Abstract:
A discretely constructed MOSFET is switched by a voltage applied between gate terminal and source terminal. The source terminal has a self-inductance in which a fast change of the load current induces a considerable voltage which opposes the applied gate-source bias. This opposing voltage is reduced since the source contact is connected to an auxiliary terminal which is largely magnetically decoupled from the source terminal. A control voltage is applied between gate terminal and auxiliary terminal. When a plurality of MOSFETs are connected in parallel, oscillations in the control circuit can thus be effectively suppressed.

Description:
This is a continuation of application Ser. No. 363,456, filed June 6, 1989, now abandoned, which is a continuation of application Ser. No. 112,223, filed Oct. 22, 1987, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention is directed to a semiconductor component having at least one power MOSFET whose semiconductor body has a source contact and a source terminal connected thereto, and also has a gate contact and a gate terminal connected thereto. 
     Such semiconductor components are activated by a control voltage applied between the source contact and the gate contact. In practice, the control voltage is applied between the source terminal and the gate terminal. The wire serving as the source terminal has a self-inductance when the load changes in time-wise fashion given turn-on or turn-off of the MOSFET, a voltage is induced in the inductance which opposes the control voltage in a switch-retarding fashion. When a plurality of power MOSFETs are connected in parallel and they are controlled in common from a single voltage source, then the inductance can cause high frequency oscillations with amplitudes which can destroy the FET input. These oscillations occur in the drive circuit due to unavoidable component tolerances. The oscillation frequency is critically determined by the inductance of the source terminal and is also determined by other parasitic network and component parameters. The amplitude of the oscillation is amplified by the large transconductance of the MOSFET. 
     The oscillations upon turn-on of power MOSFETs connected in parallel were described, for example, in the publication &#34;PCI October 1984 Proceedings&#34; pages 209 through 213 and in the publication &#34;MOTOROLA TMS POWER MOSFET DATA&#34;, pages A-49 through A-70. In order to prevent the high frequency oscillations, it is proposed to insert a respective resistor or a ferrite bead into the gate terminals of the MOSFETs connected in parallel. Tests, however, have shown that the described problems are in fact alleviated but cannot be completely eliminated when fast switching is to be undertaken. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to improve a semiconductor component of the said above described type such that the disadvantageous effect of the inductance of the source terminal is further diminished and the oscillations are avoided in MOSFETs connected in parallel, even given fast switching on the order of magnitude of less than one microsecond. 
     This object is achieved by an auxiliary terminal connected to the source contact, this auxiliary terminal being at least partially magnetically decoupled from the source terminal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of the power MOSFET arrangement or the invention; 
     FIG. 2 is also an embodiment of the invention; and 
     FIG. 3 is a plan view of a further embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The semiconductor component of FIG. 1 is constructed on an insulating, heat-conducting substrate 1. The substrate, for example, can be formed of a known aluminum oxide ceramic. It is provided with first interconnects 2, 12, with second interconnects 3, 13, and with third interconnects 4, 14. These interconnects lie parallel to one another and are arranged in mirror-symmetric fashion relative to an axis 24 of symmetry forming a longitudinal axis of the substrate 1. The substrate is also provided with a fourth interconnect 5 which resides on the symmetry axis 24. 
     The first interconnects 2, 12 and second interconnects 3, 13 are conductively connected to one another by bridges 15 or 16. The third interconnects 4, 14 are electrically connected to one another by bridges 17, 18. Together with the bridge 16, the interconnects 2, 12 form a first U-shaped conductor, whereas the interconnects 3, 13 form a second U-shaped conductor with the bridge 15. The two U-shaped conductors are turned by 180° relative to one another and are arranged on the substrate in interleaved fashion. 
     Semiconductor bodies 6 which each form a power MOSFET are arranged in two rows following one another on the first interconnects 2, 12. The semiconductor bodies 6 are each provided with a gate contact 7 and with a source contact 8. The source contacts 8 are connected to the second interconnects 3, 13 via, for example, bonding wires 9. Together with the bridge 15 and the bonding wires 9, the interconnects 3, 13 form the source terminal. The gate contacts 7 are each connected to the third interconnects 4, 14 via one or more bonding wires 11. Together with the bridges 17, 18 and the bonding wires 11, these interconnects form the gate terminal of the semiconductor component. The interconnects 2, 12 serve as a drain terminal connecting to a drain of the semiconductor body 6. 
     In addition, the source contacts 8 are connected to the interconnect 5 via bonding wires 10. Together with the interconnect 5, the bonding wires 10 form an auxiliary terminal for the drawing of the MOSFETs connected in parallel. In order to keep the bonding wires short, they lie at a right angle relative to the interconnects. 
     The semiconductor component is switched on by a gate voltage applied between the gate terminal and the auxiliary terminal. Since the interconnects 3, 13, i.e. the source terminals, are arranged at the one side of the row of semiconductor bodies, (at the outside of the substrate in the exemplary embodiment), and the interconnects for the drive of the semiconductor bodies are arranged at the other side of the row of semiconductor bodies, a high degree of magnetic decoupling of the drive circuit from the source terminals of the semiconductor element results. Such a semiconductor component can become fully conductive within, for example, 100 ns without high-frequency oscillations arising in the drive circuit. With a given position of the interconnects, the magnetic decoupling is all the better the further the bonding wires 9 carrying the load current are spaced from the bonding wire 10. The arrangement is optimum when, as illustrated, the bonding wires 9 and 10 project from the source contact 8 at opposite sides. 
     A further improvement of the drive behavior can be achieved in that the conductor systems belonging to the control circuit and composed of the bonding wires 10, 11 and of the interconnects 4 or 14 are arranged in close proximity to one another and lie at least partially parallel to one another. The inductance of the control circuit can thus be diminished. The bonding wires and interconnects can be arranged in as close proximity as possible based on insulation and manufacture considerations. 
     In FIG. 1, the semiconductor bodies 6 are arranged on the interconnects 2, 12 such that the bonding wires 10 and 11 lie relatively far apart. In the exemplary embodiment of FIG. 2, the semiconductor bodies are turned by 90° in comparison to the exemplary embodiment of FIG. 1. A spatially adjacent arrangement of the bonding wires 10 and 11 belonging to the control circuit becomes possible when the source and gate contacts lie opposite one another at the edge of the semiconductor bodies. 
     The drain terminals, source terminals, and gate terminals as well as the auxiliary terminals are connected to housing terminals 19, 20, 22, and 23. Reference numeral 19 forms the source housing terminal, 20 forms the drain housing terminal, 22 forms the gate housing terminal, and 23 forms the auxiliary housing terminal These housing terminals lead out of a housing enveloping the substrate, the semiconductor bodies, the interconnects, and the bonding wires, and are intended for connection to external voltage sources or to an external load. The housing terminals 19, 20 lie symmetrically on the bridges 15 or 16 relative to the axis 24 of symmetry or, expressed in other terms, lie on the yokes of the U-shaped conductor systems. The housing terminals 22, 23 are seated in the middle of the longitudinal extent of the third or fourth interconnects. When the semiconductor bodies 6 are seated uniformly distributed on the interconnects 2, 12 relative thereto, then a largely uniform current division and uniform turn-on conditions are obtained for all MOSFETs. 
     The exemplary embodiments of FIGS. 1 and 2 each comprise 6 semiconductor bodies. However, it is also possible to construct semiconductor components having fewer or more semiconductor bodies, preferably an even-numbered plurality of semiconductor bodies based on the same principle. It is also possible to construct semiconductor components according to the described principle which, for example, contain only a single arrangement lying at one side of the axis of symmetry. Moreover, it is conceivable to construct semiconductor components according to the illustrated principle which comprise only a single semiconductor body. 
     In a departure from the allocation of the U-shaped, first and second interconnects 2, 12, 3, 13 shown in FIGS. 1 and 2, these can also be interleaved with one another in the fashion of finger structures. 
     FIG. 3 shows a further exemplary embodiment. There the first and the second interconnects are each also designed as closed rings 26 or 27, and are arranged lying inside one another. The third interconnects 4, 14, 17, 18 which likewise form a ring, lie in the ring 27. Two of the semiconductor bodies lie on the symmetry axis 24. The housing terminals 19, 20 have been divided here and contact the rings 26, 27 at both sides of these semiconductor bodies. They lie at a right angle and symmetrically to the symmetry axis 24. 
     For especially high demands, a resistor 25 (FIG. 2) may be inserted into the gate terminal of every semiconductor body in a known fashion. For example, such a resistor can be a doped semiconductor chip which is soldered onto the interconnects 4, 14. The bonding wire 11 then contacts the upper side of the chip. 
     Although the invention has been described with respect to preferred embodiments, it is not to be so limited as changes and modifications can be made which are within the full intended scope of the invention as defined by the appended claims.