JP2019057691A - Manufacturing method of semiconductor device - Google Patents

Abstract

To provide a manufacturing method of a semiconductor device, with an excellent connection reliability.SOLUTION: A manufacturing method of a semiconductor device, comprises: a mounting step of mounting a semiconductor element onto a support member for mounting the semiconductor element through a sinterability joint material including a metal particle and a disperse medium, and in which an outer peripheral edge of the sinterability joint material is larger than that of the semiconductor element in a plan view; a drying step of removing at least one part of the disperse medium from the sinterability joint material existed exceeding the outer peripheral edge of the semiconductor element; a joint step of heating the sinterability joint material, and jointing the support member for mounting the semiconductor element and the semiconductor element through a sinter material of the sinterability joint material; and a removing step of removing the sinter material of the sinterability joint material, which is existed exceeding the outer peripheral edge of the semiconductor element.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor device manufacturing method, and more particularly to a semiconductor device manufacturing method in which a semiconductor element and a semiconductor element mounting support member are bonded using a sinterable bonding material containing metal particles and a dispersion medium.

  In recent years, semiconductor package materials are required to have heat resistance (excellent stability and reliability under high temperature and high humidity). For example, in hybrid vehicles, electric vehicles, electric railways, and distributed power supplies, power semiconductors are often used in inverters, but the power density is remarkably improved, and the package material is exposed to high temperatures. In addition, electronics control units (ECUs) that use ordinary semiconductor chips used in the car electronics field have also been installed in the vehicle compartment until now, but they are in the direction of being installed in more severe engine rooms. High heat resistance is required. Further, wide band gap semiconductors (SiC and the like) have been applied, and applications for operating at a high temperature at 200 ° C. or higher are also expected.

  Under such a high temperature condition, it has been difficult to cope with solder that has been used as a bonding material for semiconductor elements. Therefore, joining with a sintered metal obtained by sintering a paste containing metal fine particles has been proposed as a joining technique for high temperatures (see, for example, Patent Document 1). However, when bonding is performed using a paste, the paste that protrudes from the outer peripheral portion of the semiconductor element at the time of bonding may crawl up to the end surface of the semiconductor element, and the semiconductor element may be short-circuited. Such creeping is particularly noticeable when the semiconductor element is heated while being pressurized in order to improve the adhesion to the support member.

  Therefore, a method has been proposed in which the paste application area is reduced in advance so that the paste does not protrude from the outer periphery of the semiconductor element during bonding (see, for example, Patent Document 2).

JP 2007-214340 A Japanese Patent Laying-Open No. 2015-153966

  By the way, the semiconductor element repeats heat generation and cooling due to energization during operation. At this time, since the semiconductor element and the members in the vicinity of the semiconductor element repeat the expansion and contraction operations according to the respective linear expansion coefficients, a certain load is applied to the peripheral edge of the semiconductor element. In this regard, in the method of Patent Document 2, the area of the sintered metal layer, which is a paste sintered product, is smaller than the area of the semiconductor element, and as shown in FIG. A sintered metal layer is not formed. When the sintered metal layer is not formed on the peripheral edge of the semiconductor element, there is a risk that interface peeling occurs at the bonding interface during semiconductor operation. This interfacial peeling causes a decrease in connection reliability of the semiconductor device.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for manufacturing a semiconductor device having excellent connection reliability.

  The present invention is a step of placing a semiconductor element on a semiconductor element mounting support member via a sinterable bonding material containing metal particles and a dispersion medium. Is larger than the outer peripheral edge of the semiconductor element, a placing process, a drying process for removing at least a part of the dispersion medium from the sinterable bonding material existing beyond the outer peripheral edge of the semiconductor element, and a sinterable bonding material A bonding step for bonding the semiconductor element mounting support member and the semiconductor element via a sintered product of a sinterable bonding material, and a sinterable bonding that exists beyond the outer periphery of the semiconductor element. And a removing step of removing a sintered product of the material.

  In the present invention, a drying step is essential before the sintering of the sinterable bonding material proceeds. Thereby, volatilization of the dispersion medium contained in the material progresses particularly in the sinterable bonding material existing beyond the outer peripheral edge of the semiconductor element. Even if the deposited layer of metal particles from which the dispersion medium has volatilized is sintered, sufficient flexibility and adhesion cannot be obtained. That is, the deposited layer cannot be fixed on the semiconductor element mounting support member due to the displacement caused by the difference in thermal expansion coefficient when the temperature is raised from room temperature to several hundred degrees which is the firing temperature. Become. The sintered metal piece can be suitably removed by the removing step. In the obtained semiconductor device, there is no sinter of the sinterable bonding material to the edge of the semiconductor element, and the semiconductor element and the support member for mounting the semiconductor element are baked with the same area as the bonding surface of the semiconductor element. It will be joined by the joint. Any of them solves the conventional problems, and it can be said that the present invention can provide a method for manufacturing a semiconductor device excellent in connection reliability.

  In this invention, it is preferable that a metal particle contains a copper particle and content of a copper particle is 80 mass% or more on the basis of the total mass of a sinterable joining material.

  In the present invention, the copper particles include sub-micro copper particles and flaky micro-copper particles, and the total content of the sub-micro copper particles and the flaky micro-copper particles is 80 masses based on the total mass of the metal particles. % Or more.

  In the present invention, the semiconductor element may be a wide band gap semiconductor.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the semiconductor device which is excellent in connection reliability can be provided.

It is a schematic cross section which shows an example of the semiconductor device obtained by the manufacturing method of the semiconductor device which concerns on this embodiment. It is a schematic cross section which shows the other example of the semiconductor device obtained by the manufacturing method of the semiconductor device which concerns on this embodiment. It is a cross-sectional SEM image about the sealing sample of an Example.

  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.

  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.

(Sintering bonding material)
An example of a sinterable bonding material used in the method for manufacturing a semiconductor device according to this embodiment is shown below.

  The sinterable bonding material according to the present embodiment includes metal particles and a dispersion medium, and can be referred to as a bonding metal paste. In particular, when the sinterable bonding material contains copper particles as metal particles, it can be referred to as a bonding copper paste.

(Metal particles)
Examples of the metal particles according to this embodiment include sub-micro copper particles, flaky micro-copper particles, copper particles other than these, and other metal particles.

(Sub-micro copper particles)
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. If 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, the 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 a raw material, or dry copper particles from which volatile components have been removed from a metal paste, dispersed in a dispersion medium using a dispersant are subjected to light scattering particle size distribution measurement. It can be determined by a method of measuring with an apparatus (for example, a Shimadzu nanoparticle size distribution measuring apparatus (SALD-7500 nano, manufactured by Shimadzu Corporation)). When using a light scattering particle size distribution analyzer, hexane, toluene, α-terpineol, or the like can be used as the dispersion medium.

  The sub-micro copper particles can contain 10% by mass or more of copper particles having a particle size of 0.12 μm or more and 0.8 μm or less. From the viewpoint of the sinterability of the metal paste, the sub-micro copper particles can contain 20% by mass or more, 30% by mass or more of copper particles having a particle size of 0.12 μm or more and 0.8 μm or less, It can be contained by mass%. When the content ratio of the copper particles having a particle size of 0.12 μm or more and 0.8 μm or less in the sub-micro copper particles is 20% by mass or more, the dispersibility of the copper particles is further improved, the viscosity is increased, and the paste concentration is decreased. It can be suppressed more.

  The particle size of the copper particles can be calculated from, for example, a scanning electron microscope (SEM) image. The copper particle powder is placed on a carbon tape for SEM with a spatula to obtain a sample for SEM. The sample for SEM is observed with a SEM apparatus at a magnification of 5000 times. A quadrilateral circumscribing the copper particles of this SEM image is drawn by image processing software, and one side thereof is set as the particle size of the particles.

  The content of the sub-micro copper particles may be 20% by mass or more and 90% by mass or less, 30% by mass or more and 90% by mass or less, or 35% by mass or more based on the total mass of the metal particles. 85 mass% or less may be sufficient, and 40 mass% or more and 80 mass% or less may be sufficient. When the content of the sub-micro copper particles is within the above range, it becomes easy to form a sintered product (sintered metal layer) excellent in bondability.

  The content of the sub-micro copper particles may be 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 flaky micro-copper particles. When the content of the sub-micro copper particles is 20% by mass or more, the space between the flaky micro-copper particles can be sufficiently filled, and it becomes easy to form a sintered product excellent in bondability. If the content of the sub-micro copper particles is 90% by mass or less, volume shrinkage when the metal paste is sintered can be sufficiently suppressed, so that it becomes easy to form a sintered product having excellent bondability. From the viewpoint of further exerting the above effect, the content of the sub-micro copper particles is 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 flaky micro-copper 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.

  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 viewpoints 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 microparticles, etc., Alternatively, it may be approximately spherical.

  The sub-micro copper particles may have an aspect ratio of 5 or less or 3 or less from the viewpoints of dispersibility, filling properties, and miscibility with the flaky micro 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 8 to 16 carbon atoms. Examples of the organic acid having 8 to 16 carbon atoms include caprylic acid, methylheptanoic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid, and ethyl. Octanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanoic acid, lauric acid, methylundecanoic 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, ethyldodecanoic acid, propylundecanoic acid, butyldecanoic acid, pentylnonanoic acid, Siloctanoic 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, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, Saturated fatty acids such as nonylcyclohexanecarboxylic acid; octenoic acid, nonenoic acid, methylnonenoic acid, decenoic acid Unsaturated fatty acids such as undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, sabienoic acid; terephthalic acid, pyromellitic acid, o-phenoxybenzoic acid, methylbenzoic acid, Examples include aromatic carboxylic acids such as ethyl benzoic acid, propyl benzoic acid, butyl benzoic acid, pentyl 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 (n) attached to the surface of the sub-micro copper particles, the specific surface area (A _p ) (unit m ² / g) of the sub-micro copper particles, and the molecular weight (M _s ) of the surface treatment agent (M _s ) It can be calculated from the unit g / mol), the minimum covering area (S _S ) (unit m ² / piece) of the surface treatment agent, 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 )} * Calculated according to the equation of 100%.

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 metal 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.

  As the sub-micro copper particles, 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 Nippon Sanso Corporation, volume average particle size 0.12 μm).

(Flake micro copper particles)
Examples of the flaky micro copper particles include those containing copper particles having a maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of 4 or more. For example, the average maximum diameter is 1 μm or more and 20 μm or less, and the aspect ratio is 4 The above copper particles can be used. If the average maximum diameter and aspect ratio of the flaky micro-copper particles are within the above ranges, the volume shrinkage when the metal paste is sintered can be sufficiently reduced, and it is easy to form a sintered product excellent in bondability. Become. From the standpoint of further achieving the above effects, the average maximum diameter of the flaky micro copper particles may be 1 μm or more and 10 μm or less, or 3 μm or more and 10 μm or less. The measurement of the maximum diameter and the average maximum diameter of the flaky micro-copper particles can be obtained from, for example, an SEM image of the particles, and is obtained as a major axis X and an average value Xav of the major axis described later.

  The flaky micro copper particles can contain 50% by mass or more of copper particles having a maximum diameter of 1 μm or more and 20 μm or less. From the viewpoint of orientation in the sintered product, reinforcing effect, and filling property of the bonding paste, the flaky micro copper particles can contain 70% by mass or more of copper particles having a maximum diameter of 1 μm or more and 20 μm or less, and 80% by mass. It can contain above, and it can contain 100 mass%. From the viewpoint of suppressing poor bonding, the flaky micro-copper particles preferably do not contain particles having a size exceeding the bonding thickness, such as particles having a maximum diameter exceeding 20 μm.

  A method of calculating the major axis X of the flaky micro copper particles from the SEM image is illustrated. The powder of flaky micro copper particles is placed on a carbon tape for SEM with a spatula to obtain a sample for SEM. The sample for SEM is observed with a SEM apparatus at a magnification of 5000 times. A rectangle circumscribing the flaky micro copper particles of the SEM image is drawn by image processing software, and the long side of the rectangle is defined as the major axis X of the particles. This measurement is performed on 50 or more flaky micro copper particles using a plurality of SEM images, and the average value Xav of the major axis is calculated.

  The aspect ratio of the flaky micro copper particles may be 4 or more, or 6 or more. If the aspect ratio is within the above range, the flaky micro copper particles in the metal paste are oriented substantially parallel to the bonding surface, so that volume shrinkage when the metal paste is sintered can be suppressed. It becomes easy to form a sintered product having excellent properties.

  The content of the flaky micro copper particles may be 1% by mass or more and 90% by mass or less, 10% by mass or more and 70% by mass or less, and 20% by mass based on the total mass of the metal particles. It may be 50% by mass or more. When the content of the flaky micro copper particles is within the above range, it becomes easy to form a sintered product having excellent bondability.

  The total content of the sub-micro copper particles and the content of the flaky micro-copper particles may be 80% by mass or more based on the total mass of the metal particles. When the sum of the content of the sub-micro copper particles and the content of the flaky micro-copper particles is within the above range, it becomes easy to form a sintered product having excellent bondability. From the viewpoint of further exerting the above effects, the total content of the sub-micro copper particles and the content of the flaky micro-copper particles may be 90% by mass or more based on the total mass of the metal particles. The mass may be 100% by mass or more.

  In the flaky 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 flaky 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 a surface treatment agent include aliphatic carboxylic acids such as palmitic acid, stearic acid, arachidic acid, and oleic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, and o-phenoxybenzoic acid; cetyl alcohol Aliphatic alcohols such as stearyl alcohol, isobornylcyclohexanol and tetraethylene glycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine and stearylamine; fats such as stearonitrile and deconitrile Group nitriles; Silane coupling agents such as alkyl alkoxysilanes; Polymer treatment materials such as polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, and silicone oligomers. 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 flaky 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 flaky 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 preparing a metal paste only from the above-mentioned sub-micro copper particles, volume shrinkage and sintering shrinkage accompanying the volatilization of the dispersion medium are large, so that the metal paste is easily peeled off from the adherend surface during the sintering of the metal paste, so In this case, it is difficult to obtain sufficient die shear strength and connection reliability. By using the sub-micro copper particles and the flaky micro-copper particles in combination, volume shrinkage when the metal paste is sintered is suppressed, and it becomes easy to form a sintered product having excellent bondability.

  As the flaky micro copper particles according to this embodiment, commercially available ones can be used. Examples of commercially available flaky micro copper particles include MA-C025 (Mitsui Metal Mining Co., Ltd., average maximum diameter 4.1 μm), 3L3 (Fukuda Metal Foil Powder Co., Ltd., average maximum diameter 7.3 μm). ) 1110F (Mitsui Metal Mining Co., Ltd., average maximum diameter 5.8 μm), 2L3 (Fukuda Metal Foil Powder Co., Ltd., average maximum diameter 9 μm).

  The content of the copper particles is preferably 80% by mass or more, more preferably 90% by mass or more based on the total mass of the sinterable bonding material. Thereby, it becomes easy to form a sintered product having excellent bondability.

(Other metal particles other than copper particles)
As a metal particle, other metal particles other than the sub micro copper particle and micro copper particle which were mentioned above may be included, for example, particles, such as nickel, silver, gold | metal | money, palladium, platinum, may be included. The other metal particles may have a volume average particle size of 0.01 μm or more and 10 μm or less, 0.01 μm or more and 5 μm or less, or 0.05 μm or more and 3 μm or less. When other metal particles are contained, the content thereof may be less than 20% by mass or less than 10% by mass based on the total mass of the metal particles from the viewpoint of obtaining sufficient bondability. May be. Other metal particles may not be included. The shape of other metal particles is not particularly limited.

  By including metal particles other than copper particles, it is possible to obtain a sintered product in which a plurality of types of metals are dissolved or dispersed, and thus mechanical properties such as yield stress and fatigue strength of the sintered product are improved, Connection reliability is easy to improve. Further, by adding a plurality of types of metal particles, the formed sintered product is likely to improve the bonding strength and connection reliability with respect to a specific adherend.

(Dispersion medium)
The dispersion medium is preferably volatile. Examples of the volatile dispersion medium include monovalent and polyvalent pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, α-terpineol, isobornylcyclohexanol (MTPH), and the like. Dihydric 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 Butyl 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 Esters such as coal butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, propylene carbonate; N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N- Acid amides such as dimethylformamide; Aliphatic hydrocarbons such as cyclohexanone, octane, nonane, decane and undecane; Aromatic hydrocarbons such as benzene, toluene and xylene; Mercaptans having an alkyl group having 1 to 18 carbon atoms; Examples include mercaptans having 5 to 7 cycloalkyl groups. 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 with 100 parts by mass of the total mass of the metal particles. If the content of the dispersion medium is within the above range, the metal paste can be adjusted to a more appropriate viscosity, and it is difficult to inhibit the sintering of the copper particles.

(Additive)
Where necessary, wetting additives such as nonionic surfactants and fluorosurfactants; antifoaming agents such as silicone oils; ion trapping agents such as inorganic ion exchangers and the like are appropriately added to the metal paste. Also good.

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

  For metal paste, sub-micro copper particles, surface treatment agent and dispersion medium are mixed in advance, and dispersion treatment is performed to prepare a dispersion of sub-micro copper particles. Further, micro-copper particles, other metal particles, and optional additions You may mix and prepare an agent. By setting it as such a procedure, the dispersibility of a sub micro copper particle improves, a miscibility with a micro copper particle improves, and the performance of a metal paste improves more. Classification may be performed on the sub-micro copper particle dispersion to remove aggregates.

<Method for Manufacturing Semiconductor Device>
The manufacturing method of a semiconductor device according to the present embodiment includes a mounting step of mounting a semiconductor element on a semiconductor element mounting support member via a sinterable bonding material containing metal particles and a dispersion medium, and a semiconductor element A drying step for removing at least a part of the dispersion medium from the sinterable bonding material existing beyond the outer peripheral edge of the substrate, heating the sinterable bonding material, and the semiconductor element mounting support member and the semiconductor element, A joining step of joining through a sintered product of the sinterable bonding material; and a removing step of removing the sintered product of the sinterable joining material that exists beyond the outer peripheral edge of the semiconductor element.

(Installation process)
The method for providing the sinterable bonding material on the semiconductor element mounting support member is not particularly limited as long as it is a method capable of depositing the sinterable bonding material. Examples of such methods include 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. 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 sinterable bonding material may be 1 μm or more and 1000 μm or less, 10 μm or more and 500 μm or less, 50 μm or more and 200 μm or less, 10 μm or more and 3000 μm or less, or 15 μm. It may be 500 μm or less, 20 μm or more and 300 μm or less, 5 μm or more and 500 μm or less, 10 μm or more and 250 μm or less, or 15 μm or more and 150 μm or less.

  The sinterable bonding material is provided so that the outer peripheral edge of the sinterable bonding material is larger than the outer peripheral edge of the semiconductor element in plan view. As a result, a part of the sinterable bonding material is in a state of “extinguishing” from the bonding surface of the semiconductor element. The sinterable bonding material has a peripheral edge of the semiconductor element in plan view so that the bonding interface between the semiconductor element mounting support member and the semiconductor element is sufficiently bonded by the sintered product of the sinterable bonding material throughout. To at least 1 mm, more preferably at least 5 mm. In view of the size of a general semiconductor element and a semiconductor element mounting support member, the upper limit of the protrusion width can be about 20 mm.

  Examples of the method for placing the semiconductor element on the sinterable bonding material include a chip mounter, a flip chip bonder, a carbon or ceramic positioning jig.

  By this step, a semiconductor element, a precursor laminated body in which a sinterable bonding material having an area exceeding the bonding area of the semiconductor element and a semiconductor element mounting support member are laminated in this order on the direction in which the self-weight of the semiconductor element works. Can be obtained.

(Drying process)
In this step, the precursor laminate obtained by the placing step is subjected to a drying process. Thereby, in particular, at least a part of the dispersion medium is removed from the sinterable bonding material existing beyond the outer peripheral edge of the semiconductor element.

  The gas atmosphere in the drying step may be in the air, in an oxygen-free atmosphere such as nitrogen or a rare gas, or in a reducing atmosphere such as hydrogen or formic acid. The drying treatment may be room temperature drying, warm drying, reduced pressure drying, or drying at room temperature or a combination of warm drying and reduced pressure drying. For heating drying and 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, An electromagnetic heating device, a heater heating device, a steam heating furnace, a hot plate press device, or the like can be used.

  For example, when performing warming drying as the drying process, the heating temperature and time may be appropriately adjusted according to the type and amount of the used dispersion medium. The heating temperature and time can be 50 ° C. or higher and 230 ° C. or lower and 1 minute or longer and 120 minutes or shorter, respectively.

(Joining process)
In this step, the sinterable bonding material is sintered by subjecting the precursor laminate that has undergone the drying step to heat treatment. 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 in the bonding step may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the sintered body, the semiconductor element, and the semiconductor element mounting support member. The gas atmosphere in the joining process may be a reducing atmosphere from the viewpoint of removing oxides on the surface of the metal particles contained in the sinterable joining material. Examples of the oxygen-free atmosphere include an oxygen-free gas atmosphere such as nitrogen or a rare gas, or a vacuum atmosphere. Examples of the reducing atmosphere include pure hydrogen gas atmosphere, mixed gas atmosphere of hydrogen and nitrogen typified by forming gas, nitrogen atmosphere containing formic acid gas, mixed gas atmosphere of hydrogen and rare gas, rare gas atmosphere containing formic acid gas, etc. Is mentioned.

  The maximum temperature reached during the heat treatment may be 250 ° C. or higher and 450 ° C. or lower, and may be 250 ° C. or higher and 400 ° C. or lower, from the viewpoint of reducing thermal damage to the semiconductor element and the semiconductor element mounting support member and improving the yield. Or 250 ° C. or more and 350 ° C. or less. If the ultimate temperature is 250 ° C. or higher, the sintering tends to proceed sufficiently when the ultimate temperature holding time is 60 minutes or less.

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

  The pressure at the time of joining is not particularly limited, but it is preferable that the copper content (deposition ratio) in the sintered product is 65% by volume or more based on the total volume of the sintered product. For example, by using a predetermined sinterable bonding material containing sub-micro copper particles, flaky micro-copper particles, etc., as described above, a sintered product excellent in bondability without applying pressure during bonding. Can be formed. In this case, sufficient bonding strength is obtained only by the self-weight of the semiconductor element existing on the sinterable bonding material, or by further applying a pressure of 0.01 MPa or less, preferably 0.005 MPa or less to the self-weight of the semiconductor element. be able to. In this case, since a special pressurizing device is not required, void reduction, bonding strength, and connection reliability can be further improved without impairing yield. Examples of a method in which the sinterable bonding material receives a pressure of 0.01 MPa or less include a method of placing a weight on a semiconductor element.

  From the viewpoint of improving the yield and improving the density of the sintered product, pressurization may be applied to the bonding paste via the semiconductor element. The pressurizing pressure can be 0.01 MPa or more and 10 MPa or less. If it is a low pressure of about 0.01 MPa or more and 0.1 MPa or less, it is possible to suppress the bonding defects such as peeling and improve the yield. On the other hand, if the density is 1 MPa or more and 10 MPa or less, further improvement in bonding strength and improvement in thermal conductivity can be expected due to improvement in the density of the sintered product. Examples of the pressing method include a pressing jig using a weight, a spring jig, silicone rubber, etc., a thermocompression bonding apparatus, and a hot plate pressing apparatus.

(Removal process)
In this step, among the sintered products formed by the joining step, a sintered product (sintered metal piece) existing beyond the outer peripheral edge of the semiconductor element is removed in plan view. That is, the sintered material that does not contribute to the bonding formed from the portion of the sinterable bonding material that protrudes from the bonding surface of the semiconductor element is removed. Thereby, the malfunctioning by the fall of such a sintered compact is prevented. This process can be implemented using an air gun, an adhesive sheet, an adhesive tape etc., for example.

<Semiconductor device>
The semiconductor device shown in FIG. 1 can be obtained by the method for manufacturing a semiconductor device according to this embodiment. In FIG. 1, a semiconductor device 100 includes a semiconductor element 2, a semiconductor element mounting support member 3, a sintered body (sintered) of a sinterable bonding material that joins the semiconductor element 2 and the semiconductor element mounting support member 3. Metal layer) 1 is provided. In the semiconductor device 100 obtained by the semiconductor device manufacturing method according to the present embodiment, the semiconductor element 2 and the semiconductor element mounting support member 3 are joined by the sintered product 1 having substantially the same area as the joining surface 2 a of the semiconductor element 2. Has been.

  For the semiconductor element 2, in addition to a general semiconductor material such as silicon (Si), a wide band gap semiconductor material such as silicon carbide (SiC) or gallium nitride (GaN) can be used without particular limitation. . Specific examples of the semiconductor element 2 include semiconductor elements such as IGBTs, diodes, Schottky barrier diodes, MOS-FETs, thyristors, logics, sensors, analog integrated circuits, LEDs, semiconductor lasers, and oscillators. The semiconductor element mounting support member 3 includes a lead frame, a ceramic substrate with a metal plate (for example, DBC), a substrate for mounting a semiconductor element such as an LED package, a metal wiring such as a copper ribbon and a metal frame, a metal block, etc. Examples include a power supply member such as a block body and a terminal, a heat radiating plate, and a water cooling plate.

  FIG. 2 is a schematic cross-sectional view showing another example of the semiconductor device. A semiconductor device 110 shown in FIG. 2 has a semiconductor element 2 and a semiconductor element mounting support member 3 joined together by a sintered product (sintered metal layer) 1 of a sinterable joining material, and then a terminal above the semiconductor element 2. (Not shown) is connected to the lead frame 5 with wires 4, and finally the whole is covered with an insulating sealing material 6.

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

<Example 1>
(Preparation of metal paste)
Α-Terpineol (manufactured by Wako Pure Chemical Industries, Ltd.) 5.2 g and isobornylcyclohexanol (MTPH, manufactured by Nippon Terpene Chemical Co., Ltd.) 6.8 g as dispersion media, and CH-0200 (Mitsui Metals) as sub-micro copper particles 52.8 g of 0.12 μm or more and 0.8 μm or less of copper particles manufactured by Mining Co., Ltd.) was mixed in a plastic bottle and 19 by an ultrasonic homogenizer (US-600, manufactured by Nippon Seiki Co., Ltd.). A dispersion was obtained by treatment at 6 kHz, 600 W for 1 minute. In this dispersion, 35.2 g of MA-C025 (manufactured by Mitsui Mining & Smelting Co., Ltd., average maximum diameter 4.1 μm, content of copper particles having an aspect ratio of 6.6, 100 mass%) as flaky micro copper particles Was added and stirred with a spatula until there was no dry powder. Seal the plastic bottle and stir at 2000 rpm for 2 minutes using a rotating and rotating stirrer (Planetary Vacuum Mixer ARV-310, manufactured by Sinky Co., Ltd.). Copper paste).

(Installation process)
A copper substrate having a size of 19 mm × 25 mm × 3 mm (thickness), a Si chip having a size of 5 mm × 5 mm × 150 μm (thickness), and a titanium layer / nickel layer provided in this order by sputtering on the entire bonding surface; Prepared. A metal paste was stencil-printed on a copper substrate using a 100 μm-thick stainless steel mask having a 10 mm × 10 mm square opening and a squeegee. An Si chip was placed on the printed metal paste so that the nickel layer was in contact with the metal paste. The Si chip was lightly pressed with tweezers to adhere the Si chip and the metal paste. This obtained the precursor laminated body.

(Drying process)
The precursor laminate obtained in the placing step was heated at 160 ° C. for 5 minutes in the air using a warm air dryer (manufactured by ESPEC). Thereafter, the hot air dryer was stopped, and the precursor laminate was taken out after the temperature of the hot air dryer reached 100 ° C. or lower. Thereby, at least a part of the dispersion medium was removed from the metal paste that protruded from the joint surface of the Si chip.

(Joining process)
The precursor laminated body which passed through the drying process was set in a tube furnace (manufactured by Ave Sea Co., Ltd.), and argon gas was flowed at 1 L / min to replace the air with argon gas. Thereafter, the metal paste was sintered by heating at 350 mL for 10 minutes and flowing at 350 ° C. for 10 minutes while flowing hydrogen gas at 300 mL / min. Thereby, the laminated body with which the copper substrate and Si chip | tip were joined via the sintered metal layer which is a sintered compact of a metal paste was obtained. Then, it cooled, flowing argon gas at 0.3 L / min, and took out the laminated body in the air at 50 degrees C or less.

(Removal process)
Of the sintered product formed by the joining process, the sintered product (sintered metal piece) existing beyond the outer periphery of the Si chip was removed. The removal was performed by performing nitrogen blowing for 10 to 120 seconds using an air gun (manufactured by ASONE).

<Examples 2 to 8 and Comparative Example 1>
Except that the atmosphere, heating temperature, and heating time in the drying process were changed as shown in Table 1, the mounting process to the removing process were performed in the same manner as in Example 1.

<Comparative example 2>
Placed in the same manner as in Comparative Example 1 except that a 100 μm thick stainless steel mask having a 3 mm × 3 mm square opening was used instead of the 100 μm thick stainless steel mask having a 10 mm × 10 mm square opening. Process to joining process were performed.

<Various evaluations>
(Removability evaluation of sintered metal pieces)
After the removal process, the digital microscope (manufactured by Keyence Corporation) is used to determine what percentage of the area (excluding the chip area) where the metal paste has been applied. Observed and evaluated. And the removability of the sintered metal piece was evaluated based on the following criteria. The obtained results are shown in Table 1. In addition, it was set as the pass when the following A or B criteria were satisfied.
A: Less than 10% B: 10% or more and less than 20% C: 20% or more and less than 90% D: 90% or more

(Connection reliability evaluation)
About Example and the comparative example 2, the part except the heat sinking surface of the copper substrate was sealed with the sealing material (sealing resin). As the sealing material, a solid sealing material manufactured by Hitachi Chemical Co., Ltd. (CEL-400ZHF16, glass transition temperature 204 ° C., inorganic filler-containing epoxy resin, elastic modulus 17.1 GPa, linear expansion coefficient 10.2 × 10 ⁻⁶ / ° C) was used. Sealing was performed using a tonlas fur mold apparatus under conditions of a mold temperature of 180 ° C., a molding pressure of 6.9 MPa, and a curing heating time of 90 seconds. Then, the sealing material was hardened by heating the sample after sealing in 175 degreeC oven for 6 hours. Thereby, the sealing sample of each example was produced.

  The temperature cycle test was implemented with respect to the obtained sealing sample. The sealed sample (package) was subjected to a temperature cycle by hot air and cold air in the test tank. First, warm air was blown for 15 minutes so that the inside of the test tank was maintained at 200 ° C. ± 5 ° C. for 5 minutes or more. Next, cold air was blown for 15 minutes so that the inside of the test tank was held at −40 ° C. ± 5 ° C. for 5 minutes or more. This was regarded as one temperature cycle, and the temperature cycle test was conducted up to 1000 times. The adhesion area ratio of the sintered metal layer was calculated by SAM observation (Scanning Acoustic Microscope) at the time points of 400 and 1000 times of the temperature cycle, and the connection reliability was evaluated. The specific evaluation method is as follows.

First, before the temperature cycle test, an ultrasonic wave of 35 MHz is irradiated from the copper substrate side of the sealing sample, and the ultrasonic wave reflected by the sintered metal layer is measured, so that a reference SAM image (sintered metal layer) The adhesion area SDB is shown). Next, after 400 temperature cycles, a SAM image of the sintered metal layer was similarly taken. The area SA where the contrast became brighter than the SAM image before the temperature cycle test was evaluated. After subtracting SA from SDB, it was divided by SDB to calculate the adhesion area ratio S400 (%) of the sintered metal layer. Next, a SAM image of the sintered metal layer was similarly taken after 1000 temperature cycles. The area SA where the contrast became brighter than the SAM image before the temperature cycle test was evaluated. After subtracting SA from SDB, it was divided by SDB to calculate the adhesion area ratio S1000 (%) of the sintered metal layer. And connection reliability was evaluated based on the following reference | standard. The obtained results are shown in Table 2. In addition, it was set as the pass when the following A or B criteria were satisfied.
A: Adherence area ratio is 90% or more B: Adhesion area ratio is 70% or more and less than 90% C: Adhesion area ratio is 30% or more and less than 70% D: Adhesion area ratio is less than 30%

(Cross section observation)
The cross-sectional observation was performed about the sealing sample of the Example prepared by connection reliability evaluation. First, using Refine So Excel (Refine Tech Co., Ltd.) equipped with a resinoid cutting wheel, the sealed sample (here, Example 7) was cut near the cross section to be observed. The cross section was shaved with a polishing apparatus (Refine Polisher HV, manufactured by Refinetech Co., Ltd.) equipped with water-resistant abrasive paper (Carbo Mac paper, manufactured by Refinetech Co., Ltd.), and a cross section of the Si chip was obtained. Excess sealing material was scraped off in the same manner. Thereafter, the cross-section was smoothed with a polishing apparatus in which a buffing cloth soaked with a buffing abrasive was set to obtain a sample for SEM. This SEM sample was observed and imaged with an SEM device (ESEM XL30, manufactured by Philips) under the condition of an applied voltage of 10 kV. FIG. 3 is a cross-sectional SEM image of the sealed sample of the example. As shown in FIG. 3, in the sealing sample of the example, the semiconductor element (Si chip) 2 and the semiconductor element mounting support member (copper substrate) 3 have substantially the same area as the bonding surface of the semiconductor element 2. It was found that they were joined by the sintered product (sintered metal layer) 1 and sealed by the sealing material 6.

  As shown in the examples, by carrying out an appropriate drying step before sintering joining, (excess) residual sintered metal pieces around the sintered metal layer could be suitably removed after sintering joining. Thereby, a sintered metal layer having substantially the same area as the semiconductor element can be formed, and the connection reliability of the semiconductor device is improved. On the other hand, as shown in Comparative Example 1, when the drying step was not performed, the remaining sintered metal piece could not be sufficiently removed. In Comparative Example 2, no sintered metal piece was observed around the sintered metal layer, but the connection reliability was low.

  DESCRIPTION OF SYMBOLS 1 ... Sintered material (sintered metal layer) of sinterable joining material, 2 ... Semiconductor element, 3 ... Support member for mounting semiconductor element, 2a ... Joining surface of semiconductor element, 4 ... Wire, 5 ... Lead frame, 6 ... Sealant, 100, 110 ... Semiconductor device.

Claims (4)

It is a step of placing a semiconductor element on a semiconductor element mounting support member via a sinterable bonding material containing metal particles and a dispersion medium, and the outer periphery of the sinterable bonding material is the semiconductor in plan view A mounting step larger than the outer periphery of the element;
A drying step of removing at least a part of the dispersion medium from the sinterable bonding material existing beyond the outer periphery of the semiconductor element;
Heating the sinterable bonding material, and bonding the semiconductor element mounting support member and the semiconductor element via a sintered product of the sinterable bonding material;
A removal step of removing the sintered product of the sinterable bonding material, which exists beyond the outer peripheral edge of the semiconductor element;
A method for manufacturing a semiconductor device.   The manufacturing method according to claim 1, wherein the metal particles include copper particles, and the content of the copper particles is 80% by mass or more based on the total mass of the sinterable bonding material.   The copper particles include sub-micro copper particles and flaky micro-copper particles, and the total content of the sub-micro copper particles and the content of the flaky micro-copper particles is 80 mass based on the total mass of the metal particles. The manufacturing method of Claim 2 which is% or more. The manufacturing method according to claim 1, wherein the semiconductor element is a wide band gap semiconductor.