Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – Combined with field effect transistor
Patent
1995-06-08
1998-01-20
Brown, Peter Toby
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
Combined with field effect transistor
257141, 257146, 257152, 257161, 257162, H01L 2972, H01L 2910
Patent
active
057104441
DESCRIPTION:
BRIEF SUMMARY
This application was filed under 35 U.S.C. .sctn.371 from PCT/EP93/03688, filed Dec. 24, 1993.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a field-effect-controlled semiconductor component having at least four regions of alternating opposite conductivity type, including an anode-end emitter region, adjoining first and second base region and a cathode-end emitter regions, with the last-mentioned emitter region and the first base region forming the source and drain of an MOS field-effect transistor, and having an anode contact, a contact at the cathode-end emitter region and a control electrode contact for the MOS field-effect transistor.
2. Background Information
Such a component is known as an insulated gate bipolar transistor (IGBT or IGT). It was described in the European Patent Application EP-B1 80 044 and in the central application DE-A1 34 35 612. The essentials of this prior art reference are illustrated in FIG. 1. For FIG. 1, a lateral embodiment on an SOI substrate (SOI=silicon on insulator layer) was selected comprising a carrier substrate 5, a buried insulator 15 and a silicon layer 21. The IGBT comprises an anode-end emitter region 10, two adjoining base regions 20 and 32, 34 and a cathode-end emitter region 40. On an insulating layer 50, which covers a portion of the cathode-end base region 34, there is disposed a control contact 60 called a gate which forms a field-effect transistor together with the cathode-end emitter 40 and the anode-end base region 20. The component is provided with two power supply connections, a cathode 72 and an anode 76.
If the IGBT is polarized in forward direction and if the gate connection 60 of the field-effect transistor is actuated with positive potential vis-a-vis cathode 72, a conductive channel 42 is formed in the cathode-end base region 34, with this channel connecting the cathode-end emitter region 40 with the anode-end base region, i.e., the first base region 20. The electron current thus caused acts as gate current for the anode-end p-n-p transistor 10, 20, 34.
The resistance of channel 42, which is controllable by the gate, determines the level of the gate current, the injection of the minority charge carrier (holes) from the anode-end emitter 10, and therewith the on-state voltage of the component. For switch-off, the gate potential is equated with the cathode-potential so that the conductive channel 42 of the field-effect transistor disappears and the load current is switched off.
In the prior art solutions, different short-circuit structures are used for the emitter connections 72 and 76 to improve the switching properties of the component. For example, anode-end short circuits have been proposed (EP-B1 80 044) to increase the switching speed. Cathode-end short circuits (DE-A1 34 35 612) are necessary for carrying off the hole current of the p-n-p transistor to the cathode contact at a low resistance.
To this end, DE-A1 42 28 832 proposed to subdivide the hitherto undivided cathode-end base region (see FIG. 1) into two partial regions 32 and 34. The partial region 34 is moderately doped and, together with the thickness of the insulating layer 50, determines the threshold voltage of the field-effect transistor 40, 42, 20. The partial region 32 is highly doped in order to keep the layer resistance of the cathode-end base region low. This ensures that the p-n junction between the cathode-end emitter 40 and the cathode-end base region 34 is not biased so heavily in the forward direction that the emitter 40 injects electrons into the base region 34. Such an electron injection, however, would result in serious drawbacks. A locking-in of the existing parasitic thyristor structure 40, 34, 20, 10 in a switched-through state would entail a loss of the effect of the gate control.
Even if the above-described short circuit of the cathode-end emitter is used, the hole current in the p-conducting base region 34 can still effect a sufficiently large voltage drop which suffices to cause an electron injection from the emitter 40 to
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Korec Jacek
Neubrand Horst
Silber Dieter
Brown Peter Toby
Daimler-Benz Aktiengesellschaft
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