Semiconductor device and method of manufacturing the same

Abstract

To provide a semiconductor device and a manufacturing method of the semiconductor device capable of reducing a difference in cooling performance and suppressing variations in thermal resistance by making a clearance between a heat radiation fin and a water jacket constant.SOLUTION: A laminated substrate 5 on which a semiconductor element 1 is mounted via a first joining layer 25a, a metallic base 26 which is joined to the laminated substrate 5 via a second joining layer 25a having a composition and a material which are the same as or different from those of the first joining layer 25b and has a plurality of heat radiation fins 28; The plurality of heat radiation fins 28 are formed so as to become longer from the end portion of the metal base 26 toward the central portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor device and a method for manufacturing the same. [Background technology]

[0002] Conventionally, cooling devices for electronic components have been proposed in which the length of the heat dissipation fins is longest at the center of the power device and gradually shortens toward both ends, thereby reducing pressure loss of the cooling fluid and maintaining the desired cooling performance even when the semiconductor device is miniaturized (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-008264 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional semiconductor devices, tightening the water jacket (WJ) or other means causes the semiconductor module to deform into a convex shape, which results in differences in the gap (clearance) between the water jacket and the heat dissipation fins (tips) at the center and ends of the semiconductor module, resulting in differences in cooling performance and resulting in variations in thermal resistance.

[0005] The present disclosure aims to provide a semiconductor device and a method for manufacturing a semiconductor device that can reduce differences in cooling performance and suppress variations in thermal resistance by stabilizing the clearance between the heat dissipation fins and the water jacket in order to resolve the problems associated with the conventional technology described above. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object of the present disclosure, the semiconductor device according to the present disclosure has the following features: The semiconductor device includes a laminated substrate on which a semiconductor element is mounted via a first bonding layer, a metal base having a plurality of heat dissipation fins bonded to the laminated substrate via a second bonding layer of the same or different composition or material as the first bonding layer, and a water jacket bonded to the metal base. The plurality of heat dissipation fins are formed so that they become longer from the end portion of the metal base toward the center portion.

[0007] According to the disclosure above, the clearance is constant regardless of the location of the power semiconductor chip in the semiconductor device. This results in no difference in cooling performance between the heat dissipation fins and the water jacket at the center and edges of the semiconductor device, eliminating variations in thermal resistance and improving the reliability of the semiconductor device. [Effects of the Invention]

[0008] According to the semiconductor device and the method for manufacturing the semiconductor device disclosed herein, by making the clearance between the heat dissipation fins and the water jacket constant, it is possible to reduce differences in cooling performance and suppress variations in thermal resistance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a structure of a semiconductor module according to an embodiment; [Figure 2] 1 is a cross-sectional view showing a warped state of a semiconductor module according to an embodiment; [Figure 3] 10 is a cross-sectional view showing a state after fastening the water jacket of the semiconductor device according to the embodiment. FIG. [Figure 4] 10 is an enlarged cross-sectional view of a heat dissipation fin of the semiconductor device according to the embodiment after fastening the water jacket; FIG. [Figure 5] 10 is a graph showing an evaluation of the variation in thermal resistance of a metal base according to an embodiment. [Figure 6]FIG. 10 is a top view showing the measurement positions of the thermal resistance variation of the metal base according to the embodiment. [Figure 7] FIG. 1 is a cross-sectional view showing the structure of a conventional semiconductor module. [Figure 8] FIG. 10 is a cross-sectional view showing a warped state of a conventional semiconductor module. [Figure 9] FIG. 10 is a cross-sectional view showing a state before fastening a water jacket of a conventional semiconductor device. [Figure 10] FIG. 10 is a cross-sectional view showing a state after fastening the water jacket of the conventional semiconductor device. [Figure 11] FIG. 10 is an enlarged cross-sectional view of a heat dissipation fin in a state after fastening a water jacket of a conventional semiconductor device. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Summary of Embodiments of the Present Disclosure> In order to solve the above-mentioned problems and achieve the object of the present disclosure, the semiconductor device according to the present disclosure has the following features: The semiconductor device includes a laminated substrate on which a semiconductor element is mounted via a first bonding layer, a metal base having a plurality of heat dissipation fins bonded to the laminated substrate via a second bonding layer of the same or different composition or material as the first bonding layer, and a water jacket bonded to the metal base. The plurality of heat dissipation fins are formed so that they become longer from the end portion toward the center portion of the metal base.

[0011] According to the disclosure above, the clearance is constant regardless of the location of the power semiconductor chip in the semiconductor device, so there is no difference in cooling performance between the heat dissipation fins and the water jacket at the center and edges of the semiconductor device, so there is no variation in thermal resistance and the reliability of the semiconductor device can be improved.

[0012] Further, in the semiconductor device according to the present disclosure, the metal base is convex toward the semiconductor element.

[0013] Furthermore, in the semiconductor device according to the present disclosure, the amount of warping of the metal base is 0.1 mm or more.

[0014] Furthermore, in the semiconductor device according to the present disclosure, a clearance between the tips of the plurality of heat dissipation fins and the bottom surface of the water jacket is smaller than 0.2 mm.

[0015] Furthermore, in the semiconductor device according to the present disclosure, a clearance between the tips of the plurality of heat dissipation fins and the bottom surface of the water jacket is less than 0.1 mm.

[0016] Furthermore, in the semiconductor device according to the present disclosure, the maximum thermal resistance variation of the metal base is 1.1 or less.

[0017] Furthermore, in the semiconductor device according to the present disclosure, the maximum thermal resistance variation of the metal base is 1.06 or less.

[0018] In order to solve the above-mentioned problems and achieve the object of the present disclosure, the method for manufacturing a semiconductor device according to the present disclosure has the following features. First, a first step is performed in which a semiconductor element is mounted on a laminated substrate via a first bonding layer. Next, a second step is performed in which a metal base having multiple heat dissipation fins is bonded to the laminated substrate via a second bonding layer of the same or different composition or material as the first bonding layer. Next, a third step is performed in which a water jacket is bonded to the metal base. Prior to the second step, the method includes an adjustment step in which the amount of warping of the metal base is measured and the lengths of the multiple heat dissipation fins are adjusted to increase from the ends of the metal base toward the center according to the amount of warping.

[0019] In addition, the manufacturing method of a semiconductor device according to the present disclosure is characterized in that, in the above disclosure, the adjustment process includes joining a test water jacket to the metal base, measuring the distance from the bottom of the test water jacket to the tip of the heat dissipation fin, or the distance from the bottom of the test water jacket to the back surface of the metal base, and adjusting the length of the heat dissipation fin so that the distance remains constant.

[0020] Furthermore, in the manufacturing method of a semiconductor device according to the present disclosure, in the above disclosure, the adjustment process is characterized in that, when the length of the most endmost fin among the plurality of fins is L(0), the distance from the bottom surface of the test water jacket to the tip of the fin is C(x), and the distance from the most endmost fin among the plurality of fins and the bottom surface of the test water jacket to the tip of the fin is C(0), the length L(x) of the fin at each position x is adjusted so that L(x) = L(0) + (C(x) - C(0)).

[0021] <Findings underlying this disclosure> First, we will explain the problems with conventional semiconductor devices. FIG. 7 is a cross-sectional view showing the structure of a conventional semiconductor module. As shown in FIG. 7, a semiconductor module 150 includes a power semiconductor chip 101, a laminated substrate 105, a case 107, a metal base 126, metal terminals 109, and metal wires 110. The power semiconductor chip 101 is a power semiconductor chip such as a MOSFET, an IGBT, or a diode, and is bonded to the laminated substrate 105 with a bonding layer 125 such as solder. The laminated substrate 105 includes an insulating substrate 102 such as a ceramic substrate, a first conductive plate 103 made of copper or the like on its front surface, and a second conductive plate 104 made of copper or the like on its back surface. The laminated substrate 105 is bonded to the metal base 126 with the bonding layer 125 such as solder. The metal terminals 109, which output signals to the outside, are arranged to pass through the inside of the case 107 and be exposed to the inside of the case. The metal wires 110 electrically connect the power semiconductor chip 101 and the metal terminals 109. In the case of a MOSFET, a source electrode pad is formed on the surface of the power semiconductor chip 101 as a power terminal electrode pad (current supply terminal). A conductive connection member such as a metal wire 110 or a lead frame is then arranged from the power terminal electrode pad as an output terminal. In the case of a lead frame, it is joined to the power semiconductor chip 101 by a bonding layer 125 such as solder. Although not shown, a plurality of these members are mounted on one semiconductor module. A case 107 is bonded to the semiconductor module 150, and a lid (not shown) is attached, through which metal terminals 109 pass and protrude to the outside. The case 107 is filled with sealing resin (sealant) 108 that insulates and protects the laminated substrate 105 and the power semiconductor chip 101 on the substrate.

[0022] A plurality of heat dissipation fins 128 are provided on the back surface of the metal base 126. The metal base 126 conducts heat generated in the power semiconductor chip 101 and transmitted via the laminated substrate 105 to the heat dissipation fins 128. The heat dissipation fins 128 dissipate the heat conducted from the metal base 126 via a refrigerant or the like.

[0023] Because the metal base 126 of the semiconductor module 150 is open, it is not possible to run a coolant through it alone. For this reason, the semiconductor module 150 is attached to a separate water jacket 129 (see Figures 9 and 10) to allow the coolant to flow through it during cooling. The power semiconductor chip 101 of the semiconductor module 150 generates heat when it is operating. For this reason, by running the semiconductor module 150 while cooling it with a coolant, heat generation by the power semiconductor chip 101 is suppressed, allowing it to operate within the chip's guaranteed temperature range. Thermal resistance during cooling varies depending on the cooling capacity, and the heat dissipation fins 128 of the metal base 126 reduce the clearance with the water jacket 129, and by arranging the heat dissipation fins 128 in all flow paths, cooling performance is improved.

[0024] Fig. 8 is a cross-sectional view showing a warped state of a conventional semiconductor module. As shown in Fig. 8, when a joining process such as soldering involving heat is performed on a laminated substrate 105 carrying power semiconductor chips 101, metal wires 110, etc., and a metal base 126, the laminated substrate 105 warps together with the metal base 126 due to the difference in linear expansion coefficient, and the semiconductor module 150 also warps, becoming convex downward.

[0025] Figure 9 is a cross-sectional view showing a conventional semiconductor device before the water jacket is fastened. Here, the semiconductor device refers to a device having a semiconductor module and a water jacket. In Figure 9 and the following Figure 10, the structure above the metal base 126 is omitted. The semiconductor module 150 is fastened to the water jacket 129 with a fastening screw 131 via a sealing material such as an O-ring 130 or a gasket.

[0026] 10 is a cross-sectional view showing the state of a conventional semiconductor device after the water jacket is fastened. Because the water jacket 129 is fastened by screws at four points, the reaction force and internal pressure of the O-ring 130 and gasket cause the center of the semiconductor module 150 to deform into an upwardly convex shape. Even if a warped semiconductor module 150 is fastened to the water jacket 129, the warp is not corrected and the module warps in the opposite direction. Note that the "upwardly convex" mentioned above refers to a convex warp with the upper side bulging out, with the power semiconductor chip 101 side facing upward, and the "opposite direction" refers to a "downwardly convex" shape.

[0027] 11 is an enlarged cross-sectional view of the heat dissipation fins of a conventional semiconductor device after the water jacket is fastened. As shown in FIG. 11, because the center of the semiconductor module 150 is convex upward, the gap (clearance) between the tip of the heat dissipation fin 128 and the bottom of the water jacket 129 (bottom surface: inner surface of the bottom plate) is wider in the center, resulting in in-plane variations in cooling efficiency (thermal resistance) between the edge and center. In-plane variations in cooling efficiency (thermal resistance) occur between the center and edge of the semiconductor module 150, resulting in differences in cooling performance, and therefore variations in the thermal resistance of the metal base 126 (the value is higher in the center). Because the power semiconductor chips 101, which are heat sources, are arranged at the edge or in multiple locations, it is necessary to suppress in-plane variations.

[0028] For example, when the longitudinal length of the metal base 126 is 130 mm, if the difference in clearance between the end and center is 0.1 mm or more, the variation in thermal resistance Rth (ΔRth) will increase, and if it is 0.2 mm, ΔRth will increase by about 10%.

[0029] As described above, in conventional semiconductor devices, when the semiconductor module 150 is fastened to the water jacket 129, it deforms into an upward convex shape, which causes a difference in the clearance between the water jacket 129 and the heat dissipation fins 128 at the center and ends of the semiconductor module 150, resulting in a difference in cooling performance and resulting in variations in the thermal resistance of the metal base 126.

[0030] Preferred embodiments of a semiconductor device and a method for manufacturing a semiconductor device according to the present disclosure will be described in detail below with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments described below.

[0031] (Embodiment) FIG. 1 is a cross-sectional view showing the structure of a semiconductor module according to an embodiment. In the semiconductor module 50, a first conductive plate 3 made of copper is disposed on one surface (front side) of an insulating substrate 2, and a second conductive plate 4 made of copper or the like is disposed on the other surface (back side) to form a laminated substrate 5. A plurality of power semiconductor chips 1 are mounted on the front surface of the first conductive plate 3 of the laminated substrate 5 via a first bonding layer 25a made of solder or the like. Metal terminals 9 for outputting signals to the outside are disposed so as to pass through the inside of the case 7 and be exposed to the inside of the case. Furthermore, a conductive connecting member such as a pin-type terminal or a lead frame is attached to the front surface (e.g., source electrode pad) of the power semiconductor chip 1 via a metal wire 10 (bonding wire) such as aluminum wire or a bonding layer (not shown). The power semiconductor chip 1 and the metal terminal 9 are electrically connected via the metal wire 10 such as aluminum wire. A lead frame (not shown) may also be used. A primer layer (not shown) may be laminated on the sealed components, such as the power semiconductor chip 1, the laminated substrate 5, the first bonding layer 25a, and the metal wires 10 (conductive connecting members), to improve adhesion. The interior of the case 7 is filled with a sealing resin 8. The illustrated configuration of the semiconductor module 50 is merely an example, and the present invention is not limited to this configuration. Depending on the components, the semiconductor module may be substantially rectangular or square in top view, with substantially rectangular modules being more commonly used. In the case of a substantially rectangular module having long and short sides, the central portion may be the central portion in the direction parallel to the long sides or the central portion in the direction parallel to the short sides.

[0032] (Power semiconductor chip 1) The power semiconductor chip 1 is a power chip such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), or an SBD (Schottky Barrier Diode), and devices using Si, SiC, or GaN can be used as the semiconductor substrate. The present disclosure is particularly effective for SiC chips and GaN chips that have high power and a high Young's modulus. The number of power semiconductor chips 1 mounted may be one or more.

[0033] An electrode on the back surface (back surface electrode) of the power semiconductor chip 1 is joined to a first conductive plate 3 on the front surface of the laminated substrate 5 with a first bonding layer 25a such as solder. A second conductive plate 4 on the back surface of the laminated substrate 5 is joined to the front surface of a metal base 26 with a second bonding layer 25b such as solder. The first conductive plate 3 is formed in a predetermined circuit pattern on the front surface (first main surface) of the insulating substrate 2. The second conductive plate 4 may be a metal foil formed on the entire back surface of the insulating substrate 2.

[0034] (Laminated substrate 5) The laminated substrate 5 can be composed of an insulating substrate 2, a first conductive plate 3 formed in a predetermined shape on one of its main surfaces, and a second conductive plate 4 formed on the other main surface. The insulating substrate 2 can be made of a material with excellent electrical insulation and thermal conductivity. Examples of materials for the insulating substrate 2 include ceramics such as Al2O3, AlN, and SiN. For high-voltage applications, a material that combines electrical insulation and thermal conductivity is preferable, and AlN and SiN can be used, but are not limited to these. Resin insulating substrates made of epoxy resins containing highly thermally conductive particles such as boron nitride can also be used. The first conductive plate 3 and the second conductive plate 4 can be made of Cu (copper) or a Cu alloy, which are easy to process. A Cu alloy is an alloy containing 80% or more Cu. Among such conductive plates made of Cu or a Cu alloy, the conductive plate (second conductive plate) not in contact with the power semiconductor chip 1 is sometimes referred to as a back copper foil or back conductive plate. Direct copper bonding or active metal brazing can be used as a method for disposing a conductive plate on the insulating substrate 2. Alternatively, the surface of the conductive substrate may be plated with Ni (nickel) or the like to form a Ni or Ni alloy layer.

[0035] (Metal base 26) The metal base 26 is a heat sink having, for example, a substantially rectangular planar shape and made of a metal such as Cu or Al that has excellent thermal conductivity, and is also referred to as a metal substrate. The surface of the metal base 26 may be covered with a Ni film or Ni alloy film that has an anti-corrosion effect. A plurality of heat dissipation fins 28 are provided on the back surface of the metal base 26. The metal base 26 conducts heat generated in the power semiconductor chip 1 and transmitted via the laminated substrate 5 to the heat dissipation fins 28. The heat dissipation fins 28 dissipate the heat conducted from the metal base 26. A cooler (metal base 26) having heat dissipation fins 28 may be attached to the plate-shaped metal base.

[0036] (First bonding layer 25a, second bonding layer 25b) The first bonding layer 25a and the second bonding layer 25b can be formed using lead-free solder. Examples of suitable materials include, but are not limited to, Sn-Sb, Sn-Cu, Sn-Ag, and Sn-Sb-Ag solders. Sintered materials using nanometal particles such as silver or copper are also suitable. Furthermore, the first bonding layer 25a between the semiconductor element and the first conductive plate of the laminated substrate and the second bonding layer 25b between the second conductive plate and the metal base may be made of different compositions and materials.

[0037] (Case 7) The lower end of a case 7 made of resin or the like is adhered to the periphery of the metal base 26. The case 7 has a generally rectangular cylindrical shape and surrounds the periphery of the front surface of the metal base 26. A box-shaped recess is formed, with the front surface of the metal base 26 as its bottom and the inner wall of the case 7 perpendicular to the front surface of the metal base 26 as its side wall. The power semiconductor chip 1, which is wired with wiring members such as metal wires 10 and lead frames, as well as the laminated substrate 5 and wiring member components are housed inside this recess. The material of the case 7 may be, for example, a thermoplastic resin such as polyphenylene sulfide (PPS) or polybutylene terephthalate (PBT) or a thermosetting resin such as a phenolic resin. Alternatively, the semiconductor module 50 may be formed by molding the power semiconductor chip 1, the laminated substrate 5, etc. with a sealing resin 8 without including a case.

[0038] (Primer layer) A primer layer (not shown) may be formed on the member to be sealed. The primer layer may be a layer made of a resin containing polyamide, polyimide, or polyamideimide. The primer layer may be advantageously used because it can improve the adhesion at the interface between the metal wire 10, conductive connection members such as the lead frame, laminated substrate 5 (particularly the first conductive plate 3 on the main surface side), metal base 26, case 7 (inner surface), and sealing resin 8, thereby alleviating stress. The semiconductor module 50 may not have a primer layer.

[0039] (Sealing resin 8) The encapsulating resin 8 is used as an encapsulating resin layer that encapsulates the encapsulated components. It is provided in contact with the primer layer, or in semiconductor modules without a primer layer, it is provided in contact with the encapsulated components. It mainly covers the periphery of the power semiconductor chip 1, the laminated substrate 5, the metal wires 10, the lead frame, etc. The encapsulating resin 8 can be composed of a thermosetting resin composition, and is preferably composed of a highly heat-resistant thermosetting resin composition. The thermosetting resin composition includes a thermosetting resin base and may optionally contain an inorganic filler, a curing agent, a curing accelerator, and necessary additives. The thermosetting resin composition that constitutes the encapsulating resin 8 may or may not contain a fluorine-based silane coupling agent, but it is preferable that it does not contain one. This is because it may lower the glass transition temperature (Tg) of the encapsulating resin 8.

[0040] The thermosetting resin base is not particularly limited, and examples thereof include epoxy resin, phenolic resin, maleimide resin, etc. Among them, epoxy resins having at least two epoxy groups per molecule are particularly preferred due to their high dimensional stability, water resistance, chemical resistance, and electrical insulation. Specifically, it is preferable to use an aliphatic epoxy resin, an alicyclic epoxy resin, or a mixture thereof. In addition, if a case is provided, the sealing resin layer may be a silicon compound such as silicone gel.

[0041] Aliphatic epoxy resins are epoxy compounds in which the carbon atom directly bonded to the epoxy group is a carbon atom constituting an aliphatic hydrocarbon. Therefore, even if the main skeleton contains an aromatic ring, compounds that satisfy the above conditions are classified as aliphatic epoxy resins. Examples of aliphatic epoxy resins include, but are not limited to, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol AD ​​epoxy resins, biphenyl epoxy resins, naphthalene epoxy resins, cresol novolac epoxy resins, and trifunctional or higher polyfunctional epoxy resins. These can be used alone or in combination. Furthermore, naphthalene epoxy resins and trifunctional or higher polyfunctional epoxy resins have high glass transition temperatures and are therefore also referred to as high-heat-resistant epoxy resins. The inclusion of these high-heat-resistant epoxy resins can improve heat resistance.

[0042] Alicyclic epoxy resins are epoxy compounds in which the two carbon atoms constituting the epoxy group constitute an alicyclic compound. Examples of alicyclic epoxy resins include, but are not limited to, monofunctional epoxy resins, bifunctional epoxy resins, and trifunctional or higher polyfunctional epoxy resins. Alicyclic epoxy resins can be used alone or in combination with two or more different alicyclic epoxy resins. Mixing an alicyclic epoxy resin with an acid anhydride curing agent and curing it increases the glass transition temperature, so mixing an alicyclic epoxy resin with an aliphatic epoxy resin can improve heat resistance.

[0043] The thermosetting resin base used in the composition according to this embodiment may be a mixture of the above-mentioned aliphatic epoxy resin and alicyclic epoxy resin. When mixed, the mixing ratio may be any, and the mass ratio of the aliphatic epoxy resin to the alicyclic epoxy resin may be about 2:8 to 8:2, or may be about 3:7 to 7:3, and is not limited to a specific mass ratio. Preferably, the thermosetting resin base has a mass ratio of bisphenol A type epoxy resin to alicyclic epoxy resin of 1:1 to 1:4.

[0044] The thermosetting resin composition according to the present embodiment may contain an inorganic filler as an optional component. The inorganic filler may be a metal oxide or a metal nitride, and examples thereof include, but are not limited to, fused silica (fused silicon oxide), silica (silicon oxide), alumina (aluminum oxide), aluminum hydroxide, titania (titanium oxide), zirconia (zirconium oxide), aluminum nitride, talc, clay, mica, and glass fiber. These inorganic fillers can increase the thermal conductivity and reduce the thermal expansion coefficient of the cured product. These inorganic fillers may be used alone or in combination of two or more. These inorganic fillers may be microfillers or nanofillers, and two or more inorganic fillers with different particle sizes and / or types may be mixed and used.

[0045] The thermosetting resin composition may optionally contain a curing agent in addition to the thermosetting resin base, or in addition to the thermosetting resin base and inorganic filler. The curing agent is not particularly limited as long as it reacts with the thermosetting resin base, preferably the epoxy resin base, and can be cured. However, it is preferable to use an acid anhydride curing agent. Examples of the acid anhydride curing agent include aromatic acid anhydrides, specifically phthalic anhydride, pyromellitic anhydride, and trimellitic anhydride. Alternatively, examples of cyclic aliphatic acid anhydrides include tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride; and aliphatic acid anhydrides, specifically succinic anhydride, polyadipic anhydride, polysebacic anhydride, and polyazelaic anhydride. When a bisphenol A type epoxy resin is used alone or in a mixture of a bisphenol A type epoxy resin and one of the high heat-resistant epoxy resins exemplified above as the thermosetting resin base, it may be preferable not to use a curing agent, as this improves heat resistance.

[0046] The thermosetting resin composition may further contain, as an optional component, a curing accelerator, such as imidazole or a derivative thereof, a tertiary amine, a boric acid ester, a Lewis acid, an organometallic compound, or an organic acid metal salt.

[0047] The thermosetting resin composition may also contain optional additives to the extent that the properties of the composition are not impaired. Examples of additives include, but are not limited to, flame retardants, pigments for coloring the resin, and plasticizers and silicone elastomers for improving crack resistance. These optional components and their amounts can be determined by those skilled in the art according to the specifications required for the semiconductor module and / or encapsulant.

[0048] (heat dissipation fin 28) The heat dissipation fins 28 provided on the metal base 26 are arranged to fit inside the water jacket 29, and are provided from the side closest to the sidewall of the water jacket 29 (both end sides of the metal base 26) to the center of the water jacket 29 (the center of the metal base 26). The heat dissipation fins 28 may be arranged substantially vertically from the rear surface R of the metal base 26 toward the bottom surface B of the water jacket 29, or may be arranged at an angle. In the semiconductor module 50 of the embodiment, the lengths of the heat dissipation fins 28 at both ends and the center differ depending on the warp of the metal base 26, and are longer toward the center. Before the semiconductor module 50 is fastened to the water jacket 29, it warps as in the conventional case, resulting in a downward convex shape. The heat dissipation fins 28 in the center are longer by the amount of warp. By adjusting the lengths of the heat dissipation fins 28 of the metal base 26 at the center and both ends, the gap (clearance) between the tip T of the heat dissipation fin 28 and the bottom surface B of the water jacket 29 is kept constant regardless of the location of the power semiconductor chip 1 on the semiconductor module 50 after the water jacket 29 of the semiconductor module 50 is fastened (see FIG. 4 ). The lengths of the heat dissipation fins 28 increase toward the center so that the clearance remains within a certain range. Some of the heat dissipation fins 28 on both ends of the metal base 26 (e.g., the heat dissipation fin 28 on the most end side and the heat dissipation fin 28 one fin away from the end) may have substantially the same length. The bottom surface B of the water jacket 29 refers to the inner surface of the bottom plate facing the heat dissipation fin 28, and the back surface R of the metal base 26 refers to the surface facing the bottom surface B of the water jacket 29. The length of the heat dissipation fin refers to the distance in the z direction from the back surface R of the metal base to the tip of the heat dissipation fin. The z direction is a direction perpendicular to the rear surface R of the metal base or the bottom surface B of the water jacket.

[0049] The heat dissipation fins 28 may be, for example, plate-shaped, prismatic, round, or triangular. Alternatively, the heat dissipation fins 28 may be flat, thin, string-like ribbon fins or fins with embossed surfaces. If the heat dissipation fins 28 are plate-shaped, they may be arranged parallel to the short side (y direction) in FIG. 6.

[0050] (Water Jacket 29) The water jacket 29 is provided so as to cover the heat dissipation fins 28 of the metal base 26. The water jacket 29 has an inlet (not shown) and an outlet (not shown) for the coolant, and the inlet and outlet may be provided, for example, on the side walls at both ends in the x direction in FIG. 4, or at both ends in the y direction (see FIG. 6) perpendicular to the x direction. The inlet and outlet may also be offset. The coolant flows between the metal base 26 and the water jacket 29. In this way, the semiconductor module 50 and the water jacket 29 are fastened together to form a semiconductor device.

[0051] The water jacket 29 has a flat bottom plate, side walls, and a flange-shaped fastening portion. The bottom plate, side walls, and fastening portion may be integrally molded by press working or the like, or may be connected by welding or the like. The bottom plate, side walls, and fastening portion may be made of a metal material such as iron or aluminum. The water jacket 29 also has fastening members that fasten the fastening portion to the metal base 26. The fastening members are, for example, clamping screws 31, but other fastening members may also be used. The water jacket 29 has a sealing material, such as an O-ring 30 or a gasket, inside the fastening member to seal in the refrigerant. The water jacket 29, including the metal base 26 and the heat dissipation fins 28, may sometimes be referred to as a cooler.

[0052] Furthermore, it is preferable that the bottom surface B of the bottom plate of the water jacket 29 is flat. For example, it is preferable that the flatness of the bottom surface B is 0.1 mm or less. If the bottom plate is warped, the flow of the refrigerant will become uneven near the bottom surface B of the bottom plate of the water jacket 29, which is undesirable. Furthermore, when a semiconductor device having a cooler is placed inside an automobile or control device, it is required that the bottom surface B of the water jacket 29 be flat for installation stability. Furthermore, in order to maintain a constant clearance, it is difficult from a manufacturing perspective to deform the bottom plate to provide a predetermined warp while keeping the length of the heat dissipation fins 28 constant.

[0053] 2 is a cross-sectional view showing a warped state of the semiconductor module according to the embodiment. In the semiconductor module 50 according to the embodiment, as in the conventional case, when a joining process such as soldering involving heat treatment is performed on the laminated substrate 5 carrying the power semiconductor chip 1, the metal wire 10, etc., and the metal base 26, the laminated substrate 5 warps together with the metal base 26 due to the difference in linear expansion coefficient, and the semiconductor module 50 also warps, becoming convex downward (opposite the power semiconductor chip 1).

[0054] In the semiconductor device according to the embodiment, the semiconductor module 50 and the water jacket 29 are fastened together with fastening screws 31 via sealing materials such as O-rings 30 and gaskets, as in the conventional case. Because the water jacket 29 is fastened by screws at four points, the reaction force and internal pressure of the O-rings 30 and gaskets cause the center of the semiconductor module 50 to deform and become convex upward (toward the power semiconductor chip 1). Thus, even if a warped semiconductor module 50 is fastened to the water jacket 29, the warp is not corrected and warps in the opposite direction. In the embodiment, for example, the metal base 26 has a warp amount W (displacement) of 0.1 mm or more, and is convex upward. The warp amount is the difference in height between the center of the metal base 26 and the edge of the metal base 26.

[0055] Fig. 3 is a cross-sectional view showing the state of the semiconductor device according to the embodiment after fastening the water jacket. As shown in Fig. 3, the center of the semiconductor module 50 is convex upward (the metal base 26 is also convex upward), but because the lengths of the heat dissipation fins 28 of the metal base 26 are adjusted at the center and both ends, the difference in the gap (clearance) between the tip T of the heat dissipation fin 28 and the bottom surface B of the water jacket 29 is constant. Note that semiconductor chips, laminated substrates, etc. are omitted from Figs. 3 and 4.

[0056] Specifically, the heat dissipation fins 28 are formed so that their length increases from the end of the metal base 26 toward the center. For example, if the semiconductor module 50 is warped upward in the x direction (longitudinal direction) as shown in FIG. 4, the length of the heat dissipation fins 28 increases from one end of the x direction (longitudinal direction) toward the center and decreases toward the other end. Alternatively, if the semiconductor module 50 and the metal base 26 are warped upward in the y direction (transverse direction), the length of the heat dissipation fins 28 may increase from one end of the y direction (transverse direction) toward the center and decrease toward the other end. The same applies when the heat dissipation fins 28 are warped in both the x direction (longitudinal direction) and the y direction (transverse direction). Since the difference in clearance is approximately equal to the amount of warping W, the length of the heat dissipation fins 28 is set so that the distance from the bottom surface of the water jacket 29 to the tip of the heat dissipation fin 28 is constant, thereby reducing the difference in clearance. The length of the metal base 26 is the sum of the length of the heat dissipation fins 28 and the length of the heat dissipation fins 28. Therefore, the clearance is constant regardless of the placement location of the power semiconductor chip 1 on the semiconductor module 50. As a result, there is no difference in cooling performance between the heat dissipation fins 28 and the water jacket 29 at the center and end portions of the semiconductor module 50, so there is no variation in thermal resistance and the reliability of the semiconductor device can be improved.

[0057] In this embodiment, by changing the shape (length) of the heat dissipation fins 28, the flow of the refrigerant can be changed, resulting in a more efficient flow path, thereby fundamentally reducing thermal resistance. By changing the length of the heat dissipation fins 28 in areas where thermal resistance varies, it is possible to match the thermal resistance to the smallest value. In other words, the variation in thermal resistance can also be suppressed.

[0058] Fig. 4 is an enlarged cross-sectional view of the heat dissipation fins after fastening the water jacket of the semiconductor device according to the embodiment. Note that, as shown in Fig. 3, the metal base 26 and the water jacket 29 are fastened with fastening screws 31, but these are omitted in Fig. 4. In Fig. 4, C(x) is the clearance at position x, i.e., the gap between the tip T of the heat dissipation fin 28 and the bottom surface B of the water jacket 29. Position x indicates the distance from one end of the semiconductor module 50, and is 0 at that end. L(x) is the length of the heat dissipation fin 28 at position x, and D(x) is the distance between the back surface R of the metal base 26 and the bottom surface B of the water jacket 29 at position x.

[0059] In the embodiment, the specific method of adjusting the length of the heat dissipation fin 28 to the warp is as follows: (1) In the method of measuring D(x), the length L(x) of the heat dissipation fin 28 is determined so that D(x) - L(x) = CL (within a certain value), where CL is the clearance. In other words, L(x) = D(x) - CL. (2) In the method for measuring C(x), when L(0) is the length (end) of the reference heat dissipation fin 28, the length L(x) of the heat dissipation fin 28 is determined so that L(x) = L(0) + (C(x) - C(0)). Note that, as will be described later, D(x) and C(x) are obtained by forming a slit in the bottom of the water jacket 29 and measuring the distance from the slit to the bottom surface B of the water jacket 29, the back surface R of the metal base 26, and the tip T of the heat dissipation fin 28 using an optical distance meter (laser length measuring device). Note that C(0) indicates the distance from the bottom surface of the outermost heat dissipation fin 28 and the bottom surface of the test water jacket 29 to the tip of the heat dissipation fin.

[0060] Next, experimental examples were conducted to confirm the extent to which the semiconductor module 50 warps to cause variations in thermal resistance. Table 1 shows the results of the experimental examples. In the experimental examples, the length of the long side of the water jacket 29 was confirmed to be 130 mm (Experimental Examples 1 to 5), 65 mm (Experimental Examples 6 and 7), and 200 mm (Experimental Examples 8 and 9). The experiment was conducted with the amount of warp W of the metal base 26 ranging from 0 mm to 0.5 mm, and the specified clearance (the length of the gap between the tip of the heat dissipation fin 28 and the bottom surface of the water jacket 29 when the amount of warp W is 0 mm) being 0.5 mm. The maximum clearance is the sum of the amount of warp W and the specified clearance, and because the length of the heat dissipation fin 28 was not adjusted, the difference in clearance is the same as the amount of warp W.

[0061] [Table 1]

[0062] As shown in Table 1, when the warpage W of the metal base 26 in the region where the heat dissipation fins 28 are located is 0.1 mm or more, the maximum thermal resistance variation (center Rth / edge Rth) increases. For example, comparing Experimental Example 2 and Experimental Example 5, the maximum thermal resistance variation increases by 10% when the warpage W (clearance difference) is 0.2 mm or more. Similar results were obtained even when the size of the semiconductor module 50 (size of the water jacket 29) was different.

[0063] Next, we confirmed the effect of adjusting the length of the heat dissipation fins 28 when the warpage W of the metal base 26 was 0.1 mm or greater. Table 2 shows the results of a comparative example and an example. The comparative example, like the experimental examples in Table 1, is a case where the length of the heat dissipation fins 28 was not adjusted, while the example is a case where the length of the heat dissipation fins 28 was adjusted. In the comparative example and example, the length of the long side of the water jacket 29 was 130 mm (comparative examples 1 to 3, examples 1 to 6) and 65 mm (comparative example 4, example 7). Experiments were conducted with the warpage W of the metal base 26 ranging from 0.1 mm to 0.5 mm and a specified clearance of 0.5 mm. The maximum clearance is the sum of the warpage W and the specified clearance. In the comparative example where the length of the heat dissipation fins 28 was not adjusted, the difference in clearance was the same as the warpage W. In the example where the length of the heat dissipation fins 28 was adjusted, the difference in clearance was the warpage W minus the adjustment value of the length of the heat dissipation fins 28.

[0064] In addition, a P / C (power cycle) test was conducted on the semiconductor device with the heat dissipation fins under each condition to confirm the reliability of the comparative example and the example. The P / C test was conducted by applying current from 40°C to 175°C, with one cycle consisting of 2 seconds of current operation and 9 seconds of rest, and the number of cycles until no abnormalities in electrical characteristics due to the progression of cracks on the resin surface were observed was recorded. If the number of cycles was less than 10k, it was evaluated as NG, and if the number of cycles was 10k or more, it was evaluated as OK.

[0065] [Table 2]

[0066] Fig. 5 is a graph showing an evaluation of the thermal resistance variation of the metal base according to the embodiment. Fig. 6 is a top view showing the measurement positions of the thermal resistance variation of the metal base according to the embodiment. In Fig. 5, the horizontal axis indicates the measurement positions of the thermal resistance variation. UH, UL, VH, VL, WH, and WL are the positions of the power semiconductor chip 1 shown in Fig. 6. The vertical axis indicates the normalized thermal resistance where the thermal resistance (K / W) at the UH position is set to 1.

[0067] Figure 5 shows the results of Comparative Example 2 (solid line) and Example 2 (dotted line) in Table 2. The results are for a case where the length of the long side of the water jacket 29 is 130 mm, the amount of warpage W of the metal base 26 is 0.2 mm, and the specified clearance is 0.5 mm. With water flowing, electricity was passed through the circuit, and the thermal resistance (Rth) was calculated from the temperature of the power semiconductor chip 1 and the backside temperature of the metal base 26 at the measurement point relative to the power consumption. The results show that the thermal resistance varies by 10% or more at the central areas VH, VL, etc., where the clearance is large.

[0068] As shown in Table 2, it has been found that a maximum thermal resistance variation of 1.1 (10%) or more is undesirable because it creates a thermal gradient within the module, which causes thermal stress and makes it more likely for peeling to occur at the interfaces between the sealing resin 8 and the laminated substrate 5 or the power semiconductor chip 1, reducing reliability in P / C (power cycle test) and other tests. Therefore, it is preferable to keep the maximum thermal resistance variation below 1.1.

[0069] When the thermal resistance of the metal base 26 increases, the heat generation (temperature) of the power semiconductor chip 1 increases during operation. This reduces the reliability of the semiconductor device and increases the thermal gradient between the power semiconductor chip 1 and the metal base 26, leading to deterioration of the semiconductor device's characteristics (breakdown of element junctions) and deterioration of the bonding material, resulting in a decrease in P / C tolerance. Furthermore, variations in thermal resistance shorten the semiconductor device's failure life and reduce its reliability. In this case, the current value of the power semiconductor chip 1 must be reduced to operate it at a lower performance. The decrease in P / C tolerance becomes significant when the maximum thermal resistance variation exceeds 10%, so it is necessary to keep it below 10%.

[0070] For this reason, in this embodiment, it is preferable to make the clearance difference (the difference between the maximum clearance C(x) and the minimum clearance C(x)) less than 0.2 mm, since this will keep the maximum thermal resistance variation to 1.1 or less (10% or less).Furthermore, if the clearance difference is 0.1 mm or less, this will keep the maximum thermal resistance variation to 1.06 (6%), which is even more preferable.

[0071] (Method of manufacturing a semiconductor device according to an embodiment) Next, a method for manufacturing a semiconductor device according to an embodiment will be described. First, the warpage of the metal base 26 is measured. To measure the warpage of the metal base 26, a test module having the same components and size as an actual semiconductor device is prepared. A semiconductor device is prepared in which a test water jacket 29 is fastened to an assembly in which a laminated substrate 5 carrying a power semiconductor chip 1, wiring members, etc. is sealed with sealing resin 8, and the metal base 26 having heat dissipation fins 28 is joined together.

[0072] Next, a slit is made at a predetermined position x on the bottom of the test water jacket 29, and an optical distance meter (laser length measuring device) is used to measure the clearance C(x), which is the distance from the bottom surface B of the water jacket 29 to the tip T of the heat dissipation fin 28, which has a uniform length (clearance measurement).

[0073] Next, a metal base 26 is formed having heat dissipation fins 28 whose lengths are adjusted according to the amount of warping of the metal base 26. For example, a metal base 26 having heat dissipation fins 28 of uniform length is prepared, and the length L(x) of the heat dissipation fins 28 at each position is adjusted by machining or the like so that it is equal to the sum of the difference between the distance C(x) from the bottom surface of the test water jacket 29 to the tip of the heat dissipation fin and the distance C(0) from the bottom surface of the test water jacket 29 to the tip of the heat dissipation fin, where C(0) is the length of the most endmost heat dissipation fin 28 among the heat dissipation fins 28. D(x) may also be used.

[0074] After measuring the amount of warpage of the metal base 26 in this manner, the power semiconductor chip 1 is bonded to the laminated substrate 5 with the first bonding layer 25a, and a laminate is fabricated by bonding the power semiconductor chip 1, wiring members such as metal wires 10, and the laminated substrate 5. After this, the metal base 26, with the length of the heat dissipation fins 28 adjusted, is bonded to the laminated substrate 5 with the second bonding layer 25b, and the case 7 is attached to the metal base 26. After that, the lead frame is bonded and wire bonding is performed with the metal wires 10. Note that the metal wires 10 may be used instead of the lead frame. Next, a primer layer may be formed. After this, the laminated substrate 5 mounted with the power semiconductor chip 1, wiring members, and the like is sealed with sealing resin 8. The process up to this point results in the state shown in FIG. 2.

[0075] Next, the water jacket 29 is fastened with fastening screws 31 via a sealing material such as an O-ring 30 or a gasket. The water jacket is fastened by screwing at four points. With these steps, the state shown in Figure 3 is reached, and the semiconductor device is manufactured.

[0076] Alternatively, the length of the heat dissipation fin 28 may be adjusted to the warpage by measuring D(x). In this case, a slit is made in the bottom of the test water jacket 29, and an optical distance meter (laser length measuring device) is used to measure D(x), which is the distance from the bottom surface B of the water jacket 29 to the rear surface R of the metal base 26.

[0077] As described above, according to the embodiment, the length of the heat dissipation fins is formed to increase from the edge of the metal base toward the center. This ensures a constant clearance regardless of the placement location of the power semiconductor chips in the semiconductor module. As a result, there is no difference in cooling performance between the heat dissipation fins and the water jacket at the center and edge of the semiconductor module, so there is no variation in thermal resistance and the reliability of the semiconductor device can be improved.

[0078] The present invention can be modified in various ways without departing from the spirit of the present invention, and in each of the above-described embodiments, for example, the dimensions of each part, the impurity concentration, etc. are variously set according to the required specifications, etc. Furthermore, each of the above-described embodiments can be applied to wide bandgap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) in addition to silicon as the semiconductor. [Industrial Applicability]

[0079] As described above, the semiconductor device and the method of manufacturing the semiconductor device according to the present invention are useful for semiconductor modules used in power conversion devices such as inverters, power supply devices for various industrial machines, and igniters for automobiles. [Explanation of symbols]

[0080] 1, 101 Power semiconductor chip 2, 102 insulating substrate 3, 103 First conductive plate 4, 104 Second conductive plate 5, 105 laminated board 7,107 cases 8, 108 Sealing resin 9, 109 Metal terminal 10, 110 Metal Wire 25a 1st bonding layer 25b 2nd bonding layer 26, 126 Metal base 28, 128 Heat dissipation fin 29, 129 Water Jacket (WJ) 30, 130 O-ring 31, 131 Fastening screws 50, 150 semiconductor modules 125 Bonding layer R Back B Bottom T tip

Claims

1. a laminated substrate on which a semiconductor element is mounted via a first bonding layer; a metal base having a plurality of heat dissipation fins bonded to the laminated substrate via a second bonding layer having the same or different composition or material as the first bonding layer; a water jacket joined to the metal base; Equipped with The semiconductor device is characterized in that the plurality of heat dissipation fins are formed so as to become longer from the end portion toward the center portion of the metal base.

2. 2. The semiconductor device according to claim 1, wherein the metal base is convex toward the semiconductor element.

3. 3. The semiconductor device according to claim 2, wherein the amount of warping of the metal base is 0.1 mm or more.

4. 2. The semiconductor device according to claim 1, wherein a clearance between the tips of the plurality of heat dissipation fins and the bottom surface of the water jacket is smaller than 0.2 mm.

5. 2. The semiconductor device according to claim 1, wherein a clearance between the tips of the plurality of heat dissipation fins and the bottom surface of the water jacket is less than 0.1 mm.

6. 2. The semiconductor device according to claim 1, wherein the maximum thermal resistance variation of the metal base is 1.1 or less.

7. 2. The semiconductor device according to claim 1, wherein the maximum thermal resistance variation of the metal base is 1.06 or less.

8. a first step of mounting a semiconductor element on a laminated substrate via a first bonding layer; a second step of bonding a metal base having a plurality of heat dissipation fins to the laminated substrate via a second bonding layer having the same or different composition and material as the first bonding layer; a third step of joining a water jacket to the metal base; Including, A method for manufacturing a semiconductor device, characterized by including an adjustment step of measuring the amount of warping of the metal base before the second step, and adjusting the lengths of the multiple heat dissipation fins so that they become longer from the ends of the metal base toward the center according to the amount of warping.

9. The adjusting step includes:

9. The method for manufacturing a semiconductor device according to claim 8, characterized in that a test water jacket is joined to the metal base, and the distance from the bottom of the test water jacket to the tip of the heat dissipation fin or the distance from the bottom of the test water jacket to the back surface of the metal base is measured, and the length of the heat dissipation fin is adjusted so that the distance remains constant.

10. The adjusting step includes: The method for manufacturing a semiconductor device according to claim 9, characterized in that, when the length of the most extreme fin among the plurality of fins is L(0), the distance from the bottom of the test water jacket to the tip of the fin is C(x), and the distance from the most extreme fin among the plurality of fins and the bottom of the test water jacket to the tip of the fin is C(0), the length L(x) of the fin at each position x is adjusted so that L(x) = L(0) + (C(x) - C(0)).

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