DE2462500A1 - Four zone thyristor with at least one gate - has intermediate weakly doped zone between base zone and outer emitter zone - Google Patents

Abstract

Thyristor with at least four zones of alternate opposite conductivity type, and at least one gate (control electrode) is proposed. The thyristor is designed to provide reliable and faultless switching without detriment to its other properties. To this end, between the base (control) zone and the adjacent outer emitter zone an intermediate weakly doped zone is provided and is of the same conductivity type as the base (control) zone. Lands are provided for short-circuiting the intermediate zone and the emitter zone. These lands are specifically designed in planar configuration.

Description

"Thyristor"

The invention relates to a thyristor with at least four alternating zones opposite conduction type and at least one control electrode.

A thyristor with four zones of alternately opposite conduction types has two outer, metallically contacted zones, which act as emitter zones of the thyristor are designated. The two middle zones are called the base zones, one of these two zones is provided with a control contact and therefore the represents the so-called tax base zone.

A thyristor is usually operated by a control contact supplied ignition current pulse transferred into the conductive state. Switching off usually takes place by what is known as commutation, whereby the charge carriers pass through a load current flowing in the opposite direction from those with charge carriers flooded areas of the semiconductor body are sucked off. This is the PN junction loaded between the control base zone and the adjacent emitter zone in the reverse direction and can briefly break through, which hinders the shutdown process will. The switch-off behavior can be improved by emitter short circuits, whereby then the load carriers predominantly vacuumed over these areas will. In this case, the shutdown process will be particularly effective if the PN junction formed between the outer emitter zone and the control base zone does not break through.

On the other hand, too strong a lateral current should be in the control base be avoided, as this current leads to a lateral voltage drop that the risk of the barrier layer in question breaking through increases. To avoid of the lateral voltage drop, the emitter short-circuit points are chosen more densely, which in turn is unfavorable for other reasons, such as a hindrance to the ignition propagation.

The invention is therefore based on the object of making a thyristor available to make, which enables a perfect and safe shutdown without others Properties are deteriorated.

This object is achieved according to the invention in that between an intermediate region is provided between the control base region and the adjacent outer emitter region which is lightly doped and of the same conductivity type as the control base region having, and that locations are provided at which the intermediate zone and the emitter zone are short-circuited.

An advantageous development of the invention is that in Area of the short-circuits the carrier service life in the two base zones by additional Recombination centers is reduced.

The increase in the reverse voltage between the emitter zone and the control base zone is explained in a known way by the more favorable blocking properties of a P-S-N structure compared to a P§ transition with relatively high doping.

The thickness and doping of the weakly doped intermediate zone is appropriate chosen so that for the emitter, Intermediate zone and tax base P-S-N structure formed sets a reverse voltage above 20 V. Simultaneously there is also an improvement in the immunity to interference, i.e. a security against the triggering of the thyristor over the voltage rise rate by the weak Doping of the intermediate zone and its width are chosen so that the current gain factor of the sub-transistor, which consists of the control base zone and the two adjacent zones opposite formation type is formed, only increases at higher currents than with conventional construction.

The essence of the invention will be explained in more detail with reference to the figure.

The thyristor 1 consists of the two emitter zones 2, 3 and the two Base zones 4, 5. The emitter zones 2 and 3 each have metallic contacts 7 or 8 provided.

There is one between the emitter zone 3 and the base zone 5 Intermediate zone 9, which is lightly doped and the same conductivity type as the control base zone having. The intermediate zone 9 is provided with the control contact 6. As a result of the weak With doping, zones 3, 5 and 9 form a P-S-N structure with a relatively high breakdown voltage. As a result of the high breakdown voltage between the emitter zone and the base zone existing PN junction is avoided that due to the switching off by Lateral voltage drop occurring at any commutation at this junction Body goes into the breakthrough. The short circuits are between the emitter zone 3 and the intermediate zone 5 at the points with the reference number 10. As already mentioned, areas 11 below the short-circuit points 10 can advantageously be provided, in which the two base zones 4 and 5 have an increased recombination center density exhibit.

Since the only weakly doped zone when loaded in the forward direction 9 is flooded by load carriers and since the Carrier life in weakly doped zones with high injection is relatively large compared to the carrier lifetime in the more highly doped areas must also be used in the thyristor according to the invention no impairment of the passage behavior can be accepted.

A method of making a thyristor according to the invention is that the control base zone is generated by diffusion of impurities and their thickness, if necessary by removing material to the desired dimensioning the inrush current is set. Subsequently, the tax base zone the high-resistance intermediate zone is deposited epitaxially and in this intermediate layer the actual emitter zone introduced by diffusion or alloy. The epitaxial deposited layer contains zones 3 and 9 in the finished thyristor by Zone 3 is selectively introduced into this layer, the intermediate zone automatically 9 is created. The thyristor is manufactured with regard to the other parameters in a known way.

L e r s e i t e

Claims (6)

Claims 1. Thyristor with at least four zones alternately opposite conduction type and at least one control electrode, characterized in that, that between the control base zone (5) and the adjacent outer emitter zone (3) an intermediate zone (9) is provided, which is lightly doped and the same conductivity type as the control base zone (5), and that locations (10) are provided at which the intermediate zone (9) and the emitter zone (3) are short-circuited. 2. Thyristor according to claim 1, characterized in that the short-circuit points (10) are planar. 3. Thyristor according to claim 1 or 2, characterized in that im Area (11) below the short-circuit points (10) the concentration of the recombination centers is increased in the base zones (4, 5). 4. Thyristor according to one of claims 1 to 3, characterized in that that the breakdown voltage of the emitter zone (3), intermediate zone (9) and control base zone (5) formed P-S-N structure is above 20 V. 5. Thyristor according to one of claims 1 to 4, characterized in that that the control electrode (6) contacts the intermediate zone (9) directly. 6. A method for manufacturing a thyristor according to any one of the claims 1 to 5, characterized in that the control base zone (5) by diffusion generated by imperfections and adjusted their thickness, if necessary, by removing material is that on the control base zone (5), the intermediate zone (9) is deposited epitaxially and then the emitter zone (3) is formed by diffusion or alloying.