Bbc Brown, Boveri & Company, Limited

Roland Sittig

Peter Roggwiller

Jens Gobrecht

Jan Voboril

Patrick DeBruyne

Jozef Cornu

Patrick De Bruyne

Christian Ruetsch

A process for manufacturing a power semiconductor component having a component of this type is presented which has at least three consecutive layers and possessing a high current capacity and small power losses. For contacting the first two layers, the component has first second metallized contact planes, which impress a step-like structure onto a first surface of the component. The steps have a height of between 10 and 20 .mu.m and a width of between 20 and 300 .mu.m. The ratio between the surface area of the first contact plane and the surface area of the second contact plane is between 1 and 4. The first layer is heavily doped and has a maximum thickness of 8 .mu.m, and the second layer is lightly doped and has a maximum thickness of 40 .mu.m. According to the process for manufacturing the component, the surface structure according to the invention is produced essentially by a reactive ion-etching process with a single aluminum mask.

Process for manufacturing a power semiconductor component

For improving the dynamic characteristics of semiconductor components required to absorb high reverse voltages only in one polarity (diodes, reverse-conducting thyristors and asymmetric thyristors), in many cases structures having an n base consisting of two layers are used. In order to improve the reverse-voltage capability, it is proposed, in a semiconductor component having at least one pn.sup.- n sequence of layers, to select the thickness (S) and the doping of an n stop layer (4) in such a way that the following applies: ##EQU1## where e=elementary charge, .epsilon.=dielectric constant of the semiconductor, N.sub.D =donor concentration, X=path coordinate, 0.8.ltoreq.k.ltoreq.1.0 and E.sub.n =field strength at the n.sup.- n junction. The effect of this measure is that the geometric conditions of the edge chamfering are less stringent. The edge can also be shaped by means of conventional etching processes.

Semiconductor device having a blocking capability in only one direction

A power semiconductor component having a component of this type is presented which has at least three consecutive layers and possessing a high current capacity and small power losses. For contacting the first two layers, the component has first and second metallized contact planes, which impress a step-like structure onto a first surface of the component. The steps have a height of between 10 and 20 .mu.m and a width of between 20 and 300 .mu.m. The ratio between the surface area of the first contact plane and the surface area of the second contact plane is between 1 and 4. The first layer is heavily doped and has a maximum thickness of 8 .mu.m, and the second layer is lightly doped and has a maximum thickness of 40 .mu.m. The invention further includes a process for manufacturing the component, wherein the surface structure according to the invention is produced essentially by a reactive ion-etching process with a single aluminum mask.

Power semiconductor component and process for its manufacture

A semiconductor component such as a four layer assymetrical thyristor having four zones of alternately opposite conductivity type, including a P emitter, an N base, a P base and an N emitter, wherein in the N base zone there is provided a stopping layer in a partial region adjacent the P emitter. The stopping layer has a doping concentration which decreases in a direction towards the P emitter zone perpendicular to the four zones. Thus the transport factor for the holes injected by the P emitter is desirably changed by means of lowering the doping concentration of the stopping layer in front of the P emitter, on the side of the anode, of a highly blocking thyristor in the forward direction, while the full effectiveness of the stopping layer remains unchanged. Also a lower blocking current in the blocking condition and/or a lower transmission voltage in the passing condition is attained.

Asymmetrical thyristor with highly doped anode base layer region for

A process for interrupting load current in a thyristor to switch-off current conduction through the thyristor, as well as a semiconductor module for implementation of the process. In the process, a semiconductor diode is connected in parallel to the thyristor and a photocurrent is produced in the diode to switch-off current conduction in the thyristor, the diode then taking over the load current of the thyristor. The photocurrent can be optionally produced by means of an electro-magnetic radiation (light) or by means of a bombardment with electrons. The process permits considerable reduction in the complexity of the cut-off circuit and separation of this circuit in a galvanic fashion from the load circuit. The semiconductor module provided for implementing the process includes a thyristor and a radiation sensitive diode disposed in parallel with the thyristor and commonly integrated into the thyristor semiconductor structure.

Process for the cutting-off of a thyristor

A semiconductor element having at least one pn junction and provided with zone guard rings for improving the suppression behavior of the pn junction, wherein the pn junction extends to the peripheral or side surface of the element and the first of a series of guard rings is coordinated with the pn junction and is bounded by the peripheral or side surface and by the lower planar surface of the element.

Semiconductor element with zone guard rings

A power thyristor formed by four zones of alternating conductivity type and including at least one control gate, at least one generator gate in the vicinity of a respective control gate and at least one firing gate located further away from a respective control gate formed on portions of the cathode-base zone extending to the cathode-side main surface, in which the firing gate is electronically connected to the generator gate with no intervening cathode-base zone. The control gate, generator gate, firing gate, cathode zone and cathode base zone are dimensioned so that the ratio between the lateral path resistance of the cathode base zone between the generator gate and cathode zone, and the corresponding resistance between the firing gate and the cathode zone, and the ratio between the edge-length of the generator gate and the edge-length of the firing gate are such that a current furnished by the generator gate suffices to fire the thyristor in the region beneath the firing gate, even at low anode voltages and small firing currents.

Power thyristor and method of fabrication therefore utilizing control,

An output thyristor with at least two electrodes located on the cathode side base zone, whereby one of the two electrodes is used as a control electrode (starting gate) and the second electrode is used for the output of current (generator gate), wherein the existing lateral resistance R.sub.GK ' between the generator gate and the cathode zone and/or the edge length of the generator gate is selected such that at the generator gate of the started thyristor, with an anode current which is smaller than the surge limit of the thyristor in question, the current I.sub.G removable therefrom is sufficient when applied to the starting gate of a corresponding thyristor connected in parallel to start the parallel connected thyristor. The lateral resistance between the starting gate and the cathode zone--R.sub.GK --is selected as small as possible (R.sub.GK &lt;R.sub.GK ') so that the starting voltage on the starting gate can act directly on the semiconductor junction between the thyristor cathode zone and the cathode base zone.

Thyristor with starting and generating cathode base contacts for use in

A thyristor exhibiting improved maximum current rise rates as a result of the relocation of the ignition front from the edge of the cathode emitter zone to inner cathode emitter areas. This relocation is effected by providing a relatively light doping of the anode zone beneath the thyristor gate and cathode emitter edge, and a relatively higher anode zone doping opposite and outside of the cathode edge, while not applying an anode electrode metal coating to the lightly doped area of the anode zone. The thyristor utilizes cathode emitter short circuit rings arranged such that the ignition front which occurs at thyristor triggering bypasses the short circuit ring immediately adjacent the cathode emitter edge, thereby increasing the thyristor voltage rise velocity, dU/dt.

Thyristor having an anode transverse field emitter

A safety device for protecting a controllable high power semiconductor component having an anode, a cathode, and a control electrode, against excessive voltage rise rates dU/dt and comprising: a semiconductor body having at least four sequential zones of alternating and opposite conductivity type, the second sequential zone being provided with a high concentration region having a higher concentration of conductivity type determining impurities than the rest of the second sequential zone; a first emitter electrode contacting the first of the four sequential zones of the semiconductor body and adapted to be connected to the control electrode of the controllable high power semiconductor component; a second emitter electrode contacting the fourth of the four sequential zones of the semiconductor body and adapted to be connected to the anode of the controllable high power semiconductor component; a gate electrode contacting the high concentration region of the second sequential zone of the semiconductor body; and an ohmic conductor connected between the first emitter electrode and the gate electrode.

Safety device for protecting semiconductor components against excessive

A high frequency, high voltage thyristor and an associated circuit arrangement and method of operating the circuit are disclosed. The thyristor, which is capable of switching frequencies above 10 kHz and forward blocking voltages in excess of 500 V. includes an inter-digitated emitter-gate structure, a control zone in contact with the gate and a base zone that is less doped than the control zone. The base zone of the thyristor includes first and second layers of different doping concentrations. The circuit arrangement includes thyristors of the type described arranged in pairs and shunted by antiparallel diodes. According to the method of the invention, the thyristor is not fired by applying potential to the gate, but by holding the thyristor in a forward blocking state and then opening the gate circuit or reversing the gate voltage.

Electrical circuit with a high-frequency thyristor fired by blocking

A thyristor, with at least four zones of alternating opposite conductivity types, in which the first and fourth zones are contacted by the main electrodes and act as emitter zones, the second zone adjoins the first zone, and the third zone of lowest doping lies between the second and fourth zones. Both the second and the third zones together with the forward blocking PN-junction formed between them extend to the surface of the thyristor semiconductor chip on the side with the first zone. The portion of the forward blocking PN-junction reaching the surface can be irradiated with light so as to trigger the thyristor. There is provided in the surface a highly doped zone of the conductivity type of the first zone, which is connected with the second zone by an electrical contact on the surface. The part of the third zone extending to the surface encloses part of the second zone and the highly doped zone. The electrical contact connects the highly doped zone with the part of the second zone lying outside the region of the second zone enclosed by the third zone at the surface.

Light-controlled thyristor with anode-base surface firing

A bistable semiconductor component for high frequencies with a semiconductor chip includes a sequence of at least four zones of alternating opposed types of conductivity. The outer zones form the emitter zones and are more heavily doped than the two inner zones. The base zones are so doped that with a voltage V.sub.R smaller than or at most equal to the maximum inverse voltage V.sub.RS applied in the reverse direction across the two emitter zones, the shortest distance W between the two blocking layers formed at the two outer junctions is less than the diffusion length L.sub.B of the charge carriers in the base zones.

Bistable semiconductor component for high frequencies having four zones

An improved light activated thyristor and a method of fabricating the thyristor are disclosed. The thyristor includes a space charge zone extenable to one end surface of the thyristor body whereby the thyristor may be triggered efficiently with low power light beams. In one embodiment of the device, a notch is formed in an end surface of the thyristor body extending into the space charge region of the forward blocking pn-junction. In another embodiment of the device, a portion of the anodic base region of the thyristor is led up through the cathodic base region to the end surface of the thyristor, whereby the forward blocking junction extends to the end surface of the device.

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Umiken, Switzerland

Roland Sittig