Semiconductor device manufacturing method, semiconductor device

Abstract

To provide a method for manufacturing a semiconductor device capable of improving reliability.SOLUTION: A method for manufacturing a semiconductor device including an insulating substrate 11 on which a semiconductor element is mounted, and a heat dissipation member 20 which has a flat plate-like portion 21 which is parallel to the plate surface of the insulating substrate 11 and is joined to the insulating substrate 11, and which dissipates heat generated by the semiconductor element 12 includes the steps of stacking the insulating substrate 11 and the heat dissipation member 20 with a metal paste interposed between the insulating substrate 11 and the flat portion 21 of the heat dissipation member 20, and sintering the metal paste while applying pressure to the insulating substrate 11 such that the surface pressure at the periphery of the insulating substrate 11 is higher than the surface pressure at the center of the insulating substrate 11.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a semiconductor device and a semiconductor device.

Background Art

[0002] For example, the semiconductor device described in Patent Document 1 includes a plurality of semiconductor elements, an insulating circuit board on which the plurality of semiconductor elements are mounted, and a heat dissipation substrate joined to the insulating circuit board via a joining layer. The joining layer has a plurality of first sintered metal layers located directly below the plurality of semiconductor elements, and a second sintered metal layer having a porosity larger than that of the first sintered metal layer and contacting the outer peripheral portion of the insulating circuit board and surrounding each of the plurality of first sintered metal layers.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Due to the difference in the linear expansion coefficients between the insulating substrate and the heat dissipation member, cracks or peeling may occur in the outer part of the sintered part (the joining layer in Patent Document 1) between the insulating substrate and the heat dissipation member, specifically, in the part on the insulating substrate side. When cracks or the like progress to the inner part of the sintered part and reach the heat dissipation path through which heat generated from the semiconductor element reaches the heat dissipation member, the heat performance deteriorates. As a result, the reliability of the semiconductor device decreases. An object of the present invention is to provide a method for manufacturing a semiconductor device and the like that can improve reliability.

Means for Solving the Problems

[0005] The present invention completed for such an object is a method for manufacturing a semiconductor device, comprising an insulating substrate on which a semiconductor element is mounted, and a heat dissipation member having a flat plate portion parallel to the plate surface of the insulating substrate and joined to the insulating substrate, for dissipating heat generated by the semiconductor element, the method including a step of laminating the insulating substrate and the heat dissipation member with a metal paste interposed therebetween, and a step of sintering the metal paste while pressing the insulating substrate so that the surface pressure of the outer peripheral portion of the insulating substrate is higher than the surface pressure of the central portion thereof. Here, the central portion of the insulating substrate may be circular with the center of the semiconductor element as the center. Also, the surface pressure of the outer peripheral portion of the insulating substrate may be set to 1.3 to 3.0 times the surface pressure of the central portion. From another aspect, the present invention provides a semiconductor device including an insulating substrate on which a semiconductor element is mounted, and a heat dissipation member having a flat plate portion parallel to the plate surface of the insulating substrate and joined to the insulating substrate, for dissipating heat generated by the semiconductor element, wherein the insulating substrate and the flat plate portion of the heat dissipation member are joined by sintering a metal paste, and the porosity of the sintered portion at the outer peripheral portion of the insulating substrate is smaller than the porosity of the sintered portion at the central portion of the insulating substrate. Here, the central portion of the insulating substrate may be circular with the semiconductor element as the center.

Advantages of the Invention

[0006] According to the present invention, it is possible to provide a method for manufacturing a semiconductor device and the like that can improve reliability.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of a schematic configuration of a semiconductor device 1 according to an embodiment. FIG. 2 is a diagram showing an example of a cross section obtained by cutting the semiconductor module 10 at the II-II portion of FIG. 1. The semiconductor device 1 according to the embodiment includes a semiconductor module 10, a heat dissipation member 20 that dissipates heat transmitted from the semiconductor module 10, and a heat dissipation member bonding layer 30 that bonds the semiconductor module 10 and the heat dissipation member 20.

[0009] In the semiconductor device 1, a heat radiating member 20 and a semiconductor module 10 are laminated. Hereinafter, the lamination direction of the heat radiating member 20 and the semiconductor module 10 may be simply referred to as the "lamination direction". Also, the side of the semiconductor module 10 in the lamination direction (the upper side in FIG. 1) may be referred to as the "first side", and the side of the heat radiating member 20 in the lamination direction (the lower side in FIG. 1) may be referred to as the "second side". Further, in the rectangular parallelepiped-shaped flat plate portion 21 of the heat radiating member 20 described later, the rectangular longitudinal direction orthogonal to the lamination direction may be simply referred to as the "longitudinal direction", and the rectangular short side direction may be simply referred to as the "short side direction".

[0010] Although not shown, the semiconductor device 1 is used, for example, by being attached to a case having an internal space through which a coolant flows such that fins 22 (described later) of the heat radiating member 20 contact the coolant. Thereby, the heat generated in the semiconductor module 10 and conducted to the heat radiating member 20 through the heat radiating member bonding layer 30 is radiated by the coolant. Alternatively, the semiconductor device 1 may be an air-cooled type in which the heat radiating member 20 is disposed in a space through which air flows.

[0011] (Semiconductor module 10) The semiconductor module 10 includes an insulating substrate 11, semiconductor elements 12 mounted on the surface of the first side of the insulating substrate 11, and an element bonding layer 15 that bonds the insulating substrate 11 and the semiconductor elements 12.

[0012] The insulating substrate 11 is an insulating heat radiating circuit substrate in which copper plates are bonded and integrated on both surfaces of a ceramics plate 111 that is an insulating material, and has a first copper plate 112 provided on the first side of the ceramics plate 111 and a second copper plate 113 provided on the second side of the ceramics plate 111. It can be exemplified that the bonding of the ceramics plate 111, the first copper plate 112, and the second copper plate 113 is performed using a direct bonding method (Direct Copper Bonding) or an active metal brazing method. It can be exemplified that the ceramics plate 111 is larger than the first copper plate 112 and the second copper plate 113 when viewed in the lamination direction, and the first copper plate 112 and the second copper plate 113 are of the same size.

[0013] The semiconductor element 12 is, for example, a power semiconductor such as a transistor, thyristor, diode, etc. used for power control. Examples of the material of the semiconductor element 12 can include silicon (Si), silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga2O3). In this embodiment, the semiconductor element 12 has a rectangular parallelepiped shape.

[0014] The thickness of the element bonding layer 15 can be exemplified in the range of 10 μm or more and 500 μm or less. The method of bonding the insulating substrate 11 and the semiconductor element 12 via the element bonding layer 15 is copper sintering, silver sintering, or gold sintering. It can be exemplified that the sintered body constituting the element bonding layer 15 is the same as the sintered body constituting the heat dissipation member bonding layer 30 described later. Note that in the semiconductor module 10, a lead frame may be bonded to the semiconductor element 12 via, for example, solder.

[0015] (Heat dissipation member 20) The heat dissipation member 20 includes a flat plate-shaped flat plate portion 21 and a plurality of fins 22 protruding from the flat plate portion 21. The flat plate portion 21 has a rectangular shape when viewed in the stacking direction. The flat plate portion 21 has a first surface 211 that is a surface facing the semiconductor module 10 via the heat dissipation member bonding layer 30, and a second surface 212 that is the surface on the side where the plurality of fins 22 protrude.

[0016] The fins 22 protrude from the second surface 212 of the flat plate portion 21 in a direction perpendicular to the plate surface of the flat plate portion 21. The fins 22 can be exemplified as being flat plate-shaped extending in the longitudinal direction. The fins 22 may be parallel to the longitudinal direction or may be wavy having a portion inclined in the longitudinal direction. The plurality of fins 22 are arranged side by side in the short side direction. Also, the fins 22 may be columnar with the protruding direction from the flat plate portion 21 being the stacking direction. And the shape of the fins 22 cut along a plane perpendicular to the protruding direction (hereinafter, may be referred to as "cross-sectional shape") can be exemplified as being a quadrilateral such as a square, rectangle, or rhombus. Also, the cross-sectional shape may be a circle or an ellipse.

[0017] The heat radiating member 20 is formed of at least one of copper or aluminum material. As the aluminum material, it is possible to exemplify the A1000 series of pure aluminum such as A1100. It can be exemplified that the heat radiating member 20 is manufactured by subjecting a metal mass as a raw material to at least one of cutting and forging. Alternatively, the heat radiating member 20 may be manufactured by extrusion, or may be manufactured by subjecting it to cutting after extrusion.

[0018] The heat radiating member bonding layer 30 bonds the second copper plate 113 of the insulating substrate 11 and the flat plate portion 21 of the heat radiating member 20. The heat radiating member bonding layer 30 is not particularly limited as long as it can transfer heat between the second copper plate 113 and the heat radiating member 20. The method of bonding the insulating substrate 11 and the heat radiating member 20 through the heat radiating member bonding layer 30 is copper sintering, silver sintering, or gold sintering.

[0019] The thickness of the heat radiating member bonding layer 30 can be exemplified in the range of 10 μm or more and 500 μm or less. When the thickness of the heat radiating member bonding layer 30 is less than 10 μm, the bonding strength between the insulating substrate 11 and the heat radiating member 20 by the heat radiating member bonding layer 30 may be insufficient. Further, when the thickness of the heat radiating member bonding layer 30 exceeds 500 μm, the heat transfer property from the semiconductor element 12 to the heat radiating member 20 through the heat radiating member bonding layer 30 is likely to decrease. In this case, there is a possibility that the heat dissipation efficiency of the heat generated in the semiconductor element 12 decreases. The thickness of the heat radiating member bonding layer 30 is preferably in the range of 50 μm or more and 200 μm or less, and more preferably in the range of 60 μm or more and 180 μm or less.

[0020] The sintered body constituting the heat radiating member bonding layer 30 is obtained, for example, by applying a metal paste in which metal particles are dispersed between the second copper plate 113 of the insulating substrate 11 and the heat radiating member 20 and sintering it. Examples of the method of sintering the metal paste to obtain a sintered body include pressureless sintering, pressure sintering, and electric current sintering.

[0021] The metal paste contains metal particles and a solvent for dispersing the metal particles. The metal paste may also contain additives other than the metal particles and the solvent. Examples of such additives include a surfactant, an antifoaming agent, and an ion trapping agent.

[0022] Examples of the metal particles include particles containing at least one metal selected from the group consisting of copper, silver, and gold. Alternatively, the metal particles may be copper particles whose surfaces are coated with silver. Among these, from the viewpoint of thermal conductivity between the semiconductor module 10 and the heat dissipation member 20 via the heat dissipation member bonding layer 30, it is preferable to use copper particles as the metal particles.

[0023] The average particle size (50% deposition average particle size) of the metal particles is, for example, in the range of 0.1 μm to 500 μm, preferably in the range of 1 μm to 200 μm, and more preferably in the range of 10 μm to 100 μm. The average particle size of the metal particles can be determined by a method in which the solvent is removed from the metal paste, the dried metal particles are dispersed using a known dispersant, and the dispersed metal particles are measured using a light scattering particle size distribution measuring device.

[0024] The shape of the metal particles is not particularly limited, and examples thereof include a sphere, a roughly spherical shape such as a spheroid, a lump, a needle, a flake, and an aggregate thereof. These shapes of the metal particles may be used alone or in combination. From the viewpoint of the dispersibility of the metal particles in the metal paste and the filling property of the metal particles in the heat dissipation member bonding layer 30, the shape of the metal particles is preferably a sphere, a roughly spherical shape, or a flake shape. The metal particles may be surface-treated with a known surface treatment agent.

[0025] As the solvent, a volatile solvent known as a solvent for metal pastes can be used. The content of the solvent in the metal paste can be, for example, in the range of 5 parts by mass or more and 50 parts by mass or less, assuming that the total mass of the metal particles is 100 parts by mass.

[0026] {Method for manufacturing semiconductor device 1} Next, a method for manufacturing semiconductor device 1 will be described. The method for manufacturing semiconductor device 1 includes a first coating step of applying a metal paste in which metal particles are dispersed on at least one of the heat dissipation member 20 and the insulating substrate 11, and a first lamination step of laminating the insulating substrate 11 and the heat dissipation member 20 via the metal paste. Further, the method for manufacturing semiconductor device 1 includes a second coating step of applying a metal paste in which metal particles are dispersed on at least one of the insulating substrate 11 and the semiconductor element 12, and a second lamination step of laminating the insulating substrate 11 and the semiconductor element 12 via the metal paste. Further, the method for manufacturing semiconductor device 1 includes a sintering step of sintering the metal paste between the heat dissipation member 20 and the insulating substrate 11 and the metal paste between the insulating substrate 11 and the semiconductor element 12 in a state where the heat dissipation member 20, the insulating substrate 11, and the semiconductor element 12 are laminated. Further, the method for manufacturing semiconductor device 1 may include a step of joining a lead frame to the semiconductor element 12 by metal bonding such as soldering or sintering after the sintering step.

[0027] Hereinafter, the coating step and the sintering step will be described in detail. FIG. 3 is a diagram for explaining an example of the method for manufacturing semiconductor device 1. (First coating step) In the first coating step, a first coating film layer 40 is formed by applying a metal paste on at least one of the second copper plate 113 of the insulating substrate 11 and the first surface 211 of the flat plate portion 21 of the heat dissipation member 20. FIG. 3(a) shows an example of forming a first coating film layer 40 by applying a metal paste on the first surface 211 of the flat plate portion 21 of the heat dissipation member 20. The method of applying the metal paste is not particularly limited, and examples thereof include screen printing, transfer printing, offset printing, inkjet printing, and printing methods using various dispensers and coaters. In the first coating step, a metal paste is applied to the first surface 211 of the flat plate portion 21 in a rectangular range having sides corresponding to the longitudinal direction and the short-side direction when viewed from the stacking direction, to form a first coating film layer 40. It can be exemplified that the rectangular range is substantially the same as the shape of the second copper plate 113 of the insulating substrate 11.

[0028] (First stacking step) In the first stacking step, the heat radiating member 20 and the insulating substrate 11 are stacked via the metal paste of the first coating film layer 40 formed in the first coating step. FIG. 3(b) shows an example in which the second copper plate 113 of the insulating substrate 11 is overlapped on the first coating film layer 40 formed on the first surface 211 of the flat plate portion 21 of the heat radiating member 20.

[0029] When the heat radiating member 20 and the insulating substrate 11 are stacked via the first coating film layer 40, the heat radiating member 20 and the insulating substrate 11 may be pressurized or may not be pressurized. The force applied to the heat radiating member 20 and the insulating substrate 11 varies depending on the viscosity of the metal paste used for the formation of the first coating film layer 40 and the like, but can be exemplified in the range of 0.01 MPa or less, preferably 0.005 MPa or less. Further, the method of applying the force is not particularly limited, and examples thereof include a method of placing a weight on the insulating substrate 11.

[0030] (Second coating step) In the second coating step, a metal paste is applied to at least one of the first copper plate 112 of the insulating substrate 11 and the surface on the second side of the semiconductor element 12 to form a second coating film layer 50. FIG. 3(c) shows an example in which a metal paste is applied to the first copper plate 112 of the insulating substrate 11 to form a second coating film layer 50. The method of applying the metal paste is not particularly limited, and examples thereof include screen printing, transfer printing, offset printing, inkjet printing, and printing methods using various dispensers and coaters.

[0031] In the second coating step, a metal paste is applied to the first copper plate 112 of the insulating substrate 11 in a rectangular range having sides corresponding to the longitudinal direction and the short-side direction when viewed from the lamination direction, thereby forming a second coating film layer 50. It can be exemplified that the rectangular range is substantially the same as the shape of the second side surface of the semiconductor element 12.

[0032] (Second lamination step) In the second lamination step, the insulating substrate 11 and the semiconductor element 12 are laminated via the metal paste of the second coating film layer 50 formed in the second coating step. Fig. 3(d) shows an example in which the semiconductor element 12 is stacked on the second coating film layer 50 formed on the first copper plate 112 of the insulating substrate 11.

[0033] When laminating the insulating substrate 11 and the semiconductor element 12 via the second coating film layer 50, the insulating substrate 11 and the semiconductor element 12 may be pressurized or may be unpressurized. The pressure applied to the insulating substrate 11 and the semiconductor element 12 varies depending on the viscosity of the metal paste used for forming the second coating film layer 50, etc., but ranges of 0.01 MPa or less, preferably 0.005 MPa or less can be exemplified. Further, the method of applying the force is not particularly limited, and examples include a method of placing a weight on the semiconductor element 12.

[0034] Fig. 4 is a diagram showing an example of the first region A1 and the second region A2. In this embodiment, when viewed in the stacking direction, the size of the second side surface of the semiconductor element 12 is smaller than the sizes of the first copper plate 112 and the second copper plate 113 of the insulating substrate 11, and the semiconductor element 12 is stacked at the center of the first copper plate 112 of the insulating substrate 11. Therefore, when viewed in the stacking direction, the first coating layer 40 is formed in the region where the second coating layer 50 is formed, and the first coating layer 40 is also formed around the region where the second coating layer 50 is formed. Hereinafter, when viewed in the stacking direction, the region where the second coating layer 50 is formed is referred to as the "first region A1", and the region excluding the region where the second coating layer 50 is formed among the regions where the first coating layer 40 is formed may be referred to as the "second region A2". When viewed in the stacking direction, the first region A1 exists at the center of the insulating substrate 11, and the second region A2 exists at the outer periphery of the insulating substrate 11.

[0035] (Sintering process) In the sintering process, the first coating layer 40 and the second coating layer 50 are heated while being pressurized to sinter the metal paste constituting the first coating layer 40 and the second coating layer 50, and a heat dissipation member bonding layer 30 for bonding the heat dissipation member 20 and the insulating substrate 11 and an element bonding layer 15 for bonding the insulating substrate 11 and the semiconductor element 12 are formed.

[0036] When heating the first coating layer 40 and the second coating layer 50 in the sintering process, the temperature varies depending on the type of metal particles contained in the metal paste, etc., but a range of 150°C or higher and 500°C or lower can be exemplified.

[0037] When pressurizing the first coating layer 40 and the second coating layer 50 in the sintering process, pressurize so that the surface pressure of the outer periphery is higher than the surface pressure of the central portion of the insulating substrate 11. For example, pressurize the insulating substrate 11 so that the surface pressure of the second region A2 is higher than that of the first region A1.

[0038] FIG. 5 is a diagram showing an example of a pressurizing jig 500 used in the sintering process. The pressurizing jig 500 includes a first jig 510 on which an object to be pressurized 400 (the semiconductor device 1 before the sintering process) is placed, a second jig 520 that pressurizes the object to be pressurized 400, and a buffer member 530 disposed between the second jig 520 and the object to be pressurized 400. The pressurizing jig 500 is pressurized by a pressurizing device 600 on the surface of the second jig 520 opposite to the object to be pressurized 400, and the second jig 520 pressurizes the object to be pressurized 400 via the buffer member 530.

[0039] The first jig 510 and the second jig 520 are rectangular parallelepiped members formed of metal and are larger than the size of the object to be pressurized 400 when viewed in the stacking direction.

[0040] The buffer member 530 is a member provided mainly to suppress variations in surface pressure within the pressurizing surface and is formed of, for example, a rubber material, a carbon sheet, or the like. The buffer member 530 has a first buffer member 531 disposed between the semiconductor element 12 and the second jig 520, and a second buffer member 532 disposed around the first buffer member 531 between the insulating substrate 11 and the second jig 520. When viewed in the stacking direction, the first buffer member 531 is provided to transmit the pressing force from the pressurizing device 600 to the first region A1 of the insulating substrate 11, and the second buffer member 532 is provided to transmit the pressing force from the pressurizing device 600 to the second region A2 of the insulating substrate 11.

[0041] FIG. 6 is a diagram showing an example of the state of the first buffer member 531 and the second buffer member 532 before placing the second jig 520 on the first buffer member 531 and the second buffer member 532. As shown in FIG. 6, before being pressurized by the pressurizing device 600, the size of the first buffer member 531 and the second buffer member 532 in the stacking direction is set such that the surface on the first side of the second buffer member 532 protrudes more to the first side than the surface on the first side of the first buffer member 531.

[0042] According to the pressing jig 500 configured as described above, when it is pressed by the pressing device 600 via the second jig 520, the elastic deformation amount of the second buffer member 532 in the stacking direction is larger than the elastic deformation amount of the first buffer member 531 in the stacking direction. Therefore, the surface pressure of the outer peripheral portion is higher than the surface pressure of the central portion of the insulating substrate 11.

[0043] As described above, the manufacturing method of the semiconductor device 1 includes a joining method of joining an insulating substrate 11 on which a semiconductor element 12 is mounted and a heat dissipation member 20 having a flat plate portion 21 that is parallel to the plate surface of the insulating substrate 11 and is joined to the insulating substrate 11 and that dissipates heat generated by the semiconductor element 12. This joining method includes a step of laminating the insulating substrate 11 and the heat dissipation member 20 with a metal paste interposed therebetween (for example, the first lamination step), and a step of sintering the metal paste while pressing the insulating substrate 11 so that the surface pressure of the outer peripheral portion (for example, the second region A2) is higher than the surface pressure of the central portion (for example, the first region A1) of the insulating substrate 11.

[0044] In the semiconductor device 1 manufactured by this manufacturing method, the sintered state of the outer peripheral portion in the heat dissipation member joining layer 30 becomes denser than that of the central portion. In other words, the porosity of the outer peripheral portion in the heat dissipation member joining layer 30 becomes smaller than the porosity of the central portion. Therefore, the joining strength of the outer peripheral portion of the heat dissipation member joining layer 30 becomes higher than the joining strength of the central portion. As a comparative example, considering a method in which the surface pressures of the outer peripheral portion and the central portion are the same and the surface pressures of the outer peripheral portion and the central portion are the same as the surface pressure of the central portion described above, the joining strength of the outer peripheral portion in the semiconductor device 1 is higher than the joining strengths of the outer peripheral portion and the central portion joined by the method according to the comparative example. Therefore, even if the outer peripheral portion in the flat plate portion 21 of the heat dissipation member 20 is bent so as to be located more on the second side than the central portion, cracks and peeling in the outer peripheral portion of the heat dissipation member joining layer 30 are suppressed from occurring.

[0045] Here, if cracks or the like occur in the outer peripheral portion of the heat radiating member bonding layer 30, due to the semiconductor device 1 being used over a long period of time, there is a risk that the cracks or the like will progress toward the central portion where the heat dissipation path from the semiconductor element 12 to the heat radiating member 20 is formed, resulting in deterioration of the thermal performance. However, in the semiconductor device 1 manufactured by the above manufacturing method, cracks or the like are less likely to occur in the outer peripheral portion of the heat radiating member bonding layer 30, so the thermal performance is less likely to deteriorate even when used over a long period of time. Therefore, according to the manufacturing method of the semiconductor device 1, the reliability of the semiconductor device 1 can be improved.

[0046] Also, according to the manufacturing method of the semiconductor device 1, for example, it is possible to increase only the surface pressure of the outer peripheral portion while keeping the surface pressure of the central portion the same as before. A higher surface pressure in the sintering process improves the thermal conductivity in the heat radiating member bonding layer 30, but when the thermal conductivity exceeds, for example, 150 (W / m·K), it is difficult for the thermal resistance to decrease even if the thermal conductivity increases. Also, when the force for pressing the semiconductor element 12 becomes large, the semiconductor element 12 is likely to break. The manufacturing method of the semiconductor device 1 described above is a method devised in view of the above matters, and according to the manufacturing method of the semiconductor device 1, it is possible to increase the bonding strength only in the part that truly contributes to the thermal performance and reliability of the semiconductor device 1.

[0047] In the manufacturing method of the semiconductor device 1 described above, it is preferable that the surface pressure of the outer peripheral portion of the insulating substrate 11 is 1.3 to 3.0 times the surface pressure of the central portion. If the surface pressure of the outer peripheral portion is less than 1.3 times the surface pressure of the central portion, the difference in the bonding strength between the outer peripheral portion and the central portion is small, so the above-described effect of increasing the reliability is small. On the other hand, if the surface pressure of the outer peripheral portion exceeds 3.0 times the surface pressure of the central portion, there is a risk that the outer peripheral portion of the insulating substrate 11 will break. Also, when the magnitude of the surface pressure of the central portion is the same as the conventional surface pressure, the surface pressure of the outer peripheral portion becomes a value exceeding 3.0 times the conventional surface pressure, and a force exceeding 3.0 times the conventional pressing force is required as the pressing force of the pressing device 600. As a result, there is a risk that the equipment cost of the pressing device 600 will increase. By setting the surface pressure of the outer peripheral portion to 1.3 to 3.0 times the surface pressure of the central portion, it is possible to increase the reliability of the semiconductor device 1 while suppressing the breakage of the insulating substrate 11 and the increase in equipment cost.

[0048] Further, in the semiconductor device 1 described above, the porosity of the heat dissipation member bonding layer 30 as an example of the sintered portion on the outer peripheral portion of the insulating substrate 11 is smaller than the porosity of the heat dissipation member bonding layer 30 at the central portion of the insulating substrate 11. Since the porosity in the outer peripheral portion is smaller than that in the central portion, the bonding strength and the material strength in the outer peripheral portion are higher than those in the central portion. As a result, the reliability of the semiconductor device 1 is improved as compared with the case where the semiconductor device 1 is pressurized so as to have a uniform surface pressure between the central portion and the outer peripheral portion.

[0049] (Modification example of the buffer member 530) FIG. 7 is a view of an example of a modification of the buffer member 530 as viewed in the stacking direction. In the above-described embodiment, at least one of the first buffer member 531 and the second buffer member 532 may be divided without being integrally formed. FIG. 7 shows an example of the divided second buffer member 532. As shown in FIG. 7, the second buffer member 532 is provided at both ends in the short side direction, and includes two long members 541 arranged over the entire longitudinal direction of the insulating substrate 11, and two short members 542 provided at both ends in the longitudinal direction of the insulating substrate 11 so as to fill the gap between the two long members 541. It may be divided into a total of four members.

[0050] (Modification example of the method for making the surface pressure different) The method of making the surface pressure of the outer peripheral portion higher than the surface pressure of the central portion of the insulating substrate 11 described with reference to FIGS. 5 and 6 is a method of making the elastic deformation amount of the buffer member 130 deformed by being pressurized by the pressurizing device 600 different between the central portion and the outer peripheral portion, but is not particularly limited to this method.

[0051] FIG. 8 is a view showing an example of a modification of the method for making the surface pressure different. As shown in FIG. 8, the surface pressure may be made different between the central portion and the outer peripheral portion of the insulating substrate 11 by making the pressing force by the pressing device 600 different between the central portion and the outer peripheral portion of the insulating substrate 11. That is, the pressing device 600 has a plurality of pressing members 610 capable of pressing different regions at equal intervals, and the pressing force of the outer peripheral pressing member 612 provided at a position corresponding to the outer peripheral portion of the insulating substrate 11 is made larger than the pressing force of the central pressing member 611 provided at a position corresponding to the central portion of the insulating substrate 11 among the plurality of pressing members 610, whereby the surface pressure may be made different.

[0052] The pressing member 610 can be exemplified as a member having a coil spring and pressing using the spring force of the coil spring. When the pressing member 610 has a coil spring, for example, by making the spring constant of the coil spring of the outer peripheral pressing member 612 larger than the spring constant of the coil spring of the central pressing member 611, even if the coil spring of the central pressing member 611 and the coil spring of the outer peripheral pressing member 612 are compressed by the same amount, the pressing force of the outer peripheral pressing member 612 can be made larger than the pressing force of the central pressing member 611. Alternatively, for example, by making the spring constants of the coil springs of the central pressing member 611 and the outer peripheral pressing member 612 the same and making the compression amount of the coil spring of the outer peripheral pressing member 612 larger than the compression amount of the coil spring of the central pressing member 611, the pressing force of the outer peripheral pressing member 612 may be made larger than the pressing force of the central pressing member 611.

[0053] Further, the pressing member 610 can be exemplified as a member having a cylinder and pressing using the pressure of a fluid (for example, oil, air) in the cylinder. When the pressing member 610 has such a configuration, it is possible to make the pressing force of the outer peripheral pressing member 612 larger than the pressing force of the central pressing member 611 by changing the pressure of the fluid supplied into the cylinder.

[0054] In addition, when making the pressing force by the pressing device 600 different between the central portion and the outer peripheral portion of the insulating substrate 11, as described with reference to FIG. 6, the elastic deformation amount in the stacking direction of the second buffer member 532 may be made larger than the elastic deformation amount in the stacking direction of the first buffer member 531, or the elastic deformation amount of the first buffer member 531 and the elastic deformation amount of the second buffer member 532 may be made the same.

[0055] (Deformation example of the region where the surface pressure is different) The first region A1 described with reference to FIG. 4 is rectangular, and the surface pressure in the second region A2 around the first region A1 is made higher than the surface pressure in the rectangular first region A1, but the first region A1 is not limited to a rectangular shape.

[0056] FIG. 9 is a diagram showing an example of the first region A11 and the second region A21 according to the first modification. As shown in FIG. 9, the first region A11 according to the first modification may be circular with the center C1 of the semiconductor element 12 as the center and may include the region where the semiconductor element 12 is provided when viewed in the stacking direction. Since the first region A11 has the shape shown in FIG. 9, it is possible to highly accurately suppress the destruction of the semiconductor element 12 due to the pressing by the pressing device 600 during the sintering process.

[0057] FIG. 10 is a diagram showing an example of the first region A12 and the second region A22 according to the second modification. The first region A12 according to the second modification is an example of a region when a plurality of rectangular semiconductor elements 12 are joined to the insulating substrate 11. The first region A12 according to the second modification may be circular with the center C2 of the plurality of semiconductor elements 12 as the center and may include the region where the plurality of semiconductor elements 12 are provided when viewed in the stacking direction, as shown in FIG. 10. Since the first region A12 has the shape shown in FIG. 10, it is possible to highly accurately suppress the destruction of the plurality of semiconductor elements 12 due to the pressing by the pressing device 600 during the sintering process.

[0058] Note that even if the first region A1 and the second region A2 are the first region A11 and the second region A21 according to the first modification example, or the first region A12 and the second region A22 according to the second modification example, at least one of the first buffer member 531 or the second buffer member 532 may be divided without being integrally formed.

[0059] <Second Embodiment> FIG. 11 is a diagram for explaining an example of a method for manufacturing the semiconductor device 2 according to the second embodiment. The semiconductor device 2 according to the second embodiment is different from the semiconductor device 1 according to the first embodiment in that the semiconductor module 210 corresponding to the semiconductor module 10 is different. Hereinafter, the differences from the first embodiment will be described. The same components in the first embodiment and the second embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted. The semiconductor module 210 according to the second embodiment includes an insulating substrate 11, a semiconductor element 12, an element bonding layer 15, and a sealing resin portion 250 that covers the periphery of the insulating substrate 11, the semiconductor element 12, and the element bonding layer 15.

[0060] {Method for Manufacturing Semiconductor Device 2} The method for manufacturing the semiconductor device 2 includes a manufacturing process for manufacturing the semiconductor module 210, an application process for applying a metal paste to at least one of the semiconductor module 210 and the heat dissipation member 20, a lamination process for laminating the semiconductor module 210 and the heat dissipation member 20 via the metal paste, and a sintering process for sintering the metal paste between the semiconductor module 210 and the heat dissipation member 20.

[0061] The manufacturing process can be exemplified by molding the sealing resin portion 250 with a thermosetting resin after joining the insulating substrate 11 and the semiconductor element 12. Further, the manufacturing process may include a process of joining a lead frame to the semiconductor element 12 by metal bonding such as soldering or sintering after joining the insulating substrate 11 and the semiconductor element 12.

[0062] In the coating step, in the same manner as in the above-described first coating step, a metal paste is applied to at least one of the surfaces of the second copper plate 113 of the insulating substrate 11 and the first surface 211 of the flat plate portion 21 of the heat dissipation member 20 to form a first coating film layer 40. In the lamination step, as shown in FIG. 11(a), the heat dissipation member 20 and the semiconductor module 210 are laminated via the metal paste of the first coating film layer 40 formed by the coating step.

[0063] In the sintering step, as shown in FIG. 11(b), the first coating film layer 40 is heated while being pressurized to sinter the metal paste constituting the first coating film layer 40, and a heat dissipation member bonding layer 30 for bonding the heat dissipation member 20 and the semiconductor module 210 is formed. When pressurizing the first coating film layer 40 in the sintering step, the pressurizing jig 500 and the pressurizing device 600 are used to pressurize the outer peripheral portion so that the surface pressure of the outer peripheral portion is higher than the surface pressure of the central portion of the insulating substrate 11.

[0064] In the semiconductor device 2 manufactured by this manufacturing method, since the sintering state of the outer peripheral portion in the heat dissipation member bonding layer 30 is denser than that of the central portion, the bonding strength of the outer peripheral portion of the heat dissipation member bonding layer 30 is higher than that of the central portion. As a result, the occurrence of cracks and peeling in the outer peripheral portion of the heat dissipation member bonding layer 30 is suppressed, so the reliability of the semiconductor device 2 is improved. Further, according to the manufacturing method of the semiconductor device 2 described above, the bonding strength can be increased only for the portions that truly contribute to the thermal performance and reliability of the semiconductor device 2.

Description of Reference Numerals

[0065] 1, 2... semiconductor device, 10, 210... semiconductor module, 11... insulating substrate, 12... semiconductor element, 15... element bonding layer, 20... heat dissipation member, 21... flat plate portion, 22... fin, 30... heat dissipation member bonding layer, 40... first coating film layer, 50... second coating film layer, 111... ceramic plate, 112... first copper plate, 113... second copper plate, A1... first region, A2... second region

Claims

1. An insulating substrate on which a semiconductor element is mounted, A heat radiating member having a flat plate portion that is parallel to the surface of the insulating substrate and is joined to the insulating substrate, and that dissipates heat generated by the semiconductor element, A method for manufacturing a semiconductor device having, A step of laminating the insulating substrate and the heat radiating member with a metal paste interposed therebetween, A step of sintering the metal paste while pressing the insulating substrate so that the surface pressure of the outer peripheral portion is higher than the surface pressure of the central portion of the insulating substrate, A method for manufacturing a semiconductor device comprising.

2. The central portion of the insulating substrate is circular with the center of the semiconductor element as the center, The method for manufacturing a semiconductor device according to Claim 1.

3. The surface pressure of the outer peripheral portion of the insulating substrate is 1.3 to 3.0 times the surface pressure of the central portion, The method for manufacturing a semiconductor device according to Claim 1.

4. An insulating substrate on which a semiconductor element is mounted, A heat radiating member having a flat plate portion that is parallel to the surface of the insulating substrate and is joined to the insulating substrate, and that dissipates heat generated by the semiconductor element, Comprising, The insulating substrate and the flat plate portion of the heat radiating member are joined by sintering a metal paste, and the porosity of the sintered portion in the outer peripheral portion of the insulating substrate is smaller than the porosity of the sintered portion in the central portion of the insulating substrate, A semiconductor device.

5. The central portion of the insulating substrate is circular with the semiconductor element as the center, The semiconductor device according to Claim 4.

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