Bonding film, semiconductor module, inverter, electronic device, and method for manufacturing semiconductor module

Abstract

The present invention relates to a bonding film (1) comprising a metal layer (1b), a first bonding layer (1a) disposed on one surface of the metal layer (1b), and a second bonding layer (1a) disposed on the other surface of the metal layer (1b), wherein the metal layer (1b) contains a metal having a thermal conductivity of at least 100 W / m·K at a temperature of 300 K, and the metal layer (1b) has a 0.2% proof stress of at most 250 MPa.

Description

Bonding film, semiconductor module, inverter, electronic device, and method for manufacturing semiconductor module

[0001] The present invention relates to a bonding film, and to a semiconductor module, an inverter, an electronic device, and a method for manufacturing a semiconductor module, each using the bonding film.

[0002] In recent years, wide-gap semiconductors such as SiC and GaN, which operate at high temperatures of 200° C. or higher, have been attracting attention. As a method for bonding semiconductor chip elements in such semiconductors, for example, a bonding material containing Cu and Sn is heated to a temperature above the melting point of Sn to bond the Cu ６ Sn ５ and Cu ３ A joining method called transient liquid phase sintering (TLPS) has been proposed, which forms an intermetallic compound containing Sn (see, for example, Patent Document 1).

[0003] In the method for manufacturing a semiconductor module disclosed in Patent Document 1, a solder containing Sn is interposed between a first soldering base material containing Cu, which is the joining surface of a semiconductor chip element, and a second soldering base material containing Cu, which is the joining surface of a substrate, and heated at a temperature higher than the melting point of Sn, thereby causing transient liquid phase sintering of the Cu contained in each soldering base material and the Sn contained in the solder, thereby forming a connection layer containing an intermetallic compound copper-tin phase.

[0004] However, the connection layer for joining the semiconductor chip and the substrate described in Patent Document 1 is a brittle material, a Cu-Sn intermetallic compound, so when the semiconductor chip and / or the substrate are repeatedly heated and cooled, the stress caused by the difference in thermal expansion between the two cannot be sufficiently alleviated, and cracks occur in the connection layer that run vertically from the substrate to the bonding layer. Furthermore, if these cracks propagate from the substrate to the semiconductor chip element, there is a risk of damaging the semiconductor chip element, which is an electronic component.

[0005] Patent Document 2 discloses a bonding sheet in which a rolled coating layer of a paste containing Cu and Sn is provided on each side of a core sheet made of Cu or Al. This bonding sheet is manufactured by applying a paste containing Cu and Sn to each side of a core sheet made of Cu or Al, drying the paste to form a dry layer, and then pressure-molding the core sheet and the dry layers formed on each side of the core sheet together to provide a rolled coating layer of the paste on each side of the core sheet.

[0006] On the other hand, when a semiconductor module repeatedly switches on and off, causing the semiconductor chip element and / or substrate to repeatedly heat and cool, the thermal strain stress applied to the bonding material increases with higher operating temperatures, which can cause cracks to form inside the bonding material, resulting in concerns about a shortened element life and increased thermal resistance. In the semiconductor module disclosed in Patent Document 2, a Kovar substrate and a semiconductor chip element are bonded via a bonding layer, and bonded materials with relatively small differences in linear expansion coefficients are used as the electronic component and the substrate. However, when the commonly used Cu substrate and Si chip are used as the bonded materials, the thermal strain stress caused by the difference in linear expansion coefficients between the two cannot be alleviated, causing cracks to form in the bonding layer, which can lead to increased thermal resistance and element damage.

[0007] Patent Document 3 discloses a joint structure having a joint between a first member such as a semiconductor element and a second member such as a metal electrode or wiring, in which the joint includes a joining layer containing an intermetallic compound of a first metal such as Ni or Cu and a second metal such as Sn, and a relaxation layer made of Al or an Al alloy and having a notch. The relaxation layer has a notch for inducing cracks into the relaxation layer, which induces cracks in the relaxation layer and prevents the cracks from occurring or progressing near the joint.

[0008] Furthermore, when manufacturing a semiconductor device including a semiconductor chip on which a wide bandgap semiconductor element is formed, a dicing process is performed to divide a semiconductor wafer on which an integrated circuit is formed into individual chips. Therefore, it is desirable to develop a bonding material that exhibits good dicing performance while mitigating thermal distortion stress caused by differences in the linear expansion coefficients of the bonded materials.

[0009] JP 2012-74726 A JP 2019-135734 A JP 2020-136336 A

[0010] The present invention aims to provide a bonding film that prevents cracks caused by thermal strain stress applied to the inside and exhibits good dicing performance, as well as a semiconductor module, inverter, electronic device, and method for manufacturing a semiconductor module that use the same.

[0011] A bonding film according to an embodiment of the present invention comprises a metal layer, a first bonding layer provided on one surface of the metal layer, and a second bonding layer provided on the other surface of the metal layer, wherein the metal layer contains a metal having a thermal conductivity of 100 W / m·K or more at a temperature of 300 K, and the metal layer has a 0.2% yield strength of 250 MPa or less.

[0012] A semiconductor module according to an embodiment of the present invention comprises the bonding film, a first bonded material bonded to the first bonding layer, and a second bonded material bonded to the second bonding layer, wherein the first bonded material is an electronic component, and the second bonded material is a metal substrate or a metal lead frame.

[0013] An inverter according to an embodiment of the present invention is equipped with the semiconductor module.

[0014] An electronic device according to an embodiment of the present invention is equipped with the inverter.

[0015] In an embodiment of the present invention, a method for manufacturing a semiconductor module includes a step of bonding the electronic component to the metal substrate or metal lead frame via the bonding film by heating the electronic component to the metal substrate or metal lead frame at a temperature of 230°C to 350°C for 1 to 20 minutes in an inert or reducing atmosphere with the bonding film interposed between the electronic component and the metal substrate or metal lead frame.

[0016] According to the present invention, it is possible to provide a bonding film that prevents the occurrence of cracks due to thermal strain stress applied to the inside and exhibits good dicing performance, as well as a semiconductor module, an inverter, an electronic device, and a method for manufacturing a semiconductor module that use the same.

[0017] Fig. 1 is a schematic cross-sectional view showing an example of a dicing die bonding film using the bonding film of the present invention. Fig. 2 is a schematic cross-sectional view showing an example of a semiconductor module produced using the bonding film of the present invention. Fig. 3 is a schematic cross-sectional view showing a mounted sample of a semiconductor module produced using the bonding film of Comparative Example 1.

[0018] [Bonding Film] The bonding film according to the present invention comprises a metal layer, a first bonding layer provided on one surface of the metal layer, and a second bonding layer provided on the other surface of the metal layer. That is, the bonding film has a multilayer structure in which the metal layer is provided between the first bonding layer and the second bonding layer, and the metal layer is arranged as a stress-relieving intermediate layer. The first bonding layer is provided as one bonding surface of the bonding film to be bonded to a first bonded material (described later), and the second bonding layer is provided as one bonding surface of the bonding film to be bonded to a second bonded material (described later). In this way, the bonding film functions as a bonding material that bonds the first bonded material and the second bonded material. Because a metal layer having predetermined properties is inserted as an intermediate layer in the bonding film, when a semiconductor module is produced in which the bonding film is bonded to each of the bonded materials having different linear expansion coefficients, such as a silicon semiconductor chip element and a copper substrate, even if heat is applied to the bonding film, the thermal strain stress acting inside the bonding film due to the difference in linear thermal expansion between the bonded materials, such as the semiconductor chip element and the copper substrate, is absorbed by the elastic deformation or plastic deformation of the metal layer. As a result, cracks can be prevented from occurring inside the bonding film, and a decrease in the lifespan of the elements and an increase in thermal resistance can be suppressed.

[0019] <Metal Layer> The metal layer contains a metal having a thermal conductivity of 100 W / m·K or more at a temperature of 300 K. This makes it easier to establish thermal and electrical conduction paths than in a structure in which the bonding layer is a single layer, and also improves the thermal and electrical conductivity of the bonding film. Examples of such metals include copper (Cu), zinc (Zn), aluminum (Al), silver (Ag), gold (Au), magnesium (Mg), aluminum alloys, copper alloys, and zinc alloys. Copper (Cu), zinc (Zn), aluminum (Al), aluminum alloys, copper alloys, or zinc alloys are preferred, and copper (Cu), zinc (Zn), or aluminum (Al) are more preferred.

[0020] The metal layer has a 0.2% yield strength of 250 MPa or less. This allows the metal layer to deform preferentially over the bonding layers provided on both sides thereof. For example, when a semiconductor module is produced in which a bonding film is bonded to each of the bonding materials, such as semiconductor chip elements and substrates, which have different linear expansion coefficients, the stress applied to the inside of the bonding film is alleviated, preventing damage to the semiconductor module. The 0.2% yield strength of the metal layer is preferably 250 MPa or less, more preferably 120 MPa or less, and even more preferably 50 MPa or less. On the other hand, the lower limit of the 0.2% yield strength is preferably 5 MPa or more in order to impart a certain degree of deformation resistance to the metal layer (to impart a certain degree of deformation resistance and ensure ease of handling during manufacturing).

[0021] The shape of the metal layer may be, for example, foil, mesh, fiber, pellet, or the like, with foil being preferred. In particular, by using a metal foil having a foil-like shape, the bonding film can be applied to small, highly reliable power semiconductor modules. The metal layer may also be a metal foil that has been perforated or textured. By using such processed metal foil, the deformation resistance of the metal layer, such as elastic deformation and plastic deformation, is reduced, thereby enabling the 0.2% yield strength to be further reduced. The metal layer may also be a metal foil that has been softened in advance by heat treatment. In this case, the heating temperature is preferably 200°C to 700°C, more preferably 400°C to 600°C. The heating time is preferably 1 minute to 90 minutes, more preferably 30 minutes to 60 minutes. Furthermore, the metal foil may be both softened by heat treatment and perforated or textured.

[0022] Furthermore, when the metal layer is a perforated metal foil, the porosity is preferably 5% to 70% of the entire surface of the metal foil, and more preferably 15% to 55%. In particular, a porosity of 30% to 45% reduces the 0.2% yield strength of the metal layer, improving dicing performance without significantly impairing thermal conductivity. Furthermore, even when heat is applied to the metal layer, the metal layer is more susceptible to elastic and plastic deformation, which makes it easier to prevent cracks caused by thermal strain stress inside the bonding film and improves reliability in high-temperature operation. The width (diameter) of the perforations is not particularly limited, but is preferably 0.05 mm to 5 mm, and more preferably 0.1 mm to 0.5 mm.

[0023] The thickness of the metal layer is preferably 8 μm or more and 200 μm or less, and more preferably 9 μm or more and 100 μm or less. In particular, when the thickness of the metal layer is 10 μm or more and 20 μm or less, the bonding film becomes easy to process, thereby improving dicing performance. In addition, it is also effective for application as a bonding film for smaller semiconductor modules.

[0024] <Bonding layer> In the bonding film according to the present invention, a first bonding layer and a second bonding layer are provided on both sides of the metal layer so that the above-mentioned metal layer is interposed in the bonding layer as a stress relief layer. The first bonding layer and the second bonding layer each preferably contain at least one type of metal particle (P) as a metal component. The materials of the first bonding layer and the second bonding layer, i.e., the metal particles (P) contained in the first bonding layer and the second bonding layer, may be the same or different, but from the viewpoints of productivity, connectivity with the metal layer, etc., it is preferable that they are the same.

[0025] The first and second bonding layers are preferably paste layers formed using a paste-like conductive composition. Such a conductive composition contains at least one type of metal particles (P), a thermosetting resin, a flux, and a solvent, and may further contain various additives as needed. The first and second bonding layers are produced by forming a coating film by applying such a paste-like conductive composition and drying the coating film.

[0026] (Metal Particles) The metal particles (P) as the metal component preferably contain, for example, first metal particles (P1) made of one metal selected from the group consisting of copper (Cu), nickel (Ni), silver (Ag) and gold (Au) or an alloy containing two or more metals selected from these groups. Such first metal particles (P1) have excellent electrical conductivity and thermal conductivity, making them suitable as the metal particles (P) of the conductive composition described below. In particular, they are preferably Cu particles or alloy particles containing Cu, which are inexpensive and have excellent thermal conductivity.

[0027] In addition to the first metal particles (P1), the metal particles (P) may further include second metal particles (P2) having a metal element different from that of the first metal particles (P1). In this case, the metal particles (P) preferably include the first metal particles (P1) and the second metal particles (P2), and the first metal particles (P1) and the second metal particles (P2) each contain a metal component capable of forming an intermetallic compound with each other. Since the first metal particles (P1) and the second metal particles (P2) each contain a metal capable of forming an intermetallic compound with each other, the metal particles (P) as a whole are a low-melting-point metal or alloy in the unsintered state, but can form a high-melting-point intermetallic compound after sintering. As a result, such metal particles can achieve lower mounting temperatures while exhibiting excellent heat resistance without performance degradation even at temperatures above the mounting temperature after sintering.

[0028] The second metal particles (P2) may contain a metal element different from the first metal particles (P1) and capable of forming an intermetallic compound with the first metal particles (P1). The second metal particles (P2) are not particularly limited, but are preferably made of one metal selected from the group consisting of aluminum (Al), tin (Sn), zinc (Zn), titanium (Ti), indium (In), bismuth (Bi), gallium (Ga), and palladium (Pd), or an alloy containing two or more metals selected from this group. Specifically, for example, when the first metal particles (P1) are Cu particles, the second metal particles (P2) are preferably metal particles capable of forming an intermetallic compound with Cu, such as Sn particles or alloy particles containing Sn.

[0029] The combination of the first metal particles (P1) and the second metal particles (P2) capable of forming such an intermetallic compound can be appropriately selected, but it is preferable that an intermetallic compound such as Cu—Sn, Ni—Sn, Ag—Sn, Cu—Zn, Ni—Zn, or Ni—Ti can be formed. When it is necessary to set the mounting temperature as low as possible, it is preferable that the second metal particles (P2) contain low-melting-point Sn, and a Cu—Sn combination is particularly preferable. In order to form such a Cu—Sn intermetallic compound, it is preferable that the first metal particles (P1) are Cu particles and the second metal particles (P2) are Sn particles or Sn-based solder particles.

[0030] The content of the first metal particles (P1) in each of the first bonding layer and the second bonding layer is preferably 59% by mass or less, more preferably 58% by mass or less, and even more preferably 57% by mass or less. The lower limit of the content of the first metal particles (P1) is preferably 54% by mass or more, and more preferably 56% by mass or more. By having the content of the first metal particles (P1) be 59% by mass or less, the thermal conductivity of the first bonding layer and the second bonding layer is further improved. The contents of the first metal particles (P1) in the first bonding layer and the second bonding layer may be the same or different.

[0031] The content of the second metal particles (P2) in each of the first bonding layer and the second bonding layer is preferably 32% by mass or more and 41% by mass or less, and more preferably 35% by mass or more and 37% by mass or less.

[0032] From the viewpoint of reducing the environmental load, it is preferable that the metal components are substantially free of Pb (lead), Hg (mercury), Ab (antimony), and As (arsenic), and the total content of these metals in the entire metal components is preferably less than 0.1 mass%.

[0033] The shape of the metal particles (P) is not particularly limited, and spherical particles, dendritic particles, scale-like particles, spike-like particles, etc. can be used as appropriate. The particle size of the metal particles (P) is also not particularly limited, but the average particle size (D50) of the first metal particles (P1) is preferably 15 μm or less, and the average particle size (D50) of the second metal particles (P2) is more preferably 15 μm or less. In the present invention, the average particle size (D50) is a value calculated based on measurement by a laser diffraction / scattering particle size distribution measurement method.

[0034] The content of the metal component in the conductive composition is preferably 70 to 96 mass %, more preferably 80 to 94 mass %. By having the content of the metal component in this range, the formability when forming a bonding film is improved, the handling property as a film is good, and further, excellent conductivity can be exhibited after bonding and sintering.

[0035] (Thermosetting resin) The conductive composition contains at least one thermosetting resin as a binder component. When a bonding film is produced using the conductive composition, the inclusion of the thermosetting resin in the conductive composition contributes to film properties (ease of molding, ease of handling, etc.) in an unsintered state, and after sintering, it can relieve stress and the like that occurs between materials to be joined (for example, electronic components such as semiconductor elements) and metal substrates or metal lead frames, etc., due to a heat cycle.

[0036] In particular, from the viewpoint of heat resistance and film properties when mixed with metal particles (P), the thermosetting resin preferably contains a maleic acid imide compound containing two or more imide group units per molecule. Examples of resins containing such maleic acid imide compounds containing two or more imide group units per molecule include maleic acid imide resins (hereinafter sometimes referred to as "maleimide resins"). In particular, thermosetting resins containing the above-mentioned maleic acid imide resins have excellent stress relaxation properties, and therefore can improve the thermal fatigue resistance of the conductive composition after sintering.

[0037] The maleic acid imide resin can be obtained, for example, by condensing maleic acid or its anhydride with a diamine or polyamine. From the viewpoint of stress relaxation, the maleic acid imide resin preferably contains a skeleton derived from an aliphatic amine having 10 or more carbon atoms, and more preferably has a skeleton having 30 or more carbon atoms and represented by the following structural formula (1). The number average molecular weight of the maleic acid imide resin is preferably 3,000 or more.

[0038]

[0039] The maleic acid imide resin may contain a skeleton derived from an acid component other than maleic acid, such as benzenetetracarboxylic acid or its anhydride, or hydroxyphthalic acid bisether or its anhydride, to adjust the molecular weight, glass transition temperature Tg, etc.

[0040] As such maleic acid imide resins, for example, bismaleimide resins represented by the following structural formulas (2) to (4) are preferably used.

[0041]

[0042] In the above formula (3), n is an integer of 1 to 10. In the above formulas (2) to (4), the portion "X" is "C" represented by the following structural formula (6). ３６ H ７２ In the following formula (5), "*" indicates the bonding site with N.

[0043]

[0044] The content of the thermosetting resin in the conductive composition is preferably 4% by mass or more and 30% by mass or less, more preferably 6% by mass or more and 20% by mass or less. The thermosetting resin may be a single thermosetting resin, or two or more thermosetting resins may be used in combination. If necessary, the conductive composition may further contain a thermosetting resin other than those mentioned above, such as a phenolic resin, novolak (phenol and / or cresol), polyurethane resin, polyimide resin, cyanate ester resin, polyvinyl alcohol resin, polyester resin, polyurea resin, benzoxazine resin, acrylate resin, cyanate ester resin, and / or a combination thereof.

[0045] (Flux) The conductive composition may further contain a flux having one or more phosphorus or sulfur atoms in its molecular structure that can bond with oxygen atoms without generating water. The flux has the function of removing oxide films from the surfaces of metal particles (P) contained in the conductive composition, and is particularly effective on easily oxidized metals such as copper, tin, nickel, and aluminum. Organic phosphines, sulfide-based compounds, and thiol-based compounds are preferred as such fluxes. These compounds are significantly less prone to absorbing moisture and have excellent moisture absorption resistance compared to commonly used fluxes such as carboxylic acids and alcohols.

[0046] The flux preferably contains at least one of an organic phosphine represented by the following general formula (6), a sulfide compound represented by the following general formula (7), and a thiol compound represented by the following general formula (8): However, R in the following general formulas (6) and (7) each independently represents an organic group and may be the same or different.

[0047]

[0048] In the above general formulas (6), (7), and (8), it is preferable that each R is independently selected from an alkyl group, an aryl group, an organic group having a functional group, an organic group having a heteroatom, and an organic group having an unsaturated bond, and it is preferable that at least one R is an aryl group.

[0049] The alkyl group may be linear, branched, or cyclic, and may have a substituent. The alkyl group is preferably linear or branched. The alkyl group preferably has 3 or more carbon atoms, more preferably 4 to 18 carbon atoms, and even more preferably 6 to 15 carbon atoms. Examples of such alkyl groups include propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, stearyl, and isostearyl groups.

[0050] The aryl group may have a substituent and preferably has a carbon number of 6 to 10. Examples of such aryl groups include a phenyl group, a tolyl group, a xylyl group, a cumenyl group, and a 1-naphthyl group.

[0051] The organic group having a functional group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 3 carbon atoms. Examples of the functional group include halogen groups such as a chloro group, a bromo group, and a fluoro group. Examples of organic groups having such functional groups include a chloroethyl group, a fluoroethyl group, a chloropropyl group, a dichloropropyl group, a fluoropropyl group, a difluoropropyl group, a chlorophenyl group, and a fluorophenyl group.

[0052] The organic group having a heteroatom preferably has 1 or more carbon atoms, more preferably 4 to 18 carbon atoms, and even more preferably 6 to 15 carbon atoms. Examples of the heteroatom include a nitrogen atom, an oxygen atom, and a sulfur atom. Examples of such an organic group having a heteroatom include a dimethylamino group, a diethylamino group, a diphenylamino group, a methyl sulfoxide group, an ethyl sulfoxide group, and a phenyl sulfoxide group.

[0053] The organic group having an unsaturated bond preferably has 3 or more carbon atoms, more preferably 4 to 18 carbon atoms, and even more preferably 6 to 15 carbon atoms. Examples of such an organic group having an unsaturated bond include a propenyl group, a propynyl group, a butenyl group, a butynyl group, an oleyl group, a phenyl group, a vinylphenyl group, and an alkylphenyl group, and among these, a vinylphenyl group is preferred.

[0054] In the general formulas (6), (7), and (8), each R preferably independently has at least one selected from the group consisting of a vinyl group, an acrylic group, a methacrylic group, a maleic acid ester group, a maleic acid amide group, a maleic acid imide group, a primary amino group, a secondary amino group, a thiol group, a hydrosilyl group, a hydroboron group, a phenolic hydroxyl group, and an epoxy group. Among these, a vinyl group, an acrylic group, a methacrylic group, a secondary amino group, and a thiol group are more preferred.

[0055] Specifically, the organic phosphines preferably include 4-(diphenylphosphino)styrene, which is suitable in that it has a highly reactive vinyl group and therefore exhibits low bleed-out properties.

[0056] Specifically, the sulfide compound preferably contains at least one of bis(hydroxyphenyl)sulfide, bis(4-acryloylthiophenyl)sulfide, 2-methylthiophenothiazine, bis(2-methacryloylthioethyl)sulfide, and bis(4-methacryloylthiophenyl)sulfide, and more preferably contains at least one of bis(4-acryloylthiophenyl)sulfide and bis(4-methacryloylthiophenyl)sulfide. Of these compounds, sulfide compounds having a highly reactive phenolic hydroxyl group, an acrylic group, or a methacrylic group are preferred because of their low bleed-out properties, and among these, sulfide compounds having an acrylic group or a methacrylic group are most preferred.

[0057] Specifically, the thiol compound preferably contains at least one of 2-dibutylamino-4,6-dimercapto-s-triazine, 2,4,6-trimercapto-s-triazine, 2-pyridinethiol, 2-pyridinemethanethiol, and 3-pyridinemethanethiol. Such compounds are suitable in that they have a highly reactive thiol group and therefore exhibit low bleed-out.

[0058] The organic phosphines, sulfide compounds, and thiol compounds may be used alone or in combination of two or more thereof. When the conductive composition contains two or more of the organic phosphines, sulfide compounds, and thiol compounds as fluxes, the bonding properties of the bonding film can be improved when the bonding film is produced using the conductive composition.

[0059] When the thermosetting resin contains a maleimide resin, these organic phosphines, sulfide compounds, and thiol compounds can form copolymers with the maleimide resin and therefore also function as thermosetting resin components. Furthermore, organic phosphines, sulfide compounds, and thiol compounds are resistant to moisture absorption, have sufficiently large molecular weights, and are polymerizable, so they can effectively prevent bleedout when used as flux components. Therefore, by using these organic phosphines, sulfide compounds, and thiol compounds instead of alcohols and carboxylic acids, which are prone to moisture absorption, the risk of bleedout can be reduced without the need for flux cleaning, and sufficient reliability, especially reflow resistance after moisture absorption, can be ensured.

[0060] Furthermore, in terms of suppressing bleed-out during sintering, etc., the number average molecular weight of the organic phosphines, sulfide compounds, and thiol compounds is preferably 260 or more. Bleed-out can be further reduced by having the number average molecular weight of the organic phosphines, sulfide compounds, and thiol compounds be 260 or more and reacting them with the maleimide resin and curing them as described above. As a result, surface contamination of metal substrates, lead frames, etc. due to bleed-out can be prevented, and package reliability can be improved.

[0061] The content of the organic phosphines in the conductive composition is preferably 0.5% by mass or more and 10.0% by mass or less, and more preferably 1.0% by mass or more and 5.0% by mass or less. By controlling the content of the organic phosphines within this range, the metal oxide film removal ability can be fully exhibited.

[0062] The content of the sulfide compound in the conductive composition is preferably 0.5% by mass or more and 8.0% by mass or less, and more preferably 1.0% by mass or more and 4.0% by mass or less. By controlling the content of the sulfide compound within the above range, the metal oxide film removal ability can be fully exhibited.

[0063] The content of the thiol compound in the conductive composition is preferably 0.5% by mass to 8.0% by mass, more preferably 0.5% by mass to 3.0% by mass. By controlling the content of the thiol compound within this range, the metal oxide film removal ability can be fully exhibited.

[0064] When the conductive composition contains two or more of organic phosphines, sulfide-based compounds, and thiol-based compounds as fluxes, the total content of these compounds in the conductive composition is preferably 1.0 mass% or more and 10.0 mass% or less, and more preferably 2.0 mass% or more and 5.0 mass% or less.

[0065] The organic phosphines, sulfide compounds, and thiol compounds may each be used alone or in combination of two or more.

[0066] (Solvent) The conductive composition contains a solvent such as cyclopentanone, toluene, or acetone to adjust the viscosity. The content of the solvent is not particularly limited, but is preferably 0.01% by mass or more and 3% by mass or less, and more preferably 0.05% by mass or more and 1.5% by mass or less. The solvent may be used alone or in combination of two or more types.

[0067] (Other Components) In addition to the above components, the conductive composition may optionally contain various additives. Such additives can be appropriately selected as needed, and examples thereof include dispersants, radical polymerization initiators, leveling agents, plasticizers, and curing agents.

[0068] When the first bonding layer and the second bonding layer are formed using the above-described conductive composition, a mixed layer containing a Cu—Sn intermetallic compound and a cured thermosetting resin may be provided at the interface between the first bonding layer and the metal layer and at the interface between the second bonding layer and the metal layer, respectively. In this way, a dense and highly heat-resistant Cu—Sn intermetallic compound is formed, thereby making it possible to produce a bonding film with high bonding strength.

[0069] The thickness of the first bonding layer and the second bonding layer is preferably 10 μm or more and 100 μm or less, and more preferably 15 μm or more and 30 μm or less. The thicknesses of the first bonding layer and the second bonding layer may be the same or different. When the first bonding layer and the second bonding layer are paste layers formed using a paste-like conductive composition, the thickness of the first bonding layer and the second bonding layer refers to the thickness of the paste layer after drying.

[0070] (Method for Producing Conductive Composition) The paste-like conductive composition is produced by arbitrarily mixing a metal component containing at least one type of metal particles (P), a thermosetting resin, a flux, a solvent, and, if necessary, various additives.

[0071] <Bonded Material> The bonding film according to the present invention can be bonded to a bonded material, such as an electronic component such as a semiconductor chip or semiconductor element, or a support member such as a metal substrate or metal lead frame. In such a case, the first bonding layer of the bonding film is bonded to the first bonded material, and the second bonding layer of the bonding film is bonded to the second bonded material. Examples of combinations of bonded materials include a first bonded material being an electronic component with a low linear expansion coefficient, such as a semiconductor chip or semiconductor element made of silicon (Si or SiC), and a second bonded material being a metal substrate or metal lead frame with a high linear expansion coefficient, such as a metal substrate or metal lead frame made of copper or a copper alloy. As described above, the bonding film according to the present invention has a multilayer structure in which a metal layer is provided between the first bonding layer and the second bonding layer, and the metal layer is disposed as a stress-relaxing intermediate layer. Therefore, even if there is a difference in linear expansion coefficient between the first bonded material and the second bonded material, the thermal strain stress caused by the difference in thermal expansion can be sufficiently relaxed, thereby preventing cracks from occurring inside the bonding film. The combination of bonded materials is not limited to cases where the difference in linear expansion coefficient between the first and second bonded materials is large. Even when the difference in linear expansion coefficient between the first and second bonded materials is small or even when there is no difference, thermal strain stress can be alleviated, thereby preventing cracks from occurring inside the bonding film. Even when the linear expansion coefficients of the first and second bonded materials are small, a difference in thermal expansion between the first and second bonded materials occurs, especially when the difference in ambient temperature between the first and second bonded materials is large. Even in such cases, the thermal strain stress caused by the difference in thermal expansion can be sufficiently alleviated, thereby preventing cracks from occurring inside the bonding film.

[0072] The joining surfaces of one or both of the first and second materials to be joined may be coated with a metal. Examples of metals that can be used to cover the joining surfaces of the materials to be joined include gold, silver, copper, and nickel. These metals are formed in layers on the joining surfaces of the materials to be joined by plating or the like.

[0073] [Method for manufacturing bonding film] The bonding film according to the present invention is obtained by stirring the conductive composition in a planetary mixer, thinly applying it to a release-treated PET film, and drying it at 80 to 140°C for 0.5 to 10 minutes to obtain a conductive adhesive film. Next, the obtained conductive adhesive film is bonded to the metal layer, and then temporarily bonded using a roll heated at 80 to 140°C. Further, the conductive composition is applied to the surface on the metal layer side, dried at 80 to 140°C for 0.5 to 10 minutes, and dicing tape is bonded thereon to obtain a bonding film having a metal layer mounted as an intermediate layer.

[0074] The thickness of the bonding film is not particularly limited, but is preferably 10 μm or more and 200 μm or less, and more preferably 30 μm or more and 100 μm or less.

[0075] The bonding film according to the present invention can be suitably used as a bonding film with dicing tape by being bonded to a dicing tape. Dicing tape is a tape used in the process of cutting a semiconductor wafer with a dicing saw to separate integrated circuits, packages, etc. formed on the semiconductor wafer. When the bonding film is in the form of a dicing die bonding film to which a dicing tape is bonded, the bonding film and the dicing tape can be bonded to the semiconductor wafer at the same time, thereby simplifying the process.

[0076] 1 shows the structure of a bonding film with dicing tape, in which a bonding film 1 is laminated on a dicing tape 12. The dicing tape 12 has a laminated structure in which an adhesive layer 12b is provided on a supporting substrate 12a, and the bonding film 1 is provided on the adhesive layer 12b. A release-treated PET film 11 covers the dicing tape 12 and protects the adhesive layer 12b and the bonding film 1.

[0077] The support substrate 12a is preferably radiation-transmitting, and specifically, plastic, rubber, etc. are usually used, but there are no particular limitations on the material as long as it transmits radiation.

[0078] The base resin composition of the adhesive of the adhesive layer 12b is not particularly limited, and a typical radiation-curable adhesive may be used. Examples of such radiation-curable adhesives include acrylic adhesives having a functional group, such as a hydroxyl group, that can react with an isocyanate group. The acrylic adhesive preferably has an iodine value of 30 or less and a radiation-curable carbon-carbon double bond structure.

[0079] As described above, the bonding film 1 of the present invention comprises a metal layer 1b, a first bonding layer 1a provided on one surface of the metal layer 1b, and a second bonding layer 1a provided on the other surface of the metal layer, and has a laminated structure in which the metal layer 1b is sandwiched between the two bonding layers 1a.

[0080] [Semiconductor Module] The semiconductor module according to the present invention includes the above-described bonding film, a first bonded material bonded to the first bonding layer, and a second bonded material bonded to the second bonding layer, wherein the first bonded material is an electronic component, and the second bonded material is a metal substrate or a metal lead frame. Examples of the electronic component include silicon electronic components such as semiconductor chips and semiconductor elements, and examples of the metal substrate or metal lead frame include metal substrates and metal lead frames made of copper or a copper alloy.

[0081] 2 shows an example of the structure of a semiconductor module including a bonding film according to the present invention. A first bonding layer 1a of the bonding film 1 is bonded to a semiconductor chip 2 via a metal plating layer 2a provided on the bonding surface of the semiconductor chip 2, and a second bonding layer 1a of the bonding film 1 is bonded to a metal lead frame 3.

[0082] The semiconductor module according to the present invention is also effective for use in wide-gap semiconductors that operate at high temperatures of 200° C. or higher, and can therefore be mounted in inverters. Such inverters can also be mounted in electric vehicles, electric railway vehicles, power conditioners, etc.

[0083] [Method for Manufacturing a Semiconductor Module] The method for manufacturing a semiconductor module according to the present invention includes a step of bonding an electronic component to a metal substrate or metal lead frame via the bonding film by heating the electronic component and the metal substrate or metal lead frame in an inert or reducing atmosphere with the bonding film interposed between the electronic component and the metal substrate or metal lead frame. Examples of electronic components include silicon electronic components such as semiconductor chips and semiconductor elements, and examples of metal substrates or metal lead frames include metal substrates or metal lead frames made of copper or copper alloys. An inert atmosphere refers to a state filled with an inert gas such as argon gas or nitrogen gas, and a reducing atmosphere refers to a state filled with a reducing gas such as hydrogen gas. The heating temperature is preferably 230°C to 350°C, and the heating time is preferably 1 minute to 20 minutes.

[0084] Based on the above embodiments, the present invention relates to the following [1] to

[10] . [1] A bonding film comprising a metal layer, a first bonding layer provided on one surface of the metal layer, and a second bonding layer provided on the other surface of the metal layer, wherein the metal layer contains a metal having a thermal conductivity of 100 W / m·K or more at a temperature of 300 K, and the metal layer has a 0.2% yield strength of 250 MPa or less. [2] The bonding film according to [1] above, wherein the first bonding layer and the second bonding layer each contain at least one type of metal particles (P). [3] The bonding film according to [1] or [2] above, wherein the metal layer is a perforated or textured metal foil. [4] The bonding film according to any one of [1] to [3] above, wherein the thickness of the metal layer is 8 μm or more and 200 μm or less. [5] The bonding film according to any one of [1] to [4] above, wherein the first bonding layer and the second bonding layer each have a thickness of 10 μm or more and 100 μm or less. [6] The bonding film according to any one of [1] to [5] above, wherein the first bonding layer and the second bonding layer are paste layers formed using a paste-like conductive composition, and the conductive composition contains at least one type of metal particles (P), a thermosetting resin, a flux, and a solvent. [7] A semiconductor module comprising the bonding film according to any one of [1] to [6] above, a first material to be bonded to the first bonding layer, and a second material to be bonded to the second bonding layer, wherein the first material to be bonded is an electronic component, and the second material to be bonded is a metal substrate or a metal lead frame. [8] An inverter equipped with the semiconductor module according to [7] above. [9] An electronic device equipped with the inverter according to [8] above.

[10] A method for manufacturing a semiconductor module, comprising a step of heating an electronic component and a metal substrate or a metal lead frame via the bonding film described in any one of [1] to [6] above, in an inert atmosphere or a reducing atmosphere at a temperature of 230°C to 350°C for 1 minute to 20 minutes, with the bonding film being interposed between the electronic component and the metal substrate or the metal lead frame.

[0085] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, but includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention.

[0086] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0087] The materials used for each component are shown below. Unless otherwise specified, % means % by mass.

[0088] First metal particles (P1) Cu particles: fine copper powder (manufactured by Mitsui Mining & Smelting Co., Ltd.) Particle diameter (d50): 5.2 μm Second metal particles (P2) Sn—Cu—Ni-based solder particles: trade name “SN100C” (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) Particle diameter (d50): 6 μm Thermosetting resin Maleimide resin: trade name “BMI-3000” (manufactured by DESIGNER MOLECULES INC.) Flux Sulfide-based compound: trade name “MPSMA” (manufactured by Sumitomo Seika Chemicals Co., Ltd.) Solvent Cyclopentanone (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0089] Example 1 <Preparation of conductive composition> Of the above materials, 57.0 mass % of Cu particles, 36.4 mass % of Sn particles, and 6.6 mass % of other components (thermosetting resin, flux, solvent, curing agent, etc.) were mixed to prepare a paste-like conductive composition (hereinafter also referred to as "paste material").

[0090] <Bonding Film> The prepared paste material was thinly applied to a release-treated PET film and dried at 120°C in a nitrogen atmosphere. Next, electrolytic Cu foil (thickness: 100 μm) that had been softened by heat treatment at 600°C for 60 minutes was bonded to the dried paste material (paste layer), and then temporarily bonded using a roll heated at 90°C. Further, the above paste material was applied to the surface of the Cu foil and dried at 120°C in a nitrogen atmosphere. Furthermore, dicing tape was bonded to the dried paste material (paste layer), and a bonding film having the structure shown in Figure 1 was produced.

[0091] <Semiconductor Module> The PET film was peeled off from the prepared bonding film, and a Si wafer (0.2 mm thick) was bonded to the surface of the exposed bonding layer. The wafer was then diced with a dicing blade to produce semiconductor chips. The number of chips that broke off per 8-inch wafer during this dicing process was tallied. This was used as an evaluation item for the "dicing performance" described below. The bonding film to which the semiconductor chips were bonded was then peeled off from the dicing tape, and the exposed bonding layer was placed on a Cu substrate. The substrate was preheated at 150°C in a nitrogen atmosphere and then further baked at 280°C to produce a mounted sample semiconductor module having the structure shown in FIG. 2.

[0092] <Dicing Performance> The dicing performance was evaluated as follows. The results are shown in Table 1. ⊚: Chip skipping less than 1% ◯: Chip skipping 1% or more and less than 3% △: Chip skipping 3% or more and less than 10% ×: Chip skipping 10% or more

[0093] <Shear Hardness> Of the manufactured mounting samples, samples that could be mounted without chip flying were subjected to a thermal shock test (TCT) from -45°C to +200°C, and the bonding condition was evaluated by a shear test after 1000 cycles. Specifically, the shear strength after the TCT was measured at a test speed of 50 μm / s and a substrate / jig clearance of 0.05 mm, and was evaluated as follows: If the shear strength was rated "△" or higher, it was evaluated that the occurrence of cracks due to thermal strain stress applied internally was prevented. The results are shown in Table 1. ・◎: Shear strength of 35 MPa or more ・〇: Shear strength of 25 MPa or more but less than 35 MPa ・△: Shear strength of 15 MPa or more but less than 25 MPa ・×: Shear strength less than 15 MPa

[0094] Example 2 The same operation as in Example 1 was performed, except that the thickness of the Cu foil used in the bonding film was changed to 35 μm, and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0095] Example 3 The same operation as in Example 1 was performed, except that the thickness of the Cu foil used in the bonding film was changed to 18 μm, and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0096] Example 4 The same operation as in Example 1 was carried out, except that the Cu foil used for the bonding film was changed to an electrolytic Cu foil (thickness: 15 μm, aperture ratio: 17%) that had been perforated with holes having a diameter of 0.35 mm, and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0097] Example 5 The same procedure as in Example 1 was carried out, except that the Cu foil used in Example 4 was replaced with a Cu foil that had been perforated to have an opening rate of 32%, and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0098] Example 6 The same operations as in Example 1 were carried out, except that the Cu foil used in the bonding film in Example 4 was softened in advance by heat treatment at 600°C for 60 minutes, and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0099] Example 7 The same operation as in Example 1 was carried out, except that the Cu foil used in the bonding film in Example 6 was changed to a Cu foil that had been perforated with an opening rate of 32%, and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0100] Example 8 The same operation as in Example 1 was carried out, except that the paste material was applied and dried using the Cu foil used in the bonding film in Example 7 so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0101] Example 9 The same operation as in Example 1 was carried out, except that the Cu foil used in the bonding film in Example 7 was used, and the paste material was applied and dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0102] Example 10 The same operation as in Example 1 was performed, except that the Cu foil used in the bonding film was changed to a Zn foil (thickness: 56 μm), and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0103] Example 11 The same operation as in Example 1 was performed, except that the Cu foil used in the bonding film was changed to an Al foil (thickness: 85 μm), and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0104] Comparative Example 1 The paste material prepared in Example 1 was applied to a release-treated PET film, dried at 120°C in a nitrogen atmosphere, and then a dicing tape was attached onto the paste material (paste layer) to prepare a bonding film having the structure shown in Fig. 3. The results are shown in Table 1.

[0105] Comparative Example 2 The same operation as in Example 1 was carried out, except that the Cu foil used in the bonding film was changed to Cu foil (thickness: 50 μm) that had not been softened by heat treatment, and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0106] Comparative Example 3 The same operation as in Example 1 was carried out, except that the Cu foil used in the bonding film was changed to a notched Cu foil (thickness: 100 μm) that had not been softened by heat treatment, and the paste material was dried so that the thickness of the paste material (paste layer) after drying would be as shown in Table 1. The results are shown in Table 1.

[0107]

[0108] As shown in Table 1, the obtained bonding films exhibited excellent dancing performance in Examples 1 to 3 and 5 to 6. In addition, the bonding films also had excellent shear strength after TCT, and were able to prevent cracks caused by thermal distortion stress applied to the inside.

[0109] In Example 4, the obtained bonding film exhibited good dancing performance. In addition, the bonding film also had excellent shear strength after TCT, and it was possible to prevent the occurrence of cracks due to thermal distortion stress acting inside.

[0110] The resulting bonding films in Examples 7 to 9 exhibited excellent dancing performance. In addition, the bonding films also had excellent shear strength after TCT, and were able to prevent cracks caused by thermal distortion stress applied to the inside.

[0111] In Examples 10 and 11, the resulting bonding films exhibited excellent dancing performance. In addition, the bonding films also had excellent shear strength after TCT, and were able to prevent cracks caused by thermal distortion stress applied to the inside.

[0112] On the other hand, in Comparative Example 1, which used a bonding film without a metal layer, excellent dancing performance was exhibited, but the shear strength after TCT was low, and it was not possible to prevent the occurrence of cracks due to thermal strain stress applied internally.

[0113] In addition, in Comparative Example 3, which used a bonding film in which a hard Cu foil with a high 0.2% yield strength was interposed as a metal layer and was not softened by heat treatment, the shear strength after TCT was good and it was possible to prevent the occurrence of cracks due to thermal distortion stress applied to the inside, but the dancing performance was poor.

[0114] In Comparative Example 4, which used a bonding film in which a notched Cu foil was sandwiched as a metal layer and was a hard Cu foil with a high 0.2% yield strength that had not been softened by heat treatment, the shear strength after TCT was good and it was possible to prevent the occurrence of cracks due to thermal distortion stress applied to the inside, but the dancing performance was poor.

[0115] In this way, in the bonding film according to the present invention, a metal layer having predetermined properties is inserted as an intermediate layer, and bonding layers containing a predetermined metal at a certain content are provided on both sides of the metal layer, so that it is possible to provide a bonding film that exhibits good dicing performance while preventing the occurrence of cracks due to thermal strain stress applied to the interior, and a semiconductor module using the same. It is also possible to provide an inverter equipped with such a semiconductor module, and an electronic device equipped with such an inverter.

[0116] REFERENCE SIGNS LIST 1 Bonding film 1a First bonding layer, second bonding layer 1b Metal layer 2 Semiconductor chip 2a Metal plating layer 3 Metal lead frame 11 Release-treated PET 12 Dicing tape 12a Supporting substrate 12b Pressure-sensitive adhesive layer

Claims

1. A bonding film comprising a metal layer, a first bonding layer provided on one surface of the metal layer, and a second bonding layer provided on the other surface of the metal layer, wherein the metal layer contains a metal having a thermal conductivity of 100 W / m·K or more at a temperature of 300 K, and the metal layer has a 0.2% yield strength of 250 MPa or less.

2. The bonding film according to claim 1, wherein the first bonding layer and the second bonding layer each contain at least one type of metal particles (P).

3. The bonding film according to claim 1 or 2, wherein the metal layer is a metal foil that has been perforated or textured.

4. The bonding film according to claim 1 or 2, wherein the thickness of the metal layer is 8 μm or more and 200 μm or less.

5. A bonding film according to claim 1 or 2, wherein the thickness of the first bonding layer and the second bonding layer is 10 μm or more and 100 μm or less.

6. A bonding film according to claim 1 or 2, wherein the first bonding layer and the second bonding layer are paste layers formed using a paste-like conductive composition, and the conductive composition contains at least one type of metal particles (P), a thermosetting resin, a flux, and a solvent.

7. A semiconductor module comprising the bonding film according to claim 1 or 2, a first bonded material bonded to said first bonding layer, and a second bonded material bonded to said second bonding layer, wherein said first bonded material is an electronic component, and said second bonded material is a metal substrate or a metal lead frame.

8. An inverter equipped with the semiconductor module according to claim 7.

9. An electronic device equipped with the inverter according to claim 8.

10. A method for manufacturing a semiconductor module, comprising the step of: interposing a bonding film as described in claim 1 or 2 between an electronic component and a metal substrate or metal lead frame; and heating the electronic component at a temperature of 230°C to 350°C for 1 to 20 minutes in an inert or reducing atmosphere, thereby bonding the electronic component to the metal substrate or metal lead frame via the bonding film.

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