JP6965531B2 - Die bond sheet and semiconductor device - Google Patents

Description

The present invention relates to a die bond sheet and a semiconductor device. More specifically, a semiconductor element such as a power semiconductor, an LSI, or a light emitting diode (LED) is mounted on a semiconductor such as a lead frame, a ceramic wiring board, a glass epoxy wiring board, or a polyimide wiring board. The present invention relates to a die bond sheet suitable for joining to a substrate for use, and a method for manufacturing a semiconductor device obtained by using the die bond sheet.

When manufacturing a semiconductor device, as a method of adhering a semiconductor element and a lead frame (support member), a paste-like adhesive in which a filler such as silver powder is dispersed in a resin such as an epoxy resin or a polyimide resin ( For example, there is a method of using silver paste). In this method, a paste-like adhesive is applied to a die pad of a lead frame using a dispenser, a printing machine, a stamping machine, or the like, and then a semiconductor element is die-bonded and bonded by heat curing to form a semiconductor device.

In recent years, as semiconductor elements have become faster and more integrated, adhesives are also required to have high heat dissipation characteristics in order to ensure the operational stability of semiconductor devices.

Adhesives for the purpose of improving thermal conductivity have been proposed so far. For example, Patent Documents 1 to 5 below include die bonding pastes (Patent Documents 1 and 2) highly filled with silver particles having high thermal conductivity, and conductive adhesives containing spherical silver powder having a specific particle size (Patent Documents 1 and 2). Patent Document 3), paste of adhesive containing solder particles (Patent Document 4), conductive adhesive containing metal powder having a specific particle size and ultrafine metal particles having a specific particle size (Patent Document 5). ) Is disclosed.

Further, in Patent Document 6 below, silver particles are burned by heating a paste-like silver particle composition composed of surface-treated non-spherical silver particles and a volatile dispersion medium at 100 ° C. or higher and 400 ° C. or lower. A technique has been proposed in which they are combined to form solid silver having a predetermined thermal conductivity.

Japanese Unexamined Patent Publication No. 2006-73811 Japanese Unexamined Patent Publication No. 2006-302834 Japanese Unexamined Patent Publication No. 11-66953 Japanese Unexamined Patent Publication No. 2005-93996 Japanese Unexamined Patent Publication No. 2006-833777 Japanese Patent No. 4353380

It is considered that the paste-like silver particle composition described in Patent Document 6 is superior in thermal conductivity and connection reliability at high temperature as compared with other methods because silver forms a metal bond. However, such a paste-like silver particle composition requires three steps of coating, pre-drying and heat sintering. Further, since it contains a solvent, there are problems such as spots due to flow during coating, drying, mounting of a semiconductor element, and sintering, and voids during drying and sintering. Patent Document 6 has problems of productivity and device damage because pressurization is required at the time of joining in order to join the interface and improve the physical properties of the silver joint.

On the other hand, when solder is used, die bonding is performed by interposing a sheet-shaped solder between the substrate and the semiconductor element and heating and melting the solder. In this method, the process can be simplified and the generation of spots and voids due to the solvent can be suppressed as compared with the paste. However, solder poses a problem in connection reliability at high temperatures. Even if a metal having a high melting point is used instead of solder, there is a problem that joining becomes difficult.

The present invention provides a die bond sheet having excellent thermal conductivity and connection reliability and capable of joining a semiconductor element and a support member for mounting a semiconductor element in a simple process, and a semiconductor device obtained by using the die bond sheet. The purpose is.

The present invention provides a die bond sheet containing 75% by mass or more of copper particles and 5% by mass or more of a pyrolytic resin.

In the present invention, the pyrolytic resin is preferably at least one selected from the group consisting of polycarbonate, polymethacrylic acid, polymethacrylic acid ester and polyester.

In the present invention, the copper particles are sub-micro copper particles having a volume average particle diameter of 0.12 μm or more and 0.8 μm or less, and flake-shaped micro copper particles having a maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of 4 or more. The content of the flake-shaped micro copper particles is preferably 50% by mass or less based on the total mass of the copper particles.

The present invention is preferably formed by molding and heating a paste-like composition containing copper particles, a pyrolytic resin, and a dispersion medium.

The present invention also provides a semiconductor device in which a semiconductor element and a support member for mounting the semiconductor element are joined via the above-mentioned sintered body of the die bond sheet.

According to the present invention, a die bond sheet having excellent thermal conductivity and connection reliability and capable of joining a semiconductor element and a support member for mounting a semiconductor element in a simple process, and a semiconductor device obtained by using the die bond sheet. Can be provided. The semiconductor device can have excellent thermal conductivity and connection reliability by having a structure in which a semiconductor element and a support member for mounting the semiconductor element are joined by the die bond sheet of the present invention.

It is a schematic cross-sectional view which shows the manufacturing method of a semiconductor device. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment.

<Die bond sheet>
The die bond sheet of the present embodiment requires at least copper particles and a thermally decomposable resin. The copper particles are sintered by firing, and the adherend and the sintered copper particles are bonded to each other by a metal bond to exhibit a function of joining. The pyrolytic resin serves to connect the copper particles and mold them into a sheet. Further, by selecting a thermoplastic material as the pyrolytic resin, the function of temporarily fixing the adherends to each other is exhibited by thermocompression bonding. Further, by selecting one that thermally decomposes at a temperature lower than the sintering temperature, it is possible to form a good bonding layer of sintered copper by sintering copper particles without hindering sintering.

<Copper particles>
The copper particles (sinterable copper particles) preferably contain copper as a main component from the viewpoint of thermal conductivity, sinterability, and connection reliability. Among the elements contained in the copper particles, the element ratio of copper in the element ratio excluding hydrogen, carbon, and oxygen is preferably 60 atomic% or more, more preferably 70 atomic% or more, and more preferably 80 atomic%. The above is more preferable. If the copper content is lower than this, the produced copper sintered body bonding layer becomes an alloy having properties different from those of copper, and the thermal conductivity and connection reliability are lowered.

In order to lower the sintering temperature (for example, 300 ° C. or lower), the copper particles are made of sub-micro copper particles (micro-particle size copper particles) having a volume average particle size of 0.12 μm or more and 0.8 μm or less. It is preferable to contain at least 50% by mass or more based on the total mass. Sub-micro copper particles of this size start sintering at about 250 ° C. and can be bonded at a low temperature. When the volume average particle size is 0.12 μm or more, the effects of suppressing the synthesis cost of the sub-micro copper particles, good dispersibility, and suppressing the amount of the surface treatment agent used can be easily obtained. When the volume average particle size is 0.8 μm or less, the effect of excellent sinterability of the submicro copper particles can be easily obtained. From the viewpoint of further exerting the above effect, the volume average particle size of the sub-micro copper particles may be 0.15 μm or more and 0.8 μm or less, 0.15 μm or more and 0.6 μm or less, and may be 0. It may be .2 μm or more and 0.5 μm or less, and may be 0.3 μm or more and 0.45 μm or less. In the specification of the present application, the volume average particle diameter means a 50% volume average particle diameter.

In the above-mentioned sintering of the sub-micro copper particles alone, the volume shrinkage is large, and cracks on the sintered body, peeling from the adherend surface, and a decrease in the density of the sintered body are likely to occur. Therefore, it is preferable that the sub-micro copper particles and the micro copper particles having a maximum diameter of 1 μm or more and 20 μm or less are contained together. When micro-copper particles are contained, the effect of reducing the volume shrinkage during sintering and improving the strength of the bonded layer after sintering can be obtained. From the viewpoint of further exerting the above effect, the maximum diameter of the micro copper particles may be 1 μm or more and 10 μm or less, or 3 μm or more and 10 μm or less.

The content of the micro copper particles in the copper particles is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more. The upper limit of the content is preferably 50% by mass or less. If the content of the micro copper particles is too large, the sinterability at 300 ° C. or lower tends to decrease, and the bonding strength tends to decrease.

Examples of the shape of the micro copper particles include a spherical shape, a substantially spherical shape, a polyhedral shape, a needle shape, and a flake shape. In particular, when needle-shaped or flake-shaped copper particles having a large aspect ratio are used, the reinforcing effect and the density improving effect due to the orientation of the micro copper particles can be obtained, which is preferable.

When the micro-copper particles are flake-shaped (flake-shaped micro-copper particles), the aspect ratio may be 4 or more, or 6 or more. When the aspect ratio is within the above range, the flake-shaped microcopper particles in the bonding copper paste are oriented substantially parallel to the bonding surface, so that the volume shrinkage when the bonding copper paste is sintered is reduced. Easy to suppress. As used herein, the "aspect ratio" refers to the long side / thickness of the particles. The measurement of the long side and the thickness of the particle can be obtained from, for example, an SEM image of the particle.

In the present specification, the sub-micro copper particles mean particles having a particle diameter of 0.1 μm or more and less than 1.0 μm, and the micro copper particles mean particles having a particle diameter of 1.0 μm or more and less than 20 μm. do.

<Pyrolytic resin>
The thermally decomposable resin preferably has a molecular weight of 1000 or more, and more preferably 10,000 or more, for the purpose of connecting the sintered copper particles and molding the resin into a sheet. Below this, the toughness of the pyrolytic resin becomes poor, the amount of resin required for molding into a sheet increases, and the bonding characteristics deteriorate.

As the pyrolytic resin, a thermoplastic one is preferable. That is, it is preferably a linear or branched polymer rather than a crosslinked polymer. From the viewpoint of enabling temporary crimping, a polymer having a softening point (glass transition point) lower than the temporary crimping temperature is preferable. Since the temporary crimping temperature is lower than about 200 ° C., the softening point (glass transition point) is preferably 200 ° C. or lower, more preferably 170 ° C. or lower, and even more preferably 150 ° C. or lower.

The thermally decomposable resin is preferably thermally decomposed at a temperature lower than the sintering temperature. In particular, it is preferable that the resin is gasified without leaving any residue during thermal decomposition in an oxygen-free atmosphere. Residues such as oligomers and carbides after thermal decomposition are not preferable because they inhibit sintering. The amount of the residue after thermal decomposition of the pyrolyzable resin is better because it hinders the sintering of copper particles, and is usually preferably 5% by mass or less, more preferably 2% by mass or less, based on the mass of the resin before thermal decomposition. The amount of residue after pyrolysis of the pyrolyzable resin is the weight after holding for the sintering time at the sintering temperature by the TG / DTA of the pyrolysis resin in 3 to 5% by mass hydrogen-containing inert gas (nitrogen or argon). It can be measured as the amount of change. It should be noted that the TG / DTA measurement in air is not preferable because the amount of residue in the reducing atmosphere is smaller than that in the reducing atmosphere because oxidative decomposition proceeds.

The thermally decomposable resin is preferably a polymer having a thermally depolymerizable bonding group in the main chain. Examples of such a polymer having the above desired properties include polycarbonate, polymethacrylic acid, polymethacrylic acid ester, polyester, polyacrylic acid, and polyacrylic acid ester.

<Other metal particles>
The die bond sheet may contain gold particles, silver particles, palladium particles, zinc particles, nickel particles and the like as other metal particles. By containing a small amount of these metal particles, the sintering temperature of the metallic copper particles is lowered, and bonding becomes easy.

The carbon content in the copper sintered body (bonding layer) generated from the die-bonded sheet after firing is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and 0.2% by mass or less. Is even more preferable. If a larger amount of carbon is contained, sintering is hindered and the bonding strength and connection reliability are lowered.

The die bond sheet of the present embodiment contains copper particles and a thermally decomposable resin, and preferably has a carbon content of 2.0% by mass or more and 10.0% by mass or less. The carbon content can be measured by the measuring method used in the "carbon quantification method in metal", for example, the induction heating combustion infrared absorption method.

<Composition ratio of die bond sheet>
The content of the copper particles is preferably 70% by mass or more and 95% by mass or less, and more preferably 75% by mass or more and 94% by mass or less, based on the total mass of the die bond sheet. When the proportion of copper particles is smaller than this, the volume shrinkage due to the decomposition of the thermally decomposable resin becomes large, cracks, peeling, macrovoids occur, bonding defects occur due to a decrease in sintered body density, and connection reliability. It causes a decrease in. On the other hand, if the amount is more than this, the proportion of the thermally decomposable resin decreases, resulting in a decrease in moldability and a decrease in temporary fixing property.

The content of the thermally decomposable resin is preferably 5% by mass or more and 25% by mass or less, and preferably 6% by mass or more and 20% by mass or less, based on the total mass of the die bond sheet. In this case, the temporary fixing property and the adhesive strength can be improved.

When other metal particles are contained, the content thereof is preferably 0.05% by mass or more and 10% by mass or less, and 0.1% by mass or more and 5% by mass or less, based on the total mass of the die bond sheet. Is preferable. This lowers the sintering temperature and facilitates joining.

<Manufacturing method of die bond sheet>
Next, a method for manufacturing the die bond sheet of the present embodiment will be described. In order to obtain a die bond sheet, there are a method of forming a paste-like composition in which raw materials are dispersed or dissolved into a sheet by coating, and a method of mixing powders of raw materials and forming into a sheet by a hot roll or a press. ..

The paste-like composition used for coating is preferably used in the form of a paste by dispersing or dissolving particles or resins as raw materials in a solvent. As the solvent used in this paste-like composition, it is preferable that the copper particles have high dispersibility, the pyrolytic resin can be dissolved at a high concentration, and the solvent is volatilized in the drying step.

The dispersion medium capable of dispersing the copper particles and dissolving the pyrolytic resin depends on the type of the surface treatment agent for the copper particles, the type of the dispersant added to the copper paste for bonding, the type of the pyrolytic resin, and the like. For example, when a highly polar dispersant or a highly polar pyrolytic resin is selected, a highly polar solvent is suitable, and when a low polar dispersant or a low polar pyrolytic resin is selected, it is low. Polar solvents are preferred.
It is inferred that it is preferable to select a combination of such dispersants, pyrolytic resins, and solvents having similar Hansen solubility parameters. The Hansen solubility parameter can be searched, for example, from the database at the end of the following publications, or searched / calculated by the database and simulation integrated software HSPiP.
Published literature: "HANSEN SOLUBILITY PARAMETERS: A USER'S HANDBOOK" (CRC Press, 1999)

In order to form a paste-like composition in which the dispersibility of the copper particles is good and the pyrolytic resin is dissolved at a high concentration, the embodiment shown in Table 1 is preferable. If these aspects are not adopted, poor dispersibility of copper particles and poor dissolution of the thermally decomposable resin tend to cause a decrease in viscosity, a decrease in concentration, and a decrease in paste properties such as generation of coarse particles. Further, the obtained sheet tends to be brittle, the composition in the sheet becomes non-uniform, and the sheet properties deteriorate, the die bond layer becomes non-uniform, and the bonding strength tends to decrease.

Examples of highly polar solvents include carbonic acid esters such as 1,3-dioxolan-2-one and 4-methyl-1,3-dioxolan-2-one, lower alcohols such as methanol and ethanol, glycerin and diglycerin. , Polyhydric alcohols such as diethylene glycol and propylene glycol, amines, acid amides such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, esters such as γ-butyrolactone, water. Can be mentioned.

Examples of low polar solvents include higher alcohols such as pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, butylene glycol, α-terpineol, and bornylcyclohexanol (MTPH), and ethylene glycol butyl ether and ethylene glycol phenyl ether. , Diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol isopropylmethyl 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, tripropylene Ethers such as glycol dimethyl ether, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, esters such as propylene carbonate, etc. Examples thereof include aliphatic hydrocarbons such as cyclohexanone, octane, nonane, decane and undecane, and aromatic hydrocarbons such as benzene, toluene and xylene.

The blending amount of the solvent is preferably 10 to 40 parts by mass with respect to 100 parts by mass of the metal particles (the total amount of the copper particles and other metal particles, if included).

From the viewpoint of coating and moldability, the paste-like composition preferably has a Casson viscosity at 25 ° C. of 0.01 Pa · s or more and 10 Pa · s or less, and preferably 0.05 Pa · s or more and 5 Pa · s or less. More preferred.

The method for molding the composition into a sheet may be any method as long as the paste-like composition is formed into a sheet, and such methods include inkjet printing, screen printing, jet printing, dispenser, and jet dispenser. , Kamma coater, slit coater, die coater, gravure coater, slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, bar coat, applicator, spray coater, electrodeposition coating and the like can be used.

The paste-like composition may be formed in the form of a sheet directly on the adherend surface of the adherend to be bonded. Further, it may be used after being formed into a sheet on a temporary molded substrate and then peeled off.

A smooth molded substrate is preferable. From the viewpoint of the smoothness of the molded die-bonded sheet, the smoothness of the molded substrate is preferably a plate-like or sheet-like substrate having a flat surface having a ten-point average surface roughness of 20 μm or less. Further, since it is necessary to release the die bond sheet formed through the drying step from the substrate, it is preferable that the surface material of the molded substrate does not have adhesiveness to the die bond sheet. Further, it is preferable that the material has heat resistance that does not deform at the drying temperature.

As the material of such a molded substrate, polyethylene terephthalate, polytetrafluoroethylene, polyimide, PEEK, aluminum, glass, alumina, silicon nitride, and stainless steel can be used. Further, a heat-resistant substrate or cloth coated or impregnated with the above material may be used as a molded substrate.

The paste-like composition formed into a sheet can be separated as a self-supporting sheet by drying the solvent so that the pyrolytic resin becomes a binder of copper particles and solidifies.

As the above-mentioned drying method, drying by leaving at room temperature, heat drying or vacuum drying can be used. For heat drying or vacuum drying, hot plate, warm air dryer, hot air heating furnace, nitrogen dryer, infrared dryer, infrared heating furnace, far infrared heating furnace, microwave heating device, laser heating device, electromagnetic heating device , A heater heating device, a steam heating furnace, a hot plate pressing device, or the like can be used. The drying temperature and time are preferably adjusted appropriately according to the type and amount of the dispersion medium used, and for example, drying at 50 to 180 ° C. for 1 to 120 minutes is preferable.

From the viewpoint of suppressing the oxidation of copper particles, the copper particles may be dried in a non-oxidizing atmosphere. Substitution and spraying with non-oxidizing gases such as argon, nitrogen and water vapor can be mentioned.

The obtained die bond sheet is used in the die bond process. When the releasability is poor, the blade-shaped plate can be inserted between the obtained die bond sheet and the molded substrate to separate them.

The die bond sheet can be cut to the size required in the die bond process. The cutting may be performed before the mold is released from the molded substrate, or may be performed after the mold is released.

The thickness of the die bond sheet can be appropriately set according to the surface roughness of the semiconductor element as an adherend and the support member for mounting the semiconductor element and the connection reliability after joining. It is preferably 5 μm or more, and more preferably 10 μm or more.

<Manufacturing method of semiconductor devices>
In the semiconductor device, the die bond sheet of the present embodiment is sandwiched between the semiconductor element and the support member for mounting the semiconductor element, or the other adherend member is superposed on the die bond sheet formed on the adherend surface of the adherend. It is obtained by joining the semiconductor element and the support member for mounting the semiconductor element by heat-bonding, temporarily fixing, and then heat-burning (in some cases, without pressurization).

FIG. 1 is a schematic view showing a method of manufacturing a semiconductor device. In FIG. 1A, the die bond sheet 1a is formed as a self-supporting sheet, and is sandwiched between the semiconductor element 2 and the semiconductor element mounting support member 3 for joining. In FIG. 1B, the die bond sheet 1b is formed in contact with the semiconductor element mounting support member 3 in a sheet shape, and the semiconductor element 2 is placed on the die bond sheet 1b and subjected to bonding. The die bond sheet 1b is attached to the semiconductor element mounting support member 3 due to the adhesiveness of the contained pyrolytic resin even before the joining treatment. In FIG. 1C, the die bond sheet 1c is formed in a sheet shape in contact with the semiconductor element 2, and the semiconductor element 2 is placed in contact with the semiconductor element mounting support member 3 so that the die bond sheet 1c is in contact with the semiconductor element mounting support member 3. It is placed on 3 and used for joining. The die bond sheet 1c adheres to the semiconductor element 2 even before the bonding treatment due to the adhesiveness of the contained pyrolytic resin.

Temporary fastening by thermocompression bonding softens the pyrolytic resin contained in the die bond sheet and applies pressure to generate adhesion of the pyrolytic resin, thereby joining the semiconductor element and the support member for mounting the semiconductor element. Means to do. For this reason, unlike the formation of metal joints that use silver or copper sheet-like porous materials, processing can be performed at low temperatures in a short time, so chip mounting devices such as chip mounters and flip chip bonders can be used. This can be easily performed using a thermocompression bonding device or the like.

By temporarily fixing the semiconductor element and the support member for mounting the semiconductor element with a die bond sheet, the process up to the next sintering step can be easily handled, and the joint position accuracy between the semiconductor element and the support member for mounting the semiconductor element can be improved. Further, by using a sheet-shaped die bond sheet having a fixed thickness, it becomes easy to control the thickness of the die bond layer after firing.

The lower limit of the temperature for temporary fixing is the temperature at which the pyrolytic resin softens, and varies depending on the type, molecular weight, and degree of branching of the pyrolytic resin, but is usually 60 ° C. or higher. The upper limit of the temperature for temporary fixing is the thermal decomposition start temperature of the thermally decomposable resin, which varies depending on the type of the thermally decomposable resin, but is usually 200 ° C. or higher and 300 ° C. or lower. However, these temperatures are the temperatures of the die bond sheet, and the temperature of the heating device may be set to this temperature or higher for the purpose of raising the temperature in a short time.

The crimping pressure in the temporary fixing step is the pressure required for the die bond sheet to deform and adhere to the adherend in the softened state of the pyrolyzable resin, and depends on the melt viscosity of the die bond sheet, but is usually 0.01 MPa. As mentioned above, 0.1 MPa or more is preferable. The upper limit of the crimping pressure is limited by the amount of creeping up to the tip end due to the deformation of the die bond sheet, and is usually 10 MPa or less.

The semiconductor element temporarily fixed by the die bond sheet and the support member for mounting the semiconductor element are then desorbed from the thermally decomposable resin and sintered with copper particles in the heating process, and the semiconductor element and the support member for mounting the semiconductor element are separated from each other. Firmly join with a copper sintered body.

During the period from the temporary fixing step to the heating step, the temporarily fixed semiconductor element and the semiconductor element mounting support member may be cooled to room temperature. Since it is temporarily fixed with a pyrolytic resin, it is possible to suppress the displacement of the semiconductor element during handling during this period, and the handling becomes easy. Furthermore, unlike the paste-like composition, it does not substantially contain a volatile organic solvent, so that there is no restriction on the pot life in the temporarily fixed state, and no exhaust equipment for the organic solvent is required. There is.

The heating step requires a temperature sufficient for the decomposition / desorption of the pyrolytic resin and the sintering of the copper particles to proceed, and is usually preferably 180 ° C. or higher, more preferably 200 ° C. or higher. The upper limit of the temperature is determined by the heat resistance of the semiconductor element and the degree of residual thermal stress after firing, and is usually preferably 350 ° C. or lower. Further, from the viewpoint of removing oxides of copper particles and preventing oxidation, heating is preferably performed in a reducing atmosphere. Examples of the reducing atmosphere include reducing gases such as hydrogen, ammonia gas, and formic acid, and mixed gases of these reducing gases and inert gases such as nitrogen, argon, and steam.

In the heating step, firing without pressurization is possible, and in this case, a large amount of semiconductor devices can be processed in a batch without the need for a special thermocompression bonding device, so that the cost is advantageous. However, the die bond sheet may be pressurized for the purpose of improving the yield and the density of the sintered body. The pressurizing pressure can be 0.01 MPa to 10 MPa. At a low pressure of about 0.01 MPa to 0.1 MPa, it is expected that the yield will be improved by suppressing joint defects such as peeling. On the other hand, if the pressure is about 0.1 MPa to 10 MPa, it is expected that the post-contact strength and the thermal conductivity will be improved by improving the density of the sintered body. Examples of the heating and pressurizing method include a weight, a spring jig, a pressure jig using silicone rubber, a thermocompression bonding device, and a hot plate pressing device.

Through the above steps, as shown in FIG. 2, the semiconductor element 2 and the semiconductor element mounting support member 3 are joined via the sintered body (sintered metal layer) 4 of the die bond sheet. The semiconductor device 100 can be obtained.

FIG. 3 is a schematic cross-sectional view showing an example of the semiconductor device of the present embodiment. The semiconductor device 110 shown in FIG. 3 includes a semiconductor element 14 connected to the lead frame 11a via a sintered metal layer 4, and a mold resin 13 for molding the semiconductor elements 14. The semiconductor element 14 is connected to the lead frame 11b via a wire 12.

FIG. 4 is a schematic cross-sectional view showing an example of the semiconductor device of the present embodiment. The semiconductor device 200 shown in FIG. 4 includes an insulating substrate 21 having a first electrode 22 and a second electrode 24, a semiconductor element 23 bonded to the first electrode 22 by a sintered metal layer 4, and a semiconductor. A metal wiring 25 for electrically connecting the element 23 and the second electrode 24 is provided. The metal wiring 25 and the semiconductor element 23, and the metal wiring 25 and the second electrode 24 are joined by a sintered metal layer 4, respectively. Further, the semiconductor element 23 is connected to the third electrode 26 via a wire 27. The semiconductor device 200 includes a metal plate 28 on the side of the insulating substrate 21 opposite to the surface on which the electrodes and the like are mounted. In the semiconductor device 200, the structure is sealed with an insulator 29. The semiconductor device 200 has one semiconductor element 23 on the first electrode 22, but may have two or more. In this case, the plurality of semiconductor elements 23 can be joined to the metal wiring 25 by the sintered metal layer 4, respectively.

FIG. 5 is a schematic cross-sectional view showing an example of the semiconductor device of the present embodiment. In the semiconductor device 210 shown in FIG. 5, a block body 30 is provided between the semiconductor element 23 and the metal wiring 25, and the semiconductor element 23 and the block body 30 and the block body 30 and the metal wiring 25 are sintered. It has the same configuration as the semiconductor device 200 shown in FIG. 4, except that it is joined by the metal layer 4. The position of the block body 30 can be changed as appropriate, and may be provided between the first electrode 22 and the semiconductor element 23, for example. As the block body 30, generally, a block body 30 having excellent thermal conductivity and conductivity can be used.

FIG. 6 is a schematic cross-sectional view showing an example of the semiconductor device of the present embodiment. The semiconductor device 220 shown in FIG. 6 is shown in FIG. 5, except that the semiconductor element 23, the block body 30, and the sintered metal layer 4 for joining the semiconductor element 23 and the block body 30 are further provided on the first electrode 22. It has the same configuration as the semiconductor device 210. The semiconductor device 220 has two semiconductor elements on the first electrode 22, but may have three or more. In this case as well, the three or more semiconductor elements 23 can be joined to the metal wiring 25 by the sintered metal layer 4 via the block body 30, respectively. The position of the block body 30 can be changed as appropriate, and may be provided between the first electrode 22 and the semiconductor element 23, for example.

FIG. 7 is a schematic cross-sectional view showing an example of the semiconductor device of the present embodiment. In the semiconductor device 300 shown in FIG. 7, the first electrode 22, the semiconductor element 23 bonded to the first electrode 22 by the sintered metal layer 4, the semiconductor element 23, and the second electrode 24 are electrically connected to each other. It is provided with a metal wiring 25 for connecting to the object. The metal wiring 25 and the semiconductor element 23, and the metal wiring 25 and the second electrode 24 are joined by a sintered metal layer 4, respectively. Further, the semiconductor element 23 is connected to the third electrode 26 via a wire 27. In the semiconductor device 300, the structure is sealed with a sealing material 31. The semiconductor device 300 has one semiconductor element 23 on the first electrode 22, but may have two or more. In this case, the plurality of semiconductor elements 23 can be joined to the metal wiring 25 by the sintered metal layer 4, respectively.

FIG. 8 is a schematic cross-sectional view showing an example of the semiconductor device of the present embodiment. In the semiconductor device 310 shown in FIG. 8, a block body 30 is provided between the semiconductor element 23 and the metal wiring 25, and the semiconductor element 23 and the block body 30 and the block body 30 and the metal wiring 25 are made of sintered metal, respectively. It has the same configuration as the semiconductor device 300 shown in FIG. 7, except that it is joined by the layer 4. The position of the block body 30 can be changed as appropriate, and may be provided between the first electrode 22 and the semiconductor element 23, for example.

FIG. 9 is a schematic cross-sectional view showing an example of the semiconductor device of the present embodiment. The semiconductor device 320 shown in FIG. 9 is shown in FIG. 8 except that the semiconductor element 23, the block body 30, and the sintered metal layer 4 for joining the semiconductor element 23 and the block body 30 are further provided on the first electrode 22. It has the same configuration as the semiconductor device 310. The semiconductor device 320 has two semiconductor elements on the first electrode 22, but may have three or more. In this case as well, the three or more semiconductor elements 23 can be joined to the metal wiring 25 by the sintered metal layer 4 via the block body 30, respectively. The position of the block body 30 can be changed as appropriate, and may be provided between the first electrode 22 and the semiconductor element 23, for example.

FIG. 10 is a schematic cross-sectional view showing an example of the semiconductor device of the present embodiment. In the semiconductor device 400 shown in FIG. 10, the first heat conductive member 32, the semiconductor element 23 bonded to the first heat conductive member 32 via the sintered metal layer 4, and the semiconductor element 23 are sintered. A block body 30 joined via a metal layer 4 and a second heat conductive member 33 joined onto the block body 30 via a sintered metal layer 4 are provided. The semiconductor element 23 is connected to the electrode 34 via a wire 35. In the semiconductor device 400, the space between the first heat conductive member 32 and the second heat conductive member is sealed with a sealing material 31. Although the semiconductor device 400 has two semiconductor elements, it may have one or three or more, and the number of blocks can be appropriately changed. The position of the block body 30 can be changed as appropriate, and may be provided between the first electrode 22 and the semiconductor element 23, for example. The heat conductive member has both a function of releasing heat generated from the semiconductor element 23 to the outside and a function of an electrode for electrically connecting the semiconductor element to the outside.

As described above, the die bond sheet of the present embodiment can also be used for manufacturing the semiconductor device shown in FIGS. 4 to 10 having a structure different from that of the semiconductor device 110 shown in FIG. For example, the semiconductor device having the structure shown in FIGS. 4 to 10 can be suitably used in a situation where a large capacity and high reliability are required. In these structures, the wire connection which is inferior in connection reliability to the terminal on the upper part of the semiconductor element is eliminated, and instead, the metal wiring 25 and the block body 30 are joined by the sintered metal layer 4 which is a sintered body of the die bond sheet. By doing so, high temperature cycle reliability can be obtained.

Examples of the semiconductor device obtained by using the die bond sheet of the present embodiment include a power module including a diode, a rectifier, a thyristor, a MOS gate driver, a power switch, a power MOSFET, an IGBT, a Schottky diode, a fast recovery diode, and a transmitter. Examples include amplifiers and LED modules. The power module, transmitter, amplifier, and LED module obtained by using the die bond sheet of the present embodiment can have high adhesiveness between the semiconductor element and the support member for mounting the semiconductor element.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

(Material of paste-like composition)
CH-0200: Sub-micro copper particles (manufactured by Mitsui Mining & Smelting Co., Ltd., product name "CH-0200", 50% volume average particle size 0.3 μm).
MA-025KFD: Micro copper particles (manufactured by Mitsui Mining & Smelting Co., Ltd., product name "MA-025KFD", flake-shaped, 50% volume average particle size 4 μm).
Zinc particles: Zinc particles (made by Alfa-Aesar, flakes)
Poly (propylene carbonate): Pyrolytic resin (manufactured by Sigma-Aldrich)
Propylene carbonate: Solvent (manufactured by Wako Pure Chemical Industries, Ltd., product name "4-methyl-1,3-dioxolane-2-one")

(Example 1)
8.84 g of propylene carbonate as a dispersion medium and 3.30 g of poly (propylene carbonate) as a pyrolytic resin were mixed in a plastic bottle, sealed, and allowed to stand to dissolve. To this 60% by volume poly (propylene carbonate) solution, 26.21 g of CH-0200 as submicrocopper particles was added, and the mixture was stirred with a spatula until the dry powder disappeared. Further, the treatment was carried out 15 times using a 3-roll mill (M-50, manufactured by EXAKT). To 25.6 g of this dispersion treatment liquid, 4.38 g of micro copper particles MA-025KFD and 0.044 g of zinc particles (manufactured by Alfa-Aesar) are added, stirred with a spatula until the dry powder disappears, and the mixture is sealed and revolved. Using a mold stirrer (Planetry Vacuum Mixer ARV-310, manufactured by Shinky Co., Ltd.), the mixture was stirred at 2000 rpm for 1 minute and treated 5 times with a 3-roll mill to obtain a paste-like composition.

(Examples 2 to 4 and Comparative Examples 1 to 3)
A paste-like composition was obtained in the same manner as in Example 1 except that the composition was changed as shown in Table 2.

[Sheet formability]
The paste-like compositions of each Example and Comparative Example are applied in a film form on a Teflon (registered trademark) coated stainless steel plate using a baker applicator (YBA5 type, manufactured by Yoshimitsu Seiki Co., Ltd.) with a gap of 250 μm. bottom. The stainless steel plate was left on a hot plate at 90 ° C. for 2 hours to remove the solvent. After returning to room temperature (25 ° C.), the dry film of the paste-like composition was peeled off to obtain a self-supporting film. This self-supporting film was cut to obtain a die bond sheet. The film thickness of the die bond sheet was measured using a digital linear gauge (DG-525H, manufactured by Ono Sokki Co., Ltd.) and found to be 120 μm. In this step, those that could form the die bond sheet were evaluated as ◯, and those that could not form the die bond sheet were evaluated as x. The results are shown in Table 3.

[Temporary crimpability evaluation, die shear strength measurement]
A die bond sheet cut into 5 mm x 5 mm is placed on a copper substrate 30 mm x 25 mm x 3 mm, titanium and nickel are formed on the copper substrate in this order, and a silicon chip having a 3 mm x 3 mm adherend surface is nickel-plated. Was placed and preheated in air for 5 minutes using a heat-pressing device (manufactured by Tester Sangyo Co., Ltd.) heated to 130 ° C., and then treated in air at 1 MPa for 1 minute for temporary bonding. In this step, those in which the temporary crimping between the copper substrate and the silicon chip was successfully performed were evaluated as ◯.

The temporarily bonded sample was placed in an atmosphere-controllable tube oven (manufactured by ABC) and treated in hydrogen under the conditions of a temperature rise of 30 minutes and a holding temperature of 300 ° C. for 1 hour. Then, the adhesive strength of the die bond sheet was evaluated by the die shear strength. Using a universal bond tester (4000 series, manufactured by DAGE) equipped with a DS-100 load cell, the silicon chip was pushed horizontally at a measurement speed of 5 mm / min and a measurement height of 50 μm to measure the die shear strength of the die bond sheet. The average value of the measured values of the three silicon chips was taken as the die shear strength. The results are shown in Table 3.

As shown in Table 3, a die bond sheet in which the amount of poly (propylene carbonate) added as a pyrolytic resin was less than 5% by mass did not form a self-supporting film. On the other hand, the die bond sheet having an addition amount of 5% by mass or more was a self-standing film, and the silicon chip and the copper substrate could be joined by temporary crimping and firing, and the die shear strength was 20 MPa or more, which was good.

<Observation of cross-sectional morphology>
A sample in which a silicon chip and a substrate are bonded with a die bond sheet is fixed in a cup with a sample clip (Samplklip I, manufactured by Buehler), and an epoxy casting resin (Epomount, manufactured by Refine Tech) is filled around the sample until the entire sample is filled. It was poured, allowed to stand in a vacuum desiccator, and defoamed by reducing the pressure for 1 minute. Then, after leaving it at room temperature (25 ° C.) for 10 hours, the epoxy casting resin was cured in a thermostat at 60 ° C. for 2 hours. Using a refine saw low (manufactured by Refine Tech) equipped with a diamond cutting wheel (11-304, manufactured by Refine Tech), the cast sample was cut near the cross section to be observed. The cross section was ground with a polishing device (Refine Polisher HV, manufactured by Refine Tech) equipped with water resistant polishing paper (Carbomac Paper, manufactured by Refine Tech) to obtain a crack-free cross section on the silicon chip. Then, the cross section was smoothed with a polishing apparatus set with a buffing polishing cloth dyed with a buffing agent to prepare a sample for SEM. The cross section of the die bond sheet was observed with an SEM device (ESEM XL30, manufactured by Philips) at an applied voltage of 10 kV and various magnifications for the SEM sample. The particles were sintered and fused and bonded to the adherend surface, and were in a good bonding state. Similar results were obtained in other examples.

(Examples 5 to 8, Comparative Examples 4 to 6)
The paste-like compositions of Preparation Examples 1 to 7 were stencil-printed on a copper substrate using a 200 μm-thick stainless steel mask and a squeegee having a 13 mm × 13 mm square opening. Then, it was dried on a hot plate at 90 ° C. for 1 hour to form a die bond sheet on a copper substrate. In this step, those that could form the die bond sheet were evaluated as ◯, and those that could not form the die bond sheet were evaluated as x.

A 3 mm × 3 mm silicon chip having a nickel-plated adherend surface is placed on a die bond sheet formed on a copper substrate, and a heat-bonding device heated to 130 ° C. is used to preheat in air for 5 minutes and then air. Medium 1 MPa, treated for 1 minute for temporary bonding. In this step, those in which the temporary crimping between the copper substrate and the silicon chip was successfully performed were evaluated as ◯, and those in which the temporary crimping was not possible were evaluated as x.

The temporarily bonded sample was placed in an atmosphere-controllable tube oven (manufactured by ABC) and treated in hydrogen under the conditions of a temperature rise of 30 minutes and a holding temperature of 300 ° C. for 1 hour. Then, in the same manner as described above, the adhesive strength of the die bond sheet was evaluated by the die shear strength. The above results are shown in Table 4.

The die bond sheet of the example is not only excellent in thermal conductivity and connection reliability, but also can be handled as a self-supporting film and is also excellent in temporary crimping property. Therefore, it is easy to join the semiconductor element and the support member for mounting the semiconductor element. It is understood that it can be carried out in various steps.

1a, 1b, 1c ... Die bond sheet, 2 ... Semiconductor element, 3 ... Support member for mounting semiconductor element, 4 ... Sintered body (sinter metal layer) of die bond sheet, 11a, 11b ... Lead frame, 12 ... Wire, 13 ... Mold resin, 14 ... Semiconductor element, 21 ... Insulated substrate, 22 ... First electrode, 23 ... Semiconductor element, 24 ... Second electrode, 25 ... Metal wiring, 26 ... Third electrode, 27 ... Wire, 28 ... metal plate, 29 ... insulator, 30 ... block body, 31 ... encapsulant, 32 ... first heat conductive member, 33 ... second heat conductive member, 34 ... electrode, 35 ... wire, 100 ... semiconductor device , 110 ... semiconductor device, 200 ... semiconductor device, 210 ... semiconductor device, 220 ... semiconductor device, 300 ... semiconductor device, 310 ... semiconductor device, 320 ... semiconductor device, 400 ... semiconductor device.

Claims (4)

Copper particles 75 mass% or more and a thermally decomposable resin viewed containing 5 wt% or more,
The copper particles include submicro copper particles having a volume average particle diameter of 0.12 μm or more and 0.8 μm or less, and flake-shaped micro copper particles having a maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of 4 or more. A die bond sheet containing, and the content of the flake-shaped micro copper particles is 50% by mass or less based on the total mass of the copper particles. The die bond sheet according to claim 1, wherein the pyrolytic resin is at least one selected from the group consisting of polycarbonate, polymethacrylic acid, polymethacrylic acid ester, and polyester. The die bond sheet according to claim 1 or 2 , wherein a paste-like composition containing copper particles, a pyrolytic resin, and a dispersion medium is molded and heated. A semiconductor device in which a semiconductor element and a support member for mounting a semiconductor element are joined via a sintered body of the die bond sheet according to any one of claims 1 to 3.

Images