JP2569109B2 - Pressure contact type semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure contact type semiconductor device having a self-extinguishing function, and more particularly to connection of an electrode plate suitable for improving current interruption performance.

[Conventional technology]

In a conventional pressure-contact type semiconductor device, particularly in a structure in which a semiconductor substrate is not brazed to a tungsten or molybdenum support plate by alloying, for example, as described in JP-A-47-4715, extensibility is applied to both main surfaces of the semiconductor substrate. In this structure, a metal plate is disposed, and a pressure contact is made with a post electrode via a stress buffer plate adjacent to the metal plate. The spreadable metal plate and the stress buffer plate are symmetrically arranged around the semiconductor substrate.

[Problems to be solved by the invention]

The above prior art has a structure in which the semiconductor substrate, the extensible metal and the stress buffering plate are all in contact with each other under pressure, so that especially the GT
When an electrode of a semiconductor substrate is divided into a large number of pieces, such as an O-thyristor, no consideration has been given to the point of uniformly and mechanically contacting the entire surface of the divided electrodes. When a non-uniform pressing force is applied to the semiconductor substrate, the contact resistance between many electrodes of the semiconductor substrate and the metal plate in contact therewith becomes non-uniform, and in the case of a GTO thyristor, the current sharing of the many electrodes is divided. The current becomes non-uniform and the current concentrates on the electrode having a small contact resistance. At the time of current interruption (turn-off), the current concentration is further increased, and the current interruption performance of the entire semiconductor substrate is reduced. If the current interruption is severe, the element cannot be interrupted or the element is destroyed at a portion where the current is concentrated. SUMMARY OF THE INVENTION An object of the present invention is to uniformly and electrically and mechanically connect electrodes formed on both main surfaces of a semiconductor substrate and a metal plate in contact with the electrodes, thereby dispersing current uniformly to a large number of electrodes, and improving current interrupting performance. To improve.

[Means for solving the problem]

This object is achieved by metallurgically bonding the electrodes formed on one main surface of the semiconductor substrate with a thin metal plate, and in particular, by connecting a plurality of divided electrodes in parallel with the thin metal plate. You.

Further, if a thin metal plate is bonded to an electrode formed on the other main surface of the semiconductor substrate, a favorable result for achieving the object can be obtained. Here, the thin metal plate is molybdenum,
Made of materials selected from tungsten, gold, silver and copper,
It is a metal plate having a thickness of 0.5 mm or less, preferably around 0.1 mm.

[Action]

Adhesion of a thin metal plate to an electrode formed on one main surface of a semiconductor substrate means that a large number of electrodes are integrated by a thin metal plate on one main surface where the electrodes are divided into a number of pieces. It is possible to eliminate the contact resistance between the plurality of electrodes and the metal plate. Therefore, the distribution of the current flowing through the multiple electrodes is made uniform, so that the current concentration at the time of current interruption can be reduced, and the current can be safely interrupted. In addition, if the electrode and the thin metal plate are bonded on the other main surface, deformation of the semiconductor substrate itself due to bonding of a material different from that of the semiconductor substrate is prevented, and furthermore, between the thin metal plate and the stress buffer plate opposed thereto. Contact resistance can also be reduced. This means
On the other hand, it means that the effects of the present invention can be expected even when the electrodes formed on the main surface are not divided into a large number.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view of a press-contact type GTO thyristor. On a cathode surface of a semiconductor substrate 1 having a disk shape, a thin disk-shaped cathode electrode plate 4 is adhered to a plurality of cathode electrodes 2 in ohmic contact. On the anode side,
A thin disk-shaped anode electrode plate 5 is bonded to the undivided anode electrode 3. The cathode electrode plate 4 is pressed by the cathode post electrode 8 via the disk-shaped cathode stress buffer plate 6, and the anode electrode plate 5 is pressed by the anode post electrode 9 via the disk-shaped anode stress buffer plate 7. In contact. On the other hand, the gate electrode 12 is brought into pressure contact with the gate lead 13 at a constant pressure by the disc spring 10 via the gate insulator 14 and the washer 11. The semiconductor substrate 1 is hermetically sealed in a container formed by the post electrodes 8 and 9, the insulator 15 and the flanges 16 and 17. FIG. 2 is an enlarged view of a main part of FIG. The thickness of the cathode electrode plate 4 and the anode electrode plate 5 that are bonded to the cathode electrode 2 and the anode electrode 3 of the semiconductor substrate 1 are set so that excessive stress is not applied to the semiconductor substrate 1 at the time of bonding or when the semiconductor device is operated. It is desirable that the thickness be about 0.5 mm or less and about 0.1 mm.
And if the material is molybdenum or tungsten,
Since the coefficient of thermal expansion is close to that of silicon or the like, which is the material of the semiconductor substrate 1, the stress applied to the semiconductor substrate is small and the reliability is high. In addition, when the material is made of copper, silver, gold, or the like, the electrical and thermal conductivity is good, so that the characteristics of the semiconductor device as a whole are improved. Coefficient of thermal expansion is semiconductor substrate 1
The longitudinal elastic coefficient, which is largely different from that described above, is small, and since it is a thin plate, the stress applied to the semiconductor substrate 1 is small and no inconvenience occurs. Further, by making the thicknesses of the cathode electrode plate 4 and the anode electrode plate 5 the same, it is possible to prevent the semiconductor substrate 1 from being bent due to adhesion of different materials.

On the other hand, the cathode stress buffer plate 6 and the anode stress buffer plate 7
Are a cathode post electrode 8 and an anode post electrode 9 which are usually made of copper and have a large thermal expansion coefficient different from that of the semiconductor substrate 1.
Molybdenum or tungsten having a plate thickness of 1 mm or more and a thermal expansion coefficient close to that of the semiconductor substrate and a sufficiently large longitudinal elastic coefficient than copper is used to alleviate the thermal stress received from the substrate.

According to this embodiment, since the cathode electrode 2 divided into a large number is bonded and integrated with the cathode electrode plate 4, the best parallel operation is possible without contact resistance due to uneven pressurization. Since the electrode 3 is bonded with the anode electrode plate to reduce the effect of bonding the cathode electrode plate 3,
GTO thyristor performance can be fully exploited. Further, the semiconductor device having the structure of the present embodiment is applied to not only a GTO thyristor but also a pressure-contact type semiconductor device which controls a relatively large current, such as a pressure-contact thyristor transistor, a diode, and an SI thyristor. Characteristics can be maximized.

〔The invention's effect〕

According to the present invention, a large number of electrodes arranged on a semiconductor substrate are uniformly adhered to each other with a thin electrode plate, so that contact resistance between the electrodes and the electrode plate can be eliminated. Since an increase in current concentration at the time of current interruption due to non-uniformity and non-uniform contact resistance can be reduced, there is an effect that current interruption performance is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a press contact type GTO thyristor of one embodiment of the present invention, and FIG. 2 is an enlarged view of a main part of FIG. DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Cathode electrode, 3 ... Anode electrode, 4 ... Cathode electrode plate, 5 ... Anode electrode plate, 6 ... Cathode stress buffer plate, 7 ... Anode stress plate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kogo Otai 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Hitachi, Ltd. Hitachi Plant (72) Inventor Masafumi Ono 3-chome, Bentencho, Hitachi-shi, Ibaraki No. 2 Sun Tachihara Town Electronics Co., Ltd.

Claims (3)

(57) [Claims] 1. A semiconductor substrate having at least one PN junction between a pair of main surfaces, one electrode divided into a number of pieces by ohmic contact with one main surface of the semiconductor substrate, and mounted on one electrode. And a first electrode attached to each of the one electrodes
An electrode plate, a second electrode plate mounted on the first electrode plate, having a larger thermal expansion coefficient than the first electrode plate and having a thermal expansion coefficient close to that of the semiconductor substrate, and a second electrode plate mounted on the second electrode plate. And a first metal post electrode for pressing the second electrode plate against the first electrode plate. 2. A disk-shaped semiconductor substrate having at least one PN junction between a pair of main surfaces, a plurality of one electrodes in ohmic contact with one main surface of the semiconductor substrate, and the other main surface of the semiconductor substrate. A sub-assembly including the other electrode in ohmic contact with the first electrode and a disc-shaped first electrode plate adhered to the plurality of one electrodes, the first electrode having a thermal expansion coefficient similar to that of the semiconductor substrate; A press-contact type semiconductor device characterized in that a pair of metal post electrodes presses through a pair of second electrode plates having a disc shape thicker than a plate. 3. The pressure-contact type semiconductor device according to claim 2, wherein the first electrode plate is made of a material selected from tungsten, molybdenum, gold, silver, and copper.