Semiconductor device and its manufacturing method

Abstract

In the present invention, a porous SiC (2) is impregnated with a metal including Al as a main component. A circuit pattern (4) is disposed on a ceramic substrate (3). A semiconductor chip (5) is joined to the circuit pattern (4). The porous SiC (2) has a holder (7) for holding the ceramic substrate (3).

Description

[Technical field]

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

[0002] As semiconductor chips operate at higher temperatures, the temperature of the entire module rises, raising concerns about the impact of temperature changes on the module's lifespan. In particular, solder joints are susceptible to such effects, which is a major constraint on the module's lifespan. In recent years, Ag- and Cu-based bonding materials, which have higher heat cycle resistance than solder, have been developed. However, while the application of small-area bonding of chips and the like has progressed, it is difficult to ensure bonding reliability for large-area bonding of insulating substrates and the like. In addition, Ag- and Cu-based bonding materials are more expensive than solder, and are not suitable for use over a large area. In response to this, a base plate has been proposed in which porous SiC is impregnated with Al by pressure and molded integrally with an insulating substrate (see, for example, Patent Document 1), but this has not yet been put to practical use. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-297988 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the upper surface of the ceramic substrate and the upper surface of the porous SiC are made to be at the same height, and aluminum foil is provided to cover both and hold the ceramic substrate. However, the need to provide the aluminum foil increases manufacturing costs. In addition, the need to make the upper surfaces of the ceramic substrate and the porous SiC at the same height limits design freedom.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a semiconductor device and a manufacturing method thereof that have a high degree of design freedom and can reduce manufacturing costs. [Means for solving the problem]

[0006] The semiconductor device according to the present disclosure includes porous SiC impregnated with a metal mainly composed of Al, a ceramic substrate, a circuit pattern provided on the ceramic substrate, and a semiconductor chip bonded to the circuit pattern, the porous SiC having a holding portion for holding the ceramic substrate. The holding portion is hook-shaped. It is characterized by: Effect of the Invention

[0007] In the present disclosure, the shape of the porous SiC is devised to provide a holder for holding the ceramic substrate. Therefore, there is no need to provide an aluminum foil for holding the ceramic substrate, which reduces manufacturing costs. In addition, there is no need to make the height of the upper surface of the ceramic substrate and the upper surface of the porous SiC the same, which allows for greater design freedom. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a semiconductor device according to a first embodiment. [Diagram 2] 1 is a top view showing a semiconductor device according to a first embodiment. [Diagram 3] 2A to 2C are diagrams for explaining a method for manufacturing the semiconductor device according to the first embodiment. [Figure 4] FIG. 11 is a top view showing a semiconductor device according to a second embodiment. [Diagram 5] FIG. 11 is a cross-sectional view showing a semiconductor device according to a third embodiment. [Figure 6] FIG. 11 is a cross-sectional view showing a semiconductor device according to a fourth embodiment. [Figure 7] FIG. 13 is a top view showing a semiconductor device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A semiconductor device and a manufacturing method thereof according to an embodiment will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repeated description may be omitted.

[0010] Embodiment 1 FIG 1 is a cross-sectional view showing a semiconductor device according to a first embodiment. FIG 2 is a top view showing the semiconductor device according to the first embodiment. This semiconductor device is a power module. The integrated base plate 1 has porous SiC 2 impregnated with a metal mainly composed of Al, a ceramic substrate 3, and a circuit pattern 4 provided on the ceramic substrate 3. The porous SiC 2 has a holding portion 7 that holds the ceramic substrate 3. The holding portion 7 surrounds the entire outer periphery of the ceramic substrate 3 to hold the ceramic substrate 3.

[0011] The thickness of the integrated base plate 1 is, for example, 3 mm or more and 8 mm or less. The integrated base plate 1 has high heat dissipation properties, which are mainly due to the ceramic substrate 3. The ceramic substrate 3 is made of, for example, alumina (Al2O3), aluminum nitride (AlN), silicon nitride (SiN), or the like.

[0012] The semiconductor chip 5 is bonded to the circuit pattern 4 by a bonding material 6 such as a solder material, an Ag sintered material, or a Cu sintered material. The semiconductor chip 5 is, for example, a Si IGBT and diode, or a SiC MOSFET and SBD. The upper electrodes of the semiconductor chip 5 are electrically connected to terminals (not shown) by wires (not shown). An exterior case may be attached to the integrated base plate 1. Furthermore, the interior of the exterior case may be sealed with a sealing resin.

[0013] Next, a method for manufacturing the semiconductor device of this embodiment will be described. Fig. 3 is a diagram for explaining the method for manufacturing the semiconductor device according to the first embodiment. First, SiC (slurry) is cast and sintered to form porous SiC2, which is then machined to form the holding portion 7. Alternatively, a 3D printer may be used to form the porous SiC2 having the holding portion 7. Next, the ceramic substrate 3 is held by the holding portion 7 of the molded porous SiC2.

[0014] Next, the porous SiC 2 with the ceramic substrate 3 attached is placed in a mold 8 having the shape of the integrated base plate 1. For example, a metal 9 mainly composed of Al is impregnated into the porous SiC 2 by non-pressure impregnation, pressure impregnation, die casting, or the like. Next, the metal 9 remaining on the upper surface of the ceramic substrate 3 is etched to form a circuit pattern 4. Thereafter, a semiconductor chip 5 is bonded to the circuit pattern 4 with a bonding material 6, and wire bonding or the like is performed.

[0015] Conventionally, the upper surface of the ceramic substrate and the upper surface of the porous SiC are made to be at the same height, and aluminum foil is provided to cover both to hold the ceramic substrate. In contrast, in this embodiment, the shape of the porous SiC 2 is devised to provide a holder 7 for holding the ceramic substrate 3. This eliminates the need to provide aluminum foil to hold the ceramic substrate 3, thereby reducing manufacturing costs. In addition, there is a high degree of freedom in design, as there is no need to make the upper surfaces of the ceramic substrate 3 and the porous SiC 2 at the same height.

[0016] Furthermore, the ceramic substrate 3 and the base plate are integrated without soldering. The integrated base plate 1 has high heat dissipation properties, so that heat cycle resistance and high heat dissipation can be achieved.

[0017] It is also preferable to use pressureless impregnation when impregnating the porous SiC2 with a metal. Pressureless impregnation can simplify the process compared to impregnation using pressure. After impregnating the porous SiC2 with the metal 9, the metal 9 on the ceramic substrate 3 is etched to form the circuit pattern 4. This simplifies the process and reduces manufacturing costs.

[0018] Embodiment 2 4 is a top view showing a semiconductor device according to embodiment 2. The ceramic substrate 3 is rectangular in plan view. The porous SiC 2 has holding portions 7 that contact the side surfaces of the ceramic substrate 3 at three or more points to hold the ceramic substrate 3. The holding portions 7 each hold three different sides of the rectangular ceramic substrate 3. The ceramic substrate 3 is inserted into the holding portions 7 from a portion where the holding portions 7 are not provided.

[0019] The position of the ceramic substrate 3 is determined by the three or more holding parts 7. In addition, stress on the ceramic substrate 3 can be alleviated. Furthermore, compared to the first embodiment in which the porous SiC2 contacts the entire side surface of the ceramic substrate, it is possible to reduce the amount of raw material, and the manufacturing cost can be reduced especially when the porous SiC2 is formed by 3D printing. The other configurations and effects are the same as those of the first embodiment.

[0020] Embodiment 3 5 is a cross-sectional view showing a semiconductor device according to the third embodiment. The porous SiC 2 has a hook-shaped holding portion 7 that holds the ceramic substrate 3. The hook-shaped holding portion 7 is provided so as to embrace the side and top surfaces of the ceramic substrate 3. This makes it possible to prevent the ceramic substrate 3 from shifting during impregnation. This makes it possible to ensure a process margin during impregnation and improve productivity. The other configurations and effects are the same as those of the second embodiment.

[0021] Embodiment 4 6 is a cross-sectional view showing a semiconductor device according to embodiment 4. The holding parts 7 are provided so as to respectively hold three different sides of the ceramic substrate 3. The side of the ceramic substrate 3 on which the holding part 7 is not provided serves as the gate side for supplying the metal 9 during impregnation. This makes it possible to position and hold the ceramic substrate 3 while ensuring the fluidity of the metal 9 from the gate side. The other configurations and effects are the same as those of embodiment 3.

[0022] Embodiment 5. FIG. 7 is a top view showing a semiconductor device according to a fifth embodiment. In the first embodiment, only one large ceramic substrate 3 is used, but in the present embodiment, the ceramic substrate 3 is divided into two or more substrates. The porous SiC 2 holds the two or more divided ceramic substrates 3. By using individual ceramic substrates, which are less expensive than a large ceramic substrate, the manufacturing cost can be reduced. In addition, the stress on the ceramic substrate 3 can be alleviated. The other configurations and effects are the same as those of the first embodiment.

[0023] The semiconductor chip 5 is not limited to those made of silicon, but may be made of a wide band gap semiconductor having a larger band gap than silicon. The wide band gap semiconductor is, for example, silicon carbide, gallium nitride-based material, or diamond. A semiconductor chip made of such a wide band gap semiconductor has high voltage resistance and allowable current density, so it can be miniaturized. By using this miniaturized semiconductor chip, a semiconductor device incorporating this semiconductor chip can also be miniaturized and highly integrated. In addition, since the semiconductor chip has high heat resistance, the heat dissipation fins of the heat sink can be miniaturized, and the water-cooled part can be air-cooled, so the semiconductor device can be further miniaturized. In addition, since the power loss of the semiconductor chip is low and highly efficient, the semiconductor device can be highly efficient. [Explanation of symbols]

[0024] 2 porous SiC, 3 ceramic substrate, 4 circuit pattern, 5 semiconductor chip, 7 holding portion, 9 metal

Claims

1. Porous SiC impregnated with a metal mainly composed of Al; A ceramic substrate; a circuit pattern provided on the ceramic substrate; a semiconductor chip bonded to the circuit pattern, the porous SiC has a holding portion for holding the ceramic substrate, The semiconductor device, wherein the holding portion is hook-shaped.

2. 2. The semiconductor device according to claim 1, wherein the holding portion holds the ceramic substrate by surrounding the entire outer periphery of the ceramic substrate.

3. 2. The semiconductor device according to claim 1, wherein the holding portion holds the ceramic substrate by contacting the side surface of the ceramic substrate at three or more points.

4. The ceramic substrate is rectangular in plan view, 4. The semiconductor device according to claim 3, wherein the holding portions respectively hold three different sides of the ceramic substrate.

5. 5. The semiconductor device according to claim 1, wherein the ceramic substrate is divided into two or more pieces.

6. 6. The semiconductor device according to claim 1, wherein the semiconductor chip is made of a wide band gap semiconductor.

7. forming a porous SiC having a retaining portion; a step of holding the ceramic substrate on the holding part; impregnating the porous SiC with a metal mainly composed of Al; after impregnating the porous SiC with the metal, etching the remaining metal on the top surface of the ceramic substrate to form a circuit pattern; and bonding a semiconductor chip to the circuit pattern. A method for manufacturing a semiconductor device, comprising the steps of: impregnating the porous SiC with the metal without applying pressure;

8. A step of forming porous SiC having a retaining portion; a step of holding the ceramic substrate on the holding part; impregnating the porous SiC with a metal mainly composed of Al; after impregnating the porous SiC with the metal, etching the remaining metal on the top surface of the ceramic substrate to form a circuit pattern; and bonding a semiconductor chip to the circuit pattern. A method for manufacturing a semiconductor device, comprising: forming a sprue side of the ceramic substrate on which the holding portion is not provided, the sprue side through which the metal is supplied during impregnation.

9. 9. The method for manufacturing a semiconductor device according to claim 7, wherein the holding portion is formed by cutting the porous SiC.

10. The method for manufacturing a semiconductor device according to claim 7 or 8, characterized in that the porous SiC having the holding portion is formed by a 3D printer.

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