JP2018111856A - Copper paste for bonding, sintered body, bonded body, semiconductor device and methods for producing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper paste for bonding that can attain sufficient bonding strength even when bonding a semiconductor element having an adherend surface including a noble metal without application of pressure, to provide a sintered body, a bonded body and a semiconductor device each using the copper paste for bonding and to provide methods for producing the sintered body, the bonded body and the semiconductor device.SOLUTION: The copper paste for bonding includes a copper particle, a second metal particle and a dispersion medium. In the copper paste for bonding, the copper particle includes a sub-micro copper particle having a volume average particle size of 0.12 μm to 0.8 μm and a micro copper particle having a volume average particle size of 2 μm to 50 μm; the second metal particle is a particle including at least one kind of metal selected from the group consisting of iron, cobalt and nickel; the volume average particle size of the second metal particle is 0.01 μm to 50 μm; and the content of the second metal particle is 0.01 mass% to 10 mass% on the basis of the total mass of the copper particle and the second metal particle.SELECTED DRAWING: None

Description

  The present invention relates to a bonding copper paste, a sintered body, a bonded body, a semiconductor device, and a manufacturing method thereof.

In manufacturing a semiconductor device, various bonding layers are used to bond a semiconductor element and a lead frame or the like (support member). In particular, high power solder layers have been used as bonding layers in power semiconductors, LSIs, and the like that are operated at high temperatures up to about 150 ° C. In recent years, in accordance with the demand for higher capacity and space saving of semiconductor elements, there is an increasing demand for operating semiconductors at a high temperature of 175 ° C. or higher. Further, in order to ensure the operational stability of the semiconductor device, the bonding layer is required to have high connection reliability and high heat conduction characteristics at high temperatures. However, in this temperature range, the conventionally used high lead solder layer has a problem in connection reliability, and its thermal conductivity is insufficient (30 Wm ⁻¹ K ⁻¹ ), so an alternative material is required.

As an alternative joining layer having such connection reliability and high heat conduction characteristics, a sintered silver layer formed by a sintering phenomenon of silver particles has been proposed (see Patent Document 1 below). Sintered silver layers are reported to have high thermal conductivity (> 100 Wm ⁻¹ K ⁻¹ ) and high connection reliability with respect to the power cycle, and are attracting attention (see Non-Patent Document 1 below). However, in order to ensure connection reliability, a thermocompression bonding process involving pressurization is essential for improving the density of the sintered silver layer, and the mass productivity is significantly reduced. Further, silver has a problem of high material cost.

  On the other hand, a sintered copper layer using copper has been proposed. Copper is superior in mechanical strength to silver, and high-temperature reliability is easily obtained without increasing the density as much as the sintered silver layer, and the material cost can be kept low. As such a sintered copper layer, a sintered copper layer obtained by reducing and sintering copper oxide particles has been proposed (see Patent Document 2 below). This sintered copper layer avoids a decrease in bonding strength due to volume shrinkage due to reduction from copper oxide to copper by a thermocompression bonding process. However, the thermocompression process has the problems described above.

  Patent Document 3 below discloses that a bonding material containing copper nanoparticles and copper microparticles or copper submicroparticles or both can be bonded without pressure.

Japanese Patent No. 4247800 Patent No. 5006081 JP 2014-167145 A

R. Khazaka, L .; Mendizabal, D.M. Henry: J.H. ElecTron. Mater, 43 (7), 2014, 2459-2466

  In the bonding material disclosed in Patent Document 3, since the copper particles used are spherical or pseudo-spherical, the sintered portion between the copper particles tends to be a sintered portion close to a point contact derived from the spherical shape. The strength tends to be insufficient. In addition, since this bonding material is bonded to a chip or a substrate in a form close to point contact, it is difficult to secure a sufficient adhesion area and the bonding strength tends to be low. Therefore, there is a possibility that the connection reliability of the semiconductor device connected by the bonding layer formed from the conventional bonding material cannot be ensured.

  Further, according to the study by the present inventors, it has been found that the above-described conventional bonding material has a remarkably inferior bonding strength to noble metals such as gold and silver compared to bonding strength to copper, nickel and the like. From the viewpoint of rust prevention and the like, a semiconductor element may be subjected to a treatment for coating a deposition surface with a noble metal such as gold or silver by a method such as plating or sputtering. Such a process facilitates a performance test before mounting the semiconductor element, and can suppress variations in bonding strength due to the formation of an oxide film. The bonding material capable of firmly bonding the noble metal can further improve the connection reliability when bonding the semiconductor elements as described above.

  An object of this invention is to provide the copper paste for joining which can obtain sufficient joining strength, even when it joins a semiconductor element provided with the adherend surface containing a noble metal without a pressure. It is another object of the present invention to provide a sintered body, a bonded body, a semiconductor device, and a manufacturing method thereof, which are manufactured using a bonding copper paste.

  One aspect of the present invention is a bonding copper paste including copper particles, second metal particles, and a dispersion medium, wherein the copper particles have a volume average particle size of 0.12 μm to 0.8 μm. Including at least one metal selected from the group consisting of iron, cobalt, and nickel, including a certain sub-micro copper particle and a micro-copper particle having a volume average particle diameter of 2 μm to 50 μm. The volume average particle diameter of the second metal particles is 0.01 μm or more and 50 μm or less, and the content of the second metal particles is based on the total mass of the copper particles and the second metal particles. 0.01 mass% or more and 10 mass% or less.

  According to the copper paste for bonding of the present invention, sufficient bonding strength can be obtained even when a semiconductor element having a deposition surface containing a noble metal is bonded without pressure. The present inventors infer the reason why such an effect is obtained as follows. First, by containing the sub-micro copper particles and the micro-copper particles at a specific ratio, the volume shrinkage during sintering due to the surface protective agent or the dispersion medium is sufficiently maintained while maintaining sufficient sinterability. Even when joining without pressure, it is possible to ensure the strength of the sintered body and improve the joining force with the adherend surface, and the second metal particles work as a sintering aid, By obtaining a sintered body in which multiple types of metals are dissolved or dispersed, mechanical properties such as yield stress and fatigue strength of the sintered body are improved, and for members having a deposition surface containing noble metals. However, it is considered that sufficient bonding strength was obtained.

  One aspect of the present invention is a sintered body for joining the first member and the second member, and the sintered body is at least one selected from the group consisting of copper element, iron, cobalt, and nickel. The total content of at least one metal element selected from the group consisting of iron, cobalt, and nickel is 0.01% by mass or more and 10% by mass based on the total mass of the sintered body. % Or less. According to the sintered body of the present invention, sufficient bonding strength can be obtained even on the adherend surface containing the noble metal.

  In the sintered body, at least one metal element selected from the group consisting of iron, cobalt, and nickel is unevenly distributed on the surface side in contact with the first member and / or the second member of the sintered body. Also good. In this case, the content of the metal element on the surface side in contact with the member can be increased, and it is easy to improve the bonding strength to the adherend surface containing the noble metal without significantly impairing the sinterability of the sintered body. It becomes.

  One aspect of the present invention is a method of manufacturing a sintered body for joining a first member and a second member, and includes a step of sintering the joining copper paste. In the said manufacturing method, you may apply a magnetic field to the said copper paste for joining before sintering and / or during sintering. In this case, the second metal particles in the bonding copper paste can be unevenly distributed on the side in contact with the member, and it is easy to improve the bonding strength when the member and the sintered body are bonded.

  One aspect of the present invention is a joined body including a first member, a second member, and a sintered body that joins the first member and the second member, wherein the sintered body is A total content of at least one metal element selected from the group consisting of iron, cobalt, and nickel, including copper element and at least one metal element selected from the group consisting of iron, cobalt, and nickel However, it is 0.01 mass% or more and 10 mass% or less on the basis of the total mass of a sintered compact. According to the joined body of the present invention, sufficient joining strength can be obtained even when the first member or the second member has a deposition surface containing a noble metal.

  In the joined body, even if at least one metal element selected from the group consisting of iron, cobalt, and nickel is unevenly distributed on the surface side in contact with the first member and / or the second member of the sintered body Good. In this case, the content of the metal element on the surface side in contact with the member can be increased, and it is easy to improve the bonding strength to the adherend surface containing the noble metal without significantly impairing the sinterability of the sintered body. It becomes.

  One aspect of the present invention is to prepare a laminated body in which the first member, the bonding copper paste, and the second member are laminated in this order on the side in which the weight of the first member acts. It is a manufacturing method of a semiconductor device provided with the process of sintering the copper paste for the state which received the self weight of the 1st member, or the self weight of the 1st member, and the pressure of 0.01 Mpa or less. In the said manufacturing method, you may apply a magnetic field to the said copper paste for joining before sintering and / or during sintering.

  According to the method for manufacturing a joined body of the present invention, by using the joining copper paste, the die shear strength is excellent even when a member having a deposition surface containing a noble metal is joined without pressure. A joined body can be manufactured.

  One aspect of the present invention includes a first member, a second member, and a sintered body that joins the first member and the second member, and includes the first member and the second member. At least one is a semiconductor element, and the sintered body includes a copper element and at least one metal element selected from the group consisting of iron, cobalt, and nickel, and is selected from the group consisting of iron, cobalt, and nickel The total content of the at least one metal element is 0.01% by mass or more and 10% by mass or less based on the total mass of the sintered body. According to the semiconductor device of the present invention, sufficient bonding strength can be obtained even for a semiconductor element having a deposition surface containing a noble metal.

  In the semiconductor device, even if at least one metal element selected from the group consisting of iron, cobalt, and nickel is unevenly distributed on the surface side in contact with the first member and / or the second member of the sintered body Good. In this case, the mechanical properties such as the yield stress and fatigue strength of the sintered body are further improved by increasing the content of the metal element on the surface side in contact with the member or the semiconductor element, and the deposition including the noble metal is included. There exists a tendency for the joint strength with respect to a surface to improve.

  One aspect of the present invention is a laminate in which the first member, the bonding copper paste according to claim 1 and the second member are laminated in this order on the side in which the weight of the first member acts. Preparing the bonding copper paste by sintering under the condition that the weight of the first member or the weight of the first member and the pressure of 0.01 MPa or less are received. And a method for manufacturing a semiconductor device, wherein at least one of the second members is a semiconductor element. In the said manufacturing method, you may apply a magnetic field to the said copper paste for joining before sintering and / or during sintering.

  According to the method for manufacturing a semiconductor device of the present invention, by using the bonding copper paste, the die shear strength is excellent even when a semiconductor element having a deposition surface containing a noble metal is bonded without pressure. A semiconductor device can be manufactured. Further, the semiconductor device manufactured by the method for manufacturing a semiconductor device of the present invention can be excellent in connection reliability.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where a semiconductor element provided with the adherend surface containing a noble metal is joined without a pressure, the copper paste for joining which can obtain sufficient joining strength can be provided. The present invention can also provide a sintered body, a bonded body, a semiconductor device, and a manufacturing method thereof using the bonding copper paste.

It is a schematic cross section which shows an example of the sintered compact manufactured using the copper paste for joining of this embodiment. It is a schematic cross section which shows an example of the dispersion state of a metal particle after apply | coating the copper paste for joining of this embodiment. It is a schematic cross section which shows an example of the uneven distribution state of a metal particle when a magnetic field is applied after apply | coating the copper paste for joining of this embodiment. It is a schematic cross section which shows an example of the joined body manufactured using the copper paste for joining of this embodiment. It is a schematic cross section which shows an example of the semiconductor device manufactured using the copper paste for joining of this embodiment.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments.

<Copper paste for bonding>
The bonding copper paste of this embodiment includes copper particles, second metal particles, and a dispersion medium.

(Copper particles)
Examples of the copper particles according to this embodiment include sub-micro copper particles and micro-copper particles.

(Sub-micro copper particles)
The sub-micro copper particles may be copper particles having sinterability in a temperature range of 250 ° C. or higher and 350 ° C. or lower. Examples of the sub-micro copper particles include those containing copper particles having a particle size of 0.12 μm or more and 0.8 μm or less. For example, copper particles having a volume average particle size of 0.12 μm or more and 0.8 μm or less are used. it can. When the volume average particle diameter of the sub-micro copper particles is 0.12 μm or more, effects such as suppression of the synthesis cost of the sub-micro copper particles, good dispersibility, and suppression of the use amount of the surface treatment agent are easily obtained. If the volume average particle diameter of the sub-micro copper particles is 0.8 μm or less, an effect that the sinterability of the sub-micro copper particles is excellent is easily obtained. From the viewpoint of further exerting the above effects, the volume average particle diameter of the sub-micro copper particles may be 0.15 μm or more and 0.8 μm or less, 0.15 μm or more and 0.6 μm or less, and 0 It may be not less than 2 μm and not more than 0.5 μm, and may be not less than 0.3 μm and not more than 0.45 μm.

  In the present specification, the volume average particle diameter means 50% volume average particle diameter. When determining the volume average particle size of the copper particles, the copper particles used as the raw material or the dried copper particles obtained by removing volatile components from the bonding copper paste, dispersed in a dispersion medium using a dispersant, the light scattering particle size It can obtain | require by the method etc. which measure with a distribution measuring apparatus (For example, Shimadzu nanoparticle diameter distribution measuring apparatus (SALD-7500nano, Shimadzu Corporation make)). When using a light scattering particle size distribution analyzer, hexane, toluene, α-terpineol, 4-methyl-1,3-dioxolan-2-one, or the like can be used as a dispersion medium.

  The content of the sub-micro copper particles may be 20% by mass or more and 90% by mass or less, and 30% by mass or more and 90% by mass or less based on the total mass of the copper particles and the second metal particles. It may be 35 mass% or more and 85 mass% or less, and may be 40 mass% or more and 80 mass% or less. If the content of the sub-micro copper particles is within the above range, it becomes easy to secure the bonding strength of the bonded body manufactured by sintering the bonding copper paste, and the bonding copper paste can be used for bonding semiconductor elements. When used, the semiconductor device tends to exhibit good die shear strength and connection reliability.

  The content of the sub-micro copper particles is preferably 20% by mass or more and 90% by mass or less based on the total mass of the sub-micro copper particles and the mass of the micro-copper particles. If the content of the sub-micro copper particles is 20% by mass or more, the space between the micro-copper particles can be sufficiently filled, and the bonding strength of the bonded body manufactured by sintering the bonding copper paste is ensured. When the bonding copper paste is used for bonding semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. If the content of the sub-micro copper particles is 90% by mass or less, volume shrinkage when the bonding copper paste is sintered can be sufficiently suppressed. Therefore, the bonded body manufactured by sintering the bonding copper paste It becomes easy to ensure the bonding strength, and when the bonding copper paste is used for bonding semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. From the viewpoint of easily obtaining the above effect, the content of the sub-micro copper particles may be 30% by mass or more and 85% by mass or less based on the total mass of the sub-micro copper particles and the mass of the micro-copper particles. It may be 35% by mass or more and 85% by mass or less, or 40% by mass or more and 80% by mass or less.

  The shape of the sub-micro copper particles is not particularly limited. Examples of the shape of the sub-micro copper particles include a spherical shape, a lump shape, a needle shape, a flake shape, a substantially spherical shape, and an aggregate thereof. From the viewpoint of dispersibility and filling properties, the shape of the sub-micro copper particles may be spherical, substantially spherical, or flaky. From the viewpoint of combustibility, dispersibility, miscibility with flaky micro-copper particles, It may be spherical or approximately spherical. In the present specification, the “flakes” include flat shapes such as plates and scales.

  The sub-micro copper particles may have an aspect ratio of 5 or less or 3 or less from the viewpoint of dispersibility, filling properties, and miscibility with the flaky micro-copper particles. In this specification, “aspect ratio” indicates the long side / thickness of a particle. The measurement of the long side and thickness of the particle can be obtained, for example, from the SEM image of the particle.

  The sub-micro copper particles may be treated with a specific surface treatment agent. Examples of the specific surface treatment agent include organic acids having 2 to 18 carbon atoms. Examples of the organic acid having 2 to 18 carbon atoms include acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, caprylic acid, methylheptanoic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, and methyloctane. Acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid, ethyloctanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanoic acid, lauric acid, methylundecane Acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, pentylheptanoic acid, tridecanoic acid, methyldodecanoic acid, ethylundecanoic acid, propyldecanoic acid, butylnonanoic acid, pentyloctanoic acid, myristic acid, methyltridecanoic acid, ethyldodecane Acid, propylundecanoic acid, butyldecanoic acid, pentylnonanoic acid, hexyloctanoic acid, pentadecanoic acid, methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, Ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecanoic acid, heptylnonanoic acid, heptadecanoic acid, octadecanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentyl Cyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid , Saturated fatty acids such as nonylcyclohexanecarboxylic acid; octenoic acid, nonenoic acid, methylnonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, sabienoic acid, Unsaturated fatty acids such as oleic acid, vaccenic acid, linoleic acid, linolenic acid, linolenic acid; terephthalic acid, pyromellitic acid, o-phenoxybenzoic acid, methylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, pentyl Examples thereof include aromatic carboxylic acids such as benzoic acid, hexyl benzoic acid, heptyl benzoic acid, octyl benzoic acid, and nonyl benzoic acid. An organic acid may be used individually by 1 type, and may be used in combination of 2 or more type. By combining such an organic acid and the sub-micro copper particles, the dispersibility of the sub-micro copper particles and the detachability of the organic acid during sintering tend to be compatible.

The treatment amount of the surface treatment agent may be an amount that adheres to a monomolecular layer to a trimolecular layer on the surface of the sub-micro copper particles. This amount includes the number of molecular layers attached to the surface of the sub-micro copper particles (n), the specific surface area (Ap) of the sub-micro copper particles (unit m ² / g), and the molecular weight (M _s ) (unit of the surface treatment agent) g / mol), the minimum surface area of the surface treatment agent (S _S ) (unit m ² / piece), and the Avogadro number (N _A ) (6.02 × 10 ²³ pieces). Specifically, the treatment amount of the surface treatment agent is the treatment amount of the surface treatment agent (% by mass) = {(n · A _p · M _s ) / (S _S · N _A + n · A _p · M _s )} It is calculated according to the formula of x100.

The specific surface area of the sub-micro copper particles can be calculated by measuring the dried sub-micro copper particles by the BET specific surface area measurement method. Minimum coverage of the surface treatment agent, if the surface treatment agent is a straight-chain saturated fatty acids, is 2.05 × ¹⁰ -19 ^m 2/1 molecule. In the case of other surface treatment agents, for example, calculation from a molecular model, or “Chemistry and Education” (Akihiro Ueda, Juno Inafuku, Mori Kaoru, 40 (2), 1992, p114-117) It can be measured by the method described. An example of the method for quantifying the surface treatment agent is shown. The surface treatment agent can be identified by a thermal desorption gas / gas chromatograph mass spectrometer of a dry powder obtained by removing the dispersion medium from the bonding copper paste, whereby the carbon number and molecular weight of the surface treatment agent can be determined. The carbon content of the surface treatment agent can be analyzed by carbon content analysis. Examples of the carbon analysis method include a high frequency induction furnace combustion / infrared absorption method. The amount of the surface treatment agent can be calculated by the above formula from the carbon number, molecular weight, and carbon content ratio of the identified surface treatment agent.

  The treatment amount of the surface treatment agent may be 0.07% by mass or more and 2.1% by mass or less, may be 0.10% by mass or more and 1.6% by mass or less, and may be 0.2% by mass. It may be 1.1% by mass or less.

  Since the above-mentioned sub-micro copper particles have good sinterability, there are problems such as expensive synthesis cost, poor dispersibility, and decrease in volume shrinkage after sintering, which are mainly seen in bonding materials using copper nanoparticles. Can be reduced.

  As the sub-micro copper particles according to the present embodiment, commercially available ones can be used. Commercially available sub-micro copper particles include, for example, CH-0200 (Mitsui Metal Mining Co., Ltd., volume average particle size 0.36 μm), HT-14 (Mitsui Metal Mining Co., Ltd., volume average particle size 0. 41 μm), CT-500 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 0.72 μm), and Tn—Cu100 (manufactured by Taiyo Nissan Co., Ltd., volume average particle size 0.12 μm).

(Micro copper particles)
The micro copper particles include those containing copper particles having a particle size of 2.0 μm or more and 50 μm or less. For example, copper particles having a volume average particle size of 2.0 μm or more and 50 μm or less can be used. If the volume average particle diameter of the micro copper particles is within the above range, the volume shrinkage when the bonding copper paste is sintered can be sufficiently reduced, and the bonded body manufactured by sintering the bonding copper paste is bonded. It becomes easy to ensure the strength, and when the bonding copper paste is used for bonding semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. From the viewpoint of easily obtaining the above effects, the volume average particle diameter of the micro copper particles may be 2 μm or more, 3 μm or more, and 20 μm or less, and 10 μm or less. It may be the following.

  The content of the micro copper particles may be 10% by mass or more and 90% by mass or less, or 15% by mass or more and 65% by mass or less based on the total mass of the copper particles and the second metal particles. 20 mass% or more and 60 mass% or less may be sufficient. If the content of the micro copper particles is within the above range, it becomes easy to secure the bonding strength of the bonded body manufactured by sintering the bonding copper paste, and the bonding copper paste can be used for bonding semiconductor elements. When used, the semiconductor device tends to exhibit good die shear strength and connection reliability.

  The total of the content of the sub-micro copper particles and the content of the micro-copper particles can be 80% by mass or more based on the total mass of the copper particles and the second metal particles. If the total of the content of the sub-micro copper particles and the content of the micro-copper particles is within the above range, the volume shrinkage when the bonding copper paste is sintered can be sufficiently reduced, and the bonding copper paste is sintered. It is easy to ensure the bonding strength of the bonded body manufactured in this manner. When the bonding copper paste is used for bonding semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. From the viewpoint that the above effect is easily obtained, the total content of the sub-micro copper particles and the content of the micro-copper particles is 90% by mass or more based on the total mass of the copper particles and the second metal particles. It may be 95% by mass or more. From the viewpoint of the sinterability of the copper particles, the total content of the sub-micro copper particles and the content of the micro-copper particles is 99.99 mass based on the total mass of the copper particles and the second metal particles. % Or less, or 99.0% by mass or less.

  The shape of the micro copper particles is not particularly limited. Examples of the shape of the micro copper particles include a spherical shape, a lump shape, a needle shape, a flake shape, a substantially spherical shape, and an aggregate thereof. Among these, the shape of the micro copper particles is preferably a flake shape. By using flaky micro copper particles, the micro copper particles in the bonding copper paste are oriented substantially parallel to the bonding surface, thereby suppressing volume shrinkage when the bonding copper paste is sintered. This makes it easy to secure the bonding strength of the bonded body manufactured by sintering the bonding copper paste. When the bonding copper paste is used for bonding semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. From the viewpoint of easily obtaining the above effect, the flaky micro copper particles may have an aspect ratio of 4 or more, or 6 or more.

  In the micro copper particles, the presence or absence of the treatment with the surface treatment agent is not particularly limited. From the viewpoint of dispersion stability and oxidation resistance, the micro copper particles may be treated with a surface treatment agent. The surface treatment agent may be removed at the time of joining. Examples of such surface treatment agents include aliphatic carboxylic acids such as dodecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, arachidic acid, linoleic acid, linolenic acid, oleic acid; terephthalic acid, pyromellitic acid, o- Aromatic carboxylic acids such as phenoxybenzoic acid; aliphatic alcohols such as cetyl alcohol, stearyl alcohol, isobornylcyclohexanol, tetraethylene glycol; aromatic alcohols such as p-phenylphenol; octylamine, dodecylamine, stearylamine, etc. Alkyl diamines; aliphatic nitriles such as stearonitrile and decane nitrile; silane coupling agents such as alkyl alkoxy silanes; polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, silicone oligomers, etc. Child process, and the like. A surface treating agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The treatment amount of the surface treatment agent may be a monomolecular layer or more on the particle surface. The treatment amount of such a surface treatment agent varies depending on the specific surface area of the micro copper particles, the molecular weight of the surface treatment agent, and the minimum coating area of the surface treatment agent. The treatment amount of the surface treatment agent is usually 0.001% by mass or more. The specific surface area of the micro copper particles, the molecular weight of the surface treatment agent, and the minimum coating area of the surface treatment agent can be calculated by the method described above.

  When the bonding copper paste is prepared only from the above-mentioned sub-micro copper particles, the volume shrinkage and the sintering shrinkage accompanying the drying of the dispersion medium are large. In joining elements and the like, it is difficult to obtain sufficient die shear strength and connection reliability. When the bonding copper paste is prepared only from the micro copper particles as the copper particles, the sintering temperature tends to increase, and a sintering step of 400 ° C. or more tends to be required. By using the sub-micro copper particles and the micro copper particles in combination, volume shrinkage when the bonding copper paste is sintered is suppressed, and the bonded body can have sufficient bonding strength. When the bonding copper paste is used for bonding semiconductor elements, an effect that the semiconductor device exhibits good die shear strength and connection reliability can be obtained.

  Commercially available micro copper particles according to the present embodiment can be used. Examples of commercially available micro copper particles include MA-C025 KFD (Mitsui Metal Mining Co., Ltd., volume average particle size 7.5 μm), 3L3 (Fukuda Metal Foil Powder Co., Ltd., volume average particle size 8.0 μm). ) 1110F (Mitsui Metal Mining Co., Ltd., volume average particle size 3.8 μm), HWQ 3.0 μm (Fukuda Metal Foil Powder Co., Ltd., volume average particle size 3.0 μm).

(Second metal particles)
Examples of the second metal particle include particles containing at least one metal selected from the group consisting of iron, cobalt, and nickel. The second metal particle may be a magnetic metal particle. In the present specification, the magnetic metal particle means a ferromagnetic metal particle having a property of attaching to a magnet. As the second metal particles, an oxide system or a nitride system of the above metal can also be used. The second metal particles also include metal particles containing the metal as an alloy. The copper paste may contain one or more of these second metal particles.

For example, the second metal particles preferably have a magnetic permeability of 1 × 10 ⁻⁴ or more, and more preferably 1 × 10 ⁻³ or more. Further, in the second metal particles, the content of iron, cobalt, or nickel is preferably 50% by mass or more based on the total mass of the second metal particles, and 90% by mass or more. More preferably, it may be 100% by mass.

  The particle shape of the second metal particles is not particularly limited. Examples of the shape of the second metal particle include a spherical shape, a lump shape, a needle shape, a flake shape, a substantially spherical shape, and an aggregate thereof. From the viewpoint of dispersibility and filling properties, the shape of the second metal particles may be spherical, substantially spherical, or flaky. From the viewpoint of combustibility, dispersibility, miscibility with other copper particles, and the like, It may be spherical or approximately spherical.

  The volume average particle diameter of the second metal-based particles is preferably 0.01 μm or more and 50 μm or less, more preferably 0.02 μm or more and 20 μm or less, and further preferably 0.03 μm or more and 5 μm or less. . If the volume average particle diameter of the second metal particles is within the above range, when the second metal particles are unevenly distributed by a magnetic field, the second metal particles are easily moved in the connection copper paste, which is good. Can be obtained. In the connection copper paste, the second metal particles are unevenly distributed on the surface side of the member to be joined, so that high joining strength can be easily secured after joining.

  The content of the second metal particles is preferably 0.01% by mass or more and 10% by mass or less, and 0.05% by mass or more and 5% by mass based on the total mass of the copper particles and the second metal particles. % Or less, more preferably 0.1% by mass or more and 2% by mass or less. If content of a 2nd metal particle is in the said range, it will be hard to influence the sinterability of the copper paste for joining. Furthermore, when the second metal particles are unevenly distributed on the bonding interface side, a sufficient amount of the second metal particles can be present at the bonding interface, and it is easy to ensure high bonding strength for the noble metal member. Thus, when the bonding copper paste is used for bonding semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability.

  The presence or absence of the treatment of the surface treatment agent for the second metal particles is not particularly limited. From the viewpoint of dispersion stability and oxidation resistance, the second metal particles may be treated with a surface treatment agent. The surface treatment agent may be removed at the time of joining. As a specific surface treatment agent for the second metal particles, the above-mentioned surface treatment agent used for sub-micro copper particles or micro-copper particles can be used.

  What is marketed can be used as the 2nd metal particle which concerns on this embodiment. Examples of commercially available second metal particles include iron powder (50% volume average particle size 45 μm, manufactured by Wako Pure Chemical Industries, Ltd.), cobalt powder Cobalt Powder S-160 (50% volume average particle size 3. 0 μm, manufactured by Freeport Cobalt), nickel particles (50% volume average particle size 1.5 μm, manufactured by METAL FOIL & POWDERS MFG CO.).

  By adding the second metal particles, the metal elements derived from the second metal particles are dissolved or dispersed in the sintered copper, and mechanical properties such as yield stress and fatigue strength are improved. This increases the bonding strength and connection reliability. In particular, in the bonding copper paste, the second metal particles are unevenly distributed in the vicinity of the bonding interface with the member by a magnetic field, so that the sintered copper paste, that is, the sintered body, the bonding interface with the member or the vicinity thereof In addition, the metal element derived from the second metal particles can be unevenly distributed (segregated), and the above effect can be further exerted, so that high bonding strength can be ensured even if the member is a noble metal.

(Dispersion medium)
The dispersion medium is not particularly limited, and may be volatile. Examples of volatile dispersion media include monovalent and polyvalent pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, α-terpineol, isobornylcyclohexanol (MTPH), and the like. Alcohols, ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol diether Chill ether, diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol Ethers such as butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, tripropylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol Butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, esters such as propylene carbonate, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N -Acid amides such as dimethylformamide, aliphatic hydrocarbons such as cyclohexane, octane, nonane, decane and undecane, aromatic hydrocarbons such as benzene, toluene and xylene, mercaptans having an alkyl group having 1 to 18 carbon atoms, carbon Examples include mercaptans having a cycloalkyl group of 5 to 7. Examples of mercaptans having an alkyl group having 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan. And dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan.

  The content of the dispersion medium may be 5 to 50 parts by mass, where the total mass of the copper particles and the second metal particles is 100 parts by mass. When the content of the dispersion medium is within the above range, the bonding copper paste can be adjusted to a more appropriate viscosity, and the sintering of the copper particles is hardly inhibited.

(Additive)
The bonding copper paste may further contain additives such as a dispersant, a surface protective agent, a thickener, and a thixotropic agent as necessary. When the bonding copper paste contains an additive, the content of the additive that is nonvolatile or non-degradable at a temperature of 200 ° C. or lower is preferably 20% by mass or less, and more preferably 5% by mass or less. It is preferably 1% by mass or less. If the content rate of an additive is the said range, it will be easy to suppress the sinterability fall of the copper paste for joining.

  As an aspect of the bonding copper paste of the present embodiment, the copper particles have a volume average particle size of 0.12 μm or more and 0.8 μm or less, preferably 0.15 μm or more and 0.8 μm or less; And a copper particle having a volume average particle diameter of 2 μm or more and 50 μm or less, and the second metal particle is a particle containing at least one metal selected from the group consisting of iron, cobalt, and nickel, The volume average particle diameter of the second metal particles is 0.01 μm or more and 50 μm or less, and the content of the second metal particles is 0.01 based on the total mass of the copper particles and the second metal particles. Examples include a copper paste for bonding that is 10% by mass or more.

  The bonding copper paste includes a sub-micro copper particle having a volume average particle size of 0.12 μm to 0.8 μm, preferably 0.15 μm to 0.8 μm, and a volume average particle size of 2 μm to 50 μm. A micro copper particle, a second metal particle, a dispersion medium, and other components as necessary are blended, and the second metal particle is selected from the group consisting of iron, cobalt, and nickel. Particles containing at least one kind of metal, wherein the volume average particle size of the second metal particles is 0.01 μm or more and 50 μm or less, and the content of the second metal particles is that of the copper particles and the second metal particles. What is 0.01 mass% or more and 10 mass% or less is mentioned on the basis of the sum total of mass.

  Further, as another aspect of the bonding copper paste of the present embodiment, as sub-micro copper particles, copper particles having a particle diameter of 0.12 μm to 0.8 μm, preferably 0.15 μm to 0.8 μm are used. Containing, as micro copper particles, containing micro copper particles having a particle diameter of 2 μm or more and 50 μm or less, and the second metal particles include at least one metal selected from the group consisting of iron, cobalt, and nickel The second metal particles have a particle diameter of 0.01 μm or more and 50 μm or less, and the content of the second metal particles is 0.00 on the basis of the total mass of the copper particles and the second metal particles. What is 01 mass% or more and 10 mass% or less is mentioned. The particle diameter here means the maximum particle diameter, and is determined by a method of observing, with a scanning electron microscope (SEM), copper particles as raw materials or dry copper particles from which volatile components have been removed from the bonding copper paste.

  When the copper particles or the second metal particles are not spherical, the particle diameter can be determined as the maximum particle diameter by the following method. A method for calculating the major axis of the copper particles from the SEM image is exemplified. The copper particle powder is placed on a carbon tape for SEM with a spatula to obtain a sample for SEM. The SEM sample is observed at 100 to 5000 times with a SEM apparatus. A rectangle circumscribing the copper particles of this SEM image is drawn by image processing software, and the long side of the rectangle is the major axis of the particles. Also in the second metal particle, the particle diameter can be obtained by the same method.

(Preparation of bonding copper paste)
The bonding copper paste can be prepared by mixing the above-mentioned sub-micro copper particles, micro-copper particles, second metal particles and any additive in a dispersion medium. You may perform a stirring process after mixing of each component. The bonding copper paste may adjust the maximum particle size of the dispersion by classification operation.

  The bonding copper paste is prepared by mixing sub-micro copper particles, a surface treatment agent and a dispersion medium in advance, and performing a dispersion treatment to prepare a dispersion of sub-micro copper particles. Arbitrary additives may be mixed and prepared. By setting it as such a procedure, the dispersibility of a sub micro copper particle improves, a mixing property with a micro copper particle improves, and the performance of the copper paste for joining improves more. Aggregates may be removed from the sub-micro copper particle dispersion by classification.

  The stirring treatment can be performed using a stirrer. Examples of the stirrer include a rotation / revolution stirrer, a reiki machine, a twin-screw kneader, a three-roll mill, a planetary mixer, and a thin-layer shear disperser.

  Classification operation can be performed using filtration, natural sedimentation, and centrifugation, for example. Examples of the filter for filtration include a metal mesh, a metal filter, and a nylon mesh.

  Examples of the dispersion treatment include a thin layer shear disperser, a bead mill, an ultrasonic homogenizer, a high shear mixer, a narrow gap three-roll mill, a wet super atomizer, a supersonic jet mill, and an ultra high pressure homogenizer.

  The copper paste for bonding may be adjusted to a viscosity suitable for each printing / coating method when molding. The viscosity of the bonding copper paste may be, for example, a Casson viscosity at 25 ° C. of 0.05 Pa · s to 2.0 Pa · s, and 0.06 Pa · s to 1.0 Pa · s. Also good.

  According to the bonding copper paste of this embodiment, by using the above-mentioned sub-micro copper particles and micro-copper particles together in a predetermined ratio, good sinterability can be obtained, and volume shrinkage during sintering can be achieved. Can be suppressed. Furthermore, by including the second metal particles, the metal element derived from the second metal particles is in a solid solution or dispersed state in the sintered copper, and mechanical properties such as yield stress and fatigue strength are improved. This increases the bonding strength and connection reliability. In particular, in the bonding copper paste, the second metal particles are unevenly distributed in the vicinity of the bonding interface with the member by a magnetic field, so that the sintered copper paste, that is, the sintered body, the bonding interface with the member or the vicinity thereof In addition, the metal element derived from the second metal particles can be unevenly distributed (segregated), and the above effect can be further exerted, so that high bonding strength can be ensured even if the member is a noble metal. Therefore, the bonding copper paste of the present embodiment can ensure the bonding force with the member without excessive pressurization, and the bonded body manufactured by sintering the bonding copper paste is sufficient. It can have bonding strength. When the bonding copper paste is used for bonding semiconductor elements, the semiconductor device can exhibit good die shear strength and connection reliability. That is, the bonding copper paste of this embodiment may be used as a bonding material for pressureless bonding. Moreover, according to the copper paste for joining of this embodiment, manufacturing cost can be held down and mass production can be performed by using comparatively cheap copper particles. In particular, since the bonding copper paste of this embodiment can obtain the above-described effects by the sub-micro copper particles and the micro-copper particles, it is cheaper than a bonding material mainly composed of expensive copper nanoparticles. And it has the advantage that it can supply stably. Thereby, for example, when manufacturing a joined body such as a semiconductor device, it is possible to further improve the production stability. In the present specification, “no pressure” means the weight of a member to be joined, or a state in which a pressure of 0.01 MPa or less is applied in addition to its own weight.

<Sintered body, bonded body and semiconductor device>
Hereinafter, preferred embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  The sintered body of the present embodiment is a sintered body that joins the first member and the second member, and the sintered body is selected from the group consisting of copper element, iron, cobalt, and nickel. The total content of at least one metal element selected from the group consisting of iron, cobalt, and nickel, including at least one metal element, is 0.01% by mass or more based on the total mass of the sintered body It is 10 mass% or less.

  The total content of at least one metal element selected from the group consisting of iron, cobalt, and nickel is preferably 0.05% by mass or more and 5% by mass or less based on the total mass of the sintered body. More preferably, the content is 0.1% by mass or more and 2% by mass or less. If the content of the metal element is within the above range, it becomes easy to secure a high bonding strength with respect to a noble metal member. When the sintered body is used for bonding a semiconductor element, the semiconductor device has a good die share. It tends to show strength and connection reliability. The content of the metal in the sintered body can be calculated by EPMA analysis, EDX analysis, quantitative analysis by powder X-ray diffraction method or the like, or ICP plasma emission analysis.

  In the sintered body of the present embodiment, at least one metal element selected from the group consisting of iron, cobalt, and nickel is unevenly distributed on the surface side in contact with the first member and / or the second member. Good. FIG. 1 is a schematic cross-sectional view showing an example of a sintered body manufactured using the bonding copper paste of the present embodiment. The sintered body 100 of this embodiment is a sintered body of the bonding copper paste of this embodiment, and the first sintered portion 1a and the second metal particles containing a large amount of copper element derived from the copper particles. And a second sintered portion 1b containing a large amount of derived metal elements. According to such a sintered body, a sufficient amount of at least one metal element selected from the group consisting of iron, cobalt, and nickel (a metal element derived from the second metal particles) is present at the bonding interface. Thus, it becomes easier to secure a high bonding strength to the noble metal member. Moreover, when using a sintered compact for joining of a semiconductor element, it exists in the tendency for a semiconductor device to show favorable die shear strength and connection reliability.

  The manufacturing method of the sintered compact of this embodiment is equipped with the process of sintering the copper paste for joining of this embodiment. In this step, for example, the bonding copper paste can be applied to a member and then sintered. Any technique can be used as long as it can deposit a bonding copper paste. Examples of such methods include inkjet printing, super inkjet printing, screen printing, transfer printing, offset printing, jet printing, dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, slit coat, letterpress printing, Intaglio printing, gravure printing, stencil printing, soft lithography, bar coating, applicator, particle deposition method, spray coater, spin coater, dip coater, electrodeposition coating, and the like can be used. The thickness of the bonding copper paste may be 1 μm or more, 5 μm or more, 10 μm or more, or 20 μm or more. Further, the thickness of the bonding copper paste may be 3000 μm or less, 1000 μm or less, 500 μm or less, 300 μm or less, or 250 μm or less, It may be 200 μm or less, or 150 μm or less.

  In the method for producing a sintered body, a magnetic field may be applied to the bonding copper paste before and / or during sintering. FIG. 2 is a schematic cross-sectional view showing an example of a dispersed state of metal particles after the bonding copper paste of this embodiment is applied. FIG. 3 is a schematic cross-sectional view illustrating an example of uneven distribution of metal particles when a magnetic field is applied after the bonding copper paste of this embodiment is applied. As shown in FIG. 2, in the bonding copper paste 200 to which no magnetic field is applied, the sub-micro copper particles 2, the micro-copper particles 3, and the second metal particles 4 are present almost uniformly dispersed. . Here, when the second metal particle is a magnetic metal particle, the second metal particle 4 is unevenly distributed on the surface side where the magnet is brought closer by bringing the magnet 5 closer to the bonding copper paste 210 as shown in FIG. Can be made. By sintering the bonding copper paste in which the second metal particles are unevenly distributed in this way, at least one metal element selected from the group consisting of iron, cobalt, and nickel (derived from the second metal particles). A sintered body 100 in which (metal element) is unevenly distributed (segregated) can be obtained.

  Examples of the method for applying the magnetic field include a magnet and an electromagnet. Magnets include alnico magnet, KS steel, MK steel, ferrite magnet, samarium cobalt magnet, neodymium magnet, praseodymium magnet, neodymium / iron / boron magnet, samarium iron nitride magnet, ferromagnetic iron nitride, platinum magnet, cerium / cobalt magnet, etc. Can be used.

  Since the application of the magnetic field needs to move the second metal particles in the bonding copper paste, it is preferable that the bonding copper paste be fluidized. The magnetic field can be applied before and / or during sintering. From the above viewpoint, it is preferable to apply the magnetic field before drying or sintering the bonding copper paste. When the heat resistance of a magnet, an electromagnet or the like for applying a magnetic field is sufficiently high, the bonding copper paste may be dried or sintered in a state where a magnetic field is applied. At this time, a mechanism for applying a magnetic field may be attached to a part of the jig for manufacturing the sintered body.

  The strength or time of the magnetic field to be applied is not particularly limited as long as the second metal particles are unevenly distributed. The strength or time of the magnetic field may be adjusted so as to have a desired uneven distribution amount according to the residual magnetic flux density, particle diameter, content, etc. of the second metal particles. Also, the shape and size of the magnet, electromagnet, etc. are not particularly limited. When manufacturing a bonded body or a semiconductor device using the sintered body according to the present embodiment, the larger the contact area between the member to be bonded and the second metal particle, the better the bonding strength and connection reliability. It is preferable to use a magnet, an electromagnet or the like having a larger area than the members to be joined.

  The applied bonding copper paste may be appropriately dried from the viewpoint of suppressing flow and void generation during sintering. The gas atmosphere at the time of drying may be air, an oxygen-free atmosphere such as nitrogen or a rare gas, or a reducing atmosphere such as hydrogen or formic acid. The drying method may be drying at room temperature, drying by heating, or drying under reduced pressure. For heat drying or reduced pressure drying, for example, hot plate, hot air dryer, hot air heating furnace, nitrogen dryer, infrared dryer, infrared heating furnace, far infrared heating furnace, microwave heating device, laser heating device, electromagnetic A heating device, a heater heating device, a steam heating furnace, a hot plate press device, or the like can be used. The drying temperature and time may be appropriately adjusted according to the type and amount of the dispersion medium used. As the drying temperature and time, for example, the drying may be performed at 50 ° C. or higher and 180 ° C. or lower for 1 minute or longer and 120 minutes or shorter.

  Sintering is performed by heat-treating the bonding copper paste. For the heat treatment, for example, hot plate, hot air dryer, hot air heating furnace, nitrogen dryer, infrared dryer, infrared heating furnace, far infrared heating furnace, microwave heating device, laser heating device, electromagnetic heating device, A heater heating device, a steam heating furnace, or the like can be used.

  The gas atmosphere at the time of sintering may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the sintered body, the first member, and the second member. The gas atmosphere at the time of sintering may be a reducing atmosphere from the viewpoint of removing the surface oxides of the copper particles of the bonding copper paste. Examples of the oxygen-free atmosphere include introduction of oxygen-free gas such as nitrogen and rare gas, or under vacuum. Examples of the reducing atmosphere include pure hydrogen gas, hydrogen and nitrogen mixed gas typified by forming gas, nitrogen containing formic acid gas, hydrogen and rare gas mixed gas, and rare gas containing formic acid gas. Can be mentioned.

  The maximum temperature reached during the heat treatment may be 250 ° C. or higher and 450 ° C. or lower, from the viewpoint of reducing thermal damage to the first member and the second member and improving the yield, and may be 250 ° C. or higher and 400 ° C. or lower. Or 250 ° C. or more and 350 ° C. or less, or 250 ° C. or more and 300 ° C. or less.

  The ultimate temperature holding time may be 1 minute or more and 60 minutes or less, 1 minute or more and less than 40 minutes, or 1 minute from the viewpoint of volatilizing all the dispersion medium and improving the yield. It may be less than 30 minutes.

  FIG. 4 is a schematic cross-sectional view showing an example of a joined body manufactured using the joining copper paste of the present embodiment. The joined body 300 of this embodiment includes a first member 6 having a first base portion 6a and a first metal layer 6b, and a second member 7 having a second base portion 7a and a second metal layer 7b. And a sintered body 100 that joins the first member and the second member. The sintered body 100 includes a first sintered part 1a containing a large amount of copper element and a second sintered part 1b containing more metal elements derived from the second metal particles than the first sintered part 1a. Have

  Examples of the first member 6 and the second member 7 include semiconductors such as IGBT, diode, Schottky barrier diode, MOS-FET, thyristor, logic circuit, sensor, analog integrated circuit, LED, semiconductor laser, and transmitter. Examples include elements, lead frames, metal plate-attached ceramic substrates (for example, DBC), semiconductor element mounting base materials such as LED packages, copper ribbons, metal blocks, terminals and other power supply members, heat sinks, water cooling plates, and the like.

  The first member 6 and the second member 7 include a first metal layer 6b and a first metal layer 6b that form a metal bond with the sintered body 100 of the bonding copper paste on a surface in contact with the sintered body 100 of the bonding copper paste. A second metal layer 7b can be provided. As a metal which comprises the 1st metal layer 6b and the 2nd metal layer 7b, copper, nickel, silver, gold | metal | money, palladium, platinum, lead, tin, cobalt etc. are mentioned, for example. These metals may be used individually by 1 type, and may be used in combination of 2 or more type. The first metal layer 6b and the second metal layer 7b may be an alloy containing the above metal. Examples of the metal used for the alloy include zinc, manganese, aluminum, beryllium, titanium, chromium, iron, and molybdenum in addition to the above metals. Examples of the member having the first metal layer 6b and the second metal layer 7b include a member having various metal plating, a wire, a chip having metal plating, a heat spreader, a ceramic substrate to which a metal plate is attached, and various metals. Examples thereof include a lead frame having plating, a lead frame made of various metals, a copper plate, and a copper foil.

  The die shear strength of the joined body may be 10 MPa or more, 15 MPa or more, 20 MPa or more, or 30 MPa from the viewpoint of sufficiently joining the first member and the second member. It may be the above. The die shear strength can be measured using a universal bond tester (4000 series, manufactured by DAGE) or the like.

  The thermal conductivity of the sintered copper paste for bonding may be 100 W / (m · K) or more, or 120 W / (m · K) or more, from the viewpoint of heat dissipation and connection reliability at high temperatures. It may be 150 W / (m · K) or more. The thermal conductivity can be calculated from the thermal diffusivity, specific heat capacity, and density of the sintered body of the bonding copper paste.

  Hereinafter, the manufacturing method of the joined body using the copper paste for joining of this embodiment is demonstrated.

  In the manufacturing method of the joined body using the joining copper paste of the present embodiment, the joining copper paste and the second member are arranged in this order on the first member, the direction in which the weight of the first member works. A laminated body is prepared, and the bonding copper paste is sintered in a state where it receives the weight of the first member or the weight of the first member and a pressure of 0.01 MPa or less. The direction in which the weight of the first member works can also be said to be the direction in which gravity works.

  The laminated body is prepared by, for example, providing the bonding copper paste of the present embodiment on a necessary portion of the second member described above, and then arranging the first member described above on the bonding copper paste. Can do.

  As a method of providing the bonding copper paste of the present embodiment on a necessary portion of the second member, any method can be used as long as the bonding copper paste can be deposited. As such a method, the coating method described above can be used.

  The joining copper paste provided on the second member may apply a magnetic field before and / or during sintering. The condition for applying the magnetic field can be the same as the method for applying the sintered body described above. In addition, from the viewpoint that the first member to be joined and / or the second member and the second metal particles can easily secure more contacts, the magnetic field in a state where the member to be joined and the joining copper paste are in contact with each other. It is preferable that the second metal particles are unevenly distributed by applying.

  The magnetic field may be applied so that the second metal particles are unevenly distributed in the vicinity of the interface between the first member and the bonding copper paste and in the vicinity of the interface between the second member and the bonding copper paste. In this case, for example, magnets may be arranged on both sides of the first member side and the second member side so as to be parallel to the member. From the viewpoint of improving the bondability of the sintered body to a member of a noble metal (Au, Ag, etc.), in the first member or the second member, one member is a noble metal and the other member is a base metal (Ni, In the case of Cu or the like, it is preferable that the second metal particles are unevenly distributed on the noble metal member side.

  The bonding copper paste provided on the second member may be appropriately dried from the viewpoint of suppressing flow during sintering and generation of voids. As drying conditions, conditions equivalent to the above-described method for drying a sintered body can be used.

  Examples of the method for arranging the first member on the bonding copper paste include a chip mounter, a flip chip bonder, a positioning jig made of carbon or ceramics.

  By sintering the laminated body, the bonding copper paste is sintered. As the sintering conditions, conditions equivalent to the above-described sintered body sintering method can be used.

  When the laminate is sintered by using the bonding copper paste of the present embodiment, the bonded body can have sufficient bonding strength even if the adherend surface contains a noble metal. That is, sufficient bonding strength in a state in which only the own weight of the first member laminated on the bonding copper paste or the pressure of 0.01 MPa or less, preferably 0.005 MPa or less, in addition to the own weight of the first member. Can be obtained. If the pressure applied during the sintering is within the above range, a special pressurizing device is not required, and the void reduction, die shear strength and connection reliability can be further improved without impairing the yield. Examples of the method for receiving the pressure of the bonding copper paste of 0.01 MPa or less include a method of placing a weight on the first member.

  In the joined body, at least one of the first member and the second member may be a semiconductor element. Examples of the semiconductor element include a power module including a diode, a rectifier, a thyristor, a MOS gate driver, a power switch, a power MOSFET, an IGBT, a Schottky diode, and a fast recovery diode, a transmitter, an amplifier, and an LED module. In such a case, the joined body is a semiconductor device. The obtained semiconductor device can have sufficient die shear strength and connection reliability.

  FIG. 5 is a schematic cross-sectional view showing an example of a semiconductor device manufactured using the bonding copper paste of this embodiment. A semiconductor device 400 shown in FIG. 5 includes a metal layer 9b and a base portion 9a connected to a lead frame 8 having a metal layer 8b and a base portion 8a via a sintered body 100 of a bonding copper paste according to this embodiment. And a mold resin 12 for molding them. The semiconductor element 9 is connected to a lead frame 10 having a metal layer 10b and a base portion 10a through a wire 11.

  As a semiconductor device manufactured using the bonding copper paste of this embodiment, for example, a power composed of a diode, a rectifier, a thyristor, a MOS gate driver, a power switch, a power MOSFET, an IGBT, a Schottky diode, a fast recovery diode, and the like. Examples include modules, transmitters, amplifiers, high-brightness LED modules, sensors, and the like.

  The semiconductor device can be manufactured in the same manner as the above-described manufacturing method of the joined body. That is, the method for manufacturing a semiconductor device uses a semiconductor element as at least one of the first member and the second member, and the first member and the copper paste for bonding on the side in which the weight of the first member acts. And a laminated body in which the second member is laminated in this order, and the bonding copper paste is subjected to the weight of the first member or the weight of the first member and the pressure of 0.01 MPa or less. A step of sintering. For example, a step of providing a bonding copper paste on the lead frame 8 and arranging and heating the semiconductor element 9 can be mentioned. The obtained semiconductor device can have sufficient die shear strength and connection reliability even when bonding is performed without applying pressure. Moreover, even when the semiconductor element includes a deposition surface containing a noble metal, the obtained semiconductor device can have sufficient die shear strength and connection reliability. The semiconductor device of the present embodiment has a sufficient bonding strength, and has a copper sintered body having a high thermal conductivity and a high melting point, thereby having a sufficient die shear strength, excellent connection reliability, and a power cycle. It can be excellent in tolerance.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Each characteristic in each example and comparative example was measured by the following method.
(1) Die shear strength Copper paste is placed on a copper plate (19 × 25 × 3 mm ³ ) on a stainless steel plate with a thickness of 100 μm, a metal mask having 3 × 3 mm square openings in 3 rows and 3 columns, and a stencil using a metal squeegee It was applied by printing. Place a silicon chip (area 3mm x 3mm, thickness 400μm, with a gold plating layer, silver plating layer, or nickel plating layer on the copper paste) on the applied copper paste and lightly press with tweezers A laminate was obtained. If necessary, a neodymium magnet (made by Magfine Co., Ltd., cylindrical shape, φ20 mm × height 20 mm, surface magnetic flux density 531.2 mT, adsorption force 13.8 kgf) is brought close to the chip in parallel with the chip after chip mounting. The second metal particles in the copper paste were unevenly distributed on the chip side, and then the neodymium magnet was removed. The laminated body was set in a tube furnace (manufactured by Aveishi Co., Ltd.), and after argon gas was flowed at 3 L / min to replace air with argon gas, the temperature was raised for 30 minutes while flowing hydrogen gas at 300 mL / min, 300 ° C., Sintering was performed for 30 minutes to obtain a joined body in which a copper plate and a silicon chip were joined together by a sintered body. The argon gas was changed to 0.3 L / min and cooled, and when the temperature became 50 ° C. or lower, the joined body was taken out into the air.

  The adhesive strength of the joined body was evaluated by die shear strength. Using a universal bond tester (4000 series, manufactured by DAGE) equipped with a 1 kN load cell, the silicon chip was pushed in the horizontal direction at a measurement speed of 500 μm / s and a measurement height of 100 μm, and the die shear strength of the joined body was measured. The average value of the values measured for the eight bonded bodies was taken as the die shear strength.

(2) Density of sintered body An opening of 15 × 15 mm ² was provided in a polytetrafluoroethylene plate having a thickness of 1 mm. The polytetrafluoroethylene plate was placed on a glass plate, the opening was filled with copper paste, and the copper paste overflowing from the opening was removed with a metal squeegee. Remove the polytetrafluoroethylene plate, set the glass plate on which the copper paste is laminated in a tube furnace, heat at 150 ° C while flowing argon gas at 0.3 L / min, and hold for 1 hour to remove the dispersion medium did. Thereafter, the gas was changed to 300 mL / min of hydrogen gas, the temperature was raised to 300 ° C., and sintering was performed for 60 minutes. Thereafter, the hydrogen gas was changed to 0.3 L / min of argon gas and cooled. When the temperature became 50 ° C. or lower, the glass plate was taken out into the air. The plate-like sintered body was peeled from the glass plate and polished with a sandpaper (# 800) to obtain a plate-like sample having a size of 10 × 10 mm ^{2 and} a flat surface. The length, width, and thickness of the plate sample were measured, and the weight of the plate sample was measured. The density of the plate sample was calculated from these values.

(3) Thermal conductivity The thermal diffusivity was measured by the laser flash method (LFA467, manufactured by Netch) using the plate-like sample prepared by “(2) Density of copper sintered body”. From the product of this thermal diffusivity, the specific heat capacity obtained with a differential scanning calorimeter (DSC8500, manufactured by PerkinElmer) and the density determined in “(2) Density of sintered body”, copper firing at 25 ° C. The thermal conductivity [Wm ⁻¹ K ⁻¹ ] of the bonded body was calculated.

[Example 1]
The bonding copper paste was prepared according to the formulation in Table 1. Α-Terpineol (manufactured by Wako Pure Chemical Industries, Ltd.) and isobornylcyclohexanol (MTPH, manufactured by Nippon Terpene) were mixed as a dispersion medium. There, MA-C025KFD (50% volume average particle size 5 μm, manufactured by Mitsui Kinzoku Co., Ltd.) as micro copper particles, CH-0200 (50% volume average particle size 0.36 μm, manufactured by Mitsui Kinzoku Co., Ltd.), Iron powder (50% volume average particle diameter 45 μm, manufactured by Wako Pure Chemical Industries, Ltd.) was weighed and added as second metal particles, and mixed for 5 minutes in an automatic mortar. After the mixture was transferred to a plastic bottle, a joining copper paste composition was obtained by applying it to a stirrer manufactured by Shinky Corporation (Awatori Netaro ARE-310) under reduced pressure at 2000 rpm for 2 minutes. Various measurements and analyzes were performed using this copper paste. The die shear strength was measured under the condition that a magnetic field was applied after chip mounting. The evaluation results are shown in Table 3. In addition, the uneven distribution (segregation) of the metal originating in the 2nd metal particle in the sintered compact of the copper paste for joining by the application of a magnetic field was confirmed by EDX analysis.

[Example 2]
The copper paste of Example 1 was used, and the copper paste was joined without applying a magnetic field after chip mounting. The evaluation results are shown in Table 3.

[Examples 3 to 5]
A copper paste was obtained in the same manner as in Example 1 except that the amount of iron particles added was changed as the second metal particles. The recipe for the copper paste is shown in Table 1. The die shear strength was measured under the condition that a magnetic field was applied after chip mounting. The evaluation results are shown in Table 3.

[Example 6]
A copper paste was obtained in the same manner as in Example 1 except that cobalt powder Cobalt Powder S-160 (50% volume average particle size 3.0 μm, manufactured by Freeport Cobalt) was used as the second metal particles. The recipe for the copper paste is shown in Table 1. The die shear strength was measured under the condition that a magnetic field was applied after chip mounting. The evaluation results are shown in Table 3.

[Example 7]
The copper paste of Example 6 was used, and the copper paste was joined without applying a magnetic field after chip mounting. The evaluation results are shown in Table 3.

[Examples 8 to 10]
The same as Example 1 except that cobalt powder Cobalt Powder S-160 (50% volume average particle size 3.0 μm, manufactured by Freeport Cobalt) was used as the second metal particle, and the addition amount of cobalt powder was changed. A copper paste was obtained. The recipe for the copper paste is shown in Table 1. The die shear strength was measured under the condition that a magnetic field was applied after chip mounting. The evaluation results are shown in Table 3.

[Example 11]
A copper paste was obtained in the same manner as in Example 1 except that nickel particles (50% volume average particle size 1.5 μm, manufactured by METAL FOIL & POWDERS MFG CO.) Were used as the second metal particles. The recipe for the copper paste is shown in Table 1. The die shear strength was measured under the condition that a magnetic field was applied after chip mounting. The evaluation results are shown in Table 3.

[Example 12]
The copper paste of Example 11 was used, and the copper paste was joined without applying a magnetic field after chip mounting. The evaluation results are shown in Table 3.

[Examples 13 to 15]
Except that nickel particles (50% volume average particle size 1.5 μm, manufactured by METAL FOIL & POWDERS MFG CO.) Were used as the second metal particles, and the addition amount of nickel particles was changed, the same as in Example 1. A copper paste was obtained. The recipe for the copper paste is shown in Table 1. The die shear strength was measured under the condition that a magnetic field was applied after chip mounting. The evaluation results are shown in Table 3.

[Comparative Example 1]
A copper paste was obtained in the same manner as in Example 1 except that the second metal particles were not added. The recipe for the copper paste is as shown in Table 2. The evaluation results are shown in Table 4.

[Comparative Examples 2 to 4]
A copper paste was obtained in the same manner as in Example 1 except that the amount of iron particles added was changed as the second metal particles. The recipe for the copper paste is as shown in Table 2. The evaluation results are shown in Table 4.

[Comparative Examples 5 to 7]
A copper paste was obtained in the same manner as in Example 1 except that the addition amount of cobalt powder was changed as the second metal particles. The recipe for the copper paste is as shown in Table 2. The evaluation results are shown in Table 4.

[Comparative Examples 8 to 10]
A copper paste was obtained in the same manner as in Example 1 except that the amount of nickel particles added was changed as the second metal particles. The recipe for the copper paste is as shown in Table 2. The evaluation results are shown in Table 4.

DESCRIPTION OF SYMBOLS 1a ... 1st sintered part, 1b ... 2nd sintered part, 2 ... Sub micro copper particle, 3 ... Micro copper particle, 4 ... 2nd metal particle, 5 ... Magnet, 6 ... 1st member, 6a ... first base, 6b ... first metal layer, 7 ... second member, 7a ... second base, 7b ... second metal layer, 8 ... lead frame, 8a ... base, 8b ... metal layer , 9 ... Semiconductor element, 9a ... Base, 9b ... Metal layer, 10 ... Lead frame, 10a ... Base, 10b ... Metal layer, 11 ... Wire, 12 ... Mold resin, 100 ... Sintered body, 200, 210 ... For bonding Copper paste, 300 ... joined body, 400 ... semiconductor device.

Claims (13)

A copper paste for bonding comprising copper particles, second metal particles, and a dispersion medium,
The copper particles include sub-micro copper particles having a volume average particle diameter of 0.12 μm or more and 0.8 μm or less, and micro copper particles having a volume average particle diameter of 2 μm or more and 50 μm or less,
The second metal particles are particles containing at least one metal selected from the group consisting of iron, cobalt, and nickel;
The volume average particle diameter of the second metal particles is 0.01 μm or more and 50 μm or less,
The copper paste for joining whose content of said 2nd metal particle is 0.01 mass% or more and 10 mass% or less on the basis of the sum total of the mass of said copper particle and said 2nd metal particle. A sintered body for joining the first member and the second member,
The sintered body includes a copper element and at least one metal element selected from the group consisting of iron, cobalt, and nickel,
The total content of at least one metal element selected from the group consisting of iron, cobalt, and nickel is 0.01% by mass or more and 10% by mass or less based on the total mass of the sintered body. Sintered body.   The at least one metal element selected from the group consisting of iron, cobalt, and nickel is unevenly distributed on the surface side of the sintered body in contact with the first member and / or the second member. Item 3. A sintered body according to Item 2. A method for producing a sintered body for joining a first member and a second member,
The manufacturing method of a sintered compact provided with the process of sintering the copper paste for joining of Claim 1.   The manufacturing method of the sintered compact of Claim 4 which applies a magnetic field to the said copper paste for joining before the said sintering and / or during the said sintering. A first member, a second member, and a sintered body that joins the first member and the second member;
The sintered body includes a copper element and at least one metal element selected from the group consisting of iron, cobalt, and nickel,
The total content of at least one metal element selected from the group consisting of iron, cobalt, and nickel is 0.01% by mass or more and 10% by mass or less based on the total mass of the sintered body. Joined body.   The at least one metal element selected from the group consisting of iron, cobalt, and nickel is unevenly distributed on the surface side of the sintered body in contact with the first member and / or the second member. Item 7. The joined body according to Item 6.   A first member and a laminated body in which the copper paste for bonding according to claim 1 and the second member are laminated in this order are prepared on the side in which the weight of the first member acts. The manufacturing method of a joined body provided with the process of sintering a copper paste in the state which received the dead weight of said 1st member, or the dead weight of said 1st member, and the pressure of 0.01 Mpa or less.   The method for manufacturing a joined body according to claim 8, wherein a magnetic field is applied to the joining copper paste before and / or during the sintering. A first member, a second member, and a sintered body that joins the first member and the second member;
At least one of the first member and the second member is a semiconductor element,
The sintered body includes a copper element and at least one metal element selected from the group consisting of iron, cobalt, and nickel,
The total content of at least one metal element selected from the group consisting of iron, cobalt, and nickel is 0.01% by mass or more and 10% by mass or less based on the total mass of the sintered body. Semiconductor device.   The at least one metal element selected from the group consisting of iron, cobalt, and nickel is unevenly distributed on the surface side of the sintered body in contact with the first member and / or the second member. Item 11. The semiconductor device according to Item 10. A first member and a laminated body in which the copper paste for bonding according to claim 1 and the second member are laminated in this order are prepared on the side in which the weight of the first member acts. Sintering the copper paste in a state of receiving the weight of the first member or the weight of the first member and a pressure of 0.01 MPa or less,
A method for manufacturing a semiconductor device, wherein at least one of the first member and the second member is a semiconductor element.   The method of manufacturing a semiconductor device according to claim 12, wherein a magnetic field is applied to the bonding copper paste before and / or during the sintering.

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