Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – Combined with field effect transistor
Patent
1999-03-22
2000-09-12
Ngo, Ngan V.
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
Combined with field effect transistor
257137, 257146, H01L 2974
Patent
active
061181412
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an emitter-switched thyristor, having a main thyristor, which is formed from a p+ anode emitter, a drift zone having an opposing conduction type, a zone which, in the turned-off state of the thyristor, has a blocking zone with respect to the drift zone, and a cathode-side emitter having, again, a reversed conduction type resulting in a zone sequence p+n-pn+; a transistor structure, which is parallel to the main thyristor and comprises three regions of alternating conductivity types: an emitter, which is identical to the p+ anode emitter, an n-doped zone as a base, and a collector region; and, an NMOSFET for direct actuation of the cathode emitter, with the source of this transistor, like the collector region, being contacted by a cathode, which is connected to a cathode connector.
An advantage of emitter-switched thyristors is that they can easily be controlled via a gate having a low voltage drop. Most ESTs (Emitter-Switched Thyristors) have no pronounced current saturation, because the saturation is limited by the breakdown voltage of the turn-on MOSFET, which is switched in series with the main thyristor. The ESTs having a twin channel have the disadvantage of a high voltage drop in the forward direction. A MOSFET of this type is described in the publication of M. S. Shekar, B. J. Baliga, M. Nandakumar, S. Tandon and A. Reisman: "High-Voltage Current Saturation in Emitter Switched Thyristors," IEEE ELECTRON DEVICE LETTERS, VOL. 12, NO. 7, JULY 1991.
The publication of A. Bhalla, T. P. Chow, K. C. So: "RECEST: A Reverse Channel Emitter Switched Thyristor," ISPSD-95, Proc. Int. Symp. on Power Semic. Dev. and ICS, 1995, Yokohama, pp. 24-28, discloses an emitter-switched thyristor that forms a main thyristor between a "floating" n+ emitter, a p trough, an n drift region, an n buffer zone and a p+ substrate. The floating n+ emitter is short-circuited to the n+ drain region of the lateral, series-connected MOSFET by a floating metal connection. The thyristor current is thereby forced to flow through the series MOSFET. A parasitic thyristor is present between the n+ source, the p trough, the n drift region, the n buffer zone and the p+ substrate. Both parts of the gate are connected to the boundary of the cell, which forms an approximately 100- m-long strip in the z direction. The p trough under the floating n+ emitter is short-circuited in the z direction to the p+ region and the cathode at the boundary of the cell of the individual component (see FIG. 1).
Turn-on is effected by the application of a positive voltage to the gate and a positive bias voltage to the anode. The gate effects electron inversion layers under the lateral series MOSFET and the DMOS gate. The electrons flow from the cathode and into the drift region via the lateral series MOSFET, the floating metal connection, the floating n+ emitter and the DMOS channel. This in turn effects the injection of holes from the p+ substrate, a few of which are captured by the p trough. This hole current flows under the floating n+ emitter in the z direction, and polarizes the n+/p trough transition in the forward direction, and turns on the main thyristor. Because the lateral series MOSFET is regarded as the sole source of electrons for the floating n+ emitter (via the floating metal connection), the entire thyristor current must flow through the series MOSFET. This leads to a gate-switched current saturation in the turned-on state.
To turn off the component, a negative voltage is applied to the gate. The gate turns off the lateral series MOSFET and activates the p-channel MOSFET, which bypasses the hole current. This produces a path for the hole current from the p trough to the cathode contact. Because this hole current does not flow under the n+ source, the dynamic latching of the parasitic thyristor is suppressed. To the extent to which the anode voltage increases during turn-off, the potential of the JFET region will increase prior to the recovery of the transition between the p trough and the n drif
REFERENCES:
patent: 5498884 (1996-03-01), Ajit
patent: 5665988 (1997-09-01), Huang
patent: 5780917 (1998-07-01), Mori
Bhalla, Anup et al. "RECEST: A Reverse Channel Emitter Switched Thyristor", Proceedings of 1995 International Symposium on Power Semiconductor Devices & ICs, Yokohama, Japan, pp. 24-28.
Shekar, M.S. et al. "High-Voltage Current Saturation in Emitter Switched Thyristors", IEEE Electron Device Letters, vol. 12, No. 7, pp. 387-389, Jul. 1991.
Constapel Rainer
Korec Jacek
Xu Shuming
Kunitz Norman N.
Ngo Ngan V.
Spencer George
Vishay Semicondcutor GmbH
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