DE102006043485B4 - Power semiconductor module and method for operating a power semiconductor module with at least one controllable by field effect semiconductor device - Google Patents

Abstract

Method for operating a power semiconductor module, comprising the following steps:
Providing a power semiconductor module which has at least one semiconductor component (1, 2) with a semiconductor body (50) which can be controlled by field effect via a control terminal (13, 23), the semiconductor body (50) being connected to the control terminal (13) by means of a dielectric (5) , 23) is electrically isolated,
- Performing a switching operation phase (61), in which the controllable semiconductor component (1, 2) is alternately switched between a conductive state and a blocking state, wherein the driving of the semiconductor device by applying a first voltage (U _GS1 ) to the control terminal (13, 23),
- injecting electrons into the dielectric (5) during an injection operating phase (62) in which the control terminal (13, 23) is supplied with a second voltage (U _GS2 ) which is higher than the first voltage (U _GS1 ) that a positive total charge generated in the gate dielectric by radiation of ionizing particles is reduced or completely degraded.

Description

The The invention relates to power semiconductor modules having one or more field effect controllable semiconductor devices. Such semiconductor devices have a control connection, as well as a semiconductor zone to be controlled, the by means of a dielectric to the control terminal electrically is isolated. The dielectric is usually also used as a gate dielectric designated.

As a result an electrical potential of the control terminal is formed an outgoing from this electric field, through the gate dielectric passes through and the electrical conductivity of the to be controlled Semiconductor zone influenced. By changing the electrical potential of the control terminal leaves the conductivity selectively influence the semiconductor zone to be triggered.

Under certain operating conditions, it may be in the operation of such semiconductor devices to a positive charge of the gate dielectric of the semiconductor device come.

reason therefor can be, for example, ionizing radiation, as in nuclear power plants, hospitals or reinforced in space occurs. By the ionizing radiation are in the dielectric Electron-hole pairs generated. While the electrons due to their relatively high mobility Leaving gate dielectric almost instantaneously becomes a significant one Proportion of holes of impurities of the gate dielectric captured and remains there, so that the gate dielectric positively charged.

These Charging causes a shift in the threshold voltage of the semiconductor device. As a threshold voltage is understood to mean the voltage at the Control connection is created so that the semiconductor zone to be controlled a certain minimum conductivity having. The minimum conductivity can for example, by a given drain-source threshold current, z. 1 mA, in conjunction with a given drain-source voltage, z. B. 10 V, can be adjusted.

A positive charging of the gate dielectric causes n-channel semiconductor devices Decrease, with p-channel semiconductor devices an increase in the threshold voltage. Therefore, with n-channel semiconductor devices, in extreme cases, even to an undesirable Aufsteuern the semiconductor device come.

Though Is it possible, such a positive charge by a heat treatment of the device to reverse However, this procedure is because of the required high temperatures of about 500 ° C not practical, as it is at the required temperatures too to a change may come from other properties of the semiconductor device.

Out C. Picard, C. Brisset, O. Quittard and A. Hoffmann: "Radiation Hardening of Power MOSFETs using Electrical Stress, IEEE Transac., Nucl. Sc., Vol. No. 3, (2000) pp. 641-646 It is known that the injection of electrons into the gate oxide of a MOSFET through a Fowler-Nordheim tunnel mechanism the strike voltage of the MOSFET increases. In this publication became radiation hardening raising the threshold voltage of a MOSFET by a one-off Electron injection into the gate oxide proposed. This measure has the disadvantage that the rate of decrease of the threshold voltage with the radiation dose is not significantly reduced and the radiation hardness not fundamentally improved.

From the US 6548839 B1 It is known that LDMOS transistors under certain conditions hot electrons occur, causing a reduction in the threshold voltage of the transistor.

The The object of the present invention is a method to provide for the operation of a power semiconductor module, with the one undesirable high overall positive charge in the gate dielectric of a field effect controllable semiconductor device of the power semiconductor module can be reduced or reduced. Another object of the invention consists in the provision of such a power semiconductor module for execution of such a procedure.

These The object is achieved by methods according to the patent claims 1 and 23 and solved by a power semiconductor module according to claim 25.

According to the invention a first Power semiconductor module provided, the at least one through Field effect controllable semiconductor device has. In the semiconductor device it may be any field effect controllable semiconductor device, in particular to act a MOSFET or an IGBT.

The controllable semiconductor device comprises a semiconductor body, as well a control terminal for driving the semiconductor device, the by means of a gate dielectric, for example by means of a semiconductor oxide such as As silica, compared the semiconductor body is electrically isolated.

The Power semiconductor module and / or the controllable semiconductor component become regular operated in a Schaltbetriebsphase in which the controllable semiconductor device alternately switched between a conductive state and a blocking state becomes. The Schaltbetriebsphase can, for example, a conventional Inverter operation correspond.

In addition to Schaltbetriebsphase an injection operating phase is provided while the electrons in the gate dielectric be injected. The injected electrons recombine with the positive landings (the "holes") at their detention centers, such that the positive total charge present in the gate dielectric reduced or completely degraded becomes.

The Charge stored in a gate dielectric is more typical Way some nC. The injected charge, however, must be clear be bigger, preferred Values for this are in the range of 6 μC and 6 mC, corresponding to one over a period of 1 minute to 10 minutes supplied injection current of 0.1 uA-10 uA.

The Switching operation phase and the injection operating phase can be parallel performed to each other However, preferably the Schaltbetriebsphase during the Injection operating phase interrupted. Instead of an interruption the Schaltbetriebsphase may also be otherwise conditional break in the switching operation phase for the implementation an injection operation are used.

The injection of electrons is preferably carried out by means of an injection current which is generated by an electric field in the gate dielectric, which forms as a result of a voltage drop across the gate dielectric in the gate dielectric. The injection current density in the gate dielectric is preferably 0.1 μA / cm ² to 10 μA / cm ² .

The strength of this electric field in the gate dielectric is preferably greater than or equal to 7 MV / cm. Particularly preferably, the electric field is selected such that a preferably constant Fowler-Nordheim tunnel current is formed in the gate dielectric. The tunnel current is preferably between 0.1 μA / cm ² and 10 μA / cm ² .

The Frequency, with which such an injection of electrons are made intended to training an undesirably high overall positive charge in the gate dielectric depends in particular on the intensity of the radiation io nisierender Particles and can in typical applications of such semiconductor devices in the range of a few weeks or several months.

Of the Injection current can be applied by applying an electrical voltage the control terminal on the one hand and the semiconductor body on the other be effected.

The Applying the electrical voltage to the semiconductor body can in particular in the field the semiconductor zone to be controlled, an n-type emitter, a body zone, a drift zone, a field stop zone or a p-emitter to the Semiconductor body respectively.

optional can the application of electrical voltage also by means of a separate Connection made at one of the above areas of the semiconductor body is connected and preferably from a housing of the Led out semiconductor device is.

there is the polarity the voltage applied to the gate dielectric for a successful Injection of electrons in principle irrelevant. However, in the transition area of the gate dielectric to the semiconductor body recombination sites for free charge carrier ("Traps") located which Can bind electrons. Therefore, a positive voltage is preferable to the gate electrode, to electron injection from the substrate into the gate dielectric to effect and fill the traps there. Apart from that, one would Electron injection from the gate electrode rapidly destroys the Lead gate dielectric.

In dependence the choice of the location where the voltage is applied to the semiconductor body, and / or depending from an external circuit of the semiconductor device at certain polarities circuit advantages.

For example can be a voltage to generate the injection current with the same polarity connected to the same connection points of the semiconductor device be like the normal switching operation for aufsteuern of the semiconductor device voltage used in the conducting state.

What matters is that an electric field is created in the gate dielectric due to the applied voltage, causing an injection current through which electrons are injected into the gate dielectric. This electric field for generating an injection current has a field strength which is higher than the field strength of the electric field, which during the Schaltbetriebsphase due to a for controlling the semiconductor established in the conductive state voltage used in the dielectric.

Provided the field effect controllable semiconductor device a body zone, a drift zone, a field stop zone or a p-emitter may the voltage for generating an injection current also to the control terminal on the one hand and to the body zone, the drift zone, the field stop zone or the p-emitter on the other hand be created.

in the Case of an n-channel device, the application of the electrical Voltage for injecting electrons, preferably such that the gate electrode to a higher one electrical potential is placed as the external connection of the Body zone.

The Procedure has the advantage that it is easy to normal Operation of such a semiconductor device can be integrated. In In each case, electrons are repeatedly injected into the gate dielectric of the semiconductor device injected.

in the The simplest case is the injection of electrons into certain temporal - preferably equidistant - intervals be made. This is useful, for example, if the time is known after the positive total charge of the gate dielectric a predetermined maximum allowable Exceed value becomes. If there is a sufficiently strong injection of electrons Expiration of this charging time and thus before reaching an inadmissibly high positive total charge of the gate dielectric, so may be an unintentional Connecting the load path of the controllable semiconductor device be avoided.

The Injecting electrons is preferably done only then if before a change the threshold voltage of the controllable semiconductor device detected has been. For this purpose, the threshold voltage of the controllable semiconductor device in predetermined, preferably equidistant monitored over time intervals become.

A Change - in particular a sinking - the Tail voltage of the controllable semiconductor device can, for example by comparing the threshold voltage with a previously determined Threshold voltage or by comparing the value of a corresponding with the threshold voltage changing Size with one previously determined value of this size are determined.

As well may be the finding of a change - especially a sinking - the Tension by comparing the threshold voltage with a given Value of the threshold voltage or by comparing the value of a Corresponding to the threshold voltage changing size with a predetermined value of this size.

Prefers becomes a change the breakdown voltage thereby determined that the control terminal the controllable semiconductor device a predetermined voltage applied and a resulting load current of the controllable Semiconductor device is determined.

Of the Load current can be due to the voltage drop at one in the load circuit the controllable semiconductor device connected measuring resistor be determined.

As already explained at the beginning, is a positive total charge of the gate dielectric through Field effect controllable semiconductor device, in particular at n-channel Semiconductor devices considered to be critical, since it due to a Falling of its threshold voltage in an extreme case to an undesirable Aufsteuern the semiconductor device can come.

One Increasing the threshold voltage, however, is far less critical to watch. Therefore, in n-channel devices, an injection of electrons preferably made in the gate dielectric, if before a drop in the threshold voltage of the n-channel device found was, z. B. if it was previously determined that the current determined threshold voltage falls below a predetermined value Has.

The Decrease of the current threshold voltage of the controllable semiconductor device can be determined by the fact that to the gate electrode a predetermined Voltage applied and a resulting load current of the controllable semiconductor device measured and with a predetermined target load current of the controllable Semiconductor device is compared. The determination of the load current can z. B. by measuring the voltage drop at one in the load circuit the controllable semiconductor device connected measuring resistor respectively.

Corresponding the injection current can be determined by measuring the voltage drop This injecting current is applied to another measuring resistor generated.

Field effect controllable semiconductor devices of the type mentioned are often integrated into power semiconductor modules. Such power semiconductor modules according to the invention can also be one or more control circuits for injection of electrons in the gate dielectrics of one or more of the controllable semiconductor components of the power semiconductor module. By means of such a control circuit, one of the aforementioned methods can be realized in a simple manner.

The Invention will now be described with reference to exemplary embodiments with reference closer to figures explained. Show it:

1 a cross-section through a portion of a vertical n-channel IGBTs having a total positive charge gate dielectric, wherein between the gate electrode and the source electrode, an electrical voltage for generating an injection current can be applied,

2 a cross-section through a portion of an n-channel IGBT with a separate connection for supplying an injection current whose connection point is selected on the semiconductor body in the region of a formed in the body zone, p-doped tub,

3 a circuit diagram of a semiconductor module, which has a half-bridge of two n-channel IGBTs and a control circuit for generating a predetermined, to be fed via the gate electrode injection current,

4 an example of a possible time course of the gate-source voltage of an n-channel IGBT according to the 1 to 3 during an injection operating phase, and

5 a circuit diagram of a semiconductor module having a half-bridge of two n-channel IGBTs and a control circuit for generating a predetermined, to be fed via the gate electrode injection current, wherein each of the IGBTs has a separate external terminal for injecting an injection current into the gate dielectric.

In denote the figures - if not stated otherwise - same Reference numerals like elements with the same function.

1 shows a cross section through a portion of a vertical n-channel IGBT 1 , The IGBT 1 comprises a semiconductor body 50 with a p-emitter 55 , an optional field stop zone 54 , a drift zone 53 , a body zone 52 as well as with n-emitters or with an n-source area 51 , On the front of the semiconductor body 50 are gate dielectrics 5 arranged, which gate electrodes 6 opposite to the semiconductor body 50 electrically isolate.

Furthermore, on the front side of the semiconductor body 50 a source electrode 7 and on the back of the semiconductor body 50 a drain electrode 8th arranged. The gate electrode 6 , the source electrode 7 and the drain electrode 8th For example, they may be formed of aluminum or polysilicon or contain these materials. The source electrode 7 contacts both the source zone 51 as well as the body zone 52 on the surface of the semiconductor body 50 and close this short. For external wiring, the IGBT 1 a first load connection 11 (S = source), a second load connection 12 (D = drain) and a control terminal 13 (G = gate).

The gate dielectric 5 has an undesirable total positive charge which is the threshold voltage of the IGBT 1 undesirably degrades.

To such in the gate dielectric 5 is a source of voltage completely or partially dissipate positive charge surplus 9 intended. The from this voltage source 9 provided electrical voltage can by means of a switch 10 on the one hand to the control terminal 13 and, on the other hand, to the first load port 11 be created. This creates an injection current through which the gate dielectric 5 Electrons are supplied, which are the total positive charge of the gate dielectric 5 compensate in whole or in part, and thus a further drop in the threshold voltage of the IGBTs 1 prevent.

The function of the switch 10 is preferably by means of a control circuit, not shown for the IGBT 1 realized. The position of the switch 10 can be chosen anywhere. It is crucial that as a result of the operation of the switch 10 An injection current is generated by the electrons in the gate dielectric 5 be introduced.

2 shows a cross section through a portion of an IGBT 1 with an external connection 14 , which consists of a housing only schematically illustrated 1a of the IGBT 1 led out and over a metallization 70 one in the area of the body zone 52 trained, p-doped junction zone 56 with the semiconductor body 50 connected is. The connection zone 56 is of the same conductivity type as the bodyzone 52 , but preferably doped more strongly than these.

The source electrode 7 contacts the source zone 51 but not the body zone 52 so that the source zone 51 and the body zone 52 in contrast to the embodiment according to 1 not through the source electrode 7 are shorted.

As in the embodiment according to 1 can also with this arrangement by means of a switch 10 the voltage of a voltage source 9 to the control terminal 13 on the one hand and to the external connection 14 on the other hand.

The polarity of the voltage source 9 is selected according to a preferred embodiment of the invention so that the gate electrode 6 one opposite the semiconductor body 50 , in particular with respect to the connection zone 56 , has positive voltage. Basically, the polarity of the voltage source 9 however, both in this and in the embodiment according to 1 also be chosen vice versa.

3 shows the circuit diagram of a power semiconductor module with a first controllable by field effect semiconductor device 1 and a second field effect controllable semiconductor device 2 , The semiconductor device 1 has a first load connection 11 , a second load connection 12 as well as a control connection 13 on. Accordingly, the second semiconductor device 2 a first load connection 21 , a second load connection 22 as well as a control connection 23 on. The load paths of the semiconductor devices 1 and 2 are electrically connected in series to a half-bridge. Antiparallel to the load paths of the semiconductor devices 1 and 2 is each a freewheeling diode 3 respectively. 4 connected.

The power supply of the half-bridge via a positive supply voltage P, which the second load terminal 22 of the second semiconductor device 2 is supplied, as well as a negative supply voltage N, which the first load terminal 11 of the first semiconductor device 1 is supplied.

To control the half-bridge is a control circuit 40 intended. About an entrance 49 the control circuit 40 this is supplied to a pulse width modulated square-wave drive signal. This drive signal is from a unit 41 processed for signal conditioning and a gate drive 42 fed. The unit 41 For Signalaufberei device may include, for example, measures for level adjustment for galvanic decoupling, for signal inversion or the like.

The gate drive 42 is via a gate resistor 31 with the control terminal 13 of the first semiconductor device 1 connected. In normal operation, the first controllable semiconductor device 1 over the gate resistance 31 from the gate drive 42 on or off.

Furthermore, the control terminal can 13 the first controllable semiconductor device 1 one in an injection current driver 46 generated injection current I are supplied. The injection current driver 46 is part of a unit 45 for injection current treatment.

For decoupling of the two in the gate drive 42 and the injection current driver 46 generated drive signals are decoupling diodes 34 respectively. 35 produces seen.

The determination of the injection current I via the voltage drop, the injection current I at one between the Injektionsstromtreiber 46 and the control terminal 13 switched measuring resistor 33 generated. The voltage drop becomes one unit 47 to determine the injection current I is determined.

The injection current driver 46 and the unit 47 to determine the injection current together form a unit 45 for injection current treatment. The control circuit 40 further includes undervoltage protection 43 as well as a unit 44 for short-circuit protection and for adjusting the threshold voltage of the controllable semiconductor device 1 ,

Is it due to ionizing radiation to a positive total charge in the gate dielectric of the controllable semiconductor device 1 , So this causes a decrease in the voltage application of the controllable n-channel semiconductor device 1 , In an extreme case, the positive total charge of the gate dielectric can be used to control the load path of the semiconductor component 1 cause even if no Aufsteuersignal the gate drive 42 at the control terminal 13 is present. In the case of a simultaneously opened load path of the controllable semiconductor component 2 then it would be a short circuit of the half bridge.

In order to avoid this, it is advantageous if such a drop in the threshold voltage is recognized in good time, so that the controllable semiconductor component 1 an injection stream is supplied and the threshold voltage can be raised again.

In order to detect a decrease in the threshold voltage, a low-impedance measuring resistor connected in the load circuit is provided 32 provided, on which a load current-dependent voltage drop arises, which by means of the unit 44 for short-circuit protection and for adjusting the threshold voltage is determined.

Builds in the course of the regular operation of the half-bridge in the gate dielectric of the semiconductor device 1 a positive total charge on and If this leads to a drop in the threshold voltage, this will be the case if the drive of the semiconductor component remains constant 1 via the gate drive 42 an increase in the load current. This increase may occur with the unit in a measurement operation phase during which the regular operation of the half-bridge is interrupted 44 be detected for short-circuit protection and adaptation of the threshold voltage. In such a measurement operation phase, it is necessary that the semiconductor device 1 is operated outside its saturation, since in saturation a drop in the threshold voltage does not necessarily cause a significant change in the load current. During the measuring phase of operation, the gate voltage, ie between the control terminal 13 and the first load terminal 11 applied voltage, preferably smaller than 15 V.

Represents the unit 44 detects such a drop in the threshold voltage, it causes the gate drive 42 to temporarily suspend the regular circuit operation of the power semiconductor module and instead the unit 45 to enable the injection current treatment to the gate dielectric of the semiconductor device 1 as explained, to supply a defined, preferably constant injection current I.

The charge stored in the gate dielectric is typically a few nC. The injected charge, however, must be significantly larger preferred values for this are in the range of 6 μC and 6 mC, corresponding to one over a period of 1 minute to 10 minutes supplied injection current of 0.1 uA-10 uA.

In order to check whether and to what extent the injection current I as desired increases the threshold voltage of the controllable semiconductor component 1 causes the change in the threshold voltage during the injection operating phase can be checked.

An increase in the threshold voltage causes the drive voltage of the controllable semiconductor component remaining constant 1 In general, an increase in the resistance of the load path of the controllable semiconductor device 1 , As the controllable semiconductor device 1 When injection is preferably operated far in the saturation region, an increase in the threshold voltage hardly affects the resistance of the load path. As a result, from an observation of the load path of the controllable semiconductor device 1 During the injection flowing through the flow, it is difficult to conclude that the threshold voltage has changed.

To avoid this difficulty, the injection current may be interrupted during the injection phase of operation and the controllable semiconductor device 1 be driven with a measurement drive voltage which is lower than the drive voltage required for generating an injection current I and the one drive of the semiconductor device 1 ensures its saturation.

The different operating phases are described below on the basis of 4 explained in more detail. 4 shows an example of a possible time course of the gate-source voltage U _{GS of} a controllable semiconductor device 1 according to 3 ,

The controllable semiconductor component is initially in a Schaltbetriebsphase 61 controlled by a pulse width modulated gate-source-square-wave voltage with a maximum value U _GS1 .

The switching operation phase 61 follows an injection operating phase 62 in the phases 62a and 62b alternately follow each other.

During the phases 62a For example, an injection operation is performed by increasing the gate-source voltage U _GS for generating an injection current to a value U _GS2 which is set higher than the value U _GS1 , which is preferably 10 V to 15 V.

In the phases 62b in which the power semiconductor component is in a measurement operating state, it should be determined whether an increased threshold voltage of the semiconductor component is present and / or whether it is necessary to cause an injection of electrons into the gate dielectric of the semiconductor component.

In measuring operation, the semiconductor device is driven with a gate-source voltage U _GS3 , which is smaller than the voltage U _GS2 . The voltage U _GS2 is chosen so that the controllable semiconductor device is operated out of saturation. The voltage U _GS2 is preferably equal to or more preferably smaller than the voltage U _{GS1 selected} in normal switching operation.

Exceeds the load current of the controllable semiconductor device with applied gate-source voltage U _GS3 a predetermined, suitably selected reference value, it can be concluded that caused by a positive total charge of the gate dielectric lowering of the _threshold voltage.

Likewise, a drop in the threshold voltage can also be determined by two or more successively in different measuring operating phases 62b determined load currents anstei show a tendency.

After it has been determined that there is a fall in the threshold voltage, an injection phase can be initiated 62a be initiated by a predetermined time duration, in which the semiconductor device is driven with a voltage U _GS2 . The voltage U _GS2 is chosen such that electrons are supplied to the gate dielectric of the controllable semiconductor component as a result of an injection tunneling current and the total positive charge of the gate dielectric is thereby wholly or partially neutralized.

After completion of the injection phase 62a can assess the effect of the injection tunneling current during a further measurement phase 62b Checked and - if necessary - another injection phase 62a be initiated.

This method with alternating measuring phases 62b and injection phases 62a can be continued until in a measuring phase 62b an undershooting of the predetermined load current value is detected, which is synonymous with the fact that the threshold voltage of the semiconductor device is within a permissible range. Subsequently, the regular Schaltbetriebsphase can again 61 of the semiconductor device.

The measurement drive voltage U _GS3 fed to the semiconductor _component can be supplied by the injection _{current driver} 46 or preferably from the gate driver 42 to be provided.

In 3 is exemplary only the input circuit of the first controllable semiconductor device 1 shown. In the same way can also the second controllable semiconductor device 2 through one with the control circuit 40 identical control circuit further controlled and operated according to one of the methods described above.

In addition, for driving the second semiconductor device 2 the resistors 31 and 33 or the diodes 34 respectively. 35 appropriate resistors and diodes are provided.

It may be advantageous to use these resistors and / or diodes not only for the control of the arrangement in the injection mode but also for driving the arrangement in normal switching operation. The measuring resistor 32 in the load circuit can as well as the unit 44 both from the control circuit 40 as well as being used by the further control circuit.

Notwithstanding the embodiment according to 3 is in the embodiment according to 5 that of the injection current driver 46 generated injection current I the controllable semiconductor device 1 not via its control port 13 but via a separate external injection port 14 fed. The external injection port 14 can, for example, as in the controllable semiconductor device 1 according to 2 by means of a connection zone 56 on the semiconductor body 50 be connected.

In the switching operation phase, this external control connection 14 to the potential of the first load connection 11 especially the external control connection 14 by means of a switch with the first load connection 11 be electrically connected.

In the injection operating phase, the connection is made 14 applied a potential that is smaller than the potential of the first load terminal 11 , Between the injection current driver 46 and the injection port 14 are still a resistance 33 and a diode 36 connected in series.

The second controllable semiconductor device 2 also has an injection port 24 on. Also in the embodiment according to 5 can control the second controllable semiconductor device 2 have a control circuit which is constructed as the control circuit 40 , In addition, for the second controllable semiconductor device 2 the resistors 31 and 33 or the diodes 34 and 36 appropriate resistors and diodes are provided.

The basis of 4 explained method can be used appropriately adapted for any other components. It occurs in the phases 62a instead of the gate-source drive voltage U _GS, the voltage which is applied to the semiconductor component for generating an injection current in the gate dielectric.

For controllable semiconductor components whose load paths, for example, as with the controllable semiconductor devices 1 and 2 according to the 3 respectively. 5 are connected in series to a half-bridge, an injection of electrons into the gate dielectric to increase the threshold voltage can be done not only by applying an external voltage to the gate dielectric, but additionally or alternatively also by specifically generating a short circuit of the half-bridge becomes.

at Such a short circuit of the half bridge occurs in the controllable Semiconductor devices to load currents that are much higher than the load currents the relevant controllable semiconductor devices in normal operation.

The increased in such a way load currents resulting fast electrons ("hot Electrons ") penetrate from the semiconductor body in the dielectric and cause a reduction there or a reduction of the positive overall charge present there. Such a Short circuit of the half bridge can be controlled by a targeted simultaneous control of the controllable Semiconductor semiconductor devices take place.

Around a thermal overload To avoid the controllable semiconductor devices, such must Short circuit will be temporary. Preferably, several such short-term shorts the half bridge at predetermined time intervals. The time interval between each other following short circuits must be chosen be that a thermal overload the semiconductor devices reliable is avoided.

Of course you can a short-circuit operation corresponding operation even with individual controllable semiconductor devices are performed by the load path controlled and to the load terminals a sufficiently high voltage in the forward direction is created.

The invention has been described in the embodiments according to the 1 to 5 exemplified by IGBTs. In principle, however, the invention can be applied to any field-effect-controllable semiconductor components, in particular MOSFETs.

Farther It is not necessary that the positive total charge is required of the gate dielectric caused by ionizing radiation has been.

The described method for detecting the undershooting of the threshold voltage and controlling electron injection into the gate dielectric can be implemented at the chip level, but preferably at the system level become. Advantageously, can the opposite conventional power semiconductor modules such as B. so-called smart power modules (SPMs) additionally required Components are integrated into the existing control circuits. SPMs typically combine multiple controllable semiconductor devices, for example, in half or full bridge circuits. thats why it useful, too the detection of reduced threshold voltages and the control of the To combine electron injection with the functions of an SPM.

1

first controllable semiconductor device

1a

Housing of first controllable semiconductor device

2

second controllable semiconductor device

3

first Freewheeling diode

4

second Freewheeling diode

5

Gate dielectric

6

Gate electrode

7

Source electrode

8th

Drain

9

voltage source

10

switch

11

first Load connection of the first controllable semiconductor device

12

second Load connection of the first controllable semiconductor device

13

control connection the first controllable semiconductor device

14

external Injection port of the first controllable semiconductor device

21

first Load connection of the second controllable semiconductor device

22

second Load connection of the second controllable semiconductor device

23

control connection of the second controllable semiconductor device

24

external Injection port of the second controllable semiconductor device

31

gate resistor

32

Shunt resistor

33

measuring resistor for determining the injection current (Fowler-Nordheim tunnel current)

34

first decoupling diode

35

second decoupling diode

36

diode

40

control circuit

41

unit for signal conditioning

42

Gate drive

43

Undervoltage protection

44

unit for short-circuit protection and adaptation of the threshold voltage

45

unit for injection current treatment

46

Injection current driver

47

unit for determining the injection current

49

entrance for drive signal

50

Semiconductor body

51

n-emitter

52

Body zone

53

drift region

54

Field stop zone

55

p-emitter

56

contiguous zone

61

Switch Operation phase

62

Injection phase of operation

62a

injection operation

62b

measuring mode

70

electrode for connection zone

I

injection current

N

negative Supply voltage of the half-bridge (?)

P

positive Supply voltage of the half-bridge

t

Time

U

output the half bridge

U _GS

driving voltage

U _GS1

driving voltage in the switching operation phase

U _GS2

driving voltage while the injection

U _GS3

driving voltage while of measuring operation

V _D

reference voltage for undervoltage protection

Claims (25)

Method for operating a power semiconductor module, comprising the following steps: - providing a power semiconductor module which has at least one field effect via a control connection ( 13 . 23 ) controllable semiconductor component ( 1 . 2 ) with a semiconductor body ( 50 ), wherein the semiconductor body ( 50 ) by means of a dielectric ( 5 ) opposite the control terminal ( 13 . 23 ) is electrically isolated, - performing a switching operation phase ( 61 ), in which the controllable semiconductor component ( 1 . 2 ) is alternately switched between a conductive state and a blocking state, wherein the control of the semiconductor device by applying a first voltage (U _GS1 ) to the control terminal ( 13 . 23 ), - injecting electrons into the dielectric ( 5 ) during an injection operating phase ( 62 ), in which the control connection ( 13 . 23 ) is supplied with a second voltage (U _GS2 ) which is higher than the first voltage (U _GS1 ), so that a positive total charge generated in the gate dielectric by radiation of ionizing particles is reduced or completely degraded. Method according to Claim 1, in which the injection of electrons takes place by means of an injection current (I) which is injected into the dielectric ( 5 ) is fed. Method according to Claim 2, in which the injection current (I) is generated by an electric field in the dielectric ( 5 ) having a thickness of at least 7 MV / cm. having. Method according to one of the preceding claims, in which a Fowler-Nordheim tunneling current in the dielectric ( 5 ) occurs. Method according to one of claims 2 to 4, wherein the injection current (I) by applying an electrical voltage (U _GS ) between the control terminal ( 13 . 23 ) and the semiconductor body ( 50 ) he follows. Method according to Claim 5, in which the electrical voltage (U _GS ) in the region of the semiconductor zone to be controlled ( 53 ), an n-type emitter ( 51 ), a body zone ( 52 ), a drift zone ( 53 ), a field stop zone ( 54 ) or a p-emitter ( 55 ) to the semiconductor body ( 50 ) is created. Method according to Claim 5 or 6, in which the application of the electrical voltage (U _GS ) to the semiconductor body ( 50 ) by means of a separate connection ( 14 ) he follows. Method according to Claim 6, in which the separate connection ( 14 ) from a housing ( 1a ) is led out of the semiconductor device. Method according to one of the preceding claims, in which the controllable semiconductor component is an n-channel component ( 1 . 2 ) and in which during the injection of electrons the electrical potential of the control terminal ( 13 . 23 ) is higher than the electrical potential of the semiconductor body ( 50 ). The method of claim 1, wherein injecting electrons into the dielectric ( 5 ) in that in the semiconductor body ( 50 ) a high current is generated, which causes the formation of fast electrons, which in the dielectric ( 5 ). Method according to one of the preceding claims, in which the injection of electrons is carried out if a change in the threshold voltage of the controllable semiconductor component ( 1 . 2 ) was detected. The method of claim 11, wherein the change the threshold voltage by comparing the threshold voltage with a previously determined threshold voltage or by comparing the Value of a change corresponding to the threshold voltage Size with one previously determined value of this size was determined. The method of claim 11, wherein the change the threshold voltage by comparing the threshold voltage with a predetermined value of the threshold voltage or by comparing the value a corresponding to the threshold voltage changing Size with one predetermined value of this size determined becomes. Method according to one of claims 11 to 13, wherein the change in the threshold voltage is determined by the fact that to the control terminal ( 13 . 23 ) a predetermined voltage sets and a resulting load current of the controllable semiconductor device is measured. The method of claim 14, wherein the load current through the voltage drop across a connected in the load circuit of the controllable semiconductor device measuring resistor. 32 ) is determined. Method according to one of Claims 12 to 15, in which the injection of electrons takes place when a drop in the threshold voltage of the controllable semiconductor component ( 1 . 2 ) was found to be less than or equal to 20% of a predetermined or previously determined threshold voltage. Method according to one of claims 11 to 16, wherein the Location of detecting a change in the threshold voltage the detection of a drop in the threshold voltage occurs. Method according to one of claims 1 to 9, wherein the injecting of electrons at predetermined time intervals independent of a change the threshold voltage is repeated. Method according to one of the preceding claims, in which the switching operating phase ( 61 ) during the injection operating phase ( 62 ) is interrupted. Method according to one of Claims 1 to 18, in which the switching operating phase ( 61 ) during the injection operating phase ( 62 ) is not interrupted. Method according to Claim 19 or 20, in which the injection of the electrons is effected by means of an injection voltage (U _GS1 ) in the switching operation phase ( 61 ) increased, applied to the control terminal Aufsteuerspannung (U _GS2 ) takes place. Method according to one of the preceding claims, in which the controllable semiconductor component ( 1 . 2 ) is a MOSFET or an IGBT. Method for operating a power semiconductor module with the following steps: (a) providing a power semiconductor module with two field-effect-controllable semiconductor components ( 1 . 2 ), each having a control terminal ( 13 . 23 ) and a load path and their load paths are connected in series to a half-bridge, wherein each semiconductor device ( 1 . 2 ) a semiconductor body ( 50 ), which in each case by means of a dielectric ( 5 ) opposite the respective control terminal ( 13 ) is electrically isolated, (b) performing a switching operation phase ( 61 ) in which the two controllable semiconductor components ( 1 . 2 ) are none or exactly one in a conducting state at any time, and (c) carrying out an injection operating phase in which a short circuit of the half-bridge by simultaneously controlling the two controllable semiconductor components ( 1 . 2 ), so that in the semiconductor bodies ( 50 ) generate high currents, which cause the formation of fast electrons, which in the dielectrics ( 5 ), so that a positive total charge generated in the gate dielectric by radiation of ionizing particles is reduced or completely degraded. The method of claim 23, wherein a plurality of injection operating phases according to step (c) are spaced apart in time. Power semiconductor module comprising the following features: - at least one field-effect-controllable semiconductor device ( 1 . 2 ) comprising a semiconductor body ( 50 ), and a control terminal ( 13 . 23 ), which by means of a dielectric ( 5 ) with respect to a semiconductor region ( 51 . 52 . 53 ) of the semiconductor body ( 50 ) is electrically isolated, - a drive unit ( 40 ), which is designed to control the operation of the controllable semiconductor component ( 1 . 2 ) according to a method according to any one of the preceding claims.