Direct bonding

Abstract

The purpose of the present invention is to provide a novel technique for manufacturing a bonded structure by direct bonding. A bonded structure in which a structure 1 and a structure 2 are bonded with a metal plating film interposed therebetween is provided.

Description

[Technical field]

[0001] The present invention relates to direct bonding. [Background technology]

[0002] In a process of mounting a semiconductor element, the semiconductor element and a substrate are bonded with a bonding material. The semiconductor element may be, for example, a next-generation power semiconductor element (such as a silicon carbide semiconductor or a gallium nitride semiconductor).

[0003] Patent Document 1 discloses a bonded structure including a substrate, a metal film, a semiconductor element, and an adhesive layer provided at least between the substrate and the metal film and between the metal film and the semiconductor element, where the metal constituting the metal film is diffused by stress migration, and the substrate and the semiconductor element are bonded via the metal film. Patent Document 1 discloses a bonded structure including a substrate, a first metal film, a thermal stress absorbing material, a second metal film, and a semiconductor element, in this order, where at least one of the metal constituting the first metal film and the metal constituting the second metal film is diffused by stress migration, where the substrate and the thermal stress absorbing material are bonded via the first metal film, and where the semiconductor element and the thermal stress absorbing material are bonded via the second metal film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6284164 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a new manufacturing technique for a bonded structure using direct bonding. [Means for solving the problem]

[0006] Conventional solder joining techniques cannot be used to join fine Cu pillars due to concerns about solder bridging.

[0007] Conventionally, hybrid bonding technology requires high loads and high costs, such as (i) a bonding technique that requires high temperature (300℃-400℃, 2 hours) under vacuum and without pressure, (ii) a clean room, (iii) flattening by CMP (Chemical Mechanical Polishing), (vi) expensive bonding equipment, etc. In addition, it is difficult to apply this technology to fine Cu pillar bonding due to the high load bonding conditions.

[0008] Conventionally (Patent Document 1), direct bonding utilizing stress migration was possible using a metal film (Ag or Cu) formed by sputtering processing, but it was difficult to selectively form a metal film using the sputtering method.

[0009] The present invention encompasses the following direct bonding techniques.

[0010] Section 1. A bonded structure in which a structure 1 and a structure 2 are bonded via a metal plating film.

[0011] Section 2. A metal plating film 1 is provided on the structure 1, A metal plating film 2 is provided on the structure 2, 2. The joined structure according to item 1, wherein the structure 1 and the structure 2 are joined via the metal plating film 1 and the metal plating film 2.

[0012] Section 3. 2. The bonded structure according to claim 1, wherein the metal plating film has a laminated structure having two or more layers of metal plating film.

[0013] Section 4. A method for manufacturing a bonded structure, comprising the steps of: (1) forming a metal plating film 1 on a structure 1; (2) forming a metal plating film 2 on the structure 2; (3)(i) The metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2) are in contact with each other, or (ii) Between the metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2), (iii) a step of stacking the structure 1 and the structure 2 facing each other; (4) A method for producing a bonded structure, comprising the step of heating the laminate formed in step (3) to directly bond the metal plating film 1 and the metal plating film 2 together.

[0014] The bonding technology of the present invention, which utilizes hillocks of a metal plating film formed by electroless or electrolytic plating, has the following advantages: (i) it is a technology for directly bonding metal plating films to each other using hillocks in the atmosphere, without pressure (low pressure), and at low temperatures (150°C to 250°C, approximately 30 minutes); (ii) it does not require a clean room; (iii) it does not require CMP; (vi) it is applicable to fine Cu pillar bonding because there is no solder bridge and the bonding conditions are low-load; (v) it is expected to be applied to large-area bonding such as heat sinks, DBC (Direct Bonded Copper) substrates, and IC chip bonding; and (vi) electroless or electrolytic plating enables the formation of metal plating films selectively and on large and three-dimensional objects, enabling direct bonding via metal plating films in a wide range of fields of articles and materials. It is a low-load, low-cost direct bonding technology that utilizes hillocks of a metal plating film.

[0015] The present invention does not require a bonding agent (solder or metal sintered material) for bonding, for example, substrates (printed circuit boards, semiconductor wafers, semiconductor chips, etc.), and can directly bond metal plating films together by heat treatment (low temperature: approximately 150°C to 250°C, low pressure: approximately 0.1 MPa to 0.4 MPa, or no pressure, for approximately 30 minutes).

[0016] The bonding technique of the present invention is useful for semiconductor packaging. Effect of the Invention

[0017] The present invention can provide a new manufacturing technique for a bonded structure using direct bonding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention will be described in detail below.

[0019] The embodiments of the present invention are intended to provide a better understanding of the gist of the invention, and unless otherwise specified, do not limit the content of the invention.

[0020] In this specification, the terms "comprise" and "containing" are concepts which encompass all of "comprise," "consist essentially of," and "consist only of."

[0021] In this specification, when a numerical range is indicated as "A to B," it means "A or more and B or less."

[0022] In this specification, the designations parts, % etc. are generally used.

[0023] In this specification, unless otherwise specified, all parts by mass or % by mass (wt%) are used.

[0024] [1] Joined structure In the sputtering process (thin film production by vacuum deposition) of Patent Document 1, it is difficult to selectively form a metal film and to form a metal film on a large object or a three-dimensional object.

[0025] In the joined structure of the present invention, structure 1 and structure 2 are joined via a metal plating film.

[0026] In the joined structure of the present invention, preferably, a metal plating film 1 is provided on structure 1, and a metal plating film 2 is provided on structure 2, and structure 1 and structure 2 are joined via metal plating film 1 and metal plating film 2.

[0027] The direct bonding of the present invention is a technique for bonding metal plating films formed by electroless or electrolytic plating. Since electroless or electrolytic plating enables selective formation of metal plating films on large and three-dimensional objects, the direct bonding technique of the present invention enables direct bonding via metal plating films in a wide range of articles.

[0028] Structures 1 and 2 In the direct bonding technique of the present invention, the bonded structure has structure 1 and structure 2 bonded together via a metal plating film.

[0029] The structure 1 and the structure 2 are preferably made of a material (a material to be plated) on which metal plating can be applied. Examples of the material to be plated include, in addition to Cu, brass, phosphor bronze, and Cu alloys such as Corson alloy, and also Al, Mg, Fe, Ni, Pd, Ag, Au, Co, W, Mo, Pt, Si, and alloys thereof, which are metallic materials on which a metal plating film can be formed by a known technique.

[0030] Furthermore, if known techniques are used, a metal plating film can be formed on nonmetals by electroless plating, so the direct bonding technique of the present invention can also be applied to nonmetals.

[0031] Structure 1 and Structure 2 can be applied to all articles and materials to which a metal plating film can be applied, such as bumps (Cu bumps, etc.), die attach materials (materials for fixing semiconductor elements (Dies) with a die bonder), DBA (Direct Bonded Aluminum) substrates, DBC substrates, ceramic substrates, cooling fins, heat sinks (parts attached to equipment for the purpose of heat dissipation and exhaust), lead frames (parts used in semiconductor packages such as ICs and LSIs to support and fix semiconductor elements (semiconductor chips) and connect them to external wiring), passive elements (elements that consume, store, and release supplied power), iron shafts, etc.

[0032] Metal plating film (including metal plating film 1 and 2) The present invention is a method for directly bonding metal plating films together. The present invention is a method for directly bonding metal plating films together by carrying out a plating process on the surface of a material to be plated (metal or nonmetal) and utilizing hillocks that are generated by heat treatment.

[0033] The metal plating film may be a single layer, or may be a laminate of a plurality of metal plating films.

[0034] The joined structure of the present invention preferably has a metal plating film 1 on structure 1 and a metal plating film 2 on structure 2, with structure 1 and structure 2 being joined via the metal plating film 1 and the metal plating film 2.

[0035] The metal constituting the metal plating film is preferably nickel, cobalt, iron, indium, tin, palladium, gold, platinum, ruthenium, silver, copper, tungsten, molybdenum, rhenium, zinc, aluminum, or an alloy of these metals, and more preferably nickel, cobalt, palladium, silver, tungsten, molybdenum, or an alloy of these metals.

[0036] In addition, elements corresponding to the components in the plating solution are co-deposited in the metal plating film. For example, when the reducing agent contains a boron-containing compound, a phosphorus-containing compound, and / or a nitrogen-containing compound, boron, phosphorus, and / or nitrogen are co-deposited in the metal plating film.

[0037] The metal plating film has a single-layer metal plating film configuration, or a laminate configuration of a plurality of metal plating films.

[0038] The metal plating film preferably has a structure in which a plurality of metal plating films are laminated, and more preferably has a laminate structure having two or more layers of metal plating films. When the metal plating film has a structure in which a plurality of metal films are laminated, the metals constituting the plurality of metal films may be the same type of metal or different types of metal.

[0039] For example, a laminate of nickel and silver may be formed on structures 1 and 2, and a laminate may be produced in which structure 2 is laminated on structure 1 so that the silver layers of each laminate structure are in contact with each other, thereby producing a bonded structure.

[0040] When the metal plating film has a laminate structure of two or more layers, the metal plating film of the lower layer (the layer closer to the structure) is preferably electroless Ni-P plating, electroless Ni-B plating, electroless Co-P plating, electroless Co-B plating, electroless Ni-Co-P plating, electroless Ni-Co-B plating, electroless Ni-WP plating, electroless Ni-Mo-B plating, electroless Co-WP plating, electroless Co-Mo-B plating, electroless Fe-B plating, electroless In plating, electroless Sn plating, electroless Pd plating, electroless Au plating, electroless Pt plating, electroless Ru plating, electroless Ag plating, electroless Cu plating, electric Ni plating, electric Co plating, electric Ag plating, etc.

[0041] When the metal plating film has a laminate structure of two or more layers, the metal plating film of the lower layer (the layer closer to the structure) is more preferably electroless Ni-P plating, electroless Ni-B plating, electroless Co-P plating, electroless Co-B plating, electroless Ni-Co-P plating, electroless Ni-Co-B plating, electroless Ni-WP plating, electroless Ni-Mo-B plating, electroless Co-WP plating, electroless Co-Mo-B plating, electroless Pd plating, electric Ni plating, electric Co plating, etc.

[0042] When the metal plating film has a laminated structure of two or more layers, the upper (outermost) metal plating film is preferably electroless Ag plating, electroless Au plating, electroless Sn plating, electroless Cu plating, electroless Pd plating, electroless Pt plating, electroless Ru plating, etc.

[0043] When the metal plating film has a laminated structure of two or more layers, the uppermost (outermost) metal plating film is more preferably electroless Ag plating.

[0044] The laminated structure of a plurality of metal plating films (lower metal plating film / upper metal plating film) is preferably electroless Ni-P plating / electroless Ag plating, electroless Ni-B plating / electroless Ag plating, electroless Co-P plating / electroless Ag plating, electroless Co-B plating / electroless Ag plating, electroless Ni-Co-P plating / electroless Ag plating, electroless Ni-Co-B plating / electroless Ag plating, electroless Ni-WP plating / electroless Ag plating, electroless Ni-Mo-B plating / electroless Ag plating, electroless Co-WP plating / electroless Ag plating, electroless Co-Mo-B plating / electroless Ag plating, electroless Fe-B plating / electroless Ag plating, or electroless In plating. / electroless Ag plating, electroless Sn plating / electroless Ag plating, electroless Pd plating / electroless Ag plating, electroless Au plating / electroless Ag plating, electroless Pt plating / electroless Ag plating, electroless Ru plating / electroless Ag plating, electroless Ni-P plating / electroless Au plating, electroless Ni-P plating / electroless Sn plating, electroless Ni-P plating / electroless Cu plating, electroless Ni-P plating / electroless Pd plating / electroless Ag plating, electroless Ni-P plating / electroless Co-P plating / electroless Ag plating, electroless Ni-P plating / electroless Ag plating, electroless Ni plating / electroless Ag plating, electroless Ni plating / electroless Ag plating, electroless Co plating / electroless Ag plating, etc.

[0045] The laminated structure of a plurality of metal plating films (lower metal plating film / upper metal plating film) is preferably electroless Ni-P plating / electroless Ag plating, electroless Ni-B plating / electroless Ag plating, electroless Co-P plating / electroless Ag plating, electroless Co-B plating / electroless Ag plating, electroless Ni-Co-P plating / electroless Ag plating, electroless Ni-Co-B plating / electroless Ag plating, electroless Ni-WP plating / electroless Ag plating, electroless Ni-Mo-B plating / electroless Ag plating, electroless Co-WP plating / electroless Ag plating, electroless Co-Mo-B plating / electroless Ag plating, etc. The metal plating film has a laminated structure including electroless Fe-B plating / electroless Ag plating, electroless In plating / electroless Ag plating, electroless Sn plating / electroless Ag plating, electroless Pd plating / electroless Ag plating, electroless Au plating / electroless Ag plating, electroless Pt plating / electroless Ag plating, electroless Ru plating / electroless Ag plating, electroless Ni-P plating / electroless Pd plating / electroless Ag plating, electroless Ni-P plating / electroless Co-P plating / electroless Ag plating, electroless Ni-P plating / electroless Ag plating, electroless Ni plating / electroless Ag plating, and electroless Co plating / electroless Ag plating.

[0046] The laminated structure of a plurality of metal plating films (lower metal plating film / upper metal plating film) is more preferably electroless Ni-P plating / electroless Ag plating, electroless Ni-B plating / electroless Ag plating, electroless Co-P plating / electroless Ag plating, electroless Co-B plating / electroless Ag plating, electroless Ni-Co-P plating / electroless Ag plating, electroless Ni-Co-B plating / electroless Ag plating, electroless Ni-WP plating / electroless Ag plating. , electroless Ni-Mo-B plating / electroless Ag plating, electroless Co-WP plating / electroless Ag plating, electroless Co-Mo-B plating / electroless Ag plating, electroless Ni-P plating / electroless Pd plating / electroless Ag plating, electroless Ni-P plating / electroless Co-P plating / electroless Ag plating, electroless Ni-P plating / electroless Ag plating, electroless Ni plating / electroless Ag plating, electroless Ni plating / electroless Ag plating, electroless Co plating / electroless Ag plating, etc.

[0047] When electroless Ni-P plating, electroless Ni-B plating, electroless Co-P plating, electroless Co-B plating, electroless Ni-Co-P plating, electroless Ni-Co-B plating, electroless Ni-WP plating, electroless Ni-Mo-B plating, electroless Co-WP plating, electroless Co-Mo-B plating, electroless Pd plating, electroless Ni plating, electroless Co plating, etc. are used for the lower layer, it acts as a barrier layer against the diffusion of the underlying metal and is expected to prevent contamination of the metal plating film on the upper layer (outermost layer).

[0048] Furthermore, when electroless Ag plating is used for the upper layer (outermost layer), hillocks are effectively generated, and higher bonding strength can be expected.

[0049] When the metal plating film has a single layer structure, the metal plating film is preferably electroless Ag plating, electroless Au plating, electroless Sn plating, electroless Cu plating, electroless Pd plating, electroless Pt plating, electroless Ru plating, etc., and more preferably electroless Ag plating.

[0050] From the viewpoint of excellent bonding strength, the thickness of the metal plating film is preferably 0.01 μm or more and 20 μm or less, more preferably 0.05 μm or more and 10 μm or less, and even more preferably 0.1 μm or more and 5 μm or less. When the metal plating film has a laminated structure of two or more layers, the thickness of the metal plating film is the total thickness of the laminated structure, and when the metal plating film has a single-layer structure, the thickness of the single layer.

[0051] [2] Manufacturing method for bonded structure The method for producing a bonded structure of the present invention includes the steps of: (1) forming a metal plating film 1 on a structure 1; (2) forming a metal plating film 2 on the structure 2; (3)(i) The metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2) are in contact with each other, or (ii) Between the metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2), (iii) a step of stacking the structure 1 and the structure 2 facing each other; (4) A step of heating the laminate formed in the step (3) to directly bond the metal plating film 1 and the metal plating film 2 together.

[0052] In the method for producing a bonded structure of the present invention, when a substrate silicon wafer () is used as the structures 1 and 2, bumps are formed on the substrate, and a metal plating film is formed on the bumps. The bumps are preferably Cu pillar bumps.

[0053] (1) A step of forming a metal plating film 1 on a structure 1 (2) A step of forming a metal plating film 2 on the structure 2 To form the metal plating film 1 on the structure 1, and to form the metal plating film 2 on the structure 2, plating is performed. Plating can be performed multiple times. The plating method is not particularly limited, and is preferably electrolytic plating (electroplating) and / or electroless plating, and more preferably electroless plating.

[0054] The structure 1 and the structure 2 are preferably made of a material (a material to be plated) on which metal plating can be applied. Examples of the material to be plated include, in addition to Cu, brass, phosphor bronze, and Cu alloys such as Corson alloy, and also Al, Mg, Fe, Ni, Pd, Ag, Au, Co, W, Mo, Pt, Si, and alloys thereof, which are metallic materials on which a metal plating film can be formed by a known technique.

[0055] The metal plating films 1 and 2 preferably have a structure in which a plurality of (that is, two or more layers of) metal plating films are laminated.

[0056] The structure 1, the metal plating film 1, the structure 2, and the metal plating film 2 are as described above.

[0057] For example, a metal layer is formed on the surfaces of the structures 1 and 2 (for example, Cu bumps are formed on a semiconductor chip by electrolytic Cu plating, or a Cu pattern is formed on a ceramic substrate by direct bonding or active metal bonding), and then an electroless Ni-P plating film is formed using an electroless nickel-phosphorus plating (Ni-P plating) bath. In the step of forming the electroless Ni-P plating film on the material to be plated using the electroless Ni-P plating bath, the material to be plated is preferably immersed in the electroless Ni-P plating bath.

[0058] For example, when nickel plating (Ni plating) is formed, it is preferably performed electrolessly. In electroless Ni-P plating, nickel ions are autocatalytically or chemically reduced to nickel, which is then deposited on the substrate, and it can be used on any plated material that can be plated with nickel. The total thickness of the electroless Ni-P plating film is preferably 0.01 μm or more and 20 μm or less.

[0059] Next, the plated material on which the electroless Ni-P plating film is formed can be immersed in an electroless Ag plating bath to perform Ag plating. The thickness of the Ag plating is preferably 0.01 μm or more and 20 μm or less.

[0060] (3) (i) a step of stacking the structures 1 and 2 facing each other so that the metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2) are in contact with each other, or (ii) the metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2) are interposed between them (iii) (forming a laminate); A laminate is produced by stacking structures 1 and 2 such that metal plating film 1 formed on the surface of structure 1 and metal plating film 2 formed on the surface of structure 2 are in contact with each other.

[0061] A laminate is produced by stacking structures 1 and 2 so that metal plating film 1 formed on the surface of structure 1 and metal plating film 2 formed on the surface of structure 2 are interposed between them.

[0062] The bonded structure preferably includes a metal film having a configuration in which a plurality of metal plating films 1 and a plurality of metal plating films 2 are laminated.

[0063] (4) A step of heating the laminate formed in step (3) to directly bond the metal plating film 1 and the metal plating film 2 together. In the direct bonding step, the laminate is heated to bond the metal constituting the metal plating film 1 formed on the surface of the structure 1 and the metal constituting the metal plating film 2 formed on the surface of the structure 2 together.

[0064] The bonding technology utilizes hillocks of plating. A specific embodiment of the invention is a method for directly bonding metal plating films together. The present invention is a method for directly bonding metal plating films formed by plating the surface of a material to be plated (metal or nonmetal), for example, by utilizing hillocks that are generated by heat treatment. Hillocks are hemispherical protrusions that occur on the surface of a thin metal film, and are generated when the thin metal film undergoes local plastic deformation driven by compressive stress applied to the surface of the thin metal film due to heating or the like.

[0065] The temperature at which the laminate is heated is appropriately adjusted based on the materials of the structure 1, the metal plating film 1, the structure 2, and the metal plating film 2, and the laminate is heated and directly bonded at a temperature of preferably 100° C. or more and 400° C. or less, more preferably 150° C. or more and 300° C. or less, and even more preferably 150° C. or more and 250° C. or less. The temperature at which the laminate is heated and directly bonded is preferably 100° C. or more and 400° C. or less. By directly bonding the metal plating films formed on the structures by plating using hillocks generated by heat treatment, good bonding can be achieved even when heated at a low temperature of 250° C. or less.

[0066] The pressure when bonding the laminate is appropriately adjusted based on the materials of the structure 1, the metal plating film 1, the structure 2, and the metal plating film 2, and the laminate is heated and directly bonded, preferably at low pressure or no pressure, in the atmosphere. The pressure when bonding the laminate can be reduced from the pressure when performing direct bonding, preferably to no pressure or a pressure of 1 MPa or less, preferably to no pressure or low pressure: about 0.1 MPa to 0.4 MPa.

[0067] The atmosphere in which the laminate is heated and directly bonded is appropriately adjusted based on the materials of the structure 1, the metal plating film 1, the structure 2, and the metal plating film 2, and may be preferably air or vacuum. The atmosphere in which the laminate is heated and directly bonded may be preferably an inert atmosphere (e.g., argon gas, nitrogen gas, etc.) or a reducing atmosphere (hydrogen gas, formic acid gas, etc.).

[0068] The reaction time for heating the laminate and directly bonding it is appropriately adjusted based on the materials of structure 1, metal plating film 1, structure 2, and metal plating film 2, and is preferably heated and directly bonded for a period of 5 minutes or more and 3 hours or less, more preferably 10 minutes or more and 2 hours or less, and even more preferably 15 minutes or more and 1 hour or less (about 30 minutes).

[0069] The bonding technology of the present invention, which utilizes hillocks of a metal plating film formed by electroless or electrolytic plating, has the following advantages: (i) it is a technology for directly bonding metal plating films to each other using hillocks in the atmosphere, without pressure (low pressure), and at low temperatures (150°C to 250°C, approximately 30 minutes); (ii) it does not require a clean room; (iii) it does not require CMP; (vi) it is applicable to fine Cu pillar bonding because there is no solder bridge and the bonding conditions are low-load; (v) it is expected to be applied to large-area bonding such as heat sinks, DBC substrates, and IC chip bonding; and (vi) electroless or electrolytic plating enables the formation of metal plating films selectively and on large and three-dimensional objects, enabling direct bonding of metal plating films to each other in a wide range of articles and materials. It is a low-load, low-cost direct bonding technology that utilizes hillocks of a metal plating film.

[0070] The present invention does not require a bonding agent (solder or metal sintered material) for bonding, for example, substrates (printed circuit boards, semiconductor wafers, semiconductor chips, etc.), and can directly bond metal plating films together by heat treatment (low temperature: approximately 150°C to 250°C, low pressure: approximately 0.1 MPa to 0.4 MPa, or no pressure, for approximately 30 minutes).

[0071] The bonding technique of the present invention is useful for semiconductor packaging. EXAMPLES

[0072] The present invention will be specifically described below with reference to examples.

[0073] The present invention is not limited to the following specific examples.

[0074] [1] Manufacturing method for bonded structure Example 1 (1) A step of forming a metal plating film 1 on a structure 1 (Sample A) A silicon wafer having Cu pillars (bumps 1) was prepared as structure 1 (substrate), and electroless Ni-P plating of 0.1 μm was selectively (pattern-wise) applied to the Cu pillars, followed by electroless Ag plating of 0.2 μm (metal plating film 1).

[0075] (2) A step of forming a metal plating film 2 on the structure 2 (Sample B) A silicon wafer with Cu plating applied to the entire surface was prepared as structure 2 (substrate), and electroless Ni-P plating of 0.1 μm was applied thereon, followed by electroless Ag plating of 0.2 μm (metal plating film 2).

[0076] (3) (i) a step of stacking the structures 1 and 2 facing each other so that the metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2) are in contact with each other, or (ii) the metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2) are interposed between them (iii) (forming a laminate); The metal plating film of sample A and the metal plating film of sample B were placed on top of each other so as to be in contact with each other (laminate).

[0077] (4) A step of heating the laminate formed in step (3) to directly bond the metal plating film 1 and the metal plating film 2 together. The laminate was subjected to a heat treatment at 250° C. for 30 minutes in an air atmosphere without pressure, to obtain a bonded structure of Example 1.

[0078] (Table 3) When the cross section of the bonded structure of Example 1 was observed with an SEM, it was confirmed that the occurrence of bonding defects (for example, voids or cracks) was suppressed and that the bond was excellent.

[0079] (Examples 2 to 17) The same operations as in Example 1 were carried out to obtain the bonded structures of Examples 2 to 17, except that the electroless Ni-P plating of Sample A and Sample B in Example 1 was changed to the electroless plating bath type described below. When the cross sections of the bonded structures of Examples 2 to 17 were observed by SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the structures were well bonded.

[0080] Example 2: Electroless Ni-B plating Example 3: Electroless Co-P plating Example 4: Electroless Co-B plating Example 5: Electroless Ni-Co-P plating Example 6: Electroless Ni-Co-B plating Example 7: Electroless Ni-WP plating Example 8: Electroless Ni-Mo-B plating Example 9: Electroless Co-WP plating Example 10: Electroless Co-Mo-B plating Example 11: Electroless Fe-B plating Example 12: Electroless In plating Example 13: Electroless Sn plating Example 14: Electroless Pd plating Example 15: Electroless Au plating Example 16: Electroless Pt plating Example 17: Electroless Ru plating

[0081] (Examples 18 to 20) The same operations as in Example 1 were carried out to obtain the bonded structures of Examples 18 to 20, except that the electroless Ag plating of Sample A and Sample B in Example 1 was changed to the electroless plating bath type described below. When the cross sections of the bonded structures of Examples 18 to 20 were observed with an SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the structures were well bonded.

[0082] Example 18: Electroless Au plating Example 19: Electroless Sn plating Example 20: Electroless Cu plating

[0083] Example 21 A joint structure of Example 21 was obtained by carrying out the same operation as in Example 1, except that the thickness of the electroless Ni-P plating of Sample A and Sample B of Example 1 was changed from 0.1 μm to 3.0 μm. When the cross section of the joint structure of Example 21 was observed by SEM, it was confirmed that the occurrence of joint defects was suppressed and that the joint was well joined.

[0084] Example 22 A bonded structure of Example 22 was obtained by carrying out the same operation as in Example 1, except that the thickness of the electroless Ag plating of Sample A and Sample B of Example 1 was changed from 0.2 μm to 1.0 μm. When the cross section of the bonded structure of Example 22 was observed by SEM, it was confirmed that the occurrence of bonding defects was suppressed and bonding was excellent.

[0085] (Example 23) The same operations as in Example 1 were carried out, except that the laminated structure of the metal plating film of Sample A and Sample B in Example 1 was changed to a three-layer structure of electroless Ni-P plating film thickness of 0.1 μm, electroless Pd plating film thickness of 0.1 μm, and electroless Ag plating film thickness of 0.2 μm, to obtain a bonded structure of Example 23. When the cross section of the bonded structure of Example 23 was observed with an SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the bonding was excellent.

[0086] (Example 24) The same operations as in Example 1 were carried out, except that the laminated structure of the metal plating film of Sample A and Sample B in Example 1 was changed to a three-layer structure of electroless Ni-P plating film thickness of 0.1 μm, electroless Co-P plating film thickness of 0.1 μm, and electroless Ag plating film thickness of 0.2 μm, to obtain a joint structure of Example 24. When the cross section of the joint structure of Example 24 was observed by SEM, it was confirmed that the occurrence of joint defects was suppressed and that the joint was well joined.

[0087] (Example 25) A bonded structure of Example 25 was obtained by carrying out the same operation as in Example 1, except that the heat treatment conditions in Example 1 were changed from a heating temperature of 250°C for 30 minutes to a heating temperature of 200°C for 30 minutes. When the cross section of the bonded structure of Example 25 was observed by SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the bond was excellent.

[0088] (Example 26) (Sample A) A silicon wafer with Cu plating applied to the entire surface was prepared as a structure (substrate) (without bumps), and electroless Ni-P plating of 0.1 μm was applied thereon, followed by electrolytic Ag plating of 0.2 μm (metal plating film 1). Two sheets of Sample A were prepared (structures 1 and 2), and the same operation as in Example 1 was carried out to obtain a bonded structure of Example 26. When the cross section of the bonded structure of Example 26 was observed with an SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the bond was excellent.

[0089] Example 27 (Sample A) A silicon wafer with Cu plating applied to the entire surface was prepared as a structure (substrate) (without bumps), and 0.1 μm of Ni electroplating was applied thereon, and then 0.2 μm of Ag electroplating was applied (metal plating film 1). Two sheets of Sample A were prepared (structures 1 and 2), and the same operation as in Example 1 was performed to obtain a bonded structure of Example 27. When the cross section of the bonded structure of Example 27 was observed with an SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the bond was excellent.

[0090] (Example 28) (Sample A) A silicon wafer with Cu plating applied to the entire surface was prepared as a structure (substrate) (without bumps), and 0.1 μm of Co electroplating was applied thereon, and then 0.2 μm of Ag electroplating was applied (metal plating film 1). Two sheets of Sample A were prepared (structures 1 and 2), and the same operation as in Example 1 was performed to obtain a bonded structure of Example 28. When the cross section of the bonded structure of Example 28 was observed with an SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the bond was good.

[0091] (Regarding Examples 1 to 28) When electroless Ni-P plating, electroless Ni-B plating, electroless Co-P plating, electroless Co-B plating, electroless Ni-Co-P plating, electroless Ni-Co-B plating, electroless Ni-WP plating, electroless Ni-Mo-B plating, electroless Co-WP plating, electroless Co-Mo-B plating, electroless Pd plating, electroless Ni plating, electroless Co plating, etc. are used for the lower layer, it acts as a barrier layer against the diffusion of the underlying metal and is expected to prevent contamination of the metal plating film on the upper layer (outermost layer).

[0092] Furthermore, when electroless Ag plating is used for the upper layer (outermost layer), hillocks are effectively generated, and higher bonding strength can be expected.

[0093] (Example 29, Electroless Ag Plating Single Layer Structure) For Sample A and Sample B of Example 1, the same operation as in Example 1 was carried out except that the laminated structure of the metal plating film was changed to a single layer structure of 0.2 μm electroless Ag plating to obtain a bonded structure of Example 29. When the cross section of the bonded structure of Example 29 was observed with an SEM, it was confirmed that no significant bond defects occurred even in the case of a plated single layer structure, and that the bond was acceptable.

[0094] (Example 30, electroless Au plating single layer structure) For Sample A and Sample B of Example 1, the same operation as in Example 1 was carried out except that the laminated structure of the metal plating film was changed to a single-layer structure of 0.2 μm electroless Au plating to obtain a bonded structure of Example 30. When the cross section of the bonded structure of Example 30 was observed with an SEM, it was confirmed that no significant bond defects occurred even in the case of a plated single-layer structure, and that the bond was acceptable.

[0095] (Example 31, electroless Sn plating single layer structure) For Sample A and Sample B of Example 1, the same operation as in Example 1 was carried out except that the laminated structure of the metal plating film was changed to a single-layer structure of 0.2 μm electroless Sn plating to obtain a joint structure of Example 31. When the cross section of the joint structure of Example 31 was observed with an SEM, it was confirmed that no significant joint defects occurred even in the case of a plated single-layer structure, and that the joint was acceptable.

[0096] (Example 32, electroless Cu plating single layer structure) For Sample A and Sample B of Example 1, the same operation as in Example 1 was carried out except that the laminated structure of the metal plating film was changed to a single-layer structure of 0.2 μm electroless Cu plating, to obtain a joint structure of Example 32. When the cross section of the joint structure of Example 32 was observed with an SEM, it was confirmed that no significant joint defects occurred even in the case of a plated single-layer structure, and that the joint was acceptable.

[0097] (Comparative Example 1, no metal plating film) Except for not carrying out the plating treatment, the same operation as in Example 1 was carried out to obtain a bonded structure of Comparative Example 1. (Table 2) When the cross section of the bonded structure of Comparative Example 1 was observed by SEM, it was confirmed that bonding defects had occurred and the bond was not good.

[0098] [Table 1]

[0099] [Table 2]

[0100] [Table 3]

[0101] [2] Industrial Applicability The present invention is a method for directly bonding metal plating films together. The present invention is a method for directly bonding metal plating films together by performing a plating process on the surface of a material to be plated (metal or nonmetal) and utilizing hillocks that are generated by heat treatment.

[0102] The bonding technology of the present invention, which utilizes hillocks of a metal plating film formed by electroless or electrolytic plating, has the following advantages: (i) it is a technology for directly bonding metal plating films to each other using hillocks in the atmosphere, without pressure (low pressure), and at low temperatures (150°C to 250°C, approximately 30 minutes); (ii) it does not require a clean room; (iii) it does not require CMP; (vi) it is applicable to fine Cu pillar bonding because there is no solder bridge and the bonding conditions are low-load; (v) it is expected to be applied to large-area bonding such as heat sinks, DBC substrates, and IC chip bonding; and (vi) electroless or electrolytic plating enables the formation of metal plating films selectively and on large and three-dimensional objects, enabling direct bonding via metal plating films in a wide range of fields of articles and materials. It is a low-load, low-cost direct bonding technology that utilizes hillocks of a metal plating film.

[0103] The present invention does not require a bonding agent (solder or metal sintered material) for bonding, for example, substrates (printed circuit boards, semiconductor wafers, semiconductor chips, etc.), and can directly bond metal plating films together by heat treatment (low temperature: approximately 150°C to 250°C, low pressure: approximately 0.1 MPa to 0.4 MPa, or no pressure, for approximately 30 minutes).

[0104] The bonding technique of the present invention is useful for semiconductor packaging.

Claims

1. A joint structure, The structure 1 and the structure 2 are joined via a metal plating film, The metal plating film has a laminated structure having two or more metal plating film layers, The laminated structure of the metal plating film may be electroless Ni-P plating / electroless Ag plating, electroless Ni-B plating / electroless Ag plating, electroless Co-P plating / electroless Ag plating, electroless Co-B plating / electroless Ag plating, electroless Ni-Co-P plating / electroless Ag plating, electroless Ni-Co-B plating / electroless Ag plating, electroless Ni-WP plating / electroless Ag plating, electroless Ni-Mo-B plating / electroless Ag plating, or electroless Co-WP plating / electroless Ag plating. plating, electroless Co-Mo-B plating / electroless Ag plating, electroless Fe-B plating / electroless Ag plating, electroless In plating / electroless Ag plating, electroless Sn plating / electroless Ag plating, electroless Pt plating / electroless Ag plating, electroless Ru plating / electroless Ag plating, electroless Ni-P plating / electroless Pd plating / electroless Ag plating, electroless Ni-P plating / electroless Co-P plating / electroless Ag plating, or electroless Ni-P plating / electroless Ag plating, bonded structure.

2. 2. The bonded structure according to claim 1, wherein the first structure and the second structure are directly bonded to each other by hillocks via the metal plating film.

3. An article comprising the bonded structure according to claim 1 or 2.

4. The article according to claim 3, wherein the structure 1 and the structure 2 are an IC chip, a printed circuit board, a semiconductor wafer, a semiconductor chip, a bump, a die attach material, a DBA substrate, a DBC substrate, a ceramic substrate, a cooling fin, a heat sink, a lead frame, a passive element, or an iron shaft.

5. A method for manufacturing a bonded structure, comprising the steps of: (1) forming a metal plating film 1 on a structure 1; (2) forming a metal plating film 2 on the structure 2; (3) (i) The metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2) are in contact with each other, or (ii) Between the metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2), (iii) a step of stacking the structure 1 and the structure 2 facing each other to form a laminate; (4) a step of heating the laminate formed in step (3) to directly bond the metal plating film 1 and the metal plating film 2 to each other by generating hillocks in the metal plating film, The metal plating film 1 and the metal plating film 2 form a laminated structure having two or more metal plating films, The laminated structure of the metal plating film may be electroless Ni-P plating / electroless Ag plating, electroless Ni-B plating / electroless Ag plating, electroless Co-P plating / electroless Ag plating, electroless Co-B plating / electroless Ag plating, electroless Ni-Co-P plating / electroless Ag plating, electroless Ni-Co-B plating / electroless Ag plating, electroless Ni-WP plating / electroless Ag plating, electroless Ni-Mo-B plating / electroless Ag plating, or electroless Co-WP plating / electroless Ag plating. plating, electroless Co-Mo-B plating / electroless Ag plating, electroless Fe-B plating / electroless Ag plating, electroless In plating / electroless Ag plating, electroless Sn plating / electroless Ag plating, electroless Pt plating / electroless Ag plating, electroless Ru plating / electroless Ag plating, electroless Ni-P plating / electroless Pd plating / electroless Ag plating, electroless Ni-P plating / electroless Co-P plating / electroless Ag plating, or electroless Ni-P plating / electroless Ag plating, A method for manufacturing a bonded structure.

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