JP7067002B2 - Manufacturing method of semiconductor device - Google Patents

Description

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

In recent years, heat resistance (excellent in stability and reliability under high temperature and high humidity) has been required for semiconductor package materials. For example, in hybrid vehicles, electric vehicles, electric railways, and distributed power sources, power semiconductors are often used for inverters, but the power density is significantly improved and the package material is exposed to high temperatures. In addition, an electronics control unit (ECU) that uses ordinary semiconductor chips used in the car electronics field has been installed in the vehicle interior, but it is being installed in the engine room, which is more harsh, and more. High heat resistance is required. Further, wide bandgap semiconductors (SiC and the like) have also been applied, and are expected to be used for high temperature operation at 200 ° C. or higher.

Under such high temperature conditions, it is difficult to handle with solder that has been used as a joining material for semiconductor devices. Therefore, bonding with a sintered metal obtained by sintering a paste containing fine metal particles has been proposed as a bonding technique for high temperatures (see, for example, Patent Document 1). However, when joining using a paste, the paste protruding from the outer peripheral portion of the semiconductor element at the time of joining may crawl up to the end face of the semiconductor element, resulting in a short circuit of the semiconductor element. Such crawling is particularly remarkable when the semiconductor element is heated while being pressurized in order to improve the adhesiveness with the support member.

Therefore, a method has been proposed in which the coating area of the paste is reduced in advance so that the paste does not protrude from the outer peripheral edge of the semiconductor element at the time of joining (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2007-214340 JP-A-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 / contraction operation according to the respective linear expansion coefficients, a constant load is applied to the peripheral portion of the semiconductor element. Regarding this point, in the method of Patent Document 2, the area of the sintered metal layer which is a sintered product of the paste is smaller than the area of the semiconductor element, and as shown in FIG. 1 of the same document, the peripheral portion of the semiconductor element is covered. No sintered metal layer is formed. If the sintered metal layer is not formed on the peripheral edge of the semiconductor element, interface peeling may occur 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 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 mounting a semiconductor element on a support member for mounting a semiconductor element via a sinterable bonding material containing metal particles and a dispersion medium, and is an outer peripheral edge of the sinterable bonding material in a plan view. A mounting process in which is larger than the outer peripheral edge of the semiconductor element, a drying process in which 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, and a sinterable bonding material. A joining process in which a support member for mounting a semiconductor element and a semiconductor element are joined via a sintered body of a sinterable joining material, and a sinterable joining existing beyond the outer peripheral edge of the semiconductor element. Provided is a method for manufacturing a semiconductor device, comprising a removal step of removing a sintered material of a material.

In the present invention, a drying step is indispensable before proceeding with sintering of the sinterable bonding material. As a result, especially in the sinterable bonding material existing beyond the outer peripheral edge of the semiconductor element, the dispersion medium contained in the material is volatilized. Even if the deposited layer of metal particles in which the dispersion medium is volatilized is sintered, sufficient flexibility and adhesion cannot be obtained. That is, when the temperature of the deposited layer is raised from room temperature to several hundred degrees, which is the firing temperature, the deposited layer cannot be fixed on the support member for mounting the semiconductor element due to the displacement caused by the difference in the coefficient of thermal expansion, and the metal sintered piece. Become. The metal sintered pieces can be suitably removed by the removing step. In the obtained semiconductor device, the sinterable bonding material does not crawl up to the end of the semiconductor element, and the semiconductor element and the support member for mounting the semiconductor element are baked in substantially the same area as the bonding surface of the semiconductor element. It will be joined by a bond. All of them solve the conventional problems, and it can be said that the present invention can provide a method for manufacturing a semiconductor device having excellent connection reliability.

In the present invention, it is preferable that 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.

In the present invention, the copper particles include sub-micro copper particles and flake-shaped micro copper particles, and the total content of the sub-micro copper particles and the flake-shaped micro copper particles is 80 mass based on the total mass of the metal particles. It may be% or more.

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

According to the present invention, it is possible to provide a method for manufacturing a semiconductor device having excellent connection reliability.

It is a schematic sectional drawing 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 sectional drawing which shows the other example of the semiconductor device obtained by the manufacturing method of the semiconductor device which concerns on this embodiment. 6 is a cross-sectional SEM image of the sealed sample of the example.

Hereinafter, embodiments 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 designated by the same reference numerals, and duplicate description will be omitted.

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

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

(Metal particles)
Examples of the metal particles according to the present embodiment include submicro copper particles, flake-shaped micro copper particles, copper particles other than these, and other metal particles.

(Sub-micro copper particles)
Examples of the sub-micro copper particles include 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 may be used. can. When the volume average particle size of the sub-micro copper particles is 0.12 μm or more, the effects of suppressing the synthesis cost of the sub-micro copper particles, good dispersibility, and suppressing the amount of the surface treatment agent used can be easily obtained. When the volume average particle size of the sub-micro copper particles is 0.8 μm or less, the effect of excellent sinterability of the sub-micro copper particles can be easily obtained. From the viewpoint of further exerting the above effect, the volume average particle size of the submicro 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 may be 0. It may be .2 μm or more and 0.5 μm or less, and may be 0.3 μm or more and 0.45 μm or less.

In the specification of the present application, the volume average particle diameter means a 50% volume average particle diameter. When determining the volume average particle size of copper particles, the copper particles used as a raw material or dried copper particles obtained by removing volatile components from a metal paste are dispersed in a dispersion medium using a dispersant, and the particle size distribution is measured by the light scattering method. It can be obtained 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 a light scattering method particle size distribution measuring device is used, 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 of copper particles having a particle size of 0.12 μm or more and 0.8 μm or less, and can contain 30% by mass or more, 100. Can contain% by weight. 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 submicro 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 more suppressed.

The particle size of the copper particles can be calculated, for example, from a scanning electron microscope (SEM) image. The powder of copper particles is placed on a carbon tape for SEM with a spatula to prepare a sample for SEM. This SEM sample is observed with an SEM device at a magnification of 5000. A quadrangle circumscribing the copper particles of this SEM image is drawn by image processing software, and one side thereof is used 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, and 35% by mass or more, based on the total mass of the metal particles. It may be 85% by mass or less, and may be 40% by mass or more and 80% by mass or less. 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) having excellent 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 of the mass of the sub-micro copper particles and the mass of the flake-shaped micro copper particles. When the content of the sub-micro copper particles is 20% by mass or more, the space between the flake-shaped micro-copper particles can be sufficiently filled, and it becomes easy to form a sintered body having excellent bondability. When the content of the sub-micro copper particles is 90% by mass or less, the volume shrinkage when the metal paste is sintered can be sufficiently suppressed, so that it becomes easy to form a sintered body 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 of the mass of the sub-micro copper particles and the mass of the flake-shaped micro copper particles. It may be 35% by mass or more and 85% by mass or less, or 40% by mass or more and 80% by mass or less.

The shape of the sub-micro copper particles is not particularly limited. Examples of the shape of the submicro copper particles include spherical, lumpy, needle-like, flake-like, substantially spherical, and aggregates thereof. From the viewpoint of dispersibility and filling property, the shape of the sub-micro copper particles may be spherical, substantially spherical, or flake-shaped, and from the viewpoint of flammability, dispersibility, mixing with flake-shaped microparticles, and the like, the shape is spherical. Alternatively, it may be substantially spherical.

The sub-micro copper particles may have an aspect ratio of 5 or less or 3 or less from the viewpoint of dispersibility, filling property, and mixing property with flake-shaped micro particles. As used herein, the "aspect ratio" refers to the long side / thickness of the particles. The measurement of the long side and the thickness of the particle can be obtained, for example, from the SEM image of the particle.

The submicro copper particles may be treated with a specific surface treatment agent. Specific surface treatment agents include, for example, organic acids having 8 to 16 carbon atoms. Examples of the organic acid having 8 to 16 carbon atoms include capric acid, methylheptanic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid and ethyl. Octanoic acid, propylheptanic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanic acid, lauric acid, methylundecanoic acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, pentylheptanic 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, hexyloctanoic acid, pentadecanoic acid , Methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecane Acid, heptyl nonanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, nonylcyclohexanecarboxylic acid, etc. Saturated fatty acids of Aromas such as acid, pyromellitic acid, o-phenoxy benzoic acid, methyl benzoic acid, ethyl benzoic acid, propyl benzoic acid, butyl benzoic acid, pentyl benzoic acid, hexyl benzoic acid, heptyl benzoic acid, octyl benzoic acid, nonyl benzoic acid, etc. Group carboxylic acids include. As the organic acid, one kind may be used alone, or two or more kinds may be used in combination. By combining such an organic acid with the above-mentioned sub-micro copper particles, there is a tendency that both the dispersibility of the sub-micro copper particles and the desorption property of the organic acid at the time of sintering can be achieved at the same time.

The treatment amount of the surface treatment agent may be an amount that adheres to the surface of the sub-micro copper particles in a single-layer to a triple-layer. This amount is 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. It can be calculated from the unit g / mol), the minimum coating area of the surface treatment agent ( _SS ) (unit m ² / piece), and the Avogadro's number ( _NA ) (6.02 × 10 ²³ pieces). Specifically, the treatment amount of the surface treatment agent is the treatment amount of the surface treatment agent (mass%) = {(n · A _p · M _s ) / ( _SS · NA + n · _{A p} · M _s )}. It is calculated according to the formula 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 measuring method. The minimum coverage area of the surface treatment agent is 2.05 × 10 ^-19 m ^2/1 molecule when the surface treatment agent is a linear saturated fatty acid. In the case of other surface treatment agents, for example, calculation from a molecular model or "Chemistry and Education" (Ashihiro Ueda, Sumio Inafuku, Iwao Mori, 40 (2), 1992, p114-117). It can be measured by the method described. An example of a method for quantifying a surface treatment agent is shown. The surface treatment agent can be identified by a heat 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 ratio of the surface treatment agent can be analyzed by carbon content analysis. Examples of the carbon content analysis method include a high frequency induction heating furnace combustion / infrared absorption method. The amount of the surface treatment agent can be calculated from the carbon number, molecular weight and carbon content ratio of the identified surface treatment agent by the above formula.

The treatment amount of the surface treatment agent may be 0.07% by mass or more and 2.1% by mass or less, 0.10% by mass or more and 1.6% by mass or less, or 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. Examples of commercially available sub-micro copper particles include CH-0200 (manufactured by Mitsui Metal Mining Co., Ltd., volume average particle size 0.36 μm) and HT-14 (manufactured by Mitsui Metal Mining Co., Ltd., volume average particle size 0. 41 μm), CT-500 (manufactured by Mitsui Metal Mining Co., Ltd., volume average particle size 0.72 μm), Tn-Cu100 (manufactured by Taiyo Nisshi Co., Ltd., volume average particle size 0.12 μm).

(Flake-shaped micro copper particles)
Examples of the flake-shaped micro copper particles include 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, an average maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of 4 are included. The above copper particles can be used. If the average maximum diameter and aspect ratio of the flake-shaped microcopper 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 body having excellent bondability. Become. From the viewpoint of further exerting the above effect, the average maximum diameter of the flake-shaped microcopper 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 flake-shaped micro copper particles can be obtained, for example, from the SEM image of the particles, and is obtained as the major axis X and the average value Xav of the major axis of the flake-shaped structure described later.

The flake-shaped 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 body, reinforcing effect, and filling property of the bonding paste, the flake-shaped 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. The above can be contained, and 100% by mass can be contained. From the viewpoint of suppressing bonding defects, the flake-shaped microcopper particles preferably do not contain particles having a size exceeding the bonding thickness, such as particles having a maximum diameter of more than 20 μm.

An example is a method of calculating the major axis X of flake-shaped micro copper particles from an SEM image. The powder of flake-shaped micro copper particles is placed on a carbon tape for SEM with a spatula to prepare a sample for SEM. This SEM sample is observed with an SEM device at a magnification of 5000. A rectangle circumscribing the flake-shaped microcopper 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. Using a plurality of SEM images, this measurement is performed on 50 or more flake-shaped microcopper particles, and the mean value Xav of the major axis is calculated.

The flake-shaped microcopper particles may have an aspect ratio of 4 or more, or may be 6 or more. When the aspect ratio is within the above range, the flake-shaped microcopper 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 and the bonding can be performed. It becomes easy to form a sintered product having excellent properties.

The content of the flake-shaped microcopper 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, or 20% by mass, based on the total mass of the metal particles. It may be 50% by mass or less. When the content of the flake-shaped micro copper particles is within the above range, it becomes easy to form a sintered body having excellent bondability.

The total content of the sub-micro copper particles and the content of the flake-shaped micro copper particles may be 80% by mass or more based on the total mass of the metal particles. When the total content of the sub-micro copper particles and the flake-shaped micro-copper particles is within the above range, it becomes easy to form a sintered body having excellent bondability. From the viewpoint of further exerting the above effect, the total content of the sub-micro copper particles and the content of the flake-shaped micro copper particles may be 90% by mass or more based on the total mass of the metal particles, and may be 95. It may be 100% by mass or more, or 100% by mass.

In the flake-shaped micro copper particles, the presence or absence of treatment with the surface treatment agent is not particularly limited. From the viewpoint of dispersion stability and oxidation resistance, the flake-shaped microcopper particles may be treated with a surface treatment agent. The surface treatment agent may be one that is removed at the time of joining. Examples of such surface treatment agents include fatty 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; and cetyl alcohols. , Fatty alcohols such as stearyl alcohol, isobornylcyclohexanol, tetraethyleneglycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine, stearylamine; fats such as stearonitrile and decanitrile. Group nitriles; silane coupling agents such as alkylalkoxysilanes; polymer-treated materials such as polyethylene glycols, polyvinyl alcohols, polyvinylpyrrolidones and silicone oligomers. As the surface treatment agent, one type may be used alone, or two or more types may be used in combination.

The treatment amount of the surface treatment agent may be an amount of one molecular 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 flake-shaped microcopper 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 flake-shaped microcopper particles, the molecular weight of the surface treatment agent, and the minimum coating area of the surface treatment agent can be calculated by the above-mentioned method.

When the metal paste is prepared only from the above-mentioned sub-micro copper particles, the volume shrinkage and the sintering shrinkage due to the volatilization of the dispersion medium are large, so that the metal paste is easily peeled off from the adherend surface at the time of sintering, and the semiconductor element or the like is bonded. In, it is difficult to obtain sufficient die-share strength and connection reliability. By using the sub-micro copper particles and the flake-shaped micro-copper particles in combination, the volume shrinkage when the metal paste is sintered is suppressed, and it becomes easy to form a sintered body having excellent bondability.

As the flake-shaped microcopper particles according to the present embodiment, commercially available ones can be used. Examples of commercially available flake-shaped micro copper particles include MA-C025 (manufactured by Mitsui Metal Mining Co., Ltd., average maximum diameter 4.1 μm) and 3L3 (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., average maximum diameter 7.3 μm). ), 1110F (manufactured by Mitsui Metal Mining Co., Ltd., average maximum diameter 5.8 μm), 2L3 (manufactured by Fukuda Metal Foil Powder Industry 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. This makes it easy to form a sintered product having excellent bondability.

(Other metal particles other than copper particles)
The metal particles may include the above-mentioned sub-micro copper particles and other metal particles other than the micro-copper particles, and may include, for example, particles such as nickel, silver, gold, palladium, and platinum. The volume average particle diameter of the other metal particles may be 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 and 10% by mass or less based on the total mass of the metal particles from the viewpoint of obtaining sufficient bondability. You may. Other metal particles may not be included. The shape of the other metal particles is not particularly limited.

By containing metal particles other than copper particles, it is possible to obtain a sintered body in which a plurality of types of metals are solid-dissolved or dispersed, so that mechanical properties such as yield stress and fatigue strength of the sintered body are improved. Connection reliability is likely to improve. Further, the sintered body formed by adding a plurality of types of metal particles tends to improve the bonding strength and the 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 and polyvalent such as pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, α-terpineol and isobornylcyclohexanol (MTPH). Valuable 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 dibutyl ether, diethylene glycol. Butylmethyl ether, diethylene glycol isopropylmethyl ether, triethylene glycol dimethyl ether, triethylene glycol butylmethyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, di Ethers such as propylene glycol dimethyl ether, tripropylene glycol methyl ether, tripropylene glycol dimethyl ether; ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), lactic acid Ethers such as ethyl, butyl lactate, γ-butyrolactone, propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide; cyclohexanone, octane, nonane, decane, Examples thereof include aliphatic hydrocarbons such as undecane; aromatic hydrocarbons such as benzene, toluene and xylene; mercaptans having an alkyl group having 1 to 18 carbon atoms; and mercaptans having a cycloalkyl group having 5 to 7 carbon atoms. 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, and 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 the total mass of the metal particles being 100 parts by mass. When the content of the dispersion medium is within the above range, the metal paste can be adjusted to a more appropriate viscosity, and the sintering of copper particles is less likely to be hindered.

(Additive)
If necessary, a wetting improver such as a nonionic surfactant or a fluorine-based surfactant; a defoaming agent such as silicone oil; an ion trapping agent such as an inorganic ion exchanger is appropriately added to the metal paste. May be 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 with a dispersion medium. After mixing each component, stirring treatment may be performed. For the metal paste, the maximum particle size of the dispersion may be adjusted by a classification operation.

For the metal paste, the sub-micro copper particles, the surface treatment agent, and the dispersion medium are mixed in advance, and the dispersion treatment is performed to prepare a dispersion liquid of the sub-micro copper particles, and further, the micro copper particles, other metal particles, and any addition are performed. The agents may be mixed and prepared. By performing such a procedure, the dispersibility of the sub-micro copper particles is improved, the mixing property with the micro-copper particles is improved, and the performance of the metal paste is further improved. The aggregate may be removed by performing a classification operation on the dispersion liquid of the submicro copper particles.

<Manufacturing method of semiconductor devices>
The method for manufacturing a semiconductor device according to the present embodiment includes a mounting step of mounting the semiconductor element on a support member for mounting the semiconductor element via a sinterable bonding material containing metal particles and a dispersion medium, and a semiconductor element. A drying step of 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 heating the sinterable bonding material to form a support member for mounting a semiconductor element and a semiconductor element. It includes a joining step of joining the sinterable joining material via a sintered body and a removing step of removing the sintered body of the sinterable joining material existing beyond the outer peripheral edge of the semiconductor element.

(Placement process)
The method of providing the sinterable bonding material on the support member for mounting the semiconductor element is not particularly limited as long as it is a method of depositing the sinterable bonding material. Examples of such a method include screen printing, transfer printing, offset printing, jet printing method, dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, slit coat, letterpress printing, ingot printing, and gravure. Printing, stencil printing, soft lithograph, bar coat, 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, and 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 a plan view. As a result, a part of the sinterable bonding material is in a state of "protruding" from the bonding surface of the semiconductor element. The sinterable bonding material is the outer 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. It can be provided so as to protrude preferably at least 1 mm, more preferably at least 5 mm. In consideration of the sizes of general semiconductor elements and support members for mounting semiconductor elements, the upper limit of the protrusion width can be about 20 mm.

Examples of the method for mounting the semiconductor element on the sinterable bonding material include a chip mounter, a flip chip bonder, and a positioning jig made of carbon or ceramics.

By this step, a precursor laminate in which a semiconductor element, a sinterable bonding material having an area exceeding the bonding area of the semiconductor element, and a support member for mounting the semiconductor element are laminated in this order on the side in the direction in which the weight of the semiconductor element works is produced. Obtainable.

(Drying process)
In this step, the precursor laminate obtained by the mounting step is subjected to a drying treatment. This removes at least a portion of the dispersion medium, in particular, from the sinterable bonding material that exists beyond the outer peripheral edge of the semiconductor device.

The gas atmosphere in the drying step may be in the atmosphere, in an oxygen-free atmosphere such as nitrogen or noble gas, or in a reducing atmosphere such as hydrogen or formic acid. As the drying treatment, normal temperature drying may be performed, heating drying may be performed, vacuum drying may be performed, or drying may be performed at room temperature or by a combination of heating drying and vacuum drying. For heating drying and vacuum drying, for example, a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far infrared heating furnace, a microwave heating device, a laser heating device, etc. An electromagnetic heating device, a heater heating device, a steam heating furnace, a hot plate pressing device, or the like can be used.

When, for example, heating and drying is performed as the drying treatment, the heating temperature and time may be appropriately adjusted according to the type and amount of the dispersion medium used. The heating temperature and time can be 50 ° C. or higher and 230 ° C. or lower, respectively, for 1 minute or longer and 120 minutes or shorter.

(Joining process)
In this step, the sinterable bonding material is sintered by heat-treating the precursor laminate that has undergone the drying step. For heat treatment, for example, a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, etc. A heater heating device, a steam heating furnace, or the like can be used.

The gas atmosphere in the joining step may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the sintered body, the semiconductor element, and the support member for mounting the semiconductor element. The gas atmosphere in the bonding step may be a reducing atmosphere from the viewpoint of removing oxides on the surface of metal particles contained in the sinterable bonding material. Examples of the oxygen-free atmosphere include an oxygen-free gas atmosphere such as nitrogen and a rare gas, or a vacuum atmosphere. Examples of the reducing atmosphere include a pure hydrogen gas atmosphere, a mixed gas atmosphere of hydrogen and nitrogen typified by forming gas, a nitrogen atmosphere containing formic acid gas, a mixed gas atmosphere of hydrogen and rare gas, a rare gas atmosphere containing formic acid gas, and the like. Can be mentioned.

The maximum temperature reached during the heat treatment may be 250 ° C. or higher and 450 ° C. or lower, and 250 ° C. or higher and 400 ° C. from the viewpoint of reducing heat damage to the semiconductor device and the support member for mounting the semiconductor device and improving the yield. It may be the following, and may be 250 ° C. or higher and 350 ° C. or lower. When the maximum ultimate temperature is 250 ° C. or higher, sintering tends to proceed sufficiently when the maximum ultimate temperature retention time is 60 minutes or less.

The maximum temperature retention time may be 1 minute or more and 60 minutes or less, and 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 body is 65% by volume or more based on the total volume of the sintered body. For example, by using the predetermined sinterable bonding material containing sub-micro copper particles, flake-shaped micro-copper particles, etc. described above, a sintered body having excellent bondability without pressure during bonding. Can be formed. In this case, sufficient bonding strength is obtained only by the weight of the semiconductor element existing on the sinterable bonding material, or when a pressure of 0.01 MPa or less, preferably 0.005 MPa or less is further applied to the weight of the semiconductor element. be able to. In this case, since a special pressurizing device is not required, voids can be reduced, joint strength and connection reliability can be further improved without impairing the yield. Examples of the 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 the density of the sintered product, the bonding paste may be pressurized via the semiconductor element. The pressurizing pressure can be 0.01 MPa or more and 10 MPa or less. At a low pressure of about 0.01 MPa or more and 0.1 MPa or less, it is expected that the yield will be improved by suppressing joint defects such as peeling. On the other hand, if it is 1 MPa or more and 10 MPa or less, it is expected that the bonding strength will be further improved and the thermal conductivity will be improved by improving the density of the sintered body. Examples of the pressurizing method include a weight, a spring jig, a pressurizing jig using silicone rubber, a thermocompression bonding device, and a hot plate pressing device.

(Removal process)
In this step, among the sintered matter formed by the joining step, the sintered matter (sintered metal piece) existing beyond the outer peripheral edge of the semiconductor element in a plan view is removed. That is, the sintered material that does not contribute to joining, which is formed from the portion of the sinterable joining material that protrudes from the joining surface of the semiconductor element, is removed. This prevents malfunction due to such sintered matter falling off. This step can be carried out using, for example, an air gun, an adhesive sheet, an adhesive tape, or the like.

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

In addition to general semiconductor materials such as silicon (Si), wide bandgap semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) can be used for the semiconductor element 2 without particular limitation. .. Specific examples of the semiconductor element 2 include semiconductor elements such as IGBTs, diodes, shotkey barrier diodes, MOS-FETs, thyristors, logics, sensors, analog integrated circuits, LEDs, semiconductor lasers, and transmitters. The support member 3 for mounting a semiconductor element includes a lead frame, a ceramic substrate attached to a metal plate (for example, DBC), a base material for mounting a semiconductor element such as an LED package, metal wiring such as a copper ribbon and a metal frame, and a metal block. Examples include a block body, a power feeding member such as 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. In the semiconductor device 110 shown in FIG. 2, the semiconductor element 2 and the support member 3 for mounting the semiconductor element are bonded to each other by a sintered body (sintered metal layer) 1 of a sinterable bonding material, and then the terminal on the upper part of the semiconductor element 2 is bonded. It is obtained by connecting (not shown) to the lead frame 5 with a wire 4 and finally covering the whole with an insulating sealing material 6.

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

<Example 1>
(Preparation of metal paste)
5.2 g of α-terpineol (manufactured by Wako Pure Chemical Industries, Ltd.) and 6.8 g of isobornylcyclohexanol (MTPH, manufactured by Nippon Terpen Chemical Co., Ltd.) as dispersion media, and CH-0200 (Mitsui Metals) as sub-micro copper particles. Mix 52.8 g of copper particles of 0.12 μm or more and 0.8 μm or less (95% by mass) manufactured by Mining Co., Ltd. in a plastic bottle, and use an ultrasonic homogenizer (US-600, manufactured by Nippon Seiki Co., Ltd.) 19 Treatment was performed at 0.6 kHz, 600 W for 1 minute to obtain a dispersion. In this dispersion, MA-C025 (manufactured by Mitsui Mining & Smelting Co., Ltd., having an average maximum diameter of 4.1 μm and an aspect ratio of 6.6, content of copper particles of 100% by mass) 35.2 g as flake-shaped micro copper particles. Was added and stirred with a spatula until the dry powder was gone. The plastic bottle is tightly closed, and the metal paste (sintering) is stirred at 2000 rpm for 2 minutes using a rotating / revolving stirring device (Planetry Vacuum Mixer ARV-310, manufactured by Shinky Co., Ltd.), and under reduced pressure for 2 minutes at 2000 rpm. Copper paste) was obtained.

(Placement process)
A copper substrate with a size of 19 mm x 25 mm x 3 mm (thickness) and a Si chip with a size of 5 mm x 5 mm x 150 μm (thickness) in which a titanium layer / nickel layer is provided in this order by sputtering on the entire surface of the joint surface. Prepared. The metal paste was stencil-printed on a copper substrate using a 100 μm thick stainless steel mask and squeegee with a 10 mm × 10 mm square opening. The Si chip was placed on the printed matter of the metal paste so that the nickel layer was in contact with the metal paste. The Si chip was lightly pressed with tweezers to bring the Si chip into close contact with the metal paste. As a result, a precursor laminate was obtained.

(Drying process)
The precursor laminate obtained in the mounting step was heated in the air at 160 ° C. for 5 minutes using a warm air dryer (manufactured by Espec). After that, the hot air dryer was stopped, and the precursor laminate was put out after the temperature inside the hot air dryer became 100 ° C. or lower. As a result, at least a part of the dispersion medium was removed from the metal paste protruding from the joint surface of the Si chip in particular.

(Joining process)
The precursor laminate that had undergone the drying step was set in a tube furnace (manufactured by ABC Co., Ltd.), and argon gas was flowed at 1 L / min to replace the air with argon gas. Then, the metal paste was sintered by heat treatment under the conditions that the temperature was raised to 350 ° C. for 10 minutes while flowing hydrogen gas at 300 mL / min and the temperature was maintained at 350 ° C. for 10 minutes. As a result, a laminated body in which the copper substrate and the Si chip were joined via a sintered metal layer which is a sintered product of the metal paste was obtained. Then, the mixture was cooled while flowing argon gas at 0.3 L / min, and the laminate was taken out into the air at 50 ° C. or lower.

(Removal process)
Among the sintered products formed by the joining step, the sintered products (sintered metal pieces) existing beyond the outer peripheral edge of the Si chip were removed. The removal was carried out by performing a nitrogen blow using an air gun (manufactured by AS ONE) for 10 to 120 seconds.

<Examples 2 to 8 and Comparative Example 1>
The mounting step to the removing step were carried out in the same manner as in Example 1 except that the atmosphere, the heating temperature and the heating time in the drying step were changed as shown in Table 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 10 mm × 10 mm square opening was used instead of a 100 μm-thick stainless steel mask having a 3 mm × 3 mm square opening. The process-joining process was carried out.

<Various evaluations>
(Evaluation of removability of sintered metal pieces)
A digital microscope (manufactured by Keyence Co., Ltd.) is used to determine what percentage of the area where the metal paste is applied (excluding the chip area) is the area of the sintered metal pieces that remain unremoved after the removal process. It was observed and evaluated using. Then, the removability of the sintered metal piece was evaluated based on the following criteria. The results obtained are shown in Table 1. In addition, when the following criteria A or B were satisfied, it was judged as a pass.
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)
In Examples and Comparative Example 2, the portion of the copper substrate excluding the heat dissipation surface was sealed with a sealing material (sealing resin). The encapsulant is a solid encapsulant manufactured by Hitachi Kasei Co., Ltd. (CEL-400ZHF16, glass transition temperature 204 ° C., epoxy resin containing inorganic filler, elastic modulus 17.1 GPa, linear expansion coefficient 10.2 × ^10-6 / ℃) was used. Sealing was performed using a tonlas fur mold device under the 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 sealed sample was heated in an oven at 175 ° C. for 6 hours to cure the sealing material. As a result, a sealed sample of each example was prepared.

A temperature cycle test was performed on the obtained sealed sample. In the test chamber, the sealed sample (package) was given a temperature cycle by hot and cold air. First, warm air was blown for 15 minutes so that the inside of the test tank was held 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 longer. This was set as one temperature cycle, and the temperature cycle test was carried out 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 times 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, a reference SAM image (sintered metal layer) is obtained by irradiating 35 MHz ultrasonic waves from the copper substrate side of the sealed sample and measuring the ultrasonic waves reflected by the sintered metal layer. The close contact area SDB) was imaged. Next, after 400 temperature cycles, a SAM image of the sintered metal layer was similarly imaged. The area SA of the portion where the contrast became brighter than that of 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, after 1000 temperature cycles, a SAM image of the sintered metal layer was similarly imaged. The area SA of the portion where the contrast became brighter than that of 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. Then, the connection reliability was evaluated based on the following criteria. The results obtained are shown in Table 2. In addition, when the following criteria A or B were satisfied, it was judged as a pass.
A: Adhesion 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)
Cross-section observation was performed on the sealed sample of the example prepared in the connection reliability evaluation. First, using Refine Saw Excel (manufactured by 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 cut with a polishing device (Refine Polisher HV, manufactured by Refine Tech Co., Ltd.) equipped with water-resistant polishing paper (Carbomac Paper, manufactured by Refine Tech Co., Ltd.) to obtain the cross section of the Si chip. The excess encapsulant was scraped off in the same way. Then, the cross section was smoothed with a polishing device set with a buffing cloth impregnated with a buffing agent to prepare a sample for SEM. This SEM sample was observed and imaged by 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 encapsulation sample of the embodiment, 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 a sintered product (semiconductor layer) 1 and they were sealed by a sealing material 6.

As shown in the examples, by carrying out an appropriate drying step before the sintering and joining, the (excessive) residual sintered metal pieces around the metal sintered layer could be suitably removed after the sintering and joining. As a result, a metal sintered 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, the residual sintered metal pieces could not be sufficiently removed when the drying step was not carried out. Further, in Comparative Example 2, no sintered metal piece was observed around the sintered metal layer, but the connection reliability was low.

1 ... Sintered material of sinterable bonding material (sintered metal layer), 2 ... Semiconductor element, 3 ... Support member for mounting semiconductor element, 2a ... Joint surface of semiconductor element, 4 ... Wire, 5 ... Lead frame, 6 ... Encapsulant, 100, 110 ... Semiconductor device.

Claims (4)

This is a step of mounting a semiconductor element on a support member for mounting a semiconductor element via a sinterable bonding material containing metal particles and a dispersion medium. In a plan view, the outer peripheral edge of the sinterable bonding material is the semiconductor. The mounting process, which is larger than the outer peripheral edge of the device,
After the above-mentioned setting step, a drying step of 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 drying step.
After the drying step, the sinterable joining material is heated to join the semiconductor element mounting support member and the semiconductor element via a sintered body of the sinterable joining material.
A method for manufacturing a semiconductor device, comprising : after the joining step, a removing step of removing a sintered body of the sinterable joining material existing beyond the outer peripheral edge of the semiconductor element. The production method according to claim 1, wherein the metal particles contain 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 flake-shaped micro copper particles, and the total content of the sub-micro copper particles and the flake-shaped micro copper particles is 80 mass based on the total mass of the metal particles. % Or more, the manufacturing method according to claim 2. The manufacturing method according to any one of claims 1 to 3, wherein the semiconductor element is a wide bandgap semiconductor.

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