Semiconductor device manufacturing method

Provided is a semiconductor device manufacturing method which can suppress the occurrence of positional deviation or inclination of a semiconductor element when the semiconductor element is fixed so as to be sandwiched-between two insulating substrates. The semiconductor device manufacturing method includes: obtaining a laminated body in which a semiconductor element is temporarily adhered on a first electrode formed on a first insulating substrate with a first pre-sintering layer sandwiched therebetween; temporarily adhering the semiconductor element on a second electrode formed on a second insulating substrate with a second pre-sintering layer sandwiched therebetween, the second pre-sintering layer being provided on a side opposite to the first pre-sintering layer, to obtain a semiconductor device precursor; and simultaneously heating the first pre-sintering layer and the second pre-sintering layer, to bond the semiconductor element to the first electrode and the second electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Japanese Patent Application No. 2015-225440, filed on Nov. 18, 2015, in the Japanese Patent Office. Further, this application is the National Phase application of International Application No. PCT/JP2016/079522 filed on Oct. 4, 2016, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a semiconductor device such as a thermoelectric conversion module.

BACKGROUND ART

Conventionally, a thermoelectric conversion module has a configuration in which a plurality of P-type thermoelectric elements and N-type thermoelectric elements are alternately arranged, and fixed so as to be sandwiched between two insulating substrates (see, for example, Patent Document 1). On each of the insulating substrates, electrodes are formed at positions corresponding to the thermoelectric elements, and the P-type thermoelectric elements and the N-type thermoelectric elements are electrically connected in series in order.

Patent Document 1 discloses a method of manufacturing a thermoelectric conversion module in which a highly-adhesive flux is applied to at least one of an insulating substrate and solder plating attached to a thermoelectric element to temporarily fix the thermoelectric element to the insulating substrate, followed by soldering using solder plating while applying heat.

In Patent Document 1, one surface of the thermoelectric element is temporarily fixed to an electrode of one of the insulating substrates, followed by heating to bond the thermoelectric element to the electrode. Then, an electrode of the other insulating substrate is bonded to the other surface of the thermoelectric element.

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

However, the method of Patent Document 1 uses a solder for bonding, and the insulating substrate which has been already bonded is also heated when heating is performed in order to bond the other insulating substrate, which causes the solder to be re-melted, so that the positional deviation or inclination of the thermoelectric element may occur.

The present invention has been made in view of the above problems, and an object thereof is to provide a semiconductor device manufacturing method which can suppress the occurrence of positional deviation or inclination of a semiconductor element when the semiconductor element is fixed so as to be sandwiched between two insulating substrates.

Means for Solving the Problems

In order to solve the above-mentioned conventional problems, the present inventors studied a semiconductor device manufacturing method. As a result, it has been found that the occurrence of positional deviation or inclination of a semiconductor element can be suppressed by adopting the following configuration, and the present invention was completed.

That is, a semiconductor device manufacturing method according to the present invention includes:

a step A of obtaining a laminated body in which a semiconductor element is temporarily adhered on a first electrode formed on a first insulating substrate, with a first pre-sintering layer sandwiched therebetween;

a step B of, after the step A, temporarily adhering the semiconductor element on a second electrode formed on a second insulating substrate, with a second pre-sintering layer sandwiched therebetween, the second pre-sintering layer being provided on a side opposite to the first pre-sintering layer, to obtain a semiconductor device precursor; and

a step C of, after the step B, simultaneously heating the first pre-sintering layer and the second pre-sintering layer, to bond the semiconductor element to the first electrode and the second electrode.

According to the above configuration, the semiconductor element is first temporarily adhered on the first electrode formed on the first insulating substrate and the second electrode formed on the second insulating substrate. Then, the first pre-sintering layer and the second pre-sintering layer are simultaneously heated, to bond the semiconductor element to the first electrode and the second electrode. That is, by heating once, the semiconductor element and the first electrode are bonded, and the semiconductor element and the second electrode are bonded. Since the bonding of both the surfaces of the semiconductor element is completed by heating once, the re-melting of the pre-sintering layer does not occur. As a result, the occurrence of positional deviation or inclination of the semiconductor element can be suppressed.

The semiconductor element is temporarily adhered on the first pre-sintering layer and the second pre-sintered layer, which makes it unnecessary to use a mold or the like for preventing the falling of the semiconductor element. As a result, the breakage of the semiconductor element due to the rubbing of the mold or the like can be prevented.

The temporary adhesion is provided by using the first pre-sintering layer and the second pre-sintering layer as a bonding material, which does not separately require a tape or an adhesive for temporary fixing. Therefore, the semiconductor device manufacturing method is economically excellent.

It is preferable that, in the above configuration, the semiconductor element has a first surface on which the first pre-sintering layer is stacked and a second surface on which the second pre-sintering layer is stacked after the step A and before the step B.

After the step A and before the step B, the first pre-sintering layer is stacked on the first surface of the semiconductor element, and the second pre-sintering layer is stacked on the second surface, which allows the step B to be performed without performing the step of forming the second pre-sintering layer after the step A.

It is preferable that, in the above configuration, the semiconductor element having the first surface on which the first pre-sintering layer is stacked and the second surface on which the second pre-sintering layer is stacked is obtained by the following steps X and Y:

the step X of forming the first pre-sintering layer on a first surface of a semiconductor wafer and forming the second pre-sintering layer on a second surface of the semiconductor wafer, to obtain the semiconductor wafer including the pre-sintering layer formed on each of both the surfaces; and

the step Y of making the semiconductor wafer obtained in the step X and including the pre-sintering layer formed on each of both the surfaces into individual pieces.

According to the above configuration, the semiconductor wafer is made into individual pieces in a state where the sintering pre-layer is formed on each of both the surfaces of the semiconductor wafer, which makes it possible to efficiently obtain the semiconductor wafer including the pre-sintering layer formed on each of both the surfaces.

It is preferable that, in the above configuration, the first pre-sintering layer and the second pre-sintering layer contain a metal-based compound.

The first pre-sintering layer and the second pre-sintering layer contain the metal-based compound, which provides good electrical connection with low electrical resistance after bonding.

It is preferable that, in the above configuration, in the step X, a sheet-like first pre-sintering layer is stacked on the first surface of the semiconductor wafer, and a sheet-like second pre-sintering layer is stacked on the second surface of the semiconductor wafer, to obtain the semiconductor wafer including the pre-sintering layer formed on each of both the surfaces.

The sheet-like pre-sintering layer has a relatively uniform thickness. Therefore, according to the above configuration, the sheet-like pre-sintering layer is used, which allows the inclination of the semiconductor element to be further suppressed.

It is preferable that, in the above configuration, the semiconductor element is a thermoelectric element.

The semiconductor element is the thermoelectric element, which makes it possible to obtain a thermoelectric conversion module in which the positional deviation or inclination of the thermoelectric element is suppressed.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a semiconductor device manufacturing method according to an embodiment will be described with reference to the drawings. Prior to this, a first pre-sintering layer and a second pre-sintering layer used in the present embodiment will be described.

A first pre-sintering layer52according to the present embodiment (seeFIGS. 1 and 4) is a layer serving as a sintered layer after being heated.

In the present embodiment, a case will be described, in which the first pre-sintering layer is one layer serving as a sintered layer after being heated, but the present invention is not limited to this example. The layer serving as a sintered layer after being heated in the present invention may have a configuration in which a plurality of layers serving as a sintered layer after being heated are stacked.

The thickness of the first pre-sintering layer52is preferably 5 μm to 200 μm, more preferably 10 μm to 150 μm, and still more preferably 15 μm to 100 μm. The thickness of the first pre-sintering layer52before being heated to the above range is set, which allows maintenance of a sheet shape, and thickness uniformity to be secured.

The first pre-sintering layer52is pasted on a test chip (semiconductor chip, length: 2 mm×width: 2 mm, thickness: 3 mm) under the conditions of 0.5 MPa, 10 seconds, and 80° C. by a parallel plate press. The shear strength (shear strength assumed during temporary adhesion) of the test chip, on which the first pre-sintering layer52has been pasted, at room temperature (24° C.) is preferably in the range of 0.01 MPa to 1.0 MPa, and more preferably in the range of 0.1 MPa to 0.9 MPa.

Specifically, the shear strength is a value measured under the following conditions using Bond Tester 5000 Series for ultra-fine pitch bonding, manufactured by Nordson Advanced Technology Japan K. K. (former name: Dage Japan Co., Ltd.).

Test type: Destructive test

The first pre-sintering layer52is pasted on a test chip (semiconductor chip, length: 2 mm×width: 2 mm, thickness: 3 mm) under the conditions of 0.5 MPa, 10 seconds, and 80° C. by a parallel plate press. Then, the test chip on which the first pre-sintering layer52has been pasted is heated under the conditions of 1 MPa, 90 seconds, and 300° C. by a parallel plate press. The shear strength (shear strength assumed after thermal bonding) of the test chip at room temperature (24° C.) is preferably in the range of 2 MPa to 100 MPa, and more preferably in the range of 10 MPa to 90 MPa.

Specifically, the shear strength is a value measured under the following conditions using Multipurpose Bond Tester 4000 series manufactured by Nordson Advanced Technology Japan K. K. (former name: Dage Japan Co., Ltd.).

Test type: Destructive test

It is preferable that the hardness of the first pre-sintering layer52after being heated under the following heating condition A is in the range of 1.5 GPa to 10 GPa in measurement using a nanoindenter. The hardness is more preferably in the range of 2.0 GPa to 8 GPa, and still more preferably in the range of 2.5 GPa to 7 GPa. The following heating condition A is a heating condition prescribed by assuming a condition that the first pre-sintering layer52serves as a sintered layer after being heated. A method of measuring hardness using the nanoindenter is based on a method described in examples.

The first pre-sintering layer52is heated from 80° C. to 300° C. at a heating rate of 1.5° C./sec under pressure of 10 MPa, and then held at 300° C. for 2.5 minutes.

When the hardness is 1.5 GPa or more, the sintered layer obtained by heating the first pre-sintering layer52is solid. When the hardness is 10 GPa or less, the sintered layer obtained by heating the first pre-sintering layer52has appropriate flexibility.

The hardness can be controlled by the kind, content, and average particle diameter of metal fine particles, the kind and content of a thermally decomposable binder, the kind and content of a low-boiling binder, heating conditions when a sintered layer is formed by heating (for example, a temperature, a time, a heating rate, or the like), an atmosphere when the sintered layer is formed (air atmosphere, nitrogen atmosphere, reducing gas atmosphere, or the like).

The modulus of elasticity of the first pre-sintering layer52after being heated under the following heating condition A is preferably in the range of 30 GPa to 150 GPa in measurement using a nanoindenter. The modulus of elasticity is more preferably in the range of 35 GPa to 120 GPa, and still more preferably in the range of 40 GPa to 100 GPa. The following heating condition A is a heating condition prescribed by assuming a condition that the first pre-sintering layer52serves as a sintered layer after being heated. A method of measuring the modulus of elasticity using a nanoindenter is based on a method described in examples.

The first pre-sintering layer52is heated from 80° C. to 300° C. at a heating rate of 1.5° C./sec under pressure of 10 MPa, and then held at 300° C. for 2.5 minutes.

When the modulus of elasticity is 30 GPa or more, the sintered layer obtained by heating the first pre-sintering layer52is solid. When the modulus of elasticity is 150 GPa or less, the sintered layer obtained by heating the first pre-sintering layer52has appropriate flexibility.

The modulus of elasticity can be controlled by the kind, content, and average particle diameter of metal fine particles, the kind and content of a thermally decomposable binder, the kind and content of a low-boiling binder, heating conditions when a sintered layer is formed by heating (for example, a temperature, a time, a heating rate, or the like), an atmosphere when the sintered layer is formed (air atmosphere, nitrogen atmosphere, reducing gas atmosphere, or the like).

It is preferable that the deformation amount of the first pre-sintering layer52according to a deformation measurement method B described below is in the range of 1600 nm to 1900 nm. The deformation amount is more preferably in the range of 1620 nm to 1880 nm, and still more preferably in the range of 1650 nm to 1850 nm.

(1) A step of heating the first pre-sintering layer52from 80° C. to 300° C. at a heating rate of 1.5° C./sec under pressure of 10 MPa, and then holding the first pre-sintering layer52at 300° C. for 2.5 minutes to obtain a layer for measuring a deformation amount; and

(2) a step of pushing the layer for measuring a deformation amount by a pushing depth of 2 μm using a nanoindenter, releasing the pushing, and then measuring a deformation amount from before the pushing.

A more detailed deformation amount measurement method is based on a method described in examples.

When the deformation amount is 1900 nm or less, the obtained sintered layer is solid, and has improved reliability. On the other hand, when the deformation amount is 1600 nm or more, the obtained sintered layer has an elastic deformation region, and has improved reliability.

The first pre-sintering layer52has a carbon concentration of preferably 15% by weight or less, more preferably 12% by weight or less, and still more preferably 10% by weight or less. The carbon concentration is obtained by energy dispersive X-ray spectrometry after being heated from 23° C. to 400° C. in the air atmosphere at a heating rate of 10° C./min. When the carbon concentration is 15% by weight or less, an organic matter is hardly present in first pre-sintering layer52heated to 400° C. This provides excellent heat resistance after a thermal bonding step, and high reliability and heat characteristics even in a high-temperature environment.

In the first pre-sintering layer52, a peak when differential thermal analysis is performed while heating from 23° C. to 500° C. in the air atmosphere at a heating rate of 10° C./min is preferably present at 150 to 350° C., more preferably 170 to 320° C., and still more preferably 180 to 310° C. When the peak is present at 150 to 350° C., an organic matter (for example, a resin component constituting the first pre-sintering layer52) can be said to be thermally decomposed in this temperature range. This provides more excellent heat resistance after the thermal bonding step.

The first pre-sintering layer52preferably contains a metal-based compound. Examples of the metal-based compound include Au-based, Ag-based, and Cu-based metal fine particles.

Examples of the metal fine particles include sintering metal particles.

As the sintering metal particles, an aggregate of metal fine particles can be suitably used. Examples of the metal fine particles include fine particles made of a metal. Examples of the metal include gold, silver, copper, silver oxide, and copper oxide. Among these, the metal is preferably at least one selected from the group consisting of silver, copper, silver oxide, and copper oxide. The metal fine particles are made of at least one selected from the group consisting of silver, copper, silver oxide, and copper oxide, which can provide more suitable thermal bonding.

The average particle diameter of the sintering metal particles is preferably 0.0005 μm or more, and more preferably 0.001 μm or more. Examples of the lower limit of the average particle diameter include 0.01 μm, 0.05 μm, and 0.1 μm. On the other hand, the average particle diameter of the sintering metal particles is preferably 30 μm or less, and more preferably 25 μm or less. Examples of the upper limit of the average particle diameter include 20 μm, 15 μm, 10 μm, and 5 μm.

The average particle diameter of the sintering metal particles is measured by the following method. That is, the sintering metal particles are observed by a SEM (scanning electron microscope), to measure an average particle size. During SEM observation, for example, micro-sized sintering metal particles are preferably observed at a magnification of 5,000; submicron-sized sintering metal particles are preferably observed at a magnification of 50,000; and nano-sized sintering metal particles are preferably observed at a magnification of 300,000.

Examples of the shape of the sintering metal particles include a spherical shape, a rod shape, a scale shape, and an infinite shape without particular limitation.

The first pre-sintering layer52preferably contains metal fine particles in an amount in the range of 60 to 98% by weight relative to the entire first pre-sintering layer52. The content of the metal fine particles is more preferably in the range of 65 to 97% by weight, and still more preferably in the range of 70 to 95% by weight. When the metal fine particles are contained in the range of 60 to 98% by weight, the metal fine particles can be sintered or melted to bond two objects (for example, a semiconductor element and an electrode).

The first pre-sintering layer52preferably contains a low-boiling binder. The low-boiling binder is used to facilitate the handling of the metal fine particles. The low-boiling binder is also used to adjust optional mechanical properties. Specifically, the low-boiling binder can be used as a metal fine particles-containing paste in which the metal fine particles are dispersed in the low-boiling binder.

The low-boiling binder is liquid at 23° C. Herein, the term “liquid” includes semiliquid. Specifically, it means that viscosity at 23° C. obtained by viscosity measurement with a dynamic viscoelasticity measuring device (rheometer) is 100,000 Pa·s or less.

Conditions for viscosity measurement are as follows.

Rheometer: MER III manufactured by Thermo SCIENTIFIC

The first pre-sintering layer52preferably contains a thermally decomposable binder which is a solid at 23° C. When the first pre-sintering layer52contains the thermally decomposable binder, the shape of the sheet is likely to be maintained before the thermal bonding step. During the thermal bonding step, the first pre-sintering layer52is likely to be thermally decomposed.

Herein, the term “solid” specifically means that viscosity at 23° C. obtained by viscosity measurement with the rheometer is more than 100,000 Pa·s.

Herein, the term “thermally decomposable binder” refers to a binder which can be thermally decomposed in the thermal bonding step. It is preferable that the thermally decomposable binder hardly remains in the sintered layer (the first pre-sintering layer52after being heated) after the thermal bonding step. Examples of the thermally decomposable binder include a material having a carbon concentration of 15% by weight or less obtained by energy dispersive X-ray spectrometry after being heated from 23° C. to 400° C. in the air atmosphere at a heating rate of 10° C./min even if the first pre-sintering layer52contains the material. For example, by adopting a material which is more likely to be thermally decomposed as the thermally decomposable binder, the material is allowed to hardly remain in the sintered layer (the first pre-sintering layer52after being heated) after the thermal bonding step even if the content of the material is comparatively increased.

Examples of the thermally decomposable binder include polycarbonate, an acrylic resin, ethylcellulose, and polyvinyl alcohol. These materials can be used singly or in combination of two or more. Among these, from the viewpoint of high thermal decomposability, polycarbonate is preferable.

The polycarbonate is not particularly limited as long as the polycarbonate can be thermally decomposed in the thermal bonding step. Examples of the polycarbonate include aliphatic polycarbonate containing an aliphatic chain without containing an aromatic compound (for example, a benzene ring or the like) between ester carbonate groups (—O—CO—O—) as a main chain, and aromatic polycarbonate containing an aromatic compound between ester carbonate groups (—O—CO—O—) as a main chain. Among these, aliphatic polycarbonate is preferred.

Examples of the aliphatic polycarbonate include polyethylene carbonate and polypropylene carbonate. Among these, polypropylene carbonate is preferred from the viewpoint of solubility in an organic solvent when a varnish for forming a sheet is produced.

Examples of the aromatic polycarbonate include those having a bisphenol A structure as a main chain.

The weight average molecular weight of the polycarbonate is suitably in a range of 10,000 to 1,000,000. The weight average molecular weight is a value that is measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

Examples of the acrylic resin include a polymer (acrylic copolymer) containing, as a component or components, one or more esters of acrylic acid or methacrylic acid having a linear or branched alkyl group having 30 or less carbon atoms, in particular, 4 to 18 carbon atoms in a range in which the acrylic resin can be thermally decomposed in the thermal bonding step. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an 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, an octadecyl group, and a dodecyl group.

Among the acrylic resins, those more preferably have a weight average molecular weight of 10,000 to 1,000,000, and still more preferably 30,000 to 700,000. When the weight average molecular weight is in the above range, adhesion before the thermal bonding step and thermal decomposition property during the thermal bonding step become excellent. The weight average molecular weight is a value that is measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

Among the acrylic resins, an acrylic resin thermally decomposed at 200° C. to 400° C. is preferred.

The first pre-sintering layer52may appropriately contain, other than the above-mentioned components, a plasticizer or the like, for example.

The first pre-sintering layer52can be manufactured by an ordinary method. For example, a varnish containing the respective components for forming the first pre-sintering layer52is produced. The varnish is applied onto a substrate separator to form a coating film so as to have a predetermined thickness, the coating film is then dried, and the first pre-sintering layer52is thereby manufactured.

A solvent that is used in the varnish is not particularly limited. However, an organic solvent or an alcoholic solvent is preferred which allows each of the above-described components to be dissolved, kneaded, or dispersed, uniformly. Examples of the organic solvent include ketone-based solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, acetone, methylethylketone, and cyclohexanone; toluene; and xylene. Examples of the alcoholic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 1,2,6-hexanetriol, glycerin, octanediol, 2-methyl-2,4-pentanediol, and terpineol.

The applying method is not particularly limited. Examples of methods for coating a solvent include a die coater, a gravure coater, a roll coater, a reverse coater, a comma coater, a pipe doctor coater, and screen printing. Among these, a die coater is preferred in terms of high uniformity in an application thickness. The drying condition of the coating film is not particularly limited. For example, drying can be performed at a drying temperature of 70° C. to 160° C. for a drying time of 1 minute to 5 minutes. Even after the coating film is dried, some solvents may remain in the coating film without the solvents being wholly evaporated.

When the first pre-sintering layer52contains the low-boiling binder, a part of the low-boiling binder may be volatilized depending on the drying condition. Therefore, the ratios of the respective components constituting the first pre-sintering layer52vary according to the drying condition. For example, even in the first pre-sintering layer52formed of the same varnish, the content of the metal fine particles in the entire first pre-sintering layer52and the content of the thermally decomposable binder are increased as a drying temperature is higher and a drying time is longer. Therefore, the drying condition is preferably set so that the metal fine particles and the thermally decomposable binder are contained in desired amounts in the first pre-sintering layer52.

Polyethylene terephthalate (PET), polyethylene, polypropylene, and a plastic film or a paper or the like whose surface is coated with a peeling agent such as a fluorine based peeling agent and a long chain alkylacrylate based peeling agent can be used as the substrate separator.

A method for mixing each of the above-described components with a mixer and press-molding the obtained mixture to manufacture the first pre-sintering layer52is also suitable as the method for manufacturing the first pre-sintering layer52. Examples of the mixer include a planetary mixer.

The first pre-sintering layer52is preferably sandwiched between two separators. That is, the first pre-sintering layer52is preferably sandwiched between two separators such that a separator52a, the first pre-sintering layer52, and a separator52bare stacked in this order (seeFIG. 4). As the separator52aand the separator52b, the same separator as the substrate separator can be used.

A second pre-sintering layer54can have the same configuration as that of the first pre-sintering layer52. The second pre-sintering layer54may have exactly the same configuration as that of the first pre-sintering layer52. The second pre-sintering layer54may have a configuration different from that of the first pre-sintering layer52in the range described in the section of the first pre-sintering layer52.

The first pre-sintering layer52and the second pre-sintering layer54have been described above.

Next, a semiconductor device manufacturing method according to the present embodiment will be described with reference to the drawings.

Each ofFIGS. 1 to 11is a schematic cross-sectional diagram for describing a semiconductor device manufacturing method according to the present embodiment.

A semiconductor device manufacturing method according to the present embodiment includes:

a step A of obtaining a laminated body in which a semiconductor element is temporarily adhered on a first electrode formed on a first insulating substrate, with a first pre-sintering layer sandwiched therebetween;

a step B of, after the step A, temporarily adhering the semiconductor element on a second electrode formed on a second insulating substrate, with a second pre-sintering layer sandwiched therebetween, the second pre-sintering layer being provided on a side opposite to the first pre-sintering layer, to obtain a semiconductor device precursor; and

a step C of simultaneously heating the first pre-sintering layer and the second pre-sintering layer after the step B, to bond the semiconductor element to the first electrode and the second electrode.

In the semiconductor device manufacturing method according to the present embodiment, first, a laminated body10shown inFIG. 1is obtained. The laminated body10has a configuration in which a semiconductor element42is temporarily adhered on a first electrode24formed on a first insulating substrate22with a first pre-sintering layer52sandwiched therebetween.

The laminated body10includes a support layer26provided on the back surface of the first insulating substrate22(the surface provided on a side opposite to the surface on which the first electrode24is formed). In order to prevent conduction between a plurality of first electrodes24, a cover layer28is provided on the outer peripheral portion of each of the first electrodes24. The cover layer28is provided on the first insulating substrate22on which the first electrode24is not provided. As in the present embodiment, the cover layer28may be formed so as to partially cover the first electrode24on the outer peripheral portion of the first electrode24.

Hereinafter, a specific method of obtaining the laminated body10will be described.

The laminated body10can be obtained by the following steps:

a step A-1 of preparing a lower substrate20including a first insulating substrate22and a first electrode24formed on the first insulating substrate22;

a step A-2 of preparing a semiconductor element42in which the first pre-sintering layer52is stacked on one surface and the second pre-sintering layer54is stacked on the other surface; and

a step A-3 of temporarily adhering the semiconductor element42prepared in the step A-2 on the first electrode24with the first pre-sintering layer52sandwiched therebetween.

In the step A-1, the lower substrate20is prepared.

As shown inFIG. 2, the lower substrate20includes the first insulating substrate22, the first electrode24formed on a part of the upper surface of the first insulating substrate22, a support layer26stacked on the back surface of the first insulating substrate22, and a cover layer28. As described above, the cover layer28is formed on the first insulating substrate22on which the first electrode24is not provided, and is formed so as to partially cover the first electrode24.

The material of the first insulating substrate22is not particularly limited as long as the first insulating substrate22has electrical insulation properties, and examples thereof include resins such as a polyester resin, an epoxy resin, a urethane resin, a polystyrene resin, a polyethylene resin, a polyamide resin, a polyimide resin, an ABS resin, a polycarbonate resin, and a silicone resin, and ceramics. Among these, from the viewpoint of heat resistance, the polyimide resin and the ceramics are preferable.

The use of the resins such as the polyimide resin allows the first insulating substrate22to have flexibility. The use of the ceramics allows the first insulating substrate22to be made solid so that the insulating substrate22cannot be bent.

Examples of the material of the first electrode24include various metals such as gold, silver, copper, nickel, and cobalt, or various alloys mainly containing these metals. In the present embodiment, the first electrode24is a two-layer electrode in which a gold electrode24aand a copper electrode24bare stacked. However, in the present invention, the first electrode is not limited to this example, and may be composed of one layer, or be composed of three or more layers.

The support layer26is a layer for imparting elasticity or rigidity to the lower substrate20when the first insulating substrate and the first electrode have flexibility. Examples of the support layer26include a plate having rigidity (for example, a copper plate, an SUS plate, an aluminum plate, a titanium plate, or the like), and an elastic sheet (a copper foil, an SUS foil, an aluminum foil, a polyimide film, a liquid crystal polymer film, a PET film, or the like).

The material of the cover layer28is not particularly limited as long as the cover layer28has electrical insulation properties, and examples thereof include resins such as a polyester resin, an epoxy resin, a urethane resin, a polystyrene resin, a polyethylene resin, a polyamide resin, a polyimide resin, an ABS resin, a polycarbonate resin, and a silicone resin, and an acrylic resin (solder resist). Among these, the polyimide resin is preferable from the viewpoint of heat resistance.

In the present embodiment, the case where the lower substrate20includes the first insulating substrate22, the first electrode24, the support layer26, and the cover layer28will be described. However, in the present invention, the lower substrate is not limited to this example as long as the lower substrate has the first insulating substrate and the first electrode. The support layer26may be omitted. The cover layer28may also be omitted.

In the step A-2, the semiconductor element42is prepared, in which the first pre-sintering layer52is stacked on one surface and the second pre-sintering layer54is stacked on the other surface.

The semiconductor element42in which the first pre-sintering layer52is stacked on one surface and the second pre-sintering layer54is stacked on the other surface can be obtained by the following steps X and Y:

the step X of forming the first pre-sintering layer on one surface of a semiconductor wafer and forming the second pre-sintering layer on the other surface of the semiconductor wafer, to obtain the semiconductor wafer including the pre-sintering layer formed on each surface; and

the step Y of making the semiconductor wafer obtained in the step X and including the pre-sintering layer formed on each of both the surfaces into individual pieces.

In the step X, as shown inFIG. 3, the first pre-sintering layer52is formed on one surface of a semiconductor wafer40, and the second pre-sintering layer54is formed on the other surface, to obtain a semiconductor wafer including the pre-sintering layer formed on each surface.

The step X may be a step in which the sheet-like first pre-sintering layer52is stacked on one surface of the semiconductor wafer40, and the sheet-like second pre-sintering layer54is stacked on the other surface, to obtain a semiconductor wafer including the pre-sintering layer formed on each surface. That is, the step X may be a step in which the first pre-sintering layer and the second pre-sintering layer are in the form of a sheet, and the sheet-like first pre-sintering layer52and the sheet-like second pre-sintering layer54are pasted on the semiconductor wafer40.

In this case, the sheet-like pre-sintering layer has a relatively uniform thickness. Therefore, in this case, the inclination of the semiconductor element can be further suppressed.

The sheet-like pre-sintering layer is usually prepared in a state where a separator is pasted on each of the surfaces of the sheet-like pre-sintering layer.FIG. 4shows a state in which the separator52aand the separator52bare pasted on both the surfaces of the sheet-like first pre-sintering layer52.FIG. 4also shows a state in which a separator54aand a separator54bare pasted on both the surfaces of the sheet-like second pre-sintering layer54.

When the sheet-like pre-sintering layer is pasted on the semiconductor wafer40, one of the separators is peeled off, and the sheet-like pre-sintering layer is then pasted.

More specifically, as shown inFIG. 5, first, the semiconductor wafer40is placed on the first pre-sintering layer52from which the separator52ahas been peeled off, and the second pre-sintering layer54from which the separator54ahas been peeled off is placed on the semiconductor wafer40. Then, pasting is performed under pressure. For example, as shown inFIG. 6, the first pre-sintering layer52and the second pre-sintering layer54can be pasted on both the surfaces of the semiconductor wafer40by a flat plate press in a state of being placed between a lower heating plate60and an upper heating plate62. It is preferable that a pasting pressure is in the range of 0.01 to 10 MPa. A pasting temperature during pasting is not particularly limited, and it is preferably in the range of 23 to 90° C., for example.

The pasting may be performed as follows. The first pre-sintering layer52from which one of the separators has been peeled off is placed on the lower heating plate60; the semiconductor wafer40is then placed on the first pre-sintering layer52; the second pre-sintering layer54from which one of the separators has been peeled off is then placed; and the first pre-sintering layer52and the second pre-sintering layer54are finally pasted on both the surfaces of the semiconductor wafer40under pressure by the lower heating plate60and the upper heating plate62.

In the step Y, as shown inFIG. 7, the semiconductor wafer40obtained in the step X and including the pre-sintering layer formed on each of both the surfaces is made into individual pieces.

Specifically, the separator52bis peeled off from the first pre-sintering layer52, and pasted on a dicing tape (not shown). Next, the separator54bis peeled off from the second pre-sintering layer54. The semiconductor wafer40is then diced into individual pieces.

As the dicing tape, a conventionally known dicing tape can be adopted, and therefore the description thereof will be omitted. As a dicing method, a conventionally known method can be adopted using a conventionally known dicing device, and therefore the description thereof will be omitted. Examples thereof include a method using a dicing blade, and a method of splitting after laser irradiation.

As described above, the semiconductor element42is obtained, in which the first pre-sintering layer52is stacked on one surface and the second pre-sintering layer54is stacked on the other surface.

In the above embodiment, the case where the separator52band the separator54bare peeled off before dicing has been described. However, the timing of peeling off the separator52band the separator54bis not limited to this example. For example, the separator52band the separator54bmay be peeled off after dicing. However, the case where the separator52band the separator54bare peeled off before dicing is excellent in that the separator52aand the separator52acan be collectively peeled off before the semiconductor element42is made into individual pieces. The case where the separator52band the separator54bare peeled off after dicing is excellent in that the pre-sintering layer can be protected just before temporary adhesion.

In the above example, the case where the sheet-like first pre-sintering layer and the sheet-like second pre-sintering layer are used has been described. However, the present invention is not limited to this example, and a liquid composition for forming the first pre-sintering layer and a liquid composition for forming the second pre-sintering layer may be used.

That is, the step X may be a step in which a liquid composition for forming a first pre-sintering layer is applied to one surface of the semiconductor wafer40to form the first pre-sintering layer52, and a liquid composition for forming a second pre-sintering layer is applied to the other surface to form the second pre-sintering layer54, thereby obtaining the semiconductor wafer including the pre-sintering layer formed on each of both the surfaces.

A liquid composition for forming a pre-sintering layer may be applied to one surface of the semiconductor wafer40, a sheet-like pre-sintering layer may be pasted on the other surface.

In the step A-3, the semiconductor element42prepared in the step A-2 is temporarily adhered on the first electrode24of the lower substrate20with the first pre-sintering layer52sandwiched therebetween (seeFIG. 1). In this step, a plurality of semiconductor elements42are temporarily adhered on each first electrode24using a chip mounter or the like. As a temporary adhesion condition, temporary adhesion is preferably performed under pressure of 0.01 MPa to 5 MPa. A temperature during temporary adhesion is not particularly limited, and it is preferably in the range of 23 to 150° C., for example. A pressure time is preferably 0.01 to 5 seconds.

The method of obtaining the laminated body10(step A) has been described above.

After the step A, the semiconductor element42is temporarily adhered on the second electrode34formed on a second insulating substrate32with the second pre-sintering layer54provided on the side opposite to the first pre-sintering layer52sandwiched therebetween, to obtain a semiconductor device precursor70(seeFIG. 9).

Hereinafter, a specific method of obtaining the semiconductor device precursor70will be described.

The semiconductor device precursor70can be obtained by the following steps:

a step B-1 of preparing an upper substrate30including the second insulating substrate32and a second electrode34formed on the second insulating substrate32; and

a step B-2 of temporarily adhering the semiconductor element42of the laminated body10obtained in the step A and the second electrode34of the upper substrate30with the second pre-sintering layer54sandwiched therebetween.

In the step B-1, the upper substrate30is prepared.

As shown inFIG. 8, the upper substrate30includes the second insulating substrate32, the second electrode34formed on a part of the upper surface of the second insulating substrate32, a support layer36stacked on the back surface of the second insulating substrate32, and a cover layer38. The cover layer38is formed on the second insulating substrate32on which the second electrode34is not provided, and is formed so as to partially cover the second electrode34.

The second electrode34of the upper substrate30and the first electrode24of the lower substrate20are disposed so as to have an opposed positional relationship when a semiconductor device80(seeFIG. 11) is manufactured, and disposed so that a plurality of semiconductor elements42are electrically connected in series when the plurality of semiconductor elements42are sandwiched therebetween.

As the material of the second insulating substrate32, the same material as that of the first insulating substrate22can be used.

As the material of the second electrode34, the same material as that of the second electrode34can be used.

As the support layer36, the same configuration as that of the support layer26can be adopted.

As the cover layer38, the same configuration as that of the cover layer28can be adopted.

In the step B-2, as shown inFIG. 9, the semiconductor element42of the laminated body10obtained in the step A and the second electrode34of the upper substrate30are temporarily bonded with the second pre-sintering layer54sandwiched therebetween.

In this step, the upper substrate30is placed on the laminated body10, and then temporarily adhered on the laminated body10by heating using an upper heating plate64. A temperature during temporary adhesion is not particularly limited, and it is preferably in the range of 23 to 150° C., for example. A heating time is preferably 1 to 100 seconds. Pressure may be performed, and temporary adhesion is preferably performed under pressure of 0.01 MPa to 5 MPa, for example.

The method of obtaining the semiconductor device precursor70(step B) has been described above.

After the step B, the first pre-sintering layer52and the second pre-sintering layer54are simultaneously heated, to bond the semiconductor element54to the first electrode24and the second electrode34.

In this bonding step C (thermal bonding step), the metal fine particles in the first pre-sintering layer52and the second pre-sintering layer54are sintered by heating, and the thermally decomposable binder is thermally decomposed as necessary. The residual low-boiling binder which has not been sufficiently volatilized in the drying step is volatilized. A heating temperature is preferably 180 to 400° C., more preferably 190 to 370° C., and still more preferably 200 to 350° C. A heating time is preferably 0.3 to 300 minutes, more preferably 0.5 to 240 minutes, and still more preferably 1 to 180 minutes. Thermal bonding may be performed under a pressurized condition. The pressurized condition is preferably in the range of 1 to 500 kg/cm2, and more preferably in the range of 5 to 400 kg/cm2. Thermal bonding under pressure can be executed by a device which can simultaneously perform heating and pressurizing, such as a flip chip bonder, for example. As shown inFIG. 10, a parallel plate press including a lower heating plate66and an upper heating plate68may also be used. Thus, the semiconductor device80(seeFIG. 11) is obtained.

The semiconductor device manufacturing method according to the present embodiment has been described above.

The semiconductor element42is preferably a thermoelectric element. When the semiconductor element42is the thermoelectric element, a thermoelectric conversion module can be provided, in which the positional deviation or inclination of the thermoelectric element is suppressed.

When the semiconductor element42is the thermoelectric element, each of the plurality of semiconductor elements42is a P-type thermoelectric element or an N-type thermoelectric element, and these are alternately and electrically connected in series.

EXAMPLES

Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the examples below as long as the present invention does not exceed the gist thereof.

Components used in examples will be described.

Metal fine particles-containing paste A: obtained by appropriately adjusting the amount of a low-boiling binder contained in ANP-1 (paste in which nano-sized fine silver particles are dispersed in the low-boiling binder) manufactured by Applied Nanoparticle Laboratory Corporation

According to the ratio of blending of compounds described in Table 1, each component and solvent described in Table 1 were placed in a stirring pot of a hybrid mixer (HM-500 manufactured by KEYENCE CORPORATION), and were stirred and mixed in a stirring mode for 3 minutes.

The obtained varnish was applied onto a released-treated film (MRA50 manufactured by Mitsubishi Plastics, Inc.), followed by drying. The drying conditions were as shown in Table 1.

[Production and Evaluation of Semiconductor Device]

As a lower substrate, a flexible printed circuit board (FPC) was prepared. In this flexible printed circuit board, a first electrode having a three-layer configuration of gold/(electroless) nickel/copper was formed on a first insulating substrate composed of a polyimide film. One first electrode had a length of 3 mm and a width of 7 mm, and two chips each having a length of 2 mm and a width of 2 mm were mounted with a distance of 1 mm at the center on the first electrode. The first electrodes (10 in the length direction×6 in the width direction) were arrayed with a distance of 1 mm on the first insulating substrate.

The same substrate as the lower substrate was prepared as an upper substrate.

On the other hand, a semiconductor wafer having a thickness of 2 μm was prepared, and a pre-sintering layer of examples was pasted on each surface of the semiconductor wafer. The pasting conditions of 80° C., 0.5 MPa, and 10 seconds were set with a parallel plate press. The same pre-sintering layers were pasted on both the surfaces.

Next, the semiconductor wafer including the pre-sintering layer pasted on each of both the surfaces was pasted on a dicing tape (NBD-5172K manufactured by Nitto Denko Corporation).

Next, dicing was performed using a dicing device (manufactured by Disco Corporation, device name: DFD-6361). As a result, the semiconductor wafer and the pre-sintering layer pasted on each of both the surfaces were made into individual pieces. The dicing conditions were as follows: dicing ring: 2-8-1 (manufactured by Disco Corporation), dicing rate: 30 mm/sec, dicing blade: B1A8015DC320N50M51 (manufactured by Disco Corporation), dicing blade rotation number: 30000 rpm, blade height: 50 μm from chuck table surface, cut method: A mode/single cut, wafer chip size: 2 mm square.

Next, the individual piece of the semiconductor wafer (hereinafter also referred to as a chip) was temporarily adhered on the electrode of the lower substrate. Temporary adhesion conditions of 80° C., 0.5 MPa, and 0.5 seconds were set with a chip mounter.

Next, the upper substrate was placed on the chip, and then temporarily adhered on the chip. The temporary adhesion conditions of 80° C., 0.5 MPa, and 10 seconds were set with a parallel plate press.

Next, heating was performed under the conditions of 300° C., 90 seconds, and 1 MPa in the parallel plate press. This caused the chip and the electrode to be bonded to each other.

For the samples produced as described above, the sample in which the chip and the electrode were bonded to each other was evaluated as “◯”, and the sample in which the chip and the electrode were not bonded to each other was evaluated as “x”. The results are shown in Table 1.

[Measurement of Temporary Adhesion Shear Strength]

The pre-sintering layer produced in examples was pasted on a test chip (semiconductor chip, length: 2 mm×width: 2 mm, thickness: 3 mm) under the conditions of 0.5 MPa, 10 seconds, and 80° C. by a parallel plate press. Next, the shear strength (shear strength assumed during temporary adhesion) at room temperature (24° C.) was measured.

Specifically, the shear strength was measured under the following conditions using Bond Tester 5000 Series for ultra-fine pitch bonding, manufactured by Nordson Advanced Technology Japan K. K. (former name: Dage Japan Co., Ltd.). The results are shown in Table 1.

In this measurement, the test chip was broken before being peeled off. Therefore, Table describes values at break. Therefore, the actual share strength is higher than the values. Table also shows a portion of a broken interface.

Test type: Destructive test

[Measurement of Shear Strength after being Sintered]

The pre-sintering layer produced in examples was pasted on a test chip (semiconductor chip, length: 2 mm×width: 2 mm, thickness: 3 mm) under the conditions of 0.5 MPa, 10 seconds, and 80° C. by a parallel plate press. Next, heating was performed in a parallel plate press under the conditions of 1 MPa, 90 seconds, and 300° C. This provided a sintered layer from the pre-sintering layer. Then, the shear strength (shear strength assumed after thermal bonding) at room temperature (24° C.) was measured.

Specifically, the shear strength was measured under the following conditions using Multipurpose Bond Tester 4000 series manufactured by Nordson Advanced Technology Japan K. K. (former name: Dage Japan Co., Ltd.).

In this measurement, the test chip was broken before being peeled off. Therefore, Table describes values at break. Therefore, the actual share strength is higher than the values. Table also shows a portion of a broken interface.

Test type: Destructive test

A semiconductor chip (bismuth-tellurium alloy (BiTe) chip) was prepared, which included a Ni layer (thickness: 2 to 5 μm (average: about 3.5 μm)) and an Au layer (thickness: 50 nm) formed in this order on a back surface. The semiconductor chip had a thickness of 500 μm, a length of 5 mm, and a width of 5 mm. The pre-sintering layer of examples was pasted on the Au layer surface of the prepared semiconductor chip.

The pasting conditions of 0.5 MPa, 10 seconds, and 80° C. were set with a parallel plate press.

A copper plate (copper plate thickness: 3 mm) entirely covered with an Ag layer (thickness: 5 μm) was prepared. On the prepared copper plate, a pre-sintering layer with a semiconductor chip was bonded under the following conditions. Thus, a sample for evaluation was obtained. For the bonding, a sintering device (HTM-3000 manufactured by Hakuto Co., Ltd.) was used.

The pre-sintering layer was heated from 80° C. to 300° C. at a heating rate of 1.5° C./sec under pressure of 10 MPa (flat plate press), and then held at 300° C. for 2.5 minutes. Then, the pre-sintering layer was air-cooled to 170° C., and then water-cooled to 80° C. The water-cooling is provided by a water-cooling type cooling plate provided in a pressurizing plate.

Then, the sample was embedded in an epoxy resin (cured resin manufactured by SCANDIA (2-pack type, SCANDIPLEX A, SCANDIPLEX B)).

left at 45° C. for 1 to 2 hours

After embedding, the diagonal cross-section of the semiconductor chip was exposed by a mechanical polishing method. In the mechanical polishing, rough polishing was performed, and precise polishing was then performed. As a polishing device for rough polishing, RotoPol-31 manufactured by Struers was used. As a polishing device for precise polishing, a precise polishing device MultiPrep manufactured by ALLIED was used. The rough polishing conditions and the precise polishing conditions were as follows.

Then, the vicinity of the center of the exposed surface was ion-polished. As the device, a cross section polisher SM-09010 manufactured by JEOL Ltd. was used, and the conditions of ion polishing were as follows.

Amount of protrusion from shielding plate: 25 to 50 μm

Pushing was performed under the following pushing conditions using a nanoindenter (Triboindeter manufactured by Hysitron, Inc.) for the total of three points, that is, the center of the cross section of the exposed sintered layer and the positions separated by 20 μm in left and right from the center. As a result, a load-displacement curve was obtained. A projected image of an indenter (image of traces provided by pushing the indenter) was obtained.

Measuring method: Single pushing measurement mode

From the load-displacement curve and the projected area of the indenter, values of hardness, modulus of elasticity, and deformation amount were obtained by calculation. The hardness and the modulus of elasticity were calculated in detail with the device. Specifically, detailed calculation methods are described in, for example, Handbook of Micro/nano Tribology (Second Edition) Edited by Bharat Bhushan, CRC Press (ISBN 0-8493-8402-8), and therefore the description thereof will be omitted. The results are shown in Table 1.

Here, the load-displacement curve will be described.FIG. 12is a diagram showing an example of the load-displacement curve. A horizontal axis indicates a displacement amount (pushing amount), and a vertical axis indicates a load. Since, during pushing, the load is applied together with pushing, plotting is made from the position of a displacement amount of 0 and a load of 0 to the upper right. Then, when the displacement amount reaches 2 μm and the pushing is released, the deformed bonded layer is partially restored. At this time, the displacement when the load reaches 0 is read, and taken as a deformation amount.

Next, the projection image of the indenter will be described.FIG. 13is a diagram for describing the projection image of the indenter. InFIG. 13, a lower layer is a copper plate, a middle layer is a sintered layer, and an upper layer is a semiconductor chip. A black triangle on the sintered layer is a trace (projected image) after pushing the indenter. The projected area of the indenter is obtained from the area of this image.FIG. 13is a diagram for describing a projected image of an indenter using a nanoindenter, which does not belong to examples or comparative examples.

DESCRIPTION OF REFERENCE SIGNS