Alloy powder-containing composition and semiconductor device

Abstract

Provided is an alloy powder-containing composition that complies with environmental regulations, that operates at high temperatures, and that exhibits superior implementability and bonding reliability. An alloy powder-containing composition according to the present disclosure is characterized by including an alloy powder having an AgSi eutectic structure, silver (Ag) powder, and organic matter. In addition, the content of silver (Ag) relative to the total amount of the alloy powder is preferably 15-97.6 mass%, the content of the silver (Ag) powder is preferably 5-2000 parts by mass with respect to 100 parts by mass of the alloy powder, and the content of silver with respect to the total amount of the alloy powder and the silver (Ag) powder is preferably 20-99.9 mass%.

Description

Alloy powder-containing composition and semiconductor device

[0001] This disclosure relates to an alloy powder-containing composition and a semiconductor device. This application claims priority from Japanese Patent Application No. 2023-146496, filed on September 8, 2023, the contents of which are incorporated herein by reference.

[0002] Semiconductors used in power devices are required to have high efficiency, low loss, and high-frequency switching, and the use of wide-gap semiconductors such as SiC and GaN semiconductors is expanding. The operating temperatures of such semiconductors can exceed 200°C, so the bonding materials used for bonding must maintain high bonding reliability even when the semiconductors operate in high-temperature ranges or in harsh temperature cycle environments.

[0003] Furthermore, solder has traditionally been used as a high-temperature resistant joining material, but due to increasingly strict environmental regulations and safety concerns, lead-free materials have become necessary. For example, the materials described in Patent Documents 1 to 3 are known as lead-free solder substitute materials.

[0004] JP 2003-311469 A JP 2020-069517 A JP 2019-56158 A

[0005] However, the lead-free solder of Patent Document 1 has a low melting point, and in particular, there is a problem in that Sn in the solder that has not been converted into a metal compound melts at about 230°C.

[0006] Furthermore, the lead-free solder of Patent Document 2 uses bismuth (Bi) to achieve a high melting point, and although it is possible to achieve a high melting point, there is a problem in that cracks propagate when heated repeatedly, which causes problems with connection reliability.

[0007] Furthermore, the silver (Ag) paste of Patent Document 3 does not melt in an operating environment of about 250°C, but repeated heating causes coarsening of the metal structure and aggregation of voids, resulting in problems with bonding reliability.

[0008] The present disclosure solves the above-mentioned problems, and its purpose is to provide an alloy powder-containing composition that complies with environmental regulations, operates at high temperatures, and is capable of forming a bonding layer that has excellent mountability and bonding reliability. Means to solve the problem

[0009] As a result of earnest efforts to solve the above problems, the present inventors have found that an alloy powder-containing composition containing an alloy powder having an AgSi eutectic structure, silver (Ag) powder, and an organic substance complies with environmental regulations, operates at high temperatures, and has excellent mountability and bonding reliability.

[0010] That is, the present disclosure provides an alloy powder-containing composition that includes an alloy powder having an AgSi eutectic structure, silver (Ag) powder, and an organic substance.

[0011] By containing the alloy powder having the AgSi eutectic structure, silver (Ag) powder, and an organic substance, the silver (Ag) in the AgSi eutectic structure present on the surface can be recrystallized by heating during sintering and can seep out from the alloy powder surface, resulting in excellent mountability. Furthermore, since the alloy powder itself can be made to have a low linear expansion coefficient while firmly bonding to the adherend, it has excellent bonding reliability at high temperatures. Furthermore, since the raw materials are silver (Ag) and silicon (Si), it complies with environmental regulations.

[0012] The alloy powder-containing composition preferably has a silver (Ag) content of 15 to 97.6 mass % relative to the total amount of the alloy powder.

[0013] The alloy powder-containing composition preferably contains 5 to 2000 parts by mass of silver (Ag) powder relative to 100 parts by mass of the alloy powder.

[0014] The alloy powder-containing composition preferably has a silver content of 20 to 99.9 mass % relative to the total amount of the alloy powder and the silver (Ag) powder.

[0015] In the alloy powder-containing composition, the alloy powder preferably has a volume average particle size (median size) of 0.1 to 100 μm.

[0016] The present disclosure also provides a semiconductor device using the above-mentioned bonding layer for bonding a substrate and an object to be bonded.

[0017] The alloy powder-containing composition of the present disclosure can provide a bonding layer that operates at high temperatures and has excellent mountability and bonding reliability while complying with environmental regulations. Therefore, a semiconductor device using the alloy powder-containing composition of the present disclosure can operate at high temperatures and have excellent bonding reliability while complying with environmental regulations.

[0018] 1 is a cross-sectional view of an alloy powder according to the present disclosure, and FIG. 2 is a cross-sectional view of an example of an embodiment of a semiconductor device according to the present disclosure.

[0019] [Alloy Powder-Containing Composition] One embodiment of the present disclosure provides an alloy powder-containing composition containing an alloy powder, silver (Ag) powder, and an organic substance. The alloy powder is made from silver (Ag) and silicon (Si) as raw materials, and therefore complies with environmental regulations. Furthermore, the alloy powder-containing composition can take various forms without particular limitations. For example, an alloy powder-containing composition called alloy ink can be prepared by dispersing the alloy powder in a suspended state in an appropriate organic solvent (dispersion medium). Alternatively, an alloy powder-containing composition called alloy paste can be prepared by dispersing the alloy powder in a kneaded state in an organic solvent. Among these, the alloy powder-containing composition is preferably an alloy paste.

[0020] The alloy powder-containing composition can be sintered at a temperature of preferably 150 to 300° C., more preferably 160 to 280° C., and even more preferably 200 to 270° C. When the alloy powder-containing composition can be sintered at a temperature of 300° C. or less, it can be sintered at a low temperature, allowing the use of a substrate with a low melting point.

[0021] The heating time for sintering the alloy powder-containing composition is preferably 0.5 minutes to 2 hours, more preferably 10 minutes to 1 hour. By keeping the heating time to 2 hours or less, mounting can be performed in a short time, which facilitates reducing manufacturing costs.

[0022] The alloy powder-containing composition is preferably pressurized when heated. Specifically, it is preferably pressurized under conditions of 0.75 to 50 MPa, more preferably 1 to 40 MPa. Furthermore, no pressure may be applied as long as the composition is properly sintered and bonded. By keeping the pressure during mounting within the above range, the composition can be easily mounted.

[0023] The alloy powder-containing composition preferably has a strength retention rate (%) of 50% or more, more preferably 60% or more, and even more preferably 70% or more. A strength retention rate of 50% or more ensures sufficient bonding reliability. While the upper limit is not particularly limited, because the shear bond strength may increase due to a thermal shock test described below, it is preferably 150% or less, more preferably 100% or less. The strength retention rate is calculated as the ratio (shear bond strength after thermal shock test / shear bond strength before thermal shock test × 100) of the shear bond strength measured under the same conditions after a thermal shock test in which the semiconductor device is heated and cooled in the range of −50 to 250°C a specific number of times, measured using a die shear tester (product name "SERIES4000" manufactured by DAGE) at room temperature and a test speed of 50 μm / s on a semiconductor device fabricated using the alloy powder-containing composition under the conditions described in the Examples described below.

[0024] The linear expansion coefficient of the sintered body of the alloy powder-containing composition, as measured with a thermomechanical analyzer (model name "TMA-60", manufactured by Shimadzu Corporation), is preferably 17 or less, more preferably 13 or less, and even more preferably 11 or less. When the linear expansion coefficient is within the above range, it becomes easier to exhibit connection reliability.

[0025] Furthermore, when the alloy powder-containing composition is left at 250°C for 100 hours and the metal structure is observed, it is preferable that no significant coarsening occurs in the metal structure of the alloy powder-containing composition, and more preferably no coarsening occurs.

[0026] <Alloy Powder> One particle is selected from an image taken at a magnification of 2,000 to 50,000 times, and the total perimeter and the length of the outer perimeter where the eutectic structure is present, excluding the region where no eutectic structure is present at all in a region extending from the perimeter to a depth of 0.2 μm toward the center of the particle, are measured, and the ratio of the total perimeter to the total perimeter is calculated as the ratio of the AgSi structure on the particle surface. This method is performed on any 10 adjacent particles, and it is preferable that the ratio of the AgSi eutectic structure is 10% or more in at least 8 of the particles. Only one type of alloy powder may be used, or two or more types may be used in combination.

[0027] 1 and 2 are enlarged SEM images of the cross section of a particle of the alloy powder. The black areas in the images are regions made of silicon (Si), and the white areas are regions made of an AgSi eutectic structure in which silicon (Si) is dispersed in Ag.

[0028] In this disclosure, the term "eutectic structure" refers to a structure unique to eutectic alloys, in which two crystalline phases simultaneously crystallize from the liquid phase at a specific temperature, forming a very fine metal structure. The eutectic structure is formed at a constant composition ratio, and if the composition ratio is different, one crystal will crystallize first and generally grow coarsely. When the composition of the eutectic structure deviates from the ideal, the crystals that crystallize first and grow during cooling from the liquidus temperature to the eutectic temperature are called primary crystals. For example, in an AgSi alloy, if the Si content is in excess of the ideal eutectic structure, Si will crystallize as primary crystals, grow, and only when the AgSi composition in the remaining liquid phase reaches the ideal composition will a fine eutectic structure begin to form. In alloy powders having an AgSi eutectic structure with an excess of Si compared to the eutectic composition ratio, primary Si crystals of several μm in size are dispersed within the particles, and in the AgSi eutectic structure, Si is finely dispersed in Ag at approximately 100 nm or less. Furthermore, when an AgSi alloy contains more Ag than the ideal eutectic structure, Ag crystallizes as primary crystals, grows, and when the AgSi composition in the remaining liquid phase reaches the ideal composition, a fine eutectic structure begins to form. The size of the primary crystals varies depending on the particle size, but crystals with a difference of several to 10 times or more are observed within a single particle, and the larger of these can be identified as primary crystals.

[0029] The method for producing the alloy powder having the above-mentioned eutectic structure is not particularly limited, but it can be produced, for example, by a method in which a mixture of silver (Ag) and silicon (Si) heated until it becomes liquid is pulverized by a gas atomization method or a water atomization method.

[0030] The proportion of the AgSi eutectic structure of the alloy powder measured by the above-mentioned method is more preferably 15% or more, and even more preferably 20% or more. When the proportion of the AgSi eutectic structure on the particle surface is 10% or more, silver (Ag) recrystallizes during sinter bonding and seeps out from the alloy powder surface, thereby enabling sufficient bonding strength to be exerted.

[0031] The silver (Ag) content of the alloy powder is preferably 15 to 97.6 mass%, more preferably 20 to 90 mass%, and even more preferably 30 to 80 mass%. By having a silver (Ag) content of 15 mass% or more, the proportion of eutectic structure on the surface of the alloy powder can be made sufficient. Furthermore, by having a silver (Ag) content of 97.6 mass% or less, the linear expansion coefficient can be made sufficiently low, and manufacturing costs can be kept low while maintaining bonding reliability.

[0032] The silicon (Si) content of the alloy powder is preferably 2.4 to 85 mass%, more preferably 10 to 80 mass%, and even more preferably 20 to 70 mass%. By ensuring that the silicon (Si) content in the alloy powder is 2.4 mass% or more, the linear expansion coefficient can be kept sufficiently low, ensuring bonding reliability while keeping manufacturing costs low. Furthermore, by ensuring that the silicon (Si) content is 85 mass% or less, the proportion of eutectic structures on the alloy powder surface can be made sufficient.

[0033] Furthermore, the alloy powder may contain other components in addition to silver (Ag) and silicon (Si), but from the viewpoint of complying with environmental regulations, being operable at high temperatures, and exhibiting connection reliability, it is preferable that the alloy powder does not contain any components other than silver (Ag) and silicon (Si).

[0034] The total content of silver (Ag) and silicon (Si) in the alloy powder is preferably 90 mass % or more, more preferably 95 mass % or more, and even more preferably 100 mass % based on the total amount of the alloy powder.

[0035] The volume average particle size (median size) of the alloy powder is preferably 0.1 to 100 μm, more preferably 0.3 to 50 μm, even more preferably 0.5 to 10 μm, and particularly preferably 0.5 to 3 μm. A volume average particle size of 0.1 μm or more makes it easy to handle, and a volume average particle size of 100 μm or less ensures sufficient surface area of ​​the alloy powder, making it easy to bond in a short period of time. The volume average particle size (median size) can be measured by laser diffraction / scattering.

[0036] The shape of the alloy powder is not particularly limited, but examples thereof include spherical, flake (flat), polyhedral, etc. Alloy powders of the same shape may be used alone, or alloy powders of different shapes may be used in combination. Of these, spherical shapes are preferred.

[0037] The alloy powder-containing composition contains the organic substance. The organic substance may be used alone or in combination of two or more.

[0038] Examples of the organic substance include organic solvents, binder resins, and additives.

[0039] The organic solvent preferably contains at least organic solvent (a), organic solvent (b), and organic solvent (c). The organic solvents (a), (b), and (c) are different compounds and satisfy the following formulas (1) to (6). Only one type of organic solvent (a), organic solvent (b), and organic solvent (c) may be used, or two or more types may be used. 150°C≦Ta≦250°C (1) 150°C≦Tb≦250°C (2) 250°C≦Tc≦350°C (3) δa≧10.0 (4) δc≦9.0 (5) δc≦δb≦δa (6)

[0040] In the formula, Ta to Tc represent the boiling points of the organic solvents (a) to (c), respectively, and δa to δc represent the Hansen solubility parameters of the organic solvents (a) to (c), respectively. In this specification, the Hansen solubility parameter is sometimes referred to as the "SP value" and abbreviated as "δ."

[0041] The organic solvents (a) to (c) may be any solvents that dissolve uniformly and become liquid when mixed in the compounding ratio used in the above-mentioned bondable conductor paste, and each of them may be liquid or solid at room temperature.

[0042] The organic solvent (a) at least satisfies formula (1). That is, the boiling point Ta of the organic solvent (a) satisfies 150° C.≦Ta≦250° C., preferably 150° C.<Ta<250° C., more preferably 155° C.≦Ta≦220° C., and even more preferably 160° C.≦Ta≦200° C. By using an organic solvent (a) having a boiling point within the above range, the organic solvent is easily volatilized during sintering, and a sintered body can be easily formed.

[0043] The organic solvent (a) at least satisfies the formula (4) [δa≧10.0]. The SP value δa of the organic solvent (a) is 10.0 or more, preferably 10.3 or more, and more preferably 10.4 or more, within the range satisfying the formula (6). When the δa is 10.0 or more, the dispersibility of the alloy powder and the metal particles described below is excellent, and separation of the alloy powder and silver powder from the organic solvent can be made less likely. The δa of the organic solvent (a) is, for example, 16.0 or less, and may be 15.0 or less.

[0044] Examples of the organic solvent (a) include alcohol solvents, urea-based solvents, and aprotic polar solvents. Examples of the alcohol solvent include compounds having one or more hydroxy groups, and among these, tertiary alcohols and ether alcohols are preferred. The alcohol solvent may have two or more hydroxy groups. Examples of the ether alcohol include compounds having an ether bond and a hydroxy group, such as (poly)alkylene glycol monoalkyl ethers and alkoxy-substituted alcohols.

[0045] Specific examples of the organic solvent (a) include pinacol (δ 10.7, boiling point 172°C), tetramethylurea (δ 10.6, boiling point 177°C), 3-methoxybutanol (δ 10.6, boiling point 161°C), 1-methylcyclohexanol (δ 10.4, boiling point 155°C), and methyl carbitol (diethylene glycol monomethyl ether) (δ 10.7, boiling point 193°C).

[0046] The organic solvent (b) at least satisfies formula (2). That is, the boiling point Tb of the organic solvent (b) satisfies 150°C ≦ Tb ≦ 250°C, preferably 150°C < Tb < 250°C, more preferably 180°C ≦ Tb ≦ 248°C, and even more preferably 200°C ≦ Tb ≦ 245°C. By using an organic solvent (b) having a boiling point within the above range, the organic solvent is easily volatilized during sintering, making it easy to form a sintered body. Furthermore, by using an organic solvent (b) having a boiling point of 250°C or less, it is possible to suppress the generation of voids during sintering.

[0047] The organic solvent (b) at least satisfies formula (6). The SP value δb of the organic solvent (b) is preferably 8.0 to 12.0, more preferably 8.5 to 11.0, and even more preferably 9.0 to 10.5, within the range satisfying formula (6). When δb is within the above range, the compatibility of the organic solvent (a) and the organic solvent (c) is improved, they are less likely to separate, and the continuous ejection stability and storage stability tend to be more excellent.

[0048] Examples of the organic solvent (b) include alcohol solvents, ester solvents, ketone solvents, and amine-based solvents. Examples of the alcohol solvent include solvent compounds having one or more hydroxy groups, and among these, tertiary alcohols, ether alcohols, and ester alcohols are preferred. Ether alcohols are compounds having an ether bond and a hydroxy group, such as (poly)alkylene glycol monoalkyl ethers and alkoxy group-substituted alcohols. Ester alcohols are compounds having an ester bond and a hydroxy group, such as (poly)alkylene glycol monoalkyl ether monoesters. Examples of ester solvents include diacetates of diols such as (poly)alkylene glycols. Preferred ketone solvents are cyclic ketones. Preferred amine-based solvents are alkylamines.

[0049] The organic solvent (b) is selected on the premise that it satisfies the formula (6) in relation to the organic solvents (a) and (c). Specific examples of the organic solvent (b) include d-camphor (δ 10.4, boiling point 204°C), 1-heptanol (δ 10.0, boiling point 177°C), butyl carbitol (diethylene glycol monobutyl ether) (δ 10.2, boiling point 231°C), ethyl carbitol (diethylene glycol monoethyl ether) (δ 10.5, boiling point 196°C), tripropylene glycol monomethyl ether (δ 9.4, boiling point 243°C), α-terpineol (δ 9 .3, boiling point 220°C), dihydroterpineol (δ 9.0, boiling point 210°C), 1,3-butanediol diacetate (δ 9.2, boiling point 232°C), propylene glycol diacetate (δ 9.3, boiling point 190°C), butyl carbitol acetate (δ 9.0, boiling point 247°C), dipropylene glycol butyl ether (δ 9.2, boiling point 230°C), isophorone (δ 9.5, boiling point 213°C), 1-decanol (δ 9.6, boiling point 230°C), propylene glycol monobutyl ether (δ 9.0, boiling point 170°C), 1-nonanol (δ 9.8, boiling point 214°C), etc. may be used.

[0050] The boiling point Tb of the organic solvent (b) is preferably higher than the boiling point Ta of the organic solvent (a), i.e., Tb > Ta. The temperature difference between Tb and Ta [Tb - Ta] is preferably 2°C or more, more preferably 5°C or more, and even more preferably 10°C or more. When the temperature difference is 2°C or more, the generation of voids during sintering can be further suppressed.

[0051] The organic solvent (c) at least satisfies formula (3). That is, the boiling point Tc of the organic solvent (c) satisfies 250°C ≦ Tc ≦ 350°C, preferably 250°C < Tc < 350°C, more preferably 250°C < Tc ≦ 320°C, and even more preferably 250°C < Tc ≦ 300°C. By using an organic solvent (c) having a boiling point within the above range, rapid evaporation of the organic solvents (a) and (b) during sintering can be suppressed, and the generation of voids can be suppressed.

[0052] The organic solvent (c) at least satisfies formula (5) [δc≦9.0]. The SP value δc of the organic solvent (c) is 9.0 or less, preferably 8.7 or less, and more preferably 8.5 or less. By making the δc 9.0 or less, it is possible to suppress the generation of voids during sintering. The δc of the organic solvent (c) is, for example, 6.0 or more, and may be 7.0 or more.

[0053] Examples of the organic solvent (c) include ether solvents, alkane solvents, and ester solvents. Examples of the ether solvent include (poly)alkylene glycol dialkyl ethers. Examples of the alkane solvent include alkanes having 14 or more carbon atoms (e.g., 14 to 20 carbon atoms). Examples of the ester solvent include esters of (poly)alkylene glycol alkyl ethers and fatty acids.

[0054] Specific examples of the organic solvent (c) include dibutyl carbitol (diethylene glycol dibutyl ether) (δ 8.3, boiling point 255°C), tetradecane (δ 7.9, boiling point 254°C), and hexadecane (δ 8.0, boiling point 287°C).

[0055] The boiling point Tc of the organic solvent (c) is preferably higher than the boiling point Tb of the organic solvent (b), i.e., Tc > Tb. The temperature difference between Tc and Tb [Tc - Tb] is preferably 2°C or more, more preferably 6°C or more, and even more preferably 10°C or more. When the temperature difference is 2°C or more, the generation of voids during sintering can be further suppressed.

[0056] The boiling point Tc of the organic solvent (c) is preferably higher than the boiling point Ta of the organic solvent (a), i.e., Tc > Ta. The temperature difference between Tc and Ta [Tc - Ta] is preferably 30°C or more, more preferably 50°C or more, and even more preferably 60°C or more. When the temperature difference is 30°C or more, the generation of voids during sintering can be further suppressed.

[0057] The SP value δa of organic solvent (a), the SP value δb of organic solvent (b), and the SP value δc of organic solvent (c) satisfy the relationship of the above formula (6) [δc≦δb≦δa]. In particular, it is preferable that δb is higher than δc, i.e., δc<δb is satisfied. It is also preferable that δa is higher than δb, i.e., δb<δa is satisfied.

[0058] The difference between δb and δc [δb - δc] is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.5 or more. When the difference is 0.1 or more, the dispersibility of the metal particles is superior and the continuous ejection stability is superior. The difference is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. When the difference is 2.0 or less, the alloy powder and silver powder are less likely to separate from the organic solvent, and the continuous ejection stability and storage stability are superior.

[0059] The difference between δa and δb [δa - δb] is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.5 or more. When the difference is 0.1 or more, the dispersibility of the metal particles is superior and the continuous ejection stability is superior. The difference is preferably 2.5 or less, more preferably 2.0 or less, and even more preferably 1.8 or less. When the difference is 2.5 or less, the alloy powder and silver powder are less likely to separate from the organic solvent, and the continuous ejection stability and storage stability are superior.

[0060] The difference between δa and δc [δa - δc] is 1.0 or more, preferably 1.5 or more, and more preferably 2.0 or more, based on formulas (4) and (5). When the difference is 1.0 or more, the generation of voids during sintering can be further suppressed. The difference is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. When the difference is 5.0 or less, the alloy powder and silver powder are less likely to separate from the organic solvent, resulting in better continuous discharge stability and storage stability.

[0061] The ratio of organic solvent (a) to the total amount of organic solvents (a), (b), and (c) (100% by mass) [organic solvent (a) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}] is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and even more preferably 15 to 50% by mass. When this ratio is within this range, the organic solvent is easily volatilized during sintering, making it possible to easily form a sintered body, and also resulting in better dispersibility of the alloy powder and silver powder.

[0062] The ratio of organic solvent (b) to the total amount of organic solvent (a), organic solvent (b), and organic solvent (c) (100% by mass) [organic solvent (b) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}] is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and even more preferably 15 to 50% by mass. When the ratio is within the above range, the compatibility of the organic solvents is excellent, and the continuous ejection stability and storage stability are further improved.

[0063] The proportion of organic solvent (c) relative to the total mass of organic solvents (a), (b), and (c) (100 mass%) [organic solvent (c) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}] is preferably 5 to 70 mass%, more preferably 10 to 60 mass%, and even more preferably 15 to 50 mass%. When this proportion is within the above range, the generation of voids during sintering can be further suppressed.

[0064] The content of organic solvent (c) relative to 100 parts by mass of organic solvent (a) is preferably 20 to 400 parts by mass, more preferably 30 to 300 parts by mass, and even more preferably 50 to 200 parts by mass. When the content is within the above range, the blending amounts of organic solvent (a) and organic solvent (c) are well balanced, resulting in better void suppression during sintering and better dispersibility of the alloy powder and silver powder.

[0065] The content of organic solvent (b) relative to 100 parts by mass of the total amount of organic solvent (a) and organic solvent (c) is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, and even more preferably 40 to 100 parts by mass. When the content is within the above range, the compatibility between organic solvent (a) and organic solvent (c) is further improved, and the continuous ejection stability and low-temperature storage property are further improved.

[0066] The organic solvent may contain other solvents (organic solvents) in addition to organic solvents (a), (b), and (c). The total content of organic solvents (a), (b), and (c) in the organic solvent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, relative to 100% by mass of the total amount of the organic solvents. When the content is 50% by mass or more, the dispersibility of metal particles and the compatibility of each organic solvent are excellent, and continuous discharge stability, storage stability, and void formation suppression during sintering are excellent.

[0067] When the organic solvents (a), (b), and (c) are mixed in the blending ratio used for the above-mentioned bondable conductor paste, it is preferable that the organic solvents (a), (b), and (c) dissolve uniformly at room temperature and do not undergo phase separation. Furthermore, it is preferable that the organic solvents (a), (b), and (c) dissolve uniformly at room temperature and do not undergo phase separation in the above-mentioned bondable conductor paste. It is particularly preferable that no phase separation occurs at 22 to 28°C (preferably 10 to 30°C, more preferably 0 to 35°C).

[0068] Specific examples of the binder resin include vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, polyester resin, acrylic resin, and cellulose resin (eg, ethyl cellulose).

[0069] Examples of the additives include surface conditioners, viscosity adjusters, dispersants, and antifoaming agents.

[0070] In the alloy powder-containing composition, the content of the organic substance is preferably 0.5 to 50 parts by mass, more preferably 0.7 to 30 parts by mass, and even more preferably 8 to 12 parts by mass, per 100 parts by mass of the alloy powder and metal particles other than the alloy powder combined.

[0071] The alloy powder-containing composition contains, in addition to the alloy powder, silver (Ag) powder as metal particles other than the alloy powder, because the silver (Ag) powder can be firmly bonded to the silver (Ag) contained in the AgSi eutectic structure in the alloy powder. As the metal particles other than the alloy powder, only one type of silver (Ag) powder may be used, or two or more types may be used in combination.

[0072] The silver (Ag) powder preferably has a volume average particle size (median diameter) of 0.1 to 100 μm, more preferably 0.3 to 50 μm, and even more preferably 0.5 to 10 μm. A volume average particle size of 0.1 μm or more makes it easy to handle the metal particles. A volume average particle size of 100 μm or less makes it easy to demonstrate bonding reliability.

[0073] The shape of the silver (Ag) powder is not particularly limited, but examples thereof include spherical, flake (flat), polyhedral, etc. Metal particles of the same shape may be used alone, or metal particles of different shapes may be used in combination. Among these, spherical shapes are preferred for proper dispersion in the alloy powder-containing composition.

[0074] The content of the silver (Ag) powder is preferably 5 to 2000 parts by mass, more preferably 10 to 1000 parts by mass, even more preferably 20 to 500 parts by mass, and particularly preferably 40 to 400 parts by mass, relative to 100 parts by mass of the alloy powder. When the content of the silver (Ag) powder is 5 parts by mass or more, sufficient bonding with the alloy powder can be achieved during sinter bonding, and when the content is 2000 parts by mass or less, it is easy to reduce the linear expansion coefficient.

[0075] Furthermore, the silver content relative to the total amount (100% by mass) of the alloy powder and the silver (Ag) powder is preferably 20 to 99.9% by mass, more preferably 25 to 99% by mass, and even more preferably 30 to 90% by mass. Having a silver (Ag) content of 20% by mass or more facilitates the achievement of bonding reliability. Having a silver (Ag) content of 99.9% by mass or less sufficiently reduces the linear expansion coefficient, enabling the achievement of bonding reliability while keeping manufacturing costs low.

[0076] The alloy powder-containing composition may also contain other components in addition to the components described above. Examples of the other components include surfactants other than the organic substances and viscosity modifiers other than the organic substances. The content of the other components is preferably 5% by mass or less, and may be 3% by mass or less, based on the total amount of the organic substances.

[0077] [Semiconductor Device] One embodiment of the present disclosure includes a semiconductor device in which the alloy powder-containing composition (preferably the alloy paste) is used as a bonding layer for bonding a substrate and an object to be bonded. In the semiconductor device, the object to be bonded is bonded to the substrate via a bonding layer that is a sintered body of the alloy powder-containing composition. Figure 3 is a cross-sectional view schematically showing this semiconductor device. 1 denotes the semiconductor device, 10 denotes the substrate, 20 denotes the bonding layer, and 30 denotes the object to be bonded.

[0078] Examples of the substrate include metal substrates such as copper substrates, ceramic substrates, metal-clad ceramic substrates, SiC substrates, gallium nitride substrates, glass epoxy substrates, BT resin substrates, glass substrates, and resin substrates. Since the alloy paste according to one embodiment of the present disclosure can be sintered at low temperatures, substrates that are sensitive to heat can also be used. As the substrate, ceramic substrates and metal-clad ceramic substrates are preferred, and copper-clad ceramic substrates and aluminum-clad ceramic substrates are more preferred.

[0079] Examples of the bonded object include electronic components and heat dissipation substrates. Examples of electronic components include semiconductor elements, LED elements, and other electronic elements (chips, dies), and examples of the semiconductor elements include power semiconductor elements. In addition, it is preferable that the bonding surface of the bonded object with the bonding layer is silver-plated. Examples of the material of the bonded object include Si (silicon), SiC (silicon carbide), GaN, diamond, and the like.

[0080] The semiconductor device can be manufactured by applying the alloy powder-containing composition to a substrate by a printing method (specifically, a dispenser printing method, a mask printing method, a screen printing method, an inkjet printing method, etc.), mounting an object to be bonded on the applied layer, and then sintering the resulting layer.

[0081] The sintering temperature is preferably, for example, 150° C. to 300° C., more preferably 160° C. to 280° C., even more preferably 200° C. to 270° C., and particularly preferably 230° C. to 260° C. The sintering time is preferably, for example, 6 minutes to 2 hours, and more preferably 10 minutes to 1 hour.

[0082] The thickness of the bonding layer formed by the above method is preferably 3 μm to 500 μm, more preferably 10 to 300 μm, and even more preferably 40 to 150 μm.

[0083] The sintering process recrystallizes and exudes the silver (Ag) present in the AgSi eutectic structure of the alloy powder in the alloy powder-containing composition, thereby firmly bonding the silver (Ag) to the substrate and the bonded object. Furthermore, because the bonding layer contains the alloy powder with a low linear expansion coefficient, the strength of the bond can be increased while maintaining a low thermal expansion coefficient. This essentially improves the properties of the bonding layer, such as thermal fatigue resistance. Therefore, a semiconductor device using the alloy powder-containing composition as a bonding layer for bonding a substrate and a bonded object can comply with environmental regulations, operate at high temperatures, and have excellent bonding reliability.

[0084] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, each configuration and their combination in each embodiment is merely an example, and additions, omissions, and other modifications of configurations are possible as appropriate within the scope of the gist of this disclosure. The present disclosure is not limited by the embodiments, but is limited only by the scope of the claims.

[0085] Hereinafter, one embodiment of the present disclosure will be described in more detail based on examples.

[0086] Production Example 1 (Preparation of Alloy Powder) Silver (Ag) bullion (purity 99.99%) and silicon (Si) bullion (purity 99.9999%) were mixed to a content of 80 mass % and 20 mass % by mass, and then heated to 1600°C to dissolve. The resulting solution was pulverized using a gas atomizer (product name "RQP-20K", manufactured by Makabe Giken Co., Ltd.) to obtain the alloy powder of Production Example 1. The mixture was then spheronized using an ultrasonic vibration sieve (product name "TSK-DGS type", manufactured by Tokyo Screen Co., Ltd.) to obtain particles with a volume average particle diameter of 15.86 μm.

[0087] Production Example 2 Silver (Ag) bullion (purity 99.99%) and silicon (Si) bullion (purity 99.9999%) were mixed to a content of 50% by mass and heated to 1600°C to dissolve. The resulting solution was pulverized using a gas atomizer (product name "RQP-20K", manufactured by Makabe Giken Co., Ltd.) to obtain the alloy powder of Production Example 2. The mixture was then spheronized using an ultrasonic vibration sieve (product name "TSK-DGS type", manufactured by Tokyo Screen Co., Ltd.) to obtain particles with a volume average particle diameter of 17.05 μm.

[0088] Production Example 3 Silver (Ag) bullion (purity 99.99%) and silicon (Si) bullion (purity 99.9999%) were mixed to a content of 20 mass% and 80 mass%, respectively, and heated to 1600°C to dissolve. The resulting solution was pulverized using a gas atomizer (product name "RQP-20K", manufactured by Makabe Giken Co., Ltd.) to obtain the alloy powder of Production Example 3. The mixture was then spheronized using an ultrasonic vibration sieve (product name "TSK-DGS type", manufactured by Tokyo Screen Co., Ltd.) to obtain particles with a volume average particle diameter of 16.05 μm.

[0089] Example 1 A paste-like alloy powder-containing composition of Example 1 was prepared by mixing 13.05 g of the alloy powder of Production Example 1, 16.95 g of silver (Ag) particles, and 2.72 g of an organic substance under the trade name "Cellul A IP" (manufactured by Daicel Corporation).

[0090] Example 2 13.00 g of the alloy powder of Production Example 2, 7.00 g of silver (Ag) particles, and 1.40 g of an organic substance under the trade name "Cellutol A IP" (manufactured by Daicel Corporation) were mixed to prepare a paste-like alloy powder-containing composition of Example 2. The linear expansion coefficient of the sintered body of the alloy powder-containing composition of Example 2, measured by the same method as described below, was 8.

[0091] Example 3 8.13 g of the alloy powder of Production Example 3, 11.87 g of silver (Ag) particles, and 1.40 g of an organic substance under the trade name "Cellutol A IP" (manufactured by Daicel Corporation) were mixed to prepare a paste-like alloy powder-containing composition of Example 3. The linear expansion coefficient of the sintered body of the alloy powder-containing composition of Example 3, measured by the same method as described below, was 8.

[0092] Example 4 6.00 g of the alloy powder of Production Example 2, 14.00 g of silver (Ag) particles, and 1.40 g of an organic substance (trade name "Cellutol A IP" (manufactured by Daicel Corporation)) were mixed to prepare a paste-like alloy powder-containing composition of Example 4. The linear expansion coefficient of the sintered body of the alloy powder-containing composition of Example 4, measured by the same method as described below, was 12.

[0093] Example 5 3.75 g of the alloy powder of Production Example 3, 16.25 g of silver (Ag) particles, and 0.70 g of an organic substance under the trade name "Cellutol A IP" (manufactured by Daicel Corporation) were mixed to prepare a paste-like alloy powder-containing composition of Example 5. The linear expansion coefficient of the sintered body of the alloy powder-containing composition of Example 5, measured by the same method as described below, was 12.

[0094] Comparative Example 1 Instead of the alloy powder of Example 1, 20 g of silver (Ag) particles alone were mixed with 1.73 g of an organic substance "Cellutol A IP" (manufactured by Daicel Corporation) to prepare a paste of Comparative Example 1.

[0095] Comparative Example 2 A paste of Comparative Example 2 was prepared by mixing 27.39 g of silver (Ag) particles, 2.61 g of silicon (Si) particles, and 8.29 g of an organic substance under the trade name "Cellutol A IP" (manufactured by Daicel Corporation).

[0096] [Evaluation] The physical properties of the pastes of the above Examples and Comparative Examples were evaluated, and the results are shown in Tables 1 and 2.

[0097] (1) Mountability (1)-1. Mounting Temperature The pastes of Example 1 and Comparative Examples 1 and 2 were heated for 30 minutes, and those that bonded at 300°C or less were evaluated as ○, those that bonded at 250°C or less were evaluated as ⊚, and those that did not bond at 300°C or less were evaluated as ×.

[0098] (1)-2. Mounting Time The pastes of Example 1 and Comparative Examples 1 and 2 were heated under conditions of a pressure of 20 MPa and a temperature of 250°C, and those that bonded within 60 minutes were evaluated as ○, those that bonded within 30 minutes as ◎, and those that did not bond within 60 minutes as ×.

[0099] (1)-3. Mounting Pressure The pastes of Example 1 and Comparative Examples 1 and 2 were heated under conditions of a pressure of 20 MPa, a temperature of 250°C, and for 60 minutes, and evaluation was performed with a circle indicating that all the metal particles were bonded together but voids were generated, a double circle indicating that all the metal particles were bonded together and no voids were generated, and an x ​​indicating that some metal particles were not bonded together.

[0100] (2) Bonding Reliability (2)-1. Linear Expansion Coefficient Test pieces were prepared by sintering the pastes of Example 1 and Comparative Examples 1 and 2 into button shapes. The test pieces were measured using a thermomechanical analyzer (TMA-60, manufactured by Shimadzu Corporation), and the linear expansion coefficient was evaluated as follows: ◯ for a coefficient of linear expansion of 19 or less, ⊚ for a coefficient of linear expansion of 16 or less, and × for a coefficient of linear expansion of more than 19.

[0101] (2)-2. Structural Change The pastes of Example 1 and Comparative Examples 1 and 2 were left in a thermostatic bath (trade name "DKN303", manufactured by Yamato Scientific Co., Ltd.) at 250°C for 100 hours, and the metal structure was observed. When significant coarsening of the metal structure was confirmed, the evaluation was given as "x", and when no significant coarsening was observed, the evaluation was given as "o".

[0102] (2)-3. Strength Retention Rate The pastes of Examples 2 to 5 and Comparative Example 1 were molded into 3 mm x 3 mm pieces, and then bonded to a copper substrate and SiC. The resulting semiconductor devices were sintered at a pressure of 20 MPa, a temperature of 300°C, and a test speed of 50 μm / s. The shear bond strength of the semiconductor devices was measured at room temperature using a die shear tester (product name "SERIES4000," manufactured by DAGE Corporation) at a test speed of 50 μm / s. The shear bond strength was also measured under the same conditions after a thermal shock test, in which one cycle consisted of heating and cooling the temperature from -50 to 250°C for 500 and 1,000 cycles. The shear bond strength was calculated as the shear bond strength retention rate (%) before and after the thermal shock test (shear bond strength after thermal shock test / shear bond strength before thermal shock test × 100). A strength retention rate of 60% or greater was evaluated as ⊚, a strength retention rate of 50% or greater was evaluated as ◯, and a strength retention rate of less than 50% was evaluated as ×.

[0103]

[0104]

[0105] The alloy powder-containing compositions of the examples were confirmed to have excellent mountability and high-temperature bonding reliability. On the other hand, when Ag paste was used, it was confirmed that the linear expansion coefficient was high, structural changes occurred at high temperatures, and strength retention was poor, resulting in poor bonding reliability (Comparative Example 1). Furthermore, in the case of an alloy powder-containing composition using a mixed powder of silver particles and silicon particles, the alloying of Ag and Si was incomplete compared to the Ag-Si alloy particles of Example 1, making pressure application during mounting essential and resulting in poor mountability (Comparative Example 2).

[0106] Variations of the present disclosure are described below. [Appendix 1] An alloy powder-containing composition comprising an alloy powder having an AgSi eutectic structure, silver (Ag) powder, and an organic substance. [Appendix 2] The alloy powder-containing composition according to Appendices 1 or 2, which has a sinterable temperature of 150 to 300°C. [Appendix 3] The alloy powder-containing composition according to Appendices 1 or 2, which has a strength retention rate (%) of 50% or more, calculated as the ratio of the shear bond strength measured under the same conditions after a thermal shock test in which the semiconductor device is repeatedly heated and cooled in the temperature range of -50 to 250°C a specified number of times to the shear bond strength measured using a die shear tester at room temperature and a test speed of 50 μm / s (shear bond strength after thermal shock test / shear bond strength before thermal shock test × 100). [Appendix 4] The alloy powder-containing composition according to any one of Appendices 1 to 3, which has a linear expansion coefficient of 17 or less, measured using a thermomechanical analyzer. [Appendix 5] The alloy powder-containing composition according to any one of Appendices 1 to 4, wherein the metal structure is observed after standing at 250°C for 100 hours and no significant coarsening occurs in the metal structure. [Appendix 6] The alloy powder-containing composition according to any one of Appendices 1 to 5, wherein a single particle is selected from an image taken at a magnification of 2,000 to 50,000 times, and the total perimeter and the length of the outer perimeter where the eutectic structure is present, excluding a region where the eutectic structure is completely absent in a region extending from the perimeter to a depth of 0.2 μm toward the center of the particle, are measured, and the ratio of the total perimeter to the total perimeter is calculated as the ratio of the AgSi structure on the particle surface. This method is performed on any 10 adjacent particles, and the ratio of the AgSi eutectic structure on the particle surface is 10% or more in at least 8 of the particles. [Appendix 7] The alloy powder-containing composition according to any one of Appendices 1 to 6, wherein the silver (Ag) content relative to the total amount of the alloy powder is 15 to 97.6 mass%. [Appendix 8] The alloy powder-containing composition according to any one of Appendices 1 to 7, wherein the silicon (Si) content relative to the total amount of the alloy powder is 2.4 to 85 mass%. [Appendix 9] The alloy powder-containing composition according to any one of Appendices 1 to 8, wherein the alloy powder is spherical. [Appendix 10] The alloy powder-containing composition according to any one of Appendices 1 to 9, wherein the silver (Ag) powder content is 5 to 2000 parts by mass relative to 100 parts by mass of the alloy powder.[Appendix 11] The alloy powder-containing composition according to any one of Appendices 1 to 10, wherein a silver content relative to the total amount of the alloy powder and the silver (Ag) powder is 20 to 99.9 mass%. [Appendix 12] The alloy powder-containing composition according to any one of Appendices 1 to 11, wherein the alloy powder has a volume average particle diameter (median diameter) of 0.1 to 100 μm. [Appendix 13] The alloy powder-containing composition according to any one of Appendices 1 to 12, wherein the silver (Ag) powder has a volume average particle diameter (median diameter) of 0.1 to 100 μm. [Appendix 14] The alloy powder-containing composition according to any one of Appendices 1 to 13, wherein the silver (Ag) powder is spherical. [Appendix 15] The alloy powder-containing composition according to any one of Appendices 1 to 14, wherein the organic substance is an organic solvent. [Appendix 16] A semiconductor device using the alloy powder-containing composition according to any one of Appendices 1 to 15 as a bonding layer for bonding a substrate and an object to be bonded.

[0107] 1 Semiconductor device 10 Substrate 20 Bonding layer 30 Object to be bonded

Claims

1. An alloy powder-containing composition including an alloy powder having an AgSi eutectic structure, silver (Ag) powder, and an organic substance.

2. The alloy powder-containing composition according to claim 1, wherein the content of silver (Ag) relative to the total amount of the alloy powder is 15 to 97.6 mass %.

3. The alloy powder-containing composition according to claim 1 or 2, wherein the content of the silver (Ag) powder is 5 to 2000 parts by mass with respect to 100 parts by mass of the alloy powder.

4. The alloy powder-containing composition according to claim 1 or 2, wherein the silver content relative to the total amount of the alloy powder and the silver (Ag) powder is 20 to 99.9 mass %.

5. The alloy powder-containing composition according to claim 1 or 2, wherein the alloy powder has a volume average particle size (median size) of 0.1 to 100 μm.

6. A semiconductor device using the alloy powder-containing composition according to claim 1 or 2 as a bonding layer for bonding a substrate and an object to be bonded.

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