METHOD FOR MONITORING AT LEAST ONE SEMICONDUCTOR ELEMENT IN A SEMICONDUCTOR MODULE

Abstract

A method for monitoring a semiconductor element in a semiconductor module, wherein the semiconductor module has feed lines contacting the semiconductor element, includes arranging a magneto-optical sensor in a region of the semiconductor element or of at least one of the feed lines, reflecting a polarized light signal from the magneto-optical sensor or transmitting a polarized light signal through the magneto-optical sensor, and determining a current from a polarization of the reflected or transmitted light signal.

Claims

1.-21. (canceled)

22. A method for monitoring a semiconductor element in a semiconductor module, wherein the semiconductor module comprises feed lines contacting the semiconductor element, the method comprising: arranging a magneto-optical sensor in a region of the semiconductor element or of at least one of the feed lines; reflecting a polarized light signal from the magneto-optical sensor or transmitting a polarized light signal through the magneto-optical sensor, and determining a current from a polarization of the reflected or transmitted light signal.

23. The method of claim 22, further comprising guiding the polarized light signal to the magneto-optical sensor by way of a fiber-optic conductor.

24. The method of claim 23, further comprising: arranging the magneto-optical sensor and at least a part of the fiber-optic conductor within the substrate; and guiding the polarized light signal onto the magneto-optical sensor within the substrate.

25. The method of claim 22, further comprising determining from the polarization of the reflected or transmitted light signal a two-dimensional current density distribution.

26. The method of claim 22, wherein the magneto-optical sensor comprises a magneto-optical thin film, and further comprising detecting a transient current signal having an amplitude dynamic of at least 100 and a rise time of at most 10 ?sec.

27. The method of claim 26, wherein the transient current signal is determined by undersampling.

28. The method of claim 27, further comprising triggering the undersampling with a clock signal from a frequency converter, wherein the clock signal is delayed by a defined delay.

29. The method of claim 22, further comprising: determining a temperature of the magneto-optical sensor; and determining the current as a function of the temperature of the magneto-optical sensor and the polarization of the reflected or transmitted light signal.

30. A semiconductor module, comprising: a semiconductor element and feed lines for contacting the semiconductor element; a light source designed to generate a polarized light signal; a magneto-optical sensor arranged in a region of the semiconductor element or of at least one feed line and designed to reflect or transmit the polarized light signal generated by the light source; a detection unit designed to convert the reflected or transmitted polarized light signal into an electrical signal; and an evaluation unit designed to determine a current from a polarization of the reflected or transmitted polarized light signal.

31. The semiconductor module of claim 30, further comprising a fiber-optic conductor connecting the light source or the detection unit, or both, to the magneto-optical sensor.

32. The semiconductor module of claim 31, further comprising a substrate on which the semiconductor element is disposed, with the magneto-optical sensor and at least a part of the fiber-optic conductor running within the substrate.

33. The semiconductor module of claim 30, wherein the magneto-optical sensor is arranged at a distance of at most 1 mm from the semiconductor element or from at least one feed line.

34. The semiconductor module of claim 30, wherein the magneto-optical sensor comprises a first magneto-optical material and a second magneto-optical material that differs from the first magneto-optical material in respect of sensitivity.

35. The semiconductor module of claim 34, wherein the first magneto-optical material is used to determine a first current, and wherein the second magneto-optical material is used to determine a second current, which is larger than the first current.

36. The semiconductor module of claim 30, wherein the magneto-optical sensor comprises a magneto-optical thin film designed to detect a transient current signal having an amplitude dynamic of at least 100 and a rise time of at most 10 ?sec.

37. A control unit designed to drive light sources of the semiconductor module of claim 30, wherein the control unit is part of the evaluation unit.

38. A computer program product, comprising a computer program embodied in a non-transitory computer readable medium, wherein the computer program, when loaded into a computer and executed by the computer, causes the computer to execute a method as set forth in claim 22.

39. A magneto-optical sensor for determining a current in a semiconductor module as set forth in claim 30, said magneto-optical sensor arranged in a region of the semiconductor element or of at least one feed line and designed to reflect or transmit the polarized light signal generated by the light source.

40. The magneto-optical sensor of claim 39, comprising a first magneto-optical material and a second magneto-optical material that differs from the first magneto-optical material in respect of sensitivity, wherein the first magneto-optical material is used to determine a first current, and wherein the second magneto-optical material is used to determine a second current, which is larger than the first current.

41. A power converter, comprising a semiconductor module as set forth in claim 30.

Description

[0030] The invention is explained and described in more detail below with reference to the exemplary embodiments illustrated in the figures, in which:

[0031] FIG. 1 shows a schematic illustration of a first embodiment of a semiconductor module, in cross section,

[0032] FIG. 2 shows a schematic illustration of a second embodiment of a semiconductor module, in cross section,

[0033] FIG. 3 shows a schematic three-dimensional illustration of a third embodiment of a semiconductor module,

[0034] FIG. 4 shows a schematic illustration of a fourth embodiment of a semiconductor module, in cross section,

[0035] FIG. 5 shows a schematic illustration of a fifth embodiment of a semiconductor module, in cross section,

[0036] FIG. 6 shows a schematic illustration of a sixth embodiment of a semiconductor module,

[0037] FIG. 7 shows an enlarged schematic illustration of a magneton optical sensor, and

[0038] FIG. 8 shows a schematic illustration of a power converter having a semiconductor module.

[0039] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each present individual features of the invention, to be considered independently of one another, which also each develop the invention independently of one another, and hence are also to be regarded as a constituent part of the invention individually or in a different combination from that shown. Furthermore, the described embodiments may also be supplemented by further features of the invention which have already been described.

[0040] Identical reference characters have the same meaning in the different figures.

[0041] FIG. 1 shows a schematic illustration of a first embodiment of a semiconductor module 2, in cross section. The semiconductor module 2 has a semiconductor element 4 and a substrate 6, wherein by way of example the semiconductor element 4 takes the form of an insulated-gate bipolar transistor (IGBT). The semiconductor element 4 may also take the form of a metal-oxide semiconductor field-effect transistor (MOSFET), a field-effect transistor, a diode, a logic gate, in particular a field programmable gate array (FPGA), or another semiconductor. In particular, the semiconductor element 4 has a surface area of at least 10 mm.sup.2. The substrate 6 comprises a dielectric material layer 8 which contains a ceramic material, for example aluminum nitride or aluminum oxide, or an organic material such as a polyamide. Further, the dielectric material layer 8 has a thickness d of 25 ?m to 400 ?m, in particular 50 ?m to 250 ?m. In addition, on a side facing the semiconductor element 4, the substrate 6 comprises an in particular textured upper metallized element 10 and, on a side remote from the semiconductor element 4, it comprises a lower metallized element 12, wherein the upper metallized element 10 and the lower metallized element 12 are made for example from copper and are also called copper foil. The lower metallized element 12 of the substrate 6 is connected to a heat sink 14, in particular in a substance-to-substance bond.

[0042] On a side facing the substrate 6, the semiconductor element 4, which for example takes the form of an IGBT, has a contact-making element 16 in the form of a collector contact C, wherein a further contact-making element 16 in the form of an emitter contact E is arranged on a side remote from the substrate 6. A gate contact of the IGBT is not illustrated in FIG. 1, for reasons of clarity. The emitter contact E is connected to a first feed line 20 of the upper metallized element 10 of the substrate 6 by a bond connection 18, wherein the collector contact C of the semiconductor element 4 is connected in a substance-to-substance bond to a second feed line 22 of the upper metallized element 10 which is electrically insulated from the first feed line 20. The substance-to-substance bond is made by soldering or sintering. The second feed line 22 is connected to an electrical terminal element 24 by a bond connection 18. In addition, the semiconductor module 2 comprises a housing 26, which is made for example from a dielectric material, in particular a plastics material.

[0043] Further, the semiconductor module 2 has a magneto-optical sensor 28 that makes contact with the housing 26 above the semiconductor element 4. As a result of the arrangement illustrated in FIG. 1, and using the Kerr effect, the magneto-optical sensor 28 is configured to monitor a current, in particular a transient current, of the semiconductor element 4, wherein the magneto-optical sensor 28 is arranged in a magnetic field H of the semiconductor element 4, electrically isolated from the semiconductor element 4. The magneto-optical sensor 28 is constructed from a magneto-optical layer 28a, which contains for example garnet, and a reflecting layer 28b, which is applied to the magneto-optical layer 28a for example by sputtering. In particular, the magneto-optical layer 28a has a thin film with magneto-optical properties. The magneto-optical sensor 28 is connected to an optical transmitting and receiving unit 32, also designated an optical transceiver, by a fiber-optic conductor 30. The fiber-optic conductor 30 has optical fibers that are configured to maintain polarization. The optical transmitting and receiving unit 32 comprises a light source 34, which generates a polarized light signal Lp. For example, the light from a polarizer is polarized. The polarized light signal Lp is reflected by the reflecting layer 28b of the magneto-optical sensor 28, with the reflected light signal Li striking a detection unit 36. The detection unit 36 has for example an opto-electronic converter with an upstream polarization filter that filters the reflected light signal Lr and converts it into an electrical signal. In particular, a light intensity of the reflected light signal Lr is converted into a current by at least one light-sensitive diode, for example a photodiode or PIN diode. The fiber-optic conductor 30 is connected to the housing 26 of the semiconductor module 2 by a plug connector 38. The electrical signal is further processed in an evaluation unit 40, wherein a current is determined from a polarization of the reflected light signal Lr. The evaluation unit 40 has a control unit 42.

[0044] In the evaluation unit 40, parallel to the time-related magnetic field measurements H(t) of the magneto-optical sensor 28 are drive pulses, in particular gate signals, with the result that transient current signals having for example an amplitude dynamic of at least 100 and a rise time in the region of at most 10 ?m can be detected. It is likewise possible to determine the output at a particular instant.

[0045] Measurement of a polarization angle F(t) is the starting point, and within an actuation range of the magneto-optical sensor 28 there is, at any given point in time t, a linear relationship with current density I(t):

F(t)=C.sub.MO.Math.H(t)C.sub.MO.Math.I(t)/(2??r)

Taking into account intrinsic temperature effects of the embedded layers, first the spacing r and the polarization angle C.sub.MO=f(T) are dependent on temperature.

F(t,T)=C.sub.MO(T).Math.I(t)/(2?.Math.r(T))

Alternatively, the temperature dependence of the polarization angle may be determined as close to I(t)=0 and be used as a correction term. If the current I(t) at a particular instant is known, then working backward it is possible to determine a temperature.

[0046] The magneto-optical thin films have sufficient sensitivity to detect typical current densitiesthat is to say magnetic fields in the region of semiconductor elements 4. Further, magneto-optical effects are typically highly dynamic, so magneto-optical layers can easily follow fast semiconductor transient currents during switching-on and switching-off procedures. In particular, fast light-sensitive diodes such as photodiodes can detect local transient currents in reliably electrically isolated manner without complex switching.

[0047] Since polarization behavior of the magneto-optical sensor 28 is temperature-dependent, with polarization reducing as temperature increases, the accuracy of determining the current can be improved by in particular simultaneous measurement of the temperature of the magneto-optical sensor 28. For this purpose, a temperature of the magneto-optical sensor 28 is determined, for example optically with the aid of an additional IR light signal. Then, the current is determined in a manner dependent on the temperature of the magneto-optical sensor 28 and the polarization of the reflected light signal Lr. The temperature-dependent polarization behavior can be calibrated empirically using a lookup table, a model and/or with the aid of a digital twin.

[0048] FIG. 2 shows a schematic illustration of a second embodiment of a semiconductor module 2, in cross section, wherein a magneto-optical sensor 28 is arranged in a cavity 44 in the housing 26, above the second feed line 22. As a result of the arrangement illustrated in FIG. 2, and using the Kerr effect, the magneto-optical sensor 28 is configured to monitor a current, in particular a transient current, in the region of the second feed line 22, wherein the magneto-optical sensor 28 is arranged in a magnetic field H of the second feed line 22. Otherwise, the construction of the semiconductor module 2 in FIG. 2 corresponds to that in FIG. 1.

[0049] FIG. 3 shows a schematic three-dimensional illustration of a third embodiment of a semiconductor module 2. Semiconductor elements 4 make contact on a substrate 6, wherein, on a side of the semiconductor elements 4 remote from the substrate 6, a heat sink 14 is thermally connected to the semiconductor elements 4. Arranged in the substrate 6 below the semiconductor elements 4 are magneto-optical sensors 28, which take the form of an electro-optical circuit board, EOCB for short. The magneto-optical sensors 28 are configured to dynamically detect a local magnetic field and its transient characteristic, wherein this local magnetic field is used as a measure of the local current density and semiconductor temperature T.sub.Junction. A polarized light signal Lp, generated by a light source 34, is guided from an optical transmitting unit 46 by way of a fiber-optic conductor to the magneto-optical sensor 28. The light signal Lr reflected by the magneto-optical sensor 28 is guided by way of a further fiber-optic conductor 30 to an optical receiving unit 48 which comprises a detection unit 36. In particular, the magneto-optical sensors 28 and fiber-optic conductors 30 are fixed in the EOCB, with the result that vibrations that may disrupt the detection of changes in polarization are suppressed. The optical transmitting units 46 and optical receiving units 48 are connected for example to a common evaluation unit 40, which is not illustrated in FIG. 3, for reasons of clarity. In particular, the light sources 34 are driven by a common control unit 42 of the evaluation unit 40. Otherwise, the construction of the semiconductor module 2 in FIG. 3 corresponds to that in FIG. 1.

[0050] FIG. 4 shows, in cross section, a schematic illustration of a fourth embodiment of a semiconductor module 2, which has a substrate 6 on which there is connected a semiconductor element 4 taking the form for example of an IGBT. In particular, the semiconductor element 4 is of the flip-chip type and makes contact on the substrate 6 by a planar construction and connection technique, wherein the emitter E is connected to a first feed line 20 and the collector Cis connected to a second feed line 22 by way of a spacer element 50. A gate contact of the IGBT is not illustrated in FIG. 4, for reasons of clarity.

[0051] A magneto-optical sensor 28, which is connected to an optical transmitting and receiving unit 32 by a fiber-optic conductor 30, is arranged to run within the substrate 6. The magneto-optical sensor 28 is integrated with a fiber-optic conductor 30 in a recess 52 in a dielectric material layer 8 of the substrate 6. A polarized light signal Lp, generated by a light source 34, is guided from the optical transmitting and receiving unit 32 by way of a polarizer 54 and the fiber-optic conductor to the magneto-optical sensor 28. The light signal Lr reflected by the magneto-optical sensor 28 is reflected by way of the fiber-optic conductor 30 and the polarizer 54 back to the optical transmitting and receiving unit 32. A current is determined in the evaluation unit 40, from a polarization of the reflected light signal Lr. Otherwise, the construction of the semiconductor module 2 in FIG. 4 corresponds to that in FIG. 3.

[0052] FIG. 5 shows a schematic illustration of a fourth embodiment of a semiconductor module 2, in cross section, wherein a polarized light signal Lp, generated by a light source 34, is guided from an optical transmitting unit 46 by way of a polarizer 54 and a fiber-optic conductor 30 to the magneto-optical sensor 28. The polarized light signal Lp is transmitted by the magneto-optical sensor 28, wherein the transmitted light signal Lt is guided by way of a fiber-optic conductor 30 to an optical receiving unit 48, which comprises a detection unit 36. A current is determined in the evaluation unit 40, from a polarization of the transmitted light signal Lt. Otherwise, the construction of the semiconductor module 2 in FIG. 4 corresponds to that in FIG. 4.

[0053] FIG. 6 shows a schematic illustration of a sixth embodiment of a semiconductor module 2. The optical transmitting and receiving unit 32 takes the form of a camera, wherein the detection unit 36 of the camera has a two-dimensional detector array for determining a two-dimensional current density distribution 56. For this purpose, a magneto-optical sensor 28 having a large-surface magneto-optical layer 28 is used. A polarized light signal Lp, generated by a light source 34 facing the camera, is guided by way of a polarizer 54 to the large-surface magneto-optical sensor 28. The light signal Lr that is reflected by the magneto-optical sensor 28 is reflected back to the camera by way of the polarizer 54. A current is determined in the evaluation unit 40, from a polarization of the reflected light signal Lr.

[0054] In order to detect a transient current signal St that has an amplitude dynamic of at least 100 and a rise time in the region of at most 10 ?m, undersampling is performed, triggered by a frequency converter clock signal Ut having a frequency ft and generated by a signal generator 58. For the undersampling, a delay element 60 subjects the frequency converter dock signal Ut to a defined delay ?t smaller than 1/ft. Otherwise, the construction of the semiconductor module 2 in FIG. 6 corresponds to that in FIG. 1.

[0055] FIG. 7 shows an enlarged schematic illustration of a magneto-optical sensor 28 which comprises a first magneto-optical material 62 and a second magneto-optical material 64 that differs from the first magneto-optical material 62 in respect of sensitivity to field strength. As illustrated in FIG. 1, the magneto-optical sensor 28 is connected to an optical transmitting and receiving unit 32 by way of a fiber-optic conductor 30. The at least two magneto-optical materials 62, 64 can be used for different field strengths, with the result that it is possible to achieve a greater measurement dynamic.

[0056] FIG. 8 shows a schematic illustration of a power converter 66 having a semiconductor module 2. The power converter 66 may comprise more than one semiconductor module 2.

[0057] To summarize, the invention relates to a method for monitoring at least one semiconductor element 4 in a semiconductor module 2, wherein the semiconductor module 2 has feed lines 20, 22 for making contact with the semiconductor element 4. In order to be able to detect dynamic, in particular transient, events without significantly affecting the at least one semiconductor element 4 and its peripheral equipment, it is proposed that a magneto-optical sensor 28 be arranged in the region of the semiconductor element 4 or at least one feed line 20, 22, wherein a polarized light signal Lp is reflected by the magneto-optical sensor 28, wherein a current is determined from a polarization of the reflected light signal Lr.