SHEET FOR SINTERING BONDING AND SHEET FOR SINTERING BONDING WITH BASE MATERIAL

Abstract

To provide a sheet for sintering bonding and a sheet for sintering bonding with a base material that are suited for being made with a good operational efficiency and that are also suited for realizing a satisfactory operational efficiency in a sintering process in a process of producing a semiconductor device that goes through sintering bonding of semiconductor chips. A sheet for sintering bonding 10 of the present invention comprises an electrically conductive metal containing sinterable particle and a binder component, and has a shear strength at 23 C. of 2 to 40 MPa measured in accordance with a SAICAS method. A sheet body X, which is a sheet for sintering bonding with a base material according to the present invention, has a laminated structure comprising a base material B and the sheet for sintering bonding 10.

Claims

1. A sheet for sintering bonding, comprising: an electrically conductive metal containing sinterable particle; and a binder component, the sheet for sintering bonding having a shear strength at 23 C. of 2 to 40 MPa measured in accordance with a SAICAS method.

2. The sheet for sintering bonding according to claim 1, the sheet for sintering bonding having a shear strength at 100 C. of 20 MPa or less measured in accordance with the SAICAS method.

3. A sheet for sintering bonding with a base material, having a laminated structure comprising a base material and the sheet for sintering bonding according to claim 1.

4. A sheet for sintering bonding with a base material, having a laminated structure comprising a base material and the sheet for sintering bonding according to claim 2.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a partial schematic cross sectional drawing of a sheet for sintering bonding with a base material according to one embodiment of the present invention.

[0027] FIGS. 2(a) to 2(c) represents some steps in a method for producing a semiconductor device carried out by using the sheet for sintering bonding with a base material shown in FIG. 1.

[0028] FIG. 3 represents a step subsequent to the step shown in FIGS. 2(a) to 2(c).

[0029] FIG. 4 represents a step subsequent to the step shown in FIG. 3.

[0030] FIGS. 5(a) to 5(b) represents a step subsequent to the step shown in FIG. 4.

[0031] FIGS. 6(a) to 6(b) represents a step subsequent to the step shown in FIGS. 5(a) to 5(b).

DESCRIPTION OF EMBODIMENTS

[0032] FIG. 1 is a partial schematic cross sectional drawing of a sheet body X, which is a sheet for sintering bonding with a base material according to one embodiment of the present invention. The sheet body X has a laminated structure comprising a base material B and a sheet for sintering bonding 10 according to one embodiment of the present invention.

[0033] The base material B is an element that functions as a support in the sheet body X. The base material B is, for example, a plastic base material, and as such a plastic base material, a plastic film can be suitably used. Examples of the constituent material for the plastic base material include, for example, polyolefins, polyesters, polyurethanes, polycarbonates, polyetheretherketones, polyimides, polyetherimides, polyamides, wholly aromatic polyamides, polyvinyl chlorides, polyvinylidene chlorides, polyphenyl sulfides, aramids, fluororesins, cellulosic resins, and silicone resins. Examples of the polyolefin include, for example, low density polyethylenes, linear low density polyethylenes, medium density polyethylenes, high density polyethylenes, very low density polyethylenes, random copolymerized polypropylenes, block copolymerized polypropylenes, homopolypropylenes, polybutenes, polymethylpentenes, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylate ester copolymers, ethylene-butene copolymers, and ethylene-hexene copolymers. Examples of the polyester include, for example, polyethylene terephthalates, polyethylene naphthalates, and polybutylene terephthalates. The base material B may be formed of one kind of material, or may be formed of two or more kinds of materials. The base material B may have a single layer structure, or may have a multilayer structure. When the base material B is formed of a plastic film, such a base material B may be a nonoriented film, may be a uniaxially oriented film, or may be a biaxially oriented film. Alternatively, the base material B may be a pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet, such as a dicing tape, having a layer of a pressure-sensitive adhesive forming an adhesive face on the side of the sheet for sintering bonding 10. That layer of a pressure-sensitive adhesive may be a layer of an ultraviolet curable pressure-sensitive adhesive, which is cured by ultraviolet irradiation, thereby decreasing the adhesive strength.

[0034] The sheet for sintering bonding 10 is a composition for sintering bonding having the shape of a sheet, at least comprising an electrically conductive metal containing sinterable particle and a binder component, the composition being used for sintering-bonding the bonding objects therebetween. The sheet for sintering bonding 10 may have a predetermined planar view shape, such as a circular shape or a rectangular shape, on the base material B. Alternatively, on a single base material B, a plurality of sheets for sintering bonding 10 having predetermined planar view shapes may be provided.

[0035] The sinterable particle in the sheet for sintering bonding 10 is a particle that contains an electrically conductive metallic element and can be sintered. Examples of the electrically conductive metallic element include, for example, gold, silver, copper, palladium, tin, and nickel. Examples of the constituent material for such a sinterable particle include, for example, gold, silver, copper, palladium, tin, nickel, and an alloy of two or more kinds of metals selected from the group thereof. Examples of the constituent material for the sinterable particle also include metal oxides, such as silver oxide, copper oxide, palladium oxide, and tin oxide. In addition, the sinterable particle may be a particle having a core shell structure. For example, the sinterable particle may be a particle with a core shell structure, having a core mainly composed of copper and a shell mainly composed of gold or silver and covering the core. In the present embodiment, the sinterable particle preferably comprises at least one selected from the group consisting of a silver particle, a copper particle, a silver oxide particle and a copper oxide particle. Such a configuration is preferable from the viewpoint of forming a rigid sintered layer between the bonding objects to be sintering-bonded using the sheet for sintering bonding 10. Moreover, from the viewpoint of achieving high electrical conductivity and high thermal conductivity in a sintered layer to be formed, a silver particle and a copper particle are preferable as the sinterable particle. In addition, from the viewpoint of oxidation resistance, a silver particle is easily handled and is thus preferable. For example, in sintering bonding of a semiconductor chip to a copper substrate with silver plate, when a sintering material containing a copper particle as the sinterable particle is used, it is necessary to carry out the sintering process under an inert environment such as under a nitrogen atmosphere; however, when a sintering material in which a silver particle acts as the sinterable particle is used, the sintering process can be properly conducted even in an air atmosphere.

[0036] The average particle diameter of the sinterable particle to be used is preferably 10000 nm or less, more preferably 3000 nm or less, more preferably 1000 nm or less, and more preferably 500 nm or less from the viewpoint of ensuring the flatness of the surface of the sheet for sintering bonding 10. With respect to the sinterable particle in the sheet for sintering bonding 10 or the composition for forming the sheet, from the viewpoint of realizing satisfactory dispersibility, the average particle diameter of the sinterable particle is preferably 1 nm or more, more preferably 10 nm or more, and more preferably 50 nm or more. The average particle diameter of the sinterable particle can be measured by carrying out observation using a scanning electron microscope (SEM).

[0037] In the sheet for sintering bonding 10, the content of the sinterable particle is preferably 60 to 99% by mass, more preferably 65 to 98% by mass, and more preferably 70 to 97% by mass from the viewpoint of realizing sintering bonding with high reliability.

[0038] In the present embodiment, the binder component in the sheet for sintering bonding 10 at least comprises a high molecular binder and/or a low molecular binder (preferably, a low molecular binder), and may further comprise an additional component such as a plasticizer.

[0039] The high molecular binder in the sheet for sintering bonding is preferably a thermally decomposable high molecular binder. The thermally decomposable high molecular binder is a binder component that can be thermally decomposed during the heating process at high temperature for sintering bonding, and is an element that contributes to retention of the sheet shape of the sheet for sintering bonding 10 until the initiation of that heating process. In the present embodiment, from the viewpoint of securing a function of retaining the sheet shape, the thermally decomposable high molecular binder is a solid material at ordinary temperature (23 C.). Examples of such a thermally decomposable high molecular binder may include, for example, a polycarbonate resin and an acrylic resin. The sheet for sintering bonding 10 preferably comprises a polycarbonate resin and/or an acrylic resin as the high molecular binder or the thermally decomposable high molecular binder.

[0040] Examples of the above polycarbonate resin include, for example, aliphatic polycarbonates having a backbone of carboxylate ester groups (OCOO) not comprising an aromatic compound, such as a benzene ring, therebetween and formed of aliphatic chains, and aromatic polycarbonates having a backbone of carboxylate ester groups (OCOO) comprising an aromatic compound therebetween. Examples of the aliphatic polycarbonate include, for example, polyethylene carbonates and polypropylene carbonates. Examples of the aromatic polycarbonate include polycarbonates comprising a bisphenol A structure in the backbone thereof.

[0041] Examples of the above acrylic resin include, for example, polymers of an acrylate ester and/or a methacrylate ester having a linear or branched alkyl group having 4 to 18 carbon atoms. Hereinafter, acrylic and/or methacrylic are represented by (meth)acrylic, and acrylate and/or methacrylate are represented by (meth)acrylate. Examples of the alkyl group of the (meth)acrylate ester forming an acrylic resin as the thermally decomposable high molecular binder include, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a n-butyl group, a t-butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a heptyl group, a cyclohexyl group, a 2-ethylhexyl group, an octyl group, an isooctyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, an undecyl group, a lauryl group, a tridecyl group, a tetradecyl group, a stearyl group, and an octadecyl group.

[0042] The above acrylic resin may be a polymer comprising a monomer unit derived from an additional monomer other than the above (meth)acrylate ester. Examples of such an additional monomer include, for example, carboxy group containing monomers, acid anhydride monomers, hydroxy group containing monomers, sulfonic acid group containing monomers, and phosphoric acid group containing monomers. Specifically, examples of the carboxy group containing monomer include, for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the acid anhydride monomer include, for example, maleic anhydride and itaconic anhydride. Examples of the hydroxy group containing monomer include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and 4-(hydroxymethyl)cyclohexylmethyl (meth)acrylate. Examples of the sulfonic acid group containing monomer include, for example, styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid. Examples of the phosphoric acid group containing monomer include, for example, 2-hydroxyethylacryloyl phosphate.

[0043] The weight average molecular weight of the high molecular binder or the thermally decomposable high molecular binder contained in the sheet for sintering bonding 10 is preferably 10000 or more. The weight average molecular weight of the high molecular binder is defined to be a value obtained through measurement with gel permeation chromatography (GPC) and calculation in terms of polystyrene.

[0044] The content of the high molecular binder or the thermally decomposable high molecular binder contained in the sheet for sintering bonding 10 is preferably 0 to 20% by mass, more preferably 0.1 to 20% by mass, more preferably 0.5 to 18% by mass, more preferably 1 to 15% by mass, further preferably 1 to 6% by mass, and particularly preferably 1 to 5% by mass from the viewpoint of properly exhibiting the function of retaining the sheet shape mentioned above.

[0045] The low molecular binder in the sheet for sintering bonding 10 is preferably a low boiling point binder. The low boiling point binder is a binder component having a boiling point lower than the thermal decomposition starting temperature of the high molecular binder such as a thermally decomposable high molecular binder. In the present embodiment, the low boiling point binder is defined to be liquid or semi-liquid, exhibiting a viscosity at 23 C. of 110.sup.5 Pa.Math.s or less, which is measured by using an apparatus for measuring dynamic viscoelasticity (trade name: HAAKE MARS III, manufactured by Thermo Fisher Scientific K.K.). In the present viscosity measurement, 20 mm parallel plates are used as jigs, the gap between the plates is 100 m, and the shear velocity in rotational shear is 1 s.sup.1.

[0046] Examples of the low boiling point binder mentioned above include, for example, terpene alcohols, alcohols excluding terpene alcohols, alkylene glycol alkyl ethers, and ethers excluding alkylene glycol alkyl ethers. Examples of the terpene alcohol include, for example, isobornyl cyclohexanol, citronellol, geraniol, nerol, carveol, and -terpineol. Examples of the alcohol excluding terpene alcohols include, for example, pentanol, hexanol, heptanol, octanol, 1-decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, and 2,4-diethyl-1,5-pentanediol. Examples of the alkylene glycol alkyl ether include, for example, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, and tripropylene glycol dimethyl ether. Examples of the ether excluding alkylene glycol alkyl ethers include, for example, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, and dipropylene glycol methyl ether acetate. As a component in the sheet for sintering bonding 10, one kind of low boiling point binder may be used, or two or more kinds of low boiling point binders may be used. The low boiling point binder in the sheet for sintering bonding 10 is preferably a terpene alcohol, and is more preferably isobornyl cyclohexanol from the viewpoint of stability at ordinary temperature.

[0047] The molecular weight of the low molecular binder is not particularly limited, and for example, it is 500 or less, preferably 450 or less, more preferably 400 or less, further preferably 350 or less, and particularly preferably 300 or less. In addition, the molecular weight of the low molecular binder is, for example, 50 or more, preferably 100 or more, more preferably 150 or more, and further preferably 200 or more.

[0048] The boiling point of the low boiling point binder is not particularly limited as long as it is lower than the thermal decomposition starting temperature of the high molecular binder such as a thermally decomposable high molecular binder, and for example, it is 500 C. or less, preferably 450 C. or less, more preferably 400 C. or less, and further preferably 350 C. or less. In addition, the boiling point of the low boiling point binder is, for example, 50 C. or more, preferably 100 C. or more, more preferably 150 C. or more, further preferably 200 C. or more, and particularly preferably 250 C. or more.

[0049] The content of the low molecular binder, such as a low boiling point binder, in the sheet for sintering bonding 10 is, for example, 1 to 50% by mass, preferably 2 to 50% by mass, and more preferably 2.5 to 40% by mass from the viewpoint of ensuring satisfactory tackiness on the surface of that sheet.

[0050] The proportion between the high molecular binder and the low molecular binder (low boiling point binder) in the sheet for sintering bonding 10 (high molecular binder/low molecular binder) is not particularly limited, and for example, it is 3 or less, preferably 2.5 or less, more preferably 2.0 or less, and further preferably 1.5 or less from the viewpoint of ensuring satisfactory tackiness and adhesiveness on the surface of that sheet. In addition, when the proportion is in the above range, it is suitable from the viewpoint of adjusting the shear strength at 23 C. of the sheet for sintering bonding 10, measured in accordance with the SAICAS method, in a predetermined range. On the other hand, the proportion is, for example, 0.1 or more, preferably 0.15 or more, and more preferably 0.2 or more from the viewpoint of properly exhibiting the function of retaining the sheet shape of the sheet for sintering bonding 10.

[0051] The thickness of the sheet for sintering bonding 10 at 23 C. is preferably not less than 5 m, more preferably not less than 10 m, and preferably not more than 300 m, more preferably not more than 150 m.

[0052] In the sheet for sintering bonding 10, the shear strength at 23 C. (the first shear strength) measured in accordance with the SAICAS method is 2 to 40 MPa, preferably 2 to 35 MPa, and more preferably 2 to 32 MPa.

[0053] In the sheet for sintering bonding 10, the shear strength at 100 C. (the second shear strength) measured in accordance with the SAICAS method is preferably 20 MPa or less, more preferably 9 MPa or less, and more preferably 7 MPa or less.

[0054] The shear strength measured in accordance with the SAICAS method is defined to be a shear strength (shear failure strength) measured by using SAICAS (Surface And Interfacial Cutting Analysis System), which is an apparatus manufactured by DAIPLA WINTES CO., LTD., under conditions with a cutting blade having a blade width of 1 mm, a rake angle of 10, and a relief angle of 10; a constant velocity mode in which the horizontal velocity of the cutting blade is 10 m/sec and the vertical velocity thereof is 0.5 m/sec; and a predetermined temperature. This apparatus can perform diagonal cutting with a cutting blade to a material layer, which is a measurement object on a base material, and from the data pertaining to the horizontal force and the vertical force exerted on the cutting blade during the cutting process, as well as the vertical displacement of the cutting blade, the shear strength of the material layer and the like can be determined. For example, adjustment of the above shear strength of the sheet for sintering bonding 10 can be carried out by adjusting the respective amounts of the high molecular binder and the low molecular binder to be compounded in the sheet for sintering bonding 10, or by adjusting the viscoelasticity with respect to the high molecular binder.

[0055] The sheet for sintering bonding 10 or the composition for sintering bonding forming this has a viscosity at 70 C. of, for example, 510.sup.3 to 110.sup.7 Pa.Math.s, and preferably 110.sup.4 to 110.sup.6 Pa.Math.s.

[0056] The sheet for sintering bonding 10 can be made by, for example, mixing the respective components mentioned above in a solvent to prepare a varnish, applying such a varnish on the base material B to form a coating film, and then drying that coating film. For the solvent for preparing a varnish, an organic solvent or an alcoholic solvent can be used.

[0057] FIG. 2(a) to FIG. 6(b) represent some steps of a method of producing a semiconductor device carried out by using the sheet body X or the sheet for sintering bonding 10 mentioned above. The present method is a method for producing a semiconductor device, such as a power semiconductor device comprising sintering bonding portions of semiconductor chips.

[0058] In the present method, at first, as shown in FIG. 2(a), the sheet body X having the sheet for sintering bonding 10 mentioned above, and a plurality of chips C are provided. Each of a plurality of chips C is a semiconductor chip in which a predetermined semiconductor element has already been fabricated. A plurality of chips C is arranged on an adhesive face T1a of a tape for processing T1, with a gap between the adjoining chips. Examples of the constituent material for forming the chip body of chips C include, for example, semiconductor materials for power semiconductor devices, such as silicon carbide (SiC) or gallium nitride (GaN). The thickness of the chip C is, for example, 20 to 1000 m. In each chip C, an external electrode (not shown in the figure) has already been formed on the surface on the side to which the sheet for sintering bonding 10 is to be laminated (in FIGS. 2(a) to 2(c), the top face in the figure). The external electrode is, for example, a silver planar electrode, and the thickness thereof is, for example, 10 nm to 1000 nm. A silver planar electrode as the external electrode may be laminated and formed on a titanium thin film that has been formed on the surface of the semiconductor chip. The thickness of that titanium thin film is, for example, 10 nm to 1000 nm. These silver planar electrode and titanium thin film can be formed through, for example, a vapor deposition method. In addition, on the other face of each chip C (in FIGS. 2(a) to 2(c), the bottom face in the figure), another external electrode (not shown in the figure) has been formed, if necessary.

[0059] In the present method of producing a semiconductor device, next, a transfer step is carried out. In the transfer step, at first, as shown in FIG. 2(b), the side of the sheet for sintering bonding 10 of the sheet body X is pressure-bonded against a plurality of chips C on the tape for processing T1, thereby laminating them. Examples of the pressing means for the lamination include, for example, a pressure roller. The lamination temperature is, for example, in the range from room temperature to 200 C., and preferably 65 to 75 C. The load for the lamination is, for example, 0.01 to 10 MPa. After the lamination, as shown in FIG. 2(c), while leaving a part of the sheet for sintering bonding 10 on the side of the chip C, a separation operation of the base material B is carried out. Through such lamination operation and subsequent separation operation, transfer of the material for sintering bonding from the sheet for sintering bonding 10 to each chip C is carried out, and a layer of the material for sintering bonding 11, which is a small piece of the sheet for sintering bonding cut apart from the surroundings, occurs on the chip C. In the present step, the material for sintering bonding can be collectively supplied to every chip C.

[0060] In the present method of producing a semiconductor device, next, as shown in FIG. 3, the chip C is picked up from the tape for processing T1 along with the part in the sheet for sintering bonding 10 that has been closely adhered to the chip C, thereby obtaining a chip C accompanied by the layer of the material for sintering bonding 11 (a picking up step). In the picking up step of the present embodiment, specifically, the chip C to be picked up is pushed up via the tape for processing T1 by raising a pin member 21 of a picking up mechanism at the lower side of the tape for processing T1 in the figure. After such pushing up, the chip C is adsorbed to and retained by an adsorption collet 22 through an adsorptive action to the side of the layer of the material for sintering bonding 11. As such, the picking up of the chip C with the layer of the material for sintering bonding 11 can be carried out.

[0061] In the present embodiment, next, as shown in FIG. 4, the chip C with the layer of the material for sintering bonding is delivered from the adsorption collet 22 that has picked up the chip C to another adsorption collet 23. The adsorption collet 23 retains the chip C through an adsorptive action to the side of the chip of the chip C with the layer of the material for sintering bonding.

[0062] Next, as shown in FIG. 5(a), the chip C with the layer of the material for sintering bonding is pressure-bonded to a supporting substrate S via that layer of the material for sintering bonding 11, and is fixed temporarily (a temporary fixation step). Specifically, the chip C with the layer of the material for sintering bonding is pressed against the supporting substrate S via that layer of the material for sintering bonding 11 by, for example, using a chip mounter, and is fixed temporarily. Examples of the supporting substrate S include, for example, an insulating circuit substrate accompanied by a wiring such as a copper wiring on the surface thereof, and a lead frame. The portion of the supporting substrate S, on which the chip is mounted, may be the bare surface of a copper wiring or a lead frame, or may be the surface of a plated film formed on the bare surface. Examples of such a plated film include, for example, a gold plated film, a silver plated film, a nickel plated film, a palladium plated film, and a platinum plated film. In the present step, the temperature conditions for the temporary fixation are, for example, in the range from room temperature to 300 C., the load with respect to the pressing is, for example, 0.01 to 50 MPa, and the bonding time is, for example, 0.01 to 300 seconds.

[0063] Next, as shown in FIG. 5(b), a sintered layer 12 is formed through a heating process from the layer of the material for sintering bonding 11 intervening between the temporarily fixed chip C and the supporting substrate S, and the chip C is sintering-bonded to the supporting substrate S (a sintering bonding step). Specifically, by going through a predetermined heating process at high temperature, the low molecular binder in the layer of the material for sintering bonding 11 is volatilized between the supporting substrate S and the chip C, and all of or a part of the high molecular binder is thermally decomposed and vaporized, if necessary, and then, the electrically conductive metal of the sinterable particle is sintered. Due to this, the sintered layer 12 is formed between the supporting substrate S and the chip C, and the chip C is bonded to the supporting substrate S while making an electrical connection with the side of supporting substrate S. In the present step, the temperature conditions for the sintering bonding are, for example, in the range of 150 to 400 C. The pressure for the sintering bonding is, for example, 60 MPa or less. In addition, the bonding time of the sintering bonding is, for example, 0.3 to 300 minutes. For example, within the range of these conditions, the temperature profile and the pressure profile for performing the sintering bonding step are appropriately set. The sintering bonding step as described above can be carried out by using an apparatus that can carry out heating and pressurization at the same time. Examples of such an apparatus include, for example, a flip chip bonder and a parallel plate pressing machine. In addition, from the viewpoint of preventing oxidation of the metal that is involved in the sintering bonding, it is preferable that the present step be carried out under a nitrogen atmosphere, under reduced pressure, or under a reducing gas atmosphere.

[0064] In the present method of producing a semiconductor device, next, as shown in FIG. 6(a), an electrode part (not shown in the figure) of the chip C and a terminal part (not shown in the figure) that the supporting substrate S has are electrically connected via a bonding wire W, if necessary (a wire bonding step). The wire connection between the electrode part of the chip C or the terminal part of the supporting substrate S and the bonding wire W is realized through, for example, ultrasonic welding involving heating. As the bonding wire W, for example, a gold wire, an aluminum wire, or a copper wire can be used. The wire heating temperature in the wire bonding is, for example, 80 to 250 C. In addition, the heating time thereof is, for example, a few seconds to a few minutes.

[0065] Next, as shown in FIG. 6(b), a sealing resin R is formed for protecting the chip C and the bonding wire W on the supporting substrate S (a sealing step). In the present step, for example, the sealing resin R is formed through a transfer mold technology, which is carried out by using a metal mold. As the constituent material for the sealing resin R, for example, an epoxy resin can be used. In the present step, the heating temperature for forming the sealing resin R is, for example 165 to 185 C., and the heating time is, for example, 60 seconds to a few minutes. When curing of the sealing resin R does not proceed sufficiently in the present sealing step, after the present step, a subsequent curing step is carried out for completely curing the sealing resin R.

[0066] As described above, a semiconductor device comprising sintering bonding portions of semiconductor chips can be produced.

[0067] The sheet for sintering bonding 10 in the sheet body X has a shear strength at 23 C. (a first shear strength) of 2 to 40 MPa measured in accordance with the SAICAS method, as mentioned above. The present inventors have obtained a finding that, with respect to a sheet body of a composition containing an electrically conductive metal containing sinterable particle and a binder component, a configuration in which the shear strength at 23 C. measured in accordance with the SAICAS method under the above conditions is 2 to 40 MPa is suited for obtaining a satisfactory cuttability while retaining the sheet shape thereof. For example, this is shown by Examples and Comparative Examples, which will be described later. In the sheet for sintering bonding 10, a configuration in which the shear strength at 23 C. measured in accordance with the SAICAS method under the above conditions is 2 MPa or more is suitable from the viewpoint of handling the sheet for sintering bonding 10 as a material retaining the shape of a sheet. In the sheet for sintering bonding 10, a configuration in which the shear strength at 23 C. measured in accordance with the SAICAS method under the above conditions is 40 MPa or less is suitable from the viewpoint where the sheet for sintering bonding 10 is not stiffened too much, exhibiting a satisfactory cuttability. With respect to the sheet for sintering bonding 10, from the viewpoint of its satisfactory cuttability, the shear strength at 23 C. measured in accordance with the SAICAS method is preferably 2 to 35 MPa, and more preferably 2 to 32 MPa. The sheet for sintering bonding 10, which is suited for obtaining a satisfactory cuttability, is suited for properly performing cleaving or punch processing in the process of making the sheet, and is thus suited for being made with a good operational efficiency. Along with this, the sheet for sintering bonding 10, which is suited for obtaining a satisfactory cuttability, is suited for allowing a layer of the material for sintering bonding 11, which is a small piece of the sheet for sintering bonding 10 cut apart from the surroundings, to occur on the semiconductor chip in the transfer step mentioned above in the process of producing a semiconductor device. That is, the sheet for sintering bonding 10 is suited for properly performing the transfer step mentioned above, in which the material for sintering bonding is collectively supplied to a plurality of semiconductor chips. Such a sheet for sintering bonding 10 is suited for realizing a satisfactory operational efficiency in the sintering process in the process of producing a semiconductor device comprising sintering bonding portions of semiconductor chips.

[0068] As described above, the sheet for sintering bonding 10 is suited for being made with a good operational efficiency and is also suited for realizing a satisfactory operational efficiency in the sintering process in the process of producing a semiconductor device comprising sintering bonding portions of semiconductor chips.

[0069] In the sheet for sintering bonding 10 in the sheet body X, as mentioned above, the shear strength at 100 C. (the second shear strength) measured in accordance with the SAICAS method is preferably 20 MPa or less, more preferably 9 MPa or less, and more preferably 7 MPa or less. In the sheet for sintering bonding 10, a configuration in which the shear strength at 23 C. (the first shear strength) measured in accordance with the SAICAS method is 2 to 40 MPa, as mentioned above, and the shear strength at 100 C. (the second shear strength) measured in accordance with the same method is 20 MPa or less is suitable from the viewpoint of ensuring a satisfactory cuttability of the sheet for sintering bonding 10 in the temperature range of 23 to 100 C. In addition, the temperature at which the transfer step mentioned above is performed in the process of producing a semiconductor device is 70 C. and the vicinity thereof, and may be included in the temperature range of 23 to 100 C. The above configuration in which the first shear strength is 2 to 40 MPa and the second shear strength is 20 MPa or less is suitable for ensuring a satisfactory cuttability of the sheet for sintering bonding 10 at the temperature at which the transfer step is performed, for example, 70 C. and the vicinity thereof, and is thus suitable for properly performing the transfer step mentioned above by using the sheet for sintering bonding 10.

[0070] The binder component of the sheet for sintering bonding 10 preferably comprises a thermally decomposable high molecular binder, as mentioned above. According to such a configuration, at a temperature for the temporary fixation mentioned above, for example, at 70 C., and in the temperature range close thereto, by utilizing the viscoelasticity of the thermally decomposable high molecular binder, the cohesive strength of the sheet for sintering bonding 10 or the layer of the material for sintering bonding 11 derived therefrom is likely to be ensured, and accordingly, the adhesive strength of the sheet for sintering bonding 10 or the layer of the material for sintering bonding 11 is likely to be ensured. As such, the present configuration is suitable from the viewpoint of, upon or after pressure-bonding bonding objects in a state where the layer of the material for sintering bonding 11 derived from the sheet for sintering bonding 10 intervenes between the bonding objects, suppressing occurrence of position aberration in these bonding objects.

[0071] The weight average molecular weight of the high molecular binder, such as a thermally decomposable high molecular binder, in the sheet for sintering bonding 10 is preferably 10000 or more, as mentioned above. Such a configuration is suitable from the viewpoint of ensuring the cohesive strength or adhesive strength of the sheet for sintering bonding 10 or the layer of the material for sintering bonding 11 derived therefrom by utilizing the viscoelasticity of the high molecular binder.

[0072] The high molecular binder, such as a thermally decomposable high molecular binder, in the sheet for sintering bonding 10 preferably comprises a polycarbonate resin and/or an acrylic resin, as mentioned above. As mentioned above, in the process of using the sheet for sintering bonding 10 to realize sintering bonding, heating at high temperature for sintering bonding is carried out in a state where the bonding objects are temporarily fixed therebetween with the layer of the material for sintering bonding 11 derived from the sheet for sintering bonding 10. When the heating at high temperature for sintering bonding is carried out at, for example, 300 C. and in the temperature range including the vicinity thereof, a polycarbonate resin and an acrylic resin are easily provided as a high molecular binder that is decomposed and vaporized at a temperature of approximately 300 C. Accordingly, the present configuration is suitable from the viewpoint of reducing an organic residue in a sintered layer 12 formed between the bonding objects to be sintering-bonded using the sheet for sintering bonding 10. As the amount of the organic residue in the sintered layer 12 becomes smaller, that sintered layer 12 tends to be more rigid, and accordingly, high reliability for bonding is likely to be obtained in that sintered layer 12.

[0073] The low molecular binder in the sheet for sintering bonding 10 comprises a low boiling point binder having a boiling point lower than the thermal decomposition starting temperature of the high molecular binder, as mentioned above. Such a configuration is suited for ensuring satisfactory tackiness in the sheet for sintering bonding 10, and is therefore suited for ensuring satisfactory adhesiveness to other members such as the chip C and the base material B. As such, the present configuration is suitable from the viewpoint of, upon or after pressure-bonding bonding objects in a state where the layer of the material for sintering bonding 11 derived from the sheet for sintering bonding 10 intervenes between the bonding objects, suppressing occurrence of position aberration in these bonding objects.

[0074] In the sheet for sintering bonding 10, the content of the sinterable particle is preferably 60 to 99% by mass, more preferably 65 to 98% by mass, and more preferably 70 to 97% by mass. Such a configuration is suitable from the viewpoint of attempting to make the density of the sintered layer 12 formed from the sheet for sintering bonding 10 higher.

EXAMPLES

Example 1

[0075] By using a hybrid mixer (trade name: HM-500, manufactured by Keyence Corporation) at its stirring mode, 56.35 parts by mass of a silver particle as a sinterable particle P.sub.1, 1.7 parts by mass of a polycarbonate resin as a high molecular binder (a thermally decomposable high molecular binder) (trade name: QPAC 40, the weight average molecular weight is 150000, solid at ordinary temperature, manufactured by Empower Materials), 2.55 parts by mass of isobornyl cyclohexanol as a low molecular binder (a low boiling point binder) (trade name: Terusolve MTPH, liquid at ordinary temperature, manufactured by NIPPON TERPENE CHEMICALS, INC.), and 39.4 parts by mass of methyl ethyl ketone as a solvent were mixed to prepare a varnish. The stirring time was set to be 3 minutes. The above silver particle as the sinterable particle P.sub.1 comprises the first silver particle (the average particle diameter: 60 nm, manufactured by DOWA Electronics Materials Co., Ltd.) and the second silver particle (the average particle diameter: 1100 nm, manufactured by MITSUI MINING & SMELTING CO., LTD.) at a mass ratio of 9:1. Then, the obtained varnish was applied on a mold release film as a base material (trade name: MRA 38, manufactured by Mitsubishi Chemical Corporation), and subsequently dried to form a sheet for sintering bonding with a thickness of 55 m. The drying temperature was set to be 110 C., and the drying time was set to be 3 minutes. In the sheet for sintering bonding, the content of the sinterable particle is 93.0% by mass. As described above, the sheet for sintering bonding of Example 1, containing the sinterable particle, the high molecular binder and the low molecular binder, was made on the base material. The composition pertaining to the sheet for sintering bonding of Example 1 is reported in Table 1 (The same applies to Examples and Comparative Examples described below. In addition, in Table 1, the unit of each numerical value representing the composition is a relative part by mass).

Example 2

[0076] A sheet for sintering bonding of Example 2 was made in the same manner as the sheet for sintering bonding of Example 1 except that the amount of the sinterable particle P.sub.1 to be compounded was changed from 56.35 parts by mass to 56.16 parts by mass; the amount of the polycarbonate resin (trade name: QPAC 40, manufactured by Empower Materials) to be compounded was changed from 1.7 parts by mass to 2.63 parts by mass; the amount of isobornyl cyclohexanol (trade name: Terusolve MTPH, manufactured by NIPPON TERPENE CHEMICALS, INC.) to be compounded was changed from 2.55 parts by mass to 1.76 parts by mass; and the amount of methyl ethyl ketone to be used was changed from 39.4 parts by mass to 39.45 parts by mass. With respect to the sheet for sintering bonding of Example 2, the content of the sinterable particle is 92.7% by mass, and the thickness is 52 m.

Example 3

[0077] A sheet for sintering bonding of Example 3 was made in the same manner as the sheet for sintering bonding of Example 1 except that the amount of the sinterable particle P.sub.1 to be compounded was changed from 56.35 parts by mass to 56.98 parts by mass; the amount of the polycarbonate resin (trade name: QPAC 40, manufactured by Empower Materials) to be compounded was changed from 1.7 parts by mass to 0.75 parts by mass; the amount of isobornyl cyclohexanol (trade name: Terusolve MTPH, manufactured by NIPPON TERPENE CHEMICALS, INC.) to be compounded was changed from 2.55 parts by mass to 2.98 parts by mass; and the amount of methyl ethyl ketone to be used was changed from 39.4 parts by mass to 39.29 parts by mass. With respect to the sheet for sintering bonding of Example 3, the content of the sinterable particle is 93.9% by mass, and the thickness is 53 m.

Example 4

[0078] A sheet for sintering bonding of Example 4 was made in the same manner as the sheet for sintering bonding of Example 1 except that 66.11 parts by mass of a copper particle as a sinterable particle P2 (the average particle diameter: 200 nm, manufactured by MITSUI MINING & SMELTING CO., LTD.) was used instead of 56.35 parts by mass of the sinterable particle P.sub.1; the amount of the polycarbonate resin (trade name: QPAC 40, manufactured by Empower Materials) to be compounded was changed from 1.7 parts by mass to 3.57 parts by mass; the amount of isobornyl cyclohexanol (trade name: Terusolve MTPH, manufactured by NIPPON TERPENE CHEMICALS, INC.) to be compounded was changed from 2.55 parts by mass to 5.35 parts by mass; and the amount of methyl ethyl ketone to be used was changed from 39.4 parts by mass to 24.97 parts by mass. With respect to the sheet for sintering bonding of Example 4, the content of the sinterable particle is 88.1% by mass, and the thickness is 68 m.

Example 5

[0079] A sheet for sintering bonding of Example 5 was made in the same manner as the sheet for sintering bonding of Example 1 except that the amount of the sinterable particle P.sub.1 to be compounded was changed from 56.35 parts by mass to 56.69 parts by mass; the polycarbonate resin was not used; the amount of isobornyl cyclohexanol (trade name: Terusolve MTPH, manufactured by NIPPON TERPENE CHEMICALS, INC.) to be compounded was changed from 2.55 parts by mass to 3.98 parts by mass; and the amount of methyl ethyl ketone to be used was changed from 39.4 parts by mass to 39.33 parts by mass. With respect to the sheet for sintering bonding of Example 5, the content of the sinterable particle is 93.4% by mass, and the thickness is 55 m.

Comparative Example 1

[0080] A sheet for sintering bonding of Comparative Example 1 was made in the same manner as the sheet for sintering bonding of Example 1 except that the amount of the sinterable particle P.sub.1 to be compounded was changed from 56.35 parts by mass to 55.99 parts by mass; the amount of the polycarbonate resin (trade name: QPAC 40, manufactured by Empower Materials) to be compounded was changed from 1.7 parts by mass to 3.64 parts by mass; the amount of isobornyl cyclohexanol (trade name: Terusolve MTPH, manufactured by NIPPON TERPENE CHEMICALS, INC.) to be compounded was changed from 2.55 parts by mass to 0.91 parts by mass; and the amount of methyl ethyl ketone to be used was changed from 39.4 parts by mass to 39.46 parts by mass. With respect to the sheet for sintering bonding of Comparative Example 1, the content of the sinterable particle is 92.5% by mass, and the thickness is 57 m.

Comparative Example 2

[0081] A sheet for sintering bonding of Comparative Example 2 was made in the same manner as the sheet for sintering bonding of Example 1 except that the amount of the sinterable particle P.sub.1 to be compounded was changed from 56.35 parts by mass to 56.69 parts by mass; the polycarbonate resin and isobornyl cyclohexanol were not used; and the amount of methyl ethyl ketone to be used was changed from 39.4 parts by mass to 43.31 parts by mass. The thickness of the sheet for sintering bonding of Comparative Example 2 is 48 m.

<Shear Strength>

[0082] With respect to each of the sheets for sintering bonding (accompanied by the base material on one side) of Examples 1 to 5 and Comparative Examples 1 and 2, the shear strength at 23 C. (the first shear strength) was measured in accordance with the SAICAS method carried out by using a diagonal cutting apparatus manufactured by DAIPLA WINTES CO., LTD., SAICAS DN-20 model. A cutting blade for the diagonal cutting in the present measurement has a blade width of 1 mm, a rake angle of 10, and a relief angle of 10. The present measurement was carried out under temperature conditions of 23 C. at a constant velocity mode (the horizontal velocity of the cutting blade is 10 m/sec and the vertical velocity thereof is 0.5 m/sec). In addition, in the same manner as above expect that the temperature conditions were changed from 23 C. to 100 C., with respect to each of the sheets for sintering bonding (accompanied by the base material on one side) of Examples 1 to 5 and Comparative Examples 1 and 2, the shear strength at 100 C. (the second shear strength) was measured in accordance with the SAICAS method carried out by using a SAICAS DN-20 model. Results of these measurements are reported in Table 1. In the diagonal cutting to the material layer, from the horizontal force F.sub.H exerted on the cutting blade, the area of the shear plane D, and the shear angle (an angle formed by the shear plane relative to the finished face through the diagonal cutting), the shear strength FS can be derived from the calculation formula: F.sub.S=(F.sub.H/2D)cot , and in the diagonal cutting process to the sheet for sintering bonding, the maximum value of F.sub.S exhibited in a region with a depth of 30 to 70% from the exposed face of the sheet relative to the entire thickness of the sheet was defined to be the shear strength (MPa) with respect to each measurement (with respect to the sheet for sintering bonding of Comparative Example 2, which was not able to retain the sheet shape thereof at 100 C., it was not possible to measure the second shear strength).

<Sheet Cuttability>

[0083] With respect to each of the sheets for sintering bonding (accompanied by the base material on one side) of Examples 1 to 5 and Comparative Examples 1 and 2, the cuttability was examined as follows. At first, the sheet for sintering bonding accompanied by the base material was mounted on a teflon tape (trade name: NITOFLON No. 900UL, the thickness: 100 m, manufactured by NITTO DENKO CORPORATION), having the side of the base material closely adhered to the tape. Next, on that sheet for sintering bonding, a silicon chip with a size of 5 mm square (the thickness: 200 m) was mounted. The base material accompanying the sheet for sintering bonding is MRA 38 (the thickness: 38 m) manufactured by Mitsubishi Chemical Corporation. Subsequently, to the chip on the sheet for sintering bonding, a pressurization treatment toward the sheet for sintering bonding was carried out. In this pressurization treatment, the load is 10 MPa, the pressurization time is 5 seconds, and the pressurization temperature is 70 C. (Examples 1 to 3 and 5, and Comparative Examples 1 and 2) or 90 C. (Example 4). After such a pressurization treatment, the cutting state around the chip in the sheet for sintering bonding was observed. Then, with regard to the cuttability of the sheet for sintering bonding, the case where the sheet for sintering bonding was cut along the entire circumference around the chip (that is, the case where the sheet for sintering bonding was cut such that a small piece of the sheet for sintering bonding corresponding to the chip occurs) was evaluated as satisfactory, and the case where not the entire circumference around the chip was cut in the sheet for sintering bonding was evaluated as unsatisfactory. The evaluation results are reported in Table 1.

[Evaluation]

[0084] The sheets for sintering bonding of Examples 1 to 5, having a shear strength at 23 C. of 2 to 40 MPa measured in accordance with the SAICAS method, exhibited a satisfactory cuttability in the test for evaluating the cuttability mentioned above.

TABLE-US-00001 TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Example 2 Sintera P.sub.1 (silver 56.35 56.16 56.98 56.69 55.99 56.69 particle particle) P.sub.2 (copper 66.11 particle) High Polycarbonate 1.7 2.63 0.75 3.57 3.64 molecular resin binder Low Isobornyl 2.55 1.76 2.98 5.35 3.98 0.91 molecular cyclohexanol binder Solvent Methyl ethyl 39.4 39.45 39.29 24.97 39.33 39.46 43.31 used ketone Thickness of sheet for 55 52 53 68 55 57 48 sintering bonding (m) First shear strength (MPa) 24.4 31.6 11 7.53 2.19 43.6 0.12 Second shear strength (MPa) 4.91 6.87 5.34 6.79 3.53 9.07 Sheet cuttability Satisfactory Satisfactory Satisfactory Satisfactory Satisfactory Unsatisfactory Unsatisfactory

[0085] As a summary of the above, the configuration of the present invention and variations thereof will be enumerated as clauses below.

[Clause 1]

[0086] A sheet for sintering bonding, comprising an electrically conductive metal containing sinterable particle and a binder component, and having a shear strength at 23 C. of 2 to 40 MPa measured in accordance with a SAICAS method.

[Clause 2]

[0087] The sheet for sintering bonding according to clause 1, having a shear strength at 100 C. of 20 MPa or less measured in accordance with the SAICAS method.

[Clause 3]

[0088] The sheet for sintering bonding according to clause 1 or 2, wherein the binder component comprises a high molecular binder and/or a low molecular binder.

[Clause 4]

[0089] The sheet for sintering bonding according to clause 3, wherein the high molecular binder comprises a thermally decomposable high molecular binder.

[Clause 5]

[0090] The sheet for sintering bonding according to clause 3 or 4, wherein a weight average molecular weight of the high molecular binder is 10000 or more.

[Clause 6]

[0091] The sheet for sintering bonding according to any one of clauses 3 to 5, wherein the high molecular binder comprises a polycarbonate resin and/or an acrylic resin.

[Clause 7]

[0092] The sheet for sintering bonding according to any one of clauses 3 to 6, wherein the low molecular binder comprises a low boiling point binder having a boiling point lower than a thermal decomposition starting temperature of the high molecular binder.

[Clause 8]

[0093] The sheet for sintering bonding according to any one of clauses 3 to 7, wherein a proportion between the high molecular binder and the low molecular binder (high molecular binder/low molecular binder) is 3 or less, preferably 2.5 or less, more preferably 2.0 or less, and further preferably 1.5 or less.

[Clause 9]

[0094] The sheet for sintering bonding according to any one of clauses 1 to 8, wherein the sinterable particle comprises at least one selected from the group consisting of a silver particle, a copper particle, a silver oxide particle and a copper oxide particle.

[Clause 10]

[0095] The sheet for sintering bonding according to any one of clauses 1 to 9, wherein a content of the sinterable particle is 60 to 99% by mass, preferably 65 to 98% by mass, and more preferably 70 to 97% by mass.

[Clause 11]

[0096] A sheet for sintering bonding with a base material, having a laminated structure comprising a base material and the sheet for sintering bonding according to any one of clauses 1 to 10.

REFERENCE SIGNS LIST

[0097] X1 Sheet body [0098] B Base material [0099] 10 Sheet for sintering bonding [0100] 11 Layer of material for sintering bonding [0101] 12 Sintered layer [0102] T1, T2 Tape for processing [0103] C Chip (semiconductor chip) [0104] S Supporting substrate (substrate)