Semiconductor device and method for manufacturing the semiconductor device

Abstract

Semiconductor device comprising: • an insulating substrate (1) having a wiring structure (1a) in a surface layer thereof; and • a terminal electrode (4) having a pocket-shaped interior (4c) with a terminal electrode tip opening (4b), wherein • the terminal electrode (4) is anchored in a free-standing state by joining it to the wiring structure (1a).

Description

Background of the invention: Area

[0001] The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device. background

[0002] JP 2017-199713 A discloses an ultrasonic welding process, which is a technology for welding a terminal electrode to a wiring structure on an insulating substrate. Ultrasonic welding transfers ultrasonic acoustic vibrations to a loaded interface to generate friction and initiate a reaction.

[0003] However, if friction is generated at the interface between a wiring structure and a terminal electrode in the method described above, a problem arises in that a fine metal powder is distributed, which reduces the reliability of the semiconductor device. Summary

[0004] In view of the problem described above, it is an objective of the present disclosure to provide a highly reliable semiconductor device and a method for its manufacture in which a wiring structure and a terminal electrode are welded together without distributing fine metal powder.

[0005] The features and advantages of the present disclosure can be summarized as follows.

[0006] A semiconductor device according to the present disclosure comprises: an insulating substrate with a wiring structure in a surface layer thereof; and a terminal electrode having a pocket-shaped interior with a terminal electrode tip opening, wherein the terminal electrode is anchored in a freestanding state by joining it to the wiring structure.

[0007] Other and further tasks, features and benefits of the revelation will become clearer from the following description. Brief description of the characters Fig. Figure 1 is a cross-section illustrating a welded structure in a pre-welding state according to the first embodiment of the present disclosure. Fig. Figure 2 is a top view illustrating the welded structure in the state prior to welding according to the first embodiment of the present disclosure. Fig. Figure 3 is a cross-section illustrating the welded structure in the state after welding according to the first embodiment of the present disclosure. Fig. Figure 4 is a top view illustrating the welded structure in the state after welding according to the first embodiment of the present disclosure. Fig. Figure 5 is a top view illustrating the welded structure in the state prior to welding according to a third embodiment of the present disclosure. Fig. Figure 6 is a cross-section illustrating the welded structure in the state after welding according to the third embodiment of the present disclosure. Description of the embodiments: First embodiment.

[0008] Before describing a first embodiment, a prior art technology known as ultrasonic welding for welding a terminal electrode to a wiring structure of an insulating substrate is described. In ultrasonic welding, the tip of a terminal electrode is first positioned over a wiring structure of an insulating substrate. At this point, the terminal electrode tip is in contact with the wiring structure. If ultrasonic acoustic vibrations are transmitted to the loaded contact section, the terminal electrode tip vibrates, generating friction at the interface between the wiring structure on the insulating substrate and the terminal electrode tip. The friction disperses an oxide layer that forms on the surface layer of the interface, thereby exposing a fresh surface.On the fresh surface, atomic motion is activated by heating due to frictional heat, causing the metal atoms to move by diffusion. This movement creates a mutual attraction between the metal atoms, forming a solid-state weld between the wiring structure and the terminal electrode.

[0009] As described above, ultrasonic welding utilizes both a load and ultrasonic acoustic vibrations. This means that an ultrasonic wave generator is designed to produce a high-frequency AC current, thereby providing electrical energy to an oscillator. This causes the oscillator to convert the electrical energy and transmit it as mechanical vibrations to the tip of the welding electrode under load.

[0010] However, if the terminal electrode tip vibrates and friction is generated between the terminal electrode tip and the wiring structure on the insulating substrate, the distribution of fine metal powder creates the problem of reduced reliability of the semiconductor device. This is a particularly serious problem in the case of a semiconductor device that uses a large amount of power, such as a power semiconductor intended, for example, for an electric railway or power applications, since the metal powder can cause dielectric breakdown due to a corona discharge. Accordingly, it is an object of the present disclosure to provide a semiconductor device that addresses this problem.

[0011] Fig. Figure 1 is a cross-section illustrating a weld structure in a pre-welding state according to the first embodiment of the present disclosure. The weld structure according to the first embodiment comprises an insulating substrate 1. The insulating substrate 1 comprises a wiring structure 1a with raised features above the surface layer and a ceramic substrate 1b inside. The wiring structure 1a is made of aluminum (Al), copper (Cu), or alloys thereof. The ceramic substrate 1b is made of an inorganic material such as aluminum oxide (Al₂O₃), aluminum nitride (Al₃), or silicon nitride (Si₄N₄). The insulating substrate 1 is furthermore connected to a heat sink 3 via a bonding material 2. A terminal electrode 4 is positioned directly above the wiring structure 1a.

[0012] Fig. Figure 2 is a top view illustrating the weld structure in the pre-welding state according to the first embodiment of the present disclosure. The tip of the terminal electrode 4 has a folded circuit structure 4a and contacts the wiring structure 1a such that the raised sections of the folds engage with the raised sections of the wiring structure 1a. The tip of the terminal electrode 4 also has a terminal electrode tip opening 4b and is designed such that a pocket-shaped interior 4c extends inwards from the opening. The terminal electrode 4 is made of aluminum or copper, but the circuit structure 4a need not be made of aluminum or copper in a pure state and may also be subjected to a nickel (Ni) plating treatment.

[0013] It should be noted that, although a configuration is illustrated here in which the raised sections of the wiring structure 1a and the circuit structure 4a alternately interlock, any configuration is possible as long as the terminal electrode 4 is anchored in a free-standing state after welding. For example, a configuration is also possible in which the circuit structure 4a has a spirally raised shape or the like.

[0014] The method for welding the terminal electrode 4 and the insulating substrate 1 according to the first embodiment is described. First, a device is used to securely align the circuit structure 4a and the wiring structure 1a in an engagement position. Next, compressed air is injected from the terminal electrode tip opening 4b into the interior 4c. The pressure of the compressed air is regulated by a pressure regulator to be, for example, between 0.6 MPa and 0.8 MPa.

[0015] The interior space 4c, which lacks an outlet, swells when filled with compressed air. As soon as the interior space 4c swells, the tip of the terminal electrode 4 undergoes plastic deformation, causing a change in the spacing between the raised and lowered folds in the circuit structure 4a. Consequently, a gap is created with respect to the wiring structure 1a, which anchors the terminal electrode 4 in a free-standing position.

[0016] Fig. Figure 3 is a cross-section illustrating the welded structure in the post-welded state according to the first embodiment of the present disclosure. Furthermore, Fig. 4 A top view illustrating the state of the welded structure after welding according to the first embodiment of the present disclosure. As described above, in the first embodiment, compressed air is injected from the terminal electrode tip opening 4b to cause the tip of the terminal electrode 4 to swell. As a result, the free space between the circuit structure 4a and the wiring structure 1a is as shown in Fig. 3 filled, which causes the connecting electrode 4 to be anchored in a freestanding state. Second embodiment.

[0017] In a second embodiment, the configuration of the welding structure is similar to the first embodiment, but the second embodiment differs in that pure water is injected from the terminal electrode tip opening 4b.

[0018] The method for welding the terminal electrode 4 and the insulating substrate 1 according to the second embodiment is illustrated. First, a device is used to securely align the circuit structure 4a and the wiring structure 1a in an engagement position. Next, industrially pure water is injected from the terminal electrode tip opening 4b into the interior 4c. The pressure of the industrially pure water is regulated by a pressure regulator to be, for example, between 0.6 MPa and 0.8 MPa.

[0019] The interior space 4c, which lacks an outlet opening, swells when filled with industrially pure water. As soon as the interior space 4c swells, the tip of the terminal electrode 4 undergoes plastic deformation, causing a change in the spacing between the raised and lowered folds in the circuit structure 4a. Consequently, a gap is created with respect to the wiring structure 1a, which anchors the terminal electrode 4 in a free-standing position. Third embodiment.

[0020] Fig. Figure 5 is a top view illustrating the weld structure in the pre-welding state according to a third embodiment of the present disclosure. In the third embodiment, the shape relating to the joining of the terminal electrode 4 and the insulating substrate 1 differs from other embodiments.

[0021] The welding structure according to the third embodiment has a wiring structure 1c with a recessed shape in the surface layer of the insulating substrate 1. The welding structure according to the third embodiment also includes a connection electrode 4. The connection electrode 4 has a connection electrode tip 4d which engages in the inner surface of the wiring structure 1c. The connection electrode 4 also has a connection electrode tip opening 4e and is shaped such that a pocket-shaped interior space 4f is formed extending inwards from the opening.

[0022] The method for welding the terminal electrode 4 and the insulating substrate 1 according to the third embodiment is described. First, a device is used to securely align the terminal electrode tip 4d and the wiring structure 1c in an engagement position. Next, compressed air is injected into the interior 4f from the terminal electrode tip opening 4e. The pressure of the compressed air is regulated by a pressure regulator to be, for example, between 0.6 MPa and 0.8 MPa.

[0023] The interior space 4f, which lacks an outlet opening, swells when filled with compressed air. As soon as the interior space 4f swells, the terminal electrode tip 4d undergoes plastic deformation, thereby filling the space with respect to the wiring structure 1c. Consequently, the terminal electrode 4 is anchored in a free-standing position.

[0024] Fig. Figure 6 is a cross-section illustrating the weld structure in the post-weld state according to the third embodiment of the present disclosure. As described above, in the third embodiment, compressed air is injected from the terminal electrode tip opening 4e to cause the terminal electrode tip 4d to swell. As a result, the free space between the terminal electrode tip 4d and the wiring structure 1c is as shown in Figure 6. Fig. 6 filled, which causes the connecting electrode 4 to be anchored in a freestanding state.

[0025] Obviously, many modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore understood that the invention, within the scope of protection of the appended claims, can be implemented differently than specifically described.

[0026] The entire disclosure of Japanese patent application no. 2022-61965, filed on April 1, 2022, comprising the description, claims, figures and abstract on which the priority of the present application is based, is hereby incorporated by reference in its entirety. 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 2017199713 A

[0002] JP 202261965

[0026]

Claims

[1] comprising a semiconductor device: • an insulating substrate (1) which has a wiring structure (1a) in a surface layer thereof; and • a terminal electrode (4) which has a pocket-shaped interior (4c) with a terminal electrode tip opening (4b), wherein • the connecting electrode (4) is anchored in a freestanding state by joining it to the wiring structure (1a). [2] Semiconductor device according to claim 1, wherein • the wiring structure (1a) has a raised form, • the terminal electrode (4) has a circuit structure (4a) with a folded shape, and • the circuit structure (4a) is anchored in a freestanding state by joining it to the wiring structure. [3] Semiconductor device according to claim 1, wherein • the wiring structure (1c) has a recessed shape, and • the terminal electrode (4) is anchored in a freestanding state by joining it to the wiring structure (1c). [4] Method for manufacturing a semiconductor device which is provided with • an insulating substrate (1) which has a wiring structure (1a) in a surface layer thereof, and • a connecting electrode (4) which has a pocket-shaped interior (4c) with a connecting electrode tip opening (4b), wherein the method comprises: • a verification process for the safe positioning of the connection electrode (4) in an engagement position with respect to the wiring structure (1a); and • a plastic deformation process which causes the terminal electrode (4) to swell until the terminal electrode (4) is anchored in a free-standing state by joining it to the wiring structure (1a). [5] Method for manufacturing the semiconductor device according to claim 4, wherein the plastic deformation process is a process for injecting compressed air into an interior space (4c) from the terminal electrode tip opening (4b). [6] Method for manufacturing the semiconductor device according to claim 4, wherein the plastic deformation process is a process for injecting pure water into the interior (4c) of the terminal electrode tip opening (4b).

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