JP6061427B2 - Electronic component bonding material, bonding composition, bonding method, and electronic component - Google Patents

Description

  The present invention relates to a bonding material and a bonding composition used for bonding electronic components such as semiconductor devices, a method for bonding electronic components using them, and electronic components such as semiconductor devices manufactured using them.

  As an energy conversion device that enables energy saving, for example, SiC semiconductors are attracting attention in the field of power devices. With the advancement of SiC single crystal quality and device technology, practical application of SiC semiconductor devices is finally being realized. Since this SiC semiconductor has a large band gap, the SiC semiconductor device itself is characterized in that it can be used at high voltage and high temperature for automobiles and transportation equipment. However, a sufficient study has not been made on the mounting technology required for actual use as a device.

  The conventional mounting technique assumes a Si device and has not been assumed to be used in a high temperature environment of, for example, 150 ° C. or higher. For this reason, there has been a demand for a bonding technique such as die bonding for high-temperature applications that cannot be used with conventional Si devices such as automobiles. For the application of die bonding materials to high-temperature packaging, first of all, by using nanoparticles as the high melting point material, it becomes surface active at low temperatures, and the characteristics of particle bonding, grain growth, and reaction with the surface to be joined are utilized. I pay attention to it. However, sufficient research has not been conducted on the bonding process of the nanoparticles. There are few reports on metals other than precious metals.

  In actual handling of nanoparticles, exposure to the atmosphere is inevitable, so it is proposed to perform surface treatment with organic substances, for example, at room temperature to prevent reaction with oxygen in the atmosphere. (For example, Patent Documents 1 and 2). Although it is necessary for these organic substances to decompose and disappear at the bonding temperature, there is a concern that it may cause voids when gasified. Also, from another viewpoint of practical use, the price of the bonding material is also important. Under such circumstances, Ag nanoparticles have been mainly studied so far as a die bonding material capable of being sintered at a low temperature. However, Ag has problems such as corrosion and migration caused by heating, and a problem of high cost, and has not been put into practical use.

JP 2004-107728 A JP 2008-161197 A

  As described above, SiC semiconductors are semiconductors that can be used at high temperatures instead of conventional Si semiconductors, but efforts to solve the problems of high-temperature mounting technology are still insufficient. Conventionally, low melting point metals such as solder materials have been used for die bonding. Solder materials can be bonded at low temperatures, but their melting points are low, so that devices used in high temperature environments cannot be bonded. On the other hand, a high melting point Ni brazing material or the like needs to be heated to about 800 ° C. or more. At this temperature, the heat resistance of peripheral materials is not sufficient even when mounting a SiC semiconductor, and the high temperature heat resistance of electrode materials and the like is also low. Not enough. Therefore, there has been a demand for a refractory metal bonding material that can be bonded at a temperature of about 450 ° C. or lower. As the material for such a bonding material, the present inventors have conceived of using Ni that is relatively inexpensive and has corrosion resistance and heat resistance. However, Ni fine particles having a particle size of 100 nm or less have a problem that the surface free energy is large, aggregation is likely to occur, and usability is poor.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a bonding material for electronic parts having good usability by using a Ni material which is cheaper than Ag and can be used at a high temperature. That is.

The bonding material for electronic components of the present invention is a bonding material for electronic components used for bonding electronic components,
Comprising metal fine particles composed of a metal selected from the group consisting of Ni and Ni alloys, and an oxygen-containing film covering the metal fine particles, and comprising metal nanoparticles having an average particle diameter of 100 nm or less To do.

  In the bonding material for electronic parts of the present invention, the oxygen-containing film may be an oxide film or a hydroxide film having a thickness in the range of 1 nm to 8 nm.

  In the electronic component bonding material according to the present invention, the metal nanoparticles may further include a reductive organic film of one or more molecular films that further coats the outer side of the oxygen-containing film. In this case, the reducing organic substance may be an amine compound.

  The bonding material for electronic parts of the present invention contains carbon in the range of 0.1 wt% to 5.0 wt% and oxygen in the range of 0.5 wt% to 10.0 wt%. It may be a thing.

  In the bonding material for electronic parts according to the present invention, the coefficient of variation CV of the particle diameter of the metal fine particles may be 0.2 or less.

  In the bonding material for electronic parts according to the present invention, the metal nanoparticles may include 5% or more of particles having a particle diameter in the range of 10 nm to 100 nm.

  In the bonding material for electronic parts according to the present invention, the metal nanoparticles may contain 40% or more of particles having a particle diameter in the range of 50 nm to 100 nm.

  In the bonding material for electronic parts according to the present invention, the metal nanoparticles may contain 40% or more of the particles having a particle diameter in the range of 10 nm to 50 nm.

  Moreover, the bonding material of the electronic component of the present invention may have a crystallite diameter of the metal fine particles measured by X-ray diffraction of 30 nm or less.

  Further, the electronic material bonding material of the present invention may be one in which the metal nanoparticles are synthesized by a wet microwave irradiation method.

  The composition for joining electronic components of the present invention contains any of the above-described joining materials for electronic components and a volatile solution, and the joining material is dispersed in the volatile solution.

  In addition, the composition for joining electronic components of the present invention may be in the form of a slurry or a paste.

  The electronic component of the present invention is formed by forming a joint portion using any one of the above-described joining materials. In this case, the joining portion may be formed between the back surface of the semiconductor element and the substrate, between the semiconductor electrode and the substrate electrode, or between the semiconductor electrode and the semiconductor electrode.

  The electronic component of the present invention may be bonded through a heating process of 200 ° C. or higher and 450 ° C. or lower.

  The electronic component bonding method of the present invention is to perform bonding by heating a bonding material for any of the above electronic components to a temperature of 200 ° C. or higher and 450 ° C. or lower.

  Since the bonding material of the electronic component of the present invention includes metal nanoparticles having an oxygen-containing coating covering metal fine particles selected from the group consisting of Ni and Ni alloys, the surface free energy is suppressed to be small, and the metal fine particles are aggregated. Hard to occur. Moreover, since the metal nanoparticles used for the bonding material of the present invention are mainly composed of Ni or Ni alloy, they are less expensive than Ag, have excellent heat resistance, and are less likely to cause migration. Furthermore, since the metal nanoparticles used for the bonding material of the present invention have an average particle diameter of 100 nm or less, the metal nanoparticles can be bonded at a temperature of about 450 ° C. or less, and sufficient bonding strength can be obtained. Therefore, the bonding material of the present invention has high utility value for bonding electronic parts such as semiconductor devices.

It is sectional drawing explaining the structure of Ni nanoparticle of one embodiment of this invention. It is sectional drawing explaining the structure of Ni nanoparticle of another embodiment of this invention. It is drawing explaining the die-bonding process as an example of joining of the electronic component by the joining material of this invention. It is sectional drawing explaining the structure of the dummy chip used for the test example. It is drawing explaining the joining method in a test example. It is a graph which shows the result of the die share test in a test example. It is an image which shows the observation result of the junction part in the test example using Ni particle | grains with an average particle diameter of 20 nm. It is an image which shows the observation result of the junction part in the test example which uses Ni particle | grains with an average particle diameter of 100 nm. It is an image which shows the example of the fracture surface of the junction part in a test example.

[Bonding material]
The bonding material of the electronic component according to the present embodiment has an average particle diameter of 100 nm or less, and contains Ni or Ni alloy fine particles (hereinafter, these may be collectively referred to simply as “metal particles”). It contains metal nanoparticles with a coating. FIG. 1 shows a cross-sectional structure of Ni nanoparticles 1 as “metal nanoparticles” according to an embodiment of the present invention. The Ni nanoparticle 1 includes an oxygen-containing film 5 on the surface of the metal particle 3. FIG. 2 shows a cross-sectional structure of Ni nanoparticles 1A as “metal nanoparticles” according to another embodiment of the present invention. This Ni nanoparticle 1 </ b> A includes a metal particle 3, an oxygen-containing film 5, and a reducing organic material film 7 of one molecular film or more that covers the outside of the oxygen-containing film 5. The Ni nanoparticles 1 and 1A can be used as they are as bonding materials for electronic components.

<Metal particles>
The metal particles 3 are Ni or Ni alloy fine particles. When Ni alloy is used, it contains one or more metals selected from Au, Ag, Pt, Pd, etc. as a metal other than Ni from the viewpoint of controlling the particle diameter of fine particles or adjusting the sintering temperature. May be. Further, the Ni alloy may contain Cu and Al as metals other than nickel from the viewpoint of improving the conductivity of Ni and softening it to relieve stress and reduce defects such as cracks.

  From the viewpoint of improving sinterability, the metal particles 3 preferably have a crystallite diameter of Ni or Ni alloy measured by X-ray diffraction of 30 nm or less. If the crystallite diameter exceeds 30 nm, the sintering temperature increases and the adhesive strength may decrease, which is not preferable.

  In the Ni nanoparticles 1 and 1A, if the particle size of the metal particles 3 is small, it is easy to sinter by heating at the time of joining, but there is a drawback that oxygen is easily taken up. On the other hand, when the particle diameter of the metal particles 3 is large, it is difficult to sinter at the time of heating, but there is an aspect in which oxygen uptake can be suppressed. Moreover, it is preferable to combine a thing with a large particle diameter and a small thing as the metal particle 3 used for Ni nanoparticle 1 and 1A also from a viewpoint of raising the density as a joining material and improving adhesiveness more.

  Moreover, when using the metal particle 3 whose particle diameter is 50 nm or less, it is preferable that the variation coefficient CV of the particle diameter is 0.2 or less. By setting the coefficient of variation CV to 0.2 or less, the density as the bonding material can be increased, and uniform and less uneven sintering is possible. For this reason, as the metal particles 3, for example, when a particle having a particle size of 50 nm or less and a particle having a particle size of 50 nm or more are combined, the coefficient of variation CV having a particle size of 50 nm or less is preferably 0.2 or less. More preferably, the coefficient of variation CV with a particle size of 50 nm or less is 0.2 or less, and the coefficient of variation CV with a particle size of 50 nm or more is 0.2 or less. When combining different particle diameters, the coefficient of variation CV is set to 0.2 or less, so that it is easy to achieve both improvement in density as a bonding material and improvement in adhesive strength.

  In order to sufficiently increase the shear strength of the joint portion formed by sintering the Ni nanoparticles 1, 1A, it is preferable to include 5% or more of the particles having a particle diameter in the range of 10 nm to 100 nm. . Further, the Ni nanoparticles 1 and 1A include 40% or more of particles having a particle diameter in the range of 50 nm to 100 nm, or 40% or more of particles having a particle diameter in the range of 10 nm to 50 nm. It is more preferable.

<Oxygen-containing film>
The oxygen-containing film 5 formed on the surface of the metal particle 3 is preferably, for example, an oxide film or a hydroxide film. More specifically, a film of, for example, nickel oxide (NiO) or nickel hydroxide (Ni (OH) ₂ ) is formed on the surface of the metal particle 3 as the oxygen-containing film 5. Such an oxygen-containing film 5 may be a film partially present on the surface of the metal particle 3 or a film covering the entire surface of the particle.

  The thickness of the oxygen-containing film 5 is preferably in the range of 1 to 8 nm, for example, from the viewpoint of effectively suppressing aggregation of the metal particles 3. By having the oxygen-containing film 5, the Ni nanoparticles 1 preferably contain oxygen within a range of 0.5 to 10.0% by weight with respect to the total weight. Note that the thickness of the oxygen-containing film 5 is determined by observing the surface of the randomly extracted 200 metal particles 3 with a transmission electron microscope with an acceleration voltage of 300 KV and distinguishing the metal particles 3 from the lattice spacing with a high contrast. The length from the end that can be formed to the end of the portion with low contrast is measured, and the average of the measurement results of the ten metal particles 3 is taken as the thickness of the film.

<Reducing organic film>
In the Ni nanoparticles 1A, the reducing organic film 7 has an action of reducing the oxygen-containing film 5 under the heating condition during bonding and ensuring the conductivity of the bonding portion (metal bonding layer). Examples of the reducing organic material constituting the reducing organic material film 7 include amine compounds and carboxylic acids. More specifically, examples of the amine compound include oleylamine, octylamine, trioctylamine, dioctylamine, hexadecylamine, dodecylamine, tetradecylamine, stearylamine, myristylamine, laurylamine and the like. Examples of the carboxylic acid include formic acid, oxalic acid, citric acid, ascorbic acid, and abietic acid. The Ni nanoparticle 1A has the oxygen-containing film 5 and the reducing organic film 7, so that oxygen is in the range of 0.5 to 10.0% by weight and carbon is in the range of 0.1 to 5. The content is preferably within the range of 0% by weight. By setting the content of oxygen and carbon within the above range, aggregation of the Ni nanoparticles 1A can be suppressed and the adhesive strength can be improved. Further, when the oxygen content exceeds the upper limit, the sintering temperature of the Ni nanoparticles 1A tends to increase, and when the carbon content exceeds the upper limit, the Ni nanoparticles 1A are sintered. Carbon tends to remain in the metal bonding layer after bonding, and the adhesive strength tends to decrease.

[Production method]
The Ni nanoparticles 1, 1A are preferably synthesized by reducing metal ions (or metal compounds) by a wet microwave irradiation method. Hereinafter, a preferred method for producing the Ni nanoparticles 1, 1A will be exemplified.

  The method for producing Ni nanoparticles 1 and 1A includes a first step of obtaining a complexing reaction solution in which a nickel complex is formed by heating a mixture containing nickel carboxylate (nickel carboxylate) and a primary amine; A second step of heating the complexing reaction liquid with microwaves to obtain a nickel nanoparticle slurry. In the first step, heating can be performed at a temperature in the range of 105 ° C. or higher and 160 ° C. or lower. In the second step, microwaves can be irradiated and heated at a temperature of 160 ° C. or higher, preferably 180 ° C. or higher.

<First step>
In the first step, a complexing reaction solution is obtained by heating a mixture containing nickel carboxylate and primary amine.

(Nickel carboxylate)
The nickel carboxylate (nickel salt of carboxylic acid) is not limited to the type of carboxylic acid. For example, the carboxy group may be one monocarboxylic acid, and the carboxy group has two or more carboxylic acids. It may be an acid. Moreover, acyclic carboxylic acid may be sufficient and cyclic carboxylic acid may be sufficient. As nickel carboxylate, for example, nickel formate having a low reduction temperature (reduction temperature; 190 to 200 ° C.) is preferably used. The nickel carboxylate may be an anhydride or a hydrate. In addition, it is possible to use inorganic salts such as nickel chloride, nickel nitrate, nickel sulfate, nickel carbonate, nickel hydroxide instead of nickel carboxylate, but in the case of inorganic salts, dissociation (decomposition) is high temperature. In the reduction process, heating at high temperature is necessary, which is not preferable. It is also possible to use nickel salts composed of organic ligands such as Ni (acac) ₂ (β-diketonato complex) and stearate ions, but using these nickel salts increases the cost of raw materials. It is not preferable.

(Primary amine)
The primary amine can form a complex with nickel ions, and effectively exhibits a reducing ability for nickel complexes (or nickel ions). On the other hand, secondary amines have great steric hindrance and may hinder good formation of nickel complexes, and tertiary amines cannot be used because they do not have the ability to reduce nickel ions.

  The primary amine is not particularly limited as long as it can form a complex with nickel ions, and can be solid or liquid at room temperature. Here, room temperature means 20 ° C. ± 15 ° C. The primary amine that is liquid at room temperature also functions as an organic solvent for forming the nickel complex. In addition, even if it is a primary amine solid at normal temperature, there is no particular problem as long as it is liquid by heating at 100 ° C. or higher, or can be dissolved using an organic solvent.

  The primary amine also functions as a dispersant, and the nickel complex can be well dispersed in the reaction solution. Therefore, the particles when the Ni complex 1, 1A is obtained by thermally decomposing the nickel complex after forming the complex. Aggregation can be suppressed. The primary amine may be an aromatic primary amine, but an aliphatic primary amine is preferred from the viewpoint of easy nickel complex formation in the reaction solution. Aliphatic primary amines can control the particle size of the produced nanoparticles, for example, by adjusting the length of the carbon chain, and in particular, produce Ni nanoparticles 1, 1A having an average particle size of 10 to 100 nm. This is advantageous. From the viewpoint of controlling the particle size of the Ni nanoparticles 1 and 1A, the aliphatic primary amine is preferably selected from those having about 6 to 20 carbon atoms. The larger the number of carbons, the smaller the particle size of the resulting nanoparticles. Examples of such amines include octylamine, trioctylamine, dioctylamine, hexadecylamine, dodecylamine, tetradecylamine, stearylamine, oleylamine, myristylamine, and laurylamine. For example, oleylamine exists in a liquid state under the temperature conditions in the nanoparticle production process, and therefore can efficiently proceed with a reaction in a homogeneous solution.

Since the primary amine forms a reducing organic film 7 having a function as a surface modifier when the metal particles 3 are generated, secondary aggregation can be suppressed even after removal of the primary amine. The primary amine is also preferable from the viewpoint of ease of processing operation in the washing step of separating the solid component of the produced Ni nanoparticles 1, 1A and the solvent or unreacted primary amine after the reduction reaction. Further, the primary amine preferably has a boiling point higher than the reduction temperature from the viewpoint of ease of reaction control when the nickel complex is reduced to obtain the Ni nanoparticles 1, 1A. That is, the aliphatic primary amine preferably has a boiling point of 180 ° C. or higher, more preferably 200 ° C. or higher. The aliphatic primary amine preferably has 9 or more carbon atoms. Here, for example, the boiling point of C ₉ H ₂₁ N (nonylamine) of an aliphatic amine having 9 carbon atoms is 201 ° C. The amount of primary amine is preferably 2 mol or more, more preferably 2.2 mol or more, and more preferably 4 mol or more with respect to 1 mol of nickel in terms of metal contained in nickel carboxylate. When the amount of primary amine is less than 2 mol, it is difficult to control the particle diameter of the obtained Ni nanoparticles 1 and 1A, and the particle diameter tends to vary. The upper limit of the amount of primary amine is not particularly limited. For example, from the viewpoint of productivity, the amount is preferably about 20 mol or less with respect to 1 mol of metal in terms of metal contained in nickel carboxylate.

A divalent nickel ion is known as a ligand-substituted active species, and the ligand of the complex to be formed may easily change in complex formation by ligand exchange depending on temperature and concentration. For example, in the second step of obtaining a complexing reaction solution by heating a mixture of nickel carboxylate and primary amine, steric hindrance such as carbon chain length of the amine to be used is considered, and carboxylate ions (R ₁ COO, R ₂ COO) may be coordinated by either bidentate or monodentate coordination, and when the amine concentration is in a large excess, there may be a structure in which carboxylate ions are present in the outer sphere. In order to obtain a homogeneous solution at the target reaction temperature (reduction temperature), at least one of the ligands must be coordinated with a primary amine. In order to take this state, it is necessary that the primary amine is excessively present in the reaction solution, and it is preferable that at least 2 mol per 1 mol of nickel ions is present, and 2.2 mol or more exist. It is more preferable that 4 mol or more is present.

(Complexation reaction solution)
The complexing reaction liquid refers to a reaction product liquid (reaction product) generated by a reaction between nickel carboxylate and a primary amine. Although the complexing reaction can proceed even at room temperature, heating is performed at a temperature of 100 ° C. or higher in order to carry out the reaction reliably and more efficiently. This heating is particularly advantageous when a nickel carboxylate hydrate such as nickel formate dihydrate is used as the nickel carboxylate. The heating temperature is preferably higher than 100 ° C, more preferably 105 ° C or higher. As a result, the ligand substitution reaction between the coordinated water coordinated to nickel carboxylate and the primary amine is efficiently performed, and the water molecule as the complex ligand can be dissociated, and the water is further removed. Since it can be taken out of the system, a complex can be formed efficiently. For example, nickel formate dihydrate has a complex structure in which two coordinated water and two formate ions as bidentate ligands and two water molecules exist in the outer sphere at room temperature. In order to efficiently complex the two coordinated water and the primary amine by ligand substitution, it is preferable to dissociate the water molecule as the complex ligand by heating at a temperature higher than 100 ° C. In addition, the heating temperature is preferably 140 ° C. or lower from the viewpoint of reliably separating from the subsequent heat reduction process by microwave irradiation of the nickel complex (or nickel ion) and completing the complex formation reaction. The inside of the range of 140 degreeC is more preferable, and the inside of the range of 110-130 degreeC is desirable.

  The heating time can be appropriately determined according to the heating temperature and the content of each raw material, but is preferably 15 minutes or longer from the viewpoint of reliably completing the complex formation reaction. Although there is no upper limit on the heating time, heating for a long time is useless from the viewpoint of saving energy consumption and process time. The heating method is not particularly limited, and may be heating by a heat medium such as an oil bath or heating by microwave irradiation.

  The complex formation reaction between nickel carboxylate and primary amine can be confirmed by a change in the color of the solution when a solution obtained by mixing nickel carboxylate and primary amine is heated. In addition, this complex formation reaction is carried out by measuring the maximum absorption wavelength of the absorption spectrum observed in the wavelength region of 300 nm to 750 nm using, for example, an ultraviolet / visible absorption spectrum measuring device, and measuring the maximum absorption wavelength of the raw material (for example, nickel formate 2 In the case of a hydrate, the maximum absorption wavelength is 710 nm.

  After complexation of nickel carboxylate and primary amine is performed, the complexing reaction solution obtained is heated by microwave irradiation as described later, thereby reducing nickel ions of the nickel complex, Carboxylic acid ions coordinated to nickel ions are simultaneously decomposed, and finally metal particles 3 containing nickel having an oxidation number of 0 are generated. In general, nickel carboxylate is hardly soluble under conditions other than using water as a solvent, and a solution containing nickel carboxylate needs to be a homogeneous reaction solution as a pre-stage of the heat reduction reaction by microwave irradiation. On the other hand, the primary amine used in the present embodiment is liquid under the operating temperature conditions, and is considered to be liquefied by coordination with nickel ions to form a homogeneous reaction solution.

(Organic solvent)
In order to proceed the reaction in a homogeneous solution more efficiently, an organic solvent other than the primary amine may be newly added. When an organic solvent is used, the organic solvent may be mixed with the nickel carboxylate and the primary amine. However, when the nickel carboxylate and the primary amine are mixed first and complexed, the organic solvent is added to form the primary amine. Is more preferable because it efficiently coordinates to nickel ions. The organic solvent that can be used is not particularly limited as long as it does not inhibit the complex formation between the primary amine and the nickel ion. For example, the ether-based organic solvent having 4 to 30 carbon atoms, 7 to 30 carbon atoms. Saturated or unsaturated hydrocarbon organic solvents, alcohols having 8 to 18 carbon atoms, and the like can be used. Moreover, from the viewpoint of enabling use even under heating conditions by microwave irradiation, it is preferable to select an organic solvent having a boiling point of 170 ° C. or higher, more preferably in the range of 200 to 300 ° C. It is better to choose one. Specific examples of such an organic solvent include tetraethylene glycol and n-octyl ether.

<Second step>
In this step, the complexing reaction solution is heated at a temperature of 160 ° C. or higher, preferably 180 ° C. or higher by microwaves, whereby the nickel complex (or nickel ions) is reduced to metallic nickel to generate metal particles 3. If the heating temperature is lower than 160 ° C., the nickel complex may not be reduced favorably. By heating the complexing reaction solution with microwaves, the microwave penetrates into the complexing reaction solution, so uniform heating is performed and energy can be directly applied to the medium, so rapid heating is performed. Can do. As a result, the entire complexing reaction solution can be brought to a desired uniform temperature, and the processes of reduction, nucleation, and nucleation of the nickel complex (or nickel ions) are simultaneously generated in the entire solution, and the particle size distribution can be reduced. Narrow monodisperse particles can be easily produced in a short time. Further, in the wet microwave irradiation method, since water molecules exist in the reaction system, the surface of the finally generated metal particles 3 is thinly oxidized to be changed into oxide or hydroxide, and the oxygen-containing film 5 Is formed. The oxygen-containing film 5 can reduce the large surface free energy of the metal particles 3 and prevent the metal particles 3 from aggregating.

  Furthermore, since the primary amine used for the complex formation reaction with nickel ions forms the reductive organic film 7 of the amine compound and forms the Ni nanoparticles 1A when the metal particles 3 are formed, the Ni nanoparticles 1A are aggregated. Is even more suppressed. The reducing organic film 7 reduces the oxides and hydroxides in the oxygen-containing film 5 during the sintering of the Ni nanoparticles 1A during bonding, and conducts the conductive portion (metal bonding layer). It also has the effect of improving the properties.

  Moreover, when forming carboxylic acid (for example, formic acid, oxalic acid, a citric acid, ascorbic acid, abietic acid etc.) on the Ni surface as the reducing organic substance film 7, it is preferable to employ | adopt the method illustrated below. For example, a method in which a carboxylic acid is allowed to coexist in the nickel complex before the reduction reaction of the nickel complex can be mentioned. Further, for example, the Ni nanoparticle 1A having an amine compound coating is dispersed in an organic solvent containing the reducing carboxylic acid (for example, alcohol, hydrocarbon, etc.) and stirred, whereby the amine compound coating is formed into a carboxylic acid. An acid can be substituted. Further, for example, by dispersing Ni nanoparticles 1A having an amine compound coating in an organic solvent and then adding and stirring the reducing carboxylic acid, the amine compound coating can be replaced with carboxylic acid. it can.

  Although there is no upper limit of the heating temperature by microwave irradiation, it is preferable to set it to about 270 ° C. or less, for example, from the viewpoint of efficient processing. The heating time is not particularly limited, and can be, for example, about 2 to 10 minutes. When heating at 250 ° C. or higher for a long time, carbon is dissolved in the produced Ni nanoparticles to form nickel carbide particles, and such nickel carbide particles are not preferable because the sintering temperature becomes excessively high. .

  In addition, the use wavelength of a microwave is not specifically limited, For example, it is 2.45 GHz.

  In order to generate Ni nanoparticles 1 and 1A having a uniform particle size, the nickel complex is uniformly and sufficiently generated in the first step (step in which the nickel complex is generated), and the second step It is necessary to simultaneously generate and grow nickel (zero-valent) nuclei generated by reduction of the nickel complex (or nickel ion) in the process (heating by microwave irradiation). That is, by adjusting the heating temperature of the first step within the above-mentioned specific range and keeping it lower than the heating temperature of the second step, particles having a uniform particle size and shape are easily generated. . For example, if the heating temperature is too high in the first step, the formation of a nickel complex and the reduction reaction to nickel (zero valence) proceed simultaneously, making it difficult to generate particles having a uniform particle shape in the second step. There is a fear. Further, if the heating temperature in the second step is too low, the reduction reaction rate to nickel (zero valence) is slowed, and the generation of nuclei is reduced, so that not only the particles are enlarged but also the Ni nanoparticles 1, 1A are collected. It is not preferable also in terms of rate.

  The slurry of the metal particles 3 obtained by heating by microwave irradiation is, for example, left and separated, and after removing the supernatant, washed with an appropriate solvent, and dried to obtain the metal particles 3. .

  In the second step, the above-mentioned organic solvent, alcohol such as octanol (octyl alcohol), nonpolar solvent, or the like may be added to the complexing reaction solution as necessary. As described above, the primary amine used for the complex formation reaction is preferably used as it is as the organic solvent.

  The manufacturing method of Ni nanoparticles 1 and 1A in the present embodiment can include an optional step in addition to the above steps.

[Composition for bonding electronic parts]
The bonding composition of the present invention contains the Ni nanoparticles 1 or 1A and a volatile solution, and the Ni nanoparticles 1 or 1A are dispersed in the volatile solution. Examples of the volatile solution include organic solvents such as toluene, xylene, hexane, cyclohexane, octane, dencan, limonene, methanol, ethanol, propanol, isopropanol, and butanol. The composition for joining electronic components can be in the form of, for example, a slurry, a paste, a grease, or a wax.

  The bonding composition of the present invention preferably contains Ni nanoparticles 1 or 1A in the range of 20 to 90% by weight with respect to the total weight of the composition. When the content of the Ni nanoparticles 1 or 1A is less than 20% by weight, for example, it is necessary to repeat coating several times, which may cause unevenness and may not provide sufficient bonding strength, exceeding 90% by weight. And fluidity | liquidity falls and the usability as a joining material may fall.

[Electronic components and production]
The electronic component of the present invention is obtained by forming a joining portion (metal joining layer) using the Ni nanoparticles 1, 1A or the joining composition. Here, examples of the electronic component mainly include a semiconductor device and an energy conversion module component. When the electronic component is a semiconductor device, the Ni nanoparticles 1, 1A or the bonding composition may be, for example, between the back surface of the semiconductor element and the substrate, between the semiconductor electrode and the substrate electrode, and between the semiconductor electrode and the semiconductor electrode. It can be applied to bonding between a power device or a power module and a heat radiating member.

  The joining with the Ni nanoparticles 1, 1A or the joining composition is, for example, a step of applying the Ni nanoparticles 1, 1A or the joining composition to one or both of the surfaces to be joined (a coating step). And bonding the surfaces to be joined together, for example, by heating to a temperature of 200 ° C. or higher and 450 ° C. or lower, preferably 250 ° C. or higher and 400 ° C. or lower, to sinter the bonding material (heating step), and sintered bonding A step of solidifying by cooling the material to form a metal bonding layer (solidification step). FIG. 3 is a drawing for explaining an example in which the joining of electronic components using Ni nanoparticles 1, 1A or a joining composition is applied to a die bonding process of a semiconductor integrated circuit (IC). In this example, an IC chip 20 as a semiconductor element is bonded to an island portion (die pad) 10A provided on the lead frame 10. In this case, the Ni nanoparticles 1, 1A or the bonding composition can be applied to the upper surface of the island portion 10A by an arbitrary method, and the IC chip 20 can be overlapped thereon and heated to be bonded.

  In the coating step of applying the Ni nanoparticles 1, 1A or the bonding composition, methods such as spray coating, ink jet coating, and printing can be employed. The Ni nanoparticles 1 and 1A or the bonding composition can be applied in an arbitrary shape such as a pattern, an island, a mesh, a lattice, or a stripe depending on the purpose. In the application step, it is preferable to apply the Ni nanoparticles 1, 1A or the bonding composition so that the thickness of the solidified bonding portion (metal bonding layer) after bonding is 120 nm or more. By applying with such a thickness, defects in the joint portion can be reduced, so that an increase in electrical resistance and a decrease in joint strength can be prevented. In FIG. 3, Ni nanoparticles 1, 1A or a bonding composition may be applied to the lower surface of the IC chip 20.

  In the heating step, Ni and Ni alloy constituting the Ni nanoparticles 1 and 1A are sintered, and a metal bonding layer having a uniform and strong adhesive force can be formed. Further, in the Ni nanoparticles 1, 1A provided with the reducing organic substance film 7, since the Ni oxide and the Ni hydroxide constituting the oxygen-containing film 5 are reduced by the action of the reducing organic substance, Oxygen is prevented from entering, and the conductivity of the metal bonding layer is ensured. The heating temperature for bonding is preferably 200 ° C. or higher, and more preferably 250 ° C. or higher in order to obtain sufficient bonding strength. Further, when the heating temperature exceeds 450 ° C., there is a concern about damage to peripheral circuits or electrodes. Therefore, the upper limit of the heating temperature is preferably 450 ° C. or less, and more preferably 400 ° C. or less.

  The atmosphere during bonding preferably contains 1% by volume or more of oxygen. Further, by reducing the pressure, an effect of suppressing the generation of voids can be obtained. For example, the effect is confirmed at a pressure of 95% or less of the atmospheric pressure. Moreover, when bonding a joint surface, it can be pressurized as needed.

  When bonding electronic components, in order to increase the bonding strength, for example, a contact metal layer made of a material such as Au, Cu, Pd, Ni, Ag, Cr, Ti or an alloy thereof is previously formed on one or both of the surfaces to be bonded. Is preferably provided. When the material of the surface to be joined is SiC or Si or an oxide film on the surface thereof, a contact metal layer made of a material such as Ti, TiW, TiN, Cr, Ni, Pd, V or an alloy thereof is used. It is preferable to provide it. The thickness of each contact metal layer is preferably in the range of, for example, 50 nm or more and 2 μm or less. If the thickness of the contact metal layer is less than 50 nm, defects are likely to occur, and if it exceeds 2 μm, the vapor deposition process becomes long, and the production efficiency may be reduced.

  The thickness of the joining portion (metal joining layer) made of Ni or Ni alloy formed by the Ni nanoparticles 1 and 1A is preferably 120 nm or more, for example. When the thickness of the joint portion is thinner than this, defects in the joint portion increase, which causes an increase in electrical resistance and a decrease in strength.

  In addition, the joining portion (metal joining layer) made of Ni or Ni alloy formed of Ni nanoparticles 1 and 1A may have a void when applied to an application that requires thermal stress relaxation.

  The above bonding material, bonding structure and bonding conditions are not limited to bonding of Si and SiC, but can be used for bonding of other structural materials such as metal materials. In particular, when the base material is deteriorated in the heat-affected zone in joining by wax material or welding, it is preferable to join at a low temperature using the Ni nanoparticles 1 or 1A of the present invention. For example, hardened steel, stainless steel, metal materials reinforced by work hardening, inorganic materials and metals that deteriorate due to thermal oxidation and thermal strain, whose strength is reduced by recovery or recrystallization when heated at 450 ° C or higher or 800 ° C or higher. Suitable for joining materials. Examples of the joined body include, but are not limited to, a pipe, a plate, a joint, a rod, a wire, and a bolt.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. In the examples of the present invention, various measurements and evaluations are as follows unless otherwise specified.

[Average particle diameter of metal nanoparticles]
The average particle size of the metal particles is obtained by taking a photograph of the sample with an SEM (scanning electron microscope), randomly extracting 200 samples from the sample, and obtaining the average particle size (area average size) and standard deviation. It was. The CV value (coefficient of variation) was calculated by (standard deviation) / (average particle size).

[Crystal diameter of metal particles]
It calculated from the X-ray powder diffraction (XRD) result according to Scherrer's equation.

[5% heat shrink temperature]
The 5% heat shrink temperature is obtained by placing a sample in a 5Φ × 2 mm cylindrical molding machine and producing a molded product obtained by press molding, and then heating it in an atmosphere of nitrogen gas (containing 3% hydrogen gas). The temperature was 5% thermal yield measured by an analyzer (TMA).

Synthesis example 1
By adding 18.5 g of nickel formate dihydrate to 144.9 g of myristylamine and heating at 120 ° C. for 10 minutes under a nitrogen flow, the nickel formate was dissolved to obtain a complexing reaction solution. Next, 96.6 g of myristylamine was further added to the complexing reaction solution, and the mixture was heated at 180 ° C. for 10 minutes using a microwave to obtain a Ni nanoparticle slurry 1a.

  The Ni nanoparticle slurry 1a was allowed to stand and separated, the supernatant was removed, washed with hexane and methanol, and then dried for 6 hours in a vacuum dryer maintained at 60 ° C. to obtain Ni nanoparticles 1b (nickel-containing) Rate: 98 wt%, average particle size: 71 nm, crystallite size: 19 nm, CV value: 0.16, 5% heat shrinkage temperature: 290 ° C.). As a result of elemental analysis, it was C; 0.7, N; 0.016, O; 2.8 (unit: mass%). The elemental carbon and elemental nitrogen in this elemental analysis are derived from myristylamine and mean a coating of an amine compound. The thickness of the oxygen-containing film was 3 nm.

Synthesis example 2
In the same manner as in Synthesis Example 1 except that 209.8 g of laurylamine was used instead of 241.5 g of myristylamine in Synthesis Example 1, Ni nanoparticle slurry 2a and Ni nanoparticle 2b (nickel content: 98 wt. %, Average particle size: 100 nm, crystallite size: 23 nm, CV value: 0.17, 5% heat shrinkage temperature: 295 ° C.). As a result of elemental analysis, it was C; 0.5, N; 0.026, O; 2.2 (unit: mass%). The carbon element and the nitrogen element in this elemental analysis are derived from laurylamine, and mean a coating of an amine compound. The thickness of the oxygen-containing film was 4 nm.

Synthesis example 3
Ni nanoparticle slurry 3a and Ni nanoparticle 3b (nickel content; similar to synthesis example 1) except that 400.2 g of trioctylamine was used instead of 241.5 g of myristylamine in synthesis example 1. 98 wt%, average particle size: 20 nm, crystallite size: 13 nm, CV value: 0.17, 5% heat shrinkage temperature: 265 ° C.). As a result of elemental analysis, it was C; 2.8, N; 0.125, O; 5.3 (unit: mass%). The carbon element and the nitrogen element in this elemental analysis are derived from trioctylamine and mean a coating of an amine compound. The thickness of the oxygen-containing film was 3 nm.

Synthesis example 4
Ni nanoparticle slurry 4a and Ni nanoparticle 4b (nickel content: 98 wt%) were prepared in the same manner as in Synthesis Example 1 except that 302.7 g of oleylamine was used instead of 241.5 g of myristylamine in Synthesis Example 1. Average particle size: 43 nm, crystallite size: 15 nm, CV value: 0.17, 5% heat shrinkage temperature: 275 ° C.). As a result of elemental analysis, it was C; 1.9, N; 0.076, O; 3.3 (unit: mass%). The elemental carbon and elemental nitrogen in this elemental analysis are derived from oleylamine and mean a coating of an amine compound. The thickness of the oxygen-containing film was 2 nm.

[Test example]
First, the experimental results on which the present invention is based will be described. Here, regarding the use of Ni nanoparticles that can be manufactured at a relatively low cost, the influence of the particle size and bonding temperature on bonding strength was examined.

  A dummy chip was prepared for the bonding evaluation using Ni nanoparticles. The structure of this dummy chip is as shown in FIG. 4, and Cr / Ni / Au is vapor-deposited at a thickness of 500/3000/500 angstroms on the Si oxide film (thickness of 1000 angstroms) on the Si substrate surface. Vapor deposition was performed by evaporating metal chips on a boat with a vacuum vapor deposition apparatus. The Au layer is provided for the purpose of preventing the oxidation of the surface. Each element was continuously deposited in a vacuum chamber. The size of the dummy chip was 2.7 × 2.7 mm.

  In order to evaluate as a die bonding material, first, the above-mentioned chip pair is prepared, and as shown in FIG. 5, the Au surfaces are arranged facing each other, and Ni nanoparticles as a die bonding material are applied between them. Then, it was heated to a maximum of 300 ° C. and pressurized to a maximum of 50 kg for bonding. In FIG. 5, a metal bonding layer made of Ni nanoparticles is denoted by reference numeral 100. Ni nanoparticles have an average particle diameter of 20 nm (Ni nanoparticles 3b of Synthesis Example 3), 100 nm (Ni nanoparticles 2b of Synthesis Example 2), 200 nm (Ni nanoparticles c; commercial product, nickel content: 99 wt%, 200 nm, crystallite diameter; 40 nm, CV value; 0.32, 5% heat shrink temperature; 400 ° C.) and 400 nm (Ni nanoparticle d; commercial product, nickel content; 99 wt%, average particle diameter; 400 nm, crystallite diameter; 45 nm, CV value; 0.36, 5% heat shrink temperature; 470 ° C.). In any case, the particle size includes 95% or more of the size of ± 50% of the average particle size. Further, particles having an average particle diameter of 200 nm and 400 nm do not contain 3% or more of particles having a particle diameter of 100 nm or less.

  In the joint strength test, a shear tester (PTR-04) made by Leska and a load cell MAX5 kgf were used, and a die shear test was performed. The result of the die shear test is shown in FIG. The shear strength on the vertical axis of the graph in FIG. 6 is a standardized number. From FIG. 6, Ni nanoparticles having an average particle diameter of 20 nm and 100 nm showed higher shear strength even at low temperature bonding than those having an average particle diameter of 200 nm and 400 nm. That is, Ni nanoparticles having an average particle size of 20 nm and 100 nm have an increase in shear strength from a bonding temperature of about 200 ° C., and the shear strength at a bonding temperature of 300 ° C. is higher than that of those having an average particle size of 200 nm and 400 nm. , Confirmed to be significantly higher values.

  The observation of the bonding state was carried out by a transmission image using a microfocus X-ray apparatus (Shimadzu SMX-1000) and a structure observation by cross-sectional polishing. The fracture surface of the joint section was also observed. SEM images of the used Ni nanoparticles are shown in FIGS. 7 and 8, and an example of a fracture surface of the joining portion (metal joining layer) is shown in FIG. As a result of observing these joining conditions, it was confirmed that the nano-sized particles were grown after joining and bulk metalized before joining.

[Examples 1 to 5, Comparative Examples 1 and 2]
Ti, Ni, and Ag films were sequentially deposited on the back surface of the SiC chip. The upper surface of the SiC chip was prepared with an Al film formed to a thickness of 2 μm. A substrate prepared by plating Ag on Cu was prepared. Samples containing the following Ni nanoparticles of A to D were prepared as bonding materials.

A: Containing 40% or more of Ni nanoparticles having a particle size of 10 nm or more and 50 nm or less B: Containing 40% or more of Ni nanoparticles having a particle size of 50 nm or more and 100 nm or less C: Particle size of 10 nm or more Containing 5% of Ni nanoparticles of 100 nm or less in all particles D: Containing 96% of Ni nanoparticles having a particle diameter of 200 nm or more in all particles

Sample A is
60 parts by mass of Ni nanoparticles 1b (average particle size: 71 nm) obtained in Synthesis Example 1,
40 parts by mass of Ni nanoparticles 3b (average particle size; 20 nm) obtained in Synthesis Example 3,
Were prepared by mixing.

Sample B is
40 parts by mass of Ni nanoparticles 1b (average particle diameter: 71 nm) obtained in Synthesis Example 1,
60 parts by mass of Ni nanoparticles 3b (average particle size; 20 nm) obtained in Synthesis Example 3,
Were prepared by mixing.

Sample C is
95 parts by mass of Ni nanoparticles c (commercially available product, nickel content: 99 wt%, average particle size; 200 nm, crystallite size; 40 nm, CV value; 0.32, 5% heat shrink temperature; 400 ° C.)
5 parts by mass of Ni nanoparticles 3b (average particle diameter; 20 nm) obtained in Synthesis Example 3,
Were prepared by mixing.

Sample D is
96 parts by mass of Ni nanoparticles d (commercially available product, nickel content: 99 wt%, average particle size; 400 nm, crystallite size; 45 nm, CV value; 0.36, 5% heat shrink temperature; 470 ° C.)
4 parts by mass of Ni nanoparticles 3b (average particle size; 20 nm) obtained in Synthesis Example 3,
Were prepared by mixing.

  A solution in which the bonding material of each sample was dispersed in a solution was spray-coated on the substrate surface so that the thickness of the bonded portion (metal bonding layer) after bonding was 120 nm or more, and was dried. Each sample was joined at the heating temperature shown in Table 1. The joining time was 10 minutes in all cases. The atmosphere was air.

  Evaluation is made by comparing the shear strengths based on those bonded with commercially available die bonding solders, and those having a strength of 40% or more with respect to the strength of the solder bonding are ○ (good), and less than 40% × ( Bad). The results are shown in Table 1. Note that the thickness of the bonded portion (metal bonding layer) after bonding was about 40 μm.

  From Table 1, a bonding material containing Ni nanoparticles having a particle diameter of 100 nm or less in a total particle of 5% or more, preferably 40% or more has a practically sufficient bonding strength by bonding at a heating temperature of 250 ° C. or more. It was confirmed to have.

  As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment.

  DESCRIPTION OF SYMBOLS 1,1A ... Ni nanoparticle, 3 ... Metal particle, 5 ... Oxygen-containing film, 7 ... Reducing organic substance film, 10 ... Lead frame, 10A ... Island part (die pad), 20 ... IC chip

Claims (16)

A joining material for electronic parts used for joining electronic parts,
Metal fine particles composed of a metal selected from the group consisting of Ni and Ni alloys, and an oxygen-containing film which is an oxide film or a hydroxide film having a thickness in the range of 1 nm to 8 nm, which covers the metal fine particles. And a metal nanoparticle having an average particle diameter of 100 nm or less.   2. The electronic component bonding material according to claim 1, wherein the metal nanoparticles further include a film of a reducing organic substance having a molecular weight of 1 or more that further covers the outer side of the oxygen-containing film.   The electronic component bonding material according to claim 2, wherein the reducing organic substance is an amine compound.   The electronic component joining according to claim 2 or 3, wherein carbon is contained in a range of 0.1 wt% to 5.0 wt% and oxygen is contained in a range of 0.5 wt% to 10.0 wt%. Wood.   5. The electronic component bonding material according to claim 1, wherein a coefficient of variation CV of a particle diameter of the metal fine particles is 0.2 or less.   6. The bonding material for electronic parts according to claim 1, wherein the metal nanoparticles include 5% or more of particles having a particle diameter in a range of 10 nm to 100 nm.   6. The bonding material for electronic parts according to claim 1, wherein the metal nanoparticles include 40% or more of particles having a particle diameter in the range of 50 nm to 100 nm.   6. The bonding material for electronic parts according to claim 1, wherein the metal nanoparticles include 40% or more of particles having a particle diameter in a range of 10 nm to 50 nm.   The bonding material for electronic parts according to any one of claims 1 to 8, wherein a crystallite diameter of the metal fine particles measured by X-ray diffraction is 30 nm or less. A method for manufacturing a bonding material for an electronic component according to any one of claims 1 to 9,
  The manufacturing method of the bonding | jointing material of an electronic component characterized by including the process of synthesize | combining the said metal nanoparticle by the wet microwave irradiation method. The bonding material for electronic parts according to any one of claims 1 to 9 ,
A volatile solution, and
A composition for joining electronic parts, wherein the joining material is dispersed in the volatile solution.   The composition for joining electronic components according to claim 11, wherein the composition is in the form of a slurry or a paste. The manufacturing method of an electronic component including the process of heating the bonding | jointing material of the electronic component of any one of Claim 1 to 9, and forming a junction part. The method of manufacturing an electronic component according to claim 13, wherein the bonding portion is formed between the back surface of the semiconductor element and the substrate, between the semiconductor electrode and the substrate electrode, or between the semiconductor electrode and the semiconductor electrode. The method for manufacturing an electronic component according to claim 13 or 14, wherein the heating temperature is 200 ° C or higher and 450 ° C or lower. Method of bonding an electronic component which performs bonding by heating to a temperature of 200 ° C. or higher 450 ° C. or less of a bonding material of an electronic component according to any one of claims 1 9.