Composite semiconductor device

Abstract

To provide a composite semiconductor device that can satisfactorily detect thermal deterioration of a bonding material using a sensor chip.SOLUTION: A composite semiconductor device 1 includes a support substrate 2, a laminated substrate 4 serving as a base on the support substrate, a bonding material 3 that bonds the support substrate and the base, a main semiconductor chip 5 arranged on the base, a sensor chip 6 placed on the base to detect thermal deterioration of the bonding material, and a region 7 that has lower thermal conductivity than the surrounding area in at least a part of the base from just below the mounting portion of the main semiconductor chip to just below the mounting portion of the sensor chip. The laminated substrate 4 includes a ceramic substrate 4a, a back side circuit board layer 4b on the back side of the ceramic substrate 4a, and a front side circuit board layer 4c on the front side of the ceramic substrate 4a.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] In a composite semiconductor device including a main semiconductor device and a sensor device on a common base, the sensor device relates to a composite semiconductor device having a function of detecting thermal degradation of a bonding material adhered to the base by temperature.

Background Art

[0002] A semiconductor device in which a main semiconductor device (main semiconductor chip) is mounted on a base such as a laminated ceramic substrate, and the base is bonded via a bonding material such as solder on a copper plate such as a lead frame is known. In a structure as shown in FIG. 5, in order to prevent thermal runaway or the like of the main semiconductor chip, a composite semiconductor device in which a sensor device (sensor chip) for detecting the temperature of the main semiconductor chip is mounted is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, a conventional composite semiconductor device including a sensor device is for detecting the temperature of the main semiconductor device with high precision. In such a composite semiconductor device, when cracks or the like progress in the bonding material for bonding the base, it may affect the thermal resistance of the main semiconductor device and cause problems such as the composite semiconductor device malfunctioning. However, it has been difficult to detect the thermal degradation of the bonding material before the thermal degradation affects the main semiconductor device.

[0005] Therefore, the problem to be solved by the invention is to provide a composite semiconductor device capable of detecting the thermal degradation of the bonding material well with a sensor device before thermal degradation occurs in the main semiconductor device.

Means for Solving the Problems

[0006] The composite semiconductor device of the present invention comprises a support substrate, a base on the support substrate, a bonding material for joining the support substrate and the base, a main semiconductor device disposed on the base, a sensor device disposed on the base for temperature detection of thermal degradation of the bonding material, and a base extending from directly below the mounting portion of the main semiconductor device to directly below the mounting portion of the sensor device. The inner surface or back surface A key feature is that at least a portion of it has lower thermal conductivity than its surroundings. [Effects of the Invention]

[0007] According to the present invention, by making at least a portion of the base from directly below the mounting area of ​​the main semiconductor device to directly below the mounting area of ​​the sensor device a region with low thermal conductivity, it is possible to provide a composite semiconductor device that can effectively detect thermal degradation of the bonding material with a sensor device. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing a composite semiconductor device according to Example 1 of the present invention. [Figure 2] This is a schematic cross-sectional view showing a composite semiconductor device according to Embodiment 1 of the present invention, and is a diagram showing a region with low thermal conductivity or a formation position of a film 7 with low thermal conductivity. [Figure 3] This figure conceptually illustrates the increase in thermal resistance when a crack propagates in the bonding material in the composite semiconductor device of Embodiment 1 of the present invention. [Figure 4] This is a schematic plan view showing a composite semiconductor device according to Embodiment 1 of the present invention. [Figure 5] This is a schematic diagram illustrating a conventional composite semiconductor device. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the present invention will be described in detail below with reference to the figures. However, the present invention is not limited in any way to the following description.

[0010] The composite semiconductor device of Example 1 will be described in detail with reference to the drawings. The drawings are schematic, and the relationships between thickness and dimensions, as well as the thickness and ratio of each layer, are examples only and do not limit the technical concept of the invention. Furthermore, the relationships between dimensions and ratios may differ between drawings. In the following description, when describing the positional relationships of components, terms such as "top," "bottom," "right," and "left" will be used as needed based on the orientation of the referenced drawing, but do not limit the technical concept of the invention. Also, terms such as "top," "bottom," "right," "left," "directly below," "front surface," and "back surface" may be used even if the components are not in contact. (Example 1)

[0011] A composite semiconductor device 1 according to Embodiment 1 of the present invention will be described. Figure 1 is a schematic cross-sectional view showing the composite semiconductor device 1. The composite semiconductor device 1 includes a support substrate 2 made of a metal frame such as a copper plate or an aluminum plate, or a circuit board. The base laminated substrate 4 includes a ceramic substrate 4a, a back circuit board layer 4b on the back surface of the ceramic substrate 4a, and a front circuit board layer 4c on the surface of the ceramic substrate 4a. The back circuit board layer 4b and the front circuit board layer 4c are made of copper, aluminum, or the like. The back circuit board layer 4b is joined to the upper surface of the support substrate 2 via a bonding material 3 such as solder. The bonding material 3 can be solder, a sintering agent using silver or copper, TLPS, or an adhesive in which metal particles are dispersed.

[0012] A main semiconductor device (main semiconductor chip) 5 and a sensor device (sensor chip) 6 are provided on the laminated substrate 4. The main semiconductor chip 5 is a heat-generating semiconductor chip, and power semiconductor chips such as diodes, MOSFETs, and IGBTs are used. The semiconductor material of the main semiconductor chip 5 is not limited to silicon; silicon carbide, gallium oxide, and gallium nitride-based materials may also be used. Furthermore, the main semiconductor chip 5 is preferably a vertical semiconductor device that conducts current in the vertical direction (the thickness direction of the semiconductor material), but it may also be a horizontal semiconductor device. In addition, the main semiconductor chip 5 has a larger chip size than the sensor chip 6. The sensor chip 6 has a function to detect temperature, and uses PN diodes, Schottky barrier diodes, thermistors, etc. In the case of PN diodes and Schottky barrier diodes, the semiconductor material is not limited to silicon, but may also be silicon carbide, gallium oxide, or gallium nitride-based materials. The main semiconductor chip 5 and the sensor chip 6 are joined to the laminated substrate 4 via a bonding material. The bonding material can be solder, a sintering agent using silver or copper, TLPS, or an adhesive with dispersed metal particles.

[0013] In the cross-sectional view of the composite semiconductor device 1 shown in Figure 1, the main semiconductor chip 5 and the sensor chip 6 are provided on the same surface circuit board layer 4c. In the cross-sectional view of the composite semiconductor device 1 in Figure 1, no gaps are formed in the back circuit board layer 4b or the front circuit board layer 4c that penetrate from the top to the bottom. The back circuit board layer 4b and the front circuit board layer 4c may be patterned so that gaps are formed in at least a portion of the back circuit board layer 4b or the front circuit board layer 4c when viewed planar from above. Alternatively, the front circuit board layer 4c may be divided into multiple front circuit board layers 4c, and the main semiconductor chip 5 and the sensor chip 6 may be bonded to different front circuit board layers 4c. Furthermore, if a gap in the back circuit board layer 4b is provided directly below a gap in the front circuit board layer 4c, stress concentration is likely to occur around the gap. Therefore, it is desirable to provide a gap in the back circuit board layer 4b at a location different from the gap in the front circuit board layer 4c. In addition, the width of the gap in the back circuit board layer 4b and the width of the gap in the front circuit board layer 4c may be made different. Furthermore, when the main semiconductor chip 5 and the sensor chip 6 are bonded to the laminated substrate 4 with bonding material during reflow soldering, or when the laminated substrate 4 is bonded to the support substrate 2 with bonding material 3, if the bonding material penetrates into the gaps provided in the back circuit board layer 4b, or if it does not penetrate, the thermal conductivity of the laminated substrate 4 will vary. This will result in variations in the accuracy of detecting the thermal degradation of the bonding material 3 with the sensor chip 6. Therefore, it is desirable that the main semiconductor chip 5 and the sensor chip 6 are formed on the same circuit board layer, without providing gaps that penetrate from the top to the bottom in the back circuit board layer 4b and the front circuit board layer 4c directly beneath the area between the main semiconductor chip 5 and the sensor chip 6, in order to detect the thermal degradation of the bonding material 3. For example, the back circuit board layer 4b may be a solid circuit board layer. Furthermore, although Figure 1 shows only one main semiconductor chip 5 and one sensor chip 6, multiple main semiconductor chips 5 and sensor chips 6 may be provided on the surface circuit board layer 4c. In addition, a sensor chip for detecting the operating temperature of the main semiconductor chip 5 and ambient temperature may be provided separately from the sensor chip 6, or the sensor chip 6 may also be provided with a function to detect ambient temperature.

[0014] From directly below the mounting area of ​​the main semiconductor chip 5 to directly below the mounting area of ​​the sensor chip 6, at least a portion of the base laminated substrate 4 is provided such that its thermal conductivity is lower than that of the surrounding area. This area obstructs heat dissipation from the sensor chip 6 to the area projected from that region. The area 7 with lower thermal conductivity than the surrounding area may be laser-treated on a predetermined surface of the back circuit board layer 4b, so that the back circuit board layer 4b is not bonded to the bonding material 3, or the thermal conductivity of the bond between the back circuit board layer 4b and the bonding material 3 is poor. As a result, the laser-treated area of ​​the back circuit board layer 4b has worse thermal conductivity than the untreated area of ​​the back circuit board layer 4b, obstructing heat dissipation downward from the laser-treated area of ​​the back circuit board layer 4b. Further, in the region 7 with low thermal conductivity, a chemical solution may be applied to a predetermined surface of the back surface circuit board layer 4b, and the back surface circuit board layer 4b may not be joined to the bonding material 3, or the thermal conductivity of the joint between the back surface circuit board layer 4b and the bonding material 3 may be deteriorated. Thereby, the region of the back surface circuit board layer 4b where the chemical solution is applied has lower thermal conductivity than the region where the chemical solution is not applied to the back surface circuit board layer 4b. Also, in the region 7 with lower thermal conductivity than the surroundings, plating treatment for improving the bonding with the bonding material may not be performed or a surface treatment for deliberately deteriorating the thermal conductivity of the bonding material may be performed as compared with other parts of the back surface circuit board layer 4b. Thereby, the plated region has lower thermal conductivity than the non-plated region. Further, the region 7 with lower thermal conductivity than the surroundings may be provided with a film having low thermal conductivity separately between the back surface circuit board layer 4b and the bonding material 3. For example, the film 7 having low thermal conductivity is formed by printing, applying a chemical solution, resin, etc. on a predetermined surface of the back surface circuit board layer 4b, and is a film made of a material with low thermal conductivity on the surface of a predetermined region of the back surface circuit board layer 4b as compared with other than the predetermined region of the back surface circuit board layer 4b. The film 7 having low thermal conductivity may be an oxide film, a resin film, or a metal film that is difficult to bond with the bonding material 3. The thickness of the region with low thermal conductivity and the film 7 having low thermal conductivity may be thinner than the thickness of the back surface circuit board layer 4b. By providing the region 7 with low thermal conductivity, the thermal resistance of that region can be increased, and the spread of heat downward in the thickness direction can be suppressed. The region 7 with lower thermal conductivity than the surroundings is provided on a predetermined surface of the back surface circuit board layer 4b in the semiconductor device 1 of FIG. 1. However, the region 7 with lower thermal conductivity than the surroundings may be provided in any one of or a plurality of regions selected from between the back surface circuit board layer 4b and the ceramic substrate 4a and between the front surface circuit board layer 4c and the ceramic substrate 4a from directly below the mounting portion of the main semiconductor chip 5 to directly below the mounting portion of the sensor chip 6.

[0015] An example of the operation of the composite semiconductor device 1 is described below. When the main semiconductor chip 5 is in the off state, the sensor chip 6 is turned on to detect the temperature of the sensor chip 6. When a crack in the bonding material 3 progresses to the vicinity of the sensor chip 6, the temperature of the sensor chip 6 in the composite semiconductor device 1 rises to a temperature higher than expected compared to conventional composite semiconductor devices. Therefore, it is possible to detect that thermal degradation such as cracks are occurring in the bonding material 3 around the sensor chip 6. Then, before the thermal resistance of the main semiconductor chip 5 is significantly affected and the composite semiconductor device fails, a signal is issued to stop the operation of the main semiconductor chip 5, thereby suppressing abnormal operation of the main semiconductor chip 5 due to thermal degradation of the bonding material 3.

[0016] In Figure 2, the region with low thermal conductivity or the film 7 with low thermal conductivity is formed in at least a portion of the laminated substrate 4, from the sensor chip 6 mounting area to the interface between the back circuit board layer 4b and the bonding material 3 or its extension, by drawing an auxiliary line (dotted line GJ) at a 45-degree angle in the thickness direction of the semiconductor device, and from the intersection of the interface between the back circuit board layer 4b and the bonding material 3 or its extension, to the intersection of the interface between the back circuit board layer 4b and the bonding material 3 or its extension. Furthermore, the region with low thermal conductivity or the film 7 with low thermal conductivity is formed in the region of the laminated substrate 4 on the sensor chip 6 side (to the right of the dotted line HF in the plane of Figure 2) of the intersection of the interface between the back circuit board layer 4b and the bonding material 3 or its extension, as indicated by drawing an auxiliary line (dotted line HF) at a 45-degree angle in the thickness direction of the semiconductor device from the mounting area of ​​the main semiconductor chip 5. The sensor chip 6 is turned on to detect the thermal degradation of the bonding material 3. However, the thermal degradation of the bonding material 3 can be detected effectively while suppressing the spread of heat by the sensor chip 6 in areas with low thermal conductivity or in a diagonally downward direction far from the film 7 with low thermal conductivity. Further, the low thermal conductivity region or the low thermal conductivity film 7 draws an auxiliary line at an angle of 45 degrees in the thickness direction of the semiconductor device from the mounting portion of the main semiconductor chip 5, and from the intersection of the interface between the back surface circuit board layer 4b and the bonding material 3 or its extension line to the back surface circuit board layer 4b directly below the mounting portion of the sensor chip 6. It is desirable to be formed in the region up to the interface between the bonding material 3 and its extension line. In this case, while reducing the suppression of the heat flow of the main semiconductor chip 5 due to the provision of the low thermal conductivity region or the low thermal conductivity film 7, the thermal degradation of the bonding material 3 can be detected well by the sensor chip 6.

[0017] For example, FIG. 3 is a diagram conceptually showing the increase in thermal resistance with respect to the progress of cracks. Here, points K, G, and F indicate that cracks have progressed to each location of the composite semiconductor device 1 in FIG. 2. Note that FIG. 3 is a conceptually shown diagram, and although it shows that the line is bent at points K and G, it also includes cases where it does not bend at points K and G but changes smoothly. The solid line indicates the increase in the thermal resistance of the sensor chip 6, and the dotted line indicates the increase in the thermal resistance of the main semiconductor chip 5. As shown in FIG. 3, until the crack occurring in the bonding material 3 reaches point K directly below the sensor chip 6, the slope of the thermal resistance increases gently. Until the crack occurring in the bonding material 3 further progresses from point K directly below the sensor chip 6 and reaches point G, the slope of the thermal resistance increases more rapidly than until point K. Then, when the crack occurring in the bonding material 3 exceeds point G, the slope of the thermal resistance becomes gentle, and when the crack occurring in the bonding material 3 exceeds point F, the thermal resistance of the main semiconductor chip 5 also begins to increase. For example, by detecting that the thermal resistance changes gently beyond point G, a signal can be transmitted before the influence of the thermal resistance of the main semiconductor chip 5 due to thermal degradation such as cracks occurs. Figure 4 is a schematic plan view of the semiconductor device 1 as seen from above. The mounting area for the main semiconductor chip 5 is located on the central side of the laminated substrate 4, and the mounting area for the sensor chip 6 is located on the corner side of the laminated substrate 4. A region or film 7 with low thermal conductivity is formed at least between the mounting area for the main semiconductor chip 5 and the mounting area for the sensor chip 6. It is desirable that the region or film 7 with low thermal conductivity extends to an area that is hidden by the projection of the region or film 7 with low thermal conductivity when viewed from the sensor chip 6. For example, as shown in Figure 4, the region or film 7 with low thermal conductivity is formed in an L-shape when viewed from above, along the surface of the sensor chip 6 facing the main semiconductor chip 5. Thermal degradation such as cracks in the bonding material 3 is more likely to occur from the corner side of the semiconductor device 1. Therefore, by placing the main semiconductor chip 5 in the center of the semiconductor device 1 and placing multiple sensor chips 6 in the corner side of the composite semiconductor device 1, temperature changes of the sensor chips 6 can be detected before thermal degradation such as cracks reaches the center of the composite semiconductor device 1. By detecting this, the operation of the main semiconductor chip 5 can be stopped before the crack 8 progresses to the area of ​​the bonding material 3 directly beneath the mounting area of ​​the main semiconductor chip 5, significantly affecting the thermal resistance of the main semiconductor chip 5 and causing the composite semiconductor device 1 to fail. This prevents abnormal operation of the main semiconductor chip 5 due to thermal degradation of the bonding material 3. [Explanation of Symbols]

[0018] 1. Composite semiconductor device 2. Support substrate 3 Bonding material 4. Multilayer substrate 5. Main semiconductor chip 6 Sensor chips 7. Regions or films with low thermal conductivity 8 cracks

Claims

1. Support substrate and The base on the support substrate, A joining material for joining the support substrate and the base, A main semiconductor chip placed on the aforementioned base, A sensor chip is placed on the base and detects the thermal degradation of the bonding material by temperature. A composite semiconductor device characterized by having a region with lower thermal conductivity than the surrounding area in at least a portion of the inner or back surface of the base, extending from directly below the mounting portion of the main semiconductor chip to directly below the mounting portion of the sensor chip.

2. A support substrate and The base on the support substrate, A joining material for joining the support substrate and the base, A main semiconductor chip placed on the aforementioned base, A sensor chip is placed on the base and detects the thermal degradation of the bonding material by temperature. The base includes at least a portion of the area from directly below the mounting area for the main semiconductor chip to directly below the mounting area for the sensor chip, with a region having lower thermal conductivity than the surrounding area. The previous base is Ceramic substrate and The back side circuit board layer on the back side of the ceramic substrate and The ceramic substrate includes a surface circuit substrate layer on the surface side of the ceramic substrate, In the region with low thermal conductivity, a film with low thermal conductivity is formed on the back circuit board layer by laser treatment or chemical treatment. A composite semiconductor device characterized in that the low thermal conductivity of the film is lower than that of the back-side circuit board layer.

3. The composite semiconductor device according to claim 2, characterized in that the low thermal conductivity film is selected from at least one of an oxide film, a resin film, or a metal film that is difficult to bond with the bonding material.

4. Viewed in two dimensions, The mounting portion for the sensor chip is located on the corner side of the base. The composite semiconductor device according to claim 1, characterized in that the mounting portion for the main semiconductor chip is located on the central side of the base.

5. The composite semiconductor device according to claim 2, characterized in that the region with low thermal conductivity is provided in at least a portion of the region from the intersection of a line drawn at a 45-degree angle in the thickness direction from the mounting portion of the sensor chip to the back circuit board layer or its extension, to the back circuit board layer or its extension directly beneath the mounting portion of the sensor chip.

6. In the off state of the main semiconductor chip, The aforementioned sensor chip generates heat, The composite semiconductor device according to any one of claims 1 to 5, characterized in that thermal degradation of the bonding material is detected by the temperature detected by the sensor chip.

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