Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – With extended latchup current level
Patent
1997-04-08
1999-07-20
Fahmy, Wael
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
With extended latchup current level
257153, 257162, 257163, H01L 2974, H01L 31111
Patent
active
059259000
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a semiconductor device.
BACKGROUND OF THE INVENTION
In power integrated circuits, many devices having a high breakdown voltage are known. For applications such as integrated power supplies, small motor control, and electronic lamp ballasts, where high voltage and high current are required, the current carrying capability of the device is also important. The on-state specific resistance of the power device therefore needs to be low to reduce power loss. This is very important in an IC environment where minimum area and power dissipation are essential.
One known device is the emitter switched thyristor and particularly the lateral emitter switched thyristor (LEST). Reference is made to the paper by B J Baliga and Y S Huang, entitled "Lateral Junction-isolated Emitter Switched Thyristor," IEEE Electron Device Letters vol. 13, p. 615, 1992. The thyristor current for this device can be controlled by using a MOS gate. An example of a conventional LEST structure is shown in FIG. 1. In the conventional LEST device of FIG. 1, triggering of the main thyristor is difficult. A very long n+ floating emitter is necessary to ensure that the device operates in thyristor conduction mode, which leads to excessive area consumption by the device.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a lateral emitter-switched thyristor, the thyristor comprising:
a first electrode region of a first conduction type formed in the surface of a drift region of a second conduction type;
a base region of a first conduction type formed in the drift region;
an emitter region of the second conduction type formed in the surface of the base region;
a second electrode region consisting of adjacent regions of the first and second conduction types with the second electrode region of the second conduction type being separated from the emitter region by a portion of the base region;
adjacent regions of the first and second conduction types formed in the surface of the base region between the first electrode region and the emitter region, the region of the first conduction type being on the side next to the emitter region;
a floating ohmic contact connecting said adjacent regions of the first and second conduction types formed in the surface of the base region;
a first gate at the surface of the device, the first gate commencing at the region of the second conductivity type under the floating ohmic contact and extending over the junction between the drift region and the base region; and,
a second gate extending over said portion of the base region between the emitter region and the second electrode region of the second conduction type.
The floating ohmic contact may be immediately adjacent the emitter region or may be spaced from the emitter region.
According to a second aspect of the present invention, there is provided a lateral emitter-switched thyristor, the thyristor comprising:
a first electrode region of a first conduction type formed in the surface of a drift region of a second conduction type;
a base region of a first conduction type formed in the drift region;
a second electrode region of the first conduction type formed in the surface of the drift region;
adjacent regions of the first and second conduction types formed in the surface of the base region between the first electrode region and the second electrode region, the region of the first conduction type being on the side next to the second electrode region;
a floating ohmic contact connecting said adjacent regions of the first and second conduction types formed in the surface of the base region;
a first gate at the surface of the device, the first gate commencing at the region of the second conductivity type under the floating ohmic contact and extending over the junction between the drift region and the base region; and,
a second gate at the surface of the device and between the second electrode region and the region of the first conduction type under the floating ohmic co
REFERENCES:
patent: 5293054 (1994-03-01), Shekar et al.
patent: 5294816 (1994-03-01), Shekar et al.
patent: 5349212 (1994-09-01), Seki
"A CMOS Compatible Lateral Emitter Switched Thyristor with Enhanced Turn-on Capability"; Nov. 1994; IEEE, Electron Device Letters vol. 15, No. 11; Chen et al.
"Lateral Junction-Isolated Emitter Switched Thyristor" by Baliga et al. (IEEE Electron Device Letters, vol. 13, No. 12, Dec. 1992, pp. 615-617.
"The MOS-Gated Emitter Switched Thyristor" by B. J. Baliga (Proceedings of 1990 International Symposium on Power Semiconductor Devices & IC's, Tokyo, pp. 117-121).
Amaratunga Gehan Anil Joseph
Chen Wei
Kumagai Naoki
Fahmy Wael
Fuji Electric & Co., Ltd.
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