Semiconductor Device

Abstract

To provide a semiconductor device capable of reducing a stress.SOLUTION: A semiconductor device 100 comprises a semiconductor element 1, a heat spreader 2 composed of a high thermal conductive material and joined to the semiconductor element 1, and a chiller 3 bonded to the heat spreader 2 on a surface facing a surface bonded to the semiconductor element 1 among surfaces of the heat spreader 2. Thermal conductivity of the heat spreader 2 is greater than thermal conductivity of the chiller 3. A groove 4 opening on a bonding surface between the heat spreader 2 and the chiller 3 is formed in the heat spreader 2. A shape of the bonding surface between the heat spreader 2 and the chiller 3 is rectangular. At least one of virtual extension lines 5 extending along a longitudinal direction of the groove 4 crosses a surface 8 on which a long side of the heat spreader 2 is formed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor device. [Background technology]

[0002] Conventionally, a heat dissipation device that relieves stress (thermal stress) caused by heat generation from a heat generating element has been known (Patent Document 1). The heat mass member described in Patent Document 1 has a stress relief portion and a heat mass portion in its thickness direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-130060 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the heat dissipation device described in Patent Document 1, the aspect ratio of the contact surface between the cooler and the heat mass member is not sufficient to provide a sufficient stress relaxation effect.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor device capable of reducing stress. [Means for solving the problem]

[0006] A semiconductor device according to one aspect of the present invention includes a semiconductor element, a heat spreader made of a highly thermally conductive material and bonded to the semiconductor element, and a cooler bonded to the heat spreader on a surface of the heat spreader opposite to the surface bonded to the semiconductor element. The heat spreader has a groove formed therein that opens into the bonding surface between the heat spreader and the cooler. At least one of imaginary extension lines extending along the longitudinal direction of the groove intersects with a surface forming a long side of the heat spreader. Effect of the Invention

[0007] According to the present invention, it is possible to reduce stress. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a top view of a semiconductor device 100 according to the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 3 is a top view of the semiconductor device 100 according to the second embodiment. [Figure 4] FIG. 4 is a cross-sectional view of the semiconductor device 100 according to the third embodiment. [Diagram 5] FIG. 5 is a cross-sectional view of a semiconductor device 100 according to the fourth embodiment. [Figure 6] FIG. 6 is a top view of the semiconductor device 100 according to the fifth embodiment. [Figure 7] FIG. 7 is a top view of the semiconductor device 100 according to the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and the description will be omitted.

[0010] (First embodiment) A semiconductor device 100 according to a first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a top view of the semiconductor device 100. Figure 2 is a cross-sectional view taken along line AA of Figure 1.

[0011] As shown in Figures 1 and 2, one surface of the semiconductor element 1 and one surface of the heat spreader 2 are bonded together. If the surface of the semiconductor element 1 visible when viewed from above the semiconductor device 100 is defined as the "upper surface", the surface opposite to this "upper surface" as the "lower surface", and the surface of the heat spreader 2 visible when viewed from above the semiconductor device 100 is defined as the "upper surface" and the surface opposite to this "upper surface" as the "lower surface", then the lower surface of the semiconductor element 1 and the upper surface of the heat spreader 2 are said to be bonded together. A well-known method is used for bonding. Examples of well-known methods include soldering, metal bonding, and diffusion bonding.

[0012] Although the semiconductor element 1 is not particularly limited, an example thereof is an IGBT (Insulated Gate Bipolar Transistor). The heat spreader 2 is used to increase the heat dissipation efficiency and is made of a highly thermally conductive material. An example of the highly thermally conductive material is copper.

[0013] The heat spreader 2 and the cooler 3 are joined at a surface opposite to the joint surface between the semiconductor element 1 and the heat spreader 2. If the surface of the cooler 3 visible in the top view of the semiconductor device 100 is defined as the "upper surface" and the surface opposite to the "upper surface" is defined as the "lower surface", the lower surface of the heat spreader 2 and the upper surface of the cooler 3 are said to be joined. The cooler 3 is made of aluminum as an example. Therefore, in this embodiment, the thermal conductivity of the heat spreader 2 is higher than that of the cooler 3. The cooler 3 is provided with a plurality of plate-shaped fins 10, and a gap 11 is formed between the fins 10. Reference numeral 6 in FIG. 1 indicates the longitudinal direction of the heat spreader 2. Reference numeral 6 also indicates the longitudinal direction of the joint surface between the heat spreader 2 and the cooler 3. The heat spreader 2 and the cooler 3 are joined so that the longitudinal direction of the heat spreader 2 and the longitudinal direction of the fins 10 are the same direction. In this embodiment, a multi-hole pipe is used as the cooler 3, but an open-type cooler such as a comb-teeth type cooler may be used. The shapes of the semiconductor element 1, the heat spreader 2, and the cooler 3 are not particularly limited, but are, for example, rectangular.

[0014] As shown in FIGS. 1 and 2, a groove 4 is formed in the heat spreader 2. The groove 4 opens on the joint surface between the heat spreader 2 and the cooler 3. The joint surface between the heat spreader 2 and the cooler 3 has a rectangular shape. Reference numeral 9 indicates the longitudinal direction of the groove 4. Reference numeral 9 also indicates the lateral direction of the joint surface between the heat spreader 2 and the cooler 3. Reference numeral 5 indicates an extension line of the groove 4. More specifically, reference numeral 5 indicates a virtual extension line extending along the longitudinal direction of the groove 4. Reference numeral 8 indicates a surface (side surface) forming the long side of the heat spreader 2 in a side view of the semiconductor device 100. At least one of the extension lines 5 intersects with the surface 8 forming the long side of the heat spreader 2 at the joint surface between the heat spreader 2 and the cooler 3. The intersection point is indicated by reference numeral 7. The position of the surface where the extension line 5 intersects may be any position on the surface forming the long side of the heat spreader 2. Therefore, the extension line 5 may intersect with the surface 8 forming the long side of the heat spreader 2 at a position other than the joint surface between the heat spreader 2 and the cooler 3 .

[0015] (Action and effect) The semiconductor device 100 according to the first embodiment includes a semiconductor element 1, a heat spreader 2 made of a highly thermally conductive material and bonded to the semiconductor element 1, and a cooler 3 bonded to the heat spreader 2 on a surface of the heat spreader 2 opposite to the surface bonded to the semiconductor element 1. The thermal conductivity of the heat spreader 2 is greater than that of the cooler 3. The heat spreader 2 is formed with a groove 4 that opens on the bonding surface between the heat spreader 2 and the cooler 3. The bonding surface between the heat spreader 2 and the cooler 3 is rectangular. At least one of imaginary extension lines 5 extending along the longitudinal direction of the groove 4 intersects with a surface 8 forming the long side of the heat spreader 2. This makes it easier for the heat spreader 2 to expand and contract in the longitudinal direction 6, making it possible to reduce stress.

[0016] Moreover, the cooler 3 has a plurality of plate-shaped fins 10 formed in the same direction as the long sides of the heat spreader 2. By forming the fins 10 in this manner in the same direction as the longitudinal direction 6 of the contact surface between the heat spreader 2 and the cooler 3, the stress reduction effect is further enhanced.

[0017] In addition, in FIGS. 1 and 2, the groove 4 is formed perpendicular to the joint surface between the heat spreader 2 and the cooler 3, but this is only an example and it is not necessary that the groove 4 is formed perpendicular.

[0018] Second embodiment Next, a semiconductor device 100 according to a second embodiment will be described with reference to FIG. 3. In the second embodiment, as shown in FIG. 3, the grooves 4 reach the ends (both ends) of the heat spreader 2. In other words, the grooves 4 open to the surfaces (both surfaces) that form the long sides of the heat spreader 2. It may also be expressed that the grooves 4 reach the surfaces (both surfaces) that form the long sides of the heat spreader 2. As a result, the heat spreader 2 is divided by the grooves 4, which further enhances the effect of reducing stress.

[0019] Third embodiment Next, with reference to FIG. 4, a semiconductor device 100 according to a third embodiment will be described. In FIG. 4, reference numeral 13 indicates the groove bottom of the groove 4, and reference numeral 14 indicates the opening of the groove 4 formed on the joint surface between the heat spreader 2 and the cooler 3. In FIG. 4, reference numeral L1 indicates the length of the groove bottom 13 in the longitudinal direction 9, reference numeral L2 indicates the length of one side of the semiconductor element 1 in the cross-sectional view, and reference numeral L3 indicates the length of the opening 14 in the longitudinal direction 9. The relationship between the lengths L1 to L3 is L3>L2>L1. As shown in FIG. 4, the length L1 of the groove bottom 13 in the longitudinal direction 9 of the groove 4 is shorter than the length L3 of the opening 14 in the longitudinal direction 9 of the groove 4, and is shorter than the length L2 of one side of the semiconductor element 1. It has been described that an example of the shape of the semiconductor element 1 is a quadrangle. The length L1 is shorter than the length of any side (any side) of the four sides of the semiconductor element 1. In this way, by tapering the groove 4 (providing the groove bottom 13), a heat path can be secured, and the thermal resistance can be reduced. 4, a trapezoidal shape is described as an example of the taper, but the taper may be formed into a triangular shape. In this case, a vertex is formed instead of the groove bottom 13.

[0020] (Fourth embodiment) Next, referring to FIG. 5, the semiconductor device 100 according to the fourth embodiment will be described. In FIG. 5, the reference character L4 indicates the depth of the groove 4, and the reference character L5 indicates the length from the groove bottom 13 to the joint surface between the semiconductor element 1 and the heat spreader 2. The "depth of the groove 4" is the length from the opening 14 to the groove bottom 13 in a cross-sectional view. The relationship between the reference characters L4 and L5 is L5>L4. The depth L4 of the groove 4 is shorter than the length L5 from the groove bottom 13 of the groove 4 to the joint surface between the semiconductor element 1 and the heat spreader 2. In other words, the groove bottom 13 and the joint surface between the semiconductor element 1 and the heat spreader 2 are separated by a predetermined distance (length L5). Since the groove bottom 13 corresponds to a stress relaxation portion, the joint surface between the semiconductor element 1 and the heat spreader 2 is not in contact with the stress relaxation portion (groove bottom 13). This ensures a thickness (length L5) for diffusing heat, and makes it possible to further reduce thermal resistance. The relationship between the symbols L4 and L5 is not particularly limited as long as L5>L4, but L4 may be set to be less than 50% of L5.

[0021] Fifth embodiment Next, with reference to FIG. 6, a semiconductor device 100 according to a fifth embodiment will be described. In the fifth embodiment, as shown in FIG. 6, a plurality of grooves 4 are formed. In FIG. 6, three grooves 4 are formed. This allows the heat spreader 2 to expand and contract easily, and it is possible to further reduce stress. In FIG. 6, the grooves 4 are formed so as not to intersect with each other, but the grooves 4 may be formed so as to intersect with each other. In FIG. 6, the grooves 4 reach the ends of the heat spreader 2, but this is just one example, and the grooves 4 may not reach the ends of the heat spreader 2 as shown in FIG. 1.

[0022] Sixth embodiment Next, referring to FIG. 7, a semiconductor device 100 according to a sixth embodiment will be described. In the sixth embodiment, a plurality of grooves 4 are formed, which is the same as in the fifth embodiment. In the sixth embodiment, as shown in FIG. 7, a plurality of semiconductor elements 1 are also provided to be joined to the heat spreader 2. In FIG. 7, two semiconductor elements 1 are provided. As shown in FIG. 7, when the plurality of semiconductor elements 1 and the plurality of grooves 4 are projected onto the joining surface between the heat spreader 2 and the cooler 3, the plurality of grooves 4 are formed so as to separate the plurality of semiconductor elements 1. At this time, it is preferable that the groove 4 is formed at the center (or near the center) of the heat spreader 2. As shown in FIG. 7, the plurality of grooves 4 are formed so as to separate the semiconductor elements 1, and one of the plurality of grooves 4 is formed at the center (or near the center) of the heat spreader 2, so that the effect of stress relaxation widely affects the joining surface between the heat spreader 2 and the cooler 3, and it is possible to relax the thermal interference between the semiconductor elements 1. In FIG. 7, each groove 4 reaches the end of the heat spreader 2, but this is just one example, and each groove 4 does not have to reach the end of the heat spreader 2 as shown in FIG.

[0023] As described above, the embodiment of the present invention has been described, but the description and drawings forming a part of this disclosure should not be understood as limiting this invention. From this disclosure, various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art. [Explanation of symbols]

[0024] 100 Semiconductor device, 1 Semiconductor element, 2 Heat spreader, 3 Cooler, 4 Groove, 10 Fin, 13 Groove bottom, 14 Opening

Claims

1. A semiconductor element; a heat spreader made of a highly thermally conductive material and bonded to the semiconductor element; a cooler joined to the heat spreader at a surface of the heat spreader opposite to a surface joined to the semiconductor element, the thermal conductivity of the heat spreader is greater than the thermal conductivity of the cooler; a groove is formed in the heat spreader, the groove opening at a joint surface between the heat spreader and the cooler; The shape of the joint surface between the heat spreader and the cooler is rectangular, At least one of imaginary extension lines extending along the longitudinal direction of the groove intersects with a surface forming a long side of the heat spreader. A semiconductor device comprising:

2. The cooler has a plurality of plate-shaped fins formed in the same direction as the long sides of the heat spreader.

2. The semiconductor device according to claim 1,

3. The groove is open to a surface that defines a long side of the heat spreader.

3. The semiconductor device according to claim 1, wherein the first insulating layer is a conductive layer.

4. The length of the groove bottom in the longitudinal direction of the groove is shorter than the length of the opening of the groove in the longitudinal direction and is shorter than the length of any side of the semiconductor element.

4. The semiconductor device according to claim 1, wherein the first insulating layer is a conductive layer.

5. The depth of the groove is shorter than the length from the bottom of the groove to the bonding surface between the semiconductor element and the heat spreader.

5. The semiconductor device according to claim 1, wherein the first insulating layer is a conductive layer.

6. The groove is formed in plurality.

6. The semiconductor device according to claim 1, wherein the first and second electrodes are electrically connected to each other.

7. The semiconductor element bonded to the heat spreader is provided in plurality, When the semiconductor elements and the grooves are projected onto a joint surface between the heat spreader and the cooler, the grooves are formed so as to separate the semiconductor elements.

7. The semiconductor device according to claim 6.

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