DE2341211A1 - Thyristor with long gate zone edge - reduces voltage rise-time without producing localised high-density currents - Google Patents

Abstract

The thyristor has its gate zone edge made as long as possible compared to the zone area so that the voltage risetime can be reduced without producing localised high-density currents which might damage the thyristor. The gate zone may be star-shaped, or composed of separate sub-zones, or form a grid or strip arrangement, or be circular. The contact is smaller than the gate's area. The non-contact part of the gate is covered with an insulating layer, and this layer and the contact are then metallised. The insulating layer extends as far as the cathode's contact.

Description

Licentia Patent Verwaltungs-G.m.b.H. 6 Frankfurt / Main 70, Theodor-Stern-Kai 1

Dr. Lertes / gö FBE 72/27

6.8.1973 »- = .—« -

"Thyristor"

The invention relates to a thyristor with at least four zones of alternately opposite conduction types and at least one control surface provided with a contact.

The ignition of a thyristor by means of a control pulse occurs in the first stage, i.e. within a few / US, after the ignition pulse has been fed in only at the points of the cathode, which are immediately adjacent to the control surface. From there, the ignited area spreads with conventional ones Components at a speed of about 100 m / sec over the entire cathode surface. Under the In the following, the control surface of a thyristor becomes the area of a cathode zone which acts as an emitter understood inner zone, which actively participates in the ignition mechanism. This area is usually not to be equated with the expansion of the control contact. Even with a normal tax system, that consists of one to one internal If there is an ohmic contact attached to the zone, the effective part of the system is larger than the geometric extent of the Contact. In a so-called pn control system, the Control surface determined by the area of the part of the opposite conduction type embedded in the inner zone,

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while the control contact covers only a part of this area. The same goes for the so-called reinforcing Control systems.

To avoid excessive local current density, the can possibly lead to the destruction of the component, di / dt is a high current rate of rise The largest possible edge of the control surface is required. There are different structures of such so-called extended ones Control surfaces become known, such as. B. a star-shaped design of the control surface.

These extended control systems, however, have some problems with the allowable rate of voltage rise you / dt. When applying a reverse voltage in the forward direction with a high voltage rise rate a capacitive current flows through the blocking layer, which is stressed in the reverse direction. This capacitive current can at least in the event that the current amplification factors of the two sub-transistors functionally forming the thyristor are still small, can be viewed as relatively homogeneous over the entire thyristor surface.

The 'invention is based on the knowledge that this Homogeneity as a result of an undesirable increase in the current density at the cathode edges opposite the control surface is disturbed. This disturbance results from the fact that when the control surface is not short-circuited on the cathode side Capacitive current flowing under the control contact via the middle barrier layer is applied from the cathode edge regions must become. Because of the non-linearity of the diode characteristic that is established between the control and the cathode contact this current is particularly limited to the immediate cathode edge area. Since the current density increases the ignition current already at the onset of the The thyristor is triggered, although the homogeneous current density would not be sufficient to trigger it this effect reduces the allowable rate of voltage rise.

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The invention is therefore based on the object To improve thyristor with an extended control surface so that the allowable rate of voltage rise increases will.

This object is achieved according to the invention in that in one provided with a contact extended Control surface the ratio of circumference to area is chosen as large as possible. ·

An extended control surface differs from a practically punctiform control contact, which for example can have a circular extension of 1 to 3 mm due to the fact that its area is much larger, wherein in the known cases the control surface is arranged in a star shape with respect to the cathode surface. The invention can be verified in a simple manner by the fact that in a known thyristor with a given control surface this is reduced to a technically justifiable degree.

In a preferred embodiment of the invention, the extensive control surface is in a plurality of spaced apart divided into separate control surfaces. The control surfaces can be arranged in a strip, network, star or ring shape be, wherein the contacted control surfaces are connected to one another in an electrically conductive manner.

In a further development of the invention, the control contact is smaller than the control surface with which it contacts. Around to supply the necessary ignition current to the individual contacts, the control system is advantageously designed such that the non-contacted part of the control surface is provided with an insulating layer, and that on at least one part the insulating layer has a metallization covering the contact, the insulating layer also being over the The control surface may also extend to part of the emitter of the thyristor.

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A uniform control system consisting of a plurality of control surfaces is achieved in that the Connect the insulating layers of the individual control surfaces to one another and, apart from the contacts, a closed one the geometric arrangement of the control surface form the predetermined path, and that the metallization on this path is the individual Electrically connects contacts with one another.

The essence of the invention will be explained with the aid of a few figures

FIG. 1 shows an embodiment of the invention with a star-shaped arrangement of the control surfaces;

Figure 2 shows a thyristor according to the invention in cross section A-A according to Figure 1;

FIG. 3 shows a modification of the thyristor according to FIG.

In the figures, the same parts are provided with the same reference numerals.

The thyristor according to FIGS. 1 and 2 consists of a semiconductor body 1 with four zones alternately opposite one another Line types 2, 3, 4 and 5. Zone 5, which acts as an emitter, is partially provided with a cathode contact 10. Control contacts 7 are ohmic on the inner zone 4. Contacts provided and arranged in a star shape. The control surface 6 is in one direction through the edge area of the emitter 5 is limited. In the embodiment, an insulating layer 8 covers the control surface 6 and one Part of the emitter 5, wherein, as can be seen from FIG. 1, the insulating layers surrounding the individual contacts are attached to one another connect and are strip-shaped except for the contacts themselves. The insulating layer 8 is with a Metallization 9 covered, which connects the control contacts and is designed so that the individual Control current supplied to the contacts is not significantly affected by the transverse resistance of the metallization.

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In FIG. 1, the control contacts 7 covered by the metallization 9 are shown in FIG. 1 for reasons of clarity Highlighted top view.

In the embodiment of Figure 3 extends Insulating layer 8 over the non-contacted part of the emitter 5 up to an adjacent area of the cathode contact 10, the metallization 9 overlapping the cathode contact 10. This embodiment is then expedient choose if a significant reduction in the size of the cathode contact and thus the current-carrying area can be avoided should, but at the same time a sufficiently wide metallization with regard to a small transverse resistance is required is. In many cases it is advantageous to cover the metallization 9 with a further insulating layer 11 in order to avoid short circuits to avoid with the main electrode, not shown, at the cathode contact.

The invention can also be used advantageously in a control system with a pn junction and an amplifying control system.

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Claims (12)

- 6 - FBE 72/27 patent claims: 1.J thyristor with at least four zones alternately opposite Leitiing type and at least one control surface provided with a contact, characterized in that, that with an extensive control surface, the ratio of circumference to area is selected as large as possible. 2. Thyristor according to claim 1, characterized in that the extensive control surface in a plurality of spatial separate control surfaces (6) is divided. 3 · Thyristor according to Claim 2, characterized in that the control surfaces (6) are arranged in the form of a strip or network are. 4 ·. Thyristor according to Claim 2, characterized in that the control surfaces (6) are arranged in a star shape. 5. Thyristor according to claim 2, characterized in that the control surfaces (6) are arranged in a ring. 6. Thyristor according to claims 2 to 5 »characterized in that the contacted control surfaces (6) electrically are conductively connected to each other. 7. Thyristor according to Claims 2 to 6, characterized in that the contact (7) is smaller than the control surface (6) is. 8. Thyristor according to claim 7, characterized in that the non-contacted part of the control surface (6) with a Insulating layer (8) is provided, and that at least a part of the insulating layer (8) has a Contact (7) covering metallization (9) connects. 509812/0421 - 7 - FBE 72/27 9. Thyristor according to claim 8, characterized in that the insulating layer (8) over the control surface (6) extends out to part of the emitter (5) of the thyristor. 10. Thyristor according to claim 8, characterized in that the insulating layer (8) is also on part of the cathode contact (10) extends. 11. Thyristor according to claim 10, characterized in that the cathode contact (10) and the metallization (9) overlap. 12. Thyristor according to Claims 8 to 11, characterized in that that the insulating layers (8) of the individual control surfaces (6) adjoin each other and up to the Contacts (7) form a closed path given by the geometric arrangement of the control surfaces (6), and that the metallization (9) on this track electrically connects the individual contacts (7) to one another. 509812/0421 L e r? e i t e