JP2008270295A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device having high reliability and cooling performance. <P>SOLUTION: The semiconductor device includes a semiconductor chip 11 having a semiconductor element formed thereon; a heat sink member 21 made of a material principally containing ceramics and used for dissipating heat generated in the semiconductor chip 11 to a heat exchange medium; a top plate 50a as a supporting member for supporting the heat sink member 21; a resin case 53 and screws 59 as fixing members for pressing the heat sink member 21 onto the top plate 50a to fix thereto; an O-ring 57 as an annular elastic member attached between the resin case 53 and the heat sink member 21; and an O-ring 54 as an annular sealing member attached between the heat sink member 21 and the top plate 50a. The O-rings 57, 54 can release local concentration of a pressing force to the heat sink member 21. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor device on which a semiconductor chip is mounted, and particularly to a device suitable for a power device.

  In recent years, modules using IGBTs or FETs have been used as power devices (semiconductor devices) including motor-driven switching elements such as electric vehicles, hybrid vehicles, and fuel cells. In particular, in-vehicle semiconductor devices require a cooling structure with a small area and a large heat dissipation function because of the demand for miniaturization.

  In order to meet such a demand, Patent Document 1 discloses that an insulating substrate made of ceramics having high thermal conductivity such as AlN and SiC is used as a heat sink made of an Al alloy as a support member, and an aluminum-silicon brazing material. A structure in which layers are joined to each other is disclosed (FIG. 2 of Patent Document 1, etc.). Also,

JP 2001-168256 A

  However, in the technique of Patent Document 1, heat between an insulating substrate having a thermal expansion coefficient of about 3 to 4.5 ppm / K and a heat radiator having a thermal expansion coefficient of around 20 ppm / K between the insulating substrate and the heat radiator. A large thermal stress resulting from the difference in expansion coefficient is generated. Therefore, by applying the structure shown in FIG. 4 of the same document and using a resin case that is screwed, an insulating substrate is pressed against and fixed to a radiator, and a structure that relieves thermal stress can be considered.

  However, the ceramic material is a hard and brittle material, and when the insulating substrate made of ceramic is pressed and fixed to the radiator by screwing or the like, if the large pressing force is concentrated locally, the insulating substrate may be damaged. The reliability of the semiconductor device is deteriorated.

  An object of the present invention is to provide a semiconductor device having high reliability by adopting a structure that can alleviate local concentration of thermal stress and pressing force on a heat sink member.

  In the semiconductor device of the present invention, the heat sink member made of a material mainly composed of ceramics is pressed against the support member by the fixing member, and is made of an elastic material between the fixing member and the heat sink member. An annular seal member is interposed.

  As a result, since the heat sink member is made of a material whose main component is ceramics, the difference in thermal expansion coefficient from Si or SiC frequently used as a semiconductor chip material is reduced, and the thermal stress generated in the heat sink member is reduced. Is done. Further, even if the heat sink member is pressed by the fixing member, the local elastic concentration of the pressing force on the heat sink member can be reduced because the elastic elastic member is mounted between the fixing member and the heat sink member. Therefore, damage to the heat sink member can be prevented, and the reliability of the semiconductor device is improved.

  By mounting an elastic annular seal member between the heat sink member and the support member, the function of further reducing the local concentration of the pressing force on the heat sink member while maintaining the sealing performance of the space below the heat sink Can be increased.

  Since the support member is pressed by a fixing member having a plurality of screw members arranged so as to surround the annular elastic member, local concentration of the pressing force on the heat sink can be reliably suppressed.

  Since the heat sink member is made of AlN, BN, SiN, Si-SiC or Al-SiC having both high thermal conductivity and low thermal expansion coefficient, in addition to reducing thermal stress, heat dissipation function by reducing thermal resistance Can be improved.

  Since the semiconductor element formed in the semiconductor device is a power device using a wide band gap semiconductor, even if the chip temperature reaches a relatively high temperature, the thermal stress applied to the heat sink member is made as small as possible to improve reliability. Can be kept high.

  According to the semiconductor device of the present invention, since local concentration of thermal stress and pressing force on the heat sink member is alleviated, a highly reliable semiconductor device can be obtained.

  FIG. 1 is a perspective view showing a schematic external structure of a semiconductor device (power module) in an embodiment. In FIG. 1, illustration of wiring such as a resin case 53 (see FIGS. 2 and 3) and a bonding wire which will be described later is omitted. As shown in the figure, the semiconductor device of this embodiment is configured by joining a chip unit 10 on a radiator 50. The radiator 50 includes a top plate 50a and a container 50b joined to the top plate 50a. The top plate 50a is provided with a number of rectangular through holes for incorporating the chip unit 10 therein. In the present embodiment, a large number of rectangular through holes are provided, but only one may be provided. The top plate 50a and the container 50b constituting the radiator 50 are made of aluminum or an aluminum alloy, and can be manufactured by die casting, extrusion, forging, casting, machining, or the like. In addition, a cooling water supply pipe 58a, which is a heat exchange medium, and a cooling water discharge pipe 58b are attached to the container 50b of the radiator 50.

  In the assembly process of the present embodiment, after the chip unit 10 is mounted on the top plate 50a of the radiator 50, the top plate 50a is joined to the container 50b. This joining may be performed by mechanical caulking or the like. Further, in the present embodiment, the radiator 50 is formed by individually forming the top plate 50a and the container 50b and then joining them together, but the top plate and the container may be integrally formed. In that case, the radiator can be formed, for example, by die casting using an integral type. Thereafter, as will be described later, the resin case 53 is attached to the top plate 50a by screws.

  FIG. 2 is a plan view of the semiconductor device according to the embodiment. 3 is a cross-sectional view of the semiconductor device according to the embodiment, taken along line III-III in FIG. 2 and 3, illustration of wiring such as bonding wires above the semiconductor chip 11 is omitted. As shown in FIGS. 2 and 3, a resin case 53 is attached on the top plate 50 a, and the entire opening of the resin case 53 is covered with a heat sink member. Three chip units 10 are disposed on the heat sink member 21. The top plate 50a is a support member that supports the heat sink member.

  A groove 55 that surrounds the opening is formed on the top surface of the top plate 50 a, and an O-ring 54 that is an annular seal member is mounted in the groove 55. On the other hand, a groove 56 surrounding the opening is formed on the surface of the resin case 53 that faces the upper surface of the heat sink member 21, and an O-ring 57 that is an annular elastic member is mounted in the groove 56. The O-ring 57 does not necessarily need a sealing function, but the O-ring 54 needs to have a function of sealing the flow path 51 that is the internal space of the radiator 50. A total of 16 screws 59 arranged so as to surround the O-ring 57 are attached to the resin case 53, and the resin case 53 is substantially attached to the heat sink member 21 by the tightening force of the 16 screws 59. It is comprised so that equal pressing force may be applied. That is, the resin case 53 and the screw 59 constitute a fixing member that presses and fixes the heat sink member 21 to the top plate 50a.

  In the flow path 51 between the top plate 50a and the container 50b of the radiator 50, cooling water as a heat exchange medium flows in a direction orthogonal to the paper surface of FIG. The semiconductor chip 11 is formed using a single crystal SiC substrate, and an upper surface electrode (not shown) and a back surface electrode 14 connected to an active region of a diode or IGBT (semiconductor element) are provided on the upper surface and the lower surface, respectively. Is provided. The chip unit 10 is further joined to the back electrode 14 of the semiconductor chip 11 by solder, brazing material, etc., and formed from a metal plate such as Cu—Mo, Cu—W, etc., a heat sink member 21, A solder layer 26 interposed between the metal wirings 23 is provided. The heat sink member 21 has a flat plate portion 21 a and a large number of fin members 21 b that protrude from the flat plate portion 21 a toward the flow path 51. However, it is not always necessary to have the fin portion 21b.

  In the present embodiment, the dimensions of each member are as follows, for example. The size of the semiconductor chip 11 is 8.7 mm × 8.7 mm × 0.38 mm, the size of the metal wiring 23 is 10 mm × 20 mm × 0.6 mm, and the size of the heat sink member 21 (flat plate portion) is 48 mm. The outer dimensions of the top plate 50a are 55 mm x 33 mm x 10 mm, the size of the opening is 42 mm x 24 mm, and the outer dimensions of the container 50b are 55 mm x 33 mm x 20 mm. The dimensions of the recesses constituting the path 51 are 50 mm × 29 mm × 10 mm, the dimensions of the grooves 55 and 56 in the long side and short side directions shown in FIG. 2 are 46 mm × 25 mm, the cross-sectional dimensions are 4 mm wide and depth 2 mm. The lengths and cross-sectional dimensions of the O-rings 54 and 57 can be appropriately selected according to the dimensions of the grooves 55 and 56. The above dimensions are examples, and dimensions other than these values can be adopted depending on the type and application of the semiconductor device.

  As the annular elastic member or the annular seal member of the present invention, not only the O-ring in the embodiment but also a reciprocating or fixing seal member called a square ring, a T ring, or a D ring can be used. In addition, a reciprocating seal member called U packing, C packing, L packing, V packing, or X ring can be used for the fixing annular member or the annular sealing member in the present invention.

  The materials constituting the O-rings 54 and 57 include nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), fluorine rubber (FKM), silicone rubber (VMQ), ethylene propylene rubber (EPDM), chloroprene rubber (CR ), Acrylic rubber (ACM), butyl rubber (BR), urethane rubber (U), chlorosulfonated polyethylene (CSM), epichlorohydrin rubber (CO, ECO), natural rubber (NR), fluorosilicone rubber (FVMQ), styrene butadiene In addition to rubber materials such as rubber (SBR), there are carbon and various resin materials, and any of them may be used. However, when the heat sink member 21 is at a relatively high temperature, a heat resistant material such as silicone rubber or fluorine rubber is particularly preferable.

  In the present embodiment, the material of the heat sink member 21 is composed of nitride ceramics such as AlN, BN, and SiN, or carbide ceramics such as SiC and WC. Although these are insulating materials, the heat sink member 21 can also be comprised by the composite ceramic material which has electroconductivity, such as Si-SiC and Al-SiC. In that case, instead of the solder layer 26, an insulating resin layer having a high thermal conductivity or an AlN plate may be provided.

  The materials of the heat sink member 21 are not limited to the materials listed above, but are preferably limited to these materials for the following reasons. For example, the thermal expansion coefficient α of AlN is about 4.5 (ppm / K), the thermal conductivity is about 200 (W / m · K), and the thermal expansion coefficient α of Si—SiC is about 2.3-3. (Ppm / K), thermal conductivity is about 200 (W / m · K), thermal expansion coefficient α of SiC is about 3 (ppm / K), and thermal conductivity is about 210 (W / m · K). The thermal expansion coefficient α of GaN is about 3.2 or 5.6 (ppm / K), and the thermal conductivity is about 130 (W / m · K). Accordingly, these materials are much larger than the thermal conductivity of general-purpose ceramics such as alumina and have a thermal conductivity close to that of aluminum (thermal conductivity of about 240 (W / m · K), while having a thermal expansion coefficient α. Is much smaller than aluminum (α≈23 (ppm / K)), and the thermal expansion coefficient α of the semiconductor chip is about 3 (ppm / K for Si single crystal, about 4 (ppm / K) for SiC single crystal) Therefore, by configuring the heat sink member 21 with the nitride ceramics, carbide ceramics, or composite ceramics, it is possible to reduce the thermal stress as much as possible while maintaining a large heat dissipation function.

  When the heat sink member 21 is made of AlN, SiN, GaN, BN, SiC, WC, Si—SiC, Al—SiC, or the like, a metallized layer is formed in a region where the heat sink member 21 is bonded to other members. By doing so, soldering and brazing can be easily performed.

  The material of the metal wiring 23 is not limited to Cu—Mo or Cu—W. For example, a metal such as Cu, Al, and Kovar (Fe—Ni—Co) may be used. However, the thermal expansion coefficient α of Cu—Mo is about 6.5 to 8 (ppm / K), the thermal conductivity is about 200 (W / m · K), and the thermal expansion coefficient α of Cu—W is about 6 .5-7 (ppm / K), and thermal conductivity is 180-200 (W / m · K). The thermal conductivity of these composite materials is much lower than that of Cu (about 400 (W / m · K)), but is close to that of aluminum (Al), while the thermal expansion coefficient α is , Much smaller than the thermal expansion coefficient α (≈17) of Cu and close to the thermal expansion coefficient α of the semiconductor chip (about 3 (ppm / K) for Si and about 4 (ppm / K) for SiC). Moreover, it is close to the thermal expansion coefficient of the heat sink member 21 containing ceramics as a main component. Therefore, by configuring the metal wiring 23 from Cu—Mo or Cu—W, it is possible to reduce the thermal stress as much as possible while maintaining a large heat transfer amount.

  The semiconductor chip in the semiconductor device of the present invention is not limited to the one using SiC, but may be one using Si or GaN (thermal expansion coefficient is about 5.6 (a axis) -3.2. Other wide band gap semiconductors such as (c-axis) (ppm / K)) may be used.

  The heat exchange medium that exchanges heat with the heat sink member 21 is preferably water in consideration of cooling ability and cost. However, instead of water, a gas such as helium, argon, nitrogen, or air may be used.

(Other embodiments)
The structure of the embodiment of the present invention disclosed above is merely an example, and the scope of the present invention is not limited to the scope of these descriptions. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  In the above embodiment, the diode and the IGBT are formed on the semiconductor chip 11, but a semiconductor chip on which a MOSFET, a JFET, or the like is formed instead of the IGBT may be used. Further, a semiconductor chip on which only diodes are formed and a semiconductor chip on which only IGBTs, MOSFETs, and JFETs are formed may be disposed.

  In the above-described embodiment, the fixing member that presses and fixes the heat sink member 21 to the top plate 50a is configured by the resin case 53 and the screw 59. However, instead of the screw 59, pressing is performed using the biasing force of the spring. Other structures, such as using various mechanisms, can also be employed.

  The heat sink member or the semiconductor device of the present invention can be used for various devices equipped with MOSFET, IGBT, diode, JFET and the like.

It is a perspective view which shows the external appearance structure of the semiconductor device in embodiment. It is a top view of the semiconductor device in an embodiment. It is sectional drawing in the III-III line | wire of the semiconductor device of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Chip unit 11 Semiconductor chip 14 Back surface electrode 21 Heat sink member 21a Flat plate part 21b Fin part 23 Metal wiring 26 Solder layer 50 Radiator 50a Top plate 50b Container 51 Flow path 53 Resin case 54 O-ring (annular seal member)
55 groove 57 O-ring (annular elastic member)
56 groove 58a supply pipe 58b discharge pipe 59 screw

Claims (5)

A semiconductor chip on which a semiconductor element is formed;
A heat sink member for releasing heat of the semiconductor chip to a heat exchange medium;
A support member for supporting the heat sink member;
A fixing member that presses and fixes the heat sink member to the support member;
An annular elastic member mounted between the heat sink member and the fixing member;
A semiconductor device comprising: The semiconductor device according to claim 1,
A semiconductor device, further comprising an annular seal member mounted between the heat sink member and the support member. The semiconductor device according to claim 1 or 2,
The fixing member has a plurality of screw members arranged so as to surround the annular elastic member. The semiconductor device according to claim 1,
The said heat sink member is a semiconductor device comprised by AlN, BN, SiN, Si-SiC, or Al-SiC. In the semiconductor device according to claim 1,
The semiconductor device is a power device using a wide band gap semiconductor.

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