Semiconductor device and method for manufacturing a semiconductor device

Abstract

Semiconductor device comprising: - a metal base (1); - an insulating substrate (2) arranged on the metal base (1); - a semiconductor element (4) mounted on the insulating substrate (2); and - a housing (7a) bonded to the metal base (1) such that it surrounds lateral surfaces of the insulating substrate (2) and the semiconductor element (4), wherein: - a pair of first metal oxide films (8) having a projecting shape is arranged on a peripheral edge region of the metal base (1); and - the housing (7a) is bonded to the metal base (1) by an adhesive (5) arranged in a region between the first metal oxide films (8).

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

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

[0002] To achieve high current density and high reliability, a conventional semiconductor device is used with a structure in which a lead electrode, arranged in a package, is bonded to semiconductor elements mounted on a metal-based insulating substrate using a bonding material such as solder. In such a semiconductor device, a sealing resin is filled into the interior of the package to protect the interior from external environments such as moisture, ensuring high dielectric strength and high reliability.

[0003] In the published Japanese patent application No. 2000-323593, a technique is further disclosed in which a recess is formed in a heat-radiating plate (corresponding to a metal base) to serve as an adhesive reservoir, and an adhesive layer is formed to a partially thick thickness when a sealing housing (corresponding to a casing) is bonded to the heat-radiating plate to improve the airtightness of a semiconductor device.

[0004] In conventional semiconductor devices, during the bonding process of the package to the metal base, the adhesive spreads in a wet state (wet-spreading) if, after application, it takes a long time for the package to bond firmly to the metal base via the adhesive. If the package is bonded to the metal base via the adhesive while the adhesive is spreading in a wet state, the adhesive spreads below the lower surface of the metal base, reducing its vertical position. Consequently, the adhesive's vertical position, necessary to fill the gap between the package and the metal base caused by the corrugation or waviness of the metal base, or by the shape difference between the package and the metal base, is not guaranteed.

[0005] Even in the technique described in the disclosed Japanese patent application No. 2000-323593, although the adhesive layer is made partially thick by providing a recess in the heat-radiating plate to serve as an adhesive reservoir, the vertical position of the adhesive is not guaranteed. SUMMARY

[0006] One objective of the present disclosure is to provide a technique that can suppress spreading of an adhesive in a wet state, which is used to bond a housing and a metal base together, and ensure the vertical position of the adhesive required to fill a gap created between the housing and the metal base.

[0007] The semiconductor device according to the present disclosure comprises a metal base, an insulating substrate, a semiconductor element, and a housing. The insulating substrate is arranged on the metal base. The semiconductor element is mounted on the insulating substrate. The housing is bonded to the metal base such that it surrounds the lateral surfaces of the insulating substrate and the semiconductor element. A pair of first metal oxide films with a raised or projecting shape is arranged on a peripheral edge region of the metal base. The housing is bonded to the metal base by an adhesive located in a region between the first metal oxide films in the pair.

[0008] The adhesive used to bond the housing to the metal base is blocked by the pair of first metal oxide films; therefore, it is prevented from spreading when wet. Consequently, the adhesive's height, required to fill the gap between the housing and the metal base, is maintained.

[0009] These and other tasks, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when it is taken in conjunction with the accompanying drawings. List of characters Fig. Figure 1 is a cross-sectional view of a semiconductor device according to the first embodiment; Fig. Figure 2 is a top view illustrating a state prior to bonding a package in the semiconductor device according to the first embodiment; Fig. Figure 3 is a cross-sectional view to illustrate an assembly procedure of the semiconductor device according to the first embodiment; Fig. Figure 4 is a cross-sectional view to illustrate an assembly procedure of the semiconductor device according to the first embodiment; Fig. Figure 5 is a cross-sectional view to illustrate an assembly procedure of the semiconductor device according to the first embodiment; Fig. Figure 6 is a top view illustrating a state prior to bonding the housing in a semiconductor device according to the second embodiment; Fig. Figure 7 is a cross-sectional view illustrating the state before bonding the package in the semiconductor device according to the second embodiment; and Fig. Figure 8 is a top view illustrating a state prior to bonding the housing in a semiconductor device according to the third embodiment. DESCRIPTION OF PREFERRED EXECUTION FORMS<Erste Ausführungsform>

[0010] The first embodiment will now be described with reference to the drawings. Fig. Figure 1 is a cross-sectional view of a semiconductor device according to the first embodiment. Fig. Figure 2 is a top view illustrating a state prior to bonding a housing 7a in the semiconductor device according to the first embodiment.

[0011] As in Fig. As illustrated in Figure 1, the semiconductor device comprises a metal base 1, an insulating substrate 2, a plurality of semiconductor elements 4, a housing 7a, a lead electrode 7b, a pair of metal oxide films 8 (corresponding to a first metal oxide film), an adhesive 5 and a sealing resin 6.

[0012] As in Fig. As illustrated in Figure 2, the metal base 1, made of a metal such as aluminum, is rectangular in shape when viewed from above. Fig. 1 and Fig. As illustrated in Figure 2, the insulating substrate 2 is rectangular in plan view and arranged on the metal base 1. Specifically, the insulating substrate 2 is located in an area on the upper surface of the metal base 1, excluding the peripheral edge region.

[0013] The insulating substrate 2 comprises an insulating layer 2a, a circuit structure 2b arranged on the lower surface of the insulating layer 2a, and a circuit structure 2c arranged on the upper surface of the insulating layer 2a. The insulating layer 2a consists of a ceramic such as aluminum nitride and silicon nitride or a resin. The circuit structures 2b and 2c consist of a metal such as copper.

[0014] The semiconductor elements 4 are mounted on the insulating substrate 2. Specifically, the semiconductor elements 4 are bonded to the upper surface of the circuit structure 2c by means of a bonding material 3b, such as solder. Typically, the semiconductor element 4 is an insulated-gate bipolar transistor (IGBT), a diode, or a reverse-conducting IGBT made of a silicon material. A metal-oxide-semiconductor field-effect transistor (MOSFET) made of a silicon carbide material or a Schottky barrier diode can also be used as the semiconductor element 4.

[0015] Although in Fig. Figure 2 illustrates six semiconductor elements 4. However, the number of semiconductor elements 4 is not limited, and a required number of semiconductor elements 4 can be mounted according to the application of a semiconductor device. Furthermore, a variety of semiconductor element types 4 can be mounted.

[0016] As in Fig. As illustrated in Figure 1, the housing 7a consists of a resin and, in plan view, is formed in a rectangular frame shape. The housing 7a is bonded to the peripheral edge region on the upper surface of the metal base 1 by means of the adhesive 5. The lead electrode 7b is integrally formed with the housing 7a by insert molding. One end face of the lead electrode 7b is located on the upper surface of the housing 7a and connected to an external device (not illustrated). The other end face of the lead electrode 7b extends into the interior of the housing 7a and is bonded to the plurality of semiconductor elements 4 by means of a bonding material 3a, such as solder.

[0017] The sealing resin 6 seals the interior of the housing 7a to protect the insulating substrate 2 and the multitude of semiconductor elements 4 from the external environment, such as moisture. Note that in Fig. 1 The semiconductor device is illustrated in a simplified manner, and the metal wires and signal connections associated with the plurality of semiconductor elements 4 are not shown. Furthermore, heat-radiating fins and the like may be attached to the lower surface of the metal base 1.

[0018] Next, the pair of metal oxide films 8, which is a feature of the first embodiment, will be described. As in Fig. 1 and Fig. As illustrated in Figure 2, the pair of metal oxide films 8 is formed in a raised or projecting shape that extends upwards and is arranged on the peripheral edge region on the upper surface of the metal base 1. Specifically, the pair of metal oxide films 8 extends continuously along a line along the peripheral edge region on the upper surface of the metal base 1. The width of the pair of metal oxide films 8 is also constant.

[0019] The adhesive 5, used to bond the housing 7a to the metal base 1, is also applied continuously in a line along the peripheral edge region on the upper surface of the metal base 1 and is located in the area between the pair of metal oxide films 8. The adhesive 5 is a silicone-based or epoxy-based adhesive. The adhesive 5 is surrounded by the pair of metal oxide films 8; therefore, the adhesive 5 is prevented from spreading outwards from the area between the metal oxide films 8 in the pair when wet.

[0020] The pair of metal oxide films 8 is formed using a laser processing device, such as a fiber laser, prior to the application of the adhesive 5. In this case, the conditions, such as wavelength and frequency, in the laser processing device are those for forming the metal oxide on the metal base 1, and not those for melting or vaporizing the metal on the metal base 1. By performing processing under these conditions using the laser processing device, a pair of metal oxide films 8 with a protruding shape is formed. The pair of metal oxide films 8 can also be formed by a method other than laser processing.

[0021] In experiments, the inventors found that the spreading of the adhesive 5 in the wet state over time after application can be suppressed if the adhesive 5 is a silicone-based adhesive with a viscosity of, for example, about 150 Pa s and the adhesive 5 is controlled to have a width of about 1 mm and a height of about 1 mm, and if the height of the pair of metal oxide films 8 is 0.02 mm or more. The above description shows that the pair of metal oxide films 8 is formed continuously in a linear form along the peripheral edge region on the upper surface of the metal base 1; however, the formation of the pair of metal oxide films 8 is not limited to this and can be discontinuous along the peripheral edge region on the upper surface of the metal base 1.

[0022] Next, with reference to Fig. 3 to Fig. 5 describes the procedure for assembling or mounting the semiconductor device according to the first embodiment. Fig. 3 to Fig. Figure 5 shows cross-sectional views to illustrate an assembly procedure of the semiconductor device according to the first embodiment.

[0023] As in Fig. As illustrated in Figure 3, the insulating substrate 2 is bonded to the upper surface of the metal base 1, and a variety of semiconductor elements 4 are bonded to the upper surface of the insulating substrate 2 by the bonding material 3b. A solder metal is used as the bonding material 3b. Soldering is carried out by heating the solder metal to a temperature exceeding its melting point.

[0024] When paste-like solder is used as the bonding material 3b, the paste-like solder is printed onto the top surface of the insulating substrate 2. When sheet-like solder is used as the bonding material 3a, the sheet-like solder is placed on the top surface of the insulating substrate 2.

[0025] Next, a pair of metal oxide films 8 are formed on the peripheral edge region of the upper surface of the metal base 1 using the laser processing device. Along with the formation of the pair of metal oxide films 8, a control number for individual product identification can be laser-printed onto the upper surface of the metal base 1.

[0026] Next, the adhesive 5 is applied to the area between the metal oxide films 8 in the pair to bond the housing 7a, which is fitted with the lead electrode 7b, to the metal base 1. After the adhesive 5 is applied, if the time until the housing 7a is firmly bonded to the metal base 1 via the adhesive 5 is long, the adhesive 5 tends to spread when wet; however, the pair of metal oxide films 8 blocks the adhesive 5 and prevents it from spreading outwards from the area when wet.

[0027] As in Fig. 4 and Fig. As illustrated in Figure 5, the housing 7a is bonded to the upper surface of the metal base 1 in a state in which it is firmly bonded to the adhesive 5 applied to the upper surface of the metal base 1. As shown in Figure 5, the housing 7a is bonded to the upper surface of the metal base 1 in a state in which it is firmly bonded to the adhesive 5 applied to the upper surface of the metal base 1. Fig. As illustrated in Figure 4, if the height position of the adhesive 5 is higher than the height position of the pair of metal oxide films 8, the adhesive 5 can remain around the pair of metal oxide films 8 and be prevented from spreading below the lower surface of the metal base 1, even though the adhesive 5 is pressed and spreads when the housing 7a is firmly bonded to the metal base 1 over the adhesive 5.

[0028] The housing 7a can be firmly bonded to the upper surface of the metal base 1 by applying suitable pressure using a holding or clamping device or the like. After the housing 7a is firmly bonded to the metal base 1, heating can be carried out, if necessary, to cure the adhesive 5.

[0029] As in Fig. As illustrated in Figure 5, the other end of the lead electrode 7b is bonded to the upper surface of the plurality of semiconductor elements 4 by the bonding material 3a. The bonding material 3a is selected taking into account the operating temperature of the semiconductor device, and typically a solder metal is used as the bonding material 3a. When the bonding material 3a, which is a solder metal, is heated, a curing process can be performed to harden the adhesive 5.

[0030] Next, the housing 7a is coated with the sealing resin 6 (see Fig. 1) The insulating substrate 2, the multitude of semiconductor elements 4, and the other end of the lead electrode 7b are filled and sealed by the sealing resin 6. The sealing resin 6 can be a silicone gel or an epoxy resin, but is not limited to either; any resin with suitable physical properties, such as a desired modulus of elasticity, a desired heat resistance, a desired adhesion, and a desired coefficient of linear thermal expansion, will suffice. For example, the desired modulus of elasticity is approximately 0.1 MPa or more and 10 MPa or less for a silicone gel, approximately 9 GPa or more and 13 GPa or less for an epoxy resin, and the desired heat resistance is a maximum of 200°C.

[0031] After the sealing resin 6 is poured in, the semiconductor device assembly is placed in a curing oven or similar appliance to cure the sealing resin 6, and the necessary curing is carried out to complete the semiconductor device. Afterwards, the semiconductor device is tested for the necessary electrical characteristics and the like.

[0032] As described above, the semiconductor device according to the first embodiment comprises the metal base 1, the insulating substrate 2 arranged on the metal base 1, the semiconductor elements 4 mounted on the insulating substrate 2, and the housing 7a, which is bonded to a metal base 1 such that it surrounds the lateral surfaces of the insulating substrate 2 and the semiconductor elements 4, wherein the pair of metal oxide films 8 with a protruding shape is arranged on the peripheral edge region of the metal base 1, and the housing 7a is bonded to the metal base 1 by an adhesive 5 arranged in the region between the pair of metal oxide films 8.

[0033] Furthermore, a method for manufacturing the semiconductor device according to the first embodiment comprises a step (a) in which the insulating substrate 2 is bonded to the metal base 1 and the semiconductor elements 4 are mounted on the insulating substrate 2, a step (b) in which the pair of metal oxide films 8 with a protruding shape is formed on the peripheral edge region of the metal base 1, a step (c) in which the adhesive 5 is applied in the region between the metal oxide films 8 in the pair, a step (d) in which the housing 7a is bonded to the metal base 1 by the adhesive 5, a step (e) in which the lead electrode 7b arranged on the housing 7a is bonded to the semiconductor elements 4, and a step (f) in which the sealing resin 6 is filled into the interior of the housing 7a.

[0034] Accordingly, after the adhesive 5 is applied, if the time until the housing 7a is firmly bonded to the metal base 1 via the adhesive 5 is long, the adhesive 5 tends to spread in its wet state. However, the pair of metal oxide films 8 blocks the adhesive 5 and prevents it from spreading in its wet state. Consequently, the vertical position of the adhesive 5 required to fill the gap between the housing 7a and the metal base 1, caused by the waviness of the metal base 1 or the difference in shape between the housing 7a and the metal base 1, can be ensured.

[0035] Even if the gap between the housing 7a and the metal base 1 is large, the leakage or escape of the sealing resin 6 can be suppressed by bonding the housing 7a and the metal base 1 without a gap. This prevents the reduction in the heat dissipation of the semiconductor device due to the bonding of the escaped sealing resin 6 to the metal base 1. Furthermore, by suppressing the escape of the sealing resin 6, the required amount of the sealing resin 6 can be filled into the interior of the housing 7a, thus ensuring the essential insulating properties. This guarantees the production of a highly reliable semiconductor device.

[0036] Furthermore, by arranging the pair of metal oxide films 8, a specific height position of the adhesive 5 can be ensured even with a small amount of the adhesive 5, thus improving the productivity of the semiconductor device.

[0037] Furthermore, the pair of metal oxide films 8 is formed in a line along the peripheral edge region on the metal base 1. Therefore, when the housing 7a and the metal base 1 are bonded together, the adhesive 5 is prevented from being compressed and spread or distributed too much. Consequently, the thickness of the adhesive 5 required to reduce stress can be ensured, thus reducing the stress exerted on the adhesive 5.

[0038] In step (b), the pair of metal oxide films 8 is further formed by applying laser energy to the peripheral edge region on the metal base 1; therefore, the pair of metal oxide films 8 can be easily formed locally in a short time. Even if a component has a large heat capacity, such as the metal base 1, a laser with high energy density can readily form the pair of metal oxide films 8. <Zweite Ausführungsform>

[0039] Next, a semiconductor device according to the second embodiment will be described. Fig. Figure 6 is a top view illustrating a state prior to bonding the housing 7a in the semiconductor device according to the second embodiment. Fig. Figure 7 is a cross-sectional view illustrating the state before bonding the housing 7a in the semiconductor device according to the second embodiment. In the second embodiment, the same components as those described in the first embodiment are designated with the same reference numerals, and their descriptions are omitted.

[0040] As in Fig. 6 and Fig. As illustrated in Figure 7, in the second embodiment the pair of metal oxide films 9 (corresponding to a second metal oxide film) is further formed with a projecting shape such that it surrounds the lateral surfaces of the metal oxide films 8 in the pair. That is, the pair of metal oxide films 8 that is closer to the adhesive 5 and the pair of metal oxide films 9 are arranged in this order.

[0041] The pair of metal oxide films 9 is formed continuously in a line along the peripheral edge region on the upper surface of the metal base 1. The width of the pair of metal oxide films 9 is also constant. To block the adhesive 5 flowing over the pair of metal oxide films 8 when the adhesive 5 is pressed and spreads in a wet state during bonding of the housing 7a and the metal base 1, the upper edge of the pair of metal oxide films 9 is positioned higher than the upper edge of the pair of metal oxide films 8.

[0042] The process for forming the pair of metal oxide films 9 is the same as the process for forming the pair of metal oxide films 8; therefore, its description is omitted.

[0043] The metal oxide films 9 in the pair do not necessarily surround the lateral surfaces of the metal oxide films 8 over the entire circumferences in the pair and may be arranged with interruptions along the peripheral edge region on the upper surface of the metal base 1 or may be arranged locally at required locations.

[0044] As described above, on the peripheral edge region of the metal base 1, the metal oxide films 9 are arranged in a pair with a protruding shape such that they surround the lateral surfaces of the metal oxide films 8. Therefore, when the adhesive 5 spreads in a wet state and flows over the pair of metal oxide films 8, the pair of metal oxide films 9 can block the adhesive 5. This improves the reliability in ensuring the required vertical position of the adhesive 5 for the first embodiment.

[0045] Furthermore, the height of the upper end of the pair of metal oxide films 9 is higher than the height of the upper end of the pair of metal oxide films 8; therefore, when the housing 7a and the metal base 1 are bonded together, excessive compression and expansion of the adhesive 5 can be prevented. Consequently, the thickness of the adhesive 5 required to reduce stress can be ensured, thus reducing the stress exerted on the adhesive 5. <Dritte Ausführungsform>

[0046] Next, a semiconductor device according to the third embodiment will be described. Fig. Figure 8 is a top view illustrating a state prior to bonding the housing 7a in the semiconductor device according to the third embodiment. In the third embodiment, the same components as those described in the first and second embodiments are designated with the same reference numerals, and their descriptions are omitted.

[0047] As in Fig. As illustrated in Figure 8, in the third embodiment, when the housing 7a and the metal base 1 are bonded together, a screw fastening is also used.

[0048] Through holes 1a for screw fastening are arranged at the four corners of the metal base 1. Holes for screw fastening (not illustrated) are arranged in the housing 7a opposite the through holes 1a of the metal base 1. The housing 7a and the metal base 1 are screwed together from the lower surface of the metal base 1 via the holes and the through holes 1a.

[0049] Instead of a typical external thread, a self-tapping screw can be used for screw fastening. A method for indirectly adjusting the screw fastening circumference via a holding device or similar can also be used.

[0050] When the housing 7a and the metal base 1 are bonded together using a screw fastening, the adhesive 5 is not applied to the four corners of the metal base 1, since adhesion to the housing 7a can be ensured by the screw fastening. That is, the adhesive 5 is applied continuously in a line along the peripheral edge region of the upper surface of the metal base 1, except for the four corners. That is, the pair of metal oxide films 8 is applied continuously in a line along the peripheral edge region of the upper surface of the metal base 1, except for the four corners, such that they surround the adhesive 5.

[0051] Otherwise, the basic configuration is the same as in the case of the first embodiment; however, the pair of metal oxide films 9 can also be arranged as in the case of the second embodiment.

[0052] As described above, in the semiconductor device according to the third embodiment, the through holes 1a for screw fastening are arranged at the four corners of the metal base 1, the holes for screw fastening are arranged in the housing 7a opposite the through holes 1a of the metal base 1, and the housing 7a and the metal base 1 are screwed together via the holes and the through holes 1a.

[0053] Therefore, the housing 7a and the metal base 1 can be bonded together in a screwed state by the adhesive 5; thus, the housing 7a and the metal base 1 can be bonded precisely and firmly with respect to the first and second embodiments. Furthermore, the amount of adhesive 5 applied can be kept low by using a common screw connection.

[0054] Each embodiment can be combined, suitably modified, or omitted.

[0055] Although the disclosure has been illustrated and described in detail, the preceding description is in all aspects illustrative and not limiting. It is therefore understood that numerous modifications and variations can be conceived without deviating from the scope of the invention. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2000323593 [0003, 0005]

Claims

[1] A semiconductor device comprising: a metal base (1); an insulating substrate (2) arranged on the metal base (1); a semiconductor element (4) mounted on the insulating substrate (2); and a housing (7a) bonded to the metal base (1) so as to surround side surfaces of the insulating substrate (2) and the semiconductor element (4), wherein a pair of first metal oxide films (8) having a protruding shape is arranged on a peripheral edge portion of the metal base (1) and the housing (7a) is bonded to the metal base (1) by an adhesive (5) arranged in a region between the first metal oxide films (8) in the pair. [2] A semiconductor device according to claim 1, wherein the pair of first metal oxide films (8) are formed in a line along the peripheral edge portion on the metal base (1). [3] A semiconductor device according to claim 1 or 2, wherein a pair of second metal oxide films (9) having a protruding shape are arranged on a peripheral edge portion of the metal base (1) so as to surround side surfaces of the pair of first metal oxide films (8). [4] A semiconductor device according to claim 3, wherein a height position of an upper end of the pair of second metal oxide films (9) is higher than a height position of an upper end of the pair of first metal oxide films (8). [5] A semiconductor device according to any one of claims 1 to 4, wherein a through hole (1a) for screw fastening is arranged at a corner of the metal base (1), a hole for screw fastening is arranged at a position in the housing (7a) opposite the through hole (1a) of the metal base (1) and the housing (7a) and the metal base (1) are fixed through the hole and the through hole (1a). [6] A method of manufacturing a semiconductor device, comprising the steps of: (a) bonding an insulating substrate (2) to a metal base (1) and mounting a semiconductor element (4) on the insulating substrate (2); (b) forming a pair of first metal oxide films (8) having a protruding shape on a peripheral edge portion of the metal base (1); (c) applying an adhesive (5) in a region between the first metal oxide films (8) in the pair; (d) bonding the housing (7a) to the metal base (1) by the adhesive (5); (e) bonding a lead electrode (7b) arranged on the housing (7a) to the semiconductor element (4); and (f) Filling a sealing resin (6) into the interior of the housing (7a). [7] A method of manufacturing the semiconductor device according to claim 6, wherein in the step (b), the pair of first metal oxide films (8) are formed by applying laser energy to the peripheral edge portion on the metal base (1).

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