Method for manufacturing a substrate with conductive vias

Abstract

A method for manufacturing a substrate with conductive vias includes the steps of: (a) preparing a substrate having holes; and (b) providing a metal paste portion containing metal particles and a volatile solvent so as to fill the holes and cover at least the surface of the substrate around the holes; (b) heating the metal paste portion to remove part of the volatile solvent; (c) removing part of the heated metal paste portion so as to expose the surface, thereby forming a conductive via precursor containing metal particles and the remainder of the volatile solvent and having a flattened exposed surface inside the holes; and (d) firing the conductive via precursor, wherein the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, and the metal particle concentration of the metal paste portion provided in step (a) is 95.0 mass% or more, and the content of the second metal particles in the metal paste portion provided in step (a) is 50 mass% or less based on the total amount of metal particles. The above-described method for manufacturing a substrate with conductive vias is also useful as a technology for reducing the environmental load caused by plating.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a substrate with conductive vias, a metal paste, and a substrate with conductive vias. [Background technology]

[0002] In recent years, in order to miniaturize, enhance functionality, and integrate electronic devices and components, attention has been focused on three-dimensional packaging technology, which electrically connects silicon substrates arranged above and below via electrodes called through-silicon vias (TSVs) on silicon substrates and densely stacks semiconductor chips vertically (in the height direction).

[0003] As a method for forming a through electrode, for example, Patent Document 1 discloses a method for manufacturing a semiconductor device having a through-silicon electrode, which includes a step of electroplating a non-through via formed in a silicon substrate with copper using a specific copper plating solution. However, this method has problems in terms of productivity, such as the environmental impact of plating and the need to perform plating while suppressing the deposition rate of the copper film, which increases the working time.

[0004] Another known method is to fill a through-hole in a heat-resistant substrate with a copper conductor paste containing copper powder, glass powder, an organic vehicle, etc., and then bake it to form a copper conductor in the through-hole (for example, Patent Document 2 below). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-16712 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-108917 Summary of the Invention [Problem to be solved by the invention]

[0006] Recently, as silicon substrates have been reduced in size to accommodate the miniaturization of electronic devices and components, the inner diameters of through holes have also been reduced to a minimum, making it necessary to form conductive vias with sufficient conductivity even within such through holes. Furthermore, wiring may be further provided on the surface of the substrate on which the conductive vias are formed by plating or the like, and even in this case, a sufficiently low connection resistance value is required.

[0007] Furthermore, recent advances in signal speeds, board miniaturization, and reduced power consumption due to shorter transmission distances have created demands for even greater connection reliability. Under these circumstances, a substrate with conductive vias (wiring substrate) on which the above-mentioned wiring is formed is required to have not only excellent conductivity, but also excellent properties such that connection resistance is less likely to increase even when subjected to temperature changes (hereinafter also referred to as "connection reliability").

[0008] Therefore, the present invention aims to provide a method for manufacturing a substrate with conductive vias that can exhibit a sufficiently low connection resistance even after wiring formation and that allows the resulting wiring substrate to have excellent connection reliability, and a metal paste that can be used in this method. [Means for solving the problem]

[0009] As a result of extensive research to achieve the above-mentioned object, the inventors of the present invention have found that the cause of high connection resistance after wiring formation is low flatness (or smoothness) of the conductive vias on the surface of the substrate with conductive vias (in other words, a large step between the conductive via portion and the substrate surface). Based on this finding, the inventors have investigated methods for reducing the step, and have found that by forming conductive vias through a specific process using a metal paste containing specific metal particles and a volatile solvent, a sufficiently low connection resistance can be obtained even when wiring connected to the conductive vias is further formed, and that the resulting wiring substrate has excellent connection reliability, which has led to the completion of the present invention.

[0010] That is, one aspect of the present invention relates to the following method for manufacturing a substrate with conductive vias. [1] A method for manufacturing a substrate with conductive vias, comprising: step (a) of preparing a substrate having holes, and providing a metal paste portion containing metal particles and a volatile solvent so as to fill the holes and cover at least the surface of the substrate around the holes; step (b) of heating the metal paste portion to remove a portion of the volatile solvent; step (c) of removing a portion of the metal paste portion after heating to expose the surface, thereby forming a conductive via precursor containing the metal particles and the remainder of the volatile solvent and having a flattened exposed surface inside the holes; and step (d) of firing the conductive via precursor, wherein the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, the metal paste portion provided in step (a) has a metal particle concentration of 95.0 mass % or more, and the content of the second metal particles in the metal paste portion provided in step (a) is 50 mass % or less based on the total amount of the metal particles.

[0011] According to the above manufacturing method, in step a, a metal paste portion containing a volatile solvent and having the above-mentioned specific metal particle configuration is provided, and then steps b and c are carried out, thereby achieving both good filling of the interior of the hole and the formation of a conductive via precursor that is resistant to volumetric shrinkage upon firing, and step d makes it possible to form a conductive via with excellent conductivity and with sufficiently suppressed occurrence of cracks and voids, while sufficiently reducing the step with the substrate surface. This makes it possible to obtain a substrate with conductive vias that exhibits sufficiently low connection resistance even after wiring formation, and furthermore, the substrate with conductive vias (wiring substrate) on which wiring is formed can have excellent connection reliability.

[0012] [2] The method for manufacturing a substrate with conductive vias according to [1], wherein the first metal particles and the second metal particles are copper particles. [3] The method for manufacturing a substrate with conductive vias according to [1] or [2], wherein the first metal particles include flaky copper particles.

[0013] Another aspect of the present invention relates to the following metal paste. [4] A metal paste containing metal particles and a volatile solvent, wherein the content of the metal particles is 95.0 mass% or more based on the total amount of the metal paste, the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, and the content of the second metal particles is 50 mass% or less based on the total amount of the metal particles. [5] The metal paste according to [4], wherein the first metal particles and the second metal particles are copper particles. [6] The metal paste according to [4] or [5], wherein the first metal particles include flaky copper particles.

[0014] The above metal paste has sufficient printability, and the metal paste portion can be efficiently formed in the above method for manufacturing a substrate with conductive vias.

[0015] Another aspect of the present invention relates to the following substrate with conductive vias. [7] A substrate with conductive vias, comprising a substrate having a through hole and a conductive via provided in the through hole, wherein the conductive via comprises a sintered body of the metal paste described in any one of [4] to [6]. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a method for manufacturing a substrate with conductive vias that can exhibit a sufficiently low connection resistance value even after wiring formation and that allows the resulting wiring board to have excellent connection reliability, a metal paste that can be used in the method, and a substrate with conductive vias. [Brief explanation of the drawings]

[0017] [Figure 1] 5A to 5C are schematic diagrams showing an example of a method for manufacturing a substrate with conductive vias according to the present embodiment. [Figure 2] 5A to 5C are schematic diagrams showing an example of a method for manufacturing a substrate with conductive vias according to the present embodiment. [Figure 3] 5A to 5C are schematic diagrams showing an example of a method for manufacturing a substrate with conductive vias according to the present embodiment. [Figure 4] 1A to 1C are schematic diagrams showing an example of a method for forming wiring. [Figure 5] FIG. 1 is a schematic diagram showing a test piece. [Figure 6] 1 is a cross-sectional photograph of a conductive via in a silicon substrate with a conductive via produced in Example 1. [Figure 7] 1 is a cross-sectional photograph of a conductive via in a silicon substrate with a conductive via produced in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments. In the drawings, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be omitted.

[0019] <Metal paste> The metal paste of this embodiment contains metal particles and a volatile solvent, and the metal particle content is 95.0 mass% or more based on the total amount of the metal paste. The metal paste of this embodiment can be used to form a metal paste portion in a manufacturing method of a substrate with conductive vias, which will be described later.

[0020] The content of metal particles in the metal paste of this embodiment may be 95.2 mass% or more, 95.5 mass% or more, 95.7 mass% or more, or 96 mass% or more, based on the total amount of the metal paste, and may be 98 mass% or less, 97 mass% or less, or 96.5 mass% or less, or may be 95.0 to 98 mass%, 95.2 to 97 mass%, or 95.7 to 96.5 mass%.

[0021] [Metal particles] Examples of metal particles include nickel, silver, copper, gold, palladium, platinum, and solder particles. The metal particles may contain multiple 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 is resistant to increases in resistance even when subjected to temperature changes, and a substrate having through electrodes that have sufficient conductivity and excellent connection reliability. In this embodiment, the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less.

[0022] In this specification, the volume average particle size of particles (hereinafter sometimes referred to as "average particle size") refers to the 50% volume average particle size (D50). The volume average particle size of metal particles can be determined by, for example, dispersing raw metal particles in a dispersion medium such as water or alcohol and measuring the dispersion using a laser diffraction / scattering particle size distribution analyzer.

[0023] The first metal particles and the second metal particles may be copper particles from the viewpoints of reducing resistance, ensuring ion migration resistance, and facilitating wiring formation. This embodiment will be described in detail using as an example a case where the first metal particles are copper particles (hereinafter referred to as "first copper particles") and the second metal particles are copper particles (hereinafter referred to as "second copper particles").

[0024] (First copper particles) The average particle size of the first copper particles 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 within holes (e.g., through holes or non-through holes) of the substrate and suppressing the occurrence of voids and cracks within the holes; for example, from the viewpoint of suppressing particle clogging in microvias with an inner diameter of 100 μm or less and improving filling properties, 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 suppressing voids and cracks and suppressing particle clogging in microvias, the average particle size 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 diameter DC1 of the first copper particles to the inner diameter DH of the hole may be 0.01 or more, 0.03 or more, or 0.04 or more from the viewpoint of suppressing particle clogging in the microvias and improving filling, and may be 0.15 or less, 0.1 or less, or 0.05 or less from the viewpoint of suppressing voids and cracks by reducing shrinkage due to firing. Moreover, from the above viewpoint, the ratio (DC1 / DH) may be 0.01 to 0.15, or 0.03 to 0.1.

[0025] The shape of the first copper particles may be, for example, spherical, blocky, needle-like, flat (flake-like), or approximately spherical. The first metal particles may be aggregates of copper particles having these shapes. The metal paste of this embodiment may contain spherical copper particles as the first copper particles, from the viewpoint of reducing the step between the conductive via portion to be formed and the substrate surface and suppressing fluctuations in connection resistance even after a reliability test (e.g., a temperature cycle test).

[0026] From the viewpoint of improving the printability of the metal paste, the first copper particles may contain particles such as spherical particles having an aspect ratio of 2 or less in an amount of 40% by mass or more, 50% by mass or more, 60% by mass or more, 80% by mass or more, or 100% by mass, or may be 40 to 90% by mass, 50 to 80% by mass, or 60 to 70% by mass. The aspect ratio (major axis / minor axis) of the particles can be determined, for example, by observing an SEM image of the particles and measuring the major axis and minor axis (e.g., thickness).

[0027] The metal paste of this embodiment may contain flaky copper particles as the first copper particles in order to reduce shrinkage due to firing and thereby suppress voids and cracks, or may contain spherical copper particles and flaky copper particles in order to reduce the viscosity of the metal paste, improve filling of microvias, and reduce shrinkage due to firing and thereby suppress voids and cracks. When spherical copper particles and flaky copper particles are used in combination, the mass ratio thereof (spherical copper particles) / (flaky copper particles) may be 1 to 9, 1.2 to 2.5, or 1.4 to 4.

[0028] The flaky copper particles may have an aspect ratio of 1.5 or more, 2 or more, or 3 or more.

[0029] When spherical copper particles having an aspect ratio of 2 or less and flaky copper particles having an aspect ratio of more than 2 are used in combination, the mass ratio thereof (spherical copper particles) / (flaky copper particles) may be 0.6 to 9, 1.0 to 4.0, or 1.5 to 2.4.

[0030] The first copper particles may be produced by a chemical reduction method, an atomization method, an electrolysis method, a pulverization method, a plasma rotating electrode method, a uniform liquid spray method, a heat treatment method, or the like, 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.

[0031] The first copper particles may contain wet-processed copper powder. In this case, conductive vias with excellent conductivity are more likely to be obtained. This effect is believed to be achieved by the wet-processed copper powder's ability to easily bond with the copper particles blended as the second metal. The wet-processed copper powder may have a D90 / D50 ratio of 1.5 or less.

[0032] The copper particles may also contain wet-processed copper powder and atomized copper powder. This improves the printability of the metal paste and reduces the step between the formed conductive via and the substrate surface, facilitating suppression of fluctuations in connection resistance even after reliability tests (e.g., temperature cycle tests). The reason for this effect is believed to be as follows: The coexistence of wet-processed copper powder, which is easily bonded to the second copper particles and has a uniform particle size, and atomized copper powder, which has a wide particle size distribution, allows the wet-processed copper powder to bond between the atomized copper powder particles while also bonding to the second copper particles. This results in the formation of a strong sintered body due to a close-packed structure, and suppresses shrinkage during sintering, thereby suppressing the occurrence of voids, cracks, and depressions. The atomized copper powder may have a D90 / D50 ratio of 1.6 or more, 1.7 or more, or 1.8 or more.

[0033] When the first copper particles contain wet copper powder and atomized copper powder, the content of the wet copper powder may be more than 0 parts by mass and less than 100 parts by mass, or may be 20 to 80 parts by mass, relative to 100 parts by mass of the total amount of the wet copper powder and atomized copper powder.

[0034] The first copper particles may be commercially available. Examples of commercially available first copper particles include 1050Y (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 0.81 μm, D90: 1.1 μm, spherical, wet-process copper powder), 1100Y (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 1.1 μm, D90: 1.6 μm, spherical, wet-process copper powder), 1200Y (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 2.1 μm, D90: 3.1 μm, spherical, wet-process copper powder), 1300Y (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 3.5 μm, D90: 5 μm, spherical, wet-process copper powder), and 1100YP (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): Examples of such copper powders include 1.4 μm, D90: 2.3 μm, flat, wet-process copper powder), 1200YP (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 3.1 μm, D90: 5.3 μm, flat, wet-process copper powder), MA-C02K (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 1.8 μm, D90: 3.6 μm, spherical, atomized copper powder), MA-C025K (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 2.4 μm, D90: 5.2 μm, spherical, atomized copper powder), and MA-C03K (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 3.4 μm, D90: 6.3 μm, spherical, atomized copper powder).

[0035] The first copper particles may be treated with a surface treatment agent from the viewpoints of dispersion stability and oxidation resistance. The surface treatment agent may be one that is removed during wiring formation (sintering of the copper particles). 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 decanenitrile; silane coupling agents such as alkylalkoxysilanes; and polymer 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.

[0036] The amount of the surface treatment agent may be an amount equivalent to one molecular layer or more on the particle surface. The amount of the surface treatment agent varies depending on the specific surface area of the first copper particles, the molecular weight of the surface treatment agent, and the minimum coverage area of the surface treatment agent. The amount of the surface treatment agent is usually 0.001% by mass or more.

[0037] The amount of the surface treatment agent is determined by the ratio of the number of molecular layers (n) attached to the surface of the first copper particles to the specific surface area (A p ) (unit: m 2 / g) and the molecular weight of the surface treatment agent (M s ) (unit: g / mol) and the minimum coverage area of the surface treatment agent (S S ) (unit: m 2 / unit) and Avogadro's number (N A )(6.02×10 23 Specifically, the amount of surface treatment agent can be calculated from the following formula: Treatment amount of surface treatment agent (mass%) = {(n × A p ×M s ) / (S S ×N A +n×A p ×M s)}×100%.

[0038] The specific surface area of the first copper particles can be calculated by measuring the dried copper particles using a BET specific surface area measurement method. The minimum coverage area of the surface treatment agent is 2.05 × 10 when the surface treatment agent is a linear saturated fatty acid. -19 m 2 The carbon content of the surface treatment agent is 1 / molecule. For other surface treatment agents, measurement can be performed, for example, by calculation using a molecular model or by the method described in "Chemistry and Education" (Kamieda Katsuhiro, Inafuku Sumio, Mori Iwao, 40(2), 1992, pp. 114-117). Here is an example of a method for quantifying the surface treatment agent. The surface treatment agent can be identified by thermal desorption gas chromatography-mass spectrometry of the dried powder obtained by removing the dispersant from the metal paste, thereby determining the carbon number and molecular weight of the surface treatment agent. The carbon content of the surface treatment agent can be analyzed by carbon content analysis. Examples of carbon content analysis methods include high-frequency induction heating furnace combustion / infrared absorption. The amount of the surface treatment agent can be calculated using the above formula from the carbon number, molecular weight, and carbon content of the identified surface treatment agent.

[0039] (Second copper particles) The average particle size of the second copper particles may be 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, or 0.2 μm or less from the viewpoint of sinterability; it may be 0.01 μm or more, 0.03 μm or more, 0.05 μm or more, 0.08 μm or more, or 0.1 μm or more from the viewpoint of reducing synthesis costs, achieving good dispersibility, and reducing the amount of surface treatment agent used; and it may be 0.1 μm to 0.3 μm, 0.12 μm to 0.28 μm, or 0.15 μm to 0.25 μm from the viewpoint of achieving low-temperature sinterability and good dispersibility in the paste.

[0040] The second copper particles can act as copper particles that suitably bond the first copper particles together. Furthermore, the second copper particles have superior sinterability to the first copper particles and can promote sintering of the copper particles. For example, the copper particles can be sintered at a lower temperature than when the first copper particles are used alone.

[0041] The second copper particles may be wet copper powder produced by a chemical reduction method.

[0042] The shape of the second copper particles may be, for example, spherical, blocky, needle-like, flat (flake-like), or approximately spherical. The second copper particles may also be an aggregate of copper particles having any of these shapes. From the viewpoints of dispersibility and packing ability, the shape of the second copper particles may be spherical, approximately spherical, or flat (flake-like), and from the viewpoints of combustibility and mixability with the first copper particles, the shape may be spherical or approximately spherical.

[0043] The aspect ratio of the second copper particles may be 5 or less, 4 or less, or 3 or less, from the viewpoints of dispersibility, packing property, and mixability with the first copper particles.

[0044] The second copper particles may be synthesized or commercially available. Examples of commercially available second copper particles include CH0200L1 (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 200 nm, spherical) and Tn-Cu100 (manufactured by Taiyo Nippon Sanso Co., Ltd., average particle size (D50): 120 nm, spherical).

[0045] The second copper particles may be treated with a specific surface treatment agent. Examples of the specific surface treatment agent include organic acids having 8 to 16 carbon atoms. Examples of 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, methyl dodecanoic acid, ethyl undecanoic acid, propyl decanoic acid, butyl nonanoic acid, pentyl octanoic acid, myristic acid, methyl tridecanoic acid, ethyl dodecanoic acid, propyl undecanoic acid, butyl decanoic acid, pentyl nonanoic acid, hexyl octanoic acid, pentadecanoic acid, methyl tetradecanoic acid, ethyl tridecanoic acid, propyl dodecanoic acid, butyl undecanoic acid, pentyl decanoic acid, hexyl nonanoic acid, palmitic acid, methyl pentadecanoic acid, ethyl tetradecanoic acid, propyl tridecanoic acid, butyl dodecanoic acid, pentyl undecanoic acid, hexyl decanoic acid, heptyl nonanoic acid, methyl cyclohexane carboxylic acid, ethyl cyclohexane carboxylic acid, propyl cyclohexane carboxylic acid, butyl cyclohexane carboxylic acid, pentyl cyclohexane carboxylic acid, hexyl cyclohexane carboxylic acid, heptyl cyclohexane carboxylic acid, octyl cyclohexane carboxylic acid, and nonyl cyclohexane carboxylic acid; octene Examples of the organic acid include unsaturated fatty acids such as nonenoic acid, methylnonenoic acid, 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. One organic acid may be used alone, or two or more organic acids may be used in combination.By combining such an organic acid with the second copper particles, it tends to be possible to achieve both the dispersibility of the second copper particles and the elimination of the organic acid during sintering.

[0046] The amount of the surface treatment agent may be an amount sufficient to adhere to the surface of the second copper particles in a monolayer to trilayer form. The amount of the surface treatment agent 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. The amount of the surface treatment agent on the second copper particles can be calculated by the method described above for the first copper particles. The same applies to the specific surface area, the molecular weight of the surface treatment agent, and the minimum coverage area of the surface treatment agent.

[0047] The content of the second metal particles in the metal paste is 50 mass% or less based on the total amount of metal particles from the viewpoint of connection reliability, and may be 10 to 50 mass%, or 20 to 40 mass%, from the viewpoint of lowering the sintering temperature to improve adhesion to the base metal layer, reducing the porosity of the sintered body, suppressing shrinkage during sintering, and suppressing the occurrence of cracks.

[0048] The total content of the first copper particles and the second copper particles in the metal paste may be 100 parts by mass, 85 to 99.5 parts by mass, 90 to 99 parts by mass, or 95 to 98 parts by mass, when the total mass of the metal particles is 100 parts by mass.

[0049] The contents of the first copper particles and the second copper particles 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, relative to 100 parts by mass of the total of the first copper particles and the second copper particles.

[0050] The metal paste of this embodiment may contain copper particles and metal particles other than copper particles (hereinafter also referred to as "other metal particles"). In this case, the other metal particles may be nickel particles, silver particles, gold particles, palladium particles, platinum particles, or solder particles. One or more of these may be contained. 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.

[0051] The content of the 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 the copper particles is 100 parts by mass. The metal paste of this embodiment may not include solder particles as the other metal particles.

[0052] [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 (e.g., 1,3-butanediol), 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 (e.g., diethylene glycol mono-n-butyl ether), diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, and propylene glycol propyl 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 an alkyl group having 1 to 18 carbon atoms; and mercaptans having a cycloalkyl group having 5 to 7 carbon atoms.Examples of mercaptans having an alkyl group having 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan, and dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan. One type of volatile solvent may be used alone, or two or more types may be used in combination.

[0053] The metal paste of this embodiment may contain a solvent having a vapor pressure of 4 Pa or more and 30 Pa or less at 20° C. (hereinafter also referred to as a "high vapor pressure solvent") as a volatile solvent from the viewpoints of printability and suppressing volumetric shrinkage before and after firing the conductive via precursor (for example, between step C of forming the conductive via precursor and step d of firing the conductive via precursor) to suppress voids and cracks. One type of high vapor pressure solvent may be used alone, or two or more types may be used in combination.

[0054] Examples of high vapor pressure solvents include α-terpineol, 1,3-butanediol, ethyl carbitol, and propylene glycol diacetate.

[0055] The metal paste of this embodiment may contain a solvent having a vapor pressure of less than 4 Pa at 20°C (hereinafter also referred to as a "low vapor pressure solvent") as a volatile solvent, from the viewpoint of suppressing powdering due to drying accompanying solvent volatilization 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.

[0056] Low vapor pressure solvents include isobornylcyclohexanol (MTPH), dimethyl phthalate, and diethylene glycol mono-n-butyl ether.

[0057] From the viewpoint of achieving both printability and suppressing volume shrinkage before and after firing the conductive via precursor (for example, between step C of forming the conductive via precursor and step d of firing the conductive via precursor) to suppress 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 each be used alone or in combination of two or more. The content ratio of the high vapor pressure solvent and the low vapor pressure solvent may be 20 / 80 to 80 / 20 or 30 / 70 to 70 / 30 in mass ratio [high vapor pressure solvent / low vapor pressure solvent].

[0058] The content of the volatile solvent in the metal paste of this embodiment may be 2 mass% or more, 3 mass% or more, or 3.5 mass% or more, based on the total mass of the metal paste, and may be 5 mass% or less, 4.8 mass% or less, 4.5 mass% or less, 4.3 mass% or less, or 4 mass% or less, or may be 2 to 5 mass%, 3 to 4.8 mass%, or 3.5 to 4.5 mass%.

[0059] The metal paste of this embodiment may contain a resin component such as an epoxy resin. The metal paste of this embodiment may have a resin component content of 10% by mass or less, or 5% by mass or less, or may not contain a resin component.

[0060] The metal paste can be prepared by mixing metal particles such as the copper particles and optional components (additives, etc.) with the volatile solvent. After mixing the components, stirring may be performed. The maximum particle size of the dispersion may be adjusted by classification. Furthermore, the components can be mixed using a three-roll mill, kneader, planetary mixer, or other means.

[0061] When the metal paste contains the first copper particles and the second copper particles, the second copper particles, the surface treatment agent, and the dispersion medium may be mixed in advance, followed by a dispersion treatment to prepare a dispersion of the second copper particles, and then the first copper particles, and optionally other metal particles and optional additives, may be mixed therewith. This procedure improves the dispersibility of the second copper particles, improving their mixability with the first copper particles and further improving the performance of the metal paste. The dispersion of the second copper particles may be subjected to a classification operation to remove aggregates.

[0062] From the viewpoint of printability, the viscosity of the metal paste of this embodiment may be 100 to 600 Pa·s, or 150 to 400 Pa·s at 25°C. The viscosity of the metal paste is measured using a micro spiral viscometer PCU-02V (manufactured by Malcom Co., Ltd.) at a rotation speed of 10 rpm and a temperature of 25°C.

[0063] <Method of manufacturing a substrate with conductive vias> The method for manufacturing a substrate with conductive vias of this embodiment includes the steps of: (a) preparing a substrate having holes formed therein; and (b) 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; (b) heating the metal paste portion to remove some of the volatile solvent; (c) removing some of the metal paste portion after heating to expose the surface, thereby forming a conductive via precursor containing metal particles and the remainder of the volatile solvent and having a flattened exposed surface inside the holes; and (d) firing the conductive via precursor to form conductive vias, wherein the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, and the metal particle concentration of the metal paste portion provided in step (a) is 95.0 mass% or more, and the content of the second metal particles in the metal paste portion provided in step (a) is 50 mass% or less based on the total amount of metal particles.

[0064] 1 to 3 are schematic diagrams showing an example of a method for manufacturing a substrate with conductive vias according to this embodiment. Fig. 1 shows an example of a substrate used in the method for manufacturing a substrate with conductive vias. Hereinafter, the method for manufacturing a substrate with conductive vias according to this embodiment will be described with reference to these drawings. Note that this embodiment illustrates a case where the metal paste contains the above-mentioned copper particles as metal particles, and therefore the copper particles, copper layer, and copper sintered body can be read as metal particles, metal layer, and metal sintered body, respectively.

[0065] [Step a] Examples of substrates with holes prepared in this process include organic substrates, silicon substrates, glass substrates, ceramic substrates, printed wiring boards, and semiconductor package substrates. 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 blind holes. In this embodiment, for example, as shown in FIG. 1(a), a silicon substrate 40 can be prepared, which includes a silicon wafer 1 with through-holes 30 and a metal coating 2 formed on the wall surfaces of the through-holes and on the surface of the silicon wafer 1. The through-holes 30 communicate with both main surfaces of the silicon substrate 40. While the following description will be given using an example in which conductive vias are formed in this silicon substrate 40, the silicon wafer may be replaced with another insulating substrate in the description below.

[0066] 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 warpage 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 increasing the density of the substrate. Furthermore, when a polycrystalline silicon substrate or the like is used, the thickness may be 0.05 to 2 mm, 0.1 mm to 1.5 mm, or 0.2 to 1 mm.

[0067] The upper limit of the 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 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.

[0068] The ratio of the depth to the hole diameter of the through-holes 30 [(depth) / (hole diameter)] may be 0.5-40, 1-20, or 2-10.

[0069] The number of through holes 30 provided in the silicon substrate 40 is set to 1 / cm 2 of the main surface of the substrate from the viewpoint of increasing the density of the semiconductor device to be obtained. 2 The number of particles per molecule may be 100 or more, 200 or more, or 300 or more.

[0070] The metal coating 2 may be provided on both main surfaces of the silicon wafer 1 and on the wall surfaces of the through holes 30, or on at least one main surface of the silicon wafer 1 and on the wall surfaces of the through holes 30, or may be provided only on the wall surfaces of the through holes 30, or may not be provided at all. In the embodiment shown in Figure 1 (a), a silicon substrate 40 has metal coatings 2 on both main surfaces of the silicon wafer 1 and on the wall surfaces of the through holes 30.

[0071] Examples of the metal coating 2 include titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold. From the viewpoint of adhesion, the metal coating 2 is preferably a coating in which titanium, nickel, and copper are layered in this order. Adhesion is improved by oxidizing the surface of the silicon wafer 1 to form silicon oxide and then forming a titanium layer on the silicon oxide. Furthermore, by providing a nickel layer on the titanium layer and then providing a copper layer on that, diffusion of copper into the silicon wafer 1 can be suppressed compared to when a copper layer is provided directly on the titanium layer. Furthermore, providing a copper layer on the surface improves adhesion between the copper layer and copper particles in the metal paste, thereby improving reliability.

[0072] 1(b), when preparing a silicon substrate 41 having non-through holes 31 as holes, conductive vias serving as through electrodes can be formed by grinding the side of the silicon substrate opposite to the side on which the non-through holes 31 are formed after step a, step b, step c, or step d. Grinding methods include, for example, mechanical polishing and chemical mechanical polishing.

[0073] 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 pre-coated with the metal paste and pressing it onto the substrate. In the former method, examples of the method 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 combinations of these printing methods, spin coating, dipping, rolling, squeegeeing, and pressing. Among these methods, the screen printing and squeegee methods, which apply the paste directly to the substrate in a vacuum atmosphere, and the vacuum pressing method, which presses a film pre-coated with the metal paste in a vacuum atmosphere, are preferred.

[0074] In the latter method, as shown in Figures 2(a) to 2(c), the metal paste portion 3 can be provided, for example, by preparing a metal particle film on a support film 7, in which a metal particle-containing layer 3p made of the metal paste of this embodiment described above is provided, and then pressing this metal particle film against a substrate.

[0075] Examples of the support film 7 include a polyimide film, a polyethylene naphthalate film, and a 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 in forming the metal particle-containing layer by coating.

[0076] 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 easily ensuring sufficient filling of the 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.

[0077] From the viewpoint of suppressing the generation of voids in the through holes or non-through holes, the metal particle-containing layer may have a waviness (height difference) of 20 μm or less on the surface opposite the support film, or may have a waviness (height difference) of 10 μm or less. By reducing the waviness (height difference), when the metal particle film is pressed to fill the holes in the substrate with the metal particle composition, it becomes easier to simultaneously fill the numerous through holes or non-through holes present in the substrate, and it becomes 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 are partially generated. The waviness (height difference) can be evaluated by a non-contact method using a laser displacement meter or the like.

[0078] The above-mentioned metal particle film can be produced by applying the metal paste of the present embodiment described above onto a support film to form a metal particle-containing layer having a metal particle concentration of 95.0 mass % or more, or by applying a metal paste with an increased volatile solvent content (for example, an increased amount so that the metal particle concentration is less than 94.0 mass %) and drying the applied film to form a metal particle-containing layer having a metal particle concentration of 95.0 mass % or more.

[0079] Examples of methods for applying the metal paste include screen printing, transfer printing, offset printing, jet printing, and methods using a dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, bar coating, applicator, particle deposition method, spray coater, spin coater, dip coater, etc.

[0080] From the viewpoint of ease of application and uniformity of the applied film thickness, the metal paste can be applied onto the support film by screen printing.

[0081] 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.

[0082] The step of drying the coating film to form the metal particle-containing layer can be carried out at room temperature or at a temperature of room temperature to 100° C. or lower, and the atmosphere may be air or nitrogen.

[0083] In step a, the metal particle film described above is pressed against the silicon substrate 40 so that the metal particle-containing layer 3p of the metal particle film contacts the silicon substrate 40, and the through-holes 30 of the silicon substrate 40 are filled with a metal paste. In this case, for example, as shown in FIG. 2(b), the metal particle film and the silicon substrate 40 can be sandwiched and pressed from above and below by a pressing jig A. The pressing jig A is not particularly limited, but may be a commercially available one, or may be fabricated using a metal member having a flat portion. For example, a pressing jig having two or more of the above-mentioned metal members can press the metal particle film against the silicon substrate by sandwiching the metal particle film and the silicon substrate between the metal members arranged with their flat portions facing each other. The pressing 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 adjusting means. In this embodiment, a vacuum pressing method in which pressing is performed in a vacuum atmosphere may be used.

[0084] The pressing conditions may be, for example, a temperature of room temperature to 50°C or lower, 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 lower, or a vacuum of 200 Pa or lower. The pressure of the pressing jig when pressing the metal particle film onto the silicon substrate may be any pressure within a range that does not crack the silicon wafer, and may be, for example, 0.01 MPa or higher, 0.1 MPa or higher, or 1 MPa or higher.

[0085] The metal paste portion 3 may be any portion that fills the inside of the hole and covers at least the surface of the substrate around the hole, but as shown in Figures 2(b) and (c), the metal paste portion may protrude from the opening of the through hole (VP0 in Figure 2(a)) located on the opposite side of the substrate from the side where the metal particle film is pressed, covering the surface around the hole.

[0086] [Step b] In this process, the metal paste portion is heated to remove a portion of the volatile solvent, i.e., the metal paste portion is heated so that a portion of the volatile solvent remains. Note that, when using the above-mentioned metal particle film, the metal paste portion can be heated after peeling off the support film.

[0087] For heating, for example, a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, a steam heating furnace, a hot plate press device, etc. can be used.

[0088] The heating atmosphere may be air, an oxygen-free atmosphere such as nitrogen and rare gas, or a reducing atmosphere such as hydrogen and formic acid. When heated in air, copper particles are prone to oxidation when the heating temperature exceeds 100°C. However, if the metal paste portion contains the high vapor pressure solvent described above as a volatile solvent, part of the volatile solvent can be removed at temperatures below 100°C, 95°C or less, or 90°C or less. Note that if the metal paste portion does not contain a high vapor pressure solvent as a volatile solvent, for example, if it contains only the low vapor pressure solvent described above, heating in an oxygen-free or reducing atmosphere at 110°C or higher, 130°C or higher, or 150°C or higher can suppress oxidation of the copper particles while removing part of the volatile solvent.

[0089] When the metal paste portion contains a high vapor pressure solvent, the heating temperature may be 70°C or higher but lower than 100°C, or 80°C or higher but lower than 95°C, from the viewpoint of suppressing oxidation of the copper particles, and the heating time may be 5 to 60 minutes, or 10 to 30 minutes, from the viewpoint of suppressing oxidation of the copper particles.

[0090] Furthermore, in order to suppress volumetric shrinkage before and after firing the conductive via precursor (for example, between step C of forming the conductive via precursor and step d of firing the conductive via precursor) and to suppress voids and cracks, heating may be performed so that the concentration of metal particles in the metal paste portion becomes 96 mass % or more, 97.5 mass % or more, or 98 mass % or more.

[0091] [Process c] In this step, as shown in (a) to (d) of Figure 3, the metal paste portion 3a after heating obtained in step b is subjected to planarization (or smoothing) of the metal paste filled in the hole while removing the metal paste covering the surface of the substrate. As a result, a conductive via precursor 3b having a planarized exposed surface VP1 and containing metal particles and the remainder of the volatile solvent can be formed inside the hole (through hole 30) ((d) of Figure 3).

[0092] The metal paste portion can be removed using a rubber squeegee 42, as shown in Figures 3(b) and 3(d). This allows a portion of the metal paste portion (the metal paste covering the surface of the substrate and the metal paste protruding from the holes) to be removed so that the surface SP0 of the substrate 40 and the exposed surface VP1 of the conductive via precursor 3b are flush with each other. Another method is removal using a metal squeegee made of stainless steel or the like.

[0093] The step between the surface SP0 of the substrate 40 and the exposed surface VP1 of the conductive via precursor 3b may be 5 μm or less, or may be 3 μm or less, in the direction perpendicular to the substrate surface. Also, the average step calculated by the following method may be within the above range. (average step height) An image of a cross section passing through the center of the hole (via) is obtained and binarized to determine 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 is calculated by dividing this by the spacing Wa of the inner walls of the hole.

[0094] [Step d] In this step, the conductive via precursor 3b formed in step c is fired. This allows the formation of a conductive via 3c made of a metal body. The metal body may include a copper sintered 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 penetration of chemicals into the copper sintered body when immersed in a chemical solution such as a resist stripper or a plating pretreatment solution in a subsequent step and improving reliability. When the conductive via is made of a copper sintered body, the porosity of the copper sintered body may be in the above-mentioned range. The porosity can be determined by the method described in the Examples.

[0095] The firing can be carried out by a heating treatment, which can be performed using a heating means such as a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, or a steam heating furnace.

[0096] The firing atmosphere may be an oxygen-free atmosphere to suppress oxidation of the copper sintered body, or a reducing atmosphere to remove surface oxides of the copper particles in the conductive via precursor. Examples of oxygen-free atmospheres include the introduction of oxygen-free gases such as nitrogen or rare gases, or a vacuum. Examples of reducing atmospheres include pure hydrogen gas, a mixed gas of hydrogen and nitrogen such as forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and rare gas, or a rare gas containing formic acid gas. When the conductive via precursor is sintered by heating without pressure, pure hydrogen gas or a mixed gas of hydrogen and nitrogen such as forming gas is preferred, with pure hydrogen gas being preferred. Heating in pure hydrogen gas allows the sintering temperature of the copper particles to be lowered. When pure hydrogen gas is used, the gas reaches the center of the through holes 30, even if the substrate is as thick as 600 μm and the through holes 30 have a small diameter of 10 μm, making it easy to obtain a metal body containing a copper sintered body.

[0097] 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. From the viewpoint of volatilizing all the volatile solvent and improving yield, the maximum temperature holding time may be 1 minute or higher, and may be 60 minutes or lower, 40 minutes or lower, or 30 minutes or lower.

[0098] In this embodiment, by using the metal paste of this embodiment, sintering can be performed in an atmosphere containing formic acid gas at a low temperature of 300° C. or less, 200° C. or less, or 150° C. or less, and firing may be performed at 100 to 300° C., 100 to 200° C., or 100 to 150° C. In this case, a conductive via with excellent conductivity and connection reliability can also be formed.

[0099] The conductive via precursor may be fired without pressure or under pressure. In the latter case, in an atmosphere containing pure hydrogen gas, the pressure may be 0.05 MPa or more, 0.1 MPa or more, or 0.3 MPa or more, and 20 MPa or less, 15 MPa or less, or 10 MPa or less. In an atmosphere containing nitrogen gas, the pressure may be 1 MPa or more, or 3 MPa or more, and 20 MPa or less, 15 MPa or less, or 10 MPa or less.

[0100] By setting the pressure to 0.05 MPa or higher when pure hydrogen gas is used, or 1 MPa or higher when nitrogen gas is used, it becomes easier to suppress the generation of voids in the conductive via formed in the center of the through hole 30, and it becomes easier to obtain a conductive via with good conductivity. Furthermore, by setting the pressure to the above-mentioned lower limit or higher, when 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.

[0101] Furthermore, as long as the pressure applied during firing is within the above range, no special pressure device is required, and voids can be reduced and the bonding strength and connection reliability can be further improved without impairing yield. Methods for applying pressure to a silicon substrate having a conductive via precursor formed in a through hole include, for example, a method of placing a weight on the substrate, a method of applying pressure using a pressure device, and a method of applying pressure using a fixing jig for applying pressure.

[0102] The copper sintered body contained in the metal body may have a copper content of 95% by mass or more, 97% by mass or more, 98% by mass or more, or even 100% by mass, excluding light elements. If the copper content in the copper sintered body is within the above range, the formation of intermetallic compounds or the precipitation of different elements at the copper metal grain boundaries can be suppressed, the properties of the copper metal constituting the copper sintered body can be strengthened, and even better connection reliability can be obtained.

[0103] In step d, the conductive via precursor has an exposed surface VP1 that is flat and has a sufficiently small difference in height from the substrate surface, and also has a composition that is resistant to volumetric shrinkage upon firing, so that the difference in height between the surface SP0 of the substrate 40 and the exposed surface VP2 of the conductive via 3c can be made sufficiently small.

[0104] The step between the surface SP0 of the substrate 40 and the exposed surface VP2 of the conductive via 3c (or the recess of the conductive via 3c) may be 5 μm or less in the direction perpendicular to the substrate surface, or may be 3 μm or less. Also, the average step calculated by the following method may be within the above range. (average step height) An image of a cross section passing through the center of the hole (via) is acquired and binarized to determine 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 is calculated by dividing this by the spacing Wb of the inner walls of the hole.

[0105] Through the above-described steps a to d, the substrate 50 with conductive vias can be obtained. In the substrate 50 with conductive vias, the exposed surfaces of the conductive vias are flat (smooth) and the difference in level with the surface SP0 of the substrate 40 is sufficiently small, so that wiring can be easily formed and the substrate 50 can exhibit a sufficiently low connection resistance even after wiring formation.

[0106] The method for manufacturing a substrate with conductive vias of this embodiment may further include a step e of forming wiring, in which case the method may be used as a method for manufacturing a wiring substrate with conductive vias.

[0107] [Process e] This process can include a resist forming process, a plating process, a resist removing process, and an etching process, which will be described below.

[0108] <Resist formation process> In the resist formation process, for example, as shown in (a) and (b) of Figure 4, a negative photosensitive dry film 8 for etching resist is laminated on the main surface of the silicon substrate 40 and the conductive via 3c, and then a light-transmitting photomask is placed over the wiring shape, exposed to ultraviolet light, and the unexposed areas are removed with a developer to form an etching resist 8a.

[0109] Other methods for forming the etching resist 8a include, for example, a method of silk-screen printing resist ink and a method of laminating a dry film resist using a laminator.

[0110] <Plating process> In the plating step, for example, as shown in FIG. 4(c), wiring 9 can be formed in the openings of the etching resist 8a by a method such as electrolytic plating or electroless plating.

[0111] <Resist removal process> In the resist removal step, for example, as shown in FIG. 4(d), the etching resist 8a can be removed by a method such as stripping by a wet process using an alkaline aqueous solution or an organic solvent-based chemical liquid such as an organic amine-based liquid such as TMAH or a ketone-based liquid such as acetone, or stripping by a dry process using plasma, ozone, or the like.

[0112] <Etching process> In the etching step, the metal coating 2 in the portion not covered with 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.

[0113] Examples of etching methods include methods using chemical etching solutions typically used for wiring 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.

[0114] By the above step e, a wiring substrate 52 with conductive vias as shown in FIG. 4(e) can be obtained.

[0115] In the above-described method, a step of removing at least a part of the conductor such as the sintered body of the metal base or the metal coating 2 remaining on the main surface of the silicon substrate 40 may be provided before the step e.

[0116] The means for removing the conductor include chemical polishing, mechanical polishing, chemical mechanical polishing, fly-cutting, plasma treatment, etc. Fly-cutting refers to cutting and flattening with a surface planer.

[0117] Furthermore, a metal coating may be further formed on the surface of the substrate 50 with conductive vias obtained through the above-described steps a to d. Examples of metal coatings include titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold. From the viewpoint of adhesion and subsequent etching, the metal coating is preferably copper. The metal coating can be formed by plating or sputtering, but sputtering is more preferable. In this case, in the above-described resist formation step, plating step, resist removal step, and etching step, the intrusion of chemicals into the copper sintered body having a porous structure can be prevented, thereby suppressing oxidation of the copper sintered body and improving reliability.

[0118] According to the manufacturing method of the substrate with conductive vias of this embodiment, it is possible to obtain a substrate with conductive vias in which the main surface of the substrate (e.g., metal coating 2, etc.) is fully exposed and the step between the main surface of the substrate and the conductive vias is sufficiently small, so that processes for smoothing the main surface of the substrate, such as the process of removing the conductor described above, can be omitted.

[0119] Furthermore, in this embodiment, a step S2 may be performed in which a resin-containing portion containing a photosensitive resin composition or a cured product thereof is provided in the conductive via of the substrate with conductive vias obtained through the above-described steps a to d. This makes it easier to maintain excellent connection reliability even after wiring formation. The inventors speculate that the reason for this effect is as follows. First, forming the conductive via from a metal sintered body having a porous structure provides stress relaxation and makes it easier to suppress cracking of the material around the metal sintered body. On the other hand, metal sintered bodies having a porous structure are susceptible to the adverse effects of oxidation due to the penetration of chemicals used in wiring formation (e.g., oxidation of the metal sintered body due to the penetration of an aqueous solution). In contrast, providing a resin-containing portion in the conductive via is thought to sufficiently mitigate the above adverse effects. In addition, the use of a photosensitive resin composition allows the resin composition to be removed from the surface of the metal sintered body by a corresponding development process while leaving the resin composition in the metal sintered body, which is also thought to be one of the reasons for the above effect.

[0120] 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, with the resin-containing portion being concentrated on the opening side (the exposed surface side of the conductive via). This makes it possible to suppress an increase in connection resistance due to the resin-containing portion, while preventing adverse effects caused by penetration of chemicals or the like in the wiring formation process in the subsequent step.

[0121] The photosensitive resin composition may be either negative or positive, as long as it can form a predetermined pattern by exposure and development.

[0122] Examples of methods for providing a resin-containing portion containing a photosensitive resin composition in 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 the photosensitive resin composition in 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.

[0123] Step S2 may include step S2-1a of laminating a film-like negative photosensitive resin composition on the surface of the substrate with conductive vias, thereby impregnating at least a portion of the conductive vias with the negative photosensitive resin composition, and step S2-2a of removing the film-like negative photosensitive resin composition by a development treatment after step S2-1a, thereby exposing the conductive vias having resin-containing portions containing the negative photosensitive resin composition at the openings of the holes.

[0124] As the film-like negative photosensitive resin composition, a dry film resist such as a photocurable dry film resist or a thermosetting dry film resist can be used, and for example, commercially available products such as RD-1619 (product name, manufactured by Resonac Corporation), HM-4035 (product name, manufactured by Resonac Corporation), HM-4056 (product name, manufactured by Resonac Corporation), TMMF NA1000 (product name, manufactured by Tokyo Ohka Kogyo Co., Ltd.), and PSR-800 AUS SR-1 (product name, manufactured by Taiyo Ink Mfg. Co., Ltd.) may be used.

[0125] The film-like negative photosensitive resin composition can be laminated using a roll laminator, a laminator, a press, or the like.

[0126] The pressure may be 0.1 MPa or more, 0.4 MPa or more, or 1 MPa or more from the viewpoint of facilitating impregnation of the conductive vias with the photosensitive resin composition, and the upper limit of the pressure may be 10 MPa or less from the viewpoint of minimizing the influence on the substrate.

[0127] To facilitate 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 a range in which the photosensitive resin composition does not harden, and may be 50°C to 100°C, or 70°C to 90°C.

[0128] To facilitate impregnation of the conductive vias with the photosensitive resin composition, the substrate may be maintained at a vacuum of 1000 Pa or less, or at a vacuum of 200 Pa or less, and then laminated with a film of a negative photosensitive resin composition.

[0129] 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 from the exposed surface of the conductive via may be 1 μm or more, 2 μm or more, or 3 μm or more.

[0130] In step S2-2a, a development process suitable for the photosensitive resin composition can be carried out. Examples of the developer that can be used include 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, and an alkaline aqueous solution such as ammonia water. Examples of the development method include shower development, spray development, immersion development, and puddle development.

[0131] Step S2 may further include, after step S2-2a, step S2-3a of curing the negative photosensitive resin composition contained in the resin-containing portion.

[0132] In the case of photocuring, examples of actinic rays used for exposure include light emitted from a g-line stepper as a light source; ultraviolet light emitted from a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, an i-line stepper, or the like as a light source; electron beams; laser beams; etc. The exposure dose is appropriately selected depending on the light source used, the thickness of the impregnated photosensitive resin composition, etc.

[0133] When the negative photosensitive resin composition contains a thermosetting component, it may be thermally cured.

[0134] Step S2 may further include, after step S2-3a, step S2-4a of performing a desmear treatment on at least the exposed surfaces of the conductive vias.

[0135] Examples of the desmear treatment include plasma cleaning and treatment with a desmear solution containing permanganate and a caustic composition (for example, an alkali metal hydroxide).

[0136] In another embodiment, step S2 may include step S2-1b of applying a liquid negative photosensitive resin composition to the surface of the substrate with conductive vias to impregnate at least a portion of the conductive vias with the negative photosensitive resin composition, and step S2-2b of removing the coating of the liquid negative photosensitive resin composition by a development treatment after step S2-1b to expose the conductive vias having resin-containing portions that contain the negative photosensitive resin composition at the openings of the holes.

[0137] As the liquid negative photosensitive composition, for example, commercially available products such as PSR-4000 G24K / CA-40 G24 (product name, manufactured by Taiyo Ink Mfg. Co., Ltd.), TER-20HF (product name, manufactured by Taiyo Ink Mfg. Co., Ltd.), and TMMR NA1000PM (product name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) may be used.

[0138] Examples of methods for applying a liquid negative photosensitive composition include screen printing, transfer printing, offset printing, jet printing, a dispenser, a jet dispenser, a needle dispenser, a comma coater, a slit coater, a die coater, a gravure coater, a slit coater, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, a bar coater, an applicator, a particle deposition method, a spray coater, a spin coater, and a dip coater. From the viewpoints of workability in application and uniformity of the thickness of the coating film, application may be by screen printing or spin coating.

[0139] The depth to which the conductive via is impregnated with the photosensitive resin composition and the method for developing the coating film of the liquid negative photosensitive resin composition may be the same as those in steps S2-1a and S2-2a described above.

[0140] Furthermore, after step S2-2b, step S2-3b of curing the negative photosensitive resin composition contained in the resin-containing portion may be performed, similar to the above-mentioned steps S2-3a and S2-4a, and after step S2-3b, step S2-4b of performing a desmear treatment on at least the exposed surfaces of the conductive vias may be performed.

[0141] In another embodiment, step S2 may include step S2-1c of applying a liquid positive photosensitive resin composition or laminating a film-like positive photosensitive resin composition to the surface of the substrate with conductive vias, thereby impregnating at least a portion of the metal sintered body with the positive photosensitive resin composition, and step S2-2c of removing the coating of the liquid positive photosensitive resin composition or the film-like positive photosensitive resin composition by exposure and development treatment after step S2-1c, thereby exposing a conductive via having a resin-containing portion containing the positive photosensitive resin composition at the opening of the hole.

[0142] As the positive photosensitive composition, for example, commercially available products such as AH-3000 (product name, manufactured by Resonac Corporation), AR-5100 (product name, manufactured by Resonac Corporation), and OFPR-8600 (product name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) may be used.

[0143] The above-mentioned methods can be used for applying the photosensitive composition and laminating the photosensitive composition.

[0144] The depth to which the conductive vias are impregnated with the photosensitive resin composition may be the same as in the above-described step S2-1a.

[0145] The exposure in step S2-2c can be, for example, light emitted from a g-line stepper as a light source; ultraviolet light emitted from a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, an i-line stepper, or the like as a light source; electron beams; laser beams; etc. The exposure dose is appropriately selected depending on the light source used, the thickness of the impregnated photosensitive resin composition, etc.

[0146] The method for developing the coating film of the liquid positive photosensitive resin composition and the film-like positive photosensitive resin composition may be the same as that of the above-mentioned step S2-2a.

[0147] In addition, when the positive photosensitive resin composition contains a thermosetting component, step S2-2c may be followed by step S2-3c of thermally curing the positive photosensitive resin composition contained in the resin-containing portion. Furthermore, step S2-3c may be followed by step S2-4c of desmearing at least the exposed surfaces of the conductive vias, similar to step S2-4a described above. [Example]

[0148] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0149] [Preparation of metal paste] (Preparation Examples A to W and Comparative Preparation Examples A to I) The raw materials shown below were mixed in the proportions shown in Tables 1 to 10 using a triple roll mill to prepare metal pastes.

[0150] <First copper particles> (Wet copper powder) Spherical copper particles W1:1050Y (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 0.81 μm, spherical shape) Spherical copper particles W2:1100Y (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 1.1 μm, spherical shape) Spherical copper particles W3: 1200Y (Mitsui Kinzoku Co., Ltd., average particle size (D50): 2.1 μm, spherical) Spherical copper particles W4:1300Y (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 3.5 μm, spherical shape) Flat copper particles W1:1100YP (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 1.4 μm, flat) Flat copper particles W2: 1200YP (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 3.1 μm, flat) (atomized copper powder) Spherical copper particles A1: MA-C02K (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 1.8 μm, spherical) Spherical copper particles A2: MA-C025K (Mitsui Kinzoku Co., Ltd., average particle size (D50): 2.4 μm, spherical) Spherical copper particles A3: MA-C03K (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 3.4 μm, spherical)

[0151] <Second copper particles> Spherical copper particles W5: CH0200L1 (Mitsui Kinzoku Co., Ltd., average particle size (D50): 200 nm, spherical)

[0152] <Solder particles> Solder particle 1: SnBi58 solder STC-3 (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 4.1 μm, spherical)

[0153] <Volatile solvent> (High vapor pressure solvent: vapor pressure between 4 Pa and 30 Pa at 20°C) α-Terpineol: Fujifilm Wako Pure Chemical Industries, Ltd., vapor pressure at 20°C: 6.5 Pa (Low vapor pressure solvent: vapor pressure of less than 4 Pa at 20°C) Isobornylcyclohexanol: Tersolv MTPH, manufactured by Nippon Terpene Chemical Industry Co., Ltd., vapor pressure at 20°C: 0.004 Pa Diethylene glycol mono-n-butyl ether: Produced by Showa Chemical Co., Ltd., vapor pressure at 20°C: 1.3 Pa

[0154] The metal pastes obtained in Preparation Examples A to W and Comparative Preparation Examples A to I were evaluated for viscosity, printability, bondability, and volume resistivity of the sintered body according to the following methods.

[0155] <Viscosity> The viscosity of the metal paste was measured using a micro spiral viscometer PCU-02V (manufactured by Malcom Co., Ltd.) under the measurement conditions of a rotation speed of 10 rpm and a temperature of 25°C.

[0156] <Printability> In the <Preparation of Metal Particle Film> described below, when printing was performed on a 100 μm thick PET film using a screen printer, the number of pinholes that had formed due to the coating not being applied to the PET film side was counted. Based on the number of pinholes, printability was evaluated according to the following criteria. Evaluations A to D were considered to be good. (Judgment criteria) A: No pinholes B: Number of pinholes is 1 or more but less than 3 C: Number of pinholes is 3 or more but less than 5 D: Number of pinholes is 5 or more but less than 10 E: Number of pinholes is 10 or more but less than 20 F: 20 or more pinholes

[0157] In addition, in the <Preparation of Metal Particle Film> described later, after printing on a 100 μm thick PET film using a screen printer, the coating amount (g) of an 8-inch diameter film was measured.

[0158] <Zygosity> According to the following method, bonded samples for shear strength testing were prepared and die shear strength was measured, and the bondability was evaluated according to the following criteria. Note that samples with ratings of A to C can be considered as good.

[0159] (Preparation of joint samples for shear strength testing) 3×3mm 2Using a 100 μm thick stainless steel mask with square openings and a squeegee, the metal paste was stencil printed onto a 25 × 20 × 3 mm thick copper plate. After drying at 90 °C for 10 minutes using a hot plate, the plate was placed in a tube furnace (manufactured by AVC Corporation) and argon gas was purged at a flow rate of 1 L / min. The temperature was then increased to 225 °C over 10 minutes while hydrogen gas was flowed at 300 mL / min. The metal paste was then sintered at 225 °C for 60 minutes. The plate was then cooled by flowing argon gas at a flow rate of 0.3 L / min and removed into air at 50 °C or below. The copper plate with the metal body formed thereon was used as a bonded sample for shear strength testing.

[0160] (Measurement of die shear strength) For the bonded samples for shear strength tests, a universal bond tester (4000 series, Daisy Japan Co., Ltd.) equipped with a DS-100 load cell was used to measure the die shear strength by pressing the metal body or Cu plate horizontally at a measurement speed of 5 mm / min and a measurement height of 50 μm. The average value of 10 points was calculated and used as the average bond strength. (Judgment criteria) A: Average bonding strength is 50N or more B: Average bonding strength is 40N or more but less than 50N C: Average bonding strength is 20N or more but less than 40N D: Average bonding strength is 10N or more but less than 20N E: Average bonding strength is less than 10N

[0161] <Volume resistivity measurement> 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 coating film was dried on a hot plate at 90 °C for 10 minutes, then placed in a tube furnace (manufactured by AVC Corporation). Argon gas was flowed at 1 L / min to replace the air inside the tube furnace with argon gas. The temperature was then raised to 225 °C over 10 minutes while hydrogen gas was flowed at 300 mL / min, and the metal paste was sintered by sintering at 225 °C for 60 minutes. The wafer was then cooled by flowing argon gas at a flow rate of 0.3 L / min and removed into air at below 50 °C to obtain a sample with a metal body formed on the wafer.

[0162] The volume resistivity of the metal body in the above sample was calculated from the sheet resistance measured with a four-point needle sheet resistance meter (Mitsubishi Analytech, product name: Loresta GP) and the film thickness determined with a non-contact surface / layer cross-sectional shape measurement system (VertScan, Ryoka Systems Co., Ltd.).

[0163] [Table 1]

[0164] [Table 2]

[0165] [Table 3]

[0166] [Table 4]

[0167] [Fabrication of silicon substrate with conductive vias] (Examples 1 to 87 and Comparative Examples 1 to 11) A silicon substrate with conductive vias was fabricated by the following procedure.

[0168] <Preparing the silicon substrate> A silicon substrate was prepared with through holes, with a titanium layer, a nickel layer, and a copper layer formed in that order on both main surfaces and on the wall surfaces of the through holes. The silicon substrate had a diameter of 6 inches and a thickness of 300 μm, and the titanium layer, nickel layer, and copper layer were formed in that order by sputtering, with through holes of the diameters (via diameters) shown in the table.

[0169] <Preparation of metal particle film> The metal paste prepared above was printed onto a 100 μm thick PET film in an 8-inch diameter (circular shape with a diameter of 20 cm) using a screen printing plate (wire diameter: 23 μm, mesh number: 400, opening: 41 μm, void ratio: 41 μm) using a screen printer, to obtain a metal particle film provided with a metal particle-containing layer.

[0170] <Conductive via formation> Using a bonding machine VJ-35 (manufactured by Ayumi Industries Co., Ltd.), the metal particle film was bonded to the silicon substrate from the metal particle-containing layer side, and the laminate was then vacuum-pressed at room temperature under a pressure of 3 MPa to fill the through-holes with the metal paste, causing the metal paste to protrude from the side of the silicon substrate opposite to the side where the metal particle film was bonded.

[0171] Next, the PET film was peeled off from the laminate, and the laminate was dried in the air for 10 minutes at 90° C. The concentrations (mass%) of metal particles in the metal paste portion before and after drying are shown in the table.

[0172] For the dried laminate, as shown in Figure 3(a) to (d), the metal paste on the main surface of the silicon substrate on which the metal particle film was bonded was removed using a rubber squeegee, and then the metal paste protruding from the side opposite the side on which the metal particle film was bonded was removed using a rubber squeegee.

[0173] Next, the silicon substrate with the conductive via precursor formed in the through-hole by the above process was placed in a tube furnace (manufactured by AVC Corporation), and argon gas was flowed at 1 L / min to replace the air in the tube furnace with argon gas. Thereafter, while flowing hydrogen gas at 300 mL / min, the temperature was raised to 300°C over 10 minutes, and a sintering treatment was performed at 300°C for 60 minutes to sinter the conductive via precursor. Thereafter, argon gas was flowed at a flow rate of 0.3 L / min to cool the substrate, and the substrate was removed into air at 50°C or below to obtain a silicon substrate with conductive vias. In Examples 70 to 87, the conductive via precursor was sintered by flowing formic acid vapor at a concentration of 3.0% by volume (the remainder being nitrogen), while the temperature was raised to the temperature listed in the table over 10 minutes, and a sintering treatment was performed under the following conditions. Examples 70 to 72: 350°C / 4 minutes Examples 73 to 75: 300°C / 6 minutes Examples 76 to 78: 250°C / 10 minutes Examples 79 to 81: 200°C / 30 minutes Examples 82 to 84: 150°C / 60 minutes Examples 85 to 87: 120°C / 60 minutes

[0174] <Evaluation of Silicon Substrates with Conductive Vias> The silicon substrates with conductive vias obtained above were evaluated for the presence or absence of cracks and voids in the conductive vias, the porosity of the conductive vias, and the presence of depressions after sintering according to the following methods.

[0175] (Presence or absence of cracks in conductive vias) The cross-sections of the conductive vias in the silicon substrate with conductive vias were exposed by cross-section polishing, and 30 conductive vias were observed using a digital microscope (manufactured by Keyence Corporation, product name: VHX-6000) to check for the presence or absence of cracks (length 10 μm or more).

[0176] (presence or absence of voids in conductive vias) The cross-sections of the conductive vias in the silicon substrate with conductive vias were exposed by cross-section 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 more).

[0177] (dent after sintering) The cross-sections of the conductive vias of the silicon substrate with conductive vias were exposed by cross-section polishing, and 30 conductive vias were observed using a digital microscope (manufactured by Keyence Corporation, product name: VHX-6000), and the average step height was calculated using the following method. [Average step height] An image of a cross section passing through the center of the via was obtained, and the cross-sectional image was binarized to determine 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 then divided by the spacing Wb between the inner walls of the hole to calculate the average step height (=Sb / Wb). The average value of the average step height at 30 points was calculated, and the dents after sintering were evaluated according to the following criteria. Note that a rating of C or higher can be considered as good. (Judgment criteria) A: The average step height is less than 1 μm B: The average step height is 1 μm or more and less than 3 μm C: The average step height is 3 μm or more and less than 5 μm D: The average step height is 5 μm or more and less than 10 μm E: The average step height is 10 μm or more

[0178] (Porosity of conductive vias) The mechanically polished silicon substrate with conductive vias was cut in the thickness direction, and the cross section of the center of the conductive via in the silicon substrate was exposed using a focused ion beam. This cross section was then observed. When observing the cross section of the center of the through hole in the silicon substrate, a range of ±5 μm from the center of the through hole in the thickness direction of the silicon substrate and ±5 μm in the direction perpendicular to the thickness direction of the silicon substrate was observed. A focused ion beam processing and observation device (manufactured by Hitachi High-Technologies Corporation, product name: MI4050) was used. For observation, a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, product name: S-3700N) was used at a magnification of 5000x to capture cross-sectional images (approximately 10 μm square) of the conductor. Five observation locations were used. The obtained cross-sectional images were binarized using image analysis software (Adobe Photoshop (registered trademark) Elements) to distinguish the sintered copper portion from the porous (vacant) portion. For each of the five observation points, the ratio of the area of the porous portion to the total area of the cross section of the conductive via was calculated, and this was taken as the porosity. The average value of the porosities at the five observation points was taken as the porosity of the conductive via.

[0179] <Evaluation of wiring boards> A UV-curable etching resist dry film H-W425 (trade name, manufactured by Resonac Corporation) was pressure-bonded to the surface of the silicon substrate with conductive vias obtained above using a laminator. A photomask was then placed, a wiring pattern was exposed, and the resist was developed. Next, electrolytic plating was performed on the resist openings, followed by resist peeling and seed layer etching to form wiring with a 300 μm × 600 μm wiring pattern, thereby obtaining a test piece 55 (wiring substrate) as shown in FIG. 5. In test piece 55, the conductive vias formed in the through holes were electrically connected by wiring provided on the substrate surface.

[0180] The test pieces obtained above were evaluated for initial resistance, connection reliability, the presence or absence of cracks in the substrate, and depressions in the conductive vias after resist peeling, according to the following methods.

[0181] (initial resistance) The resistance value of a predetermined number of connected vias was measured as the initial resistance value of the test piece 55. The number of vias was set as follows depending on the via diameter. Based on this connected resistance value, the initial resistance value was evaluated according to the following criteria. A rating of B or higher can be considered good. (Number of vias) 30μmφ: 30 pieces 50μmφ: 25 pieces 100μmφ: 20 pieces (Judgment criteria) A: Resistance value less than 10mΩ B: Resistance is 10mΩ or more and less than 30mΩ C: Resistance is 30mΩ or more and less than 100mΩ D: Resistance is 100mΩ or more and less than 500mΩ E: Resistance value is 500mΩ or more

[0182] (Connection reliability) Test piece 55 was placed in a temperature cycle tester (TSA-72SE-W, manufactured by Espec Corporation) and subjected to a temperature cycle connection reliability test under the following conditions: low temperature: -55°C for 15 minutes, room temperature: 2 minutes, high temperature: 125°C for 15 minutes, defrost cycle: automatic, and number of cycles: 50, 100, 300, 500, and 1000. For each test piece that underwent each number of cycles, the resistance value of the connection of the above number of vias, which is set according to the via diameter, was measured. Based on this connected connection resistance value, connection reliability was evaluated according to the following criteria. (Judgment criteria) A: Resistance change rate is less than 1% of the initial resistance value B: Resistance change rate is 1% or more but less than 3% of the initial resistance value C: Resistance change rate is 3% or more but less than 5% of the initial resistance value D: Resistance change rate is 5% or more but less than 10% of the initial resistance value E: Resistance change rate is 10% or more but less than 20% of the initial resistance value F: Resistance change rate is 20% or more compared to the initial resistance value

[0183] (Cracked circuit board) The test piece 55 was visually inspected to check for cracks in the silicon substrate.

[0184] (Dent after resist removal) In preparing the test piece 55, after removing the resist, the cross section of the conductive via was exposed by cross-section polishing, and 30 conductive vias were observed using a digital microscope (Keyence Corporation, product name: VHX-6000). The average value of the average step height was calculated in the same manner as in the evaluation of the dents after sintering. Then, the dents after resist removal were evaluated according to the following evaluation criteria. Note that evaluations of C or higher can be considered good. (Judgment criteria) A: The average step height is less than 1 μm B: The average step height is 1 μm or more and less than 3 μm C: The average step height is 3 μm or more and less than 5 μm D: The average step height is 5 μm or more and less than 10 μm E: The average step height is 10 μm or more

[0185] [Observation and consideration of conductive vias] (Observation 1) For the silicon substrate with conductive vias fabricated in Example 1, a focused ion beam processing and observation device (Hitachi High-Technologies Corporation, product name: MI4050) was used to expose the cross section of the center of the conductive via in the silicon substrate with conductive vias using a focused ion beam, and the cross section was observed. For the observation, a scanning electron microscope (Hitachi High-Technologies Corporation, product name: S-3700N) was used to photograph cross-sectional images of the copper sintered body at magnifications of 5,000 and 20,000 (see FIG. 6 ). The images shown in FIG. 6 (a) are images at 5,000 magnification, and (b) are images at 20,000 magnification. As shown in FIG. 6 (b), the copper sintered body has a structure in which first copper particles are filled between second copper particles, bonding the particles together. The formation of such a dense copper sintered body and the suppression of shrinkage during sintering, which prevents the occurrence of voids and cracks and depressions, are believed to enable sufficiently low connection resistance even after wiring formation, and to enable the resulting wiring substrate to have excellent connection reliability.

[0186] (Observation 2) For the silicon substrate with conductive vias produced in Comparative Example 1, a cross-sectional image of the copper sintered body was taken in the same manner as in Observation 1 (see Figure 7). The image shown in Figure 7 was taken at a magnification of 5,000 times. As shown in Figure 7, the conductive via contains the copper sintered body, solder, and voids that have occurred around the solder. If a large number of such voids are formed with a large volume, it is thought that the penetration of etching solution during wiring formation will be more likely to occur, and the presence of the voids themselves will reduce the connection reliability of the resulting wiring substrate, especially when subjected to large temperature changes.

[0187] [Table 5]

[0188] [Table 6]

[0189] [Table 7]

[0190] [Table 8]

[0191] [Table 9]

[0192] [Table 10]

[0193] [Table 11]

[0194] [Table 12]

[0195] [Table 13]

[0196] [Table 14]

[0197] [Table 15]

[0198] [Table 16]

[0199] [Fabrication of silicon substrate with conductive vias - 2] (Examples 88 to 91) A silicon substrate with conductive vias was fabricated by the following procedure.

[0200] [Preparation of metal paste] (Preparation example a) The raw materials shown above were mixed in the proportions shown in Table 17 using a triple roll mill to prepare a metal paste, and the properties were confirmed in the same manner as above.

[0201] [Table 17]

[0202] <Preparing the silicon substrate> Silicon substrates were prepared with through holes, each having a titanium layer, a nickel layer, and a copper layer formed in that order on both main surfaces and on the wall surfaces of the through holes. The silicon substrates were 6 inches in diameter and 300 μm thick, and the titanium layer, nickel layer, and copper layer were formed in that order by sputtering. Substrates were prepared with through holes having diameters (via diameters) of 50, 90, 150, and 200 μm.

[0203] <Preparation of metal particle film> The metal paste of Preparation Example a prepared above was printed onto a 100 μm thick PET film in an 8-inch diameter (circular shape with a diameter of 20 cm) using a screen printing plate (line diameter: 23 μm, mesh number: 400, mesh size: 41 μm, void ratio: 41 μm) using a screen printing machine to obtain a metal particle film provided with a metal particle-containing layer.

[0204] <Conductive via formation> Using a bonding machine VJ-35 (manufactured by Ayumi Industries Co., Ltd.), the metal particle film was bonded to the silicon substrate from the metal particle-containing layer side, and the laminate was then vacuum-pressed at room temperature under a pressure of 3 MPa to fill the through-holes with the metal paste, causing the metal paste to protrude from the side of the silicon substrate opposite to the side where the metal particle film was bonded.

[0205] Next, the PET film was peeled off from the laminate, and the resulting product was dried in the air for 10 minutes at 90° C. The concentrations (mass %) of metal particles in the metal paste portion before and after drying were 95.7 mass % and 97.8 mass %, respectively.

[0206] For the dried laminate, as shown in Figure 3(a) to (d), the metal paste on the main surface of the silicon substrate on which the metal particle film was bonded was removed using a rubber squeegee, and then the metal paste protruding from the side opposite the side on which the metal particle film was bonded was removed using a rubber squeegee.

[0207] Next, the silicon substrate with the conductive via precursor formed in the through-hole by the above process was placed in a tube furnace (manufactured by AVC Corporation), and argon gas was flowed at 1 L / min to replace the air in the tube furnace with argon gas. Then, while flowing hydrogen gas at 300 mL / min, the temperature was raised to 300 °C over 10 minutes, and sintering treatment was performed at 300 °C for 60 minutes to sinter the conductive via precursor. After that, argon gas was flowed at a flow rate of 0.3 L / min, and the substrate was removed into air at 50 °C or below to obtain a silicon substrate with conductive vias.

[0208] The silicon substrates with conductive vias obtained above were evaluated for the presence or absence of cracks and voids in the conductive vias, the porosity of the conductive vias, and the presence of depressions after sintering, according to the methods described above.

[0209] [Creating a wiring board] (Examples 88 to 91) Conductive vias having a resin-containing portion containing a photosensitive resin composition were formed in the silicon substrates with conductive vias (via diameters: 50, 90, 150, and 200 μm) obtained above using the following procedure, and wiring was then formed to obtain wiring substrates, which were then evaluated.

[0210] On the surface of the glass substrate with the metal sintered body obtained above, a dry film for ultraviolet curable etching resist "RD-1619" (product name, manufactured by Resonac Corporation) (photosensitive resin composition F1) was laminated by atmospheric pressure lamination under conditions of a roll pressure of 3 MPa, a processing temperature of 120°C, and a conveying speed of 1.0 m / s to form a dry film resist layer. Next, the dry film resist layer was laminated using a direct writing exposure machine "DE-1UH" (product number, manufactured by Via Mechanics Co., Ltd.) at 55 mJ / cm 2The resist was exposed to light in a predetermined pattern under the following conditions. One minute later, a post-exposure bake (PEB) treatment was performed at 70°C for 1 minute. This was followed by a treatment using a 1% sodium carbonate developer at 30°C for 70 seconds at a spray pressure of 0.17 MPa. Residues were then removed by oxygen plasma treatment to form a resist pattern. Surface treatments were performed using ammonium persulfate (100 g / L, RT, 30 seconds) and sulfuric acid solution (100 g / L, RT, 30 seconds), followed by electroplating in the resist openings. The resist was then stripped and the seed layer was etched to form a 300 μm × 600 μm wiring pattern, yielding a test piece 55 (wiring substrate) as shown in FIG. 5. The wiring pattern was finished to a thickness of approximately 10 μm after etching the seed layer. In test piece 55, conductive vias formed in the through holes were electrically connected by wiring provided on the substrate surface.

[0211] [Impregnation depth of photosensitive resin composition into porous portion of conductive via] The cross section of the conductive via of the glass substrate with conductive via was exposed by cross-section polishing, the surface was cleaned by ion milling, and this cross section was observed. Using a scanning electron microscope S-3700N (manufactured by Hitachi High-Technologies Corporation), the impregnation depth of the photosensitive resin composition (or its cured product) into the porous portion was measured. The distance from the via surface to the porous portion (void) was measured at 10 points, and the average value was taken as the impregnation depth.

[0212] [Wiring board evaluation] The test pieces obtained above were evaluated for initial resistance, connection reliability, and depressions on the surface of the wiring pattern formed on the conductive vias according to the following methods.

[0213] <Initial resistance> The resistance value of 1000 connected vias was measured as the initial resistance value of the test piece 55 (wiring board). Based on this connected resistance value, the initial resistance value was evaluated according to the following criteria. (Number of vias) 1000 pieces (Judgment criteria) A: Resistance is less than 6 Ω B: Resistance is 6Ω or more and less than 10Ω C: Resistance is 10Ω or more and less than 20Ω D: Resistance is 20Ω or more and less than 50Ω E: Resistance is 50Ω or more

[0214] <Connection reliability - temperature cycle test> Test piece 55 (wiring board) was placed in a temperature cycle tester (TSA-72SE-W, manufactured by Espec Corporation) and a temperature cycle connection reliability test was performed under the following conditions: low temperature: -55°C for 15 minutes, room temperature: 2 minutes, high temperature: 125°C for 15 minutes, defrost cycle: automatic, number of cycles: 50, 100, 300, 500, 1000. For each test piece that underwent each number of cycles, the resistance value of the connection of the above number of vias was measured. Based on this connected connection resistance value, connection reliability was evaluated according to the following criteria. (Judgment criteria) A: Resistance change rate is less than 1% of the initial resistance value B: Resistance change rate is 1% or more but less than 3% of the initial resistance value C: Resistance change rate is 3% or more but less than 5% of the initial resistance value D: Resistance change rate is 5% or more but less than 10% of the initial resistance value E: Resistance change rate is 10% or more but less than 20% of the initial resistance value F: Resistance change rate is 20% or more compared to the initial resistance value G: Poor conduction occurs

[0215] <Connection reliability -150℃> Test piece 55 was placed in a high-temperature chamber (precision incubator DH612, manufactured by Yamato Scientific Co., Ltd.) and left at 150°C for 50, 100, 300, and 500 hours to conduct a high-temperature storage test. For each test piece after each time, the resistance value of the connection of the above number of vias was measured. Based on this connection 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 value B: Resistance change rate is 1% or more but less than 3% of the initial resistance value C: Resistance change rate is 3% or more but less than 5% of the initial resistance value D: Resistance change rate is 5% or more but less than 10% of the initial resistance value E: Resistance change rate is 10% or more but less than 20% of the initial resistance value F: Resistance change rate is 20% or more compared to the initial resistance value G: Poor conduction occurs

[0216] <Connection reliability at -200℃> Test piece 55 was placed in a high-temperature chamber (precision incubator DH612, manufactured by Yamato Scientific Co., Ltd.) and left at 200°C for 50, 100, 300, and 500 hours to conduct a high-temperature storage test. For each test piece after each time, the resistance value of the connection of the above number of vias was measured. Based on this connection 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 value B: Resistance change rate is 1% or more but less than 3% of the initial resistance value C: Resistance change rate is 3% or more but less than 5% of the initial resistance value D: Resistance change rate is 5% or more but less than 10% of the initial resistance value E: Resistance change rate is 10% or more but less than 20% of the initial resistance value F: Resistance change rate is 20% or more compared to the initial resistance value G: Poor conduction occurs

[0217] <Dent on the surface of the wiring pattern formed on the conductive via> The surface of the wiring pattern formed on the conductive vias of test piece 55 (wiring board) was observed for 30 conductive vias using a digital microscope (VHX-6000, manufactured by Keyence Corporation), the deepest point was measured, and the average value was taken as the depression on the wiring pattern surface. (Judgment criteria) A: The average step height is less than 2 μm B: The average step height is 2 μm or more and less than 4 μm C: The average step height is 4 μm or more and less than 6 μm D: The average step height is 6 μm or more and less than 8 μm E: The average step height is 8 μm or more

[0218] [Table 18]

[0219] [Fabrication of organic substrate with conductive vias] (Examples 92 to 95) An organic substrate with conductive vias was fabricated by the following procedure.

[0220] <Preparing the organic substrate> A 300-μm-thick high-Tg glass epoxy multilayer material, MCL-E-679F(J) (manufactured by Resonac Corporation), with 1-μm copper foil laminated on both sides, was prepared, and through holes with diameters (via diameters) of 90, 150, and 200 μm were drilled. A 0.5-μm-thick copper plating film was formed inside the vias by electroless copper plating.

[0221] An organic substrate with conductive vias and a wiring substrate were obtained and evaluated in the same manner as in Examples 89 to 91, except that the organic substrate was heated to 225°C in 10 minutes and sintered at 225°C for 60 minutes. The concentrations (mass%) of metal particles in the metal paste portion before and after drying were 95.7% and 97.8% by mass, respectively.

[0222] [Table 19] [Explanation of symbols]

[0223] 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...blind hole, 40, 41...silicon substrate, 42...rubber squeegee, 50...substrate with conductive via, 52...wiring substrate with conductive via, 55...test piece, A...pressure jig

Claims

1. a step a) of preparing a substrate having a hole formed therein, and providing a metal paste portion containing metal particles and a volatile solvent so as to fill the inside of the hole and cover at least the surface of the substrate around the hole; a step b of heating the metal paste portion to remove a portion of the volatile solvent; a step c) of removing a portion of the metal paste portion after heating so that the surface is exposed, thereby forming a conductive via precursor having a flattened exposed surface inside the hole, the conductive via precursor including the metal particles and the remainder of the volatile solvent; and step d) of firing the conductive via precursor; the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, The metal particle concentration of the metal paste portion provided in the step a is 95.0 mass% or more, A method for manufacturing a substrate with conductive vias, wherein the content of the second metal particles in the metal paste portion provided in step a is 50 mass % or less based on the total amount of the metal particles.

2. The method for manufacturing a substrate with conductive vias according to claim 1 , wherein the first metal particles and the second metal particles are copper particles.

3. The method for manufacturing a substrate with conductive vias according to claim 1 or 2, wherein the first metal particles include flaky copper particles.

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