Metal particle paste, semiconductor device, and method for manufacturing semiconductor device

Abstract

The purpose of the present invention is to provide a technology with which it is possible to increase the reliability of a bonding layer comprising a metal particle paste. The present invention provides a metal particle paste, wherein: the mass percentage of Ag nanoparticles with respect to total metal particles comprising Ag nanoparticles, Sn microparticles, and Ag microparticles is 50-70 wt%; the mass percentage of Sn microparticles with respect to the total metal particles is 10-20 wt%; and the mass percentage of Ag microparticles with respect to the total metal particles is a value obtained by subtracting the mass percentage of Ag nanoparticles and the mass percentage of Sn microparticles from 100 wt%.

Description

Metal Particle Paste, Semiconductor Device, and Method of Manufacturing Semiconductor Device

[0001] The present disclosure relates to a metal particle paste, a semiconductor device, and a method of manufacturing a semiconductor device.

[0002] Improvements in heat resistance, reliability, and heat dissipation of a bonding layer in a semiconductor device are required. In particular, for a bonding layer that bonds a semiconductor element and a bonding member having a large difference in thermal expansion coefficient, improvements in heat resistance, reliability, and heat dissipation are strongly required.

[0003] Conventionally, various solders have been used as a bonding material for a bonding layer. However, in order to satisfy the above requirements, it has been proposed to use a sintering bonding material containing metal particles and an organic solvent. When a bonding layer is formed by pressing and sintering a sintering bonding material, the bonding strength of the bonding layer can be increased. However, if the pressure becomes too large, the semiconductor element may be damaged and may not operate electrically normally. Therefore, a technique for increasing the bonding strength of a bonding layer by optimizing the composition of a sintering bonding material has been proposed (for example, Patent Documents 1 and 2).

[0004] Japanese Patent Application Laid-Open No. 2015-004122, Japanese Patent Application Laid-Open No. 2024-512617

[0005] However, conventional sintering bonding materials have had a problem that a bonding layer having high bonding strength and thus high reliability cannot be formed.

[0006] Therefore, the present disclosure has been made in view of the above problems, and an object thereof is to provide a technique capable of enhancing the reliability of a bonding layer.

[0007] The metal particle paste according to this disclosure comprises Ag nanoparticles having an average particle size of 1 nm or more and less than 1000 nm, Sn microparticles having an average particle size of 1 μm or more and 10 μm or less, and Ag microparticles having an average particle size of 1 μm or more and 10 μm or less, wherein the mass percentage of the Ag nanoparticles to the total metal particles consisting of the Ag nanoparticles, the Sn microparticles, and the Ag microparticles is 50 wt% or more and 70 wt%, the mass percentage of the Sn microparticles to the total metal particles is 10 wt% or more and 20 wt%, and the mass percentage of the Ag microparticles to the total metal particles is the value obtained by subtracting the mass percentage of the Ag nanoparticles and the mass percentage of the Sn microparticles from 100 wt%.

[0008] According to this disclosure, the reliability of the bonding layer made of metal particle paste can be improved.

[0009] The purpose, features, aspects, and advantages of this disclosure will become clearer from the following detailed description and accompanying drawings.

[0010] Figure 1 is a cross-sectional view showing the schematic configuration of the metal particle paste according to Embodiment 1. Figure 2 is a cross-sectional view showing the configuration of the semiconductor device according to Embodiment 1 before bonding. Figure 3 is a cross-sectional view showing the configuration of the semiconductor device according to Embodiment 1 after bonding. Figure 4 is a flowchart showing the manufacturing method of the semiconductor device according to Embodiment 1. Figure 5 is a diagram showing the test results of the examples and comparative examples.

[0011] Before describing Embodiment 1, we will explain the technology that underlies Embodiment 1. In the following description, mass percentage (mass%) is the same as weight percentage (weight%), and wt% is the same as mass%.

[0012] In previous semiconductor devices, lead (Pb)-containing solders, such as Sn-38Pb (mass%) or Pb-5Sn (mass%), or solders primarily composed of tin (Sn), such as Sn-3Ag-0.5Cu (mass%) or Sn-9Zn (mass%) Sn-0.7Cu (mass%), were used as bonding materials to form the bonding layer. Depending on the specifications of the semiconductor device, gold (Au)-containing solders, such as 80Au-20Sn (mass%) or Sn-10Au (mass%), were also used. However, Pb-based solders, which contain large amounts of harmful Pb, pose problems from the perspective of reducing environmental impact, and Au-containing solders present cost problems due to the soaring price of precious metals and limited reserves.

[0013] Based on the above, solder with sn as the main component is considered a candidate for bonding material. However, the melting point of sn is relatively low at 232°C, and in particular, the above-mentioned Sn-3Ag-0.5Cu is a eutectic solder, so its melting point is even lower at approximately 220°C. Therefore, in order to improve the heat resistance of sn-based solder, Sn-5Sb (mass%) or Sn-10Sb (mass%), which have Sb (antimony) added, are considered as candidate bonding materials.

[0014] However, even when Sb is added to Sn-based solder, the melting point of the Sn-based solder only increases by about 20°C at most, from around 230°C to around 240°C. Therefore, the heat resistance of the bonding layer remains a problem for the operating temperature of semiconductor devices during actual operation, as described later. Furthermore, even if a high-melting-point metal with a melting point higher than the eutectic composition is added to the Sn-based solder, the difference between the liquidus and solidus lines widens, which worsens wetting during soldering and leads to a decrease in the reliability of the bonding layer, such as the occurrence of shrinkage cavities and voids.

[0015] Furthermore, when Sn is exposed to low temperatures (below freezing), it undergoes a phase transformation from β-Sn to the fragile α-Sn. Therefore, if a heat cycle test, which alternates between low (-) and high (+) temperatures, is performed on a junction layer made of Sn-based solder, cracks will occur prematurely. When cracks occur in the junction layer, the heat dissipation of the junction layer decreases, causing the temperature of the bonded semiconductor element to increase during actual operation. As a result, a vicious cycle is created in which further cracks occur in the junction layer, potentially leading to thermal runaway of the semiconductor element.

[0016] As described above, solder-based bonding layers have insufficient heat resistance, reliability, and heat dissipation. Therefore, sintered bonding materials are attracting attention as an alternative bonding material to solder. Sintered bonding materials are materials that combine, for example, nano-sized or micro-sized metal particles with an organic solvent, and are called sinterable metals, metal pastes, or metal particle pastes. In sintered bonding materials, the organic components of the organic solvent covering the surface of the metal particles are removed (decomposed, volatilized) by the heat of the manufacturing process, causing the metal particles to sinter and form a bonding layer that joins semiconductor elements to components to be joined, such as circuit boards.

[0017] The heat resistance temperature of the bonding layer of a sintered bonding material is approximately the same as the melting point of the metal particles used in the sintered bonding material (for example, 960°C if the metal particles are silver (Ag) particles), which can be higher than the heat resistance temperature of the bonding layer of solder. Also, depending on the organic components, the boiling point of the organic solvent is approximately 200 to 300°C, so the bonding layer can be formed at a temperature that does not degrade the semiconductor element or the member to be bonded.

[0018] On the other hand, if a sintered bonding material containing metal particles and an organic solvent is sintered without pressure, the heat generated during sintering alone may not be sufficient to adequately promote the diffusion of the metal particles, resulting in insufficient bonding strength and low reliability of the bonded layer. Therefore, when using a sintered bonding material, it is preferable to apply pressure to the sintered bonding material to increase the bonding strength of the bonded layer by ensuring sufficient diffusion of the metal particles and dense sintering. However, if the pressure is too high (for example, applying high pressure of 100 MPa or more during bonding), the semiconductor element may be damaged and may not function electrically properly. Therefore, a technology has been proposed to increase the bonding strength of the bonded layer without applying pressure by optimizing the composition of the sintered bonding material.

[0019] As an example of optimizing the composition of sintered bonding materials, a technique has been proposed in which a bonding layer is formed by sintering only the nanoparticles, using a sintered bonding material composed of Cu nanoparticles and Sn nanoparticles. However, since nanoparticles have a large specific surface area and are easily oxidized, it is thought that the bonding strength will deteriorate. In addition, the Sn nanoparticles may react with the surroundings before the sintering of the Cu nanoparticles progresses, potentially inhibiting the sintering of the Cu nanoparticles. Furthermore, because the sintering shrinkage is large when only nanoparticles are sintered, cracks may form in the bonding layer.

[0020] As another example of optimizing the composition of sintered bonding materials, a technique has been proposed in which a bonding layer is formed using a metal particle paste containing Ag nanoparticles and Sn-based microparticles. However, when the proportion of Sn-based microparticles is low, the intermetallic compounds that are formed by the reaction between molten Sn-based microparticles and Ag and enhance bonding strength are reduced, resulting in insufficient bonding strength of the bonding layer.

[0021] In contrast, the metal particle paste according to this embodiment 1 makes it possible to form a bonded layer with high bonding strength and thus high reliability without pressurized bonding, as will be explained below.

[0022] <Embodiment 1> Figure 1 is a cross-sectional view showing the schematic configuration of a metal particle paste 11 according to this embodiment 1. The metal particle paste 11 in Figure 1 comprises silver (Ag) nanoparticles 1, silver (Ag) microparticles 2, tin (Sn) microparticles 3, and an organic solvent 4.

[0023] The average particle size of Ag nanoparticles 1 is 1 nm or more and less than 1000 nm, the average particle size of Ag microparticles 2 is 1 μm or more and 10 μm or less, and the average particle size of Sn microparticles 3 is 1 μm or more and 10 μm or less. The surfaces of these particles may be covered with a protective film to provide dispersibility and reducing properties.

[0024] The mass percentage of Ag nanoparticles 1 relative to the total metal particles, which consist of Ag nanoparticles 1, Ag microparticles 2, and Sn microparticles 3, is 50 wt% to 70 wt%. The mass percentage of Sn microparticles 3 relative to the total metal particles is 10 wt% to 20 wt%. The mass percentage of Ag microparticles 2 relative to the total metal particles is the value obtained by subtracting the mass percentages of Ag nanoparticles 1 and Sn microparticles 3 from 100 wt%. For example, the values ​​in the examples described later are used for these mass percentages.

[0025] The organic solvent 4 is, for example, an alcohol material with a boiling point of 300°C or lower, and it is preferable that the mass of the organic solvent 4 is 10% to 15% (10 wt% to 15 wt%) of the total mass of the metal particle paste 11.

[0026] Figures 2 and 3 are cross-sectional views showing the configuration of a semiconductor device using the metal particle paste 11 according to this embodiment 1. Figure 2 shows the semiconductor device before bonding, and Figure 3 shows the semiconductor device after bonding. The metal particle paste 11 in Figure 2 is the same as the metal particle paste 11 in Figure 1.

[0027] As shown in Figure 3, the semiconductor device according to this embodiment 1 comprises a bonding layer 12 formed from a metal particle paste 11, a semiconductor element 5, and a circuit board 6 which is the member to be bonded. The semiconductor element 5 is in contact with the bonding layer 12, and the circuit board 6 is in contact with the bonding layer 12 on the side opposite to the semiconductor element 5, thereby bonding the semiconductor element 5 to the circuit board 6 by the bonding layer 12.

[0028] The semiconductor element 5 may be made of ordinary silicon (Si), or silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga ２ O ３ ), or it may be composed of a wide-bandgap semiconductor such as diamond. The operating temperature of a semiconductor element 5 made of ordinary Si is, for example, 100°C to 125°C. The operating temperature of a semiconductor element 5 made of a wide-bandgap semiconductor is, for example, 175°C or higher from the viewpoint of reducing power loss, and it is said that in the future it will be, for example, 250°C.

[0029] The semiconductor device 5 includes, for example, at least one of MOSFET (Metal Oxide Semiconductor Field Effect Transistor), IGBT (Insulated Gate Bipolar Transistor), RC-IGBT (Reverse Conducting-IGBT), SBD (Schottky Barrier Diode), and PND (PN junction diode).

[0030] To suppress cracking of the semiconductor element 5 due to external force, the thickness of the semiconductor element 5 is preferably 100 μm or more. Although not shown in the figures, the semiconductor element 5 has an electrode layer on its upper surface. The electrode layer may be made of an aluminum alloy, and the aluminum alloy may be an aluminum-silicon alloy (Al-Si alloy). A plating layer may also be provided on the upper surface of the electrode layer. The plating layer may be made of gold (Au), nickel or a nickel alloy, or palladium.

[0031] Furthermore, the plating layer may have a laminated structure containing two or more metal layers. If the laminated structure is composed of, for example, a Ni layer, a Pd layer, and an Au layer, it is preferable that the Ni layer, Pd layer, and Au layer be provided in this order from the upper surface side of the semiconductor element 5. By forming the Pd layer on the Ni layer, it is possible to suppress the diffusion of Ni to the interface between the semiconductor element 5 and the junction layer 12. For example, the thicknesses of the Ni layer, Pd layer, and Au layer may be 15 μm, 100 nm, and 200 nm, respectively. Also, the electrode layer and the plating layer may be collectively referred to as the electrode layer.

[0032] The circuit board 6 is provided on the bonding layer 12 side and includes a sinterable metal member (not shown) that can be sintered with the Ag sintered body 8 of the bonding layer 12, which will be described later. The metal member is preferably made of copper, for example. By making the metal member out of copper, the adhesion to the Ag sintered body 8 and the heat dissipation can be improved.

[0033] The bonding layer 12 includes a Sn phase 7, an Ag sintered body 8, and an AgSn-based intermetallic compound phase 9. In the following description, the AgSn-based intermetallic compound phase 9 may be abbreviated as intermetallic compound phase 9.

[0034] The Sn phase 7, which is in contact with the intermetallic compound phase 9, is a thin phase formed by the melting of Sn microparticles 3, and is provided at the respective bonding interfaces of the semiconductor element 5 and the circuit board 6. The Ag sintered body 8 is formed by the sintering of Ag nanoparticles 1 and Ag microparticles 2, and joins the semiconductor element 5 and the circuit board 6.

[0035] The intermetallic compound phase 9 is a phase formed by the reaction of the Ag sintered body 8 and the Sn microparticles 3, and it is in contact with the Ag sintered body 8 and covers its periphery. The intermetallic compound phase 9 contains an Ag component as a trace of the reaction between the Ag sintered body 8 and the Sn microparticles 3. By providing the AgSn-based intermetallic compound phase 9 in the voids of the Ag sintered body 8, the bonding strength between the semiconductor element 5 and the circuit board 6 by the Ag sintered body 8 is increased. However, the AgSn-based intermetallic compound phase 9 itself is brittle, and if the volume fraction of the AgSn-based intermetallic compound phase 9 becomes too large, it will negatively affect the bonding strength of the bonding layer 12, so it is preferable that the volume fraction be 70% or less.

[0036] In this embodiment 1, the volume fraction of the Ag sintered body 8 relative to the bonding layer 12 is 15% or more, and the volume fraction of the intermetallic compound phase 9 relative to the bonding layer 12 is 10% or more. For example, the values ​​of the examples described later are used for these volume fractions.

[0037] <Manufacturing Method> Figure 4 is a flowchart showing the manufacturing method of a semiconductor device according to this embodiment 1. Since the manufacturing method of the semiconductor device according to this embodiment 1 is generally the same as conventional semiconductor device manufacturing methods, the following explanation will mainly focus on the differences from conventional semiconductor device manufacturing methods.

[0038] The semiconductor device manufacturing method shown in Figure 4 includes a metal particle layer formation step (step S1), a semiconductor element arrangement step (step S2), a first bonding step (step S3), a second bonding step (step S4), and a cooling step (step S5).

[0039] First, the metal particle layer formation process (step S1) will be described. A metal particle layer is formed on the circuit board 6 using metal particle paste 11. In this embodiment 1, the metal particle layer is formed by applying metal particle paste 11 to the circuit board 6, but it is not limited to this. The method of applying the metal particle paste 11 may be, for example, metal mask printing or dispensing.

[0040] It is preferable that the boiling point of the organic solvent 4 in the metal particle paste 11 is low so that it is substantially completely removed (decomposed and volatilized) during the heating of the first bonding step (step S3) described later. Examples of organic solvents 4 include texanol, butyl carbitol, butyl carbitol acetate, or hexyl carbitol.

[0041] Furthermore, if the proportion of organic solvent 4 contained in the metal particle paste 11 is increased, the organic solvent 4 may not be removed during heating, or the spacing between metal particles may become too large, preventing the sintering of the metal particles from progressing. For this reason, it is preferable to keep the proportion of organic solvent 4 contained in the metal particle paste 11 low. For example, it is preferable that the content of organic solvent 4 in the metal particle paste 11 be 10% or more and 15 wt% or less.

[0042] Next, the semiconductor element placement step (step S2) will be described. The semiconductor element 5 is placed so as to be in direct contact with the upper surface of the metal particle layer formed in step S1. That is, the metal particle layer of the metal particle paste 11 is placed between the semiconductor element 5 and the circuit board 6.

[0043] When placing the semiconductor element 5, it is preferable to apply a certain amount of pressure to the semiconductor element 5 toward the metal particle layer. The magnitude of the pressure is, for example, 3 N or more and 10 N or less, but it is appropriately changed according to the viscosity of the organic solvent 4 contained in the metal particle layer. The amount of the semiconductor element 5 pushed into the metal particle layer by the pressure is preferably large enough for the metal particle layer to adhere to the entire bonded surface of the semiconductor element 5, and smaller than the extent that a part of the metal particle layer spreads wet to the side surface and the upper surface other than the bonded surface of the semiconductor element 5.

[0044] Next, the first bonding step (step S3) will be described. Heating is performed at a first temperature that is lower than the melting point of the Sn microparticles 3 and higher than the sintering temperature of the Ag particles (Ag nanoparticles 1 and Ag microparticles 2) to remove the organic solvent 4 and sinter the Ag particles. Thereby, the semiconductor element 5 and the circuit board 6 are bonded with a sintered body layer containing the sintered Ag particles. Note that the sintered body layer corresponds to the Ag sintered body 8 and the Ag sintered body phase. The first temperature is preferably, for example, 200°C or more and 220°C or less.

[0045] Here, the sintering process of Ag particles will be described. When the organic solvent 4 covering the surface of the Ag particles is removed by heat, the Ag particles are sintered together to form an Ag sintered body layer (that is, the Ag sintered body 8), and the semiconductor element 5 and the circuit board 6 are sintered and joined. Since the heat-resistant temperature of the sintered body layer after sintering and joining is 960°C, which is about the same as the melting point of Ag, the sintered body layer has higher heat resistance than solder. Note that although it depends on the organic components, the boiling point of the organic solvent 4 is about 200 to 300°C. Even when the first temperature is lower than the boiling point temperature of the organic solvent 4, if the heating rate during heating is slowed down or the heating holding time is lengthened, substantially all of the organic solvent 4 can be volatilized and removed, so sintering and joining can be performed at the first temperature that does not deteriorate the circuit board 6. Note that if the heating rate during heating is fast, the solvent will boil suddenly, which may cause voids in the joining layer. Therefore, the heating rate is preferably 5°C / min or less.

[0046] As an example of the heating method, the structure composed of the circuit board 6, the metal particle layer of the metal particle paste 11, and the semiconductor element 5 obtained in the step of step S2 is placed in a normal-pressure heating furnace filled with an inert gas such as nitrogen, and the temperature in the heating furnace is set to the above first temperature and heated.

[0047] Next, the second joining step (step S4) will be described. The Sn microparticles 3 are melted at a second temperature that is higher than the melting point of the Sn microparticles 3 in at least one of the gaps between the semiconductor element 3, the sintered body layer, and the circuit board 6. That is, the Sn microparticles 3 may be melted in the respective gaps between the semiconductor element 3, the sintered body layer, and the circuit board 6, or may be melted between any two or more of the semiconductor element 3, the sintered body layer, and the circuit board 6. As a result, Sn is interposed in the gap between the semiconductor element 5, the Ag sintered body 8, and the circuit board 6, so that the joining strength between the semiconductor element 5 and the circuit board 6 by the Ag sintered body 8 can be increased. The second temperature is preferably, for example, 240°C or higher. As an example of the heating method, after the first joining step, the temperature in the heating furnace is set to the second temperature, and the structure obtained in the step of step S3 is heated.

[0048] Finally, the cooling process (step S5) will be described. The bonding layer 12 is formed by cooling the structure obtained in step S4.

[0049] Next, a method for evaluating the bonding strength of the bonding layer 12 in response to changes in the volume fraction of the Ag sintered body 8 and the intermetallic compound phase 9 will be described. The volume fractions of the Ag sintered body 8 and the intermetallic compound phase 9 were calculated by cross-sectional observation of the bonding layer using SEM (Scanning Electron Microscope) and from the area fractions of the Ag sintered body 8 and the intermetallic compound phase 9 in the resulting image.

[0050] The bonding strength of the bonding layer was evaluated by shear testing. The shear testing was performed in accordance with the lead-free solder testing method of JIS Z 3198-7. The test speed was 5 mm / min, and the height of the shear tool was set to 30 μm from the circuit board 6 when evaluating the semiconductor element 5 with a chip thickness of 100 μm.

[0051] Figure 5 shows the results of the above tests performed on the examples and comparative examples described later. Figure 5 shows the mixing ratio of the mass of each particle in the metal particle paste 11, the volume fraction of the Ag sintered phase and the intermetallic compound phase in the bonding layer 12, and the evaluation of the bonding strength of the bonding layer 12 by shear test. Test samples with a bonding strength of 40 MPa or more are marked with "○", and test samples with a bonding strength of less than 40 MPa are marked with "×". The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0052] <Example 1> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 50:40:10, and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering a semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0053] <Example 2> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 60:30:10 and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering a semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0054] <Example 3> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 70:20:10 and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering the semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0055] <Example 4> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 50:30:20 and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering the semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0056] <Example 5> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 60:20:20 and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering the semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 min, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0057] <Example 6> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 70:10:20 and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering a semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0058] <Comparative Example 1> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 40:40:20, and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering the semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0059] <Comparative Example 2> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 80:0:20 and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering the semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0060] <Comparative Example 3> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 60:35:5 and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering the semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0061] <Comparative Example 4> A metal particle paste 11 was prepared with a mass ratio of Ag nanoparticles 1: Ag microparticles 2: Sn microparticles 3 = 60:15:25 and applied to the Cu electrode, which is a metal component of the circuit board 6. After forming a sample by adhering the semiconductor element 5 to the applied metal particle paste 11, the sample was placed in a heating furnace at atmospheric pressure with nitrogen sealed inside, heated at a first temperature of 210°C for 60 mins, then heated to a second temperature of 250°C, and removed from the heating furnace.

[0062] <Comparative Examples 5-8> In Comparative Examples 5-8, metal particle pastes were prepared using the mixing ratios of each particle shown in Figure 5.

[0063] <Summary of Embodiment 1> According to the metal particle paste 11 of Embodiment 1, the mass percentage of Ag nanoparticles 1 relative to the total metal particles is 50 wt% or more and 70 wt% or less, the mass percentage of Sn microparticles 3 relative to the total metal particles is 10 wt% or more and 20 wt% or less, and the mass percentage of Ag microparticles 2 relative to the total metal particles is the value obtained by subtracting the mass percentage of Ag nanoparticles 1 and the mass percentage of Sn microparticles 3 from 100 wt%. With such a configuration, as shown in Examples 1 to 6 of Figure 5, the bonding strength of the bonding layer 12 and, consequently, the reliability of the bonding layer 12 can be increased.

[0064] Furthermore, in this embodiment 1, the volume fraction of the Ag sintered body 8 relative to the bonding layer 12 is 15% or more, and the volume fraction of the intermetallic compound phase 9 relative to the bonding layer 12 is 10% or more. With this configuration, as shown in Examples 1 to 6 of Figure 5, the bonding strength of the bonding layer 12 and, consequently, the reliability of the bonding layer 12 can be increased.

[0065] In this disclosure in English, 'a' and 'an' mean one or more. Therefore, 'a', 'an', 'one or more', and 'at least one' can be used interchangeably.

[0066] The configurations shown in the embodiments described above are merely examples of the content of this disclosure and can be combined with other known technologies. Furthermore, the embodiments can be combined with each other, as well as with each other, and variations can be combined. Additionally, parts of the configuration can be omitted or modified without departing from the gist of this disclosure.

[0067] The above explanation is illustrative and not limiting in all respects. It should be understood that countless variations not illustrated are conceivable.

[0068] 1. Ag nanoparticles, 2. Ag microparticles, 3. Sn microparticles, 5. Semiconductor device, 6. Circuit board, 7. Sn phase, 8. Ag sintered body, 9. AgSn-based intermetallic compound phase, 11. Metal particle paste, 12. Bonding layer.

Claims

1. A metal particle paste comprising Ag nanoparticles having an average particle size of 1 nm or more and less than 1000 nm, Sn microparticles having an average particle size of 1 μm or more and 10 μm or less, wherein the mass percentage of the Ag nanoparticles relative to the total metal particles consisting of the Ag nanoparticles, the Sn microparticles, and the Ag microparticles is 50 wt% or more and 70 wt%, the mass percentage of the Sn microparticles relative to the total metal particles is 10 wt% or more and 20 wt%, and the mass percentage of the Ag microparticles relative to the total metal particles is the value obtained by subtracting the mass percentage of the Ag nanoparticles and the mass percentage of the Sn microparticles from 100 wt%.

2. A semiconductor device comprising: a bonding layer formed from a metal particle paste as described in claim 1; a semiconductor element in contact with the bonding layer; and a member to be bonded in contact with the bonding layer on the side opposite to the semiconductor element with respect to the bonding layer, wherein the bonding layer includes an AgSn-based intermetallic compound phase in contact with an Ag sintered body and a Sn phase in contact with the AgSn-based intermetallic compound phase.

3. A semiconductor device according to claim 2, wherein the volume fraction of the Ag sintered body relative to the bonding layer is 15% or more, and the volume fraction of the AgSn-based intermetallic compound phase relative to the bonding layer is 10% or more.

4. A method for manufacturing a semiconductor device, comprising the steps of: placing the metal particle paste described in claim 1 between a semiconductor device and a member to be bonded; heating the metal particle paste at a first temperature lower than the melting point of the Sn microparticles and at or above the sintering temperature of the Ag nanoparticles and Ag microparticles, thereby bonding the semiconductor device and the member to be bonded with a sintered body layer containing the sintered Ag nanoparticles and Ag microparticles; and melting the Sn microparticles at a second temperature at or above the melting point of the Sn microparticles into the gap between at least one of the semiconductor device, the sintered body layer, and the member to be bonded.

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