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United States Patent [191 [11] Patent Number: 4,937,646 Tihanyi et al. [45] Date of Patent: Jun. 26, 1990

[54] MOSFET WITH TEMPERATURE 4,142,115 2/ 1979 Nakata et a1...... 357/ 38 PROTECI‘IQN 4,323,793 4/1982 Schutten et al...... 307/310 [75] Inventors: Jenoe Tihanyi; Johann Bierlmaier, FOREIGN PATENT DOCUMENTS b°th °f Munich’ Fed- ReP- 0f 2245089 4/1975 France . Germany 52-109881 9/1977 Japan . [73] Assignee: Siemens Aktiengesellschaft, Berlin 23402658 11/1984 Japan ‘ 3 1 and Munich Fed- Rep. of Germany 448161 8/1935 Japan ...... 57/23. 3 ’ 2103877 2/1983 United Kingdom ...... 357/23.13 [21] APP“ N°" 191’719 OTHER PUBLICATIONS [22] Film May 2’ 1988 H. Wolf, “,” @1971, John Wiley & ‘ . _ Sons, Inc., p. 399. Related U.S. Application Data Pr‘ E _ J h E Cl J , _ lma xammer- ose . awson, r. [63] c(liontiinuation of Ser. No. 881,164, Jul. 2, 1986, aban- Artur"); Agent, or Firmijohn Francis Moran one . [30] Foreign Application Priority Data [57] ‘ ABSTRACT On the body of a MOSFET (1), the Jul. 9, 1985 [DE] Fed. Rep. of Germany ...... 3524517 semiconductor body of a (5) (or of a bipolar [51] Int. Cl.5 ...... H01L 29/74; HOlL 27/02 ) is located for thermal conduction purposes. [52] U.S. Cl...... 357/43; 357/28; The anode and cathode terminals (A, K) (emitter and 357/38; 307/310 collector terminal) are connected to the gate terminal [58] Field of Search ...... 357/43, 28, 38, 234; (G) and to the source terminal (S) of the MOSFET (1), 307/3 10 respectively. The thyristor (bipolar transistor) is rated so that it turns on before a temperature of 150° to 180° [56] References Cited is obtained which is critical for the MOSFET. Thus the U.S. PATENT DOCUMENTS gate-source capacitance of the MOSFET is effectively 3,872,418 3/1975 Plough et al...... 357/28 shortcircuited and the MOSFET turns off. 4,050,083 9/1977 Jaskolski et a1. .. 357/28 4,117,505 9/1978 Nakata ...... 357/28 7 Claims, 1 Drawing Sheet US. Patent Jun. 26, 1990 4,937,646 4,937,646 1 2 wherein are located in the planar surface an anode-side MOSFET WITH TEMPERATURE PROTECTION emitter zone 9 and a cathode-side base zone 7. In zone 7, a cathode-side emitter zone 8 is embedded into the BACKGROUND OF THE INVENTION planar surface. Zones 8 and 9 are respectively provided This invention relates to a semiconductor component with electrodes 10, 11 which serves as the cathode ter including a MOSFET, and it relates, more particularly, minal K and the anode terminal A, respectively. The to such a component having a semiconductor body with electrodes 10 and 11 are respective electrically con two main surfaces as well as a gate electrode and a nected to the source electrode S and to the gate elec source electrode. ‘ trode G. Semiconductor components only function well up to It is desirable for the thyristor to be electrically insu certain temperatures. If the junction temperatures ex lated from the semiconductor body 1 of the MOSFET. ceed values which range between 130° and 180° C. To accomplish this, a thin insulating layer 3 is used, depending on the design of the particular semiconduc which comprises silicon nitride material Si3N4. The tor component, they lose their blocking ability or ability thyristor may be secured on the insulating layer 3 by a to withstand reverse bias potentials in the off-state. The 5 thin adhesive layer 4. The layers 3 and 4 are relatively ?ow of current through the semiconductor component thin, for example 0.5 pm and 5 to 10 pm, respectively, may then become so great that the component is de as a result the thyristor is in good thermal contact with stroyed. High external or ambient temperatures may the MOSFET 1. to making the semiconductor component unable to When current ?ows through the MOSFET by appli assume and maintain its off-state even at current values cation of voltage between the source S electrodes and below its nominal current. These problems arise with all the drain electrode D, the semiconductor body 1 of the semiconductor components containing a pn junction, MOSFET generates heat and with it the thyristor 5 is which includes bipolar semiconductor components as elevated in temperature. In this situation, the gate well as IGFET structures. source voltage of the MOSFET constitutes the anode 25 cathode voltage for the thyristor. If the temperature in SUMMARY OF THE INVENTION the interior of the MOSFET rises due to an overload It is an object of the invention to provide such a condition or a high ambient temperature, the tempera MOSFET so that it is reliably protected against high ture of the lateral thyristor 5 also rises. Hence the off temperatures. state current of the thyristor rises until it ?res. This This problem is overcome by a ?ring forms a low-impedance current path between having the following features: anode A and cathode K, so that the voltage between (a) On one of the main surfaces of the semiconductor source terminal S and gate terminal G of the MOSFET body of the MOSFET, the semiconductor body of practically collapses. The forward voltage of the thy a semiconductor is fastened, which turns on ristor must, in the on-state, be lower than the threshold when a certain junction temperature is reached; 35 voltage UT of the MOSFET. The gate-source capaci (b) the two semiconductor bodies are connected to tance Cas of the MOSFET will then be discharged and gether thermally; the latter is blocked. (c) the semiconductor body of the semiconductor The temperature at which the thyristor ?res may, for switch has two main electrodes; predetermined dimensions and dopings, be adjusted, for (d) the main electrodes are connected to the gate 40 example, by a shunt 12 between the cathode-side emit electrode and to the source electrode, respectively. ter zone 8 and the cathode-side base zone 7. A typical 'BRIEF DESCRIPTION OF THE DRAWING thyristor may have, for example, the following doping values: Features of the invention and additional objects of the invention will be more readily appreciated and bet 45 ter understood by reference to the following detailed Zones 8, 9: 1019 to 1020 atoms As cm‘3 description which should be considered in conjunction Zone 7: 1017 to 1018 atoms B cm-3 with the drawing. Zone 6: 10M to 1016 atoms P cm3 FIG. 1 illustrates a sectional view-of one'illustrative embodiment of the invention. 50 If the semiconductor component is used in circuits FIG. 2, depicts another illustrative embodiment of with high dv/dt or voltage transition loads, it may the invention preferably for realization in an integrated occur that the thyristor will be ?red just due to these circuit arrangement for the semiconductor switch with conditions, without a temperature critical for the MOS improved properties as compared with the arrangement FET having been reached. This behavior of the thy according to FIG. 1 55 ristor due to the dv/dt condition can be improved in a conventional manner which entails enlarging an elec DETAILED DESCRIPTION trode to act as shunt 12. But this technique also pro In FIG. 1, the semiconductor component comprises a duces a reduction in the sensitivity of the thyristor to MOSFET, having a semiconductor body 1 illustrated in rising temperatures. It is advisable, therefore, to select rather simpli?ed form. One of the major surfaces of the 60 for the semiconductor switch an arrangement which is semiconductor body 1 is connected to a drain electrode illustrated in FIG. 2. It provides insensitivity to high D. On the other major surface, a source electrode S and dv/dt loads with a good temperature sensitivity. a gate electrode G are mounted. On this same main The thyristor 5 used in FIG. 1 is shown schematically surface which includes the source and gate electrodes, a in FIG. 2. Identical or equivalent components of FIG. 2 semiconductor switch is also mounted. The mounted 65 which correspond to those of FIG. 1 are marked with semiconductor switch is identi?ed with 5. In the sim the same reference numerals. To increase the dv/dt plest case this semiconductor switch may be, as shown, - stability, arranged in shunt between zones 7 and 8 is a a lateral thyristor. It consists of a central region 6, 14 which is electrically equivalent to the shunt 4,937,646 3 4 12 of FIG. 1. Between zones 6 and 7, the base-collector however, become apparent to those skilled in the art path of a transistor 15 is connected. The base terminal of after considering this speci?cation and the accompany transistor 15 is connected to the cathode terminal K of ing drawing which disclose the preferred embodiments the transistor via the drain-source path of a MOSFET thereof. All such changes, modi?cations, variations and 16 which is of the enhancement type. The gate terminal other uses and applications which do not depart from of MOSFET 16 is connected, on the one hand, via a the spirit and scope of the invention are deemed to be 17 to the anode-side inner zone 6 of the tran covered by the invention which is limited only by the sistor, and on the other hand, via a current source 18 to claims which follow. the cathode terminal K of the thyristor. Between the What is claimed is: base terminal of the photo transistor 15 and its emitter 1. An electronic component including a MOSFET terminal there may be an additional resistor 19, which ' having a ?rst semiconductor body having two major serves to increase the emitter-collector off-state volt surfaces, a gate electrode, a source electrode, and a age. threshold voltage for turning the MOSFET on, the With the thyristor connected through its two termi electronic component comprising: nals A, K to the gate-source voltage of FET 1, a con (a) a semiconductor switch having a second semicon stant current will ?ow to the cathode terminal of the ductor body fastened on one of the major surfaces thyristor through the zones 9 and 6, the capacitor 17 of the ?rst semiconductor body and the semicon and the current source 18. This current is not suf?cient . ductor switch turns on when a predetermined junc to turn the MOSFET 16 on. FET 1 is illustrated to tion temperature is reached, the semiconductor demonstrate its mechanical and physical arrangement 20 switch having a forward on-state voltage drop with respect to device 4 in FIG. 1 for thermal coupling lower than the threshold voltage of the MOSFET; purposes. FIG. 2, on the other hand, provides the elec (b) the ?rst and second semiconductor bodies are trical interconnection in a schematic diagram. connected together thermally; When the temperature of the MOSFET rises also the (c) two electrodes are disposed on the second semi temperature of thyristor 5 and of transistor 15 increases, 25 conductor body of the semiconductor switch; and as well as that of the other parts of the preferably inte (d) one of the two electrodes is coupled to the gate grated circuit. But the thyristor 5 cannot turn on auto electrode while the other of the two electrodes is matically, as the resistor 14 constitutes a strong shunt. The current of transistor 15, on the other hand, in connected to the source electrode. creases sharply with rising temperature, so that now 2. An electronic component according to claim 1, current ?ows from anode A and zones 9 and 6 through wherein the ?rst and second semiconductor bodies are the collector—emitter path of transistor 15 and zones 7 _ electrically insulated from each other. i and 8 to the cathode K. When a temperature critical for 3. An electronic component according to claim 1, the MOSFET 1 is reached, this current is suf?cient to wherein the semiconductor switch is in the form of a tire thyristor 5; it is turned on and shortcircuits the lateral thyristor. gate-source capacitance CGS of MOSFET 1. 4. An electronic component according to claim‘ 1, But at a temperature uncritical for MOSFET 1 a characterized in that the semiconductor switch is a steep voltage drop occurs between the terminals A and thyristor comprising at least two inner zones and two K, a sharply increasing current will ?ow through ca outer zones, and at least a shunt between one of its inner pacitor 17 into the gate terminal of MOSFET 16, since 40 zones and the outer zone contiguous thereto. the current through the current source 18 remains con 5. An electronic component according to claim 4, stant. Then, MOSFET 16 is turned on and conducts the further comprising: base current of the photo transistor 15 away. The latter, a transistor having an emitter-collector path con therefore, can be controlled to become non-conducting nected to the inner zones of the thyristor and a base . and thyristor 5 remains blocked. 45 terminal; and The entire arrangement according to FIG. 2 may be the base terminal of the transistor is connected via the constructed in integrated form on a chip of an area 1 X l source-drain path of said MOSFET to a cathode to 1X 2 mm. Concerning further details of the construc terminal of the thyristor, the MOSFET is an en tion of an according to FIG. 2, refer hancement type, the gate terminal of the MOSFET ence is made to German Patent Document DE-OS 33 is connected via a capacitor to the inner zone con 44 435, which the integrated circuit is described for tiguous to the outer connected to an anode terminal another purpose of use. which is one of the two terminals, and a current For the thyristor it applies here also that, as previ source having ?rst and second terminals, the ?rst ously mentioned in connection with FIG. 1, its forward terminal is connected to the gate terminal of the on-state voltage must be lower than the threshold volt MOSFET while the second terminal is connected age UT of the MOSFET. For with high to a cathode terminal which is the other one of the threshold voltages on the order of several volts, it may two terminals of the second semiconductor body. be suf?cient to use as the semiconductor switch a bipo 6. An electronic component according to claim 1, lar transistor instead of the thyristor. wherein the semiconductor switch is a bipolar transis There has thus been shown and described novel tem 60 tor. perature protected semiconductor device arrangements 7. An electronic component according to claim 2, which ful?ll all the objects and advantages sought . wherein the semiconductor switch is a bipolar transis therefor. Many changes, modi?cations, variations and I01‘. other uses and applications of the subject invention will, enact 65