Metal paste, method for manufacturing substrate having conductive vias, and substrate havig conductive vias

Abstract

Provided is a metal paste containing metal particles and a volatile solvent. The metal particles include silver particles and copper particles. The silver particles include flat silver particles X having a volume average particle diameter of 0.8 μm or more. The copper particles include copper particles Y having a volume average particle diameter of 0.5 μm or less. Also provided is a method for manufacturing a substrate having conductive vias that comprises: a step for preparing a substrate provided with holes, and filling at least the inside of the holes with the abovementioned metal paste; and a step for firing the metal paste or the metal paste from which a portion of the volatile solvent has been removed.　The method for manufacturing a substrate having conductive vias using the metal paste is also useful as a technique for reducing the environmental impact of plating.

Description

Method for manufacturing metal paste, conductive via-equipped substrate, and conductive via-equipped substrate

[0001] This invention relates to a metal paste, a method for manufacturing a conductive via-equipped substrate, and a conductive via-equipped substrate.

[0002] In recent years, three-dimensional packaging technology has attracted attention as a means of miniaturizing, enhancing the functionality, and integrating electronic devices and components. This technology involves electrically connecting silicon substrates arranged vertically and horizontally via electrodes called through-silicon vias (TSVs) to create high-density stacking of semiconductor chips in the vertical direction (height direction).

[0003] As a method for forming through-electrodes, for example, Patent Document 1 discloses a method for manufacturing a semiconductor device having silicon through-electrodes, which includes a step of copper plating non-through vias formed on a silicon substrate by electroplating using a specific copper plating solution. However, such a method has challenges in terms of productivity due to the environmental burden caused by the plating and the long working time required to suppress the deposition rate of the copper film.

[0004] Another known method involves filling through-holes in a heat-resistant substrate with a copper conductive paste containing copper powder, glass powder, an organic vehicle, etc., and firing it to form copper conductors within the through-holes (for example, see Patent Document 2 below).

[0005] Japanese Patent Publication No. 2019-16712 Japanese Patent Publication No. 2010-108917

[0006] A method of forming conductors using a metal paste containing metal particles and a volatile solvent is useful from the standpoint of reducing environmental impact and improving productivity.

[0007] In recent years, with the miniaturization of substrates to accommodate the miniaturization of electronic devices and components, the inner diameter of through-holes has also become extremely small, making it necessary to form conductive vias that have sufficient conductivity even within such through-holes.

[0008] Recently, there has been a growing demand for faster signals, smaller substrates, and lower power consumption through shorter transmission distances, requiring even greater improvements in connection reliability than before. For these reasons, conductive via substrates are required to have not only excellent conductivity but also excellent characteristics such as minimal increase in connection resistance even when subjected to temperature changes (hereinafter also referred to as "connection reliability").

[0009] Furthermore, the substrates used to form conductive vias are diverse, including silicon substrates, glass substrates, and organic substrates, and depending on the material and via shape, it may be difficult to obtain excellent connection reliability.

[0010] Therefore, the present invention aims to provide a metal paste capable of forming conductive vias with excellent connection reliability, a method for manufacturing a conductive via-equipped substrate using the same, and a conductive via-equipped substrate.

[0011] One aspect of the present invention relates to the following metal paste: [1] A metal paste containing metal particles and a volatile solvent, wherein the metal particles contain silver particles and copper particles, the silver particles include flattened silver particles X with a volume average particle size of 0.8 μm or more, and the copper particles include copper particles Y with a volume average particle size of 0.5 μm or less. [2] The metal paste according to [1], wherein the content of the silver particles X is 5 to 40% by mass based on the total amount of metal particles. [3] The metal paste according to [1] or [2], wherein the content of the copper particles Y is 50% by mass or less based on the total amount of metal particles. [4] The specific surface area of ​​the copper particles Y is 3.3 m². ２ A metal paste according to any one of [1] to [3], which is less than or equal to / g.

[0012] Another aspect of the present invention relates to the following metal pastes: [5] A metal paste containing metal particles and a volatile solvent, wherein the metal particles include metal particles A made of a metal with a Young's modulus of 5 to 99 GPa and metal particles B made of a metal with a Young's modulus of 100 to 250 GPa, wherein metal particles A includes flattened metal particles X with a volume average particle size of 0.8 μm or more, and metal particles B include metal particles Y with a volume average particle size of 0.5 μm or less. [6] The metal paste according to [5], wherein the content of metal particles X is 5 to 40% by mass based on the total amount of metal particles. [7] The metal paste according to [5] or [6], wherein the content of metal particles Y is 50% by mass or less based on the total amount of metal particles. [8] The specific surface area of ​​metal particles Y is 3.3 m². ２ A metal paste according to any one of [5] to [7], wherein the amount is less than or equal to / g.

[0013] Another aspect of the present invention relates to the following method for manufacturing a conductive via substrate: [9] A method for manufacturing a conductive via substrate, comprising the steps of: preparing a substrate having holes, filling at least the inside of the holes with a metal paste according to any one of [1] to [8]; and firing the metal paste, or the metal paste from which a portion of the volatile solvent has been removed.

[0014] Another aspect of the present invention relates to the following conductive via substrate:

[10] A conductive via substrate comprising a substrate having through holes and conductive vias provided in the through holes, wherein the conductive vias include a sintered body of a metal paste as described in any of [1] to [8].

[0015] According to the present invention, a metal paste capable of forming conductive vias with excellent connection reliability, a method for manufacturing a conductive via-equipped substrate using the same, and a conductive via-equipped substrate can be provided.

[0016] This is a schematic diagram showing an example of a method for manufacturing a conductive via-equipped substrate according to this embodiment. This is a schematic diagram showing an example of a method for manufacturing a conductive via-equipped substrate according to this embodiment. This is a schematic diagram showing an example of a method for forming wiring. This is a schematic diagram showing a test piece.

[0017] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the following embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0018] <Metal Paste> A metal paste according to one embodiment of the present invention contains metal particles and a volatile solvent, wherein the metal particles contain silver particles and copper particles, the silver particles include flattened silver particles X with a volume average particle size of 0.8 μm or more, and the copper particles include copper particles Y with a volume average particle size of 0.5 μm or less.

[0019] The above-described metal paste makes it possible to form conductive vias with excellent connection reliability. The inventors speculate that the reason for this effect is as follows: When a substrate on which conductive vias are formed is repeatedly subjected to temperature changes, cracks tend to occur in the conductive vias due to the difference in thermal expansion between the substrate material and the conductive via material, causing the connection resistance to increase. This tendency is thought to be particularly strong when conductive vias with a large aspect ratio of [via depth / via diameter] or a large via diameter are formed on a substrate with a lower average linear thermal expansion coefficient than the conductive via material (e.g., glass substrates and silicon substrates), or when conductive vias with a large via diameter or via depth are formed on a substrate with a higher average linear thermal expansion coefficient than the conductive via material (e.g., organic substrates). In contrast, the sintered body formed from the metal paste of this embodiment containing the above-described specific silver particles X and copper particles Y has a lower sintering density and a lower Young's modulus compared to a sintered body formed from copper particles alone. This is thought to mitigate the occurrence of cracks in the conductive vias due to the difference in thermal expansion between the substrate material and the conductive via material, thereby suppressing the increase in connection resistance.

[0020] [Metal Particles] Examples of the metal particles include particles of nickel, silver, copper, gold, palladium, platinum, solder and the like. The metal particles may contain a plurality of metals such as silver-coated copper particles. When the metal paste contains copper particles, it is easy to obtain a conductor that has sufficient conductivity and hardly increases in resistance value even when subjected to temperature changes, and a substrate having through electrodes that have sufficient conductivity and excellent connection reliability.

[0021] The content of the metal particles in the metal paste of the present embodiment may be 95.0 mass% or more, 95.2 mass% or more, 95.5 mass% or more, 95.7 mass% or more, 96 mass% or more, or 96.2 mass% or more, and may be 98 mass% or less, 97 mass% or less, or 96.5 mass% or less, based on the total amount of the metal paste, and may be 95.0 to 98 mass%, 95.2 to 97 mass%, 95.7 to 96.5 mass%, or 96.2 to 96.4 mass%.

[0022] In the present specification, the volume average particle diameter of particles (hereinafter sometimes referred to as "average particle diameter") means a 50% volume average particle diameter (D50). When determining the volume average particle diameter of the metal particles, it can be determined by a method of measuring a dispersion of the raw material metal particles in a dispersion medium such as water or alcohol with a laser diffraction / scattering particle size distribution analyzer, or the like.

[0023] (Silver Particle X) The average particle size of Silver Particle X may be 0.8 μm or more, 1.0 μm or more, 2.0 μm or more, or 3.0 μm or more from the viewpoint of reducing the sintered density and longitudinal elastic modulus of the sintered body to suppress the occurrence of cracks in the conductive via due to the difference in thermal expansion between the material of the substrate and the material of the conductive via when repeated temperature changes are applied to the substrate on which the conductive via is formed; the average particle size may be 10 μm or less, 8.0 μm or less, 5.0 μm or less, or 4.0 μm or less from the viewpoint of improving the filling property and the flatness (or smoothness) of the metal paste filled in the pores; and the average particle size may be 0.8 μm to 10 μm, 1.0 μm to 8.0 μm, or 2.0 μm to 6.0 μm from the viewpoint of reducing the connection resistance value and improving the connection reliability. The ratio (DC1 / DH) of the average particle size DC1 of Silver Particle X to the inner diameter DH of the pore may be 0.01 or more, may be 0.03 or more, or may be 0.04 or more from the viewpoint of suppressing particle clogging in micro vias and improving filling property; and the ratio may be 0.15 or less, may be 0.1 or less, or may be 0.05 or less from the viewpoint of suppressing voids and cracks by reducing shrinkage due to firing. Further, from the above viewpoint, the ratio (DC1 / DH) may be 0.01 to 0.15, or 0.03 to 0.1.

[0024] The aspect ratio of Silver Particle X may be 1.5 or more, 2.0 or more, or 3.0 or more from the viewpoint of suppressing the occurrence of cracks in the conductive via due to the difference in thermal expansion between the material of the substrate and the material of the conductive via when repeated temperature changes are applied to the substrate on which the conductive via is formed; and the aspect ratio may be 1.5 to 12.0, 2.0 to 10.0, or 3.0 to 8.0 from the viewpoint of achieving both securing the filling property into the conductive via by reducing the viscosity of the metal paste and improving the connection reliability.

[0025] In the present specification, the aspect ratio (major axis / minor axis) of a particle can be determined, for example, by observing an SEM image of the particle and measuring the major axis and the minor axis (e.g., thickness).

[0026] Commercially available silver particles X can be used. Examples of commercially available silver particles X include AgC-271B (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., product name, average particle size (D50): 2.1 μm, flattened, aspect ratio: 6.0), AgC-221PA (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., product name, average particle size (D50): 7.5 μm, flattened, aspect ratio: 10.0), LM-1 (manufactured by Tokusen Industry Co., Ltd., product name, average particle size (D50): 0.92 μm, flattened, aspect ratio: 10.0), and M-13 (manufactured by Tokusen Industry Co., Ltd., product name, average particle size (D50): 1.82 μm, flattened, aspect ratio: 12.0).

[0027] The silver particles X may be treated with a surface treatment agent from the viewpoint of dispersion stability and oxidation resistance. The surface treatment agent may be removed during the sintering of the metal paste. Examples of such surface treatment agents include aliphatic carboxylic acids such as palmitic acid, stearic acid, arachidic acid, and oleic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, and o-phenoxybenzoic acid; aliphatic alcohols such as cetyl alcohol, stearyl alcohol, isobornylcyclohexanol, and tetraethylene glycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine, and stearylamine; aliphatic nitriles such as stearonitrile and decanonitrile; silane coupling agents such as alkylalkoxysilanes; and polymeric treatment agents such as polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, and silicone oligomers. One type of surface treatment agent may be used alone, or two or more types may be used in combination.

[0028] The amount of surface treatment agent applied may be one molecular layer or more on the particle surface.

[0029] The content of silver particles X in the metal paste may be 5 to 40% by mass based on the total amount of metal particles, from the viewpoint of connection reliability, and may be 5 to 30% by mass or 5 to 20% by mass, from the viewpoint of suppressing migration.

[0030] (Copper Particle Y) The average particle diameter of Copper Particle Y may be 0.5 μm or less, or 0.4 μm or less from the viewpoint of sinterability, and may be 210 nm or more, 240 nm or more, 290 nm or more, or 340 nm or more from the viewpoints of filling property, suppression of synthesis cost, favorable dispersibility, and suppression of the usage amount of the surface treatment agent, and may be 210 nm to 0.5 μm, 210 nm to 0.4 μm, 240 nm to 0.4 μm, 290 nm to 0.4 μm, or 340 nm to 0.4 μm from the viewpoint of obtaining low-temperature sinterability and favorable filling property in a paste.

[0031] The specific surface area of Copper Particle Y may be 3.3 m ２ / g or less, 2.6 m ２ / g or less, 2.2 m ２ / g or less, or 2.0 m ２ / g or less from the viewpoint of filling property, and may be 1.6 m ２ / g or more, 1.8 m ２ / g or more, or 2.0 m ２ / g or more from the viewpoint of sinterability. In addition, the specific surface area of the second metal particles may be 1.8 to 3.3 m ２ / g, 1.8 to 2.6 m ２ / g, 2.0 to 2.5 m ２ / g, or 2.1 to 2.4 m ２ / g from the viewpoints of sinterability and filling property.

[0032] The specific surface area of Copper Particle Y can be measured, for example, by a nitrogen adsorption method (BET single-point method) using "BELSO RP-MR6" manufactured by MicrotracBEL Corp.

[0033] Copper Particle Y can act as copper particles that suitably bond between Silver Particles X.

[0034] Copper Particle Y may be a wet-process copper powder produced by a chemical reduction method.

[0035] The shape of the copper particles Y may be, for example, spherical, lumpy, needle-shaped, flattened (flake-shaped), or approximately spherical. The second copper particles may be aggregates of copper particles having these shapes. From the viewpoint of dispersibility and packing, the shape of the copper particles Y may be spherical, approximately spherical, or flattened (flake-shaped), and from the viewpoint of flammability and miscibility with the first copper particles, it may be spherical or approximately spherical.

[0036] The aspect ratio of the copper particles Y may be 5 or less, 4 or less, or 3 or less, from the viewpoint of dispersibility, packing ability, and miscibility with silver particles X.

[0037] Copper particles Y can be synthesized or commercially available. Examples of commercially available copper particles Y include CH0200L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., trade name, average particle size (D50): 200 nm, spherical) and Tn-Cu100 (manufactured by Taiyo Nippon Sanso Corporation, average particle size (D50): 120 nm, spherical).

[0038] Copper particles Y may be treated with a specific surface treatment agent. Examples of specific surface treatment agents include organic acids having 8 to 16 carbon atoms. Examples of organic acids having 8 to 16 carbon atoms include caprylic acid, methylheptanoic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid, ethyloctanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanoic acid, lauric acid, methylundecanoic acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, Saturated fatty acids such as pentylheptanoic acid, tridecanoic acid, methyldodecanoic acid, ethylundecanoic acid, propyldecanoic acid, butylnonanoic acid, pentyloctanoic acid, myristic acid, methyltridecanoic acid, ethyldodecanoic acid, propylundecanoic acid, butyldecanoic acid, pentylnonanoic acid, hexyloctanoic acid, pentadecanoic acid, methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecanoic acid, heptylnonanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, nonylcyclohexanecarboxylic acid, etc. Examples include acids, unsaturated fatty acids such as nonenic acid, methylnonenic acid, 10-hydroxy-2-decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, and sapienic acid; and aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, o-phenoxybenzoic acid, methylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, pentylbenzoic acid, hexylbenzoic acid, heptylbenzoic acid, octylbenzoic acid, and nonylbenzoic acid. Organic acids may be used individually or in combination of two or more.By combining such organic acids with the copper particles Y described above, it tends to be possible to achieve both good dispersibility of the copper particles Y and good desorption of the organic acid during sintering.

[0039] The amount of surface treatment agent applied may be an amount that adheres to the surface of copper particles Y in one to three molecular layers. The amount of surface treatment agent applied may be 0.07% by mass or more, 0.10% by mass or more, or 0.2% by mass or more, and may be 2.1% by mass or less, 1.6% by mass or less, or 1.1% by mass or less.

[0040] The amount of surface treatment for copper particles Y is determined by the number of molecular layers (n) attached to the surface of copper particles Y and the specific surface area (A) of copper particles Y. ｐ ) (Unit: m) ２ ( / g) and the molecular weight (M) of the surface treatment agent. ｓ ) (unit g / mol) and the minimum coverage area (S) of the surface treatment agent. Ｓ ) (Unit: m) ２ ( / item) and Avogadro's number (N) Ａ ) (6.02 x 10 ２３ It can be calculated from the number of units. Specifically, the amount of surface treatment agent processed is: Amount of surface treatment agent processed (mass%) = {(n × A ｐ ×M ｓ ) / (S Ｓ ×N Ａ +n × A ｐ ×M ｓ It is calculated according to the formula )} × 100%.

[0041] The specific surface area of ​​copper particles Y can be calculated by measuring the specific surface area of ​​dried copper particles using the BET specific surface area measurement method. The minimum coating area of ​​the surface treatment agent is 2.05 × 10⁻⁶ when the surface treatment agent is a linear saturated fatty acid. －１９ I understand ２This is 1 molecule. For other surface treatment agents, the amount can be measured, for example, by calculation from a molecular model or by the method described in "Chemistry and Education" (Katsuhiro Ueeda, Sumio Inafuku, Iwao Mori, 40(2), 1992, pp. 114-117). An example of a quantitative method for surface treatment agents is shown. Surface treatment agents can be identified by thermal desorption gas / gas chromatography-mass spectrometry of the dried powder obtained by removing the dispersion medium from the metal paste, thereby determining the number of carbon atoms and molecular weight of the surface treatment agent. The carbon content of the surface treatment agent can be analyzed by carbon content analysis. An example of a carbon content analysis method is high-frequency induction heating furnace combustion / infrared absorption spectroscopy. The amount of surface treatment agent can be calculated from the identified number of carbon atoms, molecular weight, and carbon content using the above formula.

[0042] The copper particle Y content in the metal paste may be 50% by mass or less, or 10% by mass or more and 50% by mass or less, based on the total amount of metal particles, from the viewpoint of connection reliability. From the viewpoint of lowering the sintering temperature to improve adhesion with the underlying metal layer, reducing the porosity of the sintered body, suppressing shrinkage during sintering, and suppressing crack occurrence, it may be 15 to 45% by mass or 20 to 40% by mass.

[0043] The metal paste of this embodiment may further contain copper particles Z having a volume-average particle size of 0.8 μm or more, in addition to the copper particles Y.

[0044] (Copper particles Z) The average particle size of copper particles Z may be 0.8 μm or more, 1.0 μm or more, 2.0 μm or more, or 3.0 μm or more, from the viewpoint of improving the sintering density in the holes of the substrate (e.g., through holes or non-through holes) and suppressing voids and cracks that occur in the holes. For example, from the viewpoint of suppressing particle clogging in minute vias with an inner diameter of 100 μm or less and improving packing performance, it may be 10 μm or less, 8.0 μm or less, 5.0 μm or less, or 4.0 μm or less. From the viewpoint of suppressing voids and cracks and suppressing particle clogging in minute vias, it may be 0.8 μm to 4.0 μm, 1.0 μm to 3.5 μm, or 1.2 μm to 3.0 μm. The ratio (DC1 / DH) of the average particle size DC1 of copper particles Z to the inner diameter DH of the pores may be 0.01 or greater, 0.03 or greater, or 0.04 or greater, from the viewpoint of suppressing particle clogging in minute vias and improving packing performance. From the viewpoint of suppressing voids and cracks by reducing shrinkage due to firing, the ratio may be 0.15 or less, 0.1 or less, or 0.05 or less. Furthermore, from the above viewpoint, the ratio (DC1 / DH) may be 0.01 to 0.15, or 0.03 to 0.1.

[0045] The shape of the copper particles Z may be, for example, spherical, lumpy, needle-shaped, flattened (flake-shaped), or substantially spherical. The first metal particles may be aggregates of copper particles having these shapes. The metal paste of this embodiment may include spherical copper particles as copper particles Z, from the viewpoint of suppressing fluctuations in connection resistance even after reliability tests (e.g., temperature cycling tests).

[0046] From the viewpoint of improving the printability of the metal paste, the copper particles Z may contain 40% by mass or more, 50% by mass or more, 60% by mass or more, 80% by mass or more, or 100% by mass, and may also contain 40-90% by mass, 50-80% by mass, or 60-70% by mass.

[0047] Furthermore, the metal paste of this embodiment may contain flake-shaped copper particles as copper particles Z, from the viewpoint of suppressing voids and cracks by reducing shrinkage due to firing. It may also contain spherical copper particles and flake-shaped copper particles, from the viewpoint of lowering the viscosity of the metal paste, improving its ability to fill minute vias, and suppressing voids and cracks by reducing shrinkage due to firing. When spherical copper particles and flake-shaped copper particles are used in combination, their mass ratio (spherical copper particles) / (flake-shaped copper particles) may be 1 to 9, 1.2 to 2.5, or 1.4 to 4.

[0048] The flake-shaped copper particles may have an aspect ratio of 1.5 or more, 2 or more, or 3 or more.

[0049] When spherical copper particles with an aspect ratio of 2 or less and flake-shaped copper particles with an aspect ratio greater than 2 are used in combination, their mass ratio (spherical copper particles) / (flake-shaped copper particles) may be 0.6 to 9, 1.0 to 4.0, or 1.5 to 2.4.

[0050] The copper particles Z may be produced by chemical reduction, atomization, electrolysis, pulverization, plasma rotation electrode method, uniform droplet spraying method, heat treatment method, etc., and may be wet copper powder or atomized copper powder from the viewpoint of easily obtaining a uniform diameter and improving the dispersibility of the metal paste.

[0051] The copper particles Z may contain wet copper powder. In this case, conductive vias with excellent conductivity are more easily obtained. This effect is thought to be due to the property of wet copper powder to readily bond with copper particles Y. The wet copper powder may have a D90 / D50 ratio of 1.5 or less.

[0052] Furthermore, the copper particles Z can contain both wet copper powder and atomized copper powder. In this case, it becomes easier to improve the printability of the metal paste and to suppress fluctuations in connection resistance even after reliability tests (e.g., temperature cycling tests). The following is presumed to be the reason for these effects: The coexistence of wet copper powder, which readily bonds with copper particles Y and has a uniform particle size, and atomized copper powder, which has a wide particle size distribution, allows the wet copper powder to bond with the copper particles Y while also bonding with the atomized copper powder particles. This results in the formation of a strong sintered body with a close-packed structure, and suppression of voids, cracks, and depressions due to suppressed shrinkage during sintering. The atomized copper powder may have a D90 / D50 of 1.6 or higher, 1.7 or higher, or 1.8 or higher.

[0053] When copper particles Z contain wet copper powder and atomized copper powder, the proportion of wet copper powder may be more than 0 parts by mass and less than 100 parts by mass, or 20 to 80 parts by mass, based on 100 parts by mass of the total amount of wet copper powder and atomized copper powder.

[0054] As copper particles Z, commercially available ones can be used. Examples of commercially available first copper particles include 1050Y (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): 0.81 μm, D90: 1.1 μm, spherical, wet copper powder), 1100Y (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): 1.1 μm, D90: 1.6 μm, spherical, wet copper powder), 1200Y (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): 2.1 μm, D90: 3.1 μm, spherical, wet copper powder), 1300Y (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): 3.5 μm, D90: 5 μm, spherical, wet copper powder), 1100YP (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): Examples include 1.4 μm, D90: 2.3 μm, flattened, wet copper powder), 1200YP (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): 3.1 μm, D90: 5.3 μm, flattened, wet copper powder), MA-C02K (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): 1.8 μm, D90: 3.6 μm, spherical, atomized copper powder), MA-C025K (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): 2.4 μm, D90: 5.2 μm, spherical, atomized copper powder), and MA-C03K (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, average particle size (D50): 3.4 μm, D90: 6.3 μm, spherical, atomized copper powder).

[0055] The copper particles Z may be treated with a surface treatment agent from the viewpoint of dispersion stability and oxidation resistance. The surface treatment agent may be removed during the sintering of the metal paste. Examples of such surface treatment agents include aliphatic carboxylic acids such as palmitic acid, stearic acid, arachidic acid, and oleic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, and o-phenoxybenzoic acid; aliphatic alcohols such as cetyl alcohol, stearyl alcohol, isobornylcyclohexanol, and tetraethylene glycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine, and stearylamine; aliphatic nitriles such as stearonitrile and decanonitrile; silane coupling agents such as alkylalkoxysilanes; and polymeric treatment agents such as polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, and silicone oligomers. One type of surface treatment agent may be used alone, or two or more types may be used in combination.

[0056] The amount of surface treatment agent to be applied can be calculated for copper particles Y using the method described above. The same applies to the molecular weight of the surface treatment agent and the minimum coverage area of ​​the surface treatment agent. For the specific surface area, the specific surface area of ​​copper particles Y described above can be used.

[0057] If the metal paste of this embodiment contains copper particles Z, the total content of copper particles Y and copper particles Z in the metal paste may be 60 to 95 parts by mass, 65 to 90 parts by mass, or 70 to 85 parts by mass, when the total mass of the metal particles is 100 parts by mass.

[0058] Furthermore, the content of copper particles Y and copper particles Z may be 50 to 90 parts by mass and 50 to 10 parts by mass, 55 to 85 parts by mass and 45 to 15 parts by mass, or 60 to 80 parts by mass and 40 to 20 parts by mass, respectively, based on 100 parts by mass of the total of copper particles Y and copper particles Z.

[0059] Furthermore, the content of copper particles Y and copper particles Z may be 50 to 90 parts by mass and 50 to 10 parts by mass, 55 to 85 parts by mass and 45 to 15 parts by mass, or 60 to 80 parts by mass and 40 to 20 parts by mass, respectively, based on 100 parts by mass of the total of silver particles Z, copper particles Y and copper particles Z.

[0060] If the metal paste of this embodiment contains copper particles Z, and the copper particles Z include flattened copper particles with a volume-average particle size of 0.8 μm or more, the total content of the flattened copper particles and silver particles Z in the metal paste of this embodiment may be 40 parts by mass or less when the total mass of the metal particles is 100 parts by mass, from the viewpoint of filling properties, or it may be 20 to 40 parts by mass, from the viewpoint of filling properties and suppressing the occurrence of cracks in the conductive vias due to the difference in thermal expansion between the substrate material and the conductive via material when the substrate on which the conductive vias are formed is subjected to repeated temperature changes.

[0061] The metal paste of this embodiment may also contain metal particles other than silver particles and copper particles (hereinafter also referred to as "other metal particles"). In this case, the other metal particles may be nickel particles, gold particles, palladium particles, platinum particles, titanium particles, zinc particles, aluminum particles, tin particles, bismuth particles, indium particles, or solder particles. One or more of these may be included. The average particle size of the other metal particles may be 0.01 μm or more, 0.03 μm or more, or 0.05 μm or more, and may be 5 μm or less, 3.0 μm or less, or 2.0 μm or less. The average particle size of the solder particles may be 1.0 μm or more, 1.5 μm or more, 2.0 μm or more, 3.0 μm or more, or 4.0 μm or more, and may be 15 μm or less, 10 μm or less, 8.0 μm or less, or 5.0 μm or less.

[0062] The content of other metal particles may be 5 parts by mass or less, 3 parts by mass or less, 1 part by mass or less, or 0.8 parts by mass or less, when the total mass of silver particles and copper particles is 100 parts by mass. The metal paste of this embodiment may not contain other metal particles.

[0063] [Volatile Solvents] Examples of volatile solvents include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol (1,3-butanediol, etc.), α-terpineol, and isobornylcyclohexanol (MTPH); ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether (ethyl carbitol), diethylene glycol butyl ether (diethylene glycol mono-n-butyl ether, etc.), 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 butyl methyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, Ethers such as propyl propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, and tripropylene glycol dimethyl ether; esters such as dimethyl phthalate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, propylene glycol diacetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, and propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; aliphatic hydrocarbons such as cyclohexane, octane, nonane, decane, and undecane; aromatic hydrocarbons such as benzene, toluene, and xylene; mercaptans having alkyl groups with 1 to 18 carbon atoms;Examples of mercaptans include those having a cycloalkyl group with 5 to 7 carbon atoms. Examples of mercaptans having an alkyl group with 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan, and dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group with 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan. The volatile solvent may be used alone or in combination of two or more types.

[0064] The metal paste of this embodiment may contain, as a volatile solvent, a solvent with a vapor pressure of 4 Pa ​​or more and 30 Pa or less at 20°C (hereinafter also referred to as "high vapor pressure solvent"), in order to suppress voids and cracks by suppressing volume shrinkage before and after firing the conductive via precursor (for example, between step c, which forms the conductive via precursor, and step d, which fires the conductive via precursor), as a volatile solvent. One type of high vapor pressure solvent may be used alone, or two or more types may be used in combination.

[0065] Examples of high vapor pressure solvents include α-terpineol, 1,3-butanediol, ethyl carbitol, and propylene glycol diacetate.

[0066] The metal paste of this embodiment may contain a volatile solvent with a vapor pressure of less than 4 Pa ​​at 20°C (hereinafter also referred to as "low vapor pressure solvent") as a volatile solvent, in order to suppress powdering due to drying caused by solvent evaporation during printing or paste preparation. One type of low vapor pressure solvent may be used alone, or two or more types may be used in combination.

[0067] Examples of low vapor pressure solvents include isobornylcyclohexanol (MTPH), dimethyl phthalate, and diethylene glycol mono-n-butyl ether.

[0068] From the viewpoint of achieving both printability and suppressing volume shrinkage before and after firing the conductive via precursor (for example, between step c, which forms the conductive via precursor, and step d, which fires the conductive via precursor), thereby suppressing voids and cracks, the metal paste of this embodiment may contain a high vapor pressure solvent and a low vapor pressure solvent. In this case, the high vapor pressure solvent and the low vapor pressure solvent may be used individually or in combination of two or more. The mass ratio of the high vapor pressure solvent and the low vapor pressure solvent [high vapor pressure solvent / low vapor pressure solvent] may be 20 / 80 to 80 / 20, or 30 / 70 to 70 / 30.

[0069] The volatile solvent content in the metal paste of this embodiment may be 2% by mass or more, 3% by mass or more, or 3.5% by mass or more, based on the total mass of the metal paste, and may be 5% by mass or less, 4.8% by mass or less, 4.5% by mass or less, 4.3% by mass or less, 4% by mass or less, or 3.8% by mass or less, and may be 2 to 5% by mass, 3 to 4.8% by mass, 3 to 3.8% by mass, or 3.5 to 4.5% by mass.

[0070] The metal paste of this embodiment may contain a resin component such as epoxy resin. The metal paste of this embodiment may contain 10% by mass or less of the resin component, 5% by mass or less, or may not contain any resin component at all.

[0071] Metal paste can be prepared by mixing metal particles such as the silver and copper particles mentioned above, along with any other components (additives, etc.), with the volatile solvent mentioned above. After mixing the components, stirring may be performed. The maximum diameter of the dispersion may be adjusted by classification. In addition, means such as a three-roll mixer, kneader, or planetary mixer can be used to mix the components.

[0072] The metal paste may be prepared by first mixing copper particles Y, a surface treatment agent, and a dispersion medium, then performing a dispersion treatment to prepare a dispersion of copper particles Y, and further mixing in silver particles X, and optionally copper particles Z, other metal particles, and any additives. This procedure improves the dispersibility of copper particles Y, which in turn improves the mixability with silver particles X and copper particles Z, thereby further improving the performance of the metal paste. Aggregates may be removed by subjecting the dispersion of copper particles Y to a classification operation.

[0073] From the viewpoint of printability, the viscosity of the metal paste in this embodiment may be 100 to 600 Pa·s or 150 to 400 Pa·s at 25°C, and from the viewpoint of workability, it may be 180 to 350 Pa·s, 180 to 300 Pa·s, 180 to 250 Pa·s, or 180 to 230 Pa·s. The viscosity of the metal paste is measured using a micro-spiral viscometer PCU-02V (manufactured by Malcolm Corporation, product name) under the conditions of rotation speed: 10 rpm and temperature: 25°C.

[0074] Another embodiment of the present invention provides a metal paste containing metal particles and a volatile solvent, wherein the metal particles include metal particles A made of a metal with a Young's modulus of 5 to 99 GPa and metal particles B made of a metal with a Young's modulus of 100 to 250 GPa, and metal particles A includes flattened metal particles X with a volume average particle size of 0.8 μm or more, and metal particles B includes metal particles Y with a volume average particle size of 0.5 μm or less.

[0075] Examples of metal particles A include silver particles, gold particles, aluminum particles, aluminum alloy particles, tin particles, bismuth particles, indium particles, and solder particles (for example, Sn-Ag-Cu particles, Sn-Zn-Al particles, Sn-Bi-Ag particles, etc.).

[0076] Examples of metal particles B include copper particles, nickel particles, platinum particles, titanium particles, palladium particles, and zinc particles.

[0077] Furthermore, if metal particles A and X are silver particles, and metal particles B and Y are copper particles, the metal paste can have the configuration described above according to one embodiment.

[0078] The average particle size, aspect ratio, and content of metal particles X may be the same as those of silver particles X described above. Similarly, the average particle size, specific surface area, shape, aspect ratio, and content of metal particles Y may be the same as those of copper particles Y described above.

[0079] The metal particles B may further contain metal particles Z having a volume-average particle size of 0.8 μm or more. In this case, the average particle size, shape, aspect ratio, and content of the metal particles Z may be the same as those of the copper particles Z described above.

[0080] Furthermore, the content of metal particles, the volatile solvent and its content, and the viscosity of the metal paste may be the same as those of the metal paste according to the embodiment described above.

[0081] <Method for manufacturing a conductive via substrate> The method for manufacturing a conductive via substrate according to this embodiment comprises the steps of: preparing a substrate having holes, filling at least the inside of the holes with the metal paste of this embodiment described above, and firing the metal paste, or the metal paste from which a portion of the volatile solvent has been removed.

[0082] Incidentally, wiring may be further added to the surface of a substrate on which conductive vias are formed by plating or other processes, and in this case as well, it is required that the connection resistance value be sufficiently low. Furthermore, recently, there has been a trend towards higher signal speeds, smaller substrates, and lower power consumption through shorter transmission distances, requiring even greater improvements in connection reliability than before. For these reasons, conductive via substrates (wiring boards) on which the above-mentioned wiring is formed are required to have not only excellent conductivity but also excellent characteristics in that the connection resistance value does not easily increase even when subjected to temperature changes (hereinafter also referred to as "connection reliability").

[0083] From this viewpoint, the manufacturing method of a conductive via substrate according to this embodiment comprises the steps of: preparing a substrate having holes, and providing a metal paste portion containing metal particles and a volatile solvent so as to fill the inside of the holes and cover at least the surface of the substrate around the holes; heating the metal paste portion to remove a portion of the volatile solvent; removing a portion of the heated metal paste portion so as to expose the surface, thereby forming a conductive via precursor containing the remaining metal particles and volatile solvent with a flattened exposed surface inside the holes; and firing the conductive via precursor to form conductive vias. The metal paste portion may be provided by the metal paste described above.

[0084] In the above method, the metal particle concentration in the metal paste portion provided in step a may be 95.0% by mass or more, and the content of the second metal particles in the metal paste portion provided in step a may be 10% by mass or more and 50% by mass or less based on the total amount of metal particles.

[0085] Figures 1 to 3 are schematic diagrams showing an example of a method for manufacturing a conductive via-equipped substrate according to this embodiment. Figure 1 shows an example of a substrate used in the method for manufacturing a conductive via-equipped substrate. The method for manufacturing a conductive via-equipped substrate according to this embodiment will be described below with reference to these figures.

[0086] [Step a] Examples of substrates with holes prepared in this step include organic substrates, silicon substrates, glass substrates, ceramic substrates, printed circuit boards, semiconductor package substrates, etc. The silicon substrate may be a substrate made of polycrystalline silicon, or a rectangular silicon substrate made of polycrystalline silicon. The holes may be through holes or non-through holes. In this embodiment, for example, as shown in Figure 1(a), a silicon wafer 1 with through holes 30 and a silicon substrate 40 having a metal coating 2 provided on the wall surface of the through holes and the surface of the silicon wafer 1 can be prepared. The through holes 30 are connected to both main surfaces of the silicon substrate 40. The following explanation will describe the case in which conductive vias are provided on this silicon substrate 40, but the silicon wafer may be replaced with other insulating substrates in the following explanation.

[0087] The thickness of the silicon wafer 1 may be 100 μm or more, 200 μm or more, or 300 μm or more from the viewpoint of suppressing warping of the substrate after sintering, and may be 800 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less from the viewpoint of reducing the weight and density of the substrate. Furthermore, when using a polycrystalline silicon substrate, the thickness may be 0.05 to 2 mm, 0.1 mm to 1.5 mm, or 0.2 to 1 mm.

[0088] The upper limit of the hole diameter of the through-hole 30 may be 200 μm or less, 100 μm or less, or 60 μm or less, from the viewpoint of increasing the density of the resulting semiconductor device, and the lower limit of the hole diameter of the through-hole 30 is not particularly limited, but may be 10 μm or more, 20 μm or more, 30 μm or more, or 50 μm or more.

[0089] The ratio of the depth to the diameter of the through hole 30 [(depth) / (diameter)] may be 0.5 to 40, 1 to 20, or 2 to 10.

[0090] The number of through holes 30 provided in the silicon substrate 40 is determined from the viewpoint of increasing the density of the resulting semiconductor device, with the number of holes per 1 cm of the main surface of the substrate being such that ２ There may be 100 or more, 200 or more, or 300 or more per unit.

[0091] The metal coating 2 may be provided on both main surfaces of the silicon wafer 1 and on the walls of the through holes 30, on at least one main surface of the silicon wafer 1 and on the walls of the through holes 30, on the walls of the through holes 30 only, or not provided at all. In the embodiment shown in Figure 1(a), the silicon substrate 40 has the metal coating 2 on both main surfaces of the silicon wafer 1 and on the walls of the through holes 30.

[0092] Examples of metal coating 2 include titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold. From the viewpoint of adhesion, it is preferable that the metal coating 2 is a coating in which titanium, nickel, and copper are layered in that order. Adhesion is improved by oxidizing the surface of the silicon wafer 1 to silicon oxide and forming a titanium layer on top of the silicon oxide. Furthermore, by providing a nickel layer on top of the titanium layer and then a copper layer on top of that, the diffusion of copper into the silicon wafer 1 can be suppressed compared to the case where the copper layer is directly provided on top of the titanium layer. In addition, by providing a copper layer on the surface, the adhesion between the copper layer and the copper particles in the metal paste is improved, and reliability is improved.

[0093] Furthermore, as shown in Figure 1(b), when a silicon substrate 41 is prepared that has non-through holes 31 as holes, conductive vias, which are through electrodes, can be formed by grinding the side of the silicon substrate opposite to the side where the non-through holes 31 are open after steps a, b, c, or d. Examples of grinding methods include mechanical polishing and chemical mechanical polishing.

[0094] The metal paste portion 3 can be provided, for example, by directly applying a metal paste containing metal particles and a volatile solvent onto the silicon substrate 40, or by preparing a film coated with metal paste in advance and pressing it onto the substrate. In the former method, examples of methods for applying or filling the metal paste include printing methods such as screen printing, inkjet printing, intaglio printing, lithographic printing, offset printing, and flexographic printing, as well as printing methods combining these methods, spin coating, dipping, rolling, squeegeeing, and pressing. Of these methods, screen printing and squeegeeing, which directly fill the substrate under a vacuum atmosphere, and vacuum pressing, which presses a film coated with metal paste in advance under a vacuum atmosphere, are preferred.

[0095] In the latter method, as shown in Figures 2(a) to 2(c), the metal paste portion 3 can be formed, for example, by creating a metal particle film on a support film 7, which is made of a metal particle-containing layer 3p made of the metal paste of this embodiment described above, and then pressing this metal particle film onto a substrate.

[0096] Examples of the support film 7 include polyimide film, polyethylene naphthalate film, and polyethylene terephthalate film. The thickness of the support film may be 20 to 200 μm, 25 to 175 μm, or 30 to 150 μm, from the viewpoint of workability for forming the metal particle-containing layer by coating.

[0097] The composition of the metal particles and volatile solvent in the metal particle-containing layer can be appropriately set so as to satisfy the conditions for the metal paste of this embodiment described above. The thickness of the metal particle-containing layer may be 100 μm or less. From the viewpoint of ensuring sufficient filling of through holes or non-through holes, the thickness of the metal particle-containing layer may be 30 μm or more, 40 μm or more, or 50 μm or more.

[0098] From the viewpoint of suppressing the generation of voids in through-holes or non-through-holes, the waviness (height difference) on the surface opposite to the support film of the metal particle-containing layer may be 20 μm or less, or 10 μm or less. By reducing the waviness (height difference), when the metal particle film is pressed and the metal particle composition is filled into the holes of the substrate, it becomes easier to simultaneously fill the numerous through-holes or non-through-holes present in the substrate, making it easier to reduce the number of through-holes or non-through-holes that are completely unfilled, or through-holes or non-through-holes where voids partially occur. The waviness (height difference) can be evaluated by non-contact measurement using a laser displacement meter or the like.

[0099] The metal particle film described above can be produced by applying the metal paste of this embodiment described above onto a support film to form a metal particle-containing layer in which the concentration of metal particles is 95.0% by mass or more, or by applying a metal paste in which the content of volatile solvent is increased (for example, increased to an amount in which the concentration of metal particles is less than 94.0% by mass), and drying the coated film to form a metal particle-containing layer in which the concentration of metal particles is 95.0% by mass or more.

[0100] Methods for applying metal paste include, for example, screen printing, transfer printing, offset printing, jet printing, dispensers, jet dispensers, needle dispensers, comma coaters, slit coaters, die coaters, gravure coaters, slit coats, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, bar coating, applicators, particle deposition methods, spray coaters, spin coaters, dip coaters, and the like.

[0101] From the viewpoint of ease of application and uniformity of the applied film thickness, metal paste can be applied onto a support film by screen printing.

[0102] The thickness of the coating film may be 1 μm or more, 2 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more, and may be 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, 120 μm or less, 100 μm or less, 80 μm or less, or 50 μm or less.

[0103] The step of drying the coating film to form a metal particle-containing layer can be carried out at room temperature or at a temperature between room temperature and 100°C or lower, and the atmosphere may be air or nitrogen.

[0104] In step a, the metal particle film described above is pressed onto the silicon substrate 40 so that the metal particle-containing layer 3p of the metal particle film is in contact with the silicon substrate 40, thereby filling the through-holes 30 of the silicon substrate 40 with metal paste. In this case, for example, as shown in Figure 2(b), the metal particle film and the silicon substrate 40 can be pressed together from above and below using a pressure jig A. The pressure jig A is not particularly limited, but may be a commercially available one, or it may be made using a metal member having a flat portion. For example, a pressure jig having two or more of the above-mentioned metal members can press the metal particle film onto the silicon substrate by sandwiching the metal particle film and the silicon substrate between metal members arranged so that their flat portions face each other. The pressure jig A may have a mechanism for adjusting the pressure applied to the metal particle film and the silicon substrate. A spring or the like can be used as a pressure adjustment means. In this embodiment, a vacuum press method in which pressing is performed in a vacuum atmosphere may be used.

[0105] The pressing conditions can be, for example, room temperature to 50°C or below, and the atmosphere may be a vacuum, air, or nitrogen. To reduce voids, the metal particle film may be pressed onto the silicon substrate after maintaining a vacuum of 1000 Pa or less, or a vacuum of 200 Pa or less. The pressure of the pressing jig when pressing the metal particle film onto the silicon substrate should be within a range that does not cause the silicon wafer to crack, for example, 0.01 MPa or more, 0.1 MPa or more, or 1 MPa or more.

[0106] The metal paste portion 3 only needs to fill the inside of the hole and cover at least the surface of the substrate around the hole, but as shown in Figures 2(b) and (c), the opening of the through hole located on the opposite side of the side of the substrate from where the metal particle film is pressed (VP in Figure 2(a)) ０ The metal paste portion may protrude from the hole and cover the surface around it.

[0107] [Step b] In this step, the metal paste is heated to remove a portion of the volatile solvent; in other words, the metal paste is heated so that a portion of the volatile solvent remains. If the above-mentioned metal particle film is used, the metal paste can be heated after the support film has been removed.

[0108] For heating, for example, a hot plate, hot air dryer, hot air heating furnace, nitrogen dryer, infrared dryer, infrared heating furnace, far infrared heating furnace, microwave heating device, laser heating device, electromagnetic heating device, heater heating device, steam heating furnace, hot plate press device, etc. can be used.

[0109] The heating atmosphere may be air, an oxygen-free atmosphere such as nitrogen and noble gases, or a reducing atmosphere such as hydrogen and formic acid. In the case of air, if the heating temperature exceeds 100°C, metal particles such as copper particles tend to oxidize. However, if the metal paste contains the high vapor pressure solvent mentioned above as a volatile solvent, a portion of the volatile solvent can be removed at temperatures below 100°C, 95°C or below, or 90°C or below. If the metal paste does not contain the high vapor pressure solvent as a volatile solvent, for example, if it contains only the low vapor pressure solvent mentioned above, heating at 110°C or above, 130°C or above, or 150°C or above in an oxygen-free or reducing atmosphere can suppress the oxidation of metal particles such as copper particles while removing a portion of the volatile solvent.

[0110] When the metal paste portion contains a high vapor pressure solvent, the heating temperature may be 70°C or higher but less than 100°C, or 80°C or higher but 95°C, from the viewpoint of suppressing oxidation of metal particles such as copper particles, and the heating time may be 5 to 60 minutes, or 10 to 30 minutes, from the viewpoint of suppressing oxidation of metal particles such as copper particles.

[0111] Furthermore, in order to suppress volume shrinkage before and after firing the conductive via precursor (for example, between step c, which forms the conductive via precursor, and step d, which fires the conductive via precursor), and to suppress voids and cracks, the metal paste portion may be heated to a concentration of metal particles of 96% by mass or more, 97.5% by mass or more, and 98% by mass or more.

[0112] [Step c] In this step, as shown in Figures 3(a) to (d), the metal paste covering the surface of the substrate is removed from the heated metal paste portion 3a obtained in step b, while the metal paste filling the holes is flattened (or smoothed). This flattenes the exposed surface VP １ A conductive via precursor 3b containing metal particles and the remainder of a volatile solvent can be formed inside the hole (through hole 30) (Figure 3(d)).

[0113] The metal paste portion can be removed by using a rubber squeegee 42, for example, as shown in Figures 3(b) and 3(d). This removes the surface SP of the substrate 40. ０ and the exposed surface VP of the conductive via precursor 3b １ A portion of the metal paste (the metal paste covering the surface of the substrate and the metal paste protruding from the holes) can be removed so that the two surfaces form a single plane. Another method involves removal using a metal squeegee made of stainless steel or similar material.

[0114] Surface SP of substrate 40 ０ And the exposed surface VP of the conductive via precursor 3b １ The step difference may be 5 μm or less, or 3 μm or less, in the direction perpendicular to the substrate surface. Furthermore, the average step difference calculated by the following method may be within the above range. (Average step difference) An image of the cross section passing through the center of the hole (via) is obtained, and the cross section image is binarized to obtain the cross-sectional area Sa enclosed by the inner wall of the hole (via), the exposed surface of the conductive via precursor, and the opening surface of the hole (via), and the average step difference is calculated by dividing this by the spacing Wa of the inner walls of the hole.

[0115] [Step d] In this step, the conductive via precursor 3b formed in step c is fired. This allows for the formation of a conductive via 3c made of a metal body. The metal body may include a sintered metal body having a porous structure. The porosity of the conductive via may be 7% or less, 1.0 to 6.5%, or 1.5 to 5.0%, from the viewpoint of suppressing the penetration of chemicals into the sintered metal body when immersed in chemicals such as resist stripping solution or pre-plating treatment in subsequent processes, and improving reliability. If the conductive via is made of a sintered metal body, the porosity of the sintered metal body may be within the above range. The porosity can be determined by the method described in the examples.

[0116] Firing can be carried out by heat treatment. For heat treatment, heating means such as a hot plate, hot air dryer, hot air heating furnace, nitrogen dryer, infrared dryer, infrared heating furnace, far infrared heating furnace, microwave heating device, laser heating device, electromagnetic heating device, heater heating device, steam heating furnace, etc. can be used.

[0117] The atmosphere during firing may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the metal sintered body, or a reducing atmosphere from the viewpoint of removing surface oxides from metal particles such as copper particles in the conductive via precursor. Examples of an oxygen-free atmosphere include the introduction of oxygen-free gases such as nitrogen or noble gases, or under vacuum. Examples of a reducing atmosphere include pure hydrogen gas, a mixed gas of hydrogen and nitrogen represented by a forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and a noble gas, or a noble gas containing formic acid gas. When sintering the conductive via precursor by heating without pressurization, a pure hydrogen gas or a mixed gas of hydrogen and nitrogen represented by a forming gas is preferred, and a pure hydrogen gas is preferable. Heating in a pure hydrogen gas makes it possible to lower the sintering temperature of the copper particles. When using pure hydrogen gas, even if the substrate thickness is thick, such as 600 μm to 2000 μm, or the diameter of the through-hole 30 is as small as 10 μm, the gas can reach the center of the through-hole 30, making it easy to obtain a metal body containing a metal sintered body.

[0118] The maximum temperature reached during the heat treatment may be 150°C or higher, and may be 350°C or lower, 300°C or lower, or 260°C or lower, from the viewpoint of reducing thermal damage to each component and improving yield. If the maximum temperature reached is 150°C or higher, sintering tends to proceed sufficiently when the maximum temperature is held for 60 minutes or less. The maximum temperature is held for 1 minute or more, and may be 60 minutes or less, 40 minutes or less, or 30 minutes or less, from the viewpoint of completely evaporating the volatile solvent and improving yield.

[0119] In this embodiment, by using the metal paste of this embodiment, sintering can be performed at a low temperature of 300°C or less, 200°C or less, or 150°C or less in an atmosphere containing formic acid gas, and firing may also be performed at 100-300°C, 100-200°C, or 100-150°C. In this case as well, conductive vias with excellent conductivity and connection reliability can be formed.

[0120] The firing of the conductive via precursor may be carried out under no pressure or under pressure. In the latter case, under an atmosphere containing pure hydrogen gas, the pressure may be 0.05 MPa or higher, 0.1 MPa or higher, or 0.3 MPa or higher, and 20 MPa or lower, 15 MPa or lower, or 10 MPa or lower. Under an atmosphere containing nitrogen gas, the pressure may be 1 MPa or higher, or 3 MPa or higher, and 20 MPa or lower, 15 MPa or lower, or 10 MPa or lower.

[0121] By setting the pressure to 0.05 MPa or higher when using pure hydrogen gas, or 1 MPa or higher when using nitrogen gas, it becomes easier to suppress the generation of voids in the conductive via formed in the center of the through hole 30, and conductive vias with good conductivity can be easily obtained. Furthermore, by setting the pressure to above the lower limit mentioned above, if the silicon substrate 40 has a metal coating 2, it becomes easier to improve the bonding strength between the metal coating 2 and the conductive via.

[0122] Furthermore, if the pressure applied during firing is within the above range, a special pressurizing device is not required, thus reducing voids, improving bonding strength, and connection reliability without compromising yield. Methods for applying pressure to a silicon substrate with conductive via precursors formed in through-holes include, for example, placing weights on it, using a pressurizing device to apply pressure, and using a fixing jig for applying pressure.

[0123] When a metal paste portion is formed using a metal paste containing silver particles and copper particles according to this embodiment, the proportions of copper and silver elements in the metal sintered body contained in the metal body, excluding light elements, may be 60 to 95% by mass and 5 to 40% by mass, respectively, or 65 to 90% by mass and 10 to 35% by mass. Furthermore, the metal sintered body may contain flattened silver structures derived from the silver particles X.

[0124] When the above-mentioned ratios of copper and silver elements in the metal sintered body are within the above-mentioned range, and the metal sintered body contains a flattened silver structure, the metal sintered body can have sufficient properties of metallic copper while having a low sintering density and a low Young's modulus, making it easier to obtain even better connection reliability.

[0125] When a metal paste portion is formed using a metal paste containing metal particles A and metal particles B according to this embodiment, the proportions of the metal elements constituting metal particles A and metal elements constituting metal particles B among the constituent elements, excluding light elements, may be within the same range as described above.

[0126] In step d, the conductive via precursor is exposed on a flat surface VP that has a sufficiently small step difference from the substrate surface. １ It has the properties of and also has a composition that is less prone to volume shrinkage due to firing, so the surface SP of the substrate 40 ０ And the exposed surface VP of conductive via 3c ２ The difference in height can be made sufficiently small.

[0127] Surface SP of substrate 40 ０ And the exposed surface VP of conductive via 3c ２The step difference (or indentation of the conductive via 3c) may be 5 μm or less, or 3 μm or less, in the direction perpendicular to the substrate surface. Furthermore, the average step difference calculated by the following method may be within the above range. (Average step difference) An image of the cross section passing through the center of the hole (via) is obtained, and the cross section image is binarized to obtain the cross-sectional area Sb enclosed by the inner wall of the hole (via), the exposed surface of the conductive via, and the opening surface of the hole (via), and the average step difference is calculated by dividing this by the spacing Wb of the inner walls of the hole.

[0128] After going through the above steps a to d, a conductive via-equipped substrate 50 can be obtained. The conductive via-equipped substrate 50 has a flat (smooth) surface on which the conductive vias are exposed, and the surface SP of the substrate 40 ０ Because the difference in height is sufficiently small, wiring can be easily formed, and even after wiring is formed, a sufficiently low connection resistance value can be achieved.

[0129] The method for manufacturing a conductive via-equipped substrate according to this embodiment may further include a step e for forming wiring. In this case, it can be used as a method for manufacturing a conductive via-equipped wiring substrate.

[0130] [Step e] This step may include the resist formation step, plating step, resist removal step, and etching step described below.

[0131] <Resist Formation Process> In the resist formation process, for example, as shown in Figures 4(a) and 4(b), a negative-type photosensitive dry film 8 for etching resist is laminated onto the main surface and conductive vias 3c of the silicon substrate 40. Then, a photomask that transmits light is placed over the wiring shape, and the area is exposed to ultraviolet light. The unexposed areas are removed with a developer to form the etching resist 8a.

[0132] Other methods for forming the etching resist 8a include, for example, a method of silkscreen printing the resist ink and a method of laminating dry film resists using a laminator.

[0133] <Plating Process> In the plating process, for example, as shown in Figure 4(c), wiring 9 can be formed in the openings of the etching resist 8a by methods such as electroplating or electroless plating.

[0134] <Resist Removal Process> In the resist removal process, for example, as shown in Figure 4(d), the etching resist 8a can be removed by methods such as a wet process using an alkaline aqueous solution or an organic solvent-based chemical solution such as an organic amine-based solution like TMAH and a ketone-based solution like acetone, or by a dry process such as plasma or ozone.

[0135] <Etching Process> In the etching process, the metal coating 2 in areas not covered by the wiring 9 can be removed by etching. In this embodiment, a portion of the metal coating 2 provided on both main surfaces of the silicon wafer 1 is removed by etching.

[0136] Etching methods include, for example, using chemical etching solutions commonly used for printed circuit boards, such as a solution of cupric chloride and hydrochloric acid, a ferric chloride solution, a solution of sulfuric acid and hydrogen peroxide, or an ammonium persulfate solution.

[0137] By step e described above, a conductive via-equipped wiring board 52, as shown in Figure 4(e), can be obtained.

[0138] In the method described above, a step may be provided before step e to remove at least a portion of the conductive material, such as the sintered metal paste or the metal coating 2, that remains on the main surface of the silicon substrate 40.

[0139] Methods for removing conductive materials include chemical polishing, mechanical polishing, chemical-mechanical polishing, fly cutting, and plasma treatment. Fly cutting refers to planar cutting using a surface plane.

[0140] Furthermore, a metal film may be formed on the surface of the conductive via substrate 50 obtained through the above-described steps a to d. Examples of metal films include titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold. From the viewpoint of adhesion and subsequent etching processes, the metal film is preferably made of copper. The metal film can be formed by plating or sputtering, but sputtering is more preferable. In this case, in the resist formation step, plating step, resist removal step, and etching step described above, oxidation of the metal sintered body can be suppressed by preventing the penetration of chemicals into the metal sintered body having a porous structure, thereby improving reliability.

[0141] According to the manufacturing method of the conductive via-equipped substrate of this embodiment, a conductive via-equipped substrate can be obtained in which the main surface of the substrate (for example, the metal film 2, etc.) is sufficiently exposed and the difference in height between the conductive via and the main surface of the substrate is sufficiently small. Therefore, steps for smoothing the main surface of the substrate, such as the step of removing the conductor mentioned above, can be omitted.

[0142] Furthermore, in this embodiment, step S2 may be performed to provide a resin-containing portion containing a curable resin composition to the conductive vias of the conductive via-equipped substrate obtained through steps a to d described above. The curable resin composition may be a photosensitive resin composition or a cured product thereof. This makes it even easier to maintain excellent connection reliability even after wiring formation. The inventors speculate that the reasons for these effects are as follows. First, by forming conductive vias with a porous metal sintered body, stress relaxation is obtained, and the effect of suppressing cracking of the material around the metal sintered body is easily obtained. On the other hand, a porous metal sintered body is susceptible to adverse effects such as oxidation due to the penetration of chemicals used during wiring formation (for example, oxidation of the metal sintered body due to the penetration of an aqueous solution). In contrast, it is thought that the above adverse effects can be sufficiently reduced by providing a resin-containing portion in the conductive via. Also, when a photosensitive resin composition is used, it is thought that the resin composition can be removed from the surface of the metal sintered body while leaving the resin composition inside the metal sintered body by the corresponding developing process, which is also considered to be one of the reasons for obtaining the above effects.

[0143] Furthermore, the conductive via may be provided with the resin-containing portion and a resin-free portion that does not contain the resin composition or its cured product, such that the resin-containing portion is predominantly located on the opening side (the exposed surface side of the conductive via). This suppresses the increase in connection resistance due to the resin-containing portion while preventing adverse effects from the penetration of chemicals or the like during subsequent wiring formation processes.

[0144] Examples of components constituting a curable resin composition include thermosetting compounds. Examples of thermosetting compounds include oxetane compounds, epoxy compounds, episulfide compounds, (meth)acrylic compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. Among these, epoxy compounds may be used to further improve the curability and viscosity of the curable resin composition and to enhance its properties and insulation reliability when stored at high temperatures.

[0145] The curable resin composition may further contain a thermosetting agent. Examples of thermosetting agents include imidazole curing agents, amine curing agents, phenol curing agents, polythiol curing agents, acid anhydrides, thermal cationic initiators, and thermal radical generators. These may be used individually or in combination of two or more. Of these, imidazole curing agents, polythiol curing agents, or amine curing agents are preferred because they can be cured rapidly at low temperatures. Furthermore, latent curing agents are preferred from the viewpoint of improving storage stability when the thermosetting compound and thermosetting agent are mixed. The latent curing agent is preferably a latent imidazole curing agent, a latent polythiol curing agent, or a latent amine curing agent. The above thermosetting agents may be coated with a polymeric substance such as polyurethane resin or polyester resin.

[0146] The photosensitive resin composition can be any composition that can form a predetermined pattern by exposure and development, and may be negative or positive type.

[0147] Methods for providing a resin-containing portion containing a photosensitive resin composition on a conductive via include laminating a film-like photosensitive resin composition or applying a liquid photosensitive resin composition. When providing a resin-containing portion containing a cured product of a photosensitive resin composition on a conductive via, the photosensitive resin composition can be cured after providing the resin-containing portion containing the photosensitive resin composition. In this case, the photosensitive resin composition may contain a thermosetting component and be thermosetting.

[0148] Step S2 may include step S2-1a, in which a film-like negative-type photosensitive resin composition is laminated onto the surface of a substrate with conductive vias, thereby impregnating at least a portion of the conductive vias with the negative-type photosensitive resin composition; and step S2-2a, after step S2-1a, in which the film-like negative-type photosensitive resin composition is removed by a developing process, thereby exposing the conductive vias having a resin-containing portion containing the negative-type photosensitive resin composition at the opening of the holes.

[0149] The film-like negative-type photosensitive resin composition can use dry film resists such as photocurable dry film resists and thermosetting dry film resists. For example, commercially available products such as RD-1619 (manufactured by Resonac Corporation, product name), HM-4035 (manufactured by Resonac Corporation, product name), HM-4056 (manufactured by Resonac Corporation, product name), TMMF NA1000 (manufactured by Tokyo Ohka Kogyo Co., Ltd., product name), and PSR-800 AUS SR-1 (manufactured by Taiyo Ink Manufacturing Co., Ltd., product name) may be used.

[0150] Methods for laminating a film-like negative-type photosensitive resin composition include using a roll laminator, a laminator, or a press.

[0151] The pressure may be 0.1 MPa or higher, 0.4 MPa or higher, or 1 MPa or higher, from the viewpoint of facilitating the impregnation of the conductive vias with the photosensitive resin composition. The upper limit of the pressure may be 10 MPa or lower, from the viewpoint of minimizing the impact on the substrate.

[0152] From the viewpoint of facilitating impregnation of the conductive vias with the photosensitive resin composition, lamination may be performed while heating. The heating temperature is not particularly limited as long as it is within the range in which the photosensitive resin composition does not harden, and may be 50°C to 100°C or 70°C to 90°C.

[0153] From the viewpoint of facilitating the impregnation of the conductive vias with the photosensitive resin composition, the vias may be laminated with a film-like negative-type photosensitive resin composition after being maintained at a vacuum level of 1000 Pa or less, or 200 Pa or less.

[0154] From the viewpoint of connection reliability, the depth to which the photosensitive resin composition is impregnated into the conductive via may be 0.2% or more, 0.5% or more, or 1% or more of the total length of the conductive via in the thickness direction of the substrate, and the distance of the conductive via from the exposed surface may be 1 μm or more, 2 μm or more, or 3 μm or more.

[0155] In step S2-2a, a developing process corresponding to the photosensitive resin composition can be performed. As the developing solution, for example, an alkaline aqueous solution obtained by dissolving an alkaline compound such as sodium carbonate, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, or choline in water to a concentration of about 1 to 10% by mass, or an alkaline aqueous solution such as ammonia water can be used. Examples of developing methods include shower developing, spray developing, immersion developing, and paddle developing.

[0156] Step S2 may further include step S2-3a, which involves curing the negative-type photosensitive resin composition contained in the resin-containing portion, after step S2-2a.

[0157] When photocuring, the active light used for exposure can include, for example, light from a g-line stepper; ultraviolet light from a low-pressure mercury lamp, high-pressure mercury lamp, metal halide lamp, i-line stepper, etc.; electron beams; laser light. The exposure amount is appropriately selected depending on the light source used, the thickness of the impregnated photosensitive resin composition, etc.

[0158] If the negative-type photosensitive resin composition contains a thermosetting component, it may be thermoset.

[0159] Step S2 may further include step S2-4a, which involves performing a desmear treatment on at least the exposed surface of the conductive vias, after step S2-3a.

[0160] Examples of desmear treatments include plasma cleaning and treatment with a desmear solution containing permanganate and a caustic composition (e.g., alkali metal hydroxide).

[0161] In another embodiment, step S2 may include step S2-1b, in which a liquid negative-type photosensitive resin composition is applied to the surface of a substrate with conductive vias, thereby impregnating at least a portion of the conductive vias with the negative-type photosensitive resin composition; and step S2-2b, after step S2-1b, in which the coating of the liquid negative-type photosensitive resin composition is removed by a developing process, thereby exposing the conductive vias having a resin-containing portion containing the negative-type photosensitive resin composition at the opening of the holes.

[0162] The liquid negative-type photosensitive composition may be a commercially available product such as PSR-4000 G24K / CA-40 G24 (manufactured by Taiyo Ink Manufacturing Co., Ltd., product name), TER-20HF (manufactured by Taiyo Ink Manufacturing Co., Ltd., product name), or TMMR NA1000PM (manufactured by Tokyo Ohka Kogyo Co., Ltd., product name).

[0163] Methods for applying a liquid negative-type photosensitive composition include, for example, screen printing, transfer printing, offset printing, jet printing, dispensers, jet dispensers, needle dispensers, comma coaters, slit coaters, die coaters, gravure coaters, slit coats, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, bar coating, applicators, particle deposition methods, spray coaters, spin coaters, and dip coaters. From the viewpoint of ease of application and uniformity of the coating film thickness, application may be done by screen printing or spin coating.

[0164] The depth to which the photosensitive resin composition is impregnated into the conductive vias, and the method for developing the coating film of the liquid negative-type photosensitive resin composition, may be the same as in steps S2-1a and S2-2a described above.

[0165] Furthermore, after step S2-2b, step S2-3b may be performed to cure the negative-type photosensitive resin composition contained in the resin-containing portion, similar to steps S2-3a and S2-4a described above, and after step S2-3b, step S2-4b may be performed to desmear at least the exposed surface of the conductive via.

[0166] In another embodiment, step S2 may include step S2-1c, in which a positive-type photosensitive resin composition is impregnated into at least a portion of the metal sintered body by applying a liquid positive-type photosensitive resin composition to the surface of the conductive via-equipped substrate or by laminating a film-like positive-type photosensitive resin composition; and step S2-2c, after step S2-1c, in which the coating of the liquid positive-type photosensitive resin composition or the film-like positive-type photosensitive resin composition is removed by exposure and development to expose the conductive via having a resin-containing portion containing the positive-type photosensitive resin composition at the opening of the hole.

[0167] Positive-type photosensitive compositions may include commercially available products such as AH-3000 (manufactured by Resonaq Corporation, product name), AR-5100 (manufactured by Resonaq Corporation, product name), and OFPR-8600 (manufactured by Tokyo Ohka Kogyo Co., Ltd., product name).

[0168] The above-described methods can be used for coating and laminating the photosensitive composition.

[0169] The depth to which the photosensitive resin composition is impregnated into the conductive via may be the same as in step S2-1a described above.

[0170] Exposure in step S2-2c can be performed using, for example, light from a g-line stepper; ultraviolet light from a low-pressure mercury lamp, high-pressure mercury lamp, metal halide lamp, i-line stepper, etc.; electron beams; laser light, etc. The exposure amount is appropriately selected depending on the light source used, the thickness of the impregnated photosensitive resin composition, etc.

[0171] The method for developing a coating film of a liquid positive-type photosensitive resin composition or a film-like positive-type photosensitive resin composition may be the same as in step S2-2a described above.

[0172] Furthermore, if the positive-type photosensitive resin composition contains a thermosetting component, step S2-3c may be performed after step S2-2c to thermoset the positive-type photosensitive resin composition contained in the resin-containing portion. In addition, after step S2-3c, step S2-4c may be performed to desmear at least the exposed surface of the conductive via, similar to step S2-4a described above.

[0173] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0174] [Preparation of Metal Paste] (Preparation Examples 1-19 and Comparative Preparation Examples 1-3) Metal pastes were prepared by mixing the raw materials shown below in the proportions shown in Tables 1 and 2 using a three-roll mixing machine.

[0175] <First type of copper particles> (Wet copper powder) Spherical copper particles 1W2: 1100Y (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size (D50): 1.1 μm, spherical) Spherical copper particles 1W4: 1300Y (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size (D50): 3.5 μm, spherical) Flattened copper particles 1W1: 1100YP (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size (D50): 1.4 μm, flattened) Flattened copper particles 1W2: 1200YP (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size (D50): 3.1 μm, flattened) (Atomized copper powder) Spherical copper particles 1A2: MA-C025K (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size (D50): 2.4 μm, spherical)

[0176] <Second type of copper particle> Spherical copper particle 2WS1: CH0200L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size (D50): 210 nm, spherical shape, specific surface area 3.3 m²) ２ / g) Spherical copper particles 2WS4: CH0200L1 (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 350 nm, spherical shape, specific surface area 1.9 m ２ / g)

[0177] <Silver Particles> Flattened silver particle 1: AgC-271B (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., average particle size (D50): 2.1 μm, flattened, aspect ratio: 6.0) Flattened silver particle 2: AgC-221PA (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., average particle size (D50): 7.5 μm, flattened, aspect ratio: 10.0)

[0178] <Volatile Solvents> (High vapor pressure solvents: vapor pressure of 4 Pa ​​or more and 30 Pa or less at 20°C) α-Terpineol: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., vapor pressure of 6.5 Pa at 20°C (Low vapor pressure solvents: vapor pressure of less than 4 Pa ​​at 20°C) Diethylene glycol mono-n-butyl ether: Manufactured by Showa Chemical Co., Ltd., vapor pressure of 1.3 Pa at 20°C

[0179] The viscosity, printability, and bonding properties of the metal pastes obtained in Preparation Examples 1 to 19 and Comparative Preparation Examples 1 to 3 were evaluated according to the following method, as well as the volume resistivity and Young's modulus of the sintered body.

[0180] <Viscosity> The viscosity of the metal paste was measured using a micro-spiral viscometer PCU-02V (manufactured by Malcolm Corporation). The measurement conditions were a rotation speed of 10 rpm and a temperature of 25°C.

[0181] <Printability> In the <Preparation of Metal Particle Film> described later, when printing on a 100 μm thick PET film using a screen printing machine, the number of pinholes that could not be coated onto the PET film was measured. Based on the number of pinholes, the printability was evaluated according to the following criteria. A to D ratings are considered good. (Criteria) A: 0 pinholes B: 1 or more but less than 3 pinholes C: 3 or more but less than 5 pinholes D: 5 or more but less than 10 pinholes E: 10 or more but less than 20 pinholes F: 20 or more pinholes

[0182] Furthermore, in the "Preparation of Metal Particle Film" described later, the coating amount (g) for an 8-inch diameter film was measured after printing on a 100 μm thick PET film using a screen printing machine.

[0183] <Bonding Performance> Bonding samples for shear strength testing were prepared and die shear strength was measured according to the following method, and the bonding performance was evaluated according to the following criteria. Bonding performance can be judged as good if it is rated A to C.

[0184] (Preparation of joint samples for shear strength testing) 3 x 3 mm ２Using a 100 μm thick stainless steel mask with a square opening and a squeegee, metal paste was stencil-printed onto a copper plate measuring 25 × 20 × 3 mm thick. After drying at 90°C for 10 minutes using a hot plate, the plate was placed in a tube furnace (manufactured by AVC Co., Ltd.), and the air inside the tube furnace was replaced with argon gas by flowing argon gas at a flow rate of 1 L / min. Subsequently, the temperature was raised to 225°C in 10 minutes while flowing hydrogen gas at 300 mL / min, and the metal paste was sintered by sintering at 225°C for 60 minutes. After that, the plate was cooled by flowing argon gas at a flow rate of 0.3 L / min, and removed from the air at a temperature below 50°C to obtain a substrate with a metal body formed on the copper plate as a bonding sample for shear strength testing.

[0185] (Measurement of Die Shear Strength) For bond samples used in shear strength testing, a universal bond tester (4000 series, manufactured by Daisy Japan Co., Ltd.) equipped with a DS-100 load cell was used to measure the die shear strength by pressing a metal body or Cu plate horizontally under measurement conditions of measurement speed: 5 mm / min and measurement height: 50 μm. The average value of 10 points was calculated and used as the average bond strength. (Judgment Criteria) A: Average bond strength of 50 N or more B: Average bond strength of 40 N or more and less than 50 N C: Average bond strength of 20 N or more and less than 40 N D: Average bond strength of 10 N or more and less than 20 N E: Average bond strength of less than 10 N

[0186] <Measurement of Volume Resistivity of Sintered Body - 1> The metal paste prepared above was applied to a 1 mm thick glass wafer using an automatic film applicator (manufactured by Allgood Co., Ltd.) to a coating thickness of approximately 150 μm. The coating area was approximately 5 cm x 10 cm. Next, the wafer with the coated film was dried at 90°C for 10 minutes using a hot plate, then placed in a tube furnace (manufactured by AVC Co., Ltd.), and the air inside the tube furnace was replaced with argon gas by flowing argon gas at a rate of 1 L / min. After that, the temperature was raised to 300°C in 10 minutes while flowing hydrogen gas at a rate of 300 mL / min, and the metal paste was sintered by performing a sintering treatment at 300°C for 60 minutes. After that, the wafer was cooled by flowing argon gas at a flow rate of 0.3 L / min, and removed into the air at a temperature of 50°C or lower to obtain Sample 1 in which a metal body was formed on the wafer.

[0187] <Measurement of Volume Resistivity of Sintered Body - 2> The metal paste prepared above was applied to a 1 mm thick glass wafer using an automatic film applicator (manufactured by Allgood Co., Ltd.) to a coating thickness of approximately 150 μm. The coating area was approximately 5 cm x 10 cm. Next, the wafer with the coated film was dried at 90°C for 10 minutes using a hot plate, then placed in a tube furnace (manufactured by AVC Co., Ltd.), and the air inside the tube furnace was replaced with argon gas by flowing argon gas at a rate of 1 L / min. After that, the temperature was raised to 225°C in 10 minutes while flowing hydrogen gas at a rate of 300 mL / min, and the metal paste was sintered by performing a sintering treatment at 225°C for 60 minutes. After that, the wafer was cooled by flowing argon gas at a flow rate of 0.3 L / min, and removed into the air at a temperature of 50°C or lower to obtain sample 2 in which a metal body was formed on the wafer.

[0188] The volume resistivity of the metal bodies in Sample 1 and Sample 2 described above was calculated from the surface resistance values ​​measured with a four-point needle surface resistance measuring instrument (Mitsubishi Analytec Co., Ltd., product name: Loresta GP) and the film thickness obtained with a non-contact surface and layer cross-sectional shape measurement system (VertScan, Ryoka Systems Co., Ltd.).

[0189] <Measurement of Young's Modulus of Sintered Body - 1> The metal paste prepared above was coated onto a glass substrate so that the size after drying was 40 mm × 10 mm × 0.22 mm. Next, the metal paste coating was fired using the following procedure. The glass substrate with the metal paste coating was placed in a tube furnace (manufactured by AVC Co., Ltd.), and the air inside the tube furnace was replaced with argon gas by flowing argon gas at a rate of 1 L / min. Next, the temperature was raised to 300°C in 10 minutes while flowing hydrogen gas at a rate of 300 mL / min, and a sintering treatment was performed at 300°C for 60 minutes. After that, the glass substrate with the formed sintered body was cooled by flowing argon gas at a flow rate of 0.3 L / min, and the glass substrate was removed into the air at a temperature of 50°C or lower to obtain Sample 1.

[0190] <Measurement of Young's Modulus of Sintered Body - 2> The metal paste prepared above was coated onto a glass substrate so that the size after drying was 40 mm × 10 mm × 0.22 mm. Next, the metal paste coating was fired using the following procedure. The glass substrate with the metal paste coating was placed in a tube furnace (manufactured by AVC Co., Ltd.), and the air inside the tube furnace was replaced with argon gas by flowing argon gas at a rate of 1 L / min. Next, the temperature was raised to 225°C in 10 minutes while flowing hydrogen gas at a rate of 300 mL / min, and a sintering treatment was performed at 225°C for 60 minutes. After that, the glass substrate with the formed sintered body was cooled by flowing argon gas at a flow rate of 0.3 L / min, and the glass substrate was removed into the air at a temperature of 50°C or lower to obtain Sample 2.

[0191] The Young's modulus of the metal bodies in Sample 1 and Sample 2 described above was measured using the resonance method with a JE2-RT type measuring device manufactured by Nippon Techno Plus Co., Ltd., under the conditions of a temperature of 23°C and a resonance frequency of 278.4 Hz.

[0192]

[0193]

[0194]

[0195] As shown in Tables 1 and 3, the metal pastes of Preparation Examples 1, 2, and 19, which contain flattened silver particles, were found to be able to form sintered bodies with sufficiently low volume resistivity, and to have a lower Young's modulus compared to the metal pastes of Comparative Preparation Examples 1 to 3, in which the flattened silver particles were replaced with flattened copper particles.

[0196] [Fabrication of Conductive Via Silicon Substrates] (Examples 1-13 and Comparative Examples 1-3) Conductive via silicon substrates were fabricated using the following procedure.

[0197] <Preparation of Silicon Substrate> A silicon substrate was prepared with through-holes, and titanium, nickel, and copper layers were formed in that order on both main surfaces and on the walls of the through-holes. The silicon substrate had a diameter of 6 inches and a thickness of 300 μm, and the titanium, nickel, and copper layers were formed sequentially by sputtering, with through-holes of the hole diameters (via diameters) shown in the table.

[0198] <Preparation of Metal Particle Film> Using a screen printing machine, the metal paste prepared above was printed onto a 100 μm thick PET film in an 8-inch diameter (20 cm diameter circular shape) using a screen printing plate (wire diameter: 23 μm, mesh count: 400 lines, mesh opening: 41 μm, void ratio: 41 μm) to obtain a metal particle film with a metal particle-containing layer.

[0199] <Formation of conductive vias> Using a bonding device VJ-35 (manufactured by Ayumi Kogyo Co., Ltd.), a metal particle film was bonded to a silicon substrate from the metal particle-containing layer side. This laminate was then vacuum-pressed at room temperature and a pressure of 3 MPa to fill the through-holes with metal paste. At this time, the metal paste was made to protrude from the side of the silicon substrate opposite to the side to which the metal particle film was bonded.

[0200] Next, the PET film was peeled off the laminate and dried in air at 90°C for 10 minutes. The concentration (mass%) of metal particles in the metal paste before and after drying is shown in the table.

[0201] As shown in Figures 3(a) to 3(d), the metal paste on the main surface of the silicon substrate on the side to which the metal particle film was bonded was removed using a rubber squeegee, and then the metal paste protruding from the side of the silicon substrate opposite to the side to which the metal particle film was bonded was removed using a rubber squeegee.

[0202] Next, the silicon substrate on which conductive via precursors were formed in the through-holes by the process described above was placed in a tube furnace (manufactured by AVC Co., Ltd.), and the air inside the tube furnace was replaced with argon gas by flowing argon gas at a rate of 1 L / min. Then, the temperature was raised to 300°C in 10 minutes while flowing hydrogen gas at a rate of 300 mL / min, and the conductive via precursors were sintered by sintering at 300°C for 60 minutes. After that, the substrate was cooled by flowing argon gas at a flow rate of 0.3 L / min, and removed from the air at a temperature of 50°C or lower to obtain a silicon substrate with conductive vias.

[0203] <Evaluation of silicon substrates with conductive vias> The silicon substrates with conductive vias obtained above were evaluated according to the following method to determine the presence or absence of cracks and voids in the conductive vias, the porosity of the conductive vias, and the depressions after sintering.

[0204] (Presence or absence of cracks in conductive vias) The cross-sections of conductive vias on a silicon substrate with conductive vias were exposed by cross-sectional polishing, and 30 conductive vias were observed using a digital microscope (Keyence Corporation, product name: VHX-6000) to check for the presence or absence of cracks (length 10 μm or more).

[0205] (Presence or absence of voids in conductive vias) The cross-sections of conductive vias on a silicon substrate with conductive vias were exposed by cross-sectional polishing, and 30 conductive vias were observed using a digital microscope (Keyence Corporation, product name: VHX-6000) to check for the presence or absence of voids (diameter 5 μm or larger).

[0206] (Indentation after sintering) The cross-sections of conductive vias on a silicon substrate with conductive vias were exposed by cross-sectional polishing, and 30 conductive vias were observed using a digital microscope (Keyence Corporation, product name: VHX-6000). The average step height was calculated using the following method. [Average step height] An image of the cross-section passing through the center of the via was obtained, and the cross-sectional image was binarized to find the cross-sectional area Sb enclosed by the inner wall of the via, the exposed surface of the conductive via, and the opening surface of the via. This was divided by the spacing Wb of the inner walls of the holes to calculate the average step height (= Sb / Wb). The average value of the average step height of 30 locations was calculated, and the indentation after sintering was evaluated according to the following criteria. An evaluation of C or higher can be judged as good. (Criteria for judgment) A: Average value of average step height is less than 1 μm B: Average value of average step height is 1 μm or more and less than 3 μm C: Average value of average step height is 3 μm or more and less than 5 μm D: Average value of average step height is 5 μm or more and less than 10 μm E: Average value of average step height is 10 μm or more

[0207] (Porosity of Conductive Vias) A silicon substrate with conductive vias that had undergone mechanical polishing was cut in the thickness direction, and the cross-section of the central part of the conductive via in the silicon substrate was exposed using a focused ion beam, and this cross-section was observed. When observing the cross-section of the central part of the through-hole in the silicon substrate, the range observed was ±5 μm in the thickness direction of the silicon substrate and ±5 μm in the direction perpendicular to the thickness direction of the silicon substrate from the center of the through-hole. A focused ion beam processing observation device (Hitachi High-Technologies Corporation, product name: MI4050) was used. A scanning electron microscope (Hitachi High-Technologies Corporation, product name: S-3700N) was used for observation, with a magnification of 5000x, and a cross-sectional image of the conductor (approximately 10 μm square) was captured. Five observation points were selected. The obtained cross-sectional images were binarized using image analysis software (Adobe Photoshop® Elements) to separate the sintered copper portion from the porous (vacant) portion. For each of the five observation points, the ratio of the area of ​​the porous (vacant) portion to the total area of ​​the conductive via cross-section was calculated and defined as the porosity. The average of the porosities from the five observation points was defined as the porosity of the conductive via.

[0208] <Evaluation of the Wiring Board> A UV-curable etching resist dry film H-W425 (manufactured by Resonac Co., Ltd., product name) was pressed onto the surface of the conductive via-equipped silicon substrate obtained above using a laminator. Then, a photomask was placed over the surface and the wiring pattern was exposed to light, followed by resist development. Next, electroplating was performed on the resist openings, followed by peeling off the resist and etching the seed layer to form wiring with a wiring pattern of 300 μm × 600 μm, thereby obtaining a test piece 55 (wiring board) as shown in Figure 5. In the test piece 55, conductive vias formed in through holes are electrically connected by wiring provided on the substrate surface.

[0209] The test specimens obtained as described above were evaluated according to the following method for initial resistance, connection reliability, presence or absence of cracks in the substrate, and indentation of conductive vias after resist removal.

[0210] (Initial Resistance) The initial resistance of test piece 55 was measured by connecting a predetermined number of vias. The number of vias was set as follows according to the via diameter. Based on this connected resistance, the initial resistance was evaluated according to the following criteria. A rating of B or higher can be considered good. (Number of vias) 30 μmφ: 30 vias 50 μmφ: 25 vias 100 μmφ: 20 vias (Judgment Criteria) A: Resistance less than 10 mΩ B: Resistance 10 mΩ or more and less than 30 mΩ C: Resistance 30 mΩ or more and less than 100 mΩ D: Resistance 100 mΩ or more and less than 500 mΩ E: Resistance 500 mΩ or more

[0211] (Connection Reliability) Test specimen 55 was placed in a temperature cycle tester (TSA-72SE-W, manufactured by ESPEC Corporation), and a temperature cycle connection reliability test was conducted under the following conditions: low temperature side: -55°C, 15 minutes; room temperature: 2 minutes; high temperature side: 125°C, 15 minutes; defrost cycle: automatic; number of cycles: 50, 100, 300, 500, 1000, 2000 cycles. For each number of cycles, the resistance value of the connected vias, which were set according to the via diameter as described above, was measured for the test specimen. Based on this connected resistance value, the connection reliability was evaluated according to the following criteria. (Judgment Criteria) A: Resistance change rate is less than 1% of the initial resistance B: Resistance change rate is 1% or more but less than 3% of the initial resistance C: Resistance change rate is 3% or more but less than 5% of the initial resistance D: Resistance change rate is 5% or more but less than 10% of the initial resistance E: Resistance change rate is 10% or more but less than 20% of the initial resistance F: Resistance change rate is 20% or more of the initial resistance

[0212] (Cracks in the substrate) Test piece 55 was visually inspected to check for any cracks in the silicon substrate.

[0213] (Indentation after resist removal) In the preparation of test piece 55, after removing the resist, the cross-section of the conductive vias was exposed by cross-sectional polishing, and 30 conductive vias were observed using a digital microscope (Keyence Corporation, product name: VHX-6000), and the average value of the average step height was calculated in the same way as the evaluation of indentation after sintering described above. The indentation after resist removal was then evaluated according to the following criteria. A rating of C or higher can be considered good. (Criteria) A: Average value of average step height is less than 1 μm B: Average value of average step height is 1 μm or more and less than 3 μm C: Average value of average step height is 3 μm or more and less than 5 μm D: Average value of average step height is 5 μm or more and less than 10 μm E: Average value of average step height is 10 μm or more

[0214]

[0215]

[0216] As shown in Tables 4 and 5, when using the metal pastes of Preparation Examples 1, 2, and 19 containing flattened silver particles (Examples 4, 8, and 13), it was confirmed that the change in resistance value after reliability testing could be suppressed over a longer period compared to when using the metal pastes of Comparative Preparation Examples 1 to 3 in which the flattened silver particles were replaced with flattened copper particles (Comparative Examples 1, 2, and 3).

[0217] [Preparation of conductive via-equipped glass substrates] (Examples 14-22, Comparative Examples 4-6) Conductive via-equipped glass substrates were prepared using the following procedure.

[0218] <Preparation of glass substrate> A glass substrate "D263Teco" (manufactured by SCHOTT, product name, material: borosilicate glass, mean linear thermal expansion coefficient α: 7.2 × 10) is provided, which has through holes and has a titanium layer (thickness 100 nm) and a copper layer (thickness 300 nm) formed in that order on both main surfaces and on the walls of the through holes. －６ K －１ The following materials were prepared. The glass substrates had a diameter of 6 inches and thicknesses of 300, 500, and 1000 μm. The titanium and copper layers were formed sequentially by sputtering, and each substrate had through holes with a diameter (via diameter) of 90 μm.

[0219] Except for using the glass substrate described above, conductive via-equipped glass substrates and wiring substrates were obtained and evaluated in the same manner as the fabrication and evaluation of the conductive via-equipped silicon substrate described above.

[0220]

[0221] As shown in Table 6, it was confirmed that when using the metal pastes of Preparation Examples 1, 2, and 19 containing flattened silver particles (Examples 16, 19, and 22), the change in resistance value after reliability testing could be suppressed over a longer period compared to when using the metal pastes of Comparative Preparation Examples 1 to 3 in which the flattened silver particles were replaced with flattened copper particles (Comparative Examples 4, 5, and 6).

[0222] [Fabrication of Conductive Via-Attached Organic Substrates] (Examples 23-45, Comparative Examples 7-9) Conductive via-attached organic substrates were fabricated using the following procedure.

[0223] <Preparation of Organic Substrates> High Tg glass epoxy multilayer material MCL-E-679F(J) (manufactured by Resonac Co., Ltd.) with thicknesses of 300, 500, and 1000 μm, each with 1 μm copper foil laminated on both sides, was prepared, and through holes with a diameter (via diameter) of 100 μm were made. A copper plating film with a thickness of 0.5 μm was formed inside the vias by electroless copper plating.

[0224] Using the above-mentioned organic substrate, conductive via-equipped organic substrates and wiring substrates were obtained in the same manner as the above-described process for fabricating and evaluating conductive via-equipped silicon substrates, except that the temperature was raised to 225°C in 10 minutes and then sintered at 225°C for 60 minutes. These substrates were then evaluated. Regarding substrate cracking, evaluation was omitted because organic substrates are easily expanded and contracted and resistant to cracking.

[0225] (Example 46) An organic substrate with conductive vias was prepared in the same manner as in Example 25. Next, the surface of the organic substrate with conductive vias was coated with positive-type photosensitive resin AH-3000 (manufactured by Resonac Co., Ltd., product name) by spin coating at 1000 rpm / 5 seconds and 2000 rpm / 20 seconds to a thickness of approximately 5 μm on one side. After pre-drying at 120°C for 150 seconds, the opposite side was similarly treated by spin coating at 1000 rpm / 5 seconds and 2000 rpm / 20 seconds to a thickness of approximately 5 μm. The vacuum level was kept below 1000 Pa to promote the penetration of the conductive vias into the porous area. Pre-drying was performed at 120°C for 150 seconds. The entire surface of both sides of the substrate was exposed using a direct writing exposure machine "DE-1UH" (manufactured by Via Mechanics Co., Ltd., product number) under conditions of 500 mJ / cm2. Next, a 2.38% TMAH (developer) was used to treat the surface of the organic substrate at 30°C for 1 minute at a spray pressure of 0.17 MPa, completely removing the positive-type photosensitive resin composition layer formed on the surface. Subsequently, heat treatment was performed at 230°C for 60 minutes to cure the positive-type photosensitive resin composition (AH-3000) impregnated into the porous portion of the copper sintered body. Furthermore, oxygen plasma treatment was used to remove the remaining photosensitive resin composition and its cured residue from the surface of the copper sintered body.

[0226] A wiring board was obtained and evaluated in the same manner as the fabrication and evaluation of the conductive via-equipped silicon substrate described above.

[0227]

[0228]

[0229] As shown in Tables 7 and 8, it was confirmed that when using the metal pastes of Preparation Examples 1, 2, and 19 containing flattened silver particles (Examples 25, 28, and 45), the change in resistance value after reliability testing could be suppressed over a longer period compared to when using the metal pastes of Comparative Preparation Examples 1 to 3 in which the flattened silver particles were replaced with flattened copper particles (Comparative Examples 7, 8, and 9).

[0230] 1...Silicon wafer, 2...Metal coating, 3...Metal paste portion, 3b...Conductive via precursor, 3c...Conductive via, 3p...Metal particle-containing layer, 7...Support film, 8a...Etching resist, 9...Wiring, 30...Through hole, 31...Non-through hole, 40, 41...Silicon substrate, 42...Rubber squeegee, 50...Substrate with conductive vias, 52...Wiring substrate with conductive vias, 55...Test piece, A...Pressure jig.

Claims

1. A metal paste comprising metal particles and a volatile solvent, wherein the metal particles comprise silver particles and copper particles, the silver particles comprise flattened silver particles X with a volume average particle size of 0.8 μm or more, and the copper particles comprise copper particles Y with a volume average particle size of 0.5 μm or less.

2. The metal paste according to claim 1, wherein the content of the silver particles X is 5 to 40% by mass based on the total amount of metal particles.

3. The metal paste according to claim 1, wherein the content of the copper particles Y is 50% by mass or less based on the total amount of metal particles.

4. The specific surface area of ​​the copper particle Y is 3.3 m². ２ The metal paste according to claim 1, wherein the amount is less than or equal to / g.

5. A metal paste comprising metal particles and a volatile solvent, wherein the metal particles comprise metal particles A made of a metal with a Young's modulus of 5 to 99 GPa and metal particles B made of a metal with a Young's modulus of 100 to 250 GPa, wherein metal particles A comprises flattened metal particles X with a volume average particle size of 0.8 μm or more, and metal particles B comprises metal particles Y with a volume average particle size of 0.5 μm or less.

6. The metal paste according to claim 5, wherein the content of the metal particles X is 5 to 40% by mass based on the total amount of the metal particles.

7. The metal paste according to claim 5, wherein the content of the metal particles Y is 50% by mass or less based on the total amount of the metal particles.

8. The specific surface area of ​​the metal particle Y is 3.3 m². ２ The metal paste according to claim 5, wherein the amount is less than or equal to / g.

9. A method for manufacturing a conductive via substrate, comprising the steps of: preparing a substrate having holes, filling at least the inside of the holes with a metal paste according to any one of claims 1 to 8; and firing the metal paste, or the metal paste from which a portion of the volatile solvent has been removed.

10. A substrate with conductive vias, comprising a substrate having through holes and conductive vias provided within the through holes, wherein the conductive vias include a sintered body of metal paste according to any one of claims 1 to 8.

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