1. Field of the Invention
The present disclosure relates to a semiconductor device and a method of making a semiconductor device.
2. Description of Related Art
A semiconductor device incorporating a semiconductor element employs an electroconductive support member for forming a conduction path to the semiconductor element while supporting the semiconductor element. As disclosed in e.g. JP-A-2014-7363, a lead made of a metal is used as the electroconductive support member in such a semiconductor device. A plurality of wires made of e.g. Au are used as a means for electrically connecting the semiconductor element and the lead.
Making such a semiconductor device involves a process of bonding wires. The bonding process is performed successively with respect to each of the wires and cannot be performed collectively with respect to the plurality of wires. This hinders the improvement of the manufacturing efficiency of a semiconductor device. Moreover, since wires are relatively thin, they may be accidentally cut or detached in the process of making or using the semiconductor device. Further, in the case where a heat dissipation member is to be attached to a semiconductor element, a bonding material is currently used to bond the semiconductor element and the heat dissipation member.
The present disclosure has been proposed under the above-described circumstances and provides a semiconductor device that enables an improvement in the manufacturing efficiency as well as an enhancement in strength and reliability of bonding between a semiconductor element and an electroconductive support member or a heat dissipation member. The present disclosure further provides a method of making such a semiconductor device.
A semiconductor device provided according to a first aspect of the present invention includes: a semiconductor element including a functional surface formed with a functional circuit and a reverse surface opposite to the functional surface; an electroconductive support member supporting the semiconductor element and electrically connected to the semiconductor element; and a resin package covering the semiconductor element and at least a part of the electroconductive support member. The semiconductor element is provided with an electrode including a projection formed on the functional surface and a reinforcing layer formed on the functional surface. The semiconductor device further includes a first solid-state welded portion formed by solid state welding of at least a part of the projection of the electrode and at least a part of the electroconductive support member.
A method of making a semiconductor device provided according to a second aspect of the present invention includes: a step of forming an electroconductive support member of a metal on a sacrificial member; a solid state welding step of bonding, by solid state welding, the electroconductive support member and an electrode, the electrode being formed on a functional surface of a semiconductor element and including a projection; and a step of removing the sacrificial member.
Other features and advantages of the present invention will become apparent from the detailed description given below with reference to the accompanying drawings.
Embodiments of the present disclosure are described below with reference to the drawings.
Each of the leads 101-107 is an example of the electroconductive support member according to the present disclosure. The leads 101-107 form a conduction path between the semiconductor element 300 and the outside of the semiconductor device A1 while supporting the semiconductor element 300. The leads 101-107 are made of metal. Examples of the metal forming the leads 101-107 include Cu, Ni, alloys of these, and 42 alloy. Plating layers of e.g. Ti, Ag, Pd, or Au may be provided on the surfaces of the leads 101-107. In this embodiment, the leads 101-107 are made of Cu. The thicknesses of the leads 101-107 are not limited and may be e.g. 50-500 μm or 100-150 μm. Each of the leads 101-107 includes a facing portion 110 and a terminal portion 120. The facing portion 110 overlaps the semiconductor element 300 in plan view and faces an electrode 330, which will be described later, of the semiconductor element 300. The terminal portion 120 extends to the outside of the sealing resin 400. The terminal portion 120 is used for mounting the semiconductor device A1 on e.g. a circuit board. As shown in
As shown in
Referring to
The semiconductor element 300 is an element that performs functions of the semiconductor device A1. For example, the semiconductor element 300 is, without limitation, a transistor, a diode or an LSI. As shown in
The semiconductor element 300 is provided with a plurality of electrodes 330, a passivation film 340 and a protective film 350.
Each of the electrodes 330 is formed on the functional surface 310 and electrically connected to the corresponding lead 101-107. In this embodiment, seven electrodes 330 are provided correspondingly to the seven leads 101-107. These electrodes 330 have a common structure, though differing from each other in size and position.
In this embodiment, as shown in
As shown in
The base layer 331 is in contact with the functional surface 310 and is electrically connected directly to appropriate portions of the functional circuit formed on the functional surface 310. The base layer 331 is made of e.g. Al. For example, the base layer 331 is 0.1-10 μm in thickness.
The passivation flint 340 and the protective film 350 are described below. The passivation film 340 is formed on the functional surface 310. The passivation film 340 prevents an excessive force from being applied to a silicon member, which is the main body of the semiconductor element 300. The passivation film 340 is made of an insulating material such as SiN. For example, the passivation film 340 is 200 nm to 3 μm in thickness. The protective film 350 is formed on the passivation film 340, prevents an excessive force from being applied to a silicon member, which is the main body of the semiconductor element 300, and facilitates formation of the re-distribution layer 333. The protective film 350 is made of an insulating material such as polyimide. For example, the protective film 350 is about 5 μm in thickness.
The passivation film 340 is formed with a through-hole 341, and the base layer 331 is positioned in the through-hole 341. In this embodiment, the passivation film 340 covers side edges of the base layer 331. The protective film 350 is formed with a through-hole 351 at a position corresponding to the through-hole 341 in plan view, thereby exposing the surface of the base layer 331.
The foundation layer 332 serves as a foundation for forming the re-distribution layer 333. The foundation layer 332 corresponds in shape to the electrode 330 in plan view. The foundation layer 332 covers the surface portion of the base layer 331 which is exposed from the passivation film 340 and protective film 350, the side edges of the passivation film which define the through-hole 341, the side edges of the protective film 350 which define the through-hole 351, and appropriate portions of the protective film 350. For example, the foundation layer 332 is made of one of Ti, W or Ta. For example, the foundation layer 332 is about 100 nm in thickness.
The re-distribution layer 333 forms the main portion of the electrode 330 and is larger than the base layer 331 in plan view. The material for the re-distribution layer 333 is not limitative. In this embodiment, the re-distribution layer 333 is made of Cu. For example, the re-distribution layer 333 is about 10 μm in thickness.
The reinforcing layer 370 is provided on the functional surface 310 and reinforces the electrode 330. In this embodiment, the reinforcing layer 370 is provided between the reinforcing layer 333 and the projection 334. The reinforcing layer 370 of this embodiment consists solely of a first electroconductive layer 371. The first electro-conductive layer 371 is a layer made of a single metal and made of Ni in this embodiment. For example, the first electroconductive layer 371 is 3-20 μm in thickness.
The projection 334 is formed on the first electroconductive layer 371 so as to project from the first electroconductive layer 371. The projection 334 may be made of any conductive material and is made of Cu in this embodiment. The shape of the projection 334 is not limitative but is columnar in this embodiment. For example, the size of the projection 334 is 25-200 μm in diameter and 10-500 μm in height. The projection 334 does not overlap the base layer 331 in plan view and is provided at a position avoiding the base layer 331. The projection 334 overlaps the passivation film 340 and the protective film 350 in plan view.
In this embodiment, as shown in
The bond promoting layer 335 forms the outermost layer of the electrode 330 and covers the projection 334 and the first electroconductive layer 371 in this embodiment. The bond promoting layer 335 strengthens the bonding between each of the electrodes 330 and the facing portion 110 of the corresponding lead 101-107. The bond promoting layer 335 includes at least one of Ni or Pd and in this embodiment consists of a Ni layer directly covering the projection 334 and the first electroconductive layer 371 and a Pd layer formed on the Ni layer. For example, the bond promoting layer 335 is about 100 nm to 10 μm in thickness. Other examples of the material for the bond promoting layer 335 include Cu, Al, Ti and Au.
Each electrode 330 and the facing portion 110 of the corresponding lead 101-107 are bonded together by solid state welding. Specifically, the top surface of the projection 334 and the bonding surface 113 of the facing portion 110 are solid-state welded. Thus, as shown in
The sealing resin 400 covers the entirety of the semiconductor element 300 and the leads 101-107 except the terminal portions 120. The sealing resin 400 is made of an insulating material and made of e.g. black epoxy resin in this embodiment. In this embodiment, the sealing resin 400 also fills the space between the bonding surface 113 of the facing portion 110 and the bond promoting layer 335 of the electrode 330 at regions avoiding the projection 334.
An example of a method of making the semiconductor device A1 is described below.
First, a base layer 331 is formed on a semiconductor element 300, as shown in
Then, a passivation film 340 and a protective film 350 are formed, as shown in
Then, a foundation layer 332 is formed as shown in
Then, a re-distribution layer 333 is formed as shown in
Then, as shown in
Then, a projection 334 is formed as shown in
Then, a bond promoting layer 335 is formed as shown in
Then, as shown in
Thereafter, a step of e.g. forming a sealing resin 400 is performed, whereby the semiconductor device A1 is obtained.
The advantages of the semiconductor device A1 are described below.
According to this embodiment, the projections 334 and the leads 101-107 are bonded to each other by solid state welding. As described above, solid state welding is the bonding by which two members are directly bonded to each other and does not require any bonding medium such as a wire or solder intervening between the two. Thus, solid state welding realizes higher bonding strength and higher bonding reliability. Moreover, solid state welding can be performed collectively to all the projections 334 and facing portions 110 of the leads 101-107, which leads to an enhancement in the manufacturing efficiency of the semiconductor device. Since the reinforcing layer 370 is provided, the electrode or the semiconductor element is prevented from being damaged by the force applied in the solid state welding. The reinforcing layer 370 constituting of the first electroconductive layer 371 made of Ni is suitable for projecting the functional surface 310.
Owing to the provision of the projection 334, the bonding area between the electrode 330 and the facing portion 110 of the lead 101-107 is reduced. This leads to a reduction of the force that needs to be applied to achieve a predetermined bonding pressure in the solid state welding process. Thus, the semiconductor element 300 is more reliably prevented from being damaged by the bonding pressure. Moreover, owing to the provision of the projection 334, a space for loading the sealing resin 400 is defined between the functional surface 310 of the semiconductor element 300 and the bonding surface 113 of the facing portion 110 of the lead 101-107. Loading the sealing resin 400 in such a space assures that necessary insulation is reliably provided in the semi conductor device A1.
Arranging the projection 334 so as not to overlap the base layer 331 in plan view prevents an excessive force from being applied to a silicon member, which is the main body of the semiconductor element 300, in solid state welding. Moreover, since the projection 334 overlaps the passivation film 340 and the protective film 350 in plan view, the force applied during the solid state welding is absorbed by the passivation film 340 and the protective film 350.
Provision of the bond promoting layer 335 enhances the reliability of the solid state welding between the projection 334 and the facing portion 110.
In this embodiment, the reinforcing layer 370 comprises a first electroconductive layer 371, a second electroconductive layer 372 and a third electroconductive layer 373. The second electroconductive layer 372 is formed on the lower surface in
The third electroconductive layer 373 is formed on the lower surface in
This embodiment also enhances the manufacturing efficiency of the semiconductor device without causing damage to the functional surface 310. Also, the solid state welding of the projection 334 and the facing portion 110 of the lead 101-107 realizes higher bonding strength and higher bonding reliability. Moreover, since the reinforcing layer 370 is made up of the first electroconductive layer 371, the second electroconductive layer 372 and the third electroconductive layer 373, the functional surface 310 is protected more reliably.
In this embodiment, the foundation layer 332 overlaps the base layer 331, and the projection 334 is formed on the foundation layer 332 by utilizing the foundation layer 332. Thus, the projection 334 overlaps the base layer 331 in plan view.
The reinforcing layer 370 comprises an insulating layer 374. The insulating layer 374 is made of an insulating material and made of polyimide in this embodiment. The insulating layer 374 is formed so as to cover the protective film 350. The insulating layer 374 is formed with a through-hole 374a. The through-hole 374a penetrates the insulating layer 374 in the thickness direction and receives the projection 334.
For example, the projection 334 and the insulating layer 374 are formed as follows. First, a resist film is formed to cover the protective film 350, and then a through-hole is formed in the resist film. Then, Cu-plating is performed to fill the through-hole to form the projection 334. Then, the resist film is removed. Then, the insulating layer 374 is formed by using a polyimide resin material.
In this embodiment, the re-distribution layer 333 is provided on the opposite side of the functional surface 310 with respect to the projection 334. To form the re-distribution layer 333, a foundation layer may be formed on the outer surface the insulating layer 374. On the outer surface of the re-distribution layer 333 is formed the bond promoting layer 335.
This embodiment also enhances the manufacturing efficiency of the semiconductor device without causing damage to the functional surface 310. Also, the solid state welding of the projection 334 and the facing portion 110 of the lead 101-107 realizes higher bonding strength and higher bonding reliability. Moreover, since the re-distribution layer 333 is provided on the outer side of the projection 334, the external force or load to the projection 334 is more distributed.
Each of the leads 101-107 is an example of the electroconductive support member according to the present disclosure. The leads 101-107 form a conduction path between the semiconductor element 300 and the outside of the semiconductor device A4 while supporting the semiconductor element 300. The leads 101-107 are made of metal. Examples of the metal forming the leads 101-107 include Cu, Ni, alloys of these, and 42 alloy. Plating layers of e.g. Ti, Ag, Pd, or Au may be provided on the surfaces of the leads 101-107. In this embodiment, the leads 101-107 are made of Cu. The thicknesses of the leads 101-107 are not limited and may be e.g. 50-500 μm or 100-150 μm.
Each of the leads 101-107 includes a facing portion 110 and a terminal portion 120. The facing portion 110 overlaps the semiconductor element 300 in plan view and faces an electrode 330, which will be described later, of the semiconductor element 300. The terminal portion 120 extends to the outside of the sealing resin 400. The terminal portion 120 is used for mounting the semiconductor device A4 on e.g. a circuit board. As shown in
As shown in
Referring to
The heat dissipation member 200 is bonded to the semiconductor element 300 to promote heat dissipation from the semiconductor element 300. The heat dissipation member 200 is made of metal. Examples of the metal for forming the heat dissipation member 200 include Cu, Ni, alloys of these, and 42 alloy. Plating layers of e.g. Ti, Ag, Pd, or Au may be formed on the surfaces of the heat dissipation member 200. The thickness of the heat dissipation member 200 is, without limitation, e.g. 50-500 μm or 100-150 μm. In this embodiment, the heat dissipation member 200 is formed from Cu, along with the leads 101-107. In this case, in the process of making the semiconductor device A4, the leads 101-107 and the heat dissipation member 200 are formed from a common plate-like member. Bending part of the plate-like member through 180° about an axis extending in the y direction provides the leads 101-107 and the heat dissipation member 200 that face each other with the semiconductor element 300 intervening between the leads and the semiconductor element.
As shown in
The semiconductor element 300 is an element that performs functions of the semiconductor device A4. For example, the semiconductor element 300 is, without limitation, a transistor, a diode or an LSI. As shown in
The semiconductor element 300 includes a plurality of electrodes 330, a passivation film 340, a protective film 300, a reverse surface metal layer 360 and a bond promoting layer 361.
Each of the electrodes 330 is formed on the functional surface 310 and electrically connected to the corresponding lead 101-107. In this embodiment, seven electrodes 330 are provided correspondingly to the seven leads 101-107. These electrodes 330 have a common structure, though differing from each other in size and position.
In this embodiment, as shown in
As shown in
The base layer 331 is in contact with the functional surface 310 and is electrically connected directly to appropriate portions of the functional circuit formed on the functional surface 310. The base layer 331 is made of e.g. Al. For example, the base layer 331 is 0.1-10 μm in thickness.
The passivation film 340 and the protective film 350 are described below. The passivation film 340 is formed on the functional surface 310. The passivation film 340 prevents an excessive force from being applied to a silicon member, which is the main body of the semiconductor element 300. The passivation film 340 is made of an insulating material such as SiN. For example, the passivation film 340 is 200 nm to 3 μm in thickness. The protective film 350 is formed on the passivation film 340, prevents an excessive force from being applied to a silicon member, which is the main body of the semiconductor element 300, and facilitates formation of the re-distribution layer 333. The protective film 350 is made of an insulating material such as polyimide. For example, the protective film 350 is about 5 μm in thickness.
The passivation film 340 is formed with a through-hole 341, and the base layer 331 is positioned in the through-hole 341. In this embodiment, the passivation film 340 covers side edges of the base layer 331. The protective film 350 is formed on the passivation film 340. The protective film 350 is formed with a through-hole 351 at a position corresponding to the through-hole 341 in plan view, thereby exposing the surface of the base layer 331.
The foundation layer 332 serves as a foundation for forming the re-distribution layer 333. The foundation layer 332 corresponds in shape to the electrode 330 in plan view. The foundation layer 332 covers the surface portion of the base layer 331 which is exposed from the passivation film 340 and protective film 350, the side edges of the passivation film which define the through-hole 341, the side edges of the protective film 350 which define the through-hole 351, and appropriate portions of the protective film 350. For example, the foundation layer 332 is made of one of Ti, W or Ta. For example, the foundation layer 332 is about 100 nm in thickness.
The re-distribution layer 333 forms the main portion of the electrode 330 and is larger than the base layer 331 in plan view. The material for the re-distribution layer 333 is not limitative. In this embodiment, the re-distribution layer 333 is made of Cu. For example, the re-distribution layer 333 is about 10 μm in thickness.
The reinforcing layer 370 is provided on the functional surface 310 and reinforces the electrode 330. In this embodiment, the reinforcing layer 370 is provided between the reinforcing layer 333 and the projection 334. The reinforcing layer 370 of this embodiment consists solely of a first electroconductive layer 371. The first electroconductive layer 371 is a layer made of a single metal and made of Ni in this embodiment. For example, the first electroconductive layer 371 is 3-20 μm in thickness. Although the illustrated reinforcing layer 370 has the same structure as that of the reinforcing layer 370 of the semiconductor device A1, the reinforcing layer 370 of the semiconductor device A2 or the semiconductor device A3 may be applied to this embodiment.
The projection 334 is formed on the first electroconductive layer 371 so as to project from the first electroconductive layer 371. The projection 334 may be made of any conductive material and made of Cu in this embodiment. The shape of the projection 334 is not limitative, and columnar in this embodiment. For example, the size of the projection 334 is 25-200 μm in diameter and 10-500 μm in height. The projection 334 does not overlap the base layer 331 in plan view and is provided at a position avoiding the base layer 331. The projection 334 overlaps the passivation film 340 and the protective film 350 in plan view.
In this embodiment, as shown in
The bond promoting layer 335 forms the outermost layer of the electrode 330 and covers the projection 334 and the first electroconductive layer 371 in this embodiment. The bond promoting layer 335 strengthens the bonding between each of the electrodes 330 and the facing portion 110 of the corresponding lead 101-107. The bond promoting layer 335 includes at least one of Ni or Pd and in this embodiment consists of a Ni layer directly covering the projection 334 and the first electroconductive layer 371 and a Pd layer formed on the Ni layer. For example, the bond promoting layer 335 is about 100 nm to 10 μm in thickness. Other examples of the material for the bond promoter layer 335 include Cu, Al, Ti and Au.
Each electrode 330 and the facing portion 110 of the corresponding lead 101-107 are bonded together by solid state welding. Specifically, the top surface of the projection 334 and the bonding surface 113 of the facing portion 110 are solid-state welded. Thus, as shown in
The reverse surf ace metal layer 360 is formed on the reverse surface of the semiconductor element 300 and in this embodiment covers the entirety of the reverse surface 320. The reverse surface metal layer 360 is made of a metal such as Cu, Al, Ti or Au. For example, the reverse surface metal layer 360 is 0.1-10 μm in thickness.
The bond promoting layer 361 is formed on the reverse surface metal layer 360. The bond promoting layer 361 includes at least one of Ni or Pd and in this embodiment consists of a Ni layer directly covering the reverse surface 320 and a Pd layer formed on the Ni layer. For example, the bond promoting layer 361 is about 100 nm to 10 μm in thickness. Other examples of the material for the bond promoting layer 361 include Cu, Al, Ti and Au.
The reverse surface metal layer 360 and the bonding surface 210 of the heat dissipation member 200 are bonded together by solid state welding. In this embodiment, the bond promoting layer 361 is interposed between the reverse surface metal layer 360 and the bonding surface 210. As described above, the reverse surface 220 of the heat dissipation member 200 is irregular. This is as a result of pressing a jig against the reverse surface 220 in bonding the reverse surface metal layer 360 and the heat dissipation member 200 by solid state welding.
The sealing resin 400 covers the entirety of the semiconductor element 300 and the leads 101-107 except the terminal portions 120. The sealing resin 400 is made of an insulating material and made of e.g. black epoxy resin in this embodiment. In this embodiment, the sealing resin 400 also fills the space between the bonding surface 113 of the facing portion 110 and the bond promoting layer 335 of the electrode 330 at regions avoiding the projection 334.
In this embodiment, as described above, the heat dissipation member 200 and the reverse surface 320 of the semiconductor element 300 are solid-state welded. This allows bonding of the heat dissipation member 200 and the semi conductor element 300 to be performed more efficiently than in the case where these are bonded via e.g. a bonding material. Moreover, solid state welding enhances the efficiency of heat transfer from the semiconductor element 300 to the heat dissipation member 200, so that heat dissipation from the semiconductor element 300 is promoted.
In this embodiment again, the projection 334 and the facing portion 110 of the lead 101-107 are bonded to each other by solid state welding. As described above, solid state welding is the bonding by which two members are directly bonded to each other and does not require any bonding medium such as a wire or solder intervening between the two. Thus, solid state welding realizes higher bonding strength and higher bonding reliability. Moreover, the solid state welding can be performed collectively to all projections 334 and facing portions 110 of the leads 101-107, which leads to an enhancement in the manufacturing efficiency of the semiconductor device.
Owing to the provision of the projection 334, the bonding area between the electrode 330 and the facing portion 110 of the lead 101-107 is reduced. This leads to a reduction of the force that needs to be applied to achieve a predetermined bonding pressure in the solid state welding process. Thus, the semiconductor element 300 is prevented from being damaged by the bonding pressure. Moreover, owing to the provision of the projection 334, a space for loading the sealing resin 400 is defined between the functional surface 310 of the semiconductor element 300 and the bonding surface 113 of the facing portion 110 of the lead 101-107. Loading the sealing resin 400 in such a space assures that necessary insulation is reliably provided in the semiconductor device A4.
Arranging the projection 334 so as not to overlap the base layer 331 in plan view prevents an excessive force from being applied to a silicon member, which is the main body of the semiconductor element 300, in solid state welding. Moreover, since the projection 334 overlaps the passivation film 340 and the protective film 350 in plan view, the force applied during the solid state welding is absorbed by the passivation film 340 and the protective film 350.
Provision of the bond promoting layer 335 enhances the reliability of the solid state welding between the projection 334 and the facing portion 110.
The plurality of electroconductive support members 109 form a conduction path between the semiconductor element 300 and outside of the semiconductor device A5 while supporting the semiconductor element 300. Each of the electroconductive support members 109 and the projection 334 of the corresponding electrode 330 are bonded together by solid state welding. Thus, as shown in
As shown in
Each electroconductive support member 109 is made of a metal and contains e.g. Cu as the main component. The electroconductive support member 109 may further contain Ni in addition to Cu. In this case, the proportion of Ni in the electroconductive support member 109 may be e.g. 8-12% by weight.
The sealing resin 400 covers the entirety of the semiconductor element 300 and the electroconductive support members 109. However, as shown in
The insulating layer 610 covers the lower surface in
An example of a method of making the semiconductor device A5 is described below with reference to
First, a sacrificial member 150 is prepared as shown in
Then, as shown in
Then, as shown in
Then, as shown in
Then, as shown in
This embodiment also enhances the manufacturing efficiency of the semiconductor device and realizes reliable bonding of the semiconductor element 300 and the electroconductive support members 100. In the solid state welding process, the electroconductive support members 105 are supported by the jig 802 via the sacrificial member 150. Thus, although traces corresponding to the shape of the jig 803 may be left on the sacrificial member 150, such traces cannot be left on the electroconductive support members 109. In this way, in is possible to prevent traces of the jig 802 from being left on the semiconductor device.
According to this example, the existence of the oxide layer 140 prevents premature solid state welding of the projection 334 and the electroconductive support member 109. That is, the projection 334 and the electroconductive support member 109 are prevented from bonding to each other in an improper positional relationship at an unduly early stage as the projection 334 and the electroconductive support member 109 are pressed against each other and vibration is applied in the solid state welding process.
The semiconductor device according to the present disclosure is not limited to the foregoing embodiments. The specific structure of each part of the semiconductor device according to the present disclosure can be varied in design in many ways.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-260257 | Dec 2014 | JP | national |
| 2015-230357 | Nov 2015 | JP | national |