diameter. When the displacement amount when 10 MPa is applied exceeds 10 μm, the fluidity of the material is high, the metal particles are difficult to bond in a direction parallel to the pressurizing direction during pressurizing and heating, and the average value of the pore ferret vertical diameter is empty. It is hard to become larger than the average value of the hole ferret horizontal diameter.

(C) An image is created by using a scanning electron microscope (SEM) on the cut surface in the vertical direction of the porosity porous metal layer, and the metal fine particles contained in the metal fine particle dispersion of the image are Three-dimensional image processing was performed so as to look whitish, and the porosity (volume%) was calculated from the ratio of black and white contrast.
(D) The average pore size porous metal layer (A) was embedded in an epoxy resin, the cross section was polished and exposed, and observed by a scanning electron microscope.

(E) Measurement of the ferret diameter of the pores The prepared sample was filled with resin, the surface was polished, and the cross-section polished with a cross-section polisher (manufactured by JEOL Ltd.) was used to scan the image using a scanning electron microscope (5000 times SEM magnification). Created and binarized using image processing software (Mitani Corporation, trade name: WinROOF) so that the metal fine particles contained in the metal fine particle dispersion of the image look whitish, and extracted the hole shape Therefore, a void shape extraction range was provided in the processed image (size: vertical 10 μm × horizontal 20 μm, the center of the porous metal layer), and the horizontal ferret diameter and vertical ferret diameter of the holes were calculated. The image processing software has a function for calculating these.

(F) Temperature cycling test (TCT (Temperature Cycling test))
Ten samples in which the body to be connected 1 is bonded to the body to be connected 2 through the porous metal layer, temperature cycle test (holding at + 200 ° C. for 30 minutes and then holding at −55 ° C. for 30 minutes as one cycle, Cycle test for evaluating resistance to temperature change), 1000 cycles have passed, the number of samples where the peeled area becomes 10% or more due to ultrasonic flaws, and the samples where cracking and peeling of the connected body have occurred The number was measured.

[Examples 1 to 9]
(1) Formation of porous metal layer precursor A printing mask having an opening diameter of 7.5 mm □ and a thickness of 0.1 mm is printed on a Cu substrate, and a heating connection material made of a metal fine particle dispersion is printed and supplied with a squeegee. , Drying for 10 minutes in a thermostatic bath set at 110 ° C., placing a semiconductor element on the heated bonding material after drying, for cross-sectional observation measurement (1 piece) and for temperature cycle test (10 pieces) A total of 11 porous metal layer precursors (1) were formed.
(2) Formation of porous metal layer A semiconductor device is disposed on the porous metal layer precursor, and a Cu substrate on which the semiconductor element is disposed on the porous metal layer precursor is sintered, and is described below. As described above, the porous metal layer precursor was heated and sintered.

A 30 μm release material (PTFE sheet) is disposed on the semiconductor element, and at a pressure of 10 MPa from the upper side of the semiconductor element with an upper heating plate in a reduced pressure atmosphere (vacuum degree: 500 Pa) at the same time at 10 ° C./min. Heating was started at a rate of temperature increase, the temperature was raised to 300 ° C., and the temperature was maintained for 20 minutes. Then, it cooled and unloaded.
By the above sintering, a porous metal layer was formed from the porous metal layer precursor on which the semiconductor element was disposed, and the semiconductor element was bonded to the Cu substrate via the porous metal layer.
The results are shown in Table 1.

[Comparative Examples 1-6]
(1) Formation of porous metal layer precursor A printing mask having an opening diameter of 7.5 mm □ and a thickness of 0.1 mm is printed on a Cu substrate, and a heating connection material made of a metal fine particle dispersion is printed and supplied with a squeegee. , Drying for 10 minutes in a thermostatic bath set at 110 ° C., placing a semiconductor element on the heated bonding material after drying, for cross-sectional observation measurement (1 piece) and for temperature cycle test (10 pieces) A total of 11 porous metal layer precursors (1) were formed.
(2) Formation of porous metal layer A Cu substrate in which a semiconductor element is disposed on the porous metal layer precursor and a semiconductor element is disposed on the porous metal layer precursor is used in a sintering apparatus, and is described below. As described above, the porous metal layer precursor was heated and sintered. A 30 μm release material (PTFE sheet) is disposed on the semiconductor element, and simultaneously pressurizes at a pressure of 20 MPa from the upper side of the semiconductor element with a top heating plate in a reduced pressure atmosphere (degree of vacuum: 500 Pa), and at the same time 10 ° C./min. Heating was started at a rate of temperature increase, the temperature was raised to 300 ° C., and the temperature was maintained for 20 minutes. Then, it cooled and unloaded. By the above sintering, a porous metal layer was formed from the porous metal layer precursor on which the semiconductor element was disposed, and the semiconductor element was bonded to the Cu substrate via the porous metal layer.
The results are shown in Table 2.

[Summary of evaluation]
From the results shown in Tables 1 and 2, the connection body (B) and the connection body (C) facing each other in the connection structure of the present invention have a total of the ferret vertical diameters of the holes being equal to the ferret horizontal diameter of the holes. By joining with a porous metal layer (A) that is higher than the total as described above, the joined interface edge between the connected body (B) and the porous metal layer (A), and the porous metal layer (A) It can be confirmed that the stress generated at the joint interface edge of the joined body (C) can be relaxed, so that the joint life can be improved and the heat radiation and conductivity can be maintained to improve the joint reliability. It was.

[2] Examples 10 to 14 and Comparative Examples 7 to 9 according to the second embodiment
Examples 10 to 14 and Comparative Examples 7 to 9 according to the second embodiment are described below.

[Example 10]
As a wiring board, a DBC board (manufactured by Nippon Steel & Sumikin Electrodevice Co., Ltd., Cu (0.3 mmt) / Al ₂ O) bonded to a 28 mm square copper circuit board and a copper board 1 mm inside from the outer edge on a 30 mm square ceramic substrate ₃ (0.635 mmt) / Cu (0.3 mmt)). A stainless steel metal mask having a thickness of 100 um having an opening of 20 mm square was disposed at a position corresponding to a position where a semiconductor element was mounted on a copper circuit board, and a copper nano paste was printed using a metal squeegee. The copper nanopaste was prepared by dispersing copper particles having an average particle diameter of 20 nm as metal fine particles in a dispersant (diethylene glycol) and adding a thickener (polyvinylpyrrolidone). The printing conditions were squeegee pressure 1 MPa, squeegee angle 5 °, squeegee speed 5 mm / sec, and on-contact.

After printing, the substrate was dried at 100 ° C. for 10 minutes in an air atmosphere, and then a conductor layer made of a copper plate having a 20 mm square and a thickness of 0.3 mm was placed on the copper nanopaste and bonded by pressing and heating. The joining was performed using a vacuum press manufactured by Mikado Technos Co., Ltd. under a reduced pressure atmosphere at a temperature of 300 ° C., a pressure of 10 MPa, and a time of 10 Min. Moreover, it joined in the state which mounted the copper plate side of a DBC board | substrate on the Teflon sheet | seat as an auxiliary material, and has arrange | positioned the Teflon sheet | seat further on the conductor layer. The thickness of the sintered body layer at this time was 35 μm.
After that, using the same copper nano paste as the sintered body layer, printing and supplying under the same conditions using a metal mask having an opening of 5 mm square, drying under the same conditions, mounting a semiconductor element thereon, and heating under pressure under the same conditions And joined. Thereafter, the terminals formed on the upper surface of the semiconductor element and the wiring of the wiring board were connected by wire bonding. A semiconductor element having an area of 5 mm × 5 mm and a thickness of 0.23 mm was used.

[Example 11]
The same DBC substrate as the DBC substrate used in Example 10 was prepared, and a stainless steel metal mask with a thickness of 100 μmt having an opening of about 28 mm square was disposed at a position corresponding to the position where the semiconductor element was mounted on the copper circuit board. The copper nano paste was printed using a metal squeegee. The same copper nano paste as in Example 1 was used, and the printing conditions and drying conditions were also the same as in Example 1. After drying, a conductor layer made of a copper plate having the same area as the copper circuit board and having a 28 mm square and a thickness of 0.3 mm was placed on the copper nanopaste, and joined by pressing and heating. Bonding and subsequent placement of the semiconductor element and connection by wire bonding were performed in the same manner as in Example 1.

[Example 12]
As a wiring board, a DBC board (Toshiba Material Co., Ltd., Cu (0.6 mmt) / Si ₃ N ₄ (with a 28 mm square copper circuit board and a copper plate joined 1 mm inside from the outer edge on a 30 mm square ceramic board) A semiconductor device according to Example 12 was manufactured in the same manner as Example 10 except that 0.32 mmt) / Cu (0.6 mmt)).

[Example 13]
The same DBC substrate as the DBC substrate used in Example 10 was prepared, and a stainless metal mask with a thickness of 100 μmt having an opening of about 25 mm square was disposed at a position corresponding to the position on the copper circuit board where the semiconductor element was mounted. The copper nano paste was printed using a metal squeegee. The same copper nano paste as in Example 1 was used, and the printing conditions and drying conditions were also the same as in Example 1. After drying, a conductor layer made of a copper plate having a 25 mm square and a thickness of 0.3 mm having the same area as the copper circuit board was placed on the copper nanopaste and joined by pressing and heating. Bonding and subsequent placement of the semiconductor element and connection by wire bonding were performed in the same manner as in Example 10.

[Example 14]
The same DBC substrate as the DBC substrate used in Example 10 was prepared, and a stainless steel metal mask with a thickness of 100 μm having an opening of about 15 mm square was disposed at a position corresponding to the position where the semiconductor element was mounted on the copper circuit board. The copper nano paste was printed using a metal squeegee. The same copper nano paste as in Example 1 was used, and the printing conditions and drying conditions were also the same as in Example 1. After drying, a conductor layer made of a copper plate having a 15 mm square and a thickness of 0.3 mm having the same area as the copper circuit board was placed on the copper nanopaste and joined by pressing and heating. Bonding and subsequent placement of the semiconductor element and connection by wire bonding were performed in the same manner as in Example 10.

[Comparative Example 7]
The same DBC substrate as the DBC substrate used in Example 10 was prepared, and a copper plate for a conductor layer having a thickness of 0.335 mm and a square of 20 mm was placed at a position corresponding to a position where a semiconductor element was mounted on the copper circuit board. Then, heating was performed at 1075 ° C. for 10 minutes in a nitrogen gas atmosphere, and the copper plates were directly joined to each other (method described in Example 1 of JP-A-1-59986). Subsequent placement of the semiconductor element and connection by wire bonding were performed in the same manner as in Example 1.

[Comparative Example 8]
The same DBC substrate as the DBC substrate used in Example 10 was prepared, and a brazing material composed of Ag 71.0% by mass, Cu 16.5% by mass, and Ti 25% by mass was applied on a copper circuit board to a thickness of 30 μm. A copper plate for a conductor layer of 3 mm and 20 mm square was mounted and heat-bonded in a vacuum furnace. Subsequent placement of the semiconductor element and connection by wire bonding were performed in the same manner as in Example 1.

[Conventional example]
The same DBC substrate as the DBC substrate used in Example 10 was prepared, and a Sn-0.1Ag-0.7Cu solder layer was formed at a position corresponding to the position where the semiconductor element was mounted on the copper circuit board. The semiconductor element was placed thereon and bonded by heating in a nitrogen atmosphere at 240 ° C. for 0.5 minutes. Thereafter, the terminals formed on the upper surface of the semiconductor element and the wiring of the wiring board were connected by wire bonding. A semiconductor element having an area of 5 mm × 5 mm and a thickness of 0.23 mm was used.

  It was confirmed that the semiconductor devices according to Examples 10 to 14 obtained in this way were free from peeling, voids, and poor bonding between layers using an ultrasonic flaw detector.

[Evaluation method]
(1) Evaluation of cracks and delamination between layers For each of the 20 semiconductor packages according to the example and the comparative example, after holding at −40 ° C. for 30 minutes, the temperature is raised to 150 ° C. and held for 30 minutes. A heat cycle test was conducted. Then, the presence or absence of the crack to a board | substrate and peeling between each layer was observed and evaluated with the ultrasonic flaw detector. The results are shown in Table 1. The number of cycles when peeling or cracking is observed in 10% of the joint area with an ultrasonic flaw detector is shown, and the average number of cycles of samples in which peeling or cracking was observed with less than 2000 cycles is shown. (The number in parentheses is the number of samples.) In addition, the case where peeling or cracking was not observed in the number of cycles of 2000 times or more is indicated as 2000 times or more. Moreover, about the thing which peeling or the crack was not seen by 2000 cycles, "-" is described and the sample number is shown.

(2) Evaluation of heat dissipation effect For each of the 20 semiconductor packages according to the example and the comparative example, a current was passed through the semiconductor element so that the heat input was 100 W, and the temperature of the upper surface of the semiconductor element was measured. “◎” indicates that the heat dissipation effect is particularly excellent at 175 ° C. or less, and “B” indicates that the heat dissipation effect is excellent at 175 ° C. or more and 200 ° C. or less, and “X” indicates that the heat dissipation effect is inferior at 200 ° C. or less. The evaluation results are shown in Table 1.

[Summary of evaluation]
In Examples 10 to 14, a sintered body layer made of a sintered body of metal particles (corresponding to the porous metal layer (A) of the first embodiment) is formed on a metal circuit layer, and the sintered body layer Since the conductor layer was formed on the top, cracks and delamination were satisfactorily suppressed, and the heat dissipation effect was also good.

On the other hand, in Comparative Example 7, the conductor layer is not formed at the end portion of the metal circuit layer, and the stress generated at the end portion is reduced, so that the occurrence of peeling and cracking between the metal circuit layer and the conductor layer is reduced. However, since the metal circuit layer and the conductor layer are directly connected without going through the sintered body layer, a slight unbonded portion remains on the joint surface between the metal circuit layer and the conductor layer. It is considered that peeling occurred from the part.
In Comparative Example 8, the metal circuit layer and the conductor layer are joined by the brazing material, and the thermal conductivity between the metal circuit layer and the conductor layer is not high, so that the heat dissipation characteristics are inferior to those of Example 1. ing. Further, due to the difference in linear expansion between the brazing material, the metal circuit layer, and the conductor layer, peeling occurs at the joint surface between the metal circuit layer and the conductor layer. In addition, since cracks and peeling occurred in all samples in an average of 700 cycles, durability confirmation on the ceramic substrate and the metal circuit layer could not be performed.
In the conventional example, since the semiconductor element is connected directly to the metal circuit layer using solder, peeling between layers does not occur, but it is a heat source because it is connected without a conductor layer. Since the heat capacity of the metal circuit layer was small with respect to the heat from the semiconductor element, the heat dissipation characteristics were extremely poor.

  As described above, in Examples 10 to 14 in which the sintered body layer made of the sintered body of metal particles is formed on the metal circuit layer and the conductor layer is formed on the sintered body layer, Comparative Example 7 , 8 and the conventional example could not be realized, and good heat dissipation characteristics and suppression of peeling at the joint surface could be realized. In particular, in Examples 10 and 12, the area of the surface of the conductor layer facing the metal circuit layer is as small as 71% with respect to the area of the metal circuit layer on the conductor layer side, and the conductor layer is at the end of the metal circuit layer. Since they were not laminated, cracks and delamination between the metal circuit layer and the conductor layer and between the ceramic substrate and the metal circuit layer were effectively suppressed, and the heat dissipation characteristics were also good.

As can be seen from Examples 10, 13, and 14, when the area of the surface of the conductor layer facing the metal circuit layer is 70% or more with respect to the area of the metal circuit layer on the conductor layer side, the heat dissipation characteristics are particularly high. Was found to be excellent. Further, when the area of the surface of the conductor layer facing the metal circuit layer is 80% or less with respect to the area of the metal circuit layer on the conductor layer side, the metal circuit layer and the conductor layer, and the ceramic substrate and the metal circuit layer It has been found that the suppression of cracks and delamination of the steel works most effectively. Further, as can be seen from Example 12, by using a ceramic having high fracture toughness such as Si ₃ N _{4 for} the ceramic substrate, more effective suppression of cracks between the ceramic substrate and the metal circuit layer and high heat dissipation characteristics are realized. I was able to. In all of the examples, comparative examples, and conventional examples, the occurrence of cracks between the ceramic substrate and the metal circuit layer could not be confirmed.

As described above, for a semiconductor element such as a power semiconductor element that generates a large amount of heat during driving when operated at a high frequency and a high current, a layer disposed below the semiconductor element is used to release heat instantaneously. It is necessary to increase the heat capacity. Therefore, it has been proposed to increase the heat capacity of the metal circuit layer by increasing the area and thickness of the metal circuit layer (for example, Japanese Patent Application Laid-Open No. 2003-188316).
However, when the area and thickness of the metal circuit layer are increased, if the temperature cycle of being placed in a high temperature environment after being placed in a low temperature environment in the manufacturing stage is repeated, the linear expansion coefficient of the ceramic substrate and the metal circuit layer Since the difference from the linear expansion coefficient is large, there is a problem that the ceramic substrate breaks along the interface of the metal circuit layer.

  In addition, there is a technique (for example, Japanese Patent No. 3932343) that forms a step by etching at the end of the metal circuit layer, but such a technique accurately forms the shape and height of the step at the end of the metal circuit layer. Difficult to do. Further, a refractory metal layer mainly made of a refractory metal and a metal intervening layer having a melting point of 1000 ° C. or less and containing at least one of nickel, copper, and iron as a main component on the ceramic substrate, the metal intervening A technique for joining a conductor layer mainly composed of copper on a layer (for example, Japanese Patent Laid-Open No. 2000-311969) actually forms a metal intervening layer by plating, and has a high melting point at which plating is performed. Since the metal layer or the conductor layer is thin and bulky, the linear expansion is locally different. Therefore, there is a problem that peeling occurs in the metal intervening layer and reliability is lowered.

As described above, particularly in a semiconductor device that generates heat, a metal circuit layer formed on one surface side of a ceramic substrate, and a sintered body formed of a sintered body of metal particles formed on the metal circuit layer. It is preferable to adopt a semiconductor element structure in which the binder layer, the conductor layer formed on the sintered body layer, and the conductor layer are bonded via a die bond bonding layer, and heat dissipation can be improved.
In particular, the metal particle sintered body and the conductor are formed by using a sintered body of metal particles as in the second embodiment, and by making the area of the surface of the conductor layer facing the metal circuit layer smaller than that of the metal circuit layer. Interlayer cracks and peeling can be suppressed, and a highly reliable semiconductor device can be realized.

DESCRIPTION OF SYMBOLS 1 Semiconductor device 2 Ceramic substrate 3 Metal circuit layer (equivalent to the to-be-connected body (B) of 1st Embodiment)
4 Metal layer 5 Wiring board 6 Die bond bonding layer 7 Conductor layer (corresponding to the connected body (C) of the first embodiment)
8 Sintered body layer (corresponding to the porous metal layer (A) of the first embodiment)
9 Semiconductor element 41 Work 42 Press plate 43 Vacuum press machine 44 Lower heating plate 45 Chamber 46 Pressure cylinder 47 Upper heating plate

Claims (5)

A connected structure in which a connected body (C) is joined via a porous metal layer (A) on a connected body (B),
The porosity of the porous metal layer (A) is 2 to 25% by volume,
The ratio (V / H) of the average value (V) of the pore ferret vertical diameter of the porous metal layer (A) and the average value (H) of the horizontal diameter of the pore ferret (V / H) is more than 1 and 1.5 or less. A connection structure having a pore diameter of 30 to 600 nm.   The ratio (V / H) of the average value (V) of the hole ferret vertical diameter of the porous metal layer (A) and the average value (H) of the horizontal hole ferret horizontal diameter is 1.05 to 1.30. The connection structure according to claim 1, wherein: The porous metal layer (A) is formed of one or more selected from gold, silver, copper, aluminum, chromium, nickel, titanium, cobalt, and indium. Item 3. The connection structure according to Item 1 or 2. 1 type or 2 types by which the junction part with the porous metal layer (A) of the said to-be-connected body (B) and a to-be-connected body (C) is each selected from gold | metal | money, silver, copper, chromium, nickel, and titanium The surface formed on the porous metal layer (A) side of the body to be connected (B) and the body to be connected (C) is surface-treated with these metals or alloys, The connection structure according to any one of claims 1 to 3. The connection structure according to any one of claims 1 to 4, wherein at least a part of the pores formed in the porous metal layer (A) is filled with a heat resistant resin (R). body.

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