JP6153077B2 - Metal nanoparticle paste, bonding material containing the same, and semiconductor device using the same - Google Patents

Description

  The present invention relates to a metal nanoparticle paste containing Cu nanoparticles, a bonding material containing the same, and a semiconductor device using the bonding material.

  Conventionally, Sn—Pb-based solder has been used for electrode bonding of semiconductor elements, but recently, a new bonding material such as lead-free solder has been demanded from the viewpoint of environmental protection. Also, in semiconductor element bonding technology, materials that can be bonded at a low temperature or without pressure are required to reduce the load on the semiconductor element.

  Metal nanoparticles such as Ag and Cu can be sintered at a temperature much lower than their melting point (sintering temperature 200 ° C. or less) when the particle size is reduced to a nanometer size such as 1000 nm or less. Therefore, application to low-temperature bonding of semiconductor elements is expected.

  However, such metal nanoparticles have a highly active surface and are likely to aggregate, so that they are usually coated with a surfactant or a polymer to ensure dispersion stability. For this reason, when heat treatment is performed when joining semiconductor elements using such metal nanoparticles, the metal nanoparticles are sintered and the coating of surfactant, polymer, etc. is decomposed and gas is generated. , Voids are generated between the metal nanoparticles. As a result, the sintered structure did not become dense at no pressure or low temperature, and a sufficiently high bonding strength could not be obtained.

  11th Symposium on “Microjoining and Assembly Technology in Electronics”, February 3-4, 2005, pp. 229-232 (Non-Patent Document 1) includes 10-50 mass% Cu powder with an average particle size of 10 μm or 30 μm. A composite paste containing Sn powder of 90 to 50% by mass with an average particle size of 10 μm or 25 μm is disclosed. However, when a low temperature bonding of a semiconductor device is performed using a composite paste containing a micrometer-sized powder having an average particle diameter of 10 μm or more, a sufficiently high bonding strength cannot be obtained.

  Japanese Patent Laid-Open No. 2012-46779 (Patent Document 1) discloses metal nanoparticles having an organic coating containing a fatty acid having 8 or more carbon atoms and an aliphatic amine on the surface. It is also described that it is pyrolyzed at low temperatures.

  On the other hand, in the semiconductor device mounting technology using metal nanoparticles, conventionally, the bonding between the semiconductor device and the substrate has been performed under pressure, but the yield is reduced due to chip destruction and the cost is increased due to the addition of production processes. There was a problem, and there was a strong demand for the development of mounting technology by pressureless bonding.

JP 2012-46779 A

Ikeda, et al., “Examination of connection using Cu powder / Sn powder composite paste”, 11th Symposium on “Microjoining and Assembly Technology in Electronics”, February 3-4, 2005, pages 229-232

  However, when the surface-coated Cu nanoparticles described in Patent Document 1 are used, sintering at a low temperature is possible, but voids in the bonding layer are not necessarily sufficiently suppressed, and the bonding strength is not always sufficient. It was not expensive.

  This invention is made | formed in view of the subject which the said prior art has, and provides the metal nanoparticle paste which can form a joining layer with high joining strength at low temperature (specifically 400 degrees C or less). For the purpose.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a bonding layer having high bonding strength by using a metal nanoparticle paste containing Cu nanoparticles and Sn nanoparticles in a specific ratio. It has been found that it can be formed at a low temperature (specifically, 400 ° C. or lower), and the present invention has been completed.

That is, the metal nanoparticle paste of the present invention is characterized by containing 97 to 85 % by mass of Cu nanoparticles and 3 to 15 % by mass of Sn nanoparticles with respect to all metal nanoparticles. In such a metal nanoparticle paste, the metal nanoparticles having a diameter in the range of 1 to 1000 nm are preferably 99% or more of the total metal particles on a number basis. The bonding material of the present invention contains such a metal nanoparticle paste of the present invention.

  The semiconductor device of the present invention includes a semiconductor element, a substrate, and a bonding layer for bonding the semiconductor element and the substrate, and the bonding layer is a mixture of Cu and Sn formed of the bonding material of the present invention. It is characterized by being a layer.

In such a semiconductor device of the present invention, the mixture layer is preferably formed of metal nanoparticles having an average particle diameter of 1 to 1000 nm. The mixture layer preferably includes a CuSn intermetallic compound, and the CuSn intermetallic compound is preferably at least one of Cu ₃ Sn and Cu ₆ Sn ₅ .

Furthermore, in the semiconductor device of the present invention, an adhesive layer made of at least one metal selected from the group consisting of Ni, Co, and Ag is further provided on both surfaces of the bonding layer, and one adhesive layer is the semiconductor layer. It is preferable that it is disposed so as to be in contact with the joint portion of the element, and the other adhesion layer is disposed so as to be in contact with the joint portion of the substrate.

The reason why the metal nanoparticle paste of the present invention makes it possible to form a bonding layer having high bonding strength at a low temperature is not necessarily clear, but the present inventors speculate as follows. That is, since the metal nanoparticle paste of the present invention contains Sn nanoparticles with a melting point of 232 ° C., Sn melted at a temperature of 400 ° C. or less penetrates between the Cu nanoparticles, filling the voids, and firing. It is presumed that the consolidation density is improved and the bonding strength of the bonding layer is increased. In addition, Cu surface nanoparticles and Sn nanoparticles easily react with each other at a low temperature in a short time, and CuSn intermetallic compounds are easily formed. For this reason, Sn nanoparticles that have penetrated between Cu nanoparticles easily form stable and high heat-resistant CuSn intermetallic compounds such as Cu ₃ Sn and Cu ₆ Sn _{5 in the} vicinity of the interface, and are strong and high-strength bonded. It is inferred that a layer is formed. Furthermore, since the oxide layer on the surface of the Cu nanoparticles is easily reduced due to the reduction effect of the Sn nanoparticles, the Cu nanoparticles are easily sintered, the sintering density is improved, and a bonding layer having high bonding strength is formed. Inferred.

  On the other hand, when Sn particles having a micrometer size are used, the Sn particles do not permeate between the Cu particles, and the voids between the Cu particles are not sufficiently filled. Therefore, it is assumed that sufficient bonding strength cannot be obtained. In addition, Cu particles and Sn particles of micrometer size are not highly active on the surface, so it is difficult to sinter at low temperatures, CuSn intermetallic compounds are not easily formed, and it is assumed that the bonding strength is not sufficiently high. Is done.

  In addition, when the bonding layer is formed by heat treatment at a relatively low temperature or heat treatment without pressure using only Cu nanoparticles having an organic coating on the surface, gas generated during decomposition of the organic coating or points between Cu nanoparticles It is presumed that voids are easy to be formed due to the bonding state (linking state) in, and a structure having a low sintered density is formed. For this reason, it is speculated that the bonding strength decreases when only Cu nanoparticles having an organic coating on the surface are used.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the metal nanoparticle paste which can form a joining layer with high joining strength at low temperature (specifically 400 degrees C or less).

It is a schematic diagram which shows one embodiment of the semiconductor device of this invention. It is a schematic diagram which shows another embodiment of the semiconductor device of this invention. It is a schematic diagram which shows another embodiment of the semiconductor device of this invention. It is a schematic diagram which shows another embodiment of the semiconductor device of this invention. It is a schematic diagram which shows the joined body for shear strength measurement produced in the Example. It is a graph which shows the XRD spectrum of the adhesion layer upper part vicinity of the joining layer produced in Example 1-2 . It is a graph which shows the XRD spectrum of the adhesion layer vicinity of the upper side of the joining layer produced in Comparative Example 1-2 . It is a scanning electron micrograph of the adhesion layer vicinity of the upper side of the joining layer produced in Example 1-2 . It is a scanning electron micrograph of the adhesion layer vicinity of the lower side of the joining layer produced in Example 1-2 . It is a scanning electron micrograph of the adhesion layer vicinity of the upper side of the joining layer produced in Example 2-1 . It is a scanning electron micrograph of the adhesion layer vicinity of the lower side of the joining layer produced in Example 2-1 . It is a scanning electron micrograph near the adhesion layer on the upper side of the bonding layer produced in Comparative Example 2-2 . It is a scanning electron micrograph of the adhesive layer vicinity of the lower side of the joining layer produced in Comparative Example 2-2 .

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  First, the metal nanoparticle paste of the present invention and the bonding material of the present invention containing the same will be described. The metal nanoparticle paste of the present invention contains Cu nanoparticles and Sn nanoparticles at a predetermined ratio. The metal nanoparticle paste of the present invention can be sintered by heat treatment at a low temperature (specifically, 400 ° C. or lower) to form a bonding layer having high bonding strength. In addition, when the metal nanoparticle paste of the present invention is used, a bonding layer having high bonding strength can be formed even without pressure during heat treatment.

(Cu nanoparticles)
In the present invention, Cu particles having a diameter in the range of 1 to 1000 nm are referred to as “Cu nanoparticles”. The diameter of Cu particles can be measured by transmission electron microscope (TEM) observation. In the present invention, the ratio of Cu nanoparticles to the total Cu particles shown below and the average of Cu particles (including Cu nanoparticles) are as follows. The particle diameter is a value obtained by randomly extracting 200 Cu particles and measuring their diameters in the TEM observation.

  In the metal nanoparticle paste of the present invention, such Cu nanoparticles (those having a diameter in the range of 1 to 1000 nm) are preferably 99% or more of all Cu particles on a number basis, and all Cu particles are The Cu nanoparticles are particularly preferable. When the ratio of Cu nanoparticles is less than the lower limit, the sintering temperature of Cu particles becomes high, so that bonding of Cu particles due to heating at a low temperature (specifically, 400 ° C. or less) hardly occurs. The strength tends to decrease.

  Moreover, as an average particle diameter of Cu particle | grains (a Cu nanoparticle is included) contained in the metal nanoparticle paste of this invention, 10-1000 nm is preferable, 30-500 nm is more preferable, 50-250 nm is especially preferable. When the average particle diameter of the Cu particles is less than the lower limit, the surface ratio to the bulk is increased, so that the surface of the Cu nanoparticles is easily oxidized in the atmosphere. As a result, the Cu nanoparticles are aggregated in the metal nanoparticle paste. Or the oxidation component cannot be sufficiently removed by heat treatment at the time of bonding, and the characteristics of the bonding material such as bonding strength, conductivity, and thermal conductivity tend to be deteriorated. However, if the Cu nanoparticles are handled in an inert gas or reducing gas atmosphere, the surface of the Cu nanoparticles is less likely to be oxidized, and the above problems are less likely to occur. Therefore, Cu nanoparticles having an average particle diameter of less than the lower limit are also included. It can be used for the metal nanoparticle paste of the present invention. In addition, when using Cu nanoparticles with an organic coating, the organic coating remains higher than the Cu nanoparticles in proportion to the organic coating. There is a tendency that characteristics of the bonding material such as conductivity, thermal conductivity and the like are deteriorated. On the other hand, if the average particle diameter of the Cu particles exceeds the upper limit, the particle size effect is small, so the sintering temperature of the Cu particles increases, and the Cu particles are heated by heating at a low temperature (specifically, 400 ° C. or less). Bonding is difficult to occur, and as a result, the bonding strength tends to decrease.

  Examples of such Cu nanoparticles include surface-coated Cu nanoparticles including Cu nanoparticles and an organic coating containing a fatty acid and an aliphatic amine disposed on the surface of the Cu nanoparticles. The organic coating can be thermally decomposed at a low temperature (specifically, 400 ° C. or lower). The surface-coated Cu nanoparticles can be produced according to the method described in JP 2012-46779 A. That is, Cu nanoparticles are formed by reducing a Cu salt that is insoluble in the alcohol solvent in the presence of a fatty acid and an aliphatic amine in the alcohol solvent, and the fatty acid and the surface of the Cu nanoparticles are formed. The surface-coated Cu nanoparticles can be produced by forming an organic coating containing an aliphatic amine. Here, examples of the Cu salt include copper carbonate and copper hydroxide. Examples of fatty acids include saturated fatty acids such as octanoic acid, decanoic acid, dodecanoic acid, myristic acid, palmitic acid and stearic acid, and unsaturated fatty acids such as oleic acid. Aliphatic amines include octylamine, decylamine and dodecylamine. , Saturated aliphatic amines such as myristylamine, palmitylamine, stearylamine, and unsaturated aliphatic amines such as oleylamine, and by changing the number of carbons in the hydrocarbon chain of fatty acids and aliphatic amines, The particle size can be adjusted.

  In the present invention, commercially available Cu nanoparticles such as a copper nanoparticle powder manufactured by Tech Science Co., Ltd. can also be used. Furthermore, Cu nanoparticles dispersed in a solvent can also be used. As such a Cu nanoparticle dispersion, "Cu60-BtTP" manufactured by IOX Co., Ltd., a copper nanoparticle dispersion manufactured by Tateyama Scientific Industry Co., Ltd., "NCU-09" manufactured by Daiken Chemical Industry Co., Ltd., Commercial products such as copper nanoparticle dispersions manufactured by Harima Chemical Group Co., Ltd. may be mentioned.

(Sn nanoparticles)
In the present invention, Sn particles having a diameter in the range of 1 to 1000 nm are referred to as “Sn nanoparticles”. The diameter of the Sn particles can be measured by transmission electron microscope (TEM) observation. In the present invention, the ratio of Sn nanoparticles to the total Sn particles shown below and the average of Sn particles (including Sn nanoparticles) The particle diameter is a value obtained by randomly extracting 200 Sn particles and measuring these diameters in the TEM observation.

  In the metal nanoparticle paste of the present invention, such Sn nanoparticles (thickness in the range of 1 to 1000 nm) are preferably 99% or more of all Sn particles on a number basis, and all Sn particles The Sn nanoparticles are particularly preferable. When the ratio of the Sn nanoparticles is less than the lower limit, the amount of Sn nanoparticles entering between the Cu nanoparticles decreases, and voids between the Cu nanoparticles are not sufficiently filled, so voids are generated, and the bonding strength is sufficient. There is a tendency not to improve.

  Moreover, as an average particle diameter of Sn particle | grains (a Sn nanoparticle is included) contained in the metal nanoparticle paste of this invention, 5-1000 nm is preferable, 10-500 nm is more preferable, 20-250 nm is especially preferable. When the average particle diameter of the Sn particles is less than the lower limit, the surface ratio to the bulk increases, so that the surface of the Sn nanoparticles is likely to be oxidized in the atmosphere. As a result, the Ag nanoparticles aggregate in the metal nanoparticle paste. Or the oxidation component cannot be sufficiently removed by heat treatment at the time of bonding, and the characteristics of the bonding material such as bonding strength, conductivity, and thermal conductivity tend to be deteriorated. However, if the Sn nanoparticles are handled in an inert gas or reducing gas atmosphere, the surface of the Sn nanoparticles is less likely to be oxidized and the above problems are less likely to occur. It can be used for the metal nanoparticle paste of the present invention. In addition, when using Sn nanoparticles with an organic coating, since the proportion of the organic coating is larger than that of Sn nanoparticles, the organic coating remains without being sufficiently decomposed by the heat treatment during bonding, and the bonding strength There is a tendency that characteristics of the bonding material such as conductivity, thermal conductivity and the like are deteriorated. On the other hand, when the average particle diameter of the Sn particles exceeds the upper limit, Sn nanoparticles cannot enter between the Cu nanoparticles, and voids between the Cu nanoparticles are not sufficiently filled, so voids are generated and the bonding strength is sufficient. It does not tend to improve.

  Examples of such Sn nanoparticles include surface-coated Sn nanoparticles including Sn nanoparticles and an organic coating containing an aliphatic amine disposed on the surface of the Sn nanoparticles. The organic coating can be thermally decomposed at a low temperature (specifically, 400 ° C. or lower). The surface-coated Sn nanoparticles can be produced according to the method described in the specification of Japanese Patent Application No. 2012-130888. That is, Sn nanoparticles are formed by reducing Sn ions in the presence of an aliphatic amine and a quaternary ammonium borohydride in an organic solvent, and the aliphatic amine is formed on the surface of the Sn nanoparticles. The surface-coated Sn nanoparticles can be produced by forming an organic film to be contained. Here, the Sn ion source is not particularly limited as long as it is an Sn compound that is soluble in an organic solvent and generates Sn ions. For example, tin chloride, tin fluoride, tin bromide, tin iodide, acetic acid Examples thereof include tin, tin sulfate, tin nitrate, and acetylacetonatotin. Examples of aliphatic amines include saturated aliphatic amines such as octylamine, decylamine, dodecylamine, myristylamine, palmitylamine, stearylamine, and unsaturated aliphatic amines such as oleylamine. The particle diameter of Sn nanoparticles can be adjusted by changing the number of carbon atoms.

  In the present invention, commercially available Sn nanoparticles such as tin nano powder manufactured by Nippon Ion Co., Ltd. can also be used. Furthermore, Sn nanoparticles dispersed in a solvent can also be used. Examples of such Sn nanoparticle dispersion include commercially available products such as tin nanoparticle dispersion manufactured by Tateyama Science Co., Ltd.

(Metal nano paste)
The metal nanopaste of the present invention contains such Cu nanoparticles and Sn nanoparticles at a predetermined ratio. The ratio of Cu nanoparticles and Sn nanoparticles in the metal nanopaste of the present invention is 99.9 to 70% by mass of Cu nanoparticles and 0.1 to 30% by mass of Sn nanoparticles with respect to all metal nanoparticles. %is there. When the content of Sn nanoparticles is less than the lower limit (that is, the content of Cu nanoparticles exceeds the upper limit), the amount of Sn nanoparticles that enter between the Cu nanoparticles decreases, and the voids between the Cu nanoparticles Is not sufficiently filled, voids are generated and the bonding strength is reduced. Moreover, since the CuSn intermetallic compound is not generated, the bonding strength is reduced. On the other hand, when the content of Sn nanoparticles exceeds the upper limit (that is, the content of Cu nanoparticles is less than the lower limit), the properties of the bonding material such as bonding strength, conductivity, and thermal conductivity are deteriorated. Further, from the viewpoint of higher bonding strength, the content of Cu nanoparticles is preferably 98 to 80% by mass and the content of Sn nanoparticles is preferably 2 to 20% by mass, and the inclusion of Cu nanoparticles It is more preferable that the amount is 97 to 85% by mass and the content of Sn nanoparticles is 3 to 15% by mass. In addition, in the ratio of Cu nanoparticle and Sn nanoparticle, these total amount is 100 mass% with respect to all the metal nanoparticles.

  In the metal nanopaste of the present invention, metal nanoparticles (thickness in the range of 1 to 1000 nm, Cu nanoparticles + Sn nanoparticles) are 99% or more of all metal particles (Cu particles + Sn particles) on a number basis. It is preferable that all metal particles are the metal nanoparticles. When the ratio of the metal nanoparticles is less than the lower limit, the sintering temperature of the metal particles becomes high, so that the metal particles are hardly bonded by heating at a low temperature (specifically, 400 ° C. or less). The strength tends to decrease.

  Such a metal nanopaste of the present invention includes, for example, an organic solvent such that Cu nanoparticles and Sn nanoparticles are mixed so that a predetermined ratio is obtained, and the resulting mixed nanoparticles become a paste. After mixing with a solvent such as Cu, and preparing Cu nanoparticle paste and Sn nanoparticle paste, both are mixed so that Cu nanoparticles and Sn nanoparticles are in a predetermined ratio, or Cu nanoparticle dispersion liquid And Sn nanoparticle dispersion liquid are prepared, and then both are mixed so that Cu nanoparticles and Sn nanoparticles are in a predetermined ratio, and the resulting dispersion liquid of the mixed nanoparticles is made into an evaporator until a paste is formed. It can manufacture by concentrating using etc.

  These nanoparticle pastes and dispersions may be prepared by mixing Cu nanoparticles and Sn nanoparticles with a solvent such as an organic solvent, or commercially available nanoparticle pastes or dispersions as described above. May be used.

  Although there is no restriction | limiting in particular as an organic solvent used for the metal nanopaste of this invention, For example, C5-C18 alkanes, such as tetradecane; C1-C20 things, such as 1-butanol, decanol, and isopropyl alcohol Alcohols; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; triols such as glycerin; cyclic alcohols such as α-terpineol; ketones such as acetone, methyl ethyl ketone, and diethyl ketone; tetrahydrofuran, diethyl ether And ethers such as butyl carbitol; esters such as ethyl acetate and butyl carbitol acetate; aromatic compounds such as benzene, toluene and xylene. Moreover, you may add additives, such as viscosity modifiers, such as a cellulose derivative (for example, ethyl cellulose, hydroxyethyl cellulose) and a glyceride (for example, castor oil) to the metal nano paste of this invention as needed.

  The mixing method of the nanoparticles and the solvent is not particularly limited, and examples thereof include a method using a known stirring device such as a rotation / revolution mixer, a ball mill, or a stirrer.

<Semiconductor device>
Next, the semiconductor device of the present invention will be described. The semiconductor device of the present invention includes a semiconductor element, a substrate, and a bonding layer that bonds the semiconductor element and the substrate, and the bonding layer includes a bonding material (hereinafter referred to as “book”) containing the metal nanopaste of the present invention. It is a mixture layer of Cu and Sn formed by the “joining material of the invention”. Moreover, the semiconductor device of this invention WHEREIN: It is preferable that the said mixture layer is formed with the metal nanoparticle with an average particle diameter of 1-1000 nm. Furthermore, the CuSn intermetallic compound is preferably contained in the mixture layer from the viewpoint of increasing the bonding strength. Examples of such CuSn intermetallic compounds include Cu ₃ Sn and Cu ₆ Sn ₅ , which may include either one or both. In the semiconductor device of the present invention, it is preferable that an adhesive layer made of at least one of Ni, Co, and Ag is further provided on both surfaces of the mixture layer. In this case, one adhesion layer is disposed so as to contact the bonding portion of the semiconductor element, and the other adhesion layer is disposed so as to contact the bonding portion of the substrate.

  There is no restriction | limiting in particular as a semiconductor element which comprises the semiconductor device of this invention, For example, a power element, LSI, resistance, a capacitor | condenser etc. are mentioned. Moreover, there is no restriction | limiting in particular as a board | substrate, For example, a lead frame, the ceramic substrate in which the electrode was formed, a mounting substrate, etc. are mentioned. An example of the lead frame is a copper alloy lead frame. Examples of the ceramic substrate on which the electrode is formed include a DBC (Direct Bond Copper: registered trademark) substrate and an active metal bonded (AMC: Active Metal Copper) substrate. Examples of the mounting substrate include an alumina substrate on which electrodes are formed, a low temperature co-fired ceramics (LTCC) substrate, a glass epoxy substrate, and the like.

  Hereinafter, preferred embodiments of the semiconductor device of the present invention will be described in detail with reference to the drawings. However, the semiconductor device of the present invention is not limited to the drawings. In the following description and drawings, the same or corresponding elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

  FIG. 1 is a schematic view showing an embodiment of a semiconductor device of the present invention. This semiconductor device includes a semiconductor element 1, an upper substrate 2a, a lower substrate 2b, bonding layers 3a and 3b, a signal terminal 5, a bonding wire 6, and a molding resin 7. An upper substrate 2a is bonded to the upper surface of the semiconductor element 1 via a bonding layer 3a. A lower substrate 2b is bonded to the lower surface of the semiconductor element 1 through a bonding layer 3b. A part of the upper surface of the semiconductor element 1 and the signal element 5 are electrically connected by a bonding wire 6. The semiconductor element 1, a part of the upper substrate 2 a, a part of the lower substrate 2 b, the bonding layers 3 a and 3 b, a part of the signal terminal 5, and the bonding wire 6 are covered with the mold resin 7. Further, the protruding portion 2 c of the upper substrate 2 a, the protruding portion 2 d of the lower substrate 2 b, and a part of the signal terminal 5 protrude outside the mold resin 7.

  Such a semiconductor device can be manufactured as follows. That is, first, the bonding material of the present invention is applied to either the upper surface of the semiconductor element 1 or the lower surface of the upper substrate 2a to form a bonding material layer. Also, the bonding material of the present invention is applied to either the lower surface of the semiconductor element 1 or the upper surface of the lower substrate 2b to form a bonding material layer. Although there is no restriction | limiting in particular as thickness of these joining material layers, When productivity and joining resistance are considered, 1-500 micrometers is preferable, 50-400 micrometers is more preferable, 100-300 micrometers is especially preferable. Examples of the method for applying the bonding material include a screen printing method, an ink jet method, a dip method, and a flexographic printing method. Moreover, such application | coating can be performed in air | atmosphere or inert gas atmosphere.

  Next, the semiconductor element 1 and the upper substrate 2a are bonded together so that the bonding material layer is disposed between the upper surface of the semiconductor element 1 and the lower surface of the upper substrate 2a. The semiconductor element 1 and the lower substrate 2b are bonded together so that the bonding material layer is disposed between the upper surface of the lower substrate 2b. At this time, pressure may be applied so that bubbles do not enter the bonding material layer. The bonding may be performed in a vacuum, but the bonding material of the present invention can be bonded in the air because the oxidation of Cu nanoparticles in the air is suppressed.

  In this way, the bonded body in which the semiconductor element 1 and the upper substrate 2a and the semiconductor element 1 and the lower substrate 2b are bonded together is subjected to heat treatment to sinter the bonding material, thereby forming the bonding layers 3a and 3b. Thereby, the semiconductor element 1 and the upper substrate 2a are bonded via the bonding layer 3a, and the semiconductor element 1 and the lower substrate 2b are bonded via the bonding layer 3b. Since the bonding layers 3a and 3b formed of the bonding material of the present invention are a mixture layer of Cu and Sn, the bonding strength is excellent. Since the bonding layers 3a and 3b contain Sn, they tend to act as stress relaxation layers. On the other hand, since the bonding layer made of only Cu has high hardness, the stress is not relieved, and, for example, there is a problem that the semiconductor element is destroyed during the cooling and heating cycle.

Furthermore, the bonding layer according to the present invention preferably contains a CuSn intermetallic compound, and the CuSn intermetallic compound is preferably at least one of Cu ₃ Sn and Cu ₆ Sn ₅ . By including such a CuSn intermetallic compound, the bonding strength of the bonding layer tends to be improved. In the bonding layer according to the present invention, CuSn intermetallic compounds are formed during sintering, so that the Cu nanoparticles are not completely sintered, and the particle diameter in the bonding material of the present invention is maintained. However, it tends to be sintered. As a result, the obtained bonding layer (mixture layer) tends to be formed of metal nanoparticles having an average particle diameter of 1 to 1000 nm (more preferably 10 to 1000 nm). The bonding layer formed of such metal nanoparticles can be confirmed by observation with a scanning electron microscope or the like.

  Although there is no restriction | limiting in particular as temperature of heat processing, 150-450 degreeC is preferable and 250-400 degreeC is more preferable. When the heat treatment temperature is less than the lower limit, the solvent contained in the bonding material tends to remain in the bonding layers 3a and 3b, and sufficient bonding strength tends not to be obtained. In some cases, the temperature exceeds the heat-resistant temperature of the semiconductor element, the thermal stress increases, the warp or peeling tends to occur, and the bonding layer may be oxidized.

  Such heat treatment is preferably performed in an inert gas or reducing gas atmosphere. Furthermore, when the bonding material of the present invention is used, bonding can be performed without applying pressure, but bonding strength tends to be improved by bonding while applying pressure.

  In the semiconductor device of the present invention, as shown in FIG. 2, between the semiconductor element 1 and the bonding layer 3a, between the upper substrate 2a and the bonding layer 3a, between the semiconductor element 1 and the bonding layer 3b, It is preferable that adhesion layers 4a and 4b made of at least one of Ni, Co, and Ag are disposed between the lower substrate 2b and the bonding layer 3a. By forming such an adhesion layer, the bonding strength tends to be further improved.

  The thickness of such an adhesion layer is not particularly limited because high bonding strength can be obtained if it is 1 nm or more, but it is preferably 10 μm or less in consideration of the production cost of the semiconductor device, the electric resistance of the adhesion layer, and the like. Moreover, 200 nm or less is more preferable from a viewpoint of reducing production cost more.

  Such a semiconductor device can be manufactured as follows. That is, first, the adhesion layer is formed on both surfaces of the semiconductor element 1, the lower surface of the upper substrate 2a, and the upper surface of the lower substrate 2b. Examples of the method for forming the adhesion layer include a sputtering method, a plating method, and a coating method.

  In the case of forming an adhesion layer by sputtering, first, an object to be coated such as a semiconductor element or a substrate is inserted into a vacuum chamber, and the inside of the chamber is decompressed. After the inside of the chamber is in a vacuum state, argon gas is introduced, and RF plasma is generated on the object to be coated to remove impurities on the surface of the object to be coated. Thereafter, RF sputtering is performed using a target of the material of the adhesion layer to be formed (for example, Ni, Co, or Ag). Thereby, an adhesion layer can be formed on the surface of an object to be coated. Although there is no restriction | limiting in particular as a temperature of the to-be-coated object at the time of forming a contact | glue layer, For example, room temperature (about 25 degreeC)-450 degreeC are preferable. If the temperature of the object to be coated exceeds the upper limit, the heat resistance temperature of the semiconductor element may be exceeded, the thermal stress increases, and warping or peeling tends to occur.

  In the case of forming an adhesion layer by a coating method, first, a metal mask method, an ink jet method, a spin coating method, a dip method, an object to be coated such as a semiconductor element or a substrate in the air or an inert gas atmosphere, A paste or ink containing the material (for example, Ni, Co, or Ag) of the adhesion layer to be formed is applied by a method such as a screen printing method. As the paste or ink, a paste prepared by mixing metal particles and a solvent may be used, or a commercially available paste containing metal particles may be used. Examples of commercially available pastes containing nickel particles include nickel nanoparticle dispersions manufactured by Tateyama Kagaku Kogyo Co., Ltd., “MM12-800TO” manufactured by Daiken Chemical Industries, Ltd., and the like. Examples of commercially available pastes containing cobalt particles include cobalt nanoparticle dispersions manufactured by Tateyama Science Co., Ltd. Examples of commercially available pastes containing silver particles include “AGIN-W4A” manufactured by Sumitomo Electric Industries, Ltd. and “NPS-J-HTB” manufactured by Harima Chemical Co., Ltd. The adhesion layer is formed by heat-treating the object to which the paste is applied in this manner in an inert gas or reducing gas atmosphere. Note that heat treatment may be performed in an oxidizing atmosphere before heat treatment in an inert gas or reducing gas atmosphere. Although there is no restriction | limiting in particular as atmospheric temperature in heat processing, 150-450 degreeC is preferable. When the atmospheric temperature is lower than the lower limit, the organic components (for example, organic solvent and organic modifier) in the paste are not sufficiently volatilized and removed, and the content of the organic components in the adhesion layer tends to increase. On the other hand, when the upper limit is exceeded, the heat resistance temperature of the semiconductor element may be exceeded, the thermal stress increases, and warping and peeling tend to occur.

  Next, as in the case of the semiconductor device shown in FIG. 1, a bonding material layer is formed on the surface of the adhesion layer thus formed using the bonding material of the present invention, and the semiconductor element 1 and the upper substrate 2a. Then, the semiconductor element 1 and the lower substrate 2b are bonded together, and the obtained bonded body is subjected to heat treatment to sinter the bonding material, thereby forming the bonding layers 3a and 3b. Thereby, the semiconductor element 1 and the upper substrate 2a are bonded via the bonding layer 3a and the adhesion layers 4a and 4b, and the semiconductor element 1 and the lower substrate 2b are bonded via the bonding layer 3b and the adhesion layers 4a and 4b. The Thus, by forming the adhesion layer made of at least one metal of Ni, Co, and Ag, the bonding strength tends to be further improved.

  The reason why the bonding strength is further improved by forming the adhesion layer is not necessarily clear, but the present inventors infer as follows. That is, the passive oxide layer formed on the metal surface such as Ni is thin and easily reduced, and the metal layer such as Ni also has an action of reducing the oxide layer on the surface of the Cu nanoparticles. In addition, since a metal layer such as Ni has very high wettability with Cu nanoparticles during sintering, it is presumed that an adhesion layer having high bonding strength can be formed even without pressure.

  As described above, the semiconductor device of the present invention has been described by taking the case where the semiconductor element is sandwiched between the upper electrode and the lower electrode (FIGS. 1 and 2) as an example, but the semiconductor device of the present invention is not limited to these. For example, as shown in FIGS. 3 and 4, a semiconductor device in which only one surface of a semiconductor element is bonded to a substrate through a bonding layer can be given.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. Various metal nanoparticles used in Examples and Comparative Examples were prepared by the following method.

(Preparation Example 1)
<Preparation of Cu nanoparticles>
Cu nanoparticles were prepared according to the method described in JP 2012-46779 A. That is, when 300 ml of ethylene glycol (HO (CH ₂ ) ₂ OH) was put into a flask and 60 mmol of copper carbonate (CuCO ₃ · Cu (OH) ₂ · H ₂ O) was added thereto, the copper carbonate was hardly added to ethylene glycol. It precipitated without dissolving. To this was added 90 mmol of decanoic acid (C ₉ H ₁₉ COOH) and 30 mmol of decylamine (C ₁₀ H ₂₁ NH ₂ ), and then the mixture was heated to reflux for 1 hour at the boiling point of ethylene glycol while flowing nitrogen gas at 1 L / min. However, fine particles were generated. The obtained fine particles were recovered by dispersing in hexane, washed with acetone and ethanol sequentially added, recovered by centrifugation (3000 rpm, 20 min), and vacuum-dried (35 ° C., 30 min).

  About the obtained fine particles, an X-ray diffractometer (“Rigaku Co., Ltd.“ sample horizontal strong X-ray diffractometer RINT-TTR ”) was used, X-ray source: CuKα ray (λ = 0.15418 nm), tube voltage: Powder X-ray diffraction (XRD) measurement was performed under the conditions of 50 kV and tube current: 300 mA. The metal component was identified from the obtained XRD spectrum, and it was confirmed that Cu was the main component.

  In addition, the obtained Cu fine particles are dispersed in toluene, and this dispersion is dispersed in a Cu microgrid (Aken Shoji Co., Ltd.) with an elastic carbon support film (polymer material film (15 to 20 nm thickness) + carbon film (20 to 25 nm thickness)). The sample for observation was produced by dripping on the product) and air-drying. This observation sample was observed at an accelerating voltage of 200 kV using a transmission electron microscope (TEM, “JEM-2000EX” manufactured by JEOL Ltd.). In this TEM observation, 200 Cu fine particles were randomly extracted and the diameter thereof was measured. As a result, the Cu nanoparticles having a diameter in the range of 1 to 1000 nm were 100% (number basis) of the total Cu fine particles. Moreover, these average particle diameters were 200 nm.

(Preparation Example 2)
<Preparation of Cu particles>
Cu particles were prepared in the same manner as in Preparation Example 1 except that 30 mmol of hexanoic acid (C ₅ H ₁₁ COOH) and 30 mmol of hexylamine (C ₆ H ₁₃ NH ₂ ) were used instead of decanoic acid and decylamine. When the obtained Cu particles were observed in the same manner as in Preparation Example 1 except that a scanning electron microscope (SEM, “S-3600N” manufactured by Hitachi, Ltd.) was used, the average particle diameter was 1.5 μm. It was.

(Preparation Example 3)
<Preparation of Sn nanoparticles>
The flask was charged with 120 ml of tetrahydrofuran (THF), to which 10.8 mmol of tin chloride (SnCl ₂ ), 96 mmol of oleylamine (C ₁₈ H ₃₅ NH ₂ ) and 21.6 mmol of tetrabutylammonium borohydride (TBABH) were added, and then nitrogen was added. While flowing gas at 1 L / min, the mixture was stirred at 50 ° C. for 3 hours to carry out a synthesis reaction to obtain a THF dispersion containing fine particles.

  The THF dispersion is subjected to centrifugation (3000 rpm, 10 min), and the resulting precipitate is dispersed in ethanol, and then centrifuged again (3000 rpm, 20 min) to collect fine particles, followed by vacuum drying (35 ° C. , 30 min).

  About the obtained fine particles, an X-ray diffractometer (“Rigaku Co., Ltd.“ sample horizontal strong X-ray diffractometer RINT-TTR ”) was used, X-ray source: CuKα ray (λ = 0.15418 nm), tube voltage: Powder X-ray diffraction (XRD) measurement was performed under the conditions of 50 kV and tube current: 300 mA. The metal component was identified from the obtained XRD spectrum, and it was confirmed that Sn was the main component.

  In addition, the obtained Sn fine particles were dispersed in toluene, and this dispersion was dispersed into a Cu microgrid (Aken Shoji Co., Ltd.) with an elastic carbon support film (polymer material film (15 to 20 nm thickness) + carbon film (20 to 25 nm thickness)). The sample for observation was produced by dripping on the product) and air-drying. This observation sample was observed at an accelerating voltage of 200 kV using a transmission electron microscope (TEM, “JEM-2000EX” manufactured by JEOL Ltd.). In this TEM observation, 200 Sn fine particles were randomly extracted and the diameter thereof was measured. As a result, the Sn nanoparticles having a diameter in the range of 1 to 1000 nm accounted for 100% of all Sn fine particles (number basis). Moreover, these average particle diameters were 25 nm.

(Preparation Example 4)
<Preparation of Cu nanoparticles>
30 mmol of copper carbonate (CuCO ₃ · Cu (OH) ₂ · H ₂ O), 30 mmol of dodecanoic acid (C ₁₁ H ₂₃ COOH) and 30 mmol of dodecylamine (C ₁₂ H ₂₅ NH ₂ ) instead of decanoic acid and decylamine Cu fine particles were prepared in the same manner as in Preparation Example 1 except for the above. The obtained Cu fine particles were observed in the same manner as in Preparation Example 1. In TEM observation, 200 Cu fine particles were randomly extracted and the diameters thereof were measured. As a result, Cu nanoparticles in the range of 1 to 1000 nm in diameter were 100% of all Cu fine particles (number basis). Moreover, these average particle diameters were 60 nm.

(Preparation Example 5)
<Preparation of Cu nanoparticles>
30 mmol of copper carbonate (CuCO ₃ · Cu (OH) ₂ · H ₂ O), 30 mmol of octanoic acid (C ₇ H ₁₅ COOH) and 30 mmol of octylamine (C ₈ H ₁₇ NH ₂ ) instead of decanoic acid and decylamine Cu fine particles were prepared in the same manner as in Preparation Example 1 except for the above. The obtained Cu fine particles were observed in the same manner as in Preparation Example 1. In TEM observation, 200 Cu fine particles were randomly extracted and the diameters thereof were measured. As a result, Cu nanoparticles in the range of 1 to 1000 nm in diameter were 100% of all Cu fine particles (number basis). Moreover, these average particle diameters were 300 nm.

( Comparative Example 1-1 )
Cu nanoparticles prepared in Preparation Example 1 and Sn nanoparticles prepared in Preparation Example 3 are ground and mixed in a mortar, and 99% by mass of Cu nanoparticles and 1% by mass of Sn nanoparticles with respect to all metal nanoparticles. A mixed powder containing was prepared. To 1 g of this mixed powder, 50 μl of decanol and 50 μl of α-terpineol were added and stirred by a rotating / revolving mixer to prepare a bonding material paste.

<Bonding strength measurement>
In a semiconductor device composed of a lead frame, a semiconductor element, etc., it is difficult to directly measure the bonding strength of the bonding layer. Therefore, the bonding strength of the bonding layer formed of the obtained bonding material was measured by the following method using the bonded body for measuring shear strength shown in FIG.

  First, on one surface of a test piece 8a (diameter 5 mmφ × height 2 mm) made of oxygen-free copper (C1020) and on one surface of a test piece 8b (10 mm × 22 mm × 3 mm) made of oxygen-free copper (C1020), respectively. Ni adhesion layers 10a and 10b having a thickness of 40 nm were formed by RF sputtering.

  Next, a bonding material paste is applied to the surface of the Ni adhesion layer 10b on the test piece 8b by a screen printing method using a metal mask (diameter 5 mmφ × thickness 0.15 mm), and the bonding material layer (diameter 5 mmφ × thickness). 150 μm) was formed. The test piece 8a and the test piece 8b were bonded so that the bonding material layer and the Ni adhesion layer 10a on the test piece 8a were in contact with each other, and preheated at 200 ° C. for 10 minutes in a hydrogen atmosphere under no pressure. Then, the heat processing for 5 minutes were performed at the joining temperature of 400 degreeC, and the bonded body for shear strength measurement (FIG. 5) in which the test piece 8a and the test piece 8b were joined by the joining layer 9 was produced.

In this way, three joined bodies for measuring shear strength were prepared, and these shear strengths were measured at room temperature (20 ° C.) and shear rate of 1 mm / min using an Instron universal testing machine (Instron). The average value of these values was taken as the bonding strength of the bonding layer formed of the bonding material. The results are shown in Table 1 .

(Examples 1-1 to 1-2, Comparative Example 1-2 )
A bonding material paste was prepared in the same manner as in Comparative Example 1-1 except that the contents of Cu nanoparticles and Sn nanoparticles were changed to the ratios shown in Table 1, and further a bonded body for measuring shear strength was prepared and bonded. The bond strength of the layers was determined. The results are shown in Table 1 .

The bonding layer formed in Example 1-2 (Sn: 10 wt%) and the bonding layer formed in Comparative Example 1-2: The XRD spectrum around the upper contact layer 10a of (Sn 30 wt%) was measured However, as shown in FIGS. 6 to 7 , in addition to the diffraction peaks derived from Cu, diffraction peaks derived from Cu ₃ Sn and Cu ₆ Sn ₅ are observed, and CuSn intermetallic compounds (Cu ₃ Sn and Cu) are observed. ₆ Sn ₅ ) was confirmed to be generated.

Further, the cross section of the bonding layer (Sn: 10% by mass) formed in Example 1-2 near the upper adhesion layer 10a and the lower adhesion layer 10b was observed with a scanning electron microscope (SEM). As shown in FIG. 8A and FIG. 8B , it was confirmed that the average particle diameter was 1000 nm or less in any part. This is because, in the bonding layer formed using the bonding material paste, Cu nanoparticles are not completely sintered (sintering is suppressed) due to the formation of the CuSn intermetallic compound. This is considered to be because the Cu nanoparticles were sintered while maintaining the particle diameter at.

(Example 1-3 )
The Cu nanoparticles prepared in Preparation Example 1 were mixed with Cu powder having an average particle diameter of 1.2 μm (the ratio of Cu nanoparticles having a diameter of 1 to 1000 nm with respect to the total Cu particles (number basis): 20%). A Cu mixed powder containing 99% of Cu nanoparticles on a number basis was prepared. 97 mass% of this Cu mixed powder and 3 mass% of Sn nanoparticles prepared in Preparation Example 3 were ground and mixed in a mortar to prepare a mixed powder containing Cu nanoparticles and Sn nanoparticles. A bonding material paste was prepared in the same manner as in Comparative Example 1-1 except that 1 g of this mixed powder was used. Further, a bonded body for measuring shear strength was prepared to determine the bonding strength of the bonding layer. The results are shown in Table 1.

(Comparative Example 1-3 )
A bonding material paste was prepared in the same manner as in Comparative Example 1-1 except that the Sn nanoparticles were not mixed, and a bonded body for measuring shear strength was prepared to determine the bonding strength of the bonding layer. The results are shown in Table 1 .

(Comparative Examples 1-4 to 1-6 )
A bonding material paste was prepared in the same manner as in Comparative Example 1-1 except that the contents of Cu nanoparticles and Sn nanoparticles were changed to the ratios shown in Table 1, and further a bonded body for measuring shear strength was prepared and bonded. The bond strength of the layers was determined. The results are shown in Table 1 .

As is clear from the results shown in Table 1, a bonding layer formed of a bonding material containing 97 to 85 % by mass of Cu nanoparticles and 3 to 15 % by mass of Sn nanoparticles with respect to all metal nanoparticles ( The bonding strength of Examples 1-1 to 1-2 ) is a bonding layer formed of a bonding material that does not contain Sn nanoparticles (Comparative Example 1-3 ) and a content of Sn nanoparticles exceeding 15 % by mass. It was confirmed that the bonding strength of the bonding layer (Comparative Example 1-2 , 1-4 to 1-6 ) formed of the material was higher.

(Comparative Example 1-7 )
Cu particles prepared in Preparation Example 2 and Sn nanoparticles prepared in Preparation Example 3 are mixed in a mortar and contain 90% by mass Cu particles and 10% by mass Sn nanoparticles with respect to all metal particles. A mixed powder was prepared. A bonding material paste was prepared in the same manner as in Comparative Example 1-1 except that 20 μl of decanol and 20 μl of α-terpineol were added to 0.2 g of this mixed powder. The bonding strength was determined. The results are shown in Table 2. Table 2 also shows the results of Example 1-2 .

(Comparative Example 1-8 )
Joining material in the same manner as Comparative Example 1-7 , except that Cu powder having an average particle size of 24 μm (electrolytic Cu powder manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) was used instead of Cu particles prepared in Preparation Example 2. A paste was prepared, and a bonded body for measuring shear strength was prepared to determine the bonding strength of the bonding layer. The results are shown in Table 2.

As is apparent from the results shown in Table 2, when Cu particles having an average particle diameter exceeding 1 μm are used (Comparative Examples 1-7 to 1-8 ), Cu nanoparticles are used (Example 1). -2 ), it was confirmed that the bonding strength was low.

(Example 2-1 and Comparative Examples 2-1 to 2-2 )
Example 1-2, in the same manner as in Comparative Example 1-1～1-2 prepare a bonding material paste, further except for changing the junction temperature of 350 ° C. Example 1-2, Comparative Examples 1-1 A bonded body for measuring shear strength was prepared in the same manner as in 1-2, and the bonding strength of the bonding layer was determined. The results are shown in Table 3 .

In addition, the bonding layer formed in Example 2-1 (Sn: 10% by mass) and the bonding layer formed in Comparative Example 2-2 (Sn: 30% by mass) in the vicinity of the upper adhesion layer 10a and the lower layer. When the cross section near the adhesion layer 10b was observed with a scanning electron microscope (SEM), as shown in FIGS. 9A to 10B , it was confirmed that the average particle diameter was 1000 nm or less in any part. This is because, in the bonding layer formed using the bonding material paste, Cu nanoparticles are not completely sintered (sintering is suppressed) due to the formation of the CuSn intermetallic compound. This is considered to be because the Cu nanoparticles were sintered while maintaining the particle diameter at.

(Comparative Examples 2-3 to 2-4 )
Comparative Examples 1-3 and 1-4 and in the same manner to prepare a bonding material paste, further Similarly shear strength measuring junction and except for changing the junction temperature of 350 ° C. Comparative Examples 1-3 and 1-4 The body was prepared and the bonding strength of the bonding layer was determined. The results are shown in Table 3 .

As is apparent from the results shown in Table 3, even when the bonding temperature is changed to 350 ° C., 97 to 85 % by mass with respect to all metal nanoparticles is obtained as in the case where the bonding temperature is 400 ° C. A bonding layer (Example 2-1 ) formed of a bonding material containing Cu nanoparticles and 3 to 15 % by mass of Sn nanoparticles is a bonding layer formed of a bonding material not containing Sn nanoparticles (Comparative Example). 2-3 ) and the content of Sn nanoparticles are confirmed to be higher than the bonding strength of bonding layers (Comparative Examples 2-2 and 2-4 ) formed of a bonding material exceeding 15 % by mass. It was done.

(Example 3-1)
The bonding material was the same as in Comparative Example 1-1 except that the Cu nanoparticles prepared in Preparation Example 4 were used as the Cu nanoparticles, and the contents of Cu nanoparticles and Sn nanoparticles were changed to the ratios shown in Table 4. A paste was prepared, and a bonded body for measuring shear strength was prepared in the same manner as in Comparative Example 1-1 to determine the bonding strength of the bonding layer. The results are shown in Table 4.

(Comparative Example 3-1)
A bonding material paste was prepared in the same manner as in Example 3-1, except that the Sn nanoparticles were not mixed, and a bonded body for measuring shear strength was prepared to determine the bonding strength of the bonding layer. The results are shown in Table 4.

  As is clear from the results shown in Table 4, even when Cu nanoparticles having an average particle diameter of 60 nm are used, the bonding layer formed of the bonding material of Example 3-1 contains Sn nanoparticles. It was confirmed that the bonding strength of the bonding layer formed by the bonding material having no bonding (Comparative Example 3-1) was higher.

(Example 4-1)
The bonding material was the same as Comparative Example 1-1 except that the Cu nanoparticles prepared in Preparation Example 5 were used as Cu nanoparticles, and the contents of Cu nanoparticles and Sn nanoparticles were changed to the ratios shown in Table 5. A paste was prepared, and a bonded body for measuring shear strength was prepared in the same manner as in Comparative Example 1-1 to determine the bonding strength of the bonding layer. The results are shown in Table 5.

(Comparative Example 4-1)
A bonding material paste was prepared in the same manner as in Example 4-1, except that Sn nanoparticles were not mixed, and a bonded body for measuring shear strength was prepared to determine the bonding strength of the bonding layer. The results are shown in Table 5.

  As is clear from the results shown in Table 5, even when Cu nanoparticles having an average particle diameter of 300 nm are used, the bonding layer formed of the bonding material of Example 3-1 contains Sn nanoparticles. It was confirmed that the bonding strength of the bonding layer formed by the bonding material having no bonding (Comparative Example 3-1) was higher.

  As described above, according to the present invention, it is possible to obtain a bonding material capable of forming a bonding layer having high bonding strength at no pressure and at a low temperature (specifically, 400 ° C. or lower). Therefore, the metal nanoparticle paste of the present invention is useful as a bonding material in a bonding technique for semiconductor elements at a low temperature or no pressure.

  1: semiconductor element, 2: substrate, 2a: upper substrate, 2b: lower substrate, 2c, 2d: protruding portion of each substrate, 3, 3a, 3b: bonding layer, 4a, 4b: adhesion layer, 5: signal terminal, 6: bonding wire, 7: mold resin, 8a, 8b: test piece, 9: bonding layer, 10a, 10b: adhesion layer.

Claims (8)

A metal nanoparticle paste comprising 97 to 85 % by mass of Cu nanoparticles and 3 to 15 % by mass of Sn nanoparticles with respect to all metal nanoparticles.   2. The metal nanoparticle paste according to claim 1, wherein the metal nanoparticles having a diameter in the range of 1 to 1000 nm are 99% or more of the total metal particles based on the number.   A bonding material comprising the metal nanoparticle paste according to claim 1. Comprising a semiconductor element, a substrate, and a bonding layer disposed between the semiconductor element and the substrate;
A semiconductor device, wherein the bonding layer is a mixed layer of Cu and Sn formed of the bonding material according to claim 3.   The semiconductor device according to claim 4, wherein the mixture layer is formed of metal nanoparticles having an average particle diameter of 1 to 1000 nm.   6. The semiconductor device according to claim 4, wherein a CuSn intermetallic compound is contained in the mixture layer. The semiconductor device according to claim 6, wherein the CuSn intermetallic compound is at least one of Cu ₃ Sn and Cu ₆ Sn ₅ . An adhesive layer made of at least one metal selected from the group consisting of Ni, Co and Ag is further provided on both surfaces of the bonding layer;
8. One of the adhesion layers is disposed so as to be in contact with the bonding portion of the semiconductor element, and the other adhesion layer is disposed so as to be in contact with the bonding portion of the substrate. The semiconductor device according to claim 1.