Thermal resistance measurement method

Abstract

To provide a thermal resistance measurement method capable of improving measurement accuracy of thermal resistance.SOLUTION: The thermal resistance measurement method includes the steps of: applying first current between main electrodes to cause a semiconductor element to generate heat, and measuring voltage between the main electrodes (S50); applying second current smaller than the first current between the main electrodes in a period before the application of first current, and measuring voltage between the main electrodes at first timing (S40); applying third current smaller than the first current between the main electrodes in a period after the application of the first current, and measuring voltage between the main electrodes and current flowing between the main electrodes at second timing (S60); using preset current coefficient and current flowing between the main electrodes at the second timing to correct difference voltage (S70); using the corrected difference voltage and preset temperature coefficient to calculate temperature difference before and after application of the first current (S80); and using the temperature difference and application power for causing the semiconductor element to generate heat to calculate thermal resistance (S90).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The disclosure in this specification relates to a method for measuring thermal resistance.

Background Art

[0002] Patent Document 1 discloses a method for measuring thermal resistance. The description of the prior art document is incorporated by reference as an explanation of the technical elements in this specification.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A method is known in which a large current is applied between the main electrodes of a semiconductor element to heat the semiconductor element included in a semiconductor device, and the temperature difference before and after the application of the large current is calculated using a physical property value indicating temperature characteristics to measure the thermal resistance. In this method, since the temperature drops if measurement is not performed immediately after the application of the large current, it is required to perform measurement immediately after the application of the large current, for example, within 500 μs.

[0005] However, at the timing immediately after the application of the large current, there is a risk that the physical property value changes due to the influence of the residual current flowing through the wiring during the application of the large current, and the measurement accuracy of the thermal resistance decreases. From the above viewpoints, or from other viewpoints not mentioned, further improvement is required for the method for measuring thermal resistance.

[0006] One object of the present disclosure is to provide a method for measuring thermal resistance that can improve the measurement accuracy of thermal resistance.

Means for Solving the Problems

[0007] One aspect of the disclosure is a thermal resistance measurement method for measuring the thermal resistance of a semiconductor device including a semiconductor element, comprising: applying a first current between main electrodes of the semiconductor element to generate heat in the semiconductor element and measuring the voltage between the main electrodes (step S50); applying a second current smaller than the first current between the main electrodes during a predetermined pre-application period until the first current is applied, and measuring the voltage between the main electrodes at a first timing during the pre-application period (step S40); applying a third current smaller than the first current between the main electrodes during a predetermined post-application period after the first current is applied, and measuring the voltage between the main electrodes and the current flowing between the main electrodes at a second timing during the post-application period (step S60); correcting a differential voltage, which is the difference between the voltage between the main electrodes at the first timing and the voltage between the main electrodes at the second timing, using a preset current coefficient and the current flowing between the main electrodes at the second timing (steps S70, S70A); calculating a temperature difference of the semiconductor element before and after the application of the first current using the corrected differential voltage and a preset temperature coefficient (step S80); calculating the thermal resistance using the temperature difference and the applied power for generating heat in the semiconductor element (step S90); wherein the current coefficient indicates a rate of change of the voltage between the main electrodes with respect to the current flowing between the main electrodes.

[0008] According to the thermal resistance measurement method of the disclosure, the difference in voltage (differential voltage) before and after the application of the first current is corrected using a preset current coefficient and the current measured at the second timing. Thereby, the influence of the residual current can be corrected. Therefore, the measurement accuracy of the temperature difference, and thus the thermal resistance, can be improved.

[0009] The multiple aspects disclosed in this specification adopt different technical means to achieve their respective purposes. The claims and the reference numerals in parentheses described in this column exemplarily show the correspondence with the parts of the embodiments described later, and are not intended to limit the technical scope. The purposes, features, and effects disclosed in this specification will become clearer by referring to the subsequent detailed description and the attached drawings.

Brief Description of the Drawings

[0010]

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Modes for Carrying Out the Invention

[0011] Hereinafter, a plurality of embodiments will be described with reference to the drawings. In each embodiment, corresponding components may be denoted by the same reference numerals, and redundant descriptions may be omitted. When only a part of the configuration is described in each embodiment, the configuration of other embodiments described previously can be applied to other parts of the said configuration. Also, not only the combinations of configurations explicitly shown in the description of each embodiment, but also the configurations of a plurality of embodiments can be partially combined with each other as long as there is no problem with the combination, even if not explicitly stated.

[0012] (First Embodiment) First, based on FIGS. 1 and 2, the schematic configuration of a measurement system for measuring the thermal resistance of a semiconductor device will be described.

[0013] <Measurement System> FIG. 1 shows the schematic configuration of the measurement system. FIG. 2 shows an equivalent circuit in a state where a semiconductor device is set in the measurement system. The measurement system 10 shown in FIG. 1 is configured to be able to perform thermal resistance measurement on a semiconductor device 100 that is the measurement target.

[0014] The semiconductor device 100 includes a semiconductor element 101 as shown in FIG. 2. The semiconductor element 101 is formed by forming a switching element having a gate on a semiconductor substrate made of silicon (Si), a wide-bandgap semiconductor having a wider bandgap than silicon, or the like. Examples of the wide-bandgap semiconductor include silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga 2 O 3 ), diamond, and the like. The semiconductor element 101 may be referred to as a power element, a semiconductor chip, or the like.

[0015] The switching element may be configured to allow a main current to flow in the thickness direction of, for example, the semiconductor element 101 (semiconductor substrate). Such a switching element may be referred to as a vertical element. The vertical element has main electrodes on both surfaces in the thickness direction. As an example, the semiconductor element 101 of the present embodiment is formed by forming an n-channel MOSFET 102 on a semiconductor substrate made of SiC. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. The semiconductor element 101 has a diode 103 connected in anti-parallel to the MOSFET 102. The diode 103 is a parasitic diode of the MOSFET 102. The semiconductor element 101 has, as main electrodes, a first main electrode that functions as a source electrode and an anode electrode, and a second main electrode that functions as a drain electrode and a cathode electrode.

[0016] The semiconductor element having a diode connected in anti-parallel is not limited to the example shown in FIG. 2. For example, a semiconductor element having an IGBT and a diode connected in anti-parallel to the IGBT, that is, an RC-IGBT, may be used. The RC-IGBT is formed, for example, on a semiconductor substrate made of silicon (Si). IGBT is an abbreviation for Insulated Gate Bipolar Transistor. RC is an abbreviation for Reverse Conducting. In the case of an RC-IGBT, the semiconductor element has, as main electrodes, a first main electrode that functions as an emitter electrode and an anode electrode, and a second main electrode that functions as a collector electrode and a cathode electrode.

[0017] The semiconductor device 100 is a semiconductor package including the semiconductor element 101. The semiconductor device 100 may sometimes be referred to as a semiconductor module or the like. The semiconductor device 100 may include, together with the semiconductor element 101, for example, a wiring member, an external connection terminal, a sealing body, and the like. The semiconductor device 100 may provide at least one arm of the upper and lower arm circuits constituting a power conversion circuit such as an inverter. As an example, the semiconductor device 100 of the present embodiment is a power card having a so-called 1in1 package structure.

[0018] The semiconductor device 100 includes, as external connection terminals, a first main terminal M1, a second main terminal M2, and a gate terminal G1. The first main terminal M1 is electrically connected to the above-described first main electrode (source electrode, anode electrode). The second main terminal M2 is electrically connected to the second main electrode (drain electrode, cathode electrode). The gate terminal G1 is electrically connected to the gate electrode of the MOSFET 102.

[0019] As shown in FIGS. 1 and 2, the measurement system 10 includes a measurement device 20, a control device 30, and a display device 40. The measurement device 20 includes an M power supply 21, an S power supply 22, and a G power supply 23. As an example, each of the M power supply 21, the S power supply 22, and the G power supply 23 in the present embodiment is configured to be able to apply both current and voltage. Each of the M power supply 21, the S power supply 22, and the G power supply 23 also has a function as a measuring instrument and is configured to be able to measure both current and voltage. A configuration in which the power supply function and the measurement function of the measurement device 20 are separated may also be employed.

[0020] The M power supply 21 applies a current between the main electrodes of the semiconductor element 101. The M power supply 21 is provided between the first main terminal M1 and the second main terminal M2. The M power supply 21 can apply a large current, for example, a current up to 100 A. The M power supply 21 measures the voltage between the main electrodes, for example, in a state where a current is applied by the M power supply 21.

[0021] The S power supply 22 applies a current between the main electrodes of the semiconductor element 101. The S power supply 22 is provided between the first main terminal M1 and the second main terminal M2. The S power supply 22 applies a current smaller than the current applied by the M power supply 21. The S power supply 22 can apply a small current, for example, a current up to 0.5 A. The S power supply 22 measures the voltage between the main electrodes, for example, in a state where a current is applied by the S power supply 22. The S power supply 22 measures the current flowing between the main electrodes, for example, in a state where a current is applied by the S power supply 22.

[0022] The G power supply 23 applies a voltage to the gate of the MOSFET 102 included in the semiconductor element 101. The G power supply 23 is electrically connected to the gate terminal G1 and the first main terminal M1. The G power supply 23 can apply a voltage up to, for example, 25V. The G power supply 23 is provided between the gate terminal G1 and the first main terminal M1.

[0023] The control device 30 controls the driving of the M power supply 21, the S power supply 22, and the G power supply 23 so as to execute the thermal resistance measurement. The control device 30 includes, for example, a processor, a memory, and a storage. The processor is, for example, a CPU. The CPU is an abbreviation for Central Processing Unit. The processor executes various processes for realizing functions by accessing the memory. The memory is a volatile storage medium, for example, a RAM. The RAM is an abbreviation for Random Access Memory. The storage is configured to include a non-volatile storage medium such as a flash memory. A control program executed by the processor is stored in the storage. The processor executing the control program corresponds to the execution of the method corresponding to the control program.

[0024] The display device 40 includes, for example, a display. The display device 40 displays the measurement result.

[0025] <Thermal Resistance Measurement Method> FIG. 3 shows an example of the thermal resistance measurement process executed by the processor, that is, the thermal resistance measurement method. In the present embodiment, the thermal resistance is measured using the heat generation of the diode 103 included in the semiconductor element 101. Hereinafter, the value of the current flowing in the forward direction of the diode 103 is indicated by a positive value.

[0026] As shown in FIG. 3, first, initialization is executed (step S10). In the initialization, a predetermined voltage is applied to the gate (between the gate and the source) of the MOSFET 102 by the G power supply 23 to discharge the charges accumulated in the gate oxide film. For example, +25V and -25V are applied for several tens of ms to several hundreds of ms each. The initialization may be executed as necessary. For example, in the case of an RC-IGBT, the initialization may be omitted.

[0027] Next, the Vf temperature coefficient is measured (step S20). The Vf temperature coefficient indicates the rate of change of the forward voltage Vf of the diode 103 with respect to temperature. The S power supply 22 applies a target value current flowing in the forward direction between the main electrodes of the diode 103, and measures the forward voltage Vf. The target value current is as low as possible so as not to cause self-heating in the diode 103, and is the minimum current at which the characteristics can be stably obtained. In the measurement of the Vf temperature coefficient, a predetermined voltage is applied to the gate, and the measurement is performed with the MOSFET 102 turned off. For temperature measurement, for example, a temperature-sensitive diode built in the semiconductor element 101 may be used. As an example, the target value current in this embodiment is 100 mA. Also, the voltage applied to the gate by the G power supply 23 is -3.5V.

[0028] FIG. 4 shows an example of the measurement of the Vf temperature coefficient. The temperature characteristics of the forward voltage Vf when the target value current is applied are measured, and the slope a obtained by linear approximation is defined as the Vf temperature coefficient (Vf-t). In the measurement of the Vf temperature coefficient, the lower limit of the temperature range is the room temperature of the measurement environment (for example, 25°C). The upper limit of the temperature range is the highest temperature (for example, 150°C) to which the semiconductor element 101 rises during the measurement of the thermal resistance. Then, the Vf temperature coefficient (slope a) is calculated using three or more data points including the temperature lower limit and the temperature upper limit, and the calculated Vf temperature coefficient is stored in the memory.

[0029] Next, the Vf current coefficient is measured (step S30). The Vf current coefficient indicates the rate of change of the forward voltage Vf with respect to the forward current If. While changing the current applied between the main electrodes by the S power supply 22, the forward voltage Vf is measured. Also in the measurement of the Vf current coefficient, for example, -3.5 V is applied to the gate, and the measurement is performed with the MOSFET 102 turned off.

[0030] FIG. 5 shows an example of the measurement of the Vf current coefficient. In the measurement of the Vf current coefficient, the lower limit of the current range is the target value (100 mA). The upper limit of the current range is the maximum value of the residual current at timing T2 described later. The maximum value of the residual current is about 1000 mA at 100 μs after, for example, the application of the current Im (first current) is cut off. The Vf current coefficient is calculated using three or more data points including the current lower limit and the current upper limit, preferably five or more data points.

[0031] From the obtained results of the Vf current coefficient, a fourth-order approximation is calculated by least-squares approximation. This fourth-order approximation formula may be stored in the memory as the Vf current coefficient. As an example, in the present embodiment, the correction coefficient α shown in the following mathematical formula 1 is stored in the memory. The correction coefficient α indicates the ratio to the target value current (100 mA). In mathematical formula 1, the denominator is the current coefficient when the current If2 is obtained at timing T2, and the numerator is the current coefficient when the target value is 100 mA.

Equation

[0032] The above steps S10, S20, and S30 are pre-preparation steps. The execution order of steps S20 and S30 is not particularly limited. The measurement of the Vf current coefficient may be performed before the measurement of the Vf temperature coefficient.

[0033] After performing the preparatory steps, execute the thermal resistance measurement process. FIG. 6 shows the waveform of the gate voltage Vg (Vgs) to be applied. FIG. 7 shows the waveform of the current to be applied. FIG. 8 shows the waveform of the voltage measured when the current is applied. FIG. 9 is an enlarged view of the region IX enclosed by the dashed-dotted line in FIG. 7. FIG. 10 is an enlarged view of the region X enclosed by the dashed-dotted line in FIG. 8. As shown in FIG. 6, apply a gate voltage Vg1 = -3.5 V as the gate voltage. That is, perform the thermal resistance measurement with the MOSFET 102 turned off. Pw1, Pw2, and Pw3 indicate the time from the start of the first period, that is, the time from the start of the thermal resistance measurement process.

[0034] First, apply a current Is flowing in the forward direction of the diode 103 by the S power supply 22 in the first period set by Pw1, and measure the forward voltage Vf1 at a predetermined timing T1 in the first period (step S40). The first period corresponds to the pre-application period before applying a large current. The current Is applied in the first period corresponds to the second current. The timing T1 corresponds to the first timing. Pw1 is set to the time when a small current (current Is) is applied by the S power supply 22 and the Vf characteristic is stably output. The current Is is the target value current described above. The timing T1 is the timing for acquiring the forward voltage Vf1 and is set at the end of Pw1 or in the vicinity thereof. As an example, in this embodiment, Pw1 is 1 ms, the current Is is 100 mA, and the timing T1 is 1 ms. The first period is the period from 0 ms to 1 ms.

[0035] Next, in order to heat the diode 103, apply a current Im flowing in the forward direction of the diode 103 by the M power supply 21 in the second period, and measure the forward voltage Vf (step S50). The second period is a period following the first period and is the period obtained by subtracting Pw1 from Pw2. Pw2 is set to the maximum time that can be applied with the power supply capacity. The current Im is set to the maximum value that can be applied with the power supply capacity and does not exceed the absolute rating of the semiconductor device 100. As an example, in this embodiment, Pw2 is 36 ms and the current Im is 50 A. The second period is the period from 1 ms to 36 ms.

[0036] In step S50, the applied power for heating the diode 103, that is, the diode loss due to the application of a large current (current Im), is calculated. The applied power W can be calculated by the following formula 2. The applied power W is the average value of the product of the current and the voltage in the hatched section shown in FIGS. 7 and 8.

Equation

[0037] Next, in the third period, a current Is flowing in the forward direction of the diode 103 is applied by the S power supply 22, and the forward voltage Vf2 and the current If2 at a predetermined timing T2 in the third period are measured (step S60). The third period is a period following the second period and is a period obtained by subtracting Pw2 from Pw3. The third period corresponds to the post-application period after applying a large current. The current Is applied in the third period corresponds to the third current. The timing T2 corresponds to the second timing. The timing T2 is set within the time affected by the residual current. The current Is (third current) in the third period may be the same value as the current Is (second current) in the first period or a different value. As an example, in the present embodiment, the current Is applied in the first period and the current Is applied in the third period are the same value. That is, the current Is is set to 100 mA. Also, Pw3 is set to 37 ms and the timing T2 is set to 36.1 ms. The third period is a period from 36 ms to 37 ms. The timing T2 is set 100 μs after the cutoff of the current Im.

[0038] As shown in FIGS. 7 and 9, within 500 μs after the application of the current Im (large current) is interrupted, the residual current during the large current application flows through the wiring. The current If2 obtained at timing T2 shows a value larger than the current Is (target current) by the amount of the residual current. The forward voltage Vf of the diode 103 has a negative temperature characteristic. For this reason, when the temperature of the semiconductor element 101 rises, the forward voltage Vf decreases. However, when the current If2 shifts upward due to the influence of the residual current as described above, the corresponding forward voltage Vf2 also rises as shown in FIGS. 8 and 10. Thus, the forward voltage Vf2 immediately after the application of the large current shifts upward in value due to the influence of the residual current.

[0039] Therefore, following step S60, a differential voltage ΔVf, which is the difference between the forward voltage Vf1 at timing T1 and the forward voltage Vf2 at timing T2, is corrected using a preset current coefficient and the current If2 at timing T2 (step S70). Then, using the corrected differential voltage ΔVf and a preset temperature coefficient, the temperature difference ΔT of the semiconductor element 101 before and after the application of the current Im is calculated (step S80).

[0040] The temperature difference ΔT can be calculated by the following Equation 3. The numerator on the right side of Equation 3 indicates the differential voltage ΔVf. The correction coefficient α is obtained by inputting the value of the current If2 acquired at timing T2 into Equation 1. By correcting the forward voltage Vf2 affected by the residual current with the correction coefficient α, a differential voltage ΔVf with the shift due to the residual current corrected is obtained. The denominator is the Vf temperature coefficient (Vf-t). By dividing the corrected differential voltage ΔVf by the Vf temperature coefficient, the temperature difference ΔT can be obtained.

Equation

[0041] Next, using the temperature difference ΔT and the applied power W for heating the semiconductor element 101, the thermal resistance Rth is calculated (step S90). The thermal resistance Rth (K / W) can be calculated by the following Equation 4. The thermal resistance Rth can be obtained by dividing the temperature difference ΔT by the applied power W.

Number

[0042] Note that the current Is (100 mA) is sufficiently smaller than the current Im (50 A). Therefore, the current Is may be applied from the beginning of the first period until the end of the third period, and the current Im may be applied in the second period. That is, the current Im may be superimposed on the current Is. Alternatively, only the current Is may be applied in the first and third periods, and only the current Im may be applied in the second period. That is, the application of the current Is and the application of the current Im may be switched.

[0043] Since it is before the application of the large current, there is no deviation in the current If1 due to the residual current. However, if the value of the current If1 increases due to the influence of wiring or the like, the forward voltage Vf1 may be corrected by the current coefficient. For example, the numerator on the right side of Equation 3 may be set to (Vf1 - Vf2) * α.

[0044] <Summary of the First Embodiment> A method is known in which a large current is applied between the main electrodes of a semiconductor element, and the temperature difference before and after the application of the large current is calculated using a physical property value indicating temperature characteristics, and the thermal resistance is measured. In this method, since the temperature drops if the measurement is not performed immediately after the application of the large current, it is required to perform the measurement immediately after the application of the large current, for example, within 500 μs. However, at the timing immediately after the application of the large current, the physical property value changes due to the influence of the residual current flowing through the wiring during the application of the large current, and there is a risk that the measurement accuracy of the thermal resistance decreases. For example, when the forward voltage of a diode is used as the physical property value, although the forward voltage decreases due to the temperature rise, the forward voltage increases due to the influence of the residual current. Thus, due to the influence of the residual current, the value of the forward voltage increases, so that the difference in the forward voltage before and after the application of the large current, that is, the temperature difference, is apparently underestimated.

[0045] According to this embodiment, the difference ΔVf in the forward voltage before and after the application of the current Im (first current) is corrected using a preset current coefficient and the current If2 measured at the timing T2 (second timing) immediately after the application of the current Im. Thereby, the influence of the residual current can be corrected. Therefore, the measurement accuracy of the temperature difference, and thus the thermal resistance, can be improved.

[0046] As exemplified in this embodiment, as a preliminary preparation step, a step of measuring the temperature coefficient and a step of measuring the current coefficient may be provided. Following (continuously) the preliminary preparation step, in order to execute the thermal resistance measurement step, the measurement accuracy of the thermal resistance can be further improved.

[0047] As exemplified in this embodiment, the semiconductor element 101 may have a MOSFET 102 which is a switching element and a diode 103 connected in anti-parallel to the MOSFET 102. Then, the differential voltage may be corrected using the forward current coefficient of the diode 103. The temperature difference may be calculated using the forward temperature coefficient of the diode 103. The forward voltages Vf1 and Vf2 of the diode 103 may be measured at the timings T1 and T2. When the on-resistance of the MOSFET is small, such as in the case of a SiC-MOSFET, the thermal resistance can be efficiently measured by utilizing the heat generation of the diode.

[0048] <Modification Example> An example of executing the thermal resistance measurement step following the preliminary preparation step has been shown, but it is not limited thereto. For example, as shown in FIG. 11, only the thermal resistance measurement step may be executed. That is, the preliminary preparation step and the thermal resistance measurement step may be executed separately on the time axis. For example, the preliminary preparation step may be performed a predetermined number of days before performing the thermal resistance measurement step, and the Vf temperature coefficient and the Vf current coefficient (correction coefficient α) may be stored in the memory. Whether the preliminary preparation step and the thermal resistance measurement step are performed continuously or separately, the differential voltage ΔVf is corrected using the Vf current coefficient (correction coefficient α) stored in the memory. Also, the temperature difference ΔT is calculated using the Vf temperature coefficient stored in the memory.

[0049] (Second Embodiment) This embodiment is a modified example based on the preceding embodiment, and the description of the preceding embodiment can be incorporated by reference. In the preceding embodiment, the heat generation of the diode was used to measure the thermal resistance. Instead, the heat generation of the MOSFET may be used.

[0050] FIG. 12 shows an example of the thermal resistance measurement method according to this embodiment. The configuration of the measurement system 10 is the same as that of the preceding embodiment. Even when using the heat generation of the MOSFET 102, the basic flow is the same as that in the case of the diode 103. Hereinafter, the value of the current flowing in the forward direction of the MOSFET 102, that is, the direction opposite to the forward direction of the diode 103, is indicated by a negative value.

[0051] As shown in FIG. 12, first, initialization is executed in the same manner as in the preceding embodiment (step S10). Next, the Von temperature coefficient is measured (step S20A). The Von temperature coefficient indicates the rate of change of the on-voltage Von of the MOSFET 102 with respect to temperature. A target current value is applied between the main electrodes by the S power supply 22, and the on-voltage Von is measured. As an example, the target current value in this embodiment is -100 mA. The temperature characteristics of the on-voltage Von when the target current value is applied are measured, and the slope obtained by linear approximation is stored in the memory as the Von temperature coefficient.

[0052] Next, the Von current coefficient is measured (step S30A). The Von current coefficient indicates the rate of change of the on-voltage Von with respect to the current Id (drain current) flowing in the forward direction of the MOSFEFT 102. The on-voltage Von is measured while changing the current applied between the main electrodes by the S power supply 22. Similar to the preceding embodiment, a fourth-order approximation is calculated by least-squares approximation from the obtained results of the Von current coefficient. This fourth-order approximation formula may be stored in the memory as the Von current coefficient, or a correction coefficient similar to Equation 1 may be stored in the memory.

[0053] Next, in the first period, a current Is (the second current) flowing in the forward direction of the MOSFET 102 is applied by the S power supply 22, and the on-voltage Von1 at a predetermined timing T1 in the first period is measured (step S40). The current Is is the target value current (-100 mA) described above. The current Id1 at the timing T1 may be measured.

[0054] Next, in order to heat the MOSFET 102, a current Im flowing in the forward direction of the MOSFET 102 is applied by the M power supply 21 in the second period, and the on-voltage Von is measured (step S50). As an example, in this embodiment, the current Im is set to -50 A. In step S50, the applied power W for heating the MOSFET 102, that is, the loss of the MOSFET due to the application of a large current (current Im) is calculated.

[0055] Next, in the third period, a current Is flowing in the forward direction of the MOSFET 102 is applied by the S power supply 22, and the on-voltage Von2 and the current Id2 at a predetermined timing T2 in the third period are measured (step S60). The current Is (the third current) in the third period may be the same value as the current Is (the second current) in the first period or a different value. As an example, in this embodiment, it is the same value as the current Is in the first period. That is, the current Is is set to -100 mA.

[0056] Next, using the preset current coefficient and the current Id2 at the timing T2, the differential voltage ΔVon, which is the difference between the on-voltage Von1 at the timing T1 and the on-voltage Von2 at the timing T2, is corrected (step S70A). Then, using the corrected differential voltage ΔVon and the preset temperature coefficient, the temperature difference ΔT of the semiconductor element 101 before and after the application of the current Im is calculated (step S80). Next, using the temperature difference ΔT and the applied power W for heating the semiconductor element 101, the thermal resistance Rth is calculated (step S90). Other configurations are the same as those described in the previous embodiment.

[0057] <Summary of the Second Embodiment> As exemplified in this embodiment, in a configuration where the semiconductor element 101 includes a MOSFET 102, the differential voltage ΔVon may be corrected using the forward current coefficient of the MOSFET 102. The temperature difference ΔT may be calculated using the forward temperature coefficient of the MOSFET 102. At timings T1 and T2, the forward voltage (on-voltage Von) of the MOSFET 102 may be measured. Using a preset current coefficient and the current Id2 measured at the timing T2 (second timing) immediately after the application of the current Im, the difference ΔVon in the on-voltage Von before and after the application of the current Im (first current) is corrected. Thereby, the influence of the residual current can be corrected. Therefore, the measurement accuracy of the temperature difference, and thus the thermal resistance, can be improved.

[0058] Although an example in which the thermal resistance measurement step is executed following the preliminary preparation step has been shown, the present invention is not limited thereto. As shown in FIG. 11, the preliminary preparation step and the thermal resistance measurement step may be executed separately.

[0059] <Modification Example> The configuration using the heat generation of the MOSFET 102 is not limited to the above example. For example, a current may be applied in the forward direction of the MOSFET 102 only during the second period of step S50, and a current may be applied in the forward direction of the diode 103 otherwise. That is, the MOSFET 102 may be used only for heat generation, and the diode 103 may be used for calculating the temperature difference and the like. Specifically, in the thermal resistance measurement method shown in FIG. 3, the gate voltage during the second period of step S50 may be set to about 10 V, for example, and a current Im (-50 A) may be applied between the main electrodes from the M power supply 21. The other steps are as described in the previous embodiment.

[0060] (Other Embodiments) The disclosure in this specification, drawings, etc. is not limited to the illustrated embodiments. The disclosure includes the illustrated embodiments and modifications by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of parts and / or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes those in which parts and / or elements of the embodiments are omitted. The disclosure includes the replacement or combination of parts and / or elements between one embodiment and another. The disclosed technical scope is not limited to the description of the embodiments. Some of the disclosed technical scopes should be understood to be indicated by the description of the claims and to include all changes within the meaning and scope equivalent to the description of the claims.

[0061] The disclosure in the specification, drawings, etc. is not limited by the description of the claims. The disclosure in the specification, drawings, etc. includes the technical idea described in the claims and extends to more diverse and extensive technical ideas than the technical idea described in the claims. Therefore, various technical ideas can be extracted from the disclosure in the specification, drawings, etc. without being restricted by the description of the claims.

[0062] When an element or layer is referred to as being "on", "connected to", "attached to", or "coupled to" another element or layer, it may be directly on, connected to, attached to, or coupled to the other element or layer, and there may also be intervening elements or intervening layers. In contrast, when an element is referred to as being "directly on", "directly connected to", "directly attached to", or "directly coupled to" another element or layer, there are no intervening elements or intervening layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" vs. "directly between", "adjacent" vs. "directly adjacent", etc.). As used in this specification, the term "and / or" includes any combination and all combinations of one or more of the associated listed items. That is, the description of A and / or B means at least one of A and B.

[0063] Spatially relative terms such as "inside", "outside", "beneath", "below", "lower", "above", "upper", etc. are used herein to facilitate the description of the relationship of one element or feature to another element or feature as illustrated. Spatially relative terms can be intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the drawings. For example, if the device in the figure is turned over, an element described as "below" or "beneath" another element or feature will be oriented "above" the other element or feature. Thus, the term "below" can encompass both an orientation of above and below. The device may be oriented in other directions (rotated 90 degrees or other orientations), and the spatially relative descriptors used in this specification are to be interpreted accordingly.

[0064] Although an example in which the control device 30 includes a CPU as a processor has been shown, the present invention is not limited to this. An MPU, a GPU, a DFP, etc. may be adopted. MPU is an abbreviation for Micro-Processing Unit. GPU is an abbreviation for Graphics Processing Unit. DFP is an abbreviation for Data Flow Processor. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field-Programmable Gate Array.

[0065] Some or all of the functions provided by the processor may be realized by combining multiple types of arithmetic processing units. Some or all of the functions provided by the processor may be realized using an SoC, an ASIC, an FPGA, etc. SoC is an abbreviation for System on Chip. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field-Programmable Gate Array. Some or all of the functions provided by the processor may be realized using a hardware logic circuit.

[0066] The program may be stored in a computer-readable non-transitory tangible storage medium as instructions to be executed by a computer. As the storage medium for the program, an HDD, an SSD, a flash memory, etc. can be adopted. HDD is an abbreviation for Hard-disk Drive. SSD is an abbreviation for Solid State Drive.

Explanation of Reference Numerals

[0067] 10… Measurement system, 20… Measuring device, 21… M power supply, 22… S power supply, 23… G power supply, 30… Control device, 40… Display device, 100… Semiconductor device, 101… Semiconductor element, 102… MOSFET, 103… Diode, G1… Gate terminal, M1… First main terminal, M2… Second main terminal

Claims

1. A thermal resistance measurement method for measuring the thermal resistance of a semiconductor device (100) including a semiconductor element (101), comprising: applying a first current between main electrodes of the semiconductor element to heat the semiconductor element, and measuring a voltage between the main electrodes (step S50); applying a second current smaller than the first current between the main electrodes during a predetermined pre-application period until the first current is applied, and measuring a voltage between the main electrodes at a first timing during the pre-application period (step S40); applying a third current smaller than the first current between the main electrodes during a predetermined post-application period after the first current is applied, and measuring a voltage between the main electrodes and a current flowing between the main electrodes at a second timing during the post-application period (step S60); correcting a differential voltage, which is a difference between the voltage between the main electrodes at the first timing and the voltage between the main electrodes at the second timing, using a preset current coefficient and the current flowing between the main electrodes at the second timing (steps S70, S70A); calculating a temperature difference of the semiconductor element before and after the application of the first current using the corrected differential voltage and a preset temperature coefficient (step S80); calculating a thermal resistance using the temperature difference and an applied power for heating the semiconductor element (step S90); and wherein the current coefficient indicates a ratio of change in the voltage between the main electrodes with respect to the current flowing between the main electrodes.

2. As a pre-preparation step before applying the first current, the second current, and the third current, measuring the temperature coefficient (steps S20, S20A); measuring the current coefficient (steps S30, S30A); The thermal resistance measurement method according to claim 1, comprising:

3. The semiconductor element includes a switching element (102) and a diode (103) connected in anti-parallel to the switching element, the temperature coefficient is a forward temperature coefficient of the diode, the current coefficient is a forward current coefficient of the diode, and the voltage between the main electrodes is a forward voltage of the diode. The thermal resistance measurement method according to claim 1 or claim 2.

4. The semiconductor element has a MOSFET (102) as a switching element, the temperature coefficient is a forward temperature coefficient of the MOSFET, the current coefficient is a forward current coefficient of the MOSFET, The voltage between the main electrodes is a forward voltage of the MOSFET, the thermal resistance measurement method according to claim 1 or claim 2.

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