JPH036659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor device having an annular control electrode, and particularly to an improvement in a control electrode extraction structure of the semiconductor device.

[Prior art]

In large capacity gate turn-off thyristors and transistors, the current flowing through the control electrode (gate or base) increases as the capacity increases.
Recently, devices that flow currents of several 10A to several 100A have been put into practical use. In particular, large-capacity gate turn-off thyristors require a large gate reverse current during turn-off, and the current must flow instantaneously and uniformly, so efforts have been made to minimize the impedance between the gate and cathode. For example, the shape of the lead-out portion of the gate electrode is annular to shorten the distance from the lead-out portion to the emitter region and to equalize and reduce the current distribution.

FIG. 1 is a plan view of an element of a conventional semiconductor device, particularly a gate turn-off thyristor having an annular gate electrode structure. In Figure 1, 1
1a is an element which is a semiconductor substrate, 1a is a silicon wafer, 1b is a reinforcing plate that supports this silicon wafer 1a, 1c is a gate electrode, 1d is a cathode electrode, 1e and 1f are current collecting electrode parts of the gate electrode 1c. .

The conventional gate turn-off thyristor shown in FIG. 1 directly connects the gate electrode 1c of the element 1 to an external gate electrode (not shown) mainly by wire bonding, and FIG. FIG. 3 is a perspective view showing the extraction structure of FIG.

In Fig. 2, 2 is a gate lead-out electrode made of aluminum wire for bonding, and this aluminum wire usually has a diameter of 0.3 to 0.7 mm, and this aluminum wire controls the distribution of gate current. In order to make it uniform, from several places to several places at approximately equal intervals to the annular current collecting electrode 1e of the element 1.
It is necessary to perform bonding in 10 places.

With this conventional equipment, the electrical resistance of the aluminum wire itself used for bonding cannot be ignored, especially the
When passing a large current of 100A, if the resistance of this aluminum wire part is large, when cutting off the main current,
The carrier is not discharged from the gate sufficiently,
As a result, the controllable current of the gate turn-off thyristor may be reduced.

On the other hand, as the capacity of gate turn-off thyristors increases, the diameter of the element also increases.
Along with this, the wiring length of the gate extraction current 2 described above becomes longer, and the gate current required at the time of interruption increases, so it is necessary to further lower the electrical resistance of the gate wiring portion.

A conventional method for supplying a large current to the gate by lowering the electric resistance of the gate wiring part is to bring the gate lead electrode into pressure contact with the element. It is very effective when used in structured thyristors, large capacity transistors, etc.

Figure 3 shows examples of such conventional and semiconductor devices.
FIG. 2 is a cross-sectional view of a thyristor having a structure in which a gate lead-out electrode is brought into pressure contact with an element.

In FIG. 3, 1 is a thyristor element, 3 is an insertion plate, 4 is an external cathode, 5 is a gate lead, and 6 is an insulating support for positioning the gate lead 5 and the insertion plate 3 relative to the external cathode 4. A member 7 is the tip 5a of the gate lead 5 (corresponding to the gate lead electrode 2 in FIG. 2).
8 is a protective tube for insulating the gate lead 5 from the external cathode 4;
10 is an external cathode, 10 is a ceramic cylinder that supports the element 1 of the thyristor, 11 is a flange on the cathode side that firmly supports the external cathode 4 on the ceramic cylinder 10, 12 is a flange on the anode side that supports the external anode 9, 13 is an external gate electrode (control electrode).

In the conventional thyristor shown in FIG. 3, there is no need to bond the element 1 and the gate lead 5.
It is possible to increase the diameter of the wire, or to use a material (for example, silver, etc.) with better conductivity than aluminum for the wire, which is advantageous for supplying a large current.

However, the insulating support member 6 has poor dimensional accuracy because it is necessary to use an alumina sintered body or the like that has excellent insulation, heat resistance, and mechanical strength.
Therefore, the clearance between the external cathode 4 and the insulating support member 6 and the clearance between the insulating support member 6 and the gate lead 5 have to be increased, resulting in poor positioning accuracy and, as a result, the conventional gate Since the extraction structure requires highly accurate positioning, it has the drawback of being insufficiently accurate for use in gate turn-off thyristors.

In addition, in the case of an annular gate turn-off thyristor, in order to adopt the conventional structure shown in FIG. A pressurized contact gate structure that allows for easy and highly accurate positioning has not been put into practical use.

[Concept of the invention]

This invention was made in order to eliminate the drawbacks of the conventional gate lead-out structure as described above, and a substantially annular control electrode lead-out electrode is provided to connect the control electrode of the semiconductor substrate to an external control electrode. The recessed portion of the external electrode that accommodates the control electrode extraction electrode is coated with an insulating film, and the control electrode extraction electrode is brought into pressure contact with the control electrode, whereby the control electrode can be extracted easily and with high precision. The present invention provides a highly reliable semiconductor device that can perform the following steps. Embodiments of the present invention will be described below with reference to the drawings.

[Embodiments of the invention]

FIG. 4 shows the structure of a gate turn-off thyristor according to an embodiment of the present invention.

In FIG. 4, 1 is an element which is a semiconductor substrate, 14 is a gate lead-out electrode, and a ring-shaped metal part 1
4a and a wire portion 14b. 15 is an outer insertion plate inserted between the outer circumference of the cathode electrode of the element 1 and the outer cathode 18 which is the first outer main electrode; 16 is an outer insertion plate inserted between the outer circumference of the cathode electrode of the element 1 and the outer cathode 18 This is an inner insertion plate inserted between the two. An annular holding groove 18a is recessed in the cathode side of the external cathode 18, and the holding groove 1
An insulating coating 18c is applied to the inner surface of 8a. An annular gate lead-out electrode 14 is inserted into the holding groove 18a so as to be able to move up and down, and this gate lead-out electrode 14 is connected to the fourth hole by a spring 17 inserted between the bottom surface of the holding groove 18a and an insulating coating 18c. It is urged downward in the figure and comes into pressure contact with the gate electrode portion of element 1. Also, 10, 11, 1
2 and 13 are the same as those in Figure 3, and 1
9 is an external anode.

FIG. 5 is a perspective view showing the detailed structure of the external cathode 18 in FIG. In FIG. 5, 18d is an electrode block which is the main body of the external cathode 18, 18a is an annular holding groove provided on the surface where the external cathode 18 contacts the element 1, and 18b is adjacent to this holding groove 18a. The linear groove portion 18c for housing the gate lead provided therein is an insulating coating applied to the inner surfaces of the annular holding groove 18a and the linear groove portion 18b.

Next, a method for manufacturing the external cathode 18 will be explained.

(a) First, the electrode block 18d is formed by cutting with the desired precision, and after masking the parts excluding the annular retaining groove 18a and the linear groove portion 18b, alumina or boron nitride is applied to the annular retaining groove 18a. and straight groove portion 18b
sprayed on. When copper is used as the material for the electrode block 18d, the thickness of the alumina sprayed is approx.
Although it can be applied up to 500 μm, due to limitations such as the mechanical strength, electrical insulation, and dimensional accuracy of this film,
A thickness of 100 to 300 μm is most suitable.

(b) Next, the external cathode 18 that has been thermally sprayed, the flange 11, the ceramic cylinder 10, and the external gate electrode 13 are brazed together.

In the above embodiment, a gate turn-off thyristor has been described, but the present invention can be similarly applied to a large-capacity semiconductor device having an annular control electrode, such as a high-power transistor or a gate-assisted turn-off thyristor.

Further, the present invention can be applied not only to the structure for taking out the annular gate electrode 1c but also to the gate taking-out electrode 14 of the conventional center gate structure, thereby improving workability and positioning accuracy.

Further, in the gate turn-off thyristor of this embodiment, the annular metal portion 14 of the gate lead-out electrode 14
Since the electrode resistance of a is extremely small and the wire diameter of the wire portion 14b of the gate lead-out electrode 14 is sufficiently large, the potential drop of the gate lead-out electrode 14 can be made extremely small.

Although the above description has been made using the gate electrode 1c and the gate extraction electrode 14, they are generally referred to as the control electrode 1c and the control electrode extraction electrode 14.

〔Effect of the invention〕

As explained in detail above, the present invention provides a part of the external cathode with an annular holding groove for holding a control electrode extraction electrode for taking out the control electrode to the outside, and the control electrode extraction electrode is disposed on the bottom surface of the annular holding groove. Since a spring is provided on the upper surface of the holding groove so as to come into pressure contact with the control electrode, and an insulating coating is coated on the inner surface of the holding groove, there is no need for wire bonding and it is possible to take out the control electrode. By reducing the potential drop of the electrode, the blocking ability of the gate turn-off thyristor can be improved.

In addition, since the insulating support member in the gate pressure welding structure is no longer required, the conventional work of engaging the gate extraction wire and the insulating support member is no longer necessary. The metal part has the advantage of extremely good positioning accuracy.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the cathode/gate pattern of a gate turn-off thyristor having a conventional gate structure, and Fig. 2 is a perspective view showing the gate turn-off thyristor of the device shown in Fig. 1 with wire bonding for gate extraction. , FIG. 3 is a sectional view showing the structure of a conventional center gate pressurizing thyristor, FIG. 4 is a sectional view showing a gate turn-off thyristor according to an embodiment of the present invention, and FIG.
This figure is a perspective view showing the structure of the external cathode electrode in FIG. 4. In the figure, 1 is an element, 10 is a ceramic cylinder,
11 and 12 are flanges, 13 is an external gate electrode,
14 is a gate extraction electrode, 14a is a ring-shaped metal part,
14b is a wire portion, 15 is an outer insertion plate, 16 is an inner insertion plate, 17 is a spring, 18 is an external cathode, 19 is an external anode, 18a is a holding groove, 18b is a groove portion, 1
8c is an insulating film, and 18d is an electrode block. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A semiconductor substrate having a cathode and a control electrode on one surface and an anode on the other surface, an external cathode electrically connected to the cathode, and an external cathode electrically connected to the anode. In the semiconductor device, the semiconductor device includes an external anode, and a control electrode lead-out electrode that is electrically connected to the control electrode, and a ring-shaped holding groove for holding the control electrode lead-out electrode in a part of the external cathode. an insulating film is applied to the inner surface of the holding groove, the control electrode extraction electrode is housed in the holding groove, and the control electrode extraction electrode in the holding groove is pressed against the control electrode. A semiconductor device characterized by being equipped with a spring. 2. The semiconductor device according to claim 1, wherein the insulating film is made of a sintered product of an insulating material containing aluminum oxide as a main component. 3. The semiconductor device according to claim 1, wherein the insulating film is made of a sintered product of an insulating material containing boron nitride as a main component. 4. Claims 1 to 3, characterized in that the insulating film has a thickness of 100 to 300 μm.
3. The semiconductor device according to any one of the items. 5. Claims 1 to 4, characterized in that the contact portion between the control electrode extraction electrode and the control electrode is annular and concentric with the outer periphery of the semiconductor substrate.
3. The semiconductor device according to any one of the items.