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

direct bonding

[0001] The present invention relates to direct bonding.

[0002] In the process of mounting a semiconductor element, the semiconductor element and the substrate are bonded together using 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, wherein the metal constituting the metal film diffuses due to stress migration, and the substrate and the semiconductor element are bonded via the metal film. Patent Document 1 also discloses a bonded structure including, in this order, a substrate, a first metal film, a thermal stress absorption material, a second metal film, and a semiconductor element, wherein at least one of the metal constituting the first metal film and the metal constituting the second metal film diffuses due to stress migration, and the substrate and the thermal stress absorption material are bonded via the first metal film, and the semiconductor element and the thermal stress absorption material are bonded via the second metal film.

[0004] Patent No. 6284164

[0005] An object of the present invention is to provide a new technology for manufacturing a bonded structure by direct bonding.

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

[0007] Conventional hybrid bonding technology requires high loads and costs, such as (i) a vacuum, pressureless, high-temperature (300-400°C, 2 hours) bonding technology, (ii) a clean room, (iii) planarization by CMP (Chemical Mechanical Polishing), and (vi) expensive bonding equipment. In addition, the high-load bonding conditions make it difficult to apply to fine Cu pillar bonding.

[0008] Conventionally (Patent Document 1), direct bonding utilizing stress migration was possible using a metal film (Ag or Cu) formed by sputtering, 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] Item 1. A joined structure in which a structure 1 and a structure 2 are joined via a metal plating film.

[0011] Item 2. The bonded structure according to Item 1, wherein a metal plating film 1 is provided on the structure 1, a metal plating film 2 is provided on the structure 2, and the structure 1 and the structure 2 are bonded together via the metal plating film 1 and the metal plating film 2.

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

[0013] Item 4. A method for manufacturing a bonded structure, comprising: (1) a step of forming a metal plating film 1 on structure 1; (2) a step of forming a metal plating film 2 on structure 2; (3) a step of (i) stacking structure 1 and structure 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) a step of stacking structure 1 and structure 2; and (4) a step of heating the stack formed in step (3) to directly bond the metal plating film 1 and the metal plating film 2.

[0014] The bonding technology of the present invention, which utilizes hillocks in metal plating films formed by electroless or electrolytic plating, has the following advantages: (i) it is a technology that directly bonds metal plating films together using hillocks in the atmosphere, without pressure (low pressure), and at low temperatures (150°C to 250°C, for 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 are no solder bridges and the bonding conditions are low-load; (v) it is expected to be applicable 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 for a wide range of articles and materials. It is a low-load, low-cost direct bonding technology that utilizes hillocks in metal plating films.

[0015] The present invention does not require a bonding agent (solder or metal sintering material) for bonding, for example, substrates (printed circuit boards, semiconductor wafers, semiconductor chips, etc.), and allows metal plating films to be directly bonded to each other 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.

[0017] The present invention can provide a new manufacturing technique for a bonded structure using direct bonding.

[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 that encompass all of "comprise," "consist essentially of," and "consist only of."

[0021] In this specification, when a numerical range is expressed as "A to B," it means "not less than A and not more than B."

[0022] In this specification, the expressions parts, % and the like are generally used.

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

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

[0025] In the bonded structure of the present invention, structure 1 and structure 2 are bonded 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 technology for bonding metal plating films formed by electroless or electrolytic plating. Because electroless or electrolytic plating enables selective formation of metal plating films on large and three-dimensional objects, the direct bonding technology of the present invention enables direct bonding via metal plating films on articles in a wide range of fields.

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

[0029] The structures 1 and 2 are preferably made of a material (plating target material) that can be metal plated. Examples of the plating target material include Cu, brass, phosphor bronze, and Cu alloys such as Corson alloy, as well as Al, Mg, Fe, Ni, Pd, Ag, Au, Co, W, Mo, Pt, Si, and alloys thereof, on which a metal plating film can be formed by known techniques.

[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 performing a plating process on the surface of a plated material (metal or non-metal) 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 multiple metal plating films.

[0034] The bonded 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 bonded via metal plating film 1 and 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] Furthermore, elements corresponding to the components of the plating solution are codeposited 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 codeposited in the metal plating film.

[0037] The metal plating film has a single layer configuration or a laminate configuration of multiple 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 in which two or more metal plating films are laminated. 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 bonded structure may be produced by forming a nickel and silver laminate structure on structures 1 and 2, and then laminating structure 2 on structure 1 so that the silver layers of each laminate structure are in contact with each other.

[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, electroless Ni plating, electroless Co plating, electroless 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, electroless Ni plating, electroless 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, or the like.

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

[0046] The laminated structure of a plurality of metal plating films (lower metal plating film / upper metal plating film) is even 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 It is a layered structure of metal plating films including 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 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 as the lower layer, it acts as a barrier layer to the diffusion of the underlying metal, and is expected to prevent contamination of the upper (outermost) metal plating film.

[0048] Furthermore, if electroless Ag plating or the like is used for the upper layer (outermost layer), hillocks are generated effectively, 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] Method for manufacturing a bonded structure The method for manufacturing a bonded structure of the present invention includes: (1) a step of forming a metal plating film 1 on structure 1; (2) a step of forming a metal plating film 2 on structure 2; (3) a step of stacking structures 1 and 2 so that (i) metal plating film 1 formed in step (1) and metal plating film 2 formed in step (2) are in contact with each other, or (ii) metal plating film 1 formed in step (1) and metal plating film 2 formed in step (2) are sandwiched between them; (iii) a step of stacking structures 1 and 2 facing each other; and (4) a step of heating the laminate formed in step (3) to directly bond metal plating film 1 and metal plating film 2.

[0052] In the method for manufacturing a bonded structure of the present invention, when a substrate silicon wafer () is used as 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) Step of forming metal plating film 1 on structure 1 (2) Step of forming metal plating film 2 on structure 2 To form metal plating film 1 on structure 1 and to form metal plating film 2 on 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, more preferably electroless plating.

[0054] The structures 1 and 2 are preferably made of a material (plating target material) that can be metal plated. Examples of the plating target material include Cu, brass, phosphor bronze, and Cu alloys such as Corson alloy, as well as Al, Mg, Fe, Ni, Pd, Ag, Au, Co, W, Mo, Pt, Si, and alloys thereof, on which a metal plating film can be formed by known techniques.

[0055] The metal plating films 1 and 2 preferably have a structure in which a plurality of (i.e., 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. The step of forming the electroless Ni-P plating film on the material to be plated using the electroless Ni-P plating bath preferably involves immersing the material to be plated in the electroless Ni-P plating bath.

[0058] For example, when forming nickel plating (Ni plating), 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. This method can be used on any substrate 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] The substrate on which the electroless Ni-P plating film is formed is then 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 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) come into contact with each other, or (ii) a step of stacking 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) come into contact with each other, or (iii) a step of stacking structures 1 and 2 facing each other (forming a laminate). A laminate is produced by stacking structures 1 and 2 so that the metal plating film 1 formed on the surface of structure 1 and the metal plating film 2 formed on the surface of structure 2 come into 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 stacked.

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

[0064] The bonding technology utilizes plating hillocks. Specifically, the present invention is a method for directly bonding metal plating films together. For example, the present invention is a method for directly bonding metal plating films formed by plating the surface of a substrate (metal or nonmetal) using hillocks that are generated by heat treatment. Hillocks are hemispherical protrusions that appear on the surface of a thin metal film. They are formed when the thin metal film undergoes local plastic deformation driven by compressive stress applied to the surface by heating or other factors.

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

[0066] The pressure when bonding the laminates is adjusted appropriately based on the materials of structure 1, metal plating film 1, structure 2, and metal plating film 2, and the laminates are heated and directly bonded, preferably at low or no pressure, in the atmosphere. The pressure when bonding the laminates can be reduced from the pressure used when performing direct bonding, preferably to no pressure or a pressure of 1 MPa or less, and preferably to no pressure or a low pressure of 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 preferably be air or vacuum. The atmosphere in which the laminate is heated and directly bonded may preferably be 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 adjusted appropriately based on the materials of structure 1, metal plating film 1, structure 2, and metal plating film 2, and is preferably 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 (approximately 30 minutes).

[0069] The bonding technology of the present invention, which utilizes hillocks in metal plating films formed by electroless or electrolytic plating, has the following advantages: (i) it is a technology that directly bonds metal plating films together using hillocks in the atmosphere, without pressure (low pressure), and at low temperatures (150°C to 250°C, for 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 are no solder bridges and the bonding conditions are low-load; (v) it is expected to be applicable 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, making it possible to directly bond metal plating films together for a wide range of articles and materials. It is a low-load, low-cost direct bonding technology that utilizes hillocks in metal plating films.

[0070] The present invention does not require a bonding agent (solder or metal sintering material) for bonding, for example, substrates (printed circuit boards, semiconductor wafers, semiconductor chips, etc.), and allows metal plating films to be directly bonded to each other 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.

[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] Method for manufacturing bonded structure (Example 1) (1) Step of forming metal plating film 1 on 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) Step of forming metal plating film 2 on 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 structures 1 and 2 facing each other (forming a laminate) so that the metal plating film 1 formed in step (1) and the metal plating film 2 formed in step (2) come into 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) come into contact with each other, or (iii) the structure 1 and the structure 2 are stacked facing each other (forming a laminate).The metal plating films of sample A and sample B were stacked so that they came into contact with each other (laminate).

[0077] (4) A step of heating the laminate formed in step (3) and directly bonding the metal plating film 1 and the metal plating film 2. The laminate was subjected to a heat treatment at 250°C for 30 minutes in an air atmosphere without applying 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 following electroless plating bath type. When the cross sections of the bonded structures of Examples 2 to 17 were observed with an 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 following electroless plating bath type. 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) The same operation as in Example 1 was performed, except that the thickness of the electroless Ni-P plating on Sample A and Sample B in Example 1 was changed from 0.1 μm to 3.0 μm, to obtain a bonded structure of Example 21. When the cross section of the bonded structure of Example 21 was observed with an SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the bond was good.

[0084] (Example 22) The same operation as in Example 1 was performed, except that the thickness of the electroless Ag plating film on Sample A and Sample B in Example 1 was changed from 0.2 μm to 1.0 μm, to obtain a bonded structure of Example 22. When the cross section of the bonded structure of Example 22 was observed with an SEM, it was confirmed that the occurrence of bonding defects was suppressed and that the bond was good.

[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 bonding was good.

[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 bonded structure of Example 24. When the cross section of the bonded structure of Example 24 was observed with an SEM, it was confirmed that the occurrence of bonding defects was suppressed and that bonding was good.

[0087] Example 25 The same operation as in Example 1 was performed, 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, to obtain a bonded structure of Example 25. When a 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 bonded structure was good.

[0088] (Example 26) (Sample A) A silicon wafer with Cu plating on the entire surface was prepared as a structure (substrate) (no 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 performed to obtain the bonded structure of Example 26. SEM observation of the cross section of the bonded structure of Example 26 confirmed that the occurrence of bonding defects was suppressed and that the structure was well bonded.

[0089] (Example 27) (Sample A) A silicon wafer with Cu plating on the entire surface was prepared as a structure (substrate) (no bumps), and 0.1 μm of Ni electroplating was applied thereon, followed by 0.2 μm of Ag electroplating (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 the bonded structure of Example 27. SEM observation of the cross section of the bonded structure of Example 27 confirmed that the occurrence of bonding defects was suppressed and that the bond was good.

[0090] (Example 28) (Sample A) A silicon wafer with Cu plating on the entire surface was prepared as a structure (substrate) (no bumps), and 0.1 μm of Co electroplating was applied thereon, followed by 0.2 μm of Ag electroplating (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 the bonded structure of Example 28. SEM observation of the cross section of the bonded structure of Example 28 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, or the like is used as the lower layer, it acts as a barrier layer against the diffusion of the underlying metal, and is expected to be effective in preventing contamination of the metal plating film of the upper layer (outermost layer).

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

[0093] (Example 29, electroless Ag-plated 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 of 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 major bond defects occurred, even with the plated single layer structure, and that the bond was acceptable.

[0094] (Example 30, electroless Au-plated 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 of 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 major bond defects occurred, even with the plated single layer structure, and that the bond was acceptable.

[0095] (Example 31, electroless Sn-plated 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 bonded structure of Example 31. When the cross section of the bonded structure of Example 31 was observed with an SEM, it was confirmed that no major bond defects occurred even with the plated single layer structure, and that the bond was acceptable.

[0096] (Example 32, Electroless Cu-plated 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 of electroless Cu plating, to obtain a bonded structure of Example 32. When the cross section of the bonded structure of Example 32 was observed with an SEM, it was confirmed that no major bond defects occurred, even with the plated single-layer structure, and that the bond 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 with an SEM, it was confirmed that bonding defects had occurred and the bond was not good.

[0098]

[0099]

[0100]

[0101] [2] Industrial Applicability The present invention is a method for direct bonding between metal plating films. The method involves plating the surface of a substrate (metal or nonmetal) and directly bonding the formed metal plating films together by utilizing hillocks that are generated by heat treatment.

[0102] The bonding technology of the present invention, which utilizes hillocks in metal plating films formed by electroless or electrolytic plating, has the following advantages: (i) it is a technology that directly bonds metal plating films together using hillocks in the atmosphere, without pressure (low pressure), and at low temperatures (150°C to 250°C, for 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 are no solder bridges and the bonding conditions are low-load; (v) it is expected to be applicable 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, making it possible to directly bond metal plating films together for a wide range of articles and materials. It is a low-load, low-cost direct bonding technology that utilizes hillocks in metal plating films.

[0103] The present invention does not require a bonding agent (solder or metal sintering material) for bonding, for example, substrates (printed circuit boards, semiconductor wafers, semiconductor chips, etc.), and allows metal plating films to be directly bonded to each other 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 lower metal plating film of the laminate structure is 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, or electric Co plating; A bonded structure, wherein the upper metal plating film of the laminated structure is electroless Ag plating.

2. A metal plating film 1 is provided on the structure 1, A metal plating film 2 is provided on the structure 2, the structure 1 and the structure 2 are bonded to each other via the metal plating film 1 and the metal plating film 2, 2. The joint structure according to claim 1, wherein the first metal plating film and the second metal plating film form a laminated structure having two or more layers of metal plating films.

3. The laminate 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, electroless Co-WP plating / electroless Ag plating, electroless Co-Mo-B plating / electroless Ag plating, electroless Fe-B plating / electroless 2. The bonded structure according to claim 1, wherein the bonded structure is 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, or electroless Co plating / electroless Ag plating.

4. 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 a metal plating film.

5. An article comprising the bonded structure according to any one of claims 1 to 4.

6. The article according to claim 5, 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.

7. 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) stacking the structure 1 and the structure 2 facing each other; (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 lower metal plating film of the laminate structure is 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, or electric Co plating; A method for producing a bonded structure, wherein the upper metal plating film of the laminated structure is electroless Ag plating.

8. 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, electroless Co-WP plating / electroless Ag plating, electroless Co-Mo-B plating / electroless Ag plating, electroless Fe-B plating / electroless Ag plating, 8. The method for producing a bonded structure according to claim 7, wherein the bonding is performed by electroless 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, or electroless Co plating / electroless Ag plating.

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