Firing composition and method for producing semiconductor device

Abstract

The present invention pertains to: a firing composition which contains metal particles (A) containing metal particles having a particle diameter of 1.0 μm or less, and an aliphatic polycarbonate (B), wherein the aliphatic polycarbonate (B) has, in a side chain thereof, a substituted or unsubstituted C2-C6 aliphatic hydrocarbon group that is bonded to the main chain directly or via an oxygen atom, and the content of the aliphatic polycarbonate (B) with respect to the total content of the metal particles (A) and the aliphatic polycarbonate (B) is 4 to 14% by mass; and a method for producing a semiconductor device that uses said firing composition.

Description

Composition for firing and method for manufacturing semiconductor devices

[0001] This invention relates to a firing composition and a method for manufacturing semiconductor devices.

[0002] One known method for joining components involves interposing a joining material containing metal particles and a binder resin between the components to be joined (hereinafter also referred to as "components to be joined"), heating them under pressure, and firing the joining material to join the components. In this method, the binder resin decomposes upon firing of the joining material, and the metal particles melt and bond together, forming a metal sintered layer that joins the components to be joined.

[0003] Because the metal sintered layer formed from metal particles has excellent heat dissipation properties, the above bonding method is used, for example, in bonding power semiconductor elements (power devices). Since power semiconductor elements are used under high voltage and high current, heat generated from the semiconductor elements tends to be a problem, but by bonding semiconductor elements using the above bonding method, it is possible to improve heat dissipation.

[0004] Bonding materials containing metal particles and binder resin offer excellent shape retention and flexibility due to the binder resin, allowing for greater freedom in shape design and usage, such as by forming them into films. On the other hand, bonding materials containing binder resin require firing at relatively high temperatures to sufficiently decompose the binder resin during firing. However, from a productivity standpoint, it is desirable for bonding to be possible under the lowest possible temperatures (hereinafter also referred to as "low-temperature sinterability").

[0005] Patent Document 1 discloses a low-temperature firing type binder resin composition comprising 100 parts by weight of a (meth)acrylate polymer (A) having a functional group capable of hydrogen bonding with a hydroxyl group, 20 to 200 parts by weight of an organic compound (B) having three or more hydroxyl groups, and 100 parts by weight or less of an organic solvent (C) with a boiling point of 150°C or higher.

[0006] Patent Document 2 discloses a sintering bonding composition containing conductive metal-containing sinterable particles, the average particle size being 70 nm or more and 2 μm or less, with a proportion of particles with a particle size of 100 nm or less being 80% by mass or more, wherein polypropylene carbonate is used as the binder resin.

[0007] Japanese Patent Publication No. 2006-160791 Japanese Patent Publication No. 2023-41064

[0008] However, the acrylate polymer described in Patent Document 1 did not have sufficient low-temperature sinterability. Furthermore, when polypropylene carbonate, used in Patent Document 2, was used as the binder resin for the bonding material, there was a problem that cracks were likely to occur in the bonded members when the bonding material was in film form.

[0009] When a bonding material is interposed between two members to be joined, and these are heated under pressure to sinter the bonding material, the bonding material, softened by heating, may protrude from the edges of the members to be joined (hereinafter simply referred to as "protrusion from the edges of the members to be joined"). Protrusion from the edges of the members to be joined is desirable to suppress because it can cause the thickness of the formed metal sintered layer to be thinner than the target value and make the resulting joint difficult to handle. However, it has been difficult to achieve both crack resistance of the film-type bonding material and suppression of protrusion from the edges of the members to be joined.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a firing composition that exhibits excellent low-temperature sinterability and crack resistance in film form, and suppresses overflow from the edges of the member to be joined, and a method for manufacturing a semiconductor device using the firing composition.

[0011] As a result of diligent research, the inventors have discovered that the above problems can be solved by a firing composition containing a predetermined amount of a binder resin having a specific chemical structure, and have completed the present invention described below.

[0012] That is, the present invention relates to the following [1] to

[11] . [1] A composition for firing, comprising: metal particles (A) including metal particles having a particle diameter of 1.0 μm or less; and an aliphatic polycarbonate (B), wherein the aliphatic polycarbonate (B) has, in a side chain thereof, a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 6 carbon atoms that is bonded to the main chain directly or via an oxygen atom, and the content of the aliphatic polycarbonate (B) relative to the total amount of the metal particles (A) and the aliphatic polycarbonate (B) is 4 to 14% by mass. [2] The composition for firing according to [1] above, wherein the aliphatic polycarbonate (B) has a structural unit represented by the following general formula (1a). (In the formula, R １ , R ２ , R ３ and R ４ are each independently a hydrogen atom or a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 6 carbon atoms, and among R １ , R ２ , R ３ and R ４ , at least one is the substituted or unsubstituted aliphatic hydrocarbon group having 2 to 6 carbon atoms.) [3] R １ , R ２ , R ３ and R ４[2] The calcination composition according to [2] above, wherein only one of the above is a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 6 carbon atoms. [4] The calcination composition according to any one of [1] to [3] above, wherein the substituted or unsubstituted aliphatic hydrocarbon group having 2 to 6 carbon atoms is a substituted or unsubstituted linear aliphatic hydrocarbon group having 2 to 6 carbon atoms. [5] The calcination composition according to any one of [1] to [4] above, wherein the metal particles (A) are one or more metal particles selected from the group consisting of silver particles, gold particles, copper particles, iron particles, nickel particles, aluminum particles, tungsten particles, molybdenum particles, silicon particles, palladium particles, platinum particles, titanium particles and barium titanate particles, oxide particles of the metal constituting the metal particles, or alloy particles of the metal constituting the metal particles. [6] The calcination composition according to any one of [1] to [5] above, used for joining a semiconductor element to other components. [7] The firing composition according to [6], wherein the semiconductor element is a power semiconductor element. [8] The firing composition according to any one of [1] to [7], further comprising a solvent (C) and being in paste form. [9] The firing composition according to any one of [1] to [7], being in film form.

[10] A method for manufacturing a semiconductor device using the film-like firing composition according to [9], comprising: step 1 of stacking a semiconductor element and other components via the firing composition to obtain a laminate; and step 2 of heating and pressurizing the laminate to form a metal sintered layer by firing the firing composition, thereby obtaining a bond in which the semiconductor element and the other components are joined by the metal sintered layer.

[11] The method for manufacturing a semiconductor device according to

[10] , wherein the heating temperature in step 2 is 320°C or lower.

[0013] According to the present invention, it is possible to provide a firing composition that exhibits excellent low-temperature sinterability and crack resistance in film form, and suppresses overflow from the edges of the member to be joined, and a method for manufacturing a semiconductor device using the firing composition.

[0014] In this specification, the lower and upper limits described in steps for a preferred numerical range can be combined independently. For example, from the description "preferably 10 to 90, more preferably 30 to 60," the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60."

[0015] In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid," and the same applies to other similar terms.

[0016] In this specification, the "thickness" of an object refers to the total thickness of the object. For example, if the object consists of multiple layers, it refers to the total thickness of all the layers constituting the object. Unless otherwise specified, the "thickness" of an object in this specification refers to the average value of the thickness measured at five randomly selected locations on the object, and can be obtained using a constant-pressure thickness measuring instrument in accordance with JIS K 7130:1999.

[0017] In this specification, "solids" refers to the components of the composition in question, excluding the solvent.

[0018] In this specification, "paste" means a mixture in which some or all of the solid components are dispersed in a solvent.

[0019] Furthermore, the mechanism of action described herein is speculative and does not limit the mechanism by which the present invention achieves its effects.

[0020] [Casturing Composition] The calcining composition of this embodiment contains metal particles (A) having a particle size of 1.0 μm or less, and an aliphatic polycarbonate (B), wherein the aliphatic polycarbonate (B) has substituted or unsubstituted aliphatic hydrocarbon groups having 2 to 6 carbon atoms in its side chains, which are directly or via oxygen atoms bonded to the main chain, and the content of the aliphatic polycarbonate (B) relative to the total amount of the metal particles (A) and the aliphatic polycarbonate (B) is 4 to 14% by mass.

[0021] The firing composition of this embodiment is used to join members to be joined together. Specifically, it is used in a joining method in which the firing composition of this embodiment is interposed between members to be joined, and these members are heated under pressure to fire the firing composition, thereby forming a metal sintered layer that joins the members to be joined.

[0022] The form of the firing composition of this embodiment is not particularly limited and may be in the form of a paste or a film, but when used for joining members to be joined together, it is preferable to be in the form of a film. In the following description, the paste-like firing composition of this embodiment may be referred to as the "firing paste composition," and the film-like firing composition of this embodiment may be referred to as the "film-like firing material."

[0023] The firing composition of this embodiment exhibits excellent low-temperature sinterability and crack resistance in film form (hereinafter also simply referred to as "crack resistance"), and can suppress overflow from the edges of the joined members. The details of the reason for this are unknown, but it is presumed to be as follows. The aliphatic polycarbonate (B) contained in the firing composition of this embodiment has a carbonate structure, which causes it to decompose at low temperatures through a specific reaction, specifically a backbiting reaction. Therefore, the firing composition of this embodiment can be fired at relatively low temperatures. In addition, the aliphatic polycarbonate (B) has substituted or unsubstituted aliphatic hydrocarbon groups having 2 to 6 carbon atoms in its side chains, which are directly or via oxygen atoms attached to the main chain. Based on this structure, it is thought that the balance between hydrophilicity and hydrophobicity of the aliphatic polycarbonate (B) has become suitable for the dispersion of metal particles (A), thereby improving the homogeneity of the firing composition. As a result, it is presumed that the crack resistance in film form has improved. Furthermore, in this embodiment, the firing composition has an aliphatic polycarbonate (B) content of 4 to 14% by mass relative to the total amount of metal particles (A) and aliphatic polycarbonate (B). As a result, while having good flexibility in film form, the fluidity during firing is moderately suppressed, which is presumed to achieve both excellent crack resistance in film form and suppression of overflow from the edges of the joined members.

[0024] Hereinafter, each component contained in the firing composition of the present embodiment will be described.

[0025] <Metal particles (A) including metal particles having a particle diameter of 1.0 µm or less> The firing composition of the present embodiment contains metal particles (A) including metal particles having a particle diameter of 1.0 µm or less (hereinafter, also simply referred to as "metal particles (A)"). When the firing composition of the present embodiment is fired, the metal particles (A) form a metal sintered layer that bonds members to be joined to each other. One type of the metal particles (A) may be used alone, or two or more types may be used in combination. In the present specification, the term "metal particles" means particles containing a metal, and may be particles consisting only of a metal, or may be particles containing a metal such as a metal oxide and an element other than a metal, for example.

[0026] Examples of the metal particles (A) include one or more metal particles selected from the group consisting of silver particles, gold particles, copper particles, iron particles, nickel particles, aluminum particles, tungsten particles, molybdenum particles, silicon particles, palladium particles, platinum particles, titanium particles, and barium titanate particles; oxide particles of the metal constituting the above metal particles; alloy particles of the metal constituting the above metal particles; and the like. Among these, one or more selected from the group consisting of silver particles and copper particles are preferable from the viewpoints of conductivity, thermal conductivity, bonding strength of the metal sintered layer, and low-temperature sinterability.

[0027] From the viewpoint of low-temperature sinterability, the metal particles (A) contain metal particles having a particle diameter of 1.0 µm or less. Among the metal particles listed above, the metal particles having a particle diameter of 1.0 µm or less are preferably one or more selected from the group consisting of silver particles and copper particles, and more preferably silver particles.

[0028] From the viewpoint of low-temperature sinterability, the metal particles (A) preferably contain metal particles having a particle diameter of 700 nm or less, more preferably contain metal particles having a particle diameter of 500 nm or less, still more preferably contain metal particles having a particle diameter of 300 nm or less, even more preferably contain metal particles having a particle diameter of 200 nm or less, even more preferably contain metal particles having a particle diameter of 100 nm or less, and even more preferably contain metal particles having a particle diameter of 80 nm or less. The particle diameter of the metal particles contained in the metal particles (A) may be 0.1 nm or more, 0.3 nm or more, 0.5 nm or more, 1 nm or more, or 5 nm or more. Further, the particle diameter of the metal particles contained in the metal particles (A) may be 0.1 nm to 700 nm, 0.3 nm to 500 nm, 0.5 nm to 300 nm, 1 nm to 200 nm, 5 nm to 100 nm, or 5 nm to 80 nm.

[0029] In the present embodiment, the particle diameter of the metal particles (A) means the equivalent circular diameter, which is the diameter of a circle having the same area as the projected area of the metal particles (A). The projected area of the metal particles (A) can be obtained, for example, by a method of observing a film-shaped fired material formed by applying and drying the firing composition of the present embodiment with an electron microscope or the like, and specifically can be obtained by the method described in the Examples. Further, the particle diameter of the metal particles (A) means the particle diameter of primary particles.

[0030] From the viewpoint of low-temperature sinterability, the number-average particle diameter of metal particles with a particle size of 1.0 μm or less is preferably 0.1 nm to 1.0 μm, more preferably 0.3 nm to 700 nm, even more preferably 0.5 nm to 500 nm, even more preferably 0.7 nm to 300 nm, even more preferably 1 nm to 200 nm, even more preferably 3 nm to 100 nm, and even more preferably 5 nm to 80 nm. The number-average particle diameter of metal particles with a particle size of 1.0 μm or less refers to the average particle diameter obtained by number-averaging the equivalent circle diameters of 200 randomly selected metal particles from among metal particles whose equivalent circle diameter (the diameter of a circle having the same area as the projected area of ​​the metal particle) is 1.0 μm or less. The method for obtaining the projected area of ​​the metal particles is as described above.

[0031] The content of metal particles with a particle size of 1.0 μm or less in the metal particles (A) is preferably 1 to 100% by mass, more preferably 5 to 50% by mass, even more preferably 10 to 40% by mass, and even more preferably 15 to 30% by mass. When the content of metal particles with a particle size of 1.0 μm or less is above the lower limit, low-temperature sinterability tends to be better. Also, when the content of metal particles with a particle size of 1.0 μm or less is below the upper limit, economic efficiency tends to be better.

[0032] From an economic standpoint, the metal particles (A) may further contain metal particles with a particle size exceeding 1.0 μm. Among those listed above, the metal particles with a particle size exceeding 1.0 μm are preferably one or more selected from the group consisting of silver particles and copper particles, with copper particles being more preferable.

[0033] The metal particles (A) may include metal particles with a particle diameter greater than 1.0 μm and 20 μm or less, metal particles with a particle diameter of 1.2 to 15 μm, metal particles with a particle diameter of 1.5 to 10 μm, or metal particles with a particle diameter of 2 to 5 μm.

[0034] The number-average particle diameter of metal particles with a particle diameter exceeding 1.0 μm may be greater than 1.0 μm and less than or equal to 10 μm, may be between 1.2 and 5 μm, or may be between 1.5 and 3 μm. The number-average particle diameter of metal particles with a particle diameter exceeding 1.0 μm refers to the average particle diameter obtained by number-averaging the equivalent circle diameters of 200 randomly selected metal particles from among those with an equivalent circle diameter (the diameter of a circle having the same area as the projected area of ​​the metal particle) exceeding 1.0 μm. The method for obtaining the projected area of ​​the metal particles is as described above.

[0035] The shape of the metal particles (A) is not particularly limited and can be spherical, polygonal, plate-shaped, flake-shaped, angular, needle-shaped, rod-shaped, etc. Among these, spherical is preferred. In this embodiment, "spherical" means a perfect sphere or ellipsoid with an aspect ratio (major axis diameter / minor axis diameter) of 1.2 or less.

[0036] The metal particles (A) may be pre-dispersed in a solvent. A high-boiling point solvent such as isobornylcyclohexanol or decyl alcohol is preferred as the solvent for dispersing the metal particles (A). The boiling point of the high-boiling point solvent is, for example, 200 to 350°C. By using a high-boiling point solvent for dispersing the metal particles (A), the volatilization of the solvent at room temperature is suppressed, preventing re-aggregation of the metal particles (A) due to an increase in their concentration, thereby improving workability and quality. A method for dispersing the metal particles (A) in the solvent is to use a mixing apparatus as described in the method for manufacturing the calcination composition of this embodiment, which will be described later.

[0037] The surface of the metal particles (A) may be coated with an organic substance. The surface of the metal particles (A) coated with an organic substance has improved affinity with the binder resin, thus suppressing aggregation of the metal particles (A) in the firing composition and allowing for more uniform dispersion. When the surface of the metal particles (A) is coated with an organic substance, the mass and particle size of the metal particles (A) include the coating.

[0038] <Aliphatic Polycarbonate (B)> The firing composition of this embodiment contains aliphatic polycarbonate (B). Aliphatic polycarbonate (B) acts as a binder resin in the firing composition of this embodiment, and plays a role in enhancing crack resistance, shape retention, and adhesion to the bonded member in film form.

[0039] Aliphatic polycarbonate (B) has side chains of substituted or unsubstituted aliphatic hydrocarbon groups having 2 to 6 carbon atoms, which are directly or via oxygen atoms attached to the main chain. In this embodiment, the side chain of aliphatic polycarbonate (B) refers to an atomic group containing carbon atoms that branch off from the carbon atom chains that are linearly connected to the adjacent carbonate groups, within a molecular chain formed by linking structural units (hereinafter also called "carbonate units") consisting of a divalent aliphatic hydrocarbon group and a carbonate group (-O-C(=O)-O-). Furthermore, the main chain of aliphatic polycarbonate (B) refers to the molecular chain formed by linking the above carbonate units, excluding the side chains. For example, when a carbonate unit consisting of a branched divalent aliphatic hydrocarbon group and a carbonate group (-O-C(=O)-O-) is linked, the carbon chain linearly connected to the carbonate group constitutes the main chain, and the carbon chains branching off from the linearly connected carbon chain among the branched divalent aliphatic hydrocarbon groups constitute the side chains.

[0040] In the following explanation, the "substituted or unsubstituted aliphatic hydrocarbon groups having 2 to 6 carbon atoms that are directly or via an oxygen atom attached to the main chain" that aliphatic polycarbonate (B) has in its side chains may be referred to as "aliphatic hydrocarbon groups (X)".

[0041] The aliphatic hydrocarbon group (X) may be linear, branched, or cyclic, and may have both linear and cyclic structures, but it is preferable that it be linear from the viewpoint of ease of manufacture, etc.

[0042] The aliphatic hydrocarbon group (X) has 2 to 6 carbon atoms. When the aliphatic hydrocarbon group (X) has 2 or more carbon atoms, the dispersibility of the metal particles (A) is improved, the crack resistance in film form is improved, and it becomes easier to form a metal sintered layer with higher bonding strength. In addition, the glass transition temperature of the aliphatic polycarbonate (B) is lowered, resulting in excellent adhesion to the member to be bonded. Furthermore, when the aliphatic hydrocarbon group (X) has 6 or fewer carbon atoms, excellent low-temperature sinterability is obtained. From the same viewpoint as above, the aliphatic hydrocarbon group (X) has 2 to 5 carbon atoms, more preferably 2 to 4, even more preferably 2 or 3, and even more preferably 2 carbon atoms. Note that the carbon atoms of substituents are not included in the carbon number of the aliphatic hydrocarbon group (X) mentioned above.

[0043] Examples of substituents that the aliphatic hydrocarbon group (X) may have include hydroxyl groups, thiol groups, cyano groups, amino groups, silyl groups, halogen atoms such as fluorine, chlorine, bromine, and iodine; alkoxy groups, alkenyloxy groups; aryl groups such as phenyl groups; heteroaryl groups containing oxygen, nitrogen, sulfur, selenium, and phosphorus atoms as heteroatoms; aryloxy groups such as phenoxy groups; heteroaryloxy groups containing oxygen, nitrogen, sulfur, selenium, and phosphorus atoms as heteroatoms; alkylsilyl groups; alkylsilyloxy groups; and so on. From the viewpoint of low-temperature sinterability, the number of carbon atoms in the substituents that the aliphatic hydrocarbon group (X) may have is preferably 6 or less, more preferably 3 or less, even more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0. From the viewpoint of low-temperature sinterability, the aliphatic hydrocarbon group (X) preferably does not have substituents containing hydrocarbon groups, and more preferably does not have substituents.

[0044] Examples of the aliphatic hydrocarbon group (X) include substituted or unsubstituted C2-C6 alkyl groups; substituted or unsubstituted C2-C6 alkenyl groups; substituted or unsubstituted C2-C6 alkynyl groups; and the like. Among these, substituted or unsubstituted C2-C6 alkyl groups are preferred from the viewpoint of low-temperature sinterability and ease of manufacture. Examples of C2-C6 alkyl groups include chain-like alkyl groups such as ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 3-methylbutyl group, and n-hexyl group; and cyclic alkyl groups such as cyclopropyl group, cyclopentyl group, and cyclohexyl group. Among these, from the viewpoint of low-temperature sinterability, substituted or unsubstituted linear alkyl groups are preferred, substituted or unsubstituted linear alkyl groups are more preferred, unsubstituted linear alkyl groups are even more preferred, and unsubstituted ethyl groups are even more preferred.

[0045] The main chain of aliphatic polycarbonate (B) may or may not have groups other than aliphatic hydrocarbon groups (X) as side chains or substituents. From the viewpoint of low-temperature sinterability, it is preferable that the groups other than aliphatic hydrocarbon groups (X) do not contain hydrocarbon groups having 2 or more carbon atoms. Examples of groups that do not contain hydrocarbon groups having 2 or more carbon atoms include substituted or unsubstituted methyl groups; substituted or unsubstituted methoxy groups; hydroxyl groups; thiol groups; cyano groups; amino groups; silyl groups; halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; and so on. However, from the viewpoint of low-temperature sinterability, it is preferable that aliphatic polycarbonate (B) does not have groups other than aliphatic hydrocarbon groups (X) directly bonded to the main chain.

[0046] The aliphatic hydrocarbon group (X) is bonded to the main chain either directly or via an oxygen atom, but from the viewpoint of low-temperature sinterability, it is preferable that the group is directly bonded to the main chain.

[0047] The structural unit having an aliphatic hydrocarbon group (X) in its side chain is preferably a structural unit represented by the following general formula (1) from the viewpoint of low-temperature sinterability, crack resistance in film form, and bonding strength of the metal sintered layer.

[0048] (In the formula, R １ and R ２ Each of these groups is independently a group that does not contain a hydrogen atom, an aliphatic hydrocarbon group (X), or a hydrocarbon group having 2 or more carbon atoms, and all R contained in the structural unit １ and R ２ At least one of these is an aliphatic hydrocarbon group (X). n is an integer between 1 and 10.

[0049] R １ and R ２ The explanations for the "aliphatic hydrocarbon group (X)" and the "group that does not contain a hydrocarbon group with two or more carbon atoms" represented by are as described above.

[0050] All R included in the structural unit represented by the general formula (1) above １ and R ２ Of these, at least one is an aliphatic hydrocarbon group (X), and from the viewpoint of low-temperature sinterability, it is preferable that one to three are aliphatic hydrocarbon groups (X), more preferably that one or two are aliphatic hydrocarbon groups (X), and even more preferably that only one is an aliphatic hydrocarbon group (X).

[0051] All R included in the structural unit represented by the general formula (1) above １ and R ２ Of these, it is preferable that all those that are not aliphatic hydrocarbon groups (X) are hydrogen atoms.

[0052] In the above general formula (1), n ​​is an integer from 1 to 10, and from the viewpoint of low-temperature sinterability, crack resistance in film form, and bonding strength of the metal sintered layer, it is preferably 1 to 8, more preferably 2 to 6, even more preferably 2 to 4, even more preferably 2 to 3, and particularly preferably 2.

[0053] The structural unit represented by the above general formula (1) in the aliphatic polycarbonate (B) may be a single type or two or more types.

[0054] The structural unit represented by the above general formula (1) is preferably the structural unit represented by the following general formula (1a) from the viewpoint of low-temperature sinterability, crack resistance in film form, and bonding strength of the metal sintered layer.

[0055] (In the formula, R １ , R ２ , R ３ and R ４ Each of these is independently a hydrogen atom or an aliphatic hydrocarbon group (X), and R １ , R ２ , R ３ and R ４ Of these, at least one is an aliphatic hydrocarbon group (X).

[0056] The structural unit represented by the above general formula (1a) is preferably a structural unit represented by the following formula (1a-1) or a structural unit represented by the following formula (1a-2), from the viewpoint of low-temperature sinterability, crack resistance in film form, and bonding strength of the metal sintered layer.

[0057]

[0058] Aliphatic polycarbonate (B) may or may not contain structural units other than carbonate units having an aliphatic hydrocarbon group (X) in their side chains. From the viewpoint of low-temperature sinterability, crack resistance in film form, and bonding strength of the metal sintered layer, the content of carbonate units having an aliphatic hydrocarbon group (X) in their side chains, the structural units represented by the above general formula (1), or the structural units represented by the above general formula (1a) in aliphatic polycarbonate (B) is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more, and may be 100 mol%. Structures derived from carbon dioxide are not counted as a single unit; rather, a structure formed from one monomer molecule and one carbon dioxide molecule (i.e., a structure consisting of a divalent hydrocarbon group and a carbonate group (-O-C(=O)-O-) derived from one monomer molecule) is considered a single unit.

[0059] Specific examples of aliphatic polycarbonate (B) include polybutylene carbonate, polypentylene carbonate, polyhexylene carbonate, polyheptylene carbonate, polyoctylene carbonate, and their derivatives. Among these, polybutylene carbonate is preferred from the viewpoint of low-temperature sinterability, crack resistance in film form, and bonding strength of the metal sintered layer.

[0060] (99% thermal decomposition temperature of aliphatic polycarbonate (B)) The 99% thermal decomposition temperature of aliphatic polycarbonate (B) in a nitrogen atmosphere with an oxygen partial pressure of 0.1 kPa or less (hereinafter also simply referred to as the "99% thermal decomposition temperature") is preferably 400°C or less, more preferably 380°C or less, even more preferably 350°C or less, even more preferably 320°C or less, and particularly preferably 310°C or less. If the 99% thermal decomposition temperature of aliphatic polycarbonate (B) in a nitrogen atmosphere with an oxygen partial pressure of 0.1 kPa or less is below the above upper limit, excellent low-temperature sinterability can be easily obtained in an inert atmosphere. The lower limit of the 99% thermal decomposition temperature of aliphatic polycarbonate (B) is not particularly limited, but from the viewpoint of suppressing the decomposition of aliphatic polycarbonate (B) in the drying process when producing a film-like fired material from a firing paste composition, it may be 170°C or higher, 200°C or higher, or 230°C or higher. Furthermore, the 99% pyrolysis temperature in a nitrogen atmosphere with an oxygen partial pressure of 0.1 kPa or less shall be measured by thermogravimetric analysis (TGA) under atmospheric pressure, and specifically, it can be measured by the method described in the examples.

[0061] (Glass transition temperature (Tg) of aliphatic polycarbonate (B)) The glass transition temperature (Tg) of aliphatic polycarbonate (B) is preferably -40 to +25°C, more preferably -30 to +22°C, even more preferably -20 to +20°C, and even more preferably -10 to +18°C. When the glass transition temperature (Tg) of aliphatic polycarbonate (B) is above the lower limit, adhesion to the member to be joined tends to be better. Also, when the glass transition temperature (Tg) of aliphatic polycarbonate (B) is below the upper limit, crack resistance and shape retention in film form tend to be better. The glass transition temperature (Tg) shall be measured by differential scanning calorimetry (DSC), and specifically can be measured by the method described in the examples.

[0062] (Mass-average molecular weight (Mw) and number-average molecular weight (Mn) of aliphatic polycarbonate (B)) The mass-average molecular weight (Mw) of aliphatic polycarbonate (B) is preferably 5,000 to 1,000,000, more preferably 8,000 to 800,000, even more preferably 10,000 to 500,000, even more preferably 30,000 to 350,000, and even more preferably 50,000 to 150,000. The number-average molecular weight (Mn) of aliphatic polycarbonate (B) is preferably 2,000 to 300,000, more preferably 5,000 to 250,000, even more preferably 10,000 to 200,000, even more preferably 20,000 to 150,000, and even more preferably 30,000 to 100,000. When the mass-average molecular weight (Mw) or number-average molecular weight (Mn) of aliphatic polycarbonate (B) is within the above range, a better balance between crack resistance and shape retention in film form is more likely to be achieved. The mass-average molecular weight (Mw) and number-average molecular weight (Mn) refer to values ​​on a standard polystyrene basis measured by gel permeation chromatography (GPC), and can be measured by the method described in the examples.

[0063] (Method for producing aliphatic polycarbonate (B)) The method for producing aliphatic polycarbonate (B) is not particularly limited, but for example, carbon dioxide (CO2) ２ It can be produced by polymerizing a monomer that forms a divalent aliphatic hydrocarbon group constituting the main chain (hereinafter simply referred to as "raw material monomer"). The conditions for the above polymerization reaction can be, for example, those described in International Publication No. 2011 / 142259.

[0064] Examples of raw material monomers include 1,2-butylene oxide, isobutylene oxide, 1-pentene oxide, 2-pentene oxide, 1-hexene oxide, 1-octen oxide, and their derivatives. Among these, 1,2-butylene oxide or derivatives of 1,2-butylene oxide are preferred. The raw material monomer may be used alone or in combination of two or more.

[0065] The above polymerization reaction is preferably carried out in the presence of a metal catalyst. Examples of metal catalysts include metal salen complex catalysts, complex metal cyanide complex catalysts (DMC catalysts), and organometallic catalysts. Among these, metal salen complex catalysts and DMC catalysts are preferred from the viewpoint of exhibiting high polymerization activity, with cobalt salen complex being more preferred among metal salen complex catalysts, and Zn being preferred among DMC catalysts. ３ (Co[CN] ６ ) ２ This is more preferable. The metal catalyst may be used alone or in combination of two or more types. The amount of metal catalyst used is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 3 parts by mass, per 100 parts by mass of raw material monomer used.

[0066] The polymerization reaction described above may also use a co-catalyst in addition to the metal catalyst. Examples of co-catalysts include bis(triphenylphosphoranylidene)ammonium chloride, 4-dimethylaminopyridine, tetrabutylammonium chloride, tetrabutylammonium bromide, triphenylphosphine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, and 1,4-diazabicyclo[2.2.2]octane. One co-catalyst may be used alone, or two or more may be used in combination. The amount of co-catalyst used is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 14 parts by mass, per 100 parts by mass of the raw material monomer.

[0067] The method for carrying out the polymerization reaction is not particularly limited as long as the target product is obtained, but for example, one method involves charging a starting monomer, a metal catalyst, a co-catalyst, and a solvent to be used as needed into an autoclave, mixing them, and then injecting carbon dioxide into the resulting mixture to carry out the reaction. The solvent used as needed in the polymerization reaction is not particularly limited, but an organic solvent is preferred. The amount of solvent used is preferably 10 to 10,000 parts by mass per 100 parts by mass of monomer used.

[0068] The pressure at which carbon dioxide is injected during the polymerization reaction is preferably 0.1 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 0.1 to 5 MPa. If the pressure at which carbon dioxide is injected is above the lower limit, the polymerization reaction proceeds more easily. Also, if the pressure at which carbon dioxide is injected is below the upper limit, excessive use of carbon dioxide is suppressed, improving economic efficiency.

[0069] The reaction temperature during the polymerization reaction is preferably 20 to 100°C, more preferably 25 to 80°C, from the viewpoint of reaction rate and suppression of side reactions. The reaction time for the polymerization reaction can be adjusted as appropriate according to the reaction temperature, but is preferably 2 to 40 hours.

[0070] During the polymerization reaction, it is preferable to keep the amount of water in the reaction system at 3 mol% or less relative to the amount (moles) of metal catalyst used.

[0071] After the polymerization reaction is complete, the target aliphatic polycarbonate (B) can be isolated by known methods after performing any known post-treatment procedures. The obtained aliphatic polycarbonate (B) may also be purified if necessary.

[0072] The aliphatic polycarbonate (B) content in the firing composition of this embodiment is 4 to 14% by mass relative to the total amount of metal particles (A) and aliphatic polycarbonate (B). When the aliphatic polycarbonate (B) content is above the lower limit, crack resistance in film form is improved. Furthermore, when the aliphatic polycarbonate (B) content is below the upper limit, the effect of suppressing overflow from the edges of the joined members is excellent. From a similar viewpoint, the aliphatic polycarbonate (B) content is preferably 4 to 13% by mass, more preferably 5 to 12% by mass, relative to the total amount of metal particles (A) and aliphatic polycarbonate (B).

[0073] <Solvent (C)> The firing composition of this embodiment may further contain solvent (C). A firing composition containing solvent (C) is suitable as a firing paste composition. Solvent (C) plays the function of dispersing the metal particles (A) and aliphatic polycarbonate (B) in the firing paste composition. Solvent (C) may be used alone or in combination of two or more types.

[0074] The boiling point of solvent (C) is not particularly limited, but is preferably 65 to 350°C, more preferably 100 to 320°C, even more preferably 150 to 300°C, even more preferably 180 to 280°C, and most preferably 200 to 260°C. If the boiling point of solvent (C) is above the lower limit, the volatilization of solvent (C) during the manufacture and storage of the calcination composition is suppressed, resulting in excellent handling. If the boiling point of solvent (C) is below the upper limit, the solvent is easily volatilized after application, making it easier to obtain a calcined material of the desired shape. Furthermore, it is easier to suppress the residue of solvent (C) after drying and calcination of the calcination composition. Note that the boiling point of solvent (C) is the boiling point at 1 atmosphere (101325 Pa).

[0075] Examples of solvents (C) include ketones such as methyl ethyl ketone (2-butanone), methyl isobutyl ketone, cyclohexanone, acetylacetone, and isophorone; ethers such as dioxane and tetrahydrofuran; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated carbons such as dichloromethane and dichloroethane; esters such as methyl acetate, ethyl acetate, and butyl acetate; isopropanol, butanol, cyclohexanol, 1-decanol, and isoborn. Examples include alcohols such as rucyclohexanol; cellosolves such as methyl cellosolve and ethyl cellosolve; glycol ethers or glycol ether acetates such as butyl carbitol, propylene glycol monomethyl ether acetate, butyl carbitol acetate (diethylene glycol monobutyl ether acetate), and ethyl carbitol acetate (diethylene glycol monoethyl ether acetate); cellosolve acetates; sulfoxides such as dimethyl sulfoxide; amides such as dimethylformamide and dimethylacetamide; and the like. Among these, one or more selected from the group consisting of isophorone (boiling point: 215°C), 1-decanol (boiling point: 233°C), isobornylcyclohexanol (boiling point: 318°C), butyl carbitol acetate (boiling point: 245°C), and ethyl carbitol acetate (boiling point: 217°C), which have a boiling point of 200°C or higher, are preferred.

[0076] The solvent (C) content in the firing composition of this embodiment can be appropriately adjusted depending on the form of the firing composition of this embodiment. When the firing composition of this embodiment is a firing paste composition, the solvent (C) content is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, even more preferably 15 to 35% by mass, and even more preferably 20 to 30% by mass, based on the total mass (100% by mass) of the firing composition. When the solvent (C) content is within the above range, the dispersion stability and coating suitability of the firing paste composition tend to be better. In addition, it is easier to suppress the residue of solvent (C) after drying and firing of the firing paste composition.

[0077] <Other Optional Components> The firing composition of this embodiment may contain other optional components besides those listed above, as needed. Examples of other optional components include resins other than aliphatic polycarbonate (B), dispersants, plasticizers, tackifiers, preservatives, defoamers, thermal decomposition accelerators, antioxidants, etc. Each of these may be used individually or in combination of two or more. These additives can be appropriately selected from those commonly used in this field. The content of the above optional components in the firing composition of this embodiment is not particularly limited and may be used as needed, within a range that does not impair the effects of this embodiment. Furthermore, the firing composition of this embodiment may not contain the above optional components, depending on the desired performance.

[0078] The total content of metal particles (A) and aliphatic polycarbonate (B) in the calcination composition of this embodiment is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, even more preferably 97 to 100% by mass, and even more preferably 99 to 100% by mass, based on the total mass (100% by mass) of all components other than the solvent (C), and may also be 100% by mass.

[0079] <Members to be joined and applications of the firing composition> The material of the members to be joined using the firing composition of this embodiment is not particularly limited, and examples include metallic materials such as copper, gold, and aluminum; semiconductor materials such as silicon (Si), germanium, gallium arsenide, gallium phosphide, cadmium sulfide, silicon nitride, graphite, yttrium oxide, magnesium oxide, silicon carbide (SiC), and gallium nitride; plastic materials such as polyimide, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, and polyethylene naphthalate; ceramic materials such as glass; and so on. Multiple members to be joined using the firing composition of this embodiment may be made of the same material or different materials. The joining surfaces of the members to be joined may be provided with a metal film such as a silver film to increase the joining strength.

[0080] The firing composition of this embodiment is suitable for joining components for semiconductor devices. Examples of such components include semiconductor elements, LED elements, substrates, leads, frames, and heat sinks. Among these, the firing composition of this embodiment is particularly suitable for joining semiconductor elements to other components. In particular, since the firing composition of this embodiment can form a metal sintered layer with high thermal conductivity, the semiconductor element to be joined is preferably a power semiconductor element.

[0081] The thickness of the metal sintered layer formed using the firing composition of this embodiment can be adjusted as appropriate depending on the purpose, but from the viewpoint of bonding strength of the metal sintered layer and the effect of suppressing overflow from the edges of the joined members, it is preferably 1 to 100 μm, more preferably 3 to 50 μm, and even more preferably 5 to 25 μm.

[0082] <Film-like firing material> Next, an embodiment of the film-like firing material of this embodiment, which is one embodiment of the firing composition of this embodiment, will be described.

[0083] The total content of metal particles (A) and aliphatic polycarbonate (B) in the film-like fired material of this embodiment is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass.

[0084] The film-like firing material of this embodiment may consist of only one layer, or it may consist of two or more layers. If the film-like firing material consists of two or more layers, the composition of the two or more film-like firing materials may be the same or different.

[0085] The shape of the film-like firing material in this embodiment is not particularly limited and can be set appropriately according to the shape of the joining surface of the members to be joined, however, from the viewpoint of versatility, a circular or rectangular shape is preferred. A circular film-like firing material is suitable for, for example, attachment to a semiconductor wafer. When the film-like firing material is circular, the area of ​​the circle is 3.5 to 1,600 cm². ２ It may also be 85 to 1,400 cm ２This may also be the case. Rectangular film-like fired material is suitable, for example, for application to chips. When the film-like fired material is rectangular, the area of ​​the rectangle is 0.01 to 25 cm². ２ It may also be 0.25 to 9 cm ２ That's fine.

[0086] The thickness of the film-like firing material in this embodiment is not particularly limited and can be appropriately determined depending on the application of the film-like firing material. However, from the viewpoint of film formation properties and versatility, it is preferably 30 to 200 μm, more preferably 40 to 150 μm, and even more preferably 50 to 90 μm.

[0087] [Film-like firing material with release film] The film-like firing material may be a film-like firing material with a release film laminated on at least one surface. The release film is peeled off when using the film-like firing material. The release film functions as a protective film to prevent damage to the film-like firing material, the adhesion of dirt, etc. The release film may be provided on at least one surface of the film-like firing material, or it may be provided on both surfaces of the film-like firing material. The film-like firing material with release film can be manufactured, for example, by applying the firing paste composition of this embodiment onto the release film and then drying it.

[0088] [Film-like firing material with support sheet] The film-like firing material of this embodiment may be a film-like firing material with a support sheet, which is laminated on a support sheet. The support sheet may consist only of a base film, or it may consist of a base film and an adhesive layer provided on the base film. If the support sheet has an adhesive layer, it is preferable that the film-like firing material is laminated on the side of the support sheet that is on the adhesive layer side.

[0089] Examples of base films that make up the support sheet include films made of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene-propylene copolymer, polypropylene, polybutene, polybutadiene, polymethylpentene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-(meth)acrylate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyurethane film, ionomer, etc. When higher heat resistance is required for the support sheet, examples of base films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin films such as polypropylene and polymethylpentene; and others. In addition, crosslinked films of these materials, modified films by radiation or electrical discharge, etc., can also be used.

[0090] Examples of adhesives that make up the adhesive layer include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl ether-based adhesives, and the like.

[0091] A film-like firing material with a support sheet may have a release film on the side of the film-like firing material opposite to the support sheet. For example, a film-like firing material with a support sheet can be manufactured by laminating a film-like firing material with a release film on one side onto a support sheet, with the film-like firing material facing the support sheet.

[0092] [Method for Manufacturing the Firing Composition] The method for manufacturing the firing composition of this embodiment is not particularly limited and can be manufactured by mixing metal particles (A), aliphatic polycarbonate (B), and other components used as needed.

[0093] The method of mixing each component is not particularly limited, and known mixing methods using mixing equipment such as a rotary-orbiting agitator, kneader, three-roll mixer, ball mill, sand mill, planetary mixer, paint shaker, homomixer, homodisper, homogenizer, or ultrasonic disperser can be employed.

[0094] The baking paste composition of this embodiment can be produced, for example, by mixing metal particles (A), aliphatic polycarbonate (B), and a solvent (C) by the method described above.

[0095] The film-like firing material of this embodiment can be manufactured by applying and drying the firing paste composition of this embodiment. In this embodiment, "application" means forming a coating film of the firing paste composition on an object to be coated, and is a concept that also includes the formation of a coating film by "printing".

[0096] In the method for manufacturing a film-like fired material according to this embodiment, the object to which the firing paste composition of this embodiment is applied may be a member to be joined, or it may be a member for supporting the film-like fired material, such as a release film or a support sheet.

[0097] Methods for applying the firing paste composition include, for example, using various coaters such as air knife coaters, blade coaters, bar coaters, gravure coaters, comma coaters (registered trademark), roll coaters, roll knife coaters, curtain coaters, die coaters, knife coaters, screen coaters, Meyer bar coaters, and kiss coaters; and printing methods such as silk screen printing and rotary screen printing. Among these, printing methods are preferred from the viewpoint of easily forming a film-like firing material of the desired shape.

[0098] The drying conditions after applying the baking paste composition can be appropriately determined according to the type of solvent (C), the thickness of the coating, etc. The drying temperature may be, for example, 70 to 250°C, 100 to 200°C, or 120 to 180°C. The drying time may be, for example, 10 seconds to 20 minutes, or 30 seconds to 15 minutes.

[0099] [Method for Manufacturing Semiconductor Devices] The method for manufacturing semiconductor devices according to this embodiment is a method for manufacturing semiconductor devices using the film-like firing composition of this embodiment, and comprises: Step 1: Laminating a semiconductor element and other components via the firing composition to obtain a laminate; Step 2: Heating and pressurizing the laminate to form a metal sintered layer formed by firing the firing composition, thereby obtaining a bonded body in which the semiconductor element and the other components are joined by the metal sintered layer.

[0100] <Step 1> Step 1 is a step to obtain a laminate by laminating a semiconductor element and other components via the film-like firing composition of this embodiment, i.e., a film-like firing material. The semiconductor element and other components can be those listed in the section <Members to be bonded and uses of the firing composition> above, and the preferred embodiment is the same.

[0101] The method for producing the laminate is not particularly limited. For example, it can be produced by laminating a film-like firing material onto the bonding surface of either the semiconductor element or the other component to be bonded, and then attaching the film-like firing material to the bonding surface of the other component.

[0102] <Step 2> Step 2 is a step in which the laminate is heated and pressurized to form a metal sintered layer made of the film-like firing material, and a joint is obtained in which the semiconductor element and the other components are joined by the metal sintered layer.

[0103] The apparatus applicable in step 2 is not particularly limited as long as it is capable of heating and pressurizing the laminate, and examples include a flat plate press, flip chip bonder, die bonder, and autoclave. Among these, it is preferable to use a flat plate press or autoclave that can apply strong pressure.

[0104] From the viewpoint of energy saving, the heating temperature of the laminate in step 2 is preferably 500°C or lower, more preferably 400°C or lower, even more preferably 350°C or lower, and even more preferably 320°C or lower. The lower limit of the heating temperature of the laminate in step 2 can be appropriately determined within the range of temperatures at which the aliphatic polycarbonate (B) decomposes sufficiently, but for example it may be 200°C or higher, or 230°C or higher.

[0105] The pressurizing pressure of the laminate in step 2 may be, for example, 0.1 to 50 MPa, 1 to 40 MPa, or 5 to 30 MPa.

[0106] The heating and pressurizing time for the laminate in step 2 may be, for example, 5 seconds to 180 minutes, 7 seconds to 150 minutes, or 10 seconds to 120 minutes.

[0107] The atmosphere used to heat and pressurize the laminate in step 2 can be, for example, air; nitrogen; noble gases such as helium and argon; reducing gases such as hydrogen and carbon monoxide; etc. Among these, a nitrogen atmosphere is preferred from the viewpoint of suppressing oxidation of the members to be joined and metal particles. The atmosphere used to heat and pressurize the laminate in step 2 is preferably an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the members to be joined and metal particles. The partial pressure of oxygen in an oxygen-free atmosphere is preferably 5.0 kPa or less, more preferably 3.0 kPa or less, even more preferably 1.0 kPa or less, even more preferably 0.5 kPa or less, and particularly preferably 0.1 kPa or less.

[0108] The preferred range for the thickness of the metal sintered layer formed by step 2 is the same as the preferred range for "thickness of the metal sintered layer formed using the firing composition of this embodiment" described above.

[0109] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0110] [Measurement of Thermal Decomposition Temperature of Binder Resin] For the binder resin used in each example, a thermal decomposition test was performed using a thermogravimetric analyzer (TGA; manufactured by Shimadzu Corporation, product name "DTG-60") under the following conditions, and the temperature at which the weight reduction rate of the measured sample reached 99% was defined as the 99% thermal decomposition temperature (T). ｄ９９ ) was obtained as follows. <TGA measurement conditions> Heating rate: 10℃ / min Sample amount: 20-30 mg Measurement temperature range: 40-550℃ Measurement pressure: Atmospheric pressure Measurement atmosphere: Nitrogen atmosphere with oxygen partial pressure of 0.1 kPa or less

[0111] [Measurement of Glass Transition Temperature of Binder Resin] The glass transition temperature (Tg) of the binder resin used in each example was determined by differential scanning calorimetry (DSC) using a DSC Q2000 manufactured by T.A. Instrument Japan Co., Ltd. Specifically, an aluminum pan was used as the container, and under a nitrogen atmosphere, the temperature was raised from -70°C to 150°C at a rate of 10.0°C / min, held for 5 minutes, then cooled to -70°C at a rate of 10.0°C / min, held for 5 minutes, and then raised to 150°C at a rate of 10.0°C / min for measurement.

[0112] [Measurement of Mass-Average Molecular Weight (Mw) and Number-Average Molecular Weight (Mn) of Binder Resins] The mass-average molecular weight (Mw) and number-average molecular weight (Mn) of the binder resins used in each example were measured using a gel permeation chromatograph (Tosoh Corporation, product name "HLC-8320") under the following conditions, and the measurements were converted to standard polystyrene equivalents. In addition, the molecular weight distribution (PDI = Mw / Mn) was calculated from the obtained mass-average molecular weight (Mw) and number-average molecular weight (Mn). <GPC Measurement Conditions> ・Column: A series of "TSK guard column SuperH-H", "TSK gel SuperHM-H", "TSK gel SuperHM-H", and "TSK gel SuperH2000" (all manufactured by Tosoh Corporation) linked together. ・Column temperature: 40°C ・Developing solvent: Tetrahydrofuran (binder resin concentration 1% by mass) ・Injection volume: 20 μl ・Flow rate: 0.6 mL / min ・Detector: Differential refractometer ・Standard sample: Polystyrene

[0113] [Measurement of Metal Particle Size] The film-like fired material obtained in each example was cut in the thickness direction, and the cut surface of the film-like fired material was photographed at a magnification of 10,000x using a scanning electron microscope (SEM) (Carl Zeiss, product name "Crossbeam 550") to obtain an SEM image. Next, the obtained SEM image was binarized using the programming language Python, with a predetermined pixel value as the binarization threshold, to obtain a binarized image divided into white and black. Furthermore, the Blob (Binary Large Object) in the binarized image was detected as a metal particle, the projected area of ​​each metal particle was measured, and the equivalent diameter of a circle was calculated. As a result, it was confirmed that the film-like fired material contained silver particles with a particle size of 1.0 μm or less and copper particles with a particle size exceeding 1.0 μm, which were used as raw materials.

[0114] [Production Example 1] (Synthesis of Polymerization Catalyst) (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanecobalt(II) and pentafluorobenzoic acid were weighed in a molar ratio of 1:1.1 and placed in a flask, to which anhydrous toluene was added. The flask was shielded from light with aluminum foil and reacted at 23°C for 20 hours with stirring. The chemical reaction equation is as follows. After the reaction was complete, the solvent was removed under reduced pressure and washed several times with an excess amount of hexane. Then, vacuum drying was performed at 23°C to obtain the cobalt salen complex, which is the product of the chemical reaction equation shown below.

[0115]

[0116] [Production Example 2] (Production of Polybutylene Carbonate) 100 parts by mass of 1,2-butylene oxide as a raw material monomer, 0.6 parts by mass of the cobalt salen complex obtained in Production Example 1 as a catalyst, and 0.4 parts by mass of bis(triphenylphosphoranylidene)ammonium chloride as a co-catalyst were dissolved in 100 parts by mass of ethyl acetate to obtain a mixture (solid content concentration: 50% by mass). Next, the system of a 4 L autoclave equipped with a stirrer, gas inlet pipe and thermometer was pre-filled with a nitrogen atmosphere, and the above mixture was charged in. Next, while stirring the mixture in the autoclave, carbon dioxide gas was added to the reaction system until the pressure reached 2 MPa. After that, the temperature was raised to 30°C, and the polymerization reaction was carried out for 18 hours while replenishing the carbon dioxide consumed by the reaction. After the reaction was completed, the autoclave was cooled and depressurized, the contents were diluted with ethyl acetate, and the catalyst was removed by reprecipitation purification. The obtained solution was dried to obtain the product, polybutylene carbonate. The obtained polybutylene carbonate had an unsubstituted C2 alkyl group (i.e., an ethyl group) directly bonded to the main chain as a side chain, a glass transition temperature of 16°C, a mass-average molecular weight (Mw) of 86,000, a number-average molecular weight (Mn) of 71,000, and a molecular weight distribution (Mw / Mn) of 1.2.

[0117] [Production Example 3] (Production of Polypropylene Carbonate) Polypropylene carbonate was produced in the same manner as in Production Example 2, except that propylene oxide was used instead of 1,2-butylene oxide. The obtained polypropylene carbonate had an unsubstituted C1 alkyl group (i.e., a methyl group) as a side chain directly bonded to the main chain, a glass transition temperature of 29°C, a mass-average molecular weight (Mw) of 52,600, a number-average molecular weight (Mn) of 43,900, and a molecular weight distribution (Mw / Mn) of 1.2.

[0118] [Manufacturing of firing paste composition and film-like firing material] The components used in the manufacturing of the firing paste composition and film-like firing material are shown below.

[0119] (Metal particle dispersion) Mixed particles were prepared by mixing alcohol derivative-coated silver nanoparticles (particle size 15-55 nm) and copper particles (particle size 2,000-5,000 nm) in a mass ratio (alcohol derivative-coated silver nanoparticles:copper particles) of 1:5. These mixed particles were dispersed in a mixed solvent of isobornylcyclohexanol and decyl alcohol (mass ratio of isobornylcyclohexanol:decyl alcohol = 1:1) as a dispersion medium to prepare metal particle dispersion A with a solid content of 85% by mass.

[0120] (Binder Resin) • Polybutylene carbonate: Polybutylene carbonate synthesized in Production Example 2 • Polypropylene carbonate: Polypropylene carbonate synthesized in Production Example 3 • Acrylic copolymer: 2-ethylhexyl methacrylate (2EHMA) / lauryl methacrylate (LMA) copolymer, copolymer mass ratio (2EHMA / LMA = 70 / 30), mass-average molecular weight (Mw) 250,000, Tg: -29°C (However, the Tg of the acrylic copolymer is a calculated value using Fox's formula.)

[0121] (Solvents) Butyl carbitol acetate, Ethyl carbitol acetate

[0122] [Examples 1-4, Comparative Examples 1-4] (Preparation of paste composition for firing) Metal particle dispersion A, the binder resin shown in Table 1, and the solvent shown in Table 1 were blended so that the amount of binder resin relative to the total amount of metal particles and binder resin was the value shown in Table 1 (for example, in Example 1, 93.0 parts by mass of metal particle dispersion A, 7.0 parts by mass of the binder resin shown in Table 1, and the solvent shown in Table 1 were blended) to adjust the solid content concentration to 75.0% by mass, and the mixture was stirred for 90 seconds using a rotational stirring device (manufactured by Thinky Co., Ltd., product name "ARE-400TWIN") at a rotational speed of 1600 rpm and a rotational speed of 640 rpm. Then, the mixture was stirred again for 90 seconds using the same rotational stirring device at a rotational speed of 1600 rpm and a rotational speed of 640 rpm to obtain a paste composition for firing. Note that the amount of "metal particle dispersion A" refers to the amount including the solvent contained in metal particle dispersion A.

[0123] (Manufacturing of film-like firing material) The firing paste composition obtained above was printed in a circular shape with a diameter of 155 mm on one side of a release film (thickness 38 μm, manufactured by Lintec Corporation, product name "SP-PET382150"), and dried at 150°C for 10 minutes to obtain a film-like firing material with a thickness of 75 μm on the release film.

[0124] [Evaluation Method] The firing paste composition and film-like firing material obtained above were evaluated by the following method. The results are shown in Table 1. Note that in Comparative Example 3, cracks occurred in the film-like firing material and it was not possible to manufacture a joint, so the shear strength of the joint and the effect of suppressing overhang from the ends of the joint members were not measured.

[0125] [Measurement of Shear Strength] (1) Preparation of Laminate A copper plate measuring 30 mm x 30 mm, with a thickness of 1.5 mm and a rectangular shape was prepared as one of the members to be joined. A silver-filmed silicon chip measuring 2 mm x 2 mm, with a thickness of 350 μm and a rectangular shape, with one side covered by a silver film (thickness of 0.5 μm), was prepared as the other member to be joined, with a total thickness of 350.5 μm. The silver film in this silver-filmed silicon chip was formed by vapor deposition. One side of the film-like fired material obtained in each example by peeling off the release film was bonded to the exposed surface of the silver film in the silver-filmed silicon chip. At this time, an excess portion of the film-like fired material was created around the entire outer circumference of the silver film. Then, by cutting and removing the excess portion of the film-like firing material, a laminate was obtained in which silver-coated silicon chips of the same size (2 mm x 2 mm) and the film-like firing material were laminated together. Furthermore, the side of this laminate opposite to the silver-coated silicon chip side of the film-like firing material was bonded to one side of the copper plate. At this time, the copper plate protruded from the entire outer circumference of the laminate. During this process, only the minimum necessary pressure was applied to the film-like firing material to prevent changes in its shape and size. Thus, a laminate was fabricated in which the copper plate, the film-like firing material, and the silver-coated silicon chips were laminated in this order in the thickness direction.

[0126] (2) Manufacturing of the bonded body Aluminum foil (aluminum sheet, 40 μm thick) was laminated over the entire surface of the silver film-coated silicon chip in the laminate obtained above, on the side opposite to the film-like firing material side (i.e., the exposed surface). The entire surface of the exposed copper plate (the side opposite to the film-like firing material side) in the resulting aluminum foil-coated laminate was brought into contact with the surface of one of the two plates in a sintering apparatus (manufactured by Hakuto Co., Ltd., product name "HTM-3000"), and the aluminum foil-coated laminate was placed on this one plate. At this time, the temperature of the one plate was set to 60°C in advance. As a result, the aluminum foil-coated laminate was supported by the one plate in the sintering apparatus, and the aluminum foil-coated laminate was heated from its copper plate side, making it possible to heat it to the same temperature as the other plate, and heating was started. Furthermore, the surface of the other of the two plates in the sintering apparatus was lightly brought into contact with the entire surface of the exposed aluminum foil in the aluminum foil laminate (the surface opposite to the silver film-coated silicon chip side), and this other plate was positioned so as not to intentionally apply pressure to the aluminum foil laminate. At this time, the temperature of the other plate was also set to 60°C in advance. As a result, the aluminum foil laminate was heated from the aluminum foil side by the other plate in the sintering apparatus without intentionally applying pressure to the aluminum foil laminate (effectively applying 0 MPa of pressure), and heating was started to the same temperature as the other plate. Thus, heating of the laminate (aluminum foil laminate) was started at a temperature of 60°C without applying pressure (applying 0 MPa of pressure) in the lamination direction of the copper plate, film-like firing material, and silver film-coated silicon chip.

[0127] Next, the laminate (aluminum foil laminate) was heated by two plates in the sintering apparatus until its temperature reached 60°C, without applying any pressure (the applied pressure was set to 0 MPa) in the stacking direction of the copper plate, the film-like firing material, and the silver-film coated silicon chip. Then, without applying any pressure to the laminate, the laminate was heated by two plates in the sintering apparatus from 60°C to 300°C. The heating rate at this time was 50°C / sec. Immediately after the laminate reached 300°C, a pressure of 10 MPa was applied to the laminate in the stacking direction of the copper plate, the film-like firing material, and the silver-film coated silicon chip, and the temperature of the laminate was maintained at 300°C for 600 seconds. That is, both the pressurization start temperature and the subsequent heating temperature of the film-like firing material were set to 300°C. At this time, pressure was applied to the laminate from the other plate in the sintering apparatus (the aluminum foil side plate). Based on the above, a bonded body was fabricated comprising a copper plate, a metal sintered layer (20 μm thick), and a silicon chip with a silver film, with the copper plate and the silicon chip with the silver film being joined by the metal sintered layer. All of the above steps were carried out under a nitrogen atmosphere. Using the same method as above, four more bonded bodies were fabricated, for a total of five bonded bodies.

[0128] (3) Evaluation of the bonding strength of the joint Under conditions of 23°C, a force was applied at a speed of 200 μm / s in a direction parallel to the surface of the silicon chip (the side of the silicon chip without the silver film) to the aligned portion of the joint obtained above, where the outer circumference (side) of the metal sintered layer and the outer circumference (side) of the silver film-coated silicon chip were aligned. At this time, a stainless steel plate-shaped object was used as the pressing means for applying the force, and the position of the tip of this pressing means was set at a height of 20 μm from the surface of the copper plate in the joint (the side facing the metal sintered layer) so that the pressing means did not come into contact with the copper plate. The maximum value of the force applied until the metal sintered layer was destroyed or the metal sintered layer peeled off from the copper plate was defined as the shear strength. The same test was performed on all five joints, and the average value was defined as the shear strength of the joint.

[0129] [Evaluation of the effect of suppressing overflow from the ends of the joined members] The joined body prepared for the above shear strength measurement was observed using a digital microscope (manufactured by Keyence Corporation, product name "VHX-7000") to measure the distance of the firing composition that overflowed from the ends of the silicon chips that were to be joined, and the effect of suppressing overflow during joining was evaluated according to the following criteria. (Evaluation criteria) A: The maximum overflow distance is less than 150 μm. F: The maximum overflow distance is 150 μm or more.

[0130] [Evaluation of crack resistance of film-like fired material] When the film-like fired material manufactured in each example was attached to the member to be bonded using a wafer mounter (Lintec Corporation, product name "RAD-2510F / 12"), it was checked whether or not cracks occurred in the film-like fired material within the wafer mounter, and the crack resistance of the film-like fired material was evaluated according to the following criteria. Note that the highest gripping angle in the roll (diameter 4.0 cm, hardness 30 degrees) within the wafer mounter was 175°. (Evaluation criteria) A: No cracks were observed in the film-like fired material. F: Cracks were observed in the film-like fired material.

[0131] *1: This refers to the content (mass %) of the binder resin relative to the total amount of metal particles (A) and binder resin (aliphatic polycarbonate (B), acrylic copolymer, etc.).

[0132] Table 1 shows that the firing composition of this embodiment exhibits excellent low-temperature sinterability and crack resistance in film form, and can suppress overflow from the edges of the joined members.

Claims

1. A calcination composition comprising: metal particles (A) having a particle size of 1.0 μm or less; and an aliphatic polycarbonate (B), wherein the aliphatic polycarbonate (B) has substituted or unsubstituted aliphatic hydrocarbon groups having 2 to 6 carbon atoms in its side chains, either directly or via oxygen atoms to the main chain; and the content of the aliphatic polycarbonate (B) relative to the total amount of the metal particles (A) and the aliphatic polycarbonate (B) is 4 to 14% by mass.

2. The calcination composition according to claim 1, wherein the aliphatic polycarbonate (B) has a structural unit represented by the following general formula (1a). (In the formula, R １ , R ２ , R ３ and R ４ Each is independently a hydrogen atom or a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 6 carbon atoms, R １ , R ２ , R ３ and R ４ Of these, at least one is a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 6 carbon atoms.

3. Only any one of R in the general formula (1a) １ , R ２ , R ３ and R ４ is the substituted or unsubstituted aliphatic hydrocarbon group having 2 to 6 carbon atoms, the composition for firing according to claim 2.

4. The calcination composition according to claim 1, wherein the substituted or unsubstituted C2-C6 aliphatic hydrocarbon group is a substituted or unsubstituted C2-C6 linear aliphatic hydrocarbon group.

5. The firing composition according to claim 1, wherein the metal particles (A) are one or more metal particles selected from the group consisting of silver particles, gold particles, copper particles, iron particles, nickel particles, aluminum particles, tungsten particles, molybdenum particles, silicon particles, palladium particles, platinum particles, titanium particles, and barium titanate particles, oxide particles of the metal constituting the metal particles, or alloy particles of the metal constituting the metal particles.

6. The firing composition according to claim 1, used for joining semiconductor elements to other components.

7. The firing composition according to claim 6, wherein the semiconductor element is a power semiconductor element.

8. The calcination composition according to any one of claims 1 to 7, further comprising a solvent (C) and being in the form of a paste.

9. A firing composition according to any one of claims 1 to 7, which is in the form of a film.

10. A method for manufacturing a semiconductor device using the film-like firing composition described in claim 9, comprising: step 1 of stacking a semiconductor element and other components via the firing composition to obtain a laminate; and step 2 of heating and pressurizing the laminate to form a metal sintered layer by firing the firing composition, thereby obtaining a bonded body in which the semiconductor element and the other components are joined by the metal sintered layer.

11. The method for manufacturing a semiconductor device according to claim 10, wherein the heating temperature in step 2 is 320°C or lower.

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