Westinghouse Electric Corporation

Chang K Chu

John Bartko

Patrick E Felice

Krishan S Tarneja

George W Vomish

Earl S Schlegel

Surinder Krishna

Philip L Hower

The present invention is directed to a diffusion source for establishing a p-type conductivity region in a semiconductor device and to a method for preparing such diffusion source. The diffusion source consists of pure silicon powder diffused with a p-type impurity.

Diffusion source and method of preparing

A method of reducing the reverse recovery charge of thyristors without substantially increasing forward voltage drop by first determining the depth of the anode PN junction from a major surface adjoining a cathode emitter region. The depth of maximum defect generation in thyristor on irradiation through the major surface with a given radiation source radiating particles with molecular weight greater than one, preferably proton or alpha particles, and adjusting the energy level at the major surface of the thyristor from the radiation source to provide the depth of maximum defect generation adjacent the anode PN junction and preferably in the anode base region within 20 micrometers of the anode PN junction or in the anode emitter region within 15 micrometers of the anode PN junction. Thereafter the thyristor is irradiated through said major surface with the adjusted energy level from the radiation source to a given dosage to reduce the reverse recovery stored charge of the thyristor without substantially increasing the forward voltage drop.

Reducing the reverse recovery charge of thyristors by nuclear irradiation

The switching time of certain semiconductor devices is decreased while maintaining other electrical characteristics of the devices by irradiating them with a neutron radiation source of greater than 1.0 Mev. to a dosage between 1.times.10.sup.11 and 1.times.10.sup.15 neutrons per square centimeter. The irradiation is preferably to a dosage between 1.times.10.sup.1 and 1.times.10.sup.14 neutrons per square centimeter and preferably has substantial energy greater than 14 Mev. The devices are also annealed during and/or subsequent to the irradiation at a temperature higher than the highest specified temperature and preferably at least 50.degree. C. higher than the highest specified temperature.

Reducing the switching time of semiconductor devices by neutron

A reverse switching rectifier is described in which a PNPN semiconductor structure has a specially adapted N-type end zone or cathode-emitter zone. The N-type end zone penetrates to two different levels in the semiconductor body. A deep central portion and a shallow peripheral portion of the N-type end zone are produced by etching a cavity in the center of the body followed by diffusion of N-type dopant material. The exposed surfaces of the N-type end zone are then metallized to provide electrical and thermal contact thereto.

Reverse switching rectifier and method for making same

The turn-off time of a reverse blocking diode thyristor is decreased without significantly effecting other electrical characteristics by irradiating with a radiation source to a dosage corresponding to between about 4 .times. 10.sup.13 and about 2 .times. 10.sup.14 electrons/cm.sup.2 and preferably to between about 6 .times. 10.sup.13 and about 2 .times. 10.sup.14 electrons/cm.sup.2 with 2 MeV electron radiation source. Preferably the radiation source is electron radiation with an energy greater than 1 MeV.

Irradiation for rapid turn-off reverse blocking diode thyristor

A transistor device is described in which an NPN semiconductor structure has a specially adapted N-type emitter zone and associated electrode. The emitter zone is produced by etching a cavity in one major surface of the semiconductor body followed by diffusion of N-type dopant material. Emitter, base and collector electrodes are then affixed to the appropriate surfaces of the body to provide electrical and thermal contact thereto.

High voltage transistor with high gain

A plasma thyristor circuit is provided for generating high power, ultra-short duration electrical signals. A silicon semiconductor body has first, second and third impurity regions therein with a PN junction formed at the transition between the first and second or the second and third impurity regions. The second impurity region has an impurity concentration of less than about 5 .times. 10.sup.14 atoms/cm.sup.3, and a width of greater than about 80 microns. The ratio of the punch-through voltage of the second impurity region to the reverse breakdown voltage of the PN junction is between 0.3 and 0.7. Power sources apply both a reverse bias voltage across the body greater than said punch-through voltage and less than said reverse breakdown voltage, and a current to the body having a density greater than the saturation current density of the second impurity region.

Growing community of inventors

Pittsburgh, PA, United States of America

Chang K Chu