Semiconductor device and method of manufacturing the same

Abstract

To provide a technique capable of suppressing peeling between an insulating sheet and a heat sink in a semiconductor device.SOLUTION: The semiconductor device includes a heat sink 1, an insulating sheet 2 attached to heat sink 1, a frame 3 disposed on insulating sheet 2, a semiconductor element 4,5,6 mounted on frame 3, and a sealing material 8 sealing heat sink 1, insulating sheet 2, frame 3, and semiconductor element 4,5,6 with a surface of heat sink 1 opposite to a surface to which insulating sheet 2 is attached and a portion of frame 3 being exposed. An extension part 10 extending to the outer peripheral side is provided in a portion on the surface side to which the insulating sheet 2 is stuck in the side part of the heat sink 1, and at least two steps including a first step 11 recessed from the extension part 10 to the inner peripheral side and a second step 12 recessed further to the inner peripheral side are provided in the side part of the heat sink 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, in transfer mold type semiconductor devices having a structure in which an insulating sheet is attached to a heat sink, a step has been provided on the side of the heat sink opposite the side to which the insulating sheet is attached in order to firmly bond the heat sink and the sealing material and prevent moisture from entering (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-314004 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, the step can strengthen the adhesion between the sealing material and the side of the heat sink opposite to the side where the insulating sheet is attached, but if the sealing material peels off from the side of the heat sink, the peeling can progress during reliability tests, etc., and reach the interface between the insulating sheet and the heat sink, resulting in a problem of reduced insulation and heat dissipation performance of the semiconductor device.

[0005] Therefore, an object of the present disclosure is to provide a technique capable of suppressing peeling between an insulating sheet and a heat sink in a semiconductor device. [Means for solving the problem]

[0006] The semiconductor device according to the present disclosure comprises a heat sink, an insulating sheet attached to the heat sink, a frame placed on the insulating sheet, a semiconductor element mounted on the frame, and a sealing material that seals the heat sink, the insulating sheet, the frame, and the semiconductor element while exposing the surface of the heat sink opposite to the surface on which the insulating sheet is attached and a portion of the frame, wherein an extension portion extending outward from the side of the heat sink on the surface on which the insulating sheet is attached is provided, and the side of the heat sink has at least two steps, including a first step recessed from the extension portion toward the inner periphery and a second step recessed further toward the inner periphery. [Effects of the Invention]

[0007] According to the present disclosure, at least two steps provided on the side of the heat sink provide an anchoring effect, thereby suppressing peeling at the interface between the side of the heat sink and the sealing material. As a result, peeling between the insulating sheet and the heat sink can also be suppressed. Furthermore, even if peeling occurs between the heat sink and the sealing material, the extension portion increases the interfacial distance between the side of the heat sink and the sealing material, preventing the peeling from reaching the interface between the insulating sheet and the heat sink. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a semiconductor device according to a first embodiment. [Figure 2] 2 is an enlarged cross-sectional view showing a heat sink and its periphery provided in the semiconductor device according to the first embodiment. FIG. [Figure 3] 1 is a side view of a semiconductor device according to a first embodiment. [Figure 4] FIG. 10 is a side view of a semiconductor device according to a modified example of the first embodiment. [Figure 5] 1 is a side view illustrating a method for manufacturing a semiconductor device according to a first embodiment. [Figure 6]FIG. 10 is an enlarged cross-sectional view showing a heat sink and its periphery provided in the semiconductor device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] <First Embodiment> The first embodiment will be described below with reference to the drawings. Fig. 1 is a cross-sectional view of a semiconductor device according to the first embodiment. Fig. 2 is an enlarged cross-sectional view showing a heat sink 1 and its periphery provided in the semiconductor device according to the first embodiment.

[0010] As shown in FIG. 1, the semiconductor device is a transfer mold type IPM (Intelligent Power Module), and includes a heat sink 1, an insulating sheet 2, a frame 3, semiconductor elements 4, 5, and 6, and a sealing material 8.

[0011] As shown in FIG. 1, the frame 3 is formed in a plate shape and is placed on an insulating sheet 2 that is attached to the heat sink 1.

[0012] The semiconductor elements 4, 5, and 6 are mounted on the frame 3 via die bonding material (not shown). The semiconductor element 4 is an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The semiconductor element 5 is a diode. The semiconductor element 6 is a control IC (Integrated Circuit) that controls the operation of the semiconductor elements 4 and 5.

[0013] The material constituting the semiconductor elements 4, 5, and 6 is, for example, silicon (Si). Note that the material constituting the semiconductor elements 4, 5, and 6 is not limited to silicon and may be, for example, a wide bandgap semiconductor material such as silicon carbide (SiC), gallium nitride (GaN), or diamond (C).

[0014] The semiconductor element 4 and the semiconductor element 5 are electrically connected by a wire 7. The semiconductor element 4 and the semiconductor element 6 are electrically connected by a wire 7. Furthermore, the semiconductor elements 4, 5, and 6 are each electrically connected to the frame 3 by a wire 7. The wire 7 is made of, for example, aluminum (Al). Note that the wire 7 is not limited to aluminum, and may be made of copper (Cu), gold (Au), silver (Ag), or the like.

[0015] Semiconductor element 4 and semiconductor element 5 are power elements that generate heat when driven, and this heat is transferred to heat sink 1 via insulating sheet 2. Insulating sheet 2 contains silica (SiO2) or boron nitride (BN) as its primary material to provide heat dissipation and insulation. As shown in Figure 2, the optimal thickness t1 of insulating sheet 2 is set in consideration of heat dissipation, and is between 50 μm and 220 μm.

[0016] 1 and 2, the sealing material 8 is, for example, a mold resin. The sealing material 8 is formed by transfer molding, and seals the heat sink 1, the insulating sheet 2, the frame 3, and the semiconductor elements 4, 5, and 6, leaving the surface of the heat sink 1 opposite to the surface to which the insulating sheet 2 is attached and part of the frame 3 exposed. The heat sink 1, the insulating sheet 2, the frame 3, and the semiconductor elements 4, 5, and 6 are insulated by the sealing material 8, and the structure is such that the functions of the insulating sheet 2 and the sealing material 8 are not significantly reduced in reliability tests, mainly including heat cycle tests and humidity resistance tests.

[0017] Next, the structure of the heat sink 1 will be described. Fig. 3 is a side view of the semiconductor device according to the first embodiment. Fig. 4 is a side view of a semiconductor device according to a modified example of the first embodiment. In Figs. 3 and 4, in order to make the drawings easier to see, the semiconductor elements 4, 5, and 6, the wire 7, and the sealing material 8 are omitted, and the frame 3 is simplified.

[0018] The heat sink 1 is made of, for example, copper (Cu). As shown in Figures 1 to 3, an extension 10 extending outward is provided on the side of the heat sink 1 on the side where the insulating sheet 2 is attached. The provision of the extension 10 increases the interface distance between the side of the heat sink 1 and the sealing material 8, preventing peeling between the heat sink 1 and the sealing material 8 from reaching the interface between the insulating sheet 2 and the heat sink 1.

[0019] Furthermore, two steps, a first step 11 and a second step 12, are provided on the side of the heat sink 1. The first step 11 is a step recessed from the extension portion 10 toward the inner periphery. The second step 12 is a step recessed further toward the inner periphery from the first step 11. In other words, the second step 12 is a step recessed toward the inner periphery from the surface of the heat sink 1 opposite to the surface to which the insulating sheet 2 is attached.

[0020] The two steps provided on the side of the heat sink 1 provide an anchor effect, which prevents peeling at the interface between the side of the heat sink 1 and the sealing material 8, and also prevents peeling between the insulating sheet 2 and the heat sink 1. The number of steps is not limited to two, as long as it is at least two.

[0021] The extension portion 10 extends outward from the peripheral edge of the insulating sheet 2. As shown in Fig. 4, the extension portion 10 may not extend from the peripheral edge of the insulating sheet 2 to the peripheral edge, and the shape of the extension portion 10 in a top view may be the same as the shape of the insulating sheet 2 in a top view. In other words, the end face of the extension portion 10 and the end face of the insulating sheet 2 may be at the same position.

[0022] The thickness t2 of the extension portion 10 is equal to or greater than the thickness t1 of the insulating sheet 2 and equal to or less than 0.8 mm. As described above, the thickness t1 of the insulating sheet 2 is equal to or greater than 50 μm and equal to or less than 220 μm, and therefore the thickness t2 of the extension portion 10 is equal to or greater than 50 μm and equal to or less than 0.8 mm. By reducing the thickness t2 of the extension portion 10, when a difference occurs in the linear expansion coefficients of the sealing material 8 and the heat sink 1, the extension portion 10 can deform in the vertical direction and relieve stress.

[0023] Furthermore, in the past, the distance d from the end face of the frame 3 to the end face of the insulating sheet 2 was set large, assuming that the insulating sheet 2 and the heat sink 1 would peel off. However, in the first embodiment, the distance d from the end face of the frame 3 to the end face of the insulating sheet 2 is set small to prevent the insulating sheet 2 from peeling off from the heat sink 1. Specifically, the distance d from the end face of the frame 3 to the end face of the insulating sheet 2 is set to 1 mm or less.

[0024] Next, a brief description will be given of a method for manufacturing the semiconductor device according to the first embodiment. Fig. 5 is a side view for explaining the method for manufacturing the semiconductor device according to the first embodiment.

[0025] As shown in FIG. 5, a press die 20 is used to perform a stamping process on the surface of the heat sink 1 opposite to the surface on which the insulating sheet 2 is attached, thereby forming two steps, a first step 11 and a second step 12, in the heat sink 1. This press process also simultaneously forms an extension 10. Next, although not shown, the insulating sheet 2 and the heat sink 1 after the press process are attached to produce an integrated heat sink with an insulating sheet. A frame 3 is placed on the heat sink with an insulating sheet, and semiconductor elements 4, 5, and 6 are mounted on the frame 3. Wire bonding is then performed, followed by transfer molding. Through these steps, the semiconductor device according to the first embodiment is completed. The steps formed by the press process are not limited to two steps, as long as they are at least two steps.

[0026] In a completed semiconductor device, stress occurs when heat is applied due to differences in the linear expansion coefficients of each component, and the device is designed to alleviate this stress. Among these, the insulating sheet 2 must ensure its insulating and heat dissipation functions. One of the causes of the loss of these functions is peeling between the insulating sheet 2 and the heat sink 1. This peeling occurs not only because of stress caused by differences in the linear expansion coefficients of each component, but also because peeling progresses at the interface between the side of the heat sink 1 and the sealing material 8, and it has been confirmed that this peeling reaches the interface between the insulating sheet 2 and the heat sink 1, causing them to separate.

[0027] Therefore, in the first embodiment, the semiconductor device includes a heat sink 1, an insulating sheet 2 attached to the heat sink 1, a frame 3 arranged on the insulating sheet 2, semiconductor elements 4, 5, and 6 mounted on the frame 3, and a sealant 8 that seals the heat sink 1, the insulating sheet 2, the frame 3, and the semiconductor elements 4, 5, and 6, with the surface of the heat sink 1 opposite to the surface to which the insulating sheet 2 is attached and part of the frame 3 exposed. An extension 10 extending outward is provided on the side of the heat sink 1 on the side to which the insulating sheet 2 is attached, and the side of the heat sink 1 is provided with at least two steps, including a first step 11 recessed inward from the extension 10 and a second step 12 recessed further inward.

[0028] Therefore, an anchor effect is obtained by the at least two steps provided on the side of the heat sink 1, which makes it possible to suppress peeling at the interface between the side of the heat sink 1 and the sealing material 8. As a result, peeling between the insulating sheet 2 and the heat sink 1 can also be suppressed. Even if peeling occurs between the heat sink 1 and the sealing material 8, the provision of the extension portion 10 increases the interfacial distance between the side of the heat sink 1 and the sealing material 8, which makes it possible to suppress the peeling from reaching the interface between the insulating sheet 2 and the heat sink 1.

[0029] Furthermore, by designing the insulating sheet 2 so that it is also placed on the extension portion 10 during the process of attaching the insulating sheet 2 to the heat sink 1, the extension portion 10 and the insulating sheet 2 can be pressed together with even greater force, thereby firmly adhering the periphery of the insulating sheet 2, which is prone to peeling.

[0030] Furthermore, insulating sheet 2 contains silica or boron nitride as a main material, and has a thickness t1 of 50 μm or more and 220 μm or less. Therefore, the necessary heat dissipation and insulation properties for insulating sheet 2 can be ensured, and adhesion to heat sink 1 can be improved.

[0031] Furthermore, the thickness t2 of the extension 10 of the heat sink 1 is equal to or greater than the thickness of the insulating sheet 2 and equal to or less than 0.8 mm, so that by reducing the thickness t2 of the extension 10, the extension 10 can deform in the vertical direction and relieve stress when a difference in the linear expansion coefficient occurs between the sealing material 8 and the heat sink 1. As a result, peeling of the extension 10 due to stress can be further suppressed.

[0032] Furthermore, the distance d from the end face of the frame 3 to the end face of the insulating sheet 2 is 1 mm or less. Therefore, the sizes of the heat sink 1 and the insulating sheet 2 can be reduced, leading to a reduction in component costs.

[0033] Furthermore, at least two steps are formed by performing a press process to punch out from the side of the heat sink 1 opposite to the side on which the insulating sheet 2 is attached, so that at least two steps can be easily formed.

[0034] <Embodiment 2> Next, a semiconductor device according to embodiment 2 will be described. Fig. 6 is an enlarged cross-sectional view showing a heat sink 1 and its periphery provided in the semiconductor device according to embodiment 2. Note that in embodiment 2, the same components as those described in embodiment 1 are denoted by the same reference numerals and description thereof will be omitted.

[0035] 6, in the second embodiment, the extension 10 of the heat sink 1 is bent in the opposite direction to the insulating sheet 2. Similarly, the portion of the insulating sheet 2 attached to the extension 10 is also bent in the same direction.

[0036] Therefore, as shown by the two-dot chain line in FIG. 6, even if the frame 3A of the different electrode is deformed and the distance between the frame 3A and the heat sink 1 becomes short, it is possible to prevent the two from being short-circuited.

[0037] It should be noted that the embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate.

[0038] Various aspects of the present disclosure are summarized below as appendices.

[0039] (Appendix 1) A heat sink; an insulating sheet attached to the heat sink; a frame disposed on the insulating sheet; a semiconductor element mounted on the frame; a sealing material that seals the heat sink, the insulating sheet, the frame, and the semiconductor element while exposing a surface of the heat sink opposite to a surface to which the insulating sheet is attached and a part of the frame; an extension portion extending outward from the side of the heat sink on the surface to which the insulating sheet is attached; The semiconductor device has at least two steps on the side of the heat sink, including a first step recessed from the extension toward the inner periphery and a second step recessed further toward the inner periphery.

[0040] (Appendix 2) 2. The semiconductor device according to claim 1, wherein the extending portion extends outward beyond the peripheral edge of the insulating sheet.

[0041] (Appendix 3) the insulating sheet contains silica or boron nitride as a main material; 3. The semiconductor device according to claim 1, wherein the insulating sheet has a thickness of 50 μm or more and 220 μm or less.

[0042] (Appendix 4) 4. The semiconductor device according to claim 3, wherein the thickness of the extension of the heat sink is equal to or greater than the thickness of the insulating sheet and is 0.8 mm or less.

[0043] (Appendix 5) 5. The semiconductor device according to claim 1, wherein the distance from the end face of the frame to the end face of the insulating sheet is 1 mm or less.

[0044] (Appendix 6) 5. The semiconductor device according to claim 4, wherein the extension of the heat sink is bent toward the opposite side to the insulating sheet.

[0045] (Appendix 7) A method for manufacturing a semiconductor device according to any one of Supplementary Note 1 to Supplementary Note 6, comprising: A method for manufacturing a semiconductor device, wherein the at least two steps are formed by performing a press work to punch out from the surface of the heat sink opposite to the surface to which the insulating sheet is attached. [Explanation of symbols]

[0046] 1 heat sink, 2 insulating sheet, 3 frame, 4, 5, 6 semiconductor element, 8 sealing material, 10 extension portion, 11 first step, 12 second step.

Claims

1. A heat sink; an insulating sheet attached to the heat sink; a frame disposed on the insulating sheet; a semiconductor element mounted on the frame; a sealing material that seals the heat sink, the insulating sheet, the frame, and the semiconductor element while exposing a surface of the heat sink opposite to a surface to which the insulating sheet is attached and a part of the frame; an extension portion extending outward from the side of the heat sink on the surface to which the insulating sheet is attached; The semiconductor device has at least two steps on the side of the heat sink, including a first step recessed from the extension toward the inner periphery and a second step recessed further toward the inner periphery.

2. The semiconductor device according to claim 1 , wherein the extending portion extends outward beyond a peripheral edge of the insulating sheet.

3. the insulating sheet contains silica or boron nitride as a main material; The semiconductor device according to claim 1 , wherein the insulating sheet has a thickness of 50 μm or more and 220 μm or less.

4. The semiconductor device according to claim 3 , wherein the thickness of the extension of the heat sink is equal to or greater than the thickness of the insulating sheet and is 0.8 mm or less.

5. 2. The semiconductor device according to claim 1, wherein the distance from the end face of said frame to the end face of said insulating sheet is 1 mm or less.

6. The semiconductor device according to claim 4 , wherein the extension of the heat sink is bent in a direction opposite to the insulating sheet.

7. A method for manufacturing the semiconductor device according to any one of claims 1 to 6, comprising: A method for manufacturing a semiconductor device, wherein the at least two steps are formed by performing a press work to punch out from the surface of the heat sink opposite to the surface to which the insulating sheet is attached.

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