Semiconductor device with a plurality of semiconductor chips

文档序号：636329 发布日期：2021-05-11 浏览：15次中文

阅读说明：本技术 半导体装置 (Semiconductor device with a plurality of semiconductor chips ) 是由武田直己恩田智弘河野贤哉新谷宽春別府佑谷江尚史于 2020-11-11 设计创作，主要内容包括：本发明提供一种在两面安装构造的功率半导体中即使使用无Pb材料等高弹性的接合材料也能降低半导体元件所产生的应力的可靠性高的半导体装置。一种半导体装置,其特征中在于,具备：半导体元件,仅在一面具有栅极电极；上部电极,连接于所述半导体元件的具有所述栅极电极的面；以及下部电极,连接于所述半导体元件的与具有所述栅极电极的面相反一侧的面,在所述半导体装置中,所述上部电极中的与所述半导体元件的具有所述栅极电极的面连接的连接端部位于比所述半导体元件的具有所述栅极电极的面的端部靠内侧、且所述下部电极中的与所述半导体元件的所述相反一侧的面连接的连接端部位于比所述半导体元件的所述相反一侧的面的端部靠内侧。(The invention provides a highly reliable semiconductor device capable of reducing stress generated in a semiconductor element even when a highly elastic bonding material such as a Pb-free material is used for a power semiconductor having a double-sided mounting structure. A semiconductor device is characterized by comprising: a semiconductor element having a gate electrode on only one surface; an upper electrode connected to a surface of the semiconductor element having the gate electrode; and a lower electrode connected to a surface of the semiconductor element opposite to the surface having the gate electrode, wherein a connection end portion of the upper electrode connected to the surface of the semiconductor element having the gate electrode is located inside an end portion of the surface of the semiconductor element having the gate electrode, and a connection end portion of the lower electrode connected to the surface of the semiconductor element opposite to the surface is located inside an end portion of the surface of the semiconductor element opposite to the surface.)

1. A semiconductor device is characterized by comprising:

a semiconductor element having a gate electrode on only one surface;

an upper electrode connected to a surface of the semiconductor element having the gate electrode; and

a lower electrode connected to a surface of the semiconductor element opposite to the surface having the gate electrode,

in the semiconductor device, a semiconductor element is provided,

a connection end portion of the upper electrode connected to a surface of the semiconductor element having the gate electrode is located inward of an end portion of the surface of the semiconductor element having the gate electrode, and a connection end portion of the lower electrode connected to the opposite surface of the semiconductor element is located inward of an end portion of the opposite surface of the semiconductor element.

2. The semiconductor device according to claim 1,

in at least 1 corner portion of the semiconductor element, a connection end portion of the lower electrode connected to the opposite surface of the semiconductor element is located more inward than an end portion of the opposite surface of the semiconductor element.

3. The semiconductor device according to claim 2,

the lower electrode has a connection end portion connected to the opposite surface of the semiconductor element, the connection end portion being located outside an end portion of the opposite surface of the semiconductor element, except for a corner portion of the semiconductor element.

4. The semiconductor device according to claim 1,

the upper electrode is connected to the semiconductor element via a 1 st conductive bonding material,

the lower electrode is connected to the semiconductor element via a 2 nd conductive bonding material,

an end portion of a connection portion between the 1 st conductive bonding material and the upper electrode, an end portion of a connection portion between the 2 nd conductive bonding material and the lower electrode, an end portion of a connection portion between the 1 st conductive bonding material and the semiconductor element, and an end portion of a connection portion between the 2 nd conductive bonding material and the semiconductor element are located inside of an end portion of the semiconductor element.

5. The semiconductor device according to claim 4,

an end of a connection portion between the 1 st conductive bonding material and the upper electrode and an end of a connection portion between the 2 nd conductive bonding material and the lower electrode are substantially aligned in a vertical direction.

6. The semiconductor device according to claim 5,

7. The semiconductor device according to any one of claims 4 to 6,

the 1 st conductive bonding material and the 2 nd conductive bonding material are any of lead-free solder, a sintered material, or a conductive adhesive material.

8. A semiconductor device is characterized by comprising:

a semiconductor element having a peripheral insulating layer on only one surface and on a chip peripheral portion;

an upper electrode connected to a surface of the semiconductor element having the outer peripheral insulating layer; and

a lower electrode connected to a surface of the semiconductor element opposite to the surface having the outer peripheral insulating layer,

in the semiconductor device, a semiconductor element is provided,

the semiconductor element is a diode and the semiconductor element is a diode,

a connection end portion of the upper electrode connected to a surface of the semiconductor element having the outer peripheral insulating layer is located inward of an end portion of the surface of the semiconductor element having the outer peripheral insulating layer, and a connection end portion of the lower electrode connected to the opposite surface of the semiconductor element is located inward of an end portion of the opposite surface of the semiconductor element.

9. The semiconductor device according to claim 8,

10. The semiconductor device according to claim 9,

11. The semiconductor device according to claim 8,

the upper electrode is connected to the semiconductor element via a 1 st conductive bonding material,

the lower electrode is connected to the semiconductor element via a 2 nd conductive bonding material,

12. The semiconductor device according to claim 11,

13. The semiconductor device according to claim 12,

14. The semiconductor device according to any one of claims 11 to 13,

the 1 st conductive bonding material and the 2 nd conductive bonding material are any of lead-free solder, a sintered material, or a conductive adhesive material.

Technical Field

The present invention relates to a structure of a semiconductor device, and more particularly to a technique effective for a mounting structure applied to a power semiconductor for power control.

Background

Power semiconductors are becoming widespread worldwide, and semiconductor devices used for switching circuits and rectifier circuits are being developed in mounting technologies for various demands such as higher current, higher heat dissipation, and higher reliability.

As a mounting technique of a power semiconductor, a double-sided mounting structure is known, in which electrodes are provided on upper and lower surfaces of a semiconductor element, and at least 1 electrode is connected to an external electrode on both the upper and lower surfaces.

Examples of the electrodes on the upper and lower surfaces of the Semiconductor element include a MOSFET (Metal Oxide Semiconductor Field Effect Transistor): Field Effect Transistor) having a structure in which a source electrode and a Gate electrode are provided on one surface and a drain electrode is provided on the other surface, and an IGBT (Insulated Gate Bipolar Transistor) having an emitter electrode and a Gate electrode on one surface and a collector electrode on the other surface, and a diode having a P-pole on one surface and an N-pole on the other surface.

In addition, as the power semiconductor element, a silicon oxide film (SiO) is generally formed on the outer peripheral portion of any one surface₂) An outer peripheral insulating layer. In the above example, in the MOSFET, the outer peripheral insulating layer is formed on the source electrode side, and I isIn the GBT, an outer peripheral insulating layer is formed on the emitter electrode side, and in the case of a diode, an outer peripheral insulating layer is formed on either the P or N electrode side.

As an example of the semiconductor device having the double-sided mounting structure, for example, a semiconductor device of patent document 1 is proposed. In patent document 1, a lead frame 5 and a base electrode 3 are connected to the upper and lower surfaces of a semiconductor element 1 via solders 2 and 4. The semiconductor element 1 has a concave notch at an end portion except for the uppermost portion and the lowermost portion thereof, and the solder 2, 4 is not connected to the end portion of the semiconductor element 1. However, the solders 2 and 4 are connected in the vicinity of the end of the semiconductor element 1, while avoiding the end. The end of the lead frame 5 is connected to the inside of the end of the semiconductor element 1, and the end of the base electrode 3 is connected to the outside of the end of the semiconductor element 1. The lead frame 5, the solders 2 and 4, the base electrode 3, and a part or all of the semiconductor element 1 are sealed with a sealing resin 6.

In patent document 2, a metal plate 6a electrically connected to the lead frame 1 and the case electrode 5 is connected to the upper and lower surfaces of the semiconductor element 3 via a bonding member 2. The end of the lead frame 1 is connected to the inside of the end of the semiconductor element 3, and the end of the surface of the metal plate 6a connected to the bonding member 2 is connected to the end of the semiconductor element 3 flush therewith. The lead frame 1, the bonding member 2, the metal plate 6a, and the semiconductor element 3 are partially or entirely sealed by the insulating member 4.

In patent document 3, the metal layers 4a, 4b, 14a, and 14b are connected to both surfaces of the semiconductor element 6 via solder layers 5a, 5b, 15a, and 15 b. The ends of the solder layers 5a, 5b, 15a, 15b are all connected inside the semiconductor element 6. The ends of the surfaces of the metal layers 4a, 4b, 14a, and 14b connected to the semiconductor element 6 are connected to the inside of the ends of the semiconductor element 6. In this semiconductor device, the semiconductor element 6 has gate electrodes (control electrodes) on both surfaces.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-187494

Patent document 2: japanese patent laid-open publication No. 2004-289028

Patent document 3: japanese patent laid-open publication No. 2013-149760

Disclosure of Invention

However, in recent years, due to environmental concerns, the limitation of lead (Pb) -containing solders that are used in large quantities as bonding materials for semiconductor devices has increased. Pb has a low melting point and low elasticity, and therefore has an advantage of being easy to handle as a bonding material for a semiconductor device. However, since they are harmful to the human body, the development of Pb-free materials as substitutes for Pb-containing solders has been advanced.

As the Pb-free material, for example, Pb-free solders such as Sn-Sb and Sn-Ag-Cu, and bonding materials sintered at high temperature using Cu and Ag are generally used. These bonding materials have higher elasticity than lead-containing solder, and stress of the semiconductor element increases due to a thermal load at the time of connection, and in the worst case, a problem such as cracking occurs.

In particular, in a double-sided mounting structure which is often used for a power semiconductor, it is necessary to increase a connection area as much as possible in order to flow a large current, and there is a great problem to realize high reliability.

In patent document 1, the lead frame 5 is shorter in length than the semiconductor element 1, and the base electrode 3 is longer in length than the semiconductor element 1. Therefore, for example, when the semiconductor element 1 and the base electrode 3, and the semiconductor element 1 and the lead frame 5 are connected to each other by using a Pb-free material, there is a possibility that bending deformation occurs due to a difference in thermal expansion coefficients between them, and stress of the semiconductor element 1 increases due to the highly elastic Pb-free material. Therefore, a problem arises in that the risk of cracking of the semiconductor element 1 increases.

In patent document 2, the lead frame 1 is shorter than the semiconductor element 3, and the metal plate 6a is the same length as the semiconductor element 3. Therefore, for example, when the semiconductor element 3 and the lead frame 1, and the semiconductor element 1 and the metal plate 6a are connected to each other by using a Pb-free material, there is a possibility that bending deformation occurs due to a difference in thermal expansion coefficients between them, and stress of the semiconductor element 3 increases due to the highly elastic Pb-free material. Therefore, as in patent document 1, there is a problem that the risk of cracking of the semiconductor element 3 increases.

In patent document 3, gate electrodes (control electrodes) are provided on both surfaces of the semiconductor element 6, and the metal layers 4a, 4b, 14a, and 14b are partially connected to the semiconductor element 6 and have a symmetrical structure with the semiconductor element 6 as the center. Thus, it is by no means an appropriate configuration for applying to a semiconductor device through which a large current flows, for example, using a semiconductor element such as a MOSFET in which a source electrode and a gate electrode are provided on one surface and a drain electrode is provided on the other surface.

Accordingly, an object of the present invention is to provide a highly reliable semiconductor device capable of reducing stress generated in a semiconductor element even when a highly elastic bonding material such as a Pb-free material is used for a power semiconductor having a double-sided mounting structure.

Another object of the present invention is to provide a semiconductor device that achieves high reliability in a power semiconductor having a double-sided mounting structure and can handle a large current by high heat dissipation.

In order to solve the above problem, the present invention provides a semiconductor device comprising: a semiconductor element having a gate electrode on only one surface; an upper electrode connected to a surface of the semiconductor element having the gate electrode; and a lower electrode connected to a surface of the semiconductor element opposite to the surface having the gate electrode, wherein a connection end portion of the upper electrode connected to the surface of the semiconductor element having the gate electrode is located inside an end portion of the surface of the semiconductor element having the gate electrode, and a connection end portion of the lower electrode connected to the surface of the semiconductor element opposite to the surface is located inside an end portion of the surface of the semiconductor element opposite to the surface.

Further, a semiconductor device according to the present invention includes: a semiconductor element having a peripheral insulating layer on only one surface and on a chip peripheral portion; an upper electrode connected to a surface of the semiconductor element having the outer peripheral insulating layer; and a lower electrode connected to a surface of the semiconductor element opposite to the surface having the outer peripheral insulating layer, wherein the semiconductor element is a diode, a connection end portion of the upper electrode connected to the surface of the semiconductor element having the outer peripheral insulating layer is located inside an end portion of the surface of the semiconductor element having the outer peripheral insulating layer, and a connection end portion of the lower electrode connected to the surface of the semiconductor element opposite to the surface is located inside an end portion of the surface of the semiconductor element opposite to the surface.

According to the present invention, a highly reliable semiconductor device can be realized in which stress generated in a semiconductor element can be reduced even when a highly elastic bonding material such as a Pb-free material is used for a power semiconductor having a double-sided mounting structure.

Further, a semiconductor device which can realize high reliability in a power semiconductor having a double-sided mounting structure and can cope with a large current by high heat dissipation can be realized.

Problems, structures, and effects other than those described above will be apparent from the following description of the embodiments.

Drawings

Fig. 1 is a cross-sectional view showing a schematic structure of a semiconductor device according to embodiment 1 of the present invention.

Fig. 2 is a diagram schematically showing a longitudinal configuration in the vicinity of the semiconductor element 1a in fig. 1.

Fig. 3 is a diagram schematically showing a planar configuration in the vicinity of the semiconductor element 1a in fig. 1.

Fig. 4 is a diagram schematically showing deformation in the vicinity of the end of the semiconductor element in the conventional semiconductor device connection process.

Fig. 5 is a diagram schematically showing deformation of the vicinity of the end of the semiconductor element in the connection process of the semiconductor device according to example 1 of the present invention.

Fig. 6 is a diagram schematically showing a part of the longitudinal configuration of the semiconductor device of embodiment 1 of the present invention.

Fig. 7 is a diagram showing thermal stress generated in the semiconductor element in the connection process of the semiconductor device according to embodiment 1 of the present invention.

Fig. 8 is a cross-sectional view showing a schematic structure of a semiconductor device according to embodiment 2 of the present invention.

Fig. 9 is a diagram schematically showing a planar configuration of a semiconductor device of embodiment 3 of the present invention.

Fig. 10 is a diagram schematically showing the longitudinal configuration of a semiconductor device of embodiment 3 of the present invention.

Fig. 11 is a diagram schematically showing the longitudinal configuration of a semiconductor device of embodiment 3 of the present invention.

Fig. 12 is a diagram showing a modification of embodiment 1 (fig. 2).

Fig. 13 is a diagram showing a modification of embodiment 2 (fig. 8).

Description of the symbols

1 a: a semiconductor element (switching circuit chip); 1 b: a capacitor; 1 c: a control circuit chip; 1 d: an upper electrode (2 nd inner electrode); 1 e: (1 st) a conductive bonding material (bonding material for circuit body); 1 f: a wire; 1 g: a lower electrode (1 st internal electrode); 1 h: molding resin (1 st resin, resin of circuit body); 1 i: a lead frame (support body); 2: a base (1 st external electrode, 1 st external terminal); 2 a: a base (No. 1 electrode face); 3: leads (2 nd external electrode, 2 nd external terminal); 3 a: lead head (2 nd electrode face); 4: a 2 nd conductive bonding material (bonding material for semiconductor devices); 5: a molding resin (2 nd resin, resin of a semiconductor device); 7 a: (1 st) the vicinity of the corner of the semiconductor element 1 a; 7 b: (2) the vicinity of the corner of the semiconductor element 1 a; 7 c: (3) the vicinity of the corner of the semiconductor element 1 a; 7 d: (4) the vicinity of the corner of the semiconductor element 1 a; 8 a: (1 st) an end portion of the lower electrode 1 g; 8 b: (2) an end portion of the lower electrode 1 g; 9 a: (1 st) an end portion of the semiconductor element 1 a; 9 b: (2) an end portion of the semiconductor element 1 a; 10 a: a semiconductor element (diode); 10 e: a conductive bonding material (bonding material for semiconductor devices); 20: a base (1 st external electrode, 1 st external terminal); 20 a: a base (No. 1 electrode face); 30: leads (2 nd external electrode, 2 nd external terminal); 30 a: lead head (2 nd electrode face); 50: molded resin (of semiconductor device)A resin); 100: a circuit body; 200: a semiconductor device (rectifying element); 300: a semiconductor device (rectifying element); l: outer peripheral insulating layer (SiO)₂) (ii) a p 1: stress concentration portion (upper); p 2: stress concentration portion (lower); j: a distance from an end of a surface of the upper electrode 1d connected to the semiconductor element 1a to an end of a surface of the lower electrode 1g connected to the semiconductor element 1 a; w: a distance from an end of a surface of the upper electrode 1d connected to the semiconductor element 1a to an end of the semiconductor element 1 a; x: a value obtained by dividing J by W and performing dimensionless transformation; tb: a direction of bending stress; tj: a solder thermal stress direction; d2: a region from a connection end portion of the first main surface of the semiconductor element 1a with the lower electrode 1g to an end portion of the semiconductor element 1 a; s: a source electrode (2 nd main terminal); d: a drain electrode (1 st main terminal); c: a gate electrode (control electrode).

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and the detailed description of the overlapping portions will be omitted.

[ example 1 ]

A semiconductor device according to embodiment 1 of the present invention will be described with reference to fig. 1 to 7 and 12. Fig. 4 is a diagram schematically illustrating deformation in the vicinity of the end of the semiconductor element in the connection process of the conventional semiconductor device shown as a comparative example, in order to facilitate understanding of the operation and effect of the present invention shown in fig. 5. Fig. 12 is a view showing a modification of fig. 2.

The semiconductor device 200: one of (A)

First, the structure and function of the semiconductor device of the present embodiment will be described with reference to fig. 1. Fig. 1 is a diagram schematically showing a cross section of a vertical structure of a semiconductor device (rectifier element) 200 for a vehicle-mounted Alternator (Alternator) according to the present embodiment.

In fig. 1, the semiconductor device 200 includes, as main components: a base (1 st external electrode, 1 st external terminal) 2 having a base (1 st electrode surface portion) 2a on an upper portion (above the paper surface of fig. 1), a lead (2 nd external electrode, 2 nd external terminal) 3 having a lead (2 nd electrode surface portion) 3a on a lower portion (below the paper surface of fig. 1), and a circuit body 100.

The base 2a is connected to a lower electrode (1 st internal electrode) 1g of a circuit body 100 (described later) via a 2 nd conductive bonding material (bonding material of a semiconductor device) 4.

The lead 3a is connected to an upper electrode (2 nd internal electrode) 1d of the circuit body 100, which will be described later, via a 2 nd conductive bonding material 4.

Further, a part of the base 2a and the upper portion of the base 2, a part of the lead 3a and the lower portion of the lead 3, and the circuit body 100 are covered and sealed with a mold resin (2 nd resin, resin of a semiconductor device) 5.

The base 2 and the lead 3 are external terminals for electrical connection to an external circuit (an alternator circuit). The above is a summary of the structure of the semiconductor device 200.

Circuit body 100

Next, the detailed structure of the circuit body 100 provided in the semiconductor device 200 will be described. In fig. 1, the area of the circuit body 100 is shown by a broken line to describe the circuit body 100.

The circuit body 100 includes a semiconductor element 1a, a capacitor 1b, and a control circuit chip 1 c. The circuit body 100 includes a lower electrode 1g, an upper electrode 1d, and a lead frame (support) 1 i.

The semiconductor element 1a is formed of, for example, a MOSFET. The drain electrode D (1 st main terminal) and the source electrode S (2 nd main terminal) of the MOSFET are provided on the main surfaces of the semiconductor element 1 a. Hereinafter, the surface of the semiconductor element 1a on which the drain electrode D is provided will be referred to as the first main surface of the semiconductor element 1a, and the surface on which the source electrode S is provided will be referred to as the second main surface of the semiconductor element 1 a.

The drain electrode D is connected to a surface (1 st surface) of one end of the lower electrode 1g as the 1 st internal electrode via a 1 st conductive bonding material (bonding material of circuit body) 1 e. Alternatively, the first conductive bonding material 1e may be connected by ultrasonic bonding or the like.

The source electrode S is connected to one end surface (1 st surface) of the upper electrode 1d as the 2 nd internal electrode via the 1 st conductive bonding material 1 e.

The control circuit chip 1c is connected to the lead frame 1i as a support via the 1 st conductive bonding material 1 e.

The capacitor 1b that supplies power to the control circuit chip 1c is also connected to the lead frame 1i via the 1 st conductive bonding material 1 e. The capacitor 1b can be, for example, a ceramic capacitor.

The other end surface (2 nd surface) of the lower electrode 1g is exposed from the 1 st surface of the circuit body 100 as described later, and is in contact with the base 2a via the 2 nd conductive bonding material 4.

The other end surface (2 nd surface) of the upper electrode 1d is exposed from the 2 nd surface of the circuit body 100 as described later, and is in contact with the lead 3a via the 2 nd conductive bonding material 4.

Further, the lead frame 1i is configured to be electrically insulated from the base 2, i.e., the base 2 a.

The material of the 1 st conductive bonding material 1e and the 2 nd conductive bonding material 4 is, for example, solder, metal containing Au, Ag, or Cu, or a conductive adhesive material, which is a common conductive bonding material. As the solder, a general high-lead solder, eutectic solder, lead-free solder, or the like is used. As the conductive adhesive material, a material containing a resin and a metal filler such as Ag, Cu, and Ni or a material composed of only a metal is used.

The material of the 1 st conductive bonding material 1e and the material of the 2 nd conductive bonding material 4 may be the same material or different materials. The 1 st conductive bonding material 1e may be the same material or different materials above and below the semiconductor element 1 a. The material of the 2 nd conductive bonding material 4 may be the same material or different materials above and below the circuit body 100

Cu having high thermal conductivity and excellent electrical conductivity is mainly used as the material of the base 2, the lead 3, the lower electrode 1g, the upper electrode 1d, and the lead frame 1i, but CuMo, 42 alloy, Al, Au, Ag, or the like may be used. In this case, in order to improve connection stability, it is preferable to plate the connection portion with the conductive bonding material with Au, Pd, Ag, Ni, or the like.

The control circuit chip 1c is electrically connected to the semiconductor element 1a via a wire 1 f. For example, when the semiconductor element 1a is a power MOSFET, the gate electrode formed on the semiconductor element 1a is connected to the control circuit chip 1c by the wire 1f, and the control circuit chip 1c controls the gate voltage of the power MOSFET. This enables a large current to flow through the semiconductor element 1a having a switching function.

The capacitor 1b is electrically connected to the semiconductor element 1a and the control circuit chip 1c via the lead frame 1i and the lead 1 f.

The semiconductor element 1a has a function of switching a large current. For example, the semiconductor element (switching circuit chip) 1a having a switching function is a semiconductor element including an IGBT, a GTO (Gate Turn-Off thyristor), and a power MOSFET. Further, a semiconductor element made of Si, SiC, SiN, GaAs, or the like, in which a semiconductor element such as a thyristor that controls on and off of a large current is formed, can also be used.

The control circuit chip 1c is a semiconductor device for controlling the semiconductor device 1a for switching a large current. The control circuit chip 1c itself is a semiconductor element that does not include a semiconductor element that switches a large current. That is, the control circuit chip 1c is a semiconductor element in which a plurality of logic circuits, analog circuits, driver circuits, and the like are formed, and a microprocessor and the like are formed as necessary. Further, the semiconductor device may also have a function of controlling a large current flowing through the semiconductor element 1 a.

The semiconductor element 1a, the control circuit chip 1c, the capacitor 1b, the lower electrode 1g, the upper electrode 1d, and the 1 st conductive bonding material 1e are integrally covered with a molding resin (1 st resin, resin of the circuit body) 1h and sealed to constitute an integrated circuit body 100.

Hereinafter, the side of the circuit body 100 where the lower electrode 1g and the lead frame 1i are disposed will be referred to as "1 st surface", and the opposite side, i.e., the side where the upper electrode 1d is disposed will be referred to as "2 nd surface". The lower electrode 1g and the lower surface side of the lead frame 1i and the upper surface side of the upper electrode 1d are not covered with the 1 st resin 1h of the circuit body 100, but are exposed on the surface of the circuit body 100.

Therefore, the upper surface of the upper electrode 1d of the circuit body 100 can be electrically connected to the lead 3a via the 2 nd conductive bonding material 4.

The lower surface of the lower electrode 1g of the circuit body 100 can be electrically connected to the base 2a via the 2 nd conductive bonding material 4.

The semiconductor device 200: second (2)

As described above, the circuit body 100 is integrally sealed with the 1 st resin 1h, and one surface of each of the lower electrode 1g and the upper electrode 1d is exposed on the surface of the circuit body 100. One surface of the exposed lower electrode 1g is electrically connected to the base 2a of the base 2 by the 2 nd electrically conductive bonding material 4, and one surface of the upper electrode 1d is electrically connected to the lead 3a of the lead 3 by the 2 nd electrically conductive bonding material 4, thereby constituting the semiconductor device 200.

In this structure, the upper electrode 1d connected to the source electrode S of the semiconductor element 1a is made thicker than the lower electrode 1 g. Here, thick means long in a direction from the base 2a toward the lead 3 a.

By making the upper electrode 1d thicker than the lower electrode 1g in this way, heat generated by loss when a current flows through the source electrode S can be efficiently dissipated to the upper electrode 1d side, and the cooling performance of the semiconductor device 200 can be improved.

The semiconductor element 1a mainly forms a transistor element on the surface on the side where the source electrode S is formed, and heat generation of the transistor element mainly occurs on the side where the source electrode S is formed. Therefore, it is effective to dissipate heat by the upper electrode 1 d. In order to dissipate heat by the upper electrode 1d, it is effective to increase the heat capacity of the upper electrode 1d and improve the heat conduction, and as described above, the upper electrode 1d is made thicker than the lower electrode 1 g.

Further, by thickening the upper electrode 1d, the upper electrode 1d has a structure in which a conductor can be exposed on the lead 3a side of the circuit body 100 and can be electrically connected to the lead 3a, i.e., the lead 3.

Next, the structure of the semiconductor device of the present embodiment will be described in detail with reference to fig. 2 and 3. Fig. 2 is a diagram schematically showing a longitudinal configuration in the vicinity of the semiconductor element 1a in fig. 1. Fig. 3 is a diagram schematically showing a planar configuration in the vicinity of the semiconductor element 1a in fig. 1. Fig. 2 corresponds to section a-a' of fig. 3. In fig. 2 and 3, only the semiconductor element 1a, the upper electrode 1d, the lower electrode 1g, and the 1 st conductive bonding material 1e disposed in the semiconductor device 200 are shown for easy understanding.

In fig. 2 and 3, the semiconductor element 1a has a gate electrode (control electrode) C and a source electrode S on the upper electrode 1D side, and has only a drain electrode D on the lower electrode 1g side. The semiconductor element 1a has a silicon oxide film (SiO) on the outer periphery of the surface on the gate electrode C side₂) An outer peripheral insulating layer L.

The surface (second main surface) of the semiconductor element 1a on the source electrode S side is connected to the lower surface of the upper electrode 1d via the 1 st conductive bonding material 1 e.

The surface (first main surface) on the drain electrode D side is connected to the upper surface of the lower electrode 1g via the 1 st conductive bonding material 1 e.

The length of the upper electrode 1d (the distance in the left-right direction of the upper electrode 1d in fig. 2) is shorter than the length of the semiconductor element 1a (the distance in the left-right direction of the semiconductor element 1a in fig. 2), and both the end of the upper electrode 1d and the end of the connection portion between the upper electrode 1d and the semiconductor element 1a are located inside the semiconductor element 1 a. In addition, the end of the lower electrode 1g connected to the semiconductor element 1a is aligned with the end of the upper electrode 1d in the vertical direction.

In order to form the circuit body 100 in the manufacturing of the semiconductor device 200 of the present embodiment, first, the 1 st conductive bonding material 1e is disposed between the upper electrode 1d and each of the semiconductor element 1a and the lower electrode 1g, and heated to a high temperature to connect the lower surface of the upper electrode 1d, the second main surface of the semiconductor element 1a, the upper surface of the lower electrode 1g, and the first main surface of the semiconductor element 1 a. The connection step is, for example, reflow soldering, flow soldering, or the like. At this time, in order to melt the 1 st conductive bonding material 1e, the entire semiconductor device 200 is heated to a temperature equal to or higher than the melting point of the bonding material, and then cooled to room temperature.

In the cooling process, thermal deformation occurs in all of the upper electrode 1d, the lower electrode 1g, and the semiconductor element 1 a. When the upper electrode 1d and the lower electrode 1g are Cu and the semiconductor element 1a is Si, the thermal expansion coefficients of the upper electrode 1d and the lower electrode 1g are about 16.8 x 10-6/K and 2.4 x 10-6/K, respectively, so that the upper electrode 1d and the lower electrode 1g contract more than the semiconductor element 1 a. This causes bending deformation of the upper electrode 1d, the lower electrode 1g, and the semiconductor element 1a, and causes thermal stress in the respective members.

Next, the operation and effect of the semiconductor device of the present embodiment will be described with reference to fig. 4 and 5. Fig. 4 shows a deformation diagram in a connecting process of a semiconductor device of a conventional structure, and fig. 5 shows a deformation diagram in a connecting process of a semiconductor device of the present embodiment. In fig. 4 and 5, the end portion of the semiconductor element 1a shown in the region Y of fig. 2 is enlarged for easy understanding.

As shown in fig. 4, in the conventional structure, the length of the lower electrode 1g is longer than that of the semiconductor element 1 a. Therefore, the connection portion connected to the lower electrode 1g extends to the end portion of the first main surface of the semiconductor element 1 a. On the other hand, the length of the upper electrode 1d is shorter than that of the semiconductor element 1 a. Therefore, with respect to the second main surface of the semiconductor element 1a, the connection portion between the upper electrode 1d and the semiconductor element 1a is formed inside the second main surface of the semiconductor element 1 a.

Since the length of the connection portion between the lower electrode 1g and the semiconductor element 1a is longer than the length of the connection portion between the upper electrode 1d and the semiconductor element 1a, the force transmitted from the lower electrode 1g to the semiconductor element 1a is larger than the force from the upper electrode 1d, and the bending deformation of the semiconductor element 1a during thermal contraction is convex upward as shown in fig. 4.

At a point p1 in fig. 4, the bending deformation of the semiconductor element 1a becomes large, the stretching (bending stress) of the arrow Tb is generated, and further the stretching (solder thermal stress) of the arrow Tj is simultaneously applied from the 1 st conductive bonding material 1e, so the stress concentrates on the point p 1. When a high-rigidity bonding material such as a lead-free solder or a sintered material is used as the 1 st conductive bonding material 1e, the stress at the stress concentration portion p1 becomes larger, and the risk of cracks entering the semiconductor element 1a further increases as compared with the case of a lead solder.

In contrast, as shown in fig. 5, in the semiconductor device 200 of the present embodiment, the length of the lower electrode 1g of the portion connected to the semiconductor element 1a via the 1 st conductive bonding material 1e is shorter than that of the semiconductor element 1 a. Therefore, the 1 st conductive bonding material 1e is not connected to the region D2 from the connection end portion of the first main surface of the semiconductor element 1a with the lower electrode 1g to the end portion of the semiconductor element 1a, and the bending deformation is smaller than that of the conventional structure.

Further, since both end portions of the lower electrode 1g in the region connected to the semiconductor element 1a and the end portion of the upper electrode 1d are aligned in the vertical direction, imbalance in vertical bending deformation is eliminated, and the stress concentration portion is dispersed to the point p1 and the point p2, so that the stress at the stress concentration portion p1 can be greatly reduced as compared with the conventional structure. Therefore, even when a lead-free bonding material having high rigidity such as a lead-free solder or a sintered material is used as the 1 st conductive bonding material 1e, a highly reliable semiconductor device can be manufactured. The structure of the present embodiment can be applied to a case where lead solder is used as the conductive bonding material 1 e.

Next, the effect of reducing the thermal stress in the connection step of the present invention will be quantitatively described with reference to fig. 6 and 7. Fig. 6 is a diagram showing the definition of parameters for explaining how the thermal stress generated in the semiconductor element 1a changes in the connection step when the length of the lower electrode 1g is changed in fig. 7. Fig. 7 is a result of examining how the thermal stress generated in the semiconductor element 1a changes in the connection step when the length of the lower electrode 1g is changed by the finite element method. In fig. 6, for ease of understanding, only the end portion of the semiconductor element 1a shown in the region Y of fig. 2 is enlarged.

In fig. 6, W represents the distance from the end of the connection surface (broken line E-E' in fig. 6) of the upper electrode 1d with the semiconductor element 1a to the end of the semiconductor element 1 a. J is a distance from an end of a connection surface with the semiconductor element 1a in the upper electrode 1d to an end of a connection surface with the semiconductor element 1a in the lower electrode 1 g. When the end of the connection surface with the semiconductor element 1a of the lower electrode 1g is located closer to the center of the semiconductor element 1a than the end of the connection surface with the semiconductor element 1a of the upper electrode 1d, J has a negative value.

Here, a parameter obtained by dividing J by W and normalizing is defined as X. X is a value obtained by dividing J by W and performing dimensionless transformation. In the conventional structure shown in fig. 4, since the lower surface of the semiconductor element 1a is connected to the lower electrode 1g over the entire surface, X is 1.

In contrast, in the semiconductor device of the present invention shown in fig. 5, J is smaller than W because the length of the lower electrode 1g of the portion connected to the semiconductor element 1a via the 1 st conductive bonding material 1e is shorter than that of the semiconductor element 1 a. Thus, X takes any value less than 1 (however, the lower limit is limited). In the semiconductor device 200 of the present embodiment shown in fig. 2, the upper electrode 1d and the lower electrode 1g have the same size, J is 0, and X is 0.

The horizontal axis of fig. 7 represents the parameter X defined in the above. The range of the horizontal axis varies from-1.5 to 1. In the vertical axis of fig. 7, the thermal stress generated in the semiconductor element 1a when the parameter X is changed in the semiconductor device of the present invention is normalized by the stress at the stress concentration point p1 of the conventional structure shown in fig. 4.

In the conventional structure of fig. 4, the normalized stress is 1 corresponding to X being 1. The stress at the stress concentration site p1 on the upper electrode 1d side of the semiconductor element 1a shown in fig. 5 is indicated by a black circle (●), and the stress at the stress concentration site p2 on the lower electrode 1g side of the semiconductor element 1a is indicated by a black triangle (a). The larger of the stresses generated at the stress concentration point p1 and the stress concentration point p2 is the largest stress generated in the semiconductor element 1 a.

As shown in fig. 7, the stress at the stress concentration point p1 increases as the parameter X increases, that is, as the lower electrode 1g is longer and the connection length between the lower electrode 1g and the first main surface of the semiconductor element 1a is longer. This is because the force transmitted from the lower electrode 1g to the semiconductor element 1a is larger than the force from the upper electrode 1d, and the bending deformation of the semiconductor element 1a during thermal contraction is convex upward as shown in fig. 4.

On the other hand, the smaller the parameter X, that is, the shorter the lower electrode 1g, the shorter the connection length between the lower electrode 1g and the first main surface of the semiconductor element 1a, the greater the stress at the stress concentration point p 2. This is because the force transmitted from the upper electrode 1d to the semiconductor element 1a is larger than the force from the lower electrode 1g, and the bending deformation of the semiconductor element 1a during thermal contraction is convex downward.

Since the stresses at the stress concentration point p1 and the stress concentration point p2 have a trade-off relationship in this way, there is a parameter X that minimizes the stress generated in the semiconductor element 1 a. As is clear from fig. 7, when X is 0 (corresponding to the structure of fig. 2), the stress generated in the semiconductor element 1a is the smallest, and is about half of that in the conventional structure (X is 1). That is, the end of the lower electrode 1g connected to the semiconductor element 1a is preferably aligned with the end of the upper electrode 1d in the vertical direction.

In addition, in view of the definition of the parameter X, in the conventional structure, the upper electrode 1d is enlarged so that the end portion of the upper electrode 1d, the end portion of the semiconductor element 1a, and the end portion of the lower electrode 1g are aligned in the vertical direction, whereby X can be geometrically set to 0. However, since the outer peripheral insulating layer L having poor wettability with solder is present on the second main surface of the semiconductor element 1a, and the gate electrode C is present in the vicinity thereof, it is necessary to electrically insulate them from the upper electrode 1d, and therefore, in a structure in which the entire first main surface of the semiconductor element 1a is connected as in the conventional structure, a semiconductor device that operates when X is 0 cannot be realized.

The effect of the present invention is not limited to the case where the parameter X is 0. For example, when W is 0.4mm and J is 0.2mm in fig. 6, X is 0.5, and it is understood from fig. 7 that the stress can be reduced by about 20% as compared with the conventional structure.

Therefore, even when X is not equal to 0 due to the structural constraint of the circuit body 100, according to the present invention, by bringing X close to 0 within a possible range, it is possible to reduce stress at the time of the connection process.

In other words, the semiconductor device 200 of the present embodiment described above is configured to include the semiconductor element 1a having the gate electrode C on only one surface, the upper electrode 1d connected to the surface (second main surface) of the semiconductor element 1a having the gate electrode C, and the lower electrode 1g connected to the surface (first main surface) of the semiconductor element 1a opposite to the surface having the gate electrode C, the connection end portion of the upper electrode 1d to the surface (second main surface) of the semiconductor element 1a having the gate electrode C is located inward of the end portion of the surface (second main surface) of the semiconductor element 1a having the gate electrode C, and the connection end portion of the lower electrode 1g to the surface (first main surface) of the semiconductor element 1a on the opposite side is located inward of the end portion of the surface (first main surface) of the semiconductor element 1a on the opposite side.

The upper electrode 1d is connected to the semiconductor element 1a via a 1 st conductive bonding material 1e, the lower electrode 1g is connected to the semiconductor element 1a via a 2 nd conductive bonding material (1e), and an end of a connection portion between the 1 st conductive bonding material 1e and the upper electrode 1d and an end of a connection portion between the 2 nd conductive bonding material (1e) and the lower electrode 1g are substantially aligned in the vertical direction.

As in the modification shown in fig. 12, the end of the connection portion between the 1 st conductive bonding material 1e and the upper electrode 1d, the end of the connection portion between the 2 nd conductive bonding material (1e) and the lower electrode 1g, the end of the connection portion between the 1 st conductive bonding material 1e and the semiconductor element 1a, and the end of the connection portion between the 2 nd conductive bonding material (1e) and the semiconductor element 1a may all be substantially aligned in the vertical direction.

[ example 2 ]

Next, a semiconductor device according to embodiment 2 of the present invention will be described with reference to fig. 8 and 13. Fig. 8 is a diagram schematically showing a cross section of a vertical structure of a semiconductor device (rectifier element) 300 for a vehicle-mounted Alternator (Alternator) according to the present embodiment. Fig. 13 is a modification of fig. 8, and corresponds to fig. 2 of example 1.

In example 1, a semiconductor element having a switching function such as a MOSFET is used, whereas in this example, a semiconductor element (diode) having a rectifying function is used.

In fig. 8, the semiconductor device 300 includes a base (1 st external electrode, 1 st external terminal) 20 having a convex base (1 st electrode surface portion) 20a on an upper portion (upper side of the paper surface in fig. 8), a lead (2 nd external electrode, 2 nd external terminal) 30 having a lead head (2 nd electrode surface portion) 30a on a lower portion (lower side of the paper surface in fig. 8), and a semiconductor element 10 a.

The base 20a is directly connected to a semiconductor element 10a via a conductive bonding material (bonding material of a semiconductor device) 10e, and the semiconductor element 10a is a diode having an insulating layer L on only one surface at the outer peripheral portion of the chip. The lead 30a is directly connected to the semiconductor element 10a which is a diode via the conductive bonding material 10 e.

The length of the lead 30a (the distance in the left-right direction of the lead 30a in fig. 8) is shorter than the length of the semiconductor element 10a (the distance in the left-right direction of the semiconductor element 10a in fig. 8), and both the end of the lead 30a and the end of the lead 30a at the connection portion with the semiconductor element 10a are located inside the semiconductor element 10 a. The end of the base 20a and the end of the lead 30a are aligned in the vertical direction.

Further, a part of the base 20a and the upper portion of the base 20, a part of the lead 30a and the lower portion of the lead 30, and the semiconductor element 10a are covered and sealed with a mold resin (resin of a semiconductor device) 50.

In the present embodiment, since the semiconductor element 10a itself, which is a diode, has a rectifying function, unlike embodiment 1, the semiconductor element 10a can be directly connected to the base (1 st external electrode) 20 and the lead (2 nd external electrode) 30 without constituting the circuit body 100, and therefore, the semiconductor device can be provided at a lower cost.

Further, since the vertical structure similar to that of example 1 can be realized by vertically aligning the end portion of the base 20a and the end portion of the lead 30a, thermal stress generated in the semiconductor element 10a in the connection step can be reduced.

In addition, since the Alternator (Alternator) requires P-type and N-type rectifier elements, it is necessary to manufacture two types of semiconductor devices in which the orientation of the semiconductor element 10a is inverted in the vertical direction (P-pole and N-pole are inverted) in fig. 8. In the present embodiment, since the end portion of the base 20a and the end portion of the lead 30a are aligned in the vertical direction, the connection method does not change even if the semiconductor element 10a is inverted. Thus, a highly reliable semiconductor device can be manufactured by both P-type and N-type.

Fig. 13 is a modification of the present example (fig. 8) in which the semiconductor element 1a of example 1 (fig. 2) is replaced with a diode having a P/N junction. The components other than the diode are the same as those in fig. 2, and redundant detailed description is omitted. As in example 1 (fig. 2), the semiconductor device 300 may be configured by connecting the upper electrode 1d and the lower electrode 1g to the semiconductor element 10a which is a diode.

That is, in other words, the semiconductor device 300 of the present embodiment described above is configured to include the semiconductor element 10a having the outer peripheral insulating layer L on only one surface at the chip outer peripheral portion, the upper electrode 1d connected to the surface of the semiconductor element 10a having the outer peripheral insulating layer L, and the lower electrode 1g connected to the surface of the semiconductor element 10a opposite to the surface having the outer peripheral insulating layer L, the semiconductor element 10a being a diode formed by a P/N junction, the connection end of the upper electrode 1d to the surface of the semiconductor element 10a having the outer peripheral insulating layer L is located inward of the end of the surface of the semiconductor element 10a having the outer peripheral insulating layer L, and the connection end of the lower electrode 1g to the surface of the semiconductor element 10a on the opposite side is located inward of the end of the surface of the semiconductor element 10a on the opposite side.

[ example 3 ]

Next, a semiconductor device according to embodiment 3 of the present invention will be described with reference to fig. 9 to 11. The structure of this embodiment is the same as the semiconductor device 200 of embodiment 1 except for the connection form of the semiconductor element 1a and the lower electrode 1g, and therefore, redundant description about the entire structure of the semiconductor device is omitted.

Fig. 9 is a diagram schematically showing a planar structure in the vicinity of the semiconductor element 1a in the semiconductor device of the present embodiment. Fig. 10 and 11 are diagrams schematically showing the vertical structure in the vicinity of the semiconductor element 1a in the semiconductor device of the present embodiment. Fig. 10 corresponds to the section B-B 'of fig. 9, and fig. 11 corresponds to the section C-C' of fig. 9. In fig. 9 to 11, only the semiconductor element 1a, the upper electrode 1d, the lower electrode 1g, and the 1 st conductive bonding material 1e disposed in the semiconductor device 200 are shown for easy understanding.

As shown in fig. 9 and 10, in the semiconductor device of the present embodiment, the corner portions 7a, 7b, 7c, and 7d of the semiconductor element 1a are configured as follows: the ends 8a, 8b, 8c, and 8d (8 c and 8d not shown) of the lower electrode 1g are inside the semiconductor element 1a and aligned with the ends of the upper electrode 1 d.

Therefore, the vicinity of the corner of the semiconductor element 1a has the same vertical structure as in example 1 (fig. 2).

As shown in fig. 9 and 11, in the semiconductor device of the present embodiment, in regions other than the corner portions 7a, 7b, 7c, and 7d of the semiconductor element 1a, the length of the lower electrode 1g of the portion connected to the semiconductor element 1a via the 1 st conductive bonding material 1e is longer than the length of the semiconductor element 1a, and therefore, the lower electrode is connected to the end portions 9a and 9b of the semiconductor element 1 a.

The thermal stress generated in the connection step becomes particularly high in the vicinity of the corner portions 7a, 7b, 7c, and 7d of the semiconductor element 1 a. Therefore, suppressing the stress at the corner is effective for preventing the crack of the semiconductor element.

Therefore, in the present embodiment, the same connection method as in embodiment 1 (fig. 2) is adopted only in the vicinity of the corner of the semiconductor element 1 a. In the region other than the vicinity of the corner of the semiconductor element 1a, the contact area between the semiconductor element 1a and the lower electrode 1g is larger than that in example 1 (fig. 2). This can suppress stress at the corner of the semiconductor element and improve heat dissipation.

The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments are described in detail to explain the present invention easily and understandably, and are not necessarily limited to examples having all the structures described. Further, a part of the structure of one embodiment may be replaced with the structure of another embodiment, and the structure of another embodiment may be added to the structure of one embodiment. In addition, as for a part of the configuration of each embodiment, addition, deletion, and replacement of other configurations can be performed.

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