North Carolina State University

Mallikarjunaswamy S Shekar

Bantval J Baliga

Jacek Korec

B Jayant Baliga

Mahalingam Nandakumar

A semiconductor switching device includes a plurality of adjacent and parallel-connected switching cells in a semiconductor substrate. Each cell includes a thyristor having a floating emitter region and a trench-gate field effect transistor (TFET) for providing turn-on and turn-off control of the thyristor. In one embodiment of the switching device, parasitic thyristor latch-up is suppressed by using a dual-channel TFET which forms both inversion-layer and accumulation-layer channel connections in series between respective floating emitter regions and the cathode contact. In another embodiment, parasitic thyristor latch-up is prevented by joining floating emitter regions of a pair of adjacent cells to thereby eliminate a parasitic P-N-P-N path between the anode and cathode contacts. According to this second embodiment, a dual-channel TFET is preferably used to form a separate first conductivity type inversion-layer channel adjacent a first sidewall of the trench and a second conductivity type inversion-layer channel adjacent a second opposing sidewall of the trench. These channels provide the necessary electrical connections for both gated turn-on and turn-off control.

Dual-channel emitter switched thyristor with trench gate

An emitter switched thyristor structure providing on-state current saturation capability is disclosed herein. The thyristor structure includes anode and cathode electrodes, and a remote electrode connected to the cathode electrode. A multi-layer body of semiconductor material has a first surface and includes regenerative and non-regenerative portions each operatively coupled between the anode and cathode electrodes. The regenerative portion includes adjacent first, second, third and fourth regions of alternating conductivity type arranged respectively in series, wherein the remote electrode is in electrical contact with the second region and the anode electrode is in electrical contact with the fourth region. The emitter-switched thyristor is turned on by applying an enabling voltage to an insulated gate electrode disposed adjacent the first surface such that a conductive channel is created in the non-regenerative portion via modulation of the conductivity therein. The device may be operated in a saturation mode by reducing the applied gate voltage such that the conductive channel in the non-regenerative portion becomes pinched off. Termination of regenerative operation is initiated by applying a non-enabling voltage to the gate electrode so as to extinguish channel conductivity within the non-regenerative portion as well as within the third region of the regenerative portion. The remote electrode collects any charges remaining in the second region of the regenerative portion subsequent to application of the non-enabling voltage and thereby expedites turn-off of the thyristor device.

MOS gated thyristor having on-state current saturation capability

An emitter-switched thyristor structure includes a remote turn-off electrode for reducing turn-off time and increasing maximum controllable operating current. The switched thyristor structure further includes anode and cathode electrodes, with the remote electrode being connected to the cathode electrode. A multi-layer body of semiconductor material has a first surface, as well as regenerative and non-regenerative portions each operatively coupled between the anode and cathode electrodes. The regenerative portion includes adjacent first, second, third and fourth regions of alternating conductivity type arranged respectively in series. Electrical contacts exist between the remote electrode and the second region, as well as between the anode electrode and the fourth region. The thyristor is turned on by applying an enabling voltage to an insulated gate electrode disposed adjacent the first surface such that a conductive channel is created in the regenerative portion via modulation of the conductivity therein. Similarly, the termination of regenerative operation is initiated by applying a non-enabling voltage to the gate electrode. The remote electrode collects any charges remaining in the second region of the regenerative portion subsequent to application of the non-enabling voltage and thereby expedites turn off of the emitter-switched thyristor.

MOS gated thyristor with remote turn-off electrode

An emitter switched thyristor with base resistance control for preventing parasitic latch-up includes a P-N-P-N main thyristor with an N.sup.+ floating emitter for MOS-gated controlled turn-on and a lateral P-channel MOSFET for shunting hole current in a second base region to a P.sup.+ diverting region electrically connected to the cathode. The P-channel MOSFET is enabled by the application of a negative gate voltage to form a P-type inversion layer between the second base region and the P.sup.+ diverter region, thus reducing the resistance between the cathode and the second base region and raising the holding current of the emitter switched thyristor to above the operating current level. The formation of an alternative current path to the cathode has the further effect of reducing the forward bias across the base-emitter junction of an adjacent parasitic thyristor to thereby prevent the sustained regenerative action of the parasitic thyristor.

Unit cell arrangement for emitter switched thyristor with base

An emitter switched thyristor without parasitic thyristor latch-up susceptibility includes a thyristor having an anode region, a first base region, a second base region in the first base region and an emitter region of first conductivity type in the second base region. An electrical connection is provided between the emitter region and the cathode contact by a field effect transistor in the first base region. The transistor is positioned adjacent the second base region and includes a source electrically connected to the emitter region by a metal strap on the surface of the substrate. The drain of the transistor is electrically connected to the cathode contact and has a conductivity type opposite the conductivity type of the first base region. Accordingly, the cathode contact and anode contact are not separated by a four layer parasitic thyristor. Parasitic latch-up operation is thereby eliminated.

Growing community of inventors

Raleigh, NC, United States of America

Mallikarjunaswamy S Shekar