Measuring device, semiconductor wafer tester, and measuring method

Abstract

We provide measurement technology that enables measurements that are currently difficult to perform. [Solution] The measuring device of the present disclosure includes a simulation voltage waveform acquisition unit 313 that acquires a simulation voltage waveform corresponding to a transient response voltage waveform by simulation, a parameter correction unit 314 that corrects the values ​​of parameters included in the current-voltage model so that the transient response voltage waveform and the simulation voltage waveform match, and a current-voltage characteristic acquisition unit 315 that acquires the current-voltage characteristics of the object under test based on the corrected current-voltage model in which the parameter values ​​have been corrected by the parameter correction unit 314. The current-voltage characteristic acquisition unit 315 acquires a corrected simulation voltage waveform by performing simulation again based on the corrected current-voltage model, and if the error between the corrected simulation voltage waveform and the transient response voltage waveform is within an acceptable range, the corrected current-voltage model is considered to be the current-voltage characteristics of the object under test.

Description

Technical Field

[0001] The present disclosure relates to a measuring device, a semiconductor wafer tester, and a measuring method.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2016-48617 (Patent Document 1) describes a technique for selecting a model to be used for estimation, extracting data to be used for estimation, and then estimating a state value of a device to be estimated based on the selected model and the extracted data.

[0003] Japanese Translation of PCT International Publication No. 2014-522966 (Patent Document 2) describes a technique for performing a failure diagnosis of an insulation resistance measuring device by using a first diagnostic voltage, a second diagnostic voltage, and a circuit equation derived from a diagnostic circuit.

[0004] International Publication WO2019 / 146460 (Patent Document 3) describes a technique for performing a simulation using a device model.

[0005] Japanese Unexamined Patent Application Publication No. 2002-245107 (Patent Document 4) describes a technique related to a high-frequency measuring device having a function as a simulator.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] Current measurement is fundamental to electronics. Measuring large currents at high speeds is difficult due to factors such as the inductance of the measurement system, heat generation of the sensor, and integration circuits. In this regard, semiconductor devices are becoming faster and more energy-dense. Consequently, current measurement techniques are insufficient to address the current demands of current measurement in semiconductor devices.

[0008] For example, current curve tracers can only measure pulses of 100 μs or longer. In contrast, the short-circuit withstand capability of a SiC power MOSFET is 3 μs. Therefore, current curve tracers cannot evaluate SiC power MOSFETs.

[0009] Therefore, there is a need for measurement technologies that can enable measurements that are currently difficult to perform. [Means for solving the problem]

[0010] In one embodiment, the measuring device includes an input unit that inputs the transient response voltage waveform of the object under test included in the main circuit, and a simulation unit that performs a simulation based on the equivalent circuit of the main circuit and the current-voltage model of the object under test. The current-voltage model of the object under test is a function that outputs the current value flowing through the object under test when a voltage value applied to the object under test is input. The function includes one or more parameters as coefficients. The simulation unit includes a simulation voltage waveform acquisition unit that acquires a simulation voltage waveform corresponding to the transient response voltage waveform by simulation, a parameter modification unit that modifies the parameters included in the current-voltage model so that the transient response voltage waveform and the simulation voltage waveform match, and a current-voltage characteristic acquisition unit that acquires the current-voltage characteristics of the object under test based on the modified current-voltage model obtained by modifying the parameter values ​​in the parameter modification unit.

[0011] The current-voltage characteristic acquisition unit obtains a corrected simulated voltage waveform by performing a simulation again based on the corrected current-voltage model. If the error between the corrected simulated voltage waveform and the transient response voltage waveform is within an acceptable range, the corrected current-voltage model is considered to represent the current-voltage characteristics of the object under test.

[0012] In one embodiment, the semiconductor wafer tester comprises a main body and a probe head connected to the main body via a cable. The main body includes the measuring device described in the claim. The probe head includes a main circuit excluding the object to be measured.

[0013] In one embodiment, the measurement method comprises (a) inputting the transient response voltage waveform of the object to be measured included in the main circuit, and (b) performing a simulation based on the equivalent circuit of the main circuit and the current-voltage model of the object to be measured. The current-voltage model of the object to be measured is a function that takes an estimated voltage value applied to the object to be measured as input and outputs an estimated current value flowing through the object to be measured, and is a function that includes parameters. Step (b) includes (b1) obtaining a simulated voltage waveform corresponding to the transient response voltage waveform by simulation, (b2) modifying the parameters included in the current-voltage model so that the transient response voltage waveform and the simulated voltage waveform match, and (b3) obtaining the current-voltage characteristics of the object to be measured based on the modified current-voltage model obtained by modifying the parameter values ​​in the parameter modification unit.

[0014] (b3) Step (b3) involves obtaining a modified simulated voltage waveform by performing the simulation again based on the modified current-voltage model, and if the error between the modified simulated voltage waveform and the transient response voltage waveform is within an acceptable range, the modified current-voltage model is considered to be the current-voltage characteristic of the object under test. [Effects of the Invention]

[0015] According to one embodiment, it is possible to provide a measurement technology that enables measurements that are currently difficult to perform. [Brief explanation of the drawing]

[0016] [Figure 1] It is an equivalent circuit diagram of a measuring device for obtaining the current-voltage characteristics of a measurement object. [Figure 2] In the related art, it is a graph showing a transient response voltage waveform and simulation results measured with a 20 μs pulse at a speed close to the limit of existing measuring devices. [Figure 3] In the related art, it is a graph showing a transient response voltage waveform and simulation results measured with a pulse on the order of several μs. [Figure 4] It is a diagram showing the configuration of the measuring device in the embodiment. [Figure 5] It is a diagram showing the mounting configuration of the main circuit. [Figure 6] It is a diagram showing the mounting configuration of the main circuit. [Figure 7] It is a functional block diagram showing the configuration of the simulation device. [Figure 8] It is a circuit diagram showing an example of an equivalent circuit of the main circuit. [Figure 9] It is a flowchart for explaining the operation of the simulation device. [Figure 10] It is a diagram showing a transient response voltage waveform and a simulation voltage waveform. [Figure 11] It is a diagram showing current-voltage models with different parameters. [Figure 12] It is a diagram showing a voltage waveform. [Figure 13] It is a diagram showing the current-voltage model of the measurement object. [Figure 14] It is a functional block diagram showing the configuration of a simulation device having a calibration function for a MOSFET model and a passive element model. [Figure 15] It is a flowchart for explaining the calibration operation. [Figure 16] It is a diagram for explaining an example of the calibration of the MOSFET model. [Figure 17]Figure 8 shows a circuit diagram of the main circuit equivalent circuit, which includes a MOSFET, a gate driver, and a resistor with a known resistance value, representing a realistic closed loop. [Figure 18] This is a diagram illustrating the technical concept in the embodiment. [Figure 19] This diagram shows the implementation configuration of the main circuit. [Figure 20] This figure shows the configuration of a semiconductor wafer tester in an embodiment. [Figure 21] This is a diagram intended to illustrate the usefulness of the technical concept of this disclosure. [Modes for carrying out the invention]

[0017] In all the drawings illustrating the embodiments, the same reference numeral is used for identical components, and repeated explanations of them are omitted. Hatching may be used even in plan views to improve clarity.

[0018] <Consideration of improvements> Figure 1 is an equivalent circuit diagram of a measuring device for acquiring the current-voltage characteristics of a device under test (DUT). In Figure 1, the equivalent circuit includes a high-voltage power supply PS, a capacitor CAP, a MOSFET 100, a gate driver GD, and a device under test (DUT).

[0019] The high-voltage power supply PS and capacitor CAP are connected in parallel. Therefore, the voltage supplied from the high-voltage power supply PS is applied to capacitor CAP. MOSFET 100 and the device under test DUT are connected in series. The series-connected MOSFET 100 and device under test DUT are connected in parallel with capacitor CAP. A gate driver GD is connected to the gate of MOSFET 100. The gate driver GD is configured to control the switching operation of MOSFET 100.

[0020] First, the related technologies will be described. In this specification, "related technologies" refers to technologies that are not publicly known but have problems identified by the present inventors, and which are the prerequisites for this disclosure.

[0021] In the related technology, the transient response voltage waveform is acquired from the measuring device shown in the equivalent circuit of Figure 1, and the current-voltage characteristics of the object under test are obtained. In the related technology, a MOSFET model corresponding to MOSFET100 is used. A MOSFET model is a function that takes the gate voltage value and source-drain voltage value as input and outputs the source-drain current value.

[0022] Figure 2 is a graph showing the transient response voltage waveform and simulation results measured at a 20 μs pulse speed, which is close to the limit of existing measurement devices, in the related technology.

[0023] "V(GATE)" is the gate voltage of MOSFET100 measured from probe points P3 and P4 shown in Figure 1. "V(MOS)" is the source-drain voltage measured from probe points P1 and P2 shown in Figure 1. In Figure 2, "V(GATE)" and "V(MOS)" correspond to the measured transient response voltage waveforms.

[0024] "V(CAP)" is the voltage applied to capacitor CAP shown in Figure 1. As can be seen from Figure 1, the voltage applied to capacitor CAP is equal to the voltage supplied from the high-voltage power supply PS. The voltage supplied from the high-voltage power supply PS is known. Therefore, "V(CAP)" is also known. "V(CAP)-V(MOS)" indicates the voltage estimated to be applied to the device under test DUT. That is, as shown in Figure 1, MOSFET 100 and the device under test DUT are connected in series. The voltage applied across the series-connected MOSFET 100 and the device under test DUT is equal to the voltage applied across capacitor CAP ("V(CAP)"). Therefore, the estimated voltage applied to the device under test DUT is expressed as "V(CAP)-V(MOS)". On the other hand, "V(DUT)" is the true voltage applied to the device under test DUT. "V(DUT)" cannot be directly measured with actual measuring equipment. Therefore, in Figure 2, "V(DUT)" is obtained by simulation based on the equivalent circuit. This is because any point can be probed in the simulation.

[0025] "I(DUT)" is the current flowing through the device under test, DUT. "I(DUT)" can be obtained by using a MOSFET model. That is, as mentioned above, the MOSFET model is a function that takes the gate voltage value and source-drain voltage value as input and outputs the source-drain current value. Therefore, by inputting "V(GATE)" and "V(MOS)", which are obtained as transient response voltage waveforms, into the MOSFET model, the source-drain current is output from the MOSFET model. As can be seen from Figure 1, MOSFET100 and the device under test, DUT, are connected in series. For this reason, the source-drain current flowing through MOSFET100 is equal to the current flowing through the device under test, DUT.

[0026] Based on the above, the related technology can obtain the current flowing through the DUT under test ("I(DUT)") based on the measured transient response voltage waveforms of "V(GATE)" and "V(MOS)" and the MOSFET model. Furthermore, in the related technology, as shown in Figure 2, "V(CAP)-V(MOS)" and "V(DUT)" are almost identical. Therefore, in the related technology, the voltage applied to the DUT under test can be obtained from the difference between "V(GATE)" and "V(MOS)" without having to obtain "V(DUT)" through simulation. In other words, the related technology can accurately obtain the voltage applied to the DUT under test and the current flowing through the DUT under test by using the measured transient response voltage waveforms of "V(GATE)" and "V(MOS)" and the MOSFET model. As a result, the related technology can obtain highly accurate current-voltage characteristics of the DUT under test.

[0027] However, related technologies make it difficult to perform measurements at high speeds and high currents.

[0028] This point will be explained below.

[0029] For example, if the power supplied to the DUT under test is a high power of around 30kW, considering the short-circuit withstand capability of the DUT, the HALS width must be on the order of a few microseconds; otherwise, the DUT may be damaged. Therefore, when measuring with high power, high-speed measurement is necessary to prevent damage to the DUT.

[0030] Figure 3 is a graph showing the transient response voltage waveform measured with pulses on the order of several microseconds and the simulation results in the related technology.

[0031] As shown in Figure 3, "V(CAP)-V(MOS)" deviates from "V(DUT)". This is because, in high-speed measurements, the effect of distributed inductance included in the circuit cannot be ignored. In other words, in high-speed measurements where the effect of distributed inductance becomes apparent, "V(CAP)-V(MOS)" cannot be used as the voltage estimated to be applied to the DUT under test. In short, when related techniques are used in high-speed measurements, it becomes difficult to obtain accurate current-voltage characteristics of the DUT under test. To put it another way, related techniques using "V(GATE)" and "V(MOS)" and the MOSFET model do not take distributed inductance into consideration, and therefore cannot obtain accurate current-voltage characteristics of the DUT under test.

[0032] Therefore, we have implemented measures to obtain accurate current-voltage characteristics of the DUT (Device Under Test) even during high-speed measurements. The technical concept of this disclosure is explained below.

[0033] The technical concept of this disclosure utilizes not only transient response voltage waveforms and MOSFET models for "V(GATE)" and "V(MOS)," but also current-voltage models and passive component models for the DUT under test. In this respect, the technical concept of this disclosure differs from related technologies. Unlike related technologies, the technical concept of this disclosure performs simulations based on equivalent circuits.

[0034] <Basic philosophy> The basic principles include the following:

[0035] (1) The basic idea is to obtain the current-voltage characteristics of the object under test by measuring only the voltage, without measuring the current. Specifically, the basic idea is to obtain the current-voltage characteristics of the object under test by utilizing the transient response voltage waveform of the object under test.

[0036] (2) The basic idea is to inductively obtain the current-voltage characteristics of the object under test from simulations using an equivalent circuit. Specifically, the basic idea is to obtain a simulated voltage waveform corresponding to the transient response voltage waveform by simulating using the current-voltage model of the object under test. The basic idea is to modify the parameters of the current-voltage model of the object under test so that the simulated voltage waveform matches the actually measured transient response voltage waveform. The modified simulated voltage waveform obtained by performing a simulation again based on the modified current-voltage model is compared with the transient response voltage waveform. If the error between the modified simulated voltage waveform and the transient response voltage waveform is within an acceptable range as a result of the comparison, the modified current-voltage model is taken as the current-voltage characteristics of the object under test. In other words, the basic idea is to obtain the current-voltage characteristics based on the reasonable assumption that a current-voltage model that produces a simulated voltage waveform that matches the transient response voltage waveform represents the true current-voltage characteristics of the object under test.

[0037] The current-voltage model of an object under test is a function that takes a voltage value applied to the object under test as input and outputs the current value flowing through the object under test; it is a function that includes parameters.

[0038] For example, if the current value is "I" and the voltage value is "V", the function is I = F(V). One example is I = F(V) = aV + bV. 2 If we add +..., then "a" and "b" are examples of parameters as coefficients.

[0039] (3) In the basic concept, the passive element model and the MOSFET model are considered in the equivalent circuit simulation. The MOSFET model is a function that takes the gate voltage value and source-drain voltage value as input and outputs the source-drain current value, and is a function that includes parameters. The passive element model is the specific characteristic value of a passive element. In the basic concept, for example, distributed inductance is considered as a passive element.

[0040] Based on the fundamental concept, it can provide measurement technology that enables measurements that are currently difficult to perform.

[0041] The following describes embodiments that embody the basic concept.

[0042] <Embodiment> <<Configuration of the measuring device>> Figure 4 shows the configuration of the measuring device 1 in the embodiment.

[0043] In Figure 4, the measuring device 1 includes a main circuit 10, a sensing unit 20, and a main body 30. The main circuit 10 includes the device under test (DUT) and a power control unit 11. The power control unit 11 includes a capacitor 12, a MOSFET 13, and a gate driver 14.

[0044] The sensing unit 20 includes a sensor 21. The main body 30 has a simulation device 31, a pulse generator 32, a high-voltage power supply 33, and a control unit 34.

[0045] The DUT (Device Under Test) is the object whose current-voltage characteristics are being measured.

[0046] The power control unit 11 is configured to supply power to the device under test (DUT). A current loop is formed between the device under test (DUT) and the power control unit 11. The capacitor 12 is electrically connected to the high-voltage power supply 33. The MOSFET 13 is electrically connected to the gate driver 14. The gate driver 14 is configured to control the switching operation of the MOSFET 13.

[0047] Sensor 21 is configured to receive the probe point voltage output from the probe point of the power control unit 11. Sensor 21 is configured to output a probe voltage signal. That is, when sensor 21 receives a probe point voltage, it is configured to output a transient response voltage waveform composed of the probe voltage signal.

[0048] The simulation device 31 is electrically connected to the sensor 21. The simulation device 31 is configured to receive a transient response voltage waveform as input. The simulation device 31 is configured to perform a simulation to obtain the current-voltage characteristics of the DUT under test based on the transient response voltage waveform. The simulation device 31 is configured to output the current-voltage characteristics of the DUT under test based on the simulation. The detailed configuration of the simulation device 31 will be described later.

[0049] The control unit 34 is electrically connected to the pulse generator 32. The control unit 34 is electrically connected to the high-voltage power supply 33. The control unit 34 is configured to receive a voltage sweep range indicating the voltage range to be applied to the device under test (DUT). The control unit 34 is configured to control the pulse generator 32 and the high-voltage power supply 33 based on the voltage sweep range. The pulse generator 32 is electrically connected to the gate driver 14. The pulse generator 32 is configured to output a control signal to the gate driver 14. The high-voltage power supply 33 is electrically connected to the capacitor 12. The high-voltage power supply 33 is configured to supply a charging current to charge the capacitor 12.

[0050] The control unit 34 is configured to control the charging energy of the capacitor 12 so that it is less than the short-circuit withstand energy of the MOSFET 13.

[0051] <<Operation of the measuring device>> In Figure 4, when the voltage sweep range is input to the control unit 34, the control unit 34 outputs a control command to the pulse generator 32. Also, when the voltage sweep range is input to the control unit 34, the control unit 34 outputs a voltage command to the high-voltage power supply 33.

[0052] A control signal is output from the pulse generator 32, which receives a control command, to the gate driver 14. The gate driver 14, upon receiving the control signal, controls the switching operation of the MOSFET 13 based on the control signal. A charging current is supplied to the capacitor 12 from the high-voltage power supply 33, which receives a voltage command. As a result, the capacitor 12 is charged until its voltage is equal to the voltage of the high-voltage power supply 33. The capacitor 12, MOSFET 13, and the device under test (DUT) form a closed loop. The current flowing through the closed loop is controlled by the switching operation of the MOSFET 13.

[0053] When current is flowing within the closed loop, sensor 21 receives a probe point voltage from a probe point within the closed loop. Sensor 21, upon receiving the probe point voltage, outputs a transient response voltage waveform. Simulation device 31 receives the transient response voltage waveform as input. Based on the transient response voltage waveform, simulation device 31 performs a simulation to obtain the current-voltage characteristics of the DUT under test. Based on the simulation, simulation device 31 outputs the current-voltage characteristics of the DUT under test.

[0054] <<Main Circuit Implementation Configuration>> Figures 5 and 6 show the main circuit implementation configuration 2.

[0055] Implementation configuration 2 comprises the device under test (DUT), capacitor 12, MOSFET 13, gate driver 14, probe 15, and probe 16. Probe 15 is provided for measuring the source-drain voltage of MOSFET 13. Probe 16 is provided for measuring the gate voltage of MOSFET 13.

[0056] The source-drain voltage measured by probe 15 is input to sensor 21 shown in Figure 4. The gate voltage measured by probe 16 is also input to sensor 21.

[0057] <<Configuration of the simulation system>> Figure 7 is a functional block diagram showing the configuration of the simulation device 31.

[0058] In Figure 7, the simulation device 31 includes an input unit 311, a simulation unit 312, and a storage unit 317.

[0059] The input unit 311 is configured to receive the transient response voltage waveform of the object under test included in the main circuit. For example, the input unit 311 has the function of receiving the transient response voltage waveform output from the sensor 21 shown in Figure 4.

[0060] For example, the transient response voltage waveform is acquired from probe 15 or probe 16 provided in the main circuit implementation configuration 2 shown in Figures 5 and 6. Specifically, probe 15 measures the source-drain voltage of MOSFET 13. Probe 16 measures the gate voltage of MOSFET 13. The measured source-drain voltage and gate voltage are input to sensor 21 shown in Figure 4. The transient response voltage waveforms of the source-drain voltage and gate voltage are output from sensor 21. Therefore, the transient response voltage waveform in this embodiment is the waveform of the source-drain voltage and the waveform of the gate voltage.

[0061] The simulation unit 312 is configured to perform simulations based on the equivalent circuit of the main circuit and the current-voltage model of the object under test. The current-voltage model of the object under test is a function that takes a voltage value applied to the object under test as input and outputs a current value flowing through the object under test, and is a function that includes parameters.

[0062] The simulation unit 312 includes a simulation voltage waveform acquisition unit 313, a parameter correction unit 314, a current-voltage characteristic acquisition unit 315, and an output unit 316.

[0063] The simulation voltage waveform acquisition unit 313 is configured to acquire a simulation voltage waveform corresponding to the transient response voltage waveform through simulation.

[0064] The parameter modification unit 314 is configured to modify the values ​​of the parameters included in the current-voltage model so that the transient response voltage waveform and the simulated voltage waveform match.

[0065] The current-voltage characteristic acquisition unit 315 is configured to perform the simulation again based on the current-voltage model (referred to as the modified current-voltage model) whose parameter values ​​have been corrected by the parameter correction unit 314. The current-voltage characteristic acquisition unit 315 is configured to consider the modified current-voltage model as the current-voltage characteristic of the object under test if the error between the simulated voltage waveform (referred to as the modified simulated voltage waveform) obtained by performing the simulation and the transient response voltage waveform is within an acceptable range.

[0066] Furthermore, the current-voltage characteristic acquisition unit 315 is configured to repeatedly correct the parameter values ​​by the parameter correction unit 314 until the error between the corrected simulation voltage waveform and the transient response voltage waveform falls within the acceptable range.

[0067] The output unit 316 is configured to output a modified current-voltage model that is considered to be the current-voltage characteristic of the object under test by the current-voltage characteristic acquisition unit 315.

[0068] Figure 8 is a circuit diagram showing an example of the equivalent circuit of the main circuit.

[0069] As shown in Figure 8, the equivalent circuit includes a high-voltage power supply 33, a capacitor 12, a MOSFET 13, a gate driver 14, and the device under test (DUT). The simulation unit 312 is configured to perform simulations based on the equivalent circuit, current-voltage model, MOSFET model, and passive component model shown in Figure 8.

[0070] A MOSFET model is a function that takes a gate voltage and a source-drain voltage as inputs and outputs a source-drain current value, and includes parameters. A MOSFET model is, for example, a circuit simulation model or surrogate model consisting of a behavioral voltage-controlled power supply. A MOSFET model has input ports corresponding to the gate voltage, drain voltage, and at least one temperature.

[0071] A passive element model represents the specific characteristic values ​​of a passive element. For example, the equivalent circuit shown in Figure 8 includes distributed inductance. That is, the equivalent circuit is a circuit that takes distributed inductance into consideration. In the embodiment, a passive element model corresponding to distributed inductance is used. In other words, the passive element model includes the inductance value of the distributed inductance.

[0072] In the equivalent circuit shown in Figure 8, the difference between the voltage value at point P1 and the voltage value at point P2 corresponds to the source-drain voltage measured by probe 15 in Figure 5. In the equivalent circuit shown in Figure 8, the difference between the voltage value at point P3 and the voltage value at point P4 corresponds to the gate voltage measured by probe 16 in Figure 5. Therefore, the simulation voltage waveform acquisition unit 313 is configured to acquire a simulated voltage waveform of the source-drain voltage based on the difference between the voltage value at point P1 and the voltage value at point P2 in the equivalent circuit. The simulation voltage waveform acquisition unit 313 is configured to acquire a simulated voltage waveform of the gate voltage based on the difference between the voltage value at point P3 and the voltage value at point P4 in the equivalent circuit.

[0073] The memory unit 317 stores equivalent circuits, transient response voltage waveforms, simulated voltage waveforms, current-voltage models, MOSFET models, and passive element models, among others.

[0074] <<Operation of the simulation device>> Figure 9 is a flowchart illustrating the operation of the simulation device 31.

[0075] In Figure 9, first, the input unit 311 receives the transient response voltage waveform of the main circuit (S101). The input transient response voltage waveform is stored in the storage unit 317.

[0076] Next, the simulation device 31 sets up, for example, the equivalent circuit that has been pre-stored in the memory unit 317 (S102). The simulation device 31 also initializes the parameter values ​​of the current-voltage model (S103).

[0077] Next, the simulation unit 312 performs a simulation based on the equivalent circuit of the main circuit, the current-voltage model of the device under test, the MOSFET model, and the passive element model. Here, the MOSFET model and the passive element model are known.

[0078] Specifically, the simulation voltage waveform acquisition unit 313 acquires a simulation voltage waveform corresponding to the transient response voltage waveform by performing a simulation based on the equivalent circuit shown in Figure 8 (S104). The simulation voltage waveform is stored in the storage unit 317.

[0079] The current-voltage characteristic acquisition unit 315 then compares the transient response voltage waveform with the simulated voltage waveform (S105). If the error between the transient response voltage waveform and the simulated voltage waveform is within an acceptable range (S106), the current-voltage characteristic acquisition unit 315 determines that the current-voltage model used in the simulation is appropriate.

[0080] Subsequently, the output unit 316 outputs the current-voltage model that the current-voltage characteristic acquisition unit 315 has determined to be appropriate (S108).

[0081] On the other hand, if the error between the transient response voltage waveform and the simulated voltage waveform is not within the acceptable range (S106), the parameter correction unit 314 corrects the parameter values ​​of the current-voltage model (S107). Next, the simulation is performed using the current-voltage model with the corrected parameter values. The measuring device repeats the parameter correction by the parameter correction unit 314 until the error falls within the acceptable range (S104~S107). Finally, when the error between the transient response voltage waveform and the simulated voltage waveform falls within the acceptable range, the current-voltage characteristic acquisition unit 315 determines that the current-voltage model used in the simulation is appropriate. The current-voltage model determined to be appropriate by the current-voltage characteristic acquisition unit 315 is then output from the output unit 316. The final current-voltage model determined to be appropriate is also stored in the storage unit 317.

[0082] The operation of the simulation device 31 will be explained in an easy-to-understand manner using diagrams below.

[0083] Figure 10 shows the transient response voltage waveform and the simulated voltage waveform.

[0084] Figure 11 shows current-voltage models with different parameters.

[0085] In Figure 10, the thick line labeled "V(GATE)" represents the gate voltage waveform of MOSFET13 as measured. The thick line labeled "Measured Waveform" represents the source-drain voltage waveform of MOSFET13 as measured. In other words, "V(GATE)" and "Measured Waveform" represent transient response voltage waveforms obtained through actual measurements.

[0086] In Figure 10, "iter1", "iter2", "iter3", and "iter4" are simulation voltage waveforms acquired by the simulation voltage waveform acquisition unit 313. Each of "iter1", "iter2", "iter3", and "iter4" is a simulation voltage waveform obtained by simulating using current-voltage models and equivalent circuits with different parameter values.

[0087] The simulated voltage waveform "iter1" in Figure 10 was obtained using the current-voltage model shown in "iter1" in Figure 11. The simulated voltage waveform "iter2" in Figure 10 was obtained using the current-voltage model shown in "iter2" in Figure 11. The simulated voltage waveform "iter3" in Figure 10 was obtained using the current-voltage model shown in "iter3" in Figure 11. The simulated voltage waveform "iter4" in Figure 10 was obtained using the current-voltage model shown in "iter4" in Figure 11.

[0088] First, the current-voltage model with the initially set parameter values ​​is "iter1" in Figure 11. A simulation is performed using the current-voltage model "iter1" shown in Figure 11. As a result, the simulated voltage waveform for "iter1" shown in Figure 10 is obtained. Comparing "iter1" with the "measured waveform" in Figure 10, it can be seen that "iter1" deviates significantly from the "measured waveform".

[0089] Therefore, the parameter values ​​of the current-voltage model are corrected. As a result, the current-voltage model with the corrected parameter values ​​is "iter2" in Figure 11. The simulation is performed again using the current-voltage model "iter2" shown in Figure 11. As a result, the simulated voltage waveform for "iter2" shown in Figure 10 is obtained. Comparing "iter2" with the "measured waveform" in Figure 10, "iter2" deviates from the "measured waveform," although the deviation is smaller than that between "iter1" and the "measured waveform."

[0090] Therefore, the parameter values ​​of the current-voltage model are modified again. As a result, the current-voltage model with the modified parameter values ​​is "iter3" in Figure 11. The simulation is performed again using the current-voltage model "iter3" shown in Figure 11. As a result, the simulated voltage waveform for "iter3" shown in Figure 10 is obtained. Comparing "iter3" with the "measured waveform" in Figure 10, "iter3" deviates from the "measured waveform," although the deviation is smaller than that between "iter2" and the "measured waveform."

[0091] Furthermore, the parameter values ​​of the current-voltage model are modified again. As a result, the current-voltage model with the modified parameter values ​​is "iter4" in Figure 11. The simulation is performed again using the current-voltage model "iter4" shown in Figure 11. As a result, the simulated voltage waveform for "iter4" shown in Figure 10 is obtained. In Figure 10, "iter4" matches the "measured waveform".

[0092] In this way, a current-voltage model is obtained that produces a simulation waveform that matches the transient response voltage waveform. A current-voltage model that produces a simulation voltage waveform that matches the transient response voltage waveform is considered to represent the true current-voltage characteristics of the object under test. Therefore, according to this embodiment, the current-voltage characteristics of the object under test can be obtained with high accuracy.

[0093] <<Techniques for quickly obtaining the final current-voltage model>> 1.First improvement point Figure 12 shows a voltage waveform.

[0094] In Figure 12, "Waveform (1)" shows the transient response voltage waveform (source-drain voltage waveform) obtained by actually measuring using a probe.

[0095] "Waveform (2)" shows the simulated voltage waveform (source-drain voltage waveform) obtained from simulations based on the equivalent circuit, the current-voltage model of the device under test, the MOSFET model, and the passive element model.

[0096] "Waveform (3)" shows the voltage waveform (voltage waveform applied to the object under test) obtained from simulations based on the equivalent circuit, the current-voltage model of the object under test, the MOSFET model, and the passive element model.

[0097] As shown in Figure 12, when comparing "waveform (1)" and "waveform (2)", at times less than time T1, "waveform (2)" matches "waveform (1)". On the other hand, at times T1 and above, "waveform (2)" deviates from "waveform (1)".

[0098] Furthermore, as shown in "Waveform (3)," at times less than time T1, the voltage applied to the object under test is lower than the voltage value Verr. At time T1, the voltage applied to the object under test is the voltage value Verr. At times greater than time T1, the voltage applied to the object under test is higher than the voltage value Verr.

[0099] Figure 13 shows the current-voltage model of the object being measured.

[0100] In Figure 13, "Current-Voltage Model (A)" shows the current-voltage model used to obtain "Waveform (2)" shown in Figure 12. "Current-Voltage Model (A)" has a first current-voltage model A1 that corresponds to a voltage range smaller than the voltage value Verr, and a second current-voltage model A2 that corresponds to a voltage range greater than or equal to the voltage value Verr.

[0101] Here, the first current-voltage model A1 of "Current-Voltage Model (A)" is used to obtain the waveform corresponding to a time less than time T1 in "Waveform (2)" shown in Figure 12. As shown in Figure 12, the waveform corresponding to a time less than time T1 in "Waveform (2)" matches the waveform corresponding to a time less than time T1 in "Waveform (1)". Therefore, there is no need to modify the parameter values ​​of the first current-voltage model A1 of "Current-Voltage Model (A)".

[0102] In contrast, the second current-voltage model A2 of "Current-Voltage Model (A)" is used to acquire the waveform corresponding to time T1 and above in "Waveform (2)" shown in Figure 12. As shown in Figure 12, the waveform corresponding to time T1 and above in "Waveform (2)" is shifted from the waveform corresponding to time T1 and above in "Waveform (1)". Therefore, it is necessary to make the waveform corresponding to time T1 and above in "Waveform (2)" match the waveform corresponding to time T1 and above in "Waveform (1)". For this reason, it is necessary to modify the parameter values ​​of the second current-voltage model A2 of "Current-Voltage Model (A)". As a result, the second current-voltage model A2 of "Current-Voltage Model (A)" is modified to current-voltage model B, shown by the dotted line.

[0103] Based on the above, the technical concept behind the first point of innovation is as follows:

[0104] Compare the transient response voltage waveform with the simulated voltage waveform.

[0105] From these comparison results, the following conditions can be identified.

[0106] At time points shorter than the first time step, the error between the transient response voltage waveform and the simulated voltage waveform is within the acceptable range. At time points longer than or equal to the first time step, the error between the transient response voltage waveform and the simulated voltage waveform is outside the acceptable range.

[0107] At a time less than the first time point, the voltage applied to the object under test is lower than the first voltage value. At the first time point, the voltage applied to the object under test is the first voltage value. At a time greater than the first time point, the voltage applied to the object under test is higher than the first voltage value.

[0108] The current-voltage model is represented by the first current-voltage model in the voltage range below the first voltage value. The current-voltage model is represented by the second current-voltage model in the voltage range above the first voltage value.

[0109] Under these conditions, the first technique is to not modify the parameter values ​​of the first current-voltage model. On the other hand, the first technique is to modify the parameter values ​​of the current-voltage model so that the transient response voltage waveform matches the simulated voltage waveform.

[0110] Thus, in the first technique, the final current-voltage model can be obtained by modifying the parameter values ​​of the current-voltage model to the minimum necessary extent. Specifically, in the first technique, the parameter values ​​of the first current-voltage model A1 of "Current-Voltage Model (A)" are not modified. On the other hand, the parameter values ​​of the second current-voltage model of "Current-Voltage Model (A)" are modified. As a result, the time spent on modifying parameter values ​​can be reduced according to the first technique. In other words, the final current-voltage model can be obtained quickly according to the first technique.

[0111] 2.Second improvement point The technical concept behind the second point of innovation is as follows:

[0112] The measuring device stores the modified current-voltage model obtained from past simulations in association with the transient response voltage waveform. In other words, the measuring device stores a lookup table as a database that associates the transient response voltage waveform with the modified current-voltage model. For example, the lookup table is stored in the storage unit 317 in Figure 7.

[0113] For example, assume that there is a first corrected current-voltage model associated with a first transient response voltage waveform in a lookup table. In this case, when the first transient response voltage waveform is input to the input unit 311, the measurement device outputs, based on the lookup table, a first corrected current-voltage model corresponding to the first transient response voltage waveform input to the input unit 311 without performing a simulation. Thus, according to the second idea, the final current-voltage model (corrected current-voltage model) can be obtained at high speed without performing a simulation.

[0114] <<Measures to Improve the Accuracy of MOSFET Models and Passive Element Models>> The passive element model is a specific characteristic value of a passive element. For example, when the passive element is a resistance element, the passive element model is the specific resistance value of the resistance element. When the passive element is an inductor, the passive element model is the specific inductance value of the inductor.

[0115] The passive element model can be obtained from electromagnetic field analysis during design. However, the specific characteristic values of passive elements may vary from product to product depending on the process capabilities. Also, the characteristics of MOSFETs may vary from product to product. Therefore, in order to improve the accuracy of simulations using MOSFET models and passive element models, it is important to optimize the MOSFET models and passive element models for each product. Thus, in the embodiment, measures are taken to improve the accuracy of the MOSFET models and passive element models. Specifically, in the embodiment, a function for performing calibration of the MOSFET model and the passive element model is added to the simulation device in the measurement device.

[0116] FIG. 14 is a functional block diagram showing the configuration of a simulation device 31 having a calibration function for MOSFET models and passive element models.

[0117] In Figure 14, the simulation device 31 has a calibration unit 401. The calibration unit 401 has the function of correcting the MOSFET model and the passive element model. The calibration unit 401 includes a calibration voltage waveform acquisition unit 402 and a correction unit 403.

[0118] The calibration voltage waveform acquisition unit 402 is configured to acquire a calibration voltage waveform corresponding to the transient response voltage waveform by simulating a calibration sample having a known resistance value as the object to be measured.

[0119] The correction unit 403 is configured to correct the parameter values ​​of the MOSFET model and the passive element model so that the transient response voltage waveform and the calibration voltage waveform match.

[0120] Figure 15 is a flowchart illustrating the calibration process.

[0121] First, a calibration sample with a known resistance value is placed at the position of the object to be measured (S201). The input unit 311 receives the transient response voltage waveform of the main circuit where the calibration sample is placed (S202). The input transient response voltage waveform is stored in the storage unit 317.

[0122] Next, the simulation device 31 performs, for example, the setup of the equivalent circuit that has been pre-stored in the memory unit 317 (S202). Specifically, it sets the parameter values ​​of the MOSFET model and also sets the passive element model.

[0123] Next, the calibration voltage waveform acquisition unit 402 performs a simulation based on the equivalent circuit including the calibration sample, the MOSFET model, and the passive element model. Specifically, the calibration voltage waveform acquisition unit 402 acquires a calibration voltage waveform corresponding to the transient response voltage waveform by simulation based on the equivalent circuit (S204). The calibration voltage waveform is stored in the storage unit 317.

[0124] The correction unit 403 then compares the transient response voltage waveform with the calibration voltage waveform (S205). If the error between the transient response voltage waveform and the calibration voltage waveform is within an acceptable range (S206), the correction unit 403 determines that the MOSFET model and the passive element model with the set parameter values ​​are appropriate. Subsequently, the output unit 316 outputs the MOSFET model and passive element model that the correction unit 403 determined to be appropriate (S208).

[0125] On the other hand, if the error between the transient response voltage waveform and the calibration voltage waveform is not within the acceptable range (S206), the correction unit 403 corrects the parameter values ​​of the MOSFET model (S207). The correction unit 403 also corrects the passive element model.

[0126] Next, calibration is performed using the MOSFET model with the corrected parameter values ​​and the corrected passive element model. The measuring device repeatedly corrects the parameter values ​​of the MOSFET model and the passive element model by the correction unit 403 until the error falls within an acceptable range (S204~S207). Finally, when the error between the transient response voltage waveform and the calibration voltage waveform falls within an acceptable range, the correction unit 403 determines that the MOSFET model and passive element model whose errors are within an acceptable range are appropriate. The MOSFET model and passive element model determined to be appropriate by the correction unit 403 are then used in the simulation. The MOSFET model and passive element model determined to be appropriate by the correction unit 403 are stored in the storage unit 317.

[0127] Figure 16 illustrates an example of MOSFET model calibration.

[0128] In Figure 16, a calibration sample with a known resistance value is placed at the position of the object under test. However, here, multiple calibration samples with resistance values ​​ranging from 100 mΩ to 1 MΩ are used. The source-drain voltage of the MOSFET model is the voltage across the capacitor divided by the resistance value of the MOSFET model and the resistance value of the calibration sample. Here, the capacitor voltage and the resistance value of the calibration sample are known. Therefore, the source-drain voltage of the MOSFET model can be determined. The gate voltage corresponding to this source-drain voltage can then be obtained from Figure 16.

[0129] The resistance of the MOSFET model can be calculated by working backward from the voltage division. This allows the current flowing through the MOSFET model to be calculated as (source-drain voltage of the MOSFET model) / (resistance of the MOSFET model). This reveals the relationship between the input (source-drain voltage and gate voltage) and output (current) of the MOSFET model. As a result, according to this embodiment, calibration of the MOSFET model becomes possible without using a current sensor.

[0130] <<Techniques for measuring gate voltage with high precision>> For example, as can be seen from the equivalent circuit shown in Figure 8, MOSFET 13 and the device under test (DUT) are connected in series. Therefore, the current flowing through the device under test (DUT) is equal to the current flowing through MOSFET 13. Thus, the current flowing through the device under test (DUT) can be obtained from the current flowing through MOSFET 13. The current flowing through MOSFET 13 is related to the gate voltage of MOSFET 13. For example, when the current is small, the current flowing through MOSFET 13 is logarithmically related to the gate voltage. Therefore, the measurement error of the gate voltage exponentially affects the error of the measured current value. Specifically, the subthreshold slope, defined as the amount of change in gate voltage required for the current to increase tenfold, is generally about 0.3V / dec. From this, a measurement error of 0.3V in gate voltage results in a tenfold current error.

[0131] When the current is large, the current flowing through MOSFET13 is linearly linked to the gate voltage. Therefore, the current error is relatively small. In contrast, when the current is small, for the reasons mentioned above, precise measurement of the gate voltage is extremely important in order to reduce the current error.

[0132] Figure 17 is a schematic diagram showing a realistic closed loop of the equivalent circuit of the main circuit shown in Figure 8, including a MOSFET, a gate driver, and a resistor with a known resistance value.

[0133] In Figure 17, the gate voltage is measured by probe points M1 and M2. Since Figure 17 assumes a realistic closed loop, an inductance (L1) is included between the MOSFET gate and probe point M1. If only self-inductance is considered, there is almost no error in measuring the gate voltage. However, as shown in Figure 17, when an inductance (Laload) connected in series with the MOSFET is considered, the gate voltage measured by probe points M1 and M2 will have a large error compared to the true gate voltage at the timing when current flows through the main circuit. This is because the magnetic coupling between the inductance (L1) and the inductance (Laload) shown in Figure 17 generates an electromotive force V = MdI / dt (M: mutual inductance) in the closed loop.

[0134] This error increases with higher currents and higher speeds. In principle, it is difficult to completely eliminate this error when measuring the gate voltage with a probe.

[0135] Therefore, in this embodiment, measures are taken to measure the gate voltage with high precision.

[0136] Figure 18 illustrates the technical concept of the embodiment. In this embodiment, instead of directly measuring the gate voltage as shown in Figure 17, the voltage across a resistor with a known resistance value inserted in a closed loop is measured. Specifically, as shown in Figure 18, the voltage across the resistor (Rmeas) is measured by probe points M3 and M4.

[0137] The following explains how gate voltage can be measured with high accuracy by measuring the voltage across a resistor (Rmeas).

[0138] Let the gate-source capacitance of the MOSFET be "Cgs". In this case, the charge "Qgs" stored in the gate-source capacitance "Cgs" is expressed by (Equation 1).

[0139]

number

[0140] We transform (Equation 1) with respect to "Vgs". We also consider that "Qgs" is expressed as the integral of the gate-source current "Igs". This gives us (Equation 2).

[0141]

number

[0142] Next, the voltage across the resistor (Rmeas), "Vmeas," is expressed by (Equation 3).

[0143]

number

[0144] Therefore, as in the embodiment, measuring "Vmeas" automatically results in the measurement of "Igs". Substituting the measured "Igs" into (Equation 2) yields "Vgs". In other words, in the embodiment, the gate voltage (gate-source voltage) can be measured by measuring the voltage across a resistor with a known resistance value inserted in the closed loop, rather than directly measuring the gate voltage. The gate voltage measured in this way is less affected by the magnetic coupling between the inductance (L1) and the inductance (Laload) mentioned above, thus reducing the error.

[0145] The technical concept described above is as follows:

[0146] The main circuit has a closed loop including a MOSFET, a gate driver, and a resistor with a known resistance value. The transient response voltage waveform includes the gate voltage waveform of the MOSFET. The gate voltage waveform is based on the voltage measured across the resistor.

[0147] <<Measures to reduce inductance in the main circuit implementation configuration>> Figure 19 shows the main circuit implementation configuration 2A.

[0148] In configuration 2A, a planar mount type MOSFET 13A is used. This reduces the inductance in the MOSFET 13 package. In addition, in configuration 2A, the P terminal (positive terminal) PT and N terminal (negative terminal) NT, which are connected to the high-voltage power supply, are stacked. As a result, the loop inductance can be reduced in configuration 2A. Thus, configuration 2A is effective in that it can reduce inductance.

[0149] <<Application to semiconductor wafer testers>> Generally, a semiconductor wafer tester consists of a main unit and a probe head. The main unit and probe head are connected by a cable. The main unit outputs power to the probe head. Because the probe head is movable, the length of the cable connecting the main unit and probe head becomes long. As a result, a very large inductance is generated in the semiconductor wafer tester due to the cable. Therefore, the power output from the main unit is absorbed by the cable's inductance. Consequently, it is difficult to output high power from the main unit to the probe head.

[0150] Specifically, a long pulse width of 100 μs or more is required. As a result, temperature rise during measurement becomes a problem. Also, because power is drawn by the cable inductance, it is difficult to supply more than 1 kW of power to the object being measured.

[0151] Therefore, current semiconductor wafer testers are insufficient for measuring high power, such as that required to predict the switching characteristics of power devices. This necessitates a dedicated measurement device for semiconductor chips obtained by dicing semiconductor wafers. However, this makes 100% inspection of semiconductor chips difficult.

[0152] Therefore, an example of applying the measuring device in the embodiment to a semiconductor wafer tester will be described.

[0153] Figure 20 shows the configuration of the semiconductor wafer tester TS in the embodiment.

[0154] The semiconductor wafer tester TS consists of a main unit MU and a probe head PH.

[0155] The main unit MU is connected to the probe head PH via a cable. The main unit MU includes, for example, the simulation device 31, pulse generator 32, high-voltage power supply 33, and control unit 34 shown in Figure 4.

[0156] The probe head PH has a source pin SP, a gate pin GP, ​​and a main circuit MC. The main circuit MC has, for example, a power control unit 11 as shown in Figure 4. The power control unit 11 includes a capacitor 12, a MOSFET 13, and a gate driver 14.

[0157] The DUT (Device Under Test) is, for example, a semiconductor device formed on each of multiple chip regions of a semiconductor wafer (WF).

[0158] Thus, the semiconductor wafer tester TS comprises a main unit MU and a probe head PH connected to the main unit MU via a cable. The main unit MU includes the measuring device in the embodiment. The probe head PH includes the main circuit excluding the object under test DUT.

[0159] In a semiconductor wafer tester (TS), the main circuit (MC) includes a capacitor. This capacitor is charged by a high-voltage power supply located in the main unit (MU). When measuring a material under test, the charged capacitor in the main circuit (MC) functions as the power source. As a result, in a semiconductor wafer tester (TS), the current loop flowing through the main circuit is formed within the probe head (PH) when measuring a material under test. In other words, the current loop flowing through the main circuit does not flow through the cable connecting the main unit (MU) and the probe head (PH).

[0160] Therefore, when measuring a DUT (Device Under Test) using a semiconductor wafer tester TS, the inductance of the cable does not affect the measurement. As a result, when measuring a DUT using a semiconductor wafer tester TS, the inductance of the main circuit can be reduced to 20 nH or less, for example. Consequently, with a semiconductor wafer tester TS, measurements with ultra-fast pulse widths of less than 3 μs become possible. As a result, when measuring a DUT using a semiconductor wafer tester TS, the occurrence of temperature rise during measurement can be suppressed. Furthermore, with a semiconductor wafer tester TS, measurements at high power levels of 100 kW or more become possible.

[0161] Therefore, the semiconductor wafer tester TS enables 100% measurement of semiconductor devices (e.g., power devices) at high power. The measurement method using the semiconductor wafer tester TS in the embodiment makes it possible to create individual device models of all semiconductor chips, for example. Furthermore, the measurement method using the semiconductor wafer tester TS in the embodiment also makes it possible to predict the short-circuit withstand capability, which is a reliability index, for all devices.

[0162] <<Usefulness of the technical concept presented in this disclosure>> Figure 21 is a diagram illustrating the usefulness of the technical concept of this disclosure.

[0163] Generally, semiconductor parameter analyzers are used to measure the characteristics of switching elements, which are semiconductor devices. Semiconductor parameter analyzers can detect minute currents on the order of nA. Therefore, they can be used to measure leakage current. However, semiconductor parameter analyzers can only perform slow measurements. Consequently, semiconductor parameter analyzers are generally used to measure the static characteristics of semiconductor devices.

[0164] In this regard, measuring dynamic characteristics is necessary to measure switching operation or high-current characteristics that involve significant heat generation. Dynamic characteristics are transient characteristics. In this case, a semiconductor parameter analyzer cannot be used. Therefore, a tester combining a Rogowski coil or shunt resistor with an amplification amplifier is used.

[0165] Probes using Rogowski coils are current probes. A Rogowski coil includes an integrator, which functions as a low-pass filter. Therefore, high-speed operation is not possible. Consequently, measuring high-speed switching elements using SiC or GaN is difficult.

[0166] On the other hand, probes using shunt resistors are voltage probes. Shunt resistors generate heat. Therefore, probes using shunt resistors have difficulty achieving a large dynamic range for measuring current. This is because if they are designed to handle small currents, the heat generated at large currents becomes excessive. Furthermore, space must be secured to insert the shunt resistor. For this reason, downsizing the probe is difficult.

[0167] Both testers using Rogowski coils and testers using shunt resistors have difficulty measuring currents below mA. Therefore, evaluating leakage characteristics is difficult with either type of tester. Furthermore, because the effect of distributed inductance is not considered, errors are large during high-speed measurements.

[0168] In contrast, a measuring device (tester) applying the technical concept of this disclosure measures only voltage, without measuring current. Therefore, high-speed operation is possible. Furthermore, the measuring device uses a passive element model. That is, the measuring device performs simulations using an equivalent circuit that includes distributed inductance. Thus, the measuring device applying the technical concept of this disclosure also takes distributed inductance into consideration. As a result, the measuring device can achieve high-speed operation while minimizing measurement errors.

[0169] Furthermore, the measuring device includes a MOSFET. When the current is small, the current flowing through the MOSFET is logarithmically linked to the gate voltage. Therefore, according to the measuring device, minute currents on the order of nA can be detected by logarithmically amplifying them by measuring the gate voltage. As a result, the measuring device can ensure a dynamic range of the measured current from the order of nA to the order of kA without switching ranges.

[0170] Based on the above, the measuring device applying the technical concept of this disclosure is superior in that it can provide the only measuring device capable of completely measuring transient characteristics from normal operation to failure.

[0171] The present inventors have described the invention in detail based on its embodiments, but it goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from its essence. [Explanation of symbols]

[0172] 1. Measuring device 2. Implementation Configuration 2A Implementation Configuration 10 Main circuit 11 Power Control Unit 12 Capacitors 13 MOSFET 13A MOSFET 14 Gate Driver 15 probes 16 probes 20 Sensing Unit 21 sensors 30 Main Unit 31 Simulation device 32 Pulse Generators 33 High-voltage power supply 34 Control Unit 100 MOSFET 311 Input Section 312 Simulation Department 313 Simulation voltage waveform acquisition unit 314 Parameter Correction Section 315 Current-voltage characteristic acquisition unit 316 Output section 317 Storage section 401 Calibration section 402 Calibration voltage waveform acquisition unit 403 Correction Unit CAP capacitor DUT DUT GD Gate Driver GP gate pin MC main circuit MU main unit M1 Probe Point M2 probe point M3 Probe Point M4 probe point NT N terminal PH probe head PS High-Voltage Power Supply PT P terminal P1 Probe point P2 probe point P3 Probe Point P4 Probe Point SP Sourcepin TS Semiconductor Wafer Tester WF Semiconductor wafer

Claims

1. The main circuit includes an input section that receives the transient response voltage waveform of the object under test, A simulation unit that performs a simulation based on the equivalent circuit of the main circuit and the current-voltage model of the object under test, A measuring device comprising, The current-voltage model of the object under test is a function that takes a voltage value applied to the object under test as input and outputs a current value flowing through the object under test. The aforementioned function includes one or more parameters as coefficients, The aforementioned simulation unit, A simulation voltage waveform acquisition unit acquires a simulation voltage waveform corresponding to the transient response voltage waveform through the aforementioned simulation, A parameter correction unit that modifies the values ​​of the parameters included in the current-voltage model so that the transient response voltage waveform and the simulated voltage waveform match, A current-voltage characteristic acquisition unit acquires the current-voltage characteristics of an object under test based on a modified current-voltage model obtained by modifying the parameter values ​​in the parameter modification unit, It has, The current-voltage characteristic acquisition unit acquires a corrected simulated voltage waveform by performing a simulation again based on the corrected current-voltage model, and if the error between the corrected simulated voltage waveform and the transient response voltage waveform is within an acceptable range, the measurement device considers the corrected current-voltage model to be the current-voltage characteristic of the object under test.

2. In the measuring device according to claim 1, The measuring device is configured such that, if the error between the corrected simulation voltage waveform and the transient response voltage waveform is not within an acceptable range, the parameter correction unit repeatedly corrects the parameter values ​​until the error falls within the acceptable range.

3. In the measuring device according to claim 1, When comparing the transient response voltage waveform and the simulated voltage waveform, At a time less than the first time, the error between the transient response voltage waveform and the simulated voltage waveform is within an acceptable range, and at a time greater than or equal to the first time, the error between the transient response voltage waveform and the simulated voltage waveform is not within an acceptable range. At a time earlier than the first time, the voltage applied to the object under test is lower than the first voltage value, at the first time, the voltage applied to the object under test is the first voltage value, and at a time later than the first time, the voltage applied to the object under test is higher than the first voltage value. The aforementioned current-voltage model is, In a voltage range lower than the first voltage value, it is represented by the first current-voltage model, In the voltage range above the first voltage value, it is represented by the second current-voltage model, The measuring device modifies the parameters of the second current-voltage model without modifying the parameter values ​​of the first current-voltage model, and modifies the parameter values ​​of the second current-voltage model so that the transient response voltage waveform and the simulated voltage waveform match.

4. In the measuring device according to claim 1, The equivalent circuit includes a MOSFET and passive elements, The simulation unit is configured to perform simulations based on the equivalent circuit, the current-voltage model, the MOSFET model, and the passive element model. The MOSFET model described above is a function that takes a gate voltage value and a source-drain voltage value as input and outputs a source-drain current value. The aforementioned function includes one or more parameters as coefficients, The passive element model is a specific characteristic value of the passive element.

5. In the measuring device according to claim 4, The MOSFET model is a circuit simulation model or surrogate model consisting of a behavioral voltage-controlled power supply. The MOSFET model has input ports corresponding to gate voltage, drain voltage, and at least one temperature.

6. In the measuring device according to claim 4, The measuring device includes a calibration unit for correcting the MOSFET model and the passive element model.

7. In the measuring device according to claim 6, The calibration unit is A calibration voltage waveform acquisition unit that acquires a calibration voltage waveform corresponding to the transient response voltage waveform by simulation using a calibration sample having a known resistance value as the object to be measured, A correction unit corrects the parameter values ​​of the MOSFET model and the passive element model so that the transient response voltage waveform and the calibration voltage waveform match. It has.

8. In the measuring device according to claim 1, The measuring device stores a lookup table that associates the transient response voltage waveform with the modified current-voltage model. Based on the aforementioned lookup table, a modified current-voltage model corresponding to the first transient response voltage waveform input to the input unit is output without performing a simulation.

9. In the measuring device according to claim 1, The main circuit has a closed loop including a MOSFET, a gate driver, and a resistor having a known resistance value. The transient response voltage waveform includes the gate voltage waveform of the MOSFET. The gate voltage waveform is a waveform based on the voltage measured across the resistor element.

10. In the measuring device according to claim 1, The main circuit is, A capacitor for supplying power to the object under test, A MOSFET that controls the connection / disconnection between the capacitor and the object under test, It has, The aforementioned measuring device is A power supply for charging the aforementioned capacitor, A control unit for controlling the power supply, It has, The control unit is configured to control the charging energy of the capacitor so that it is less than the short-circuit withstand energy of the MOSFET.

11. The main unit and A probe head connected to the main unit via a cable, A semiconductor wafer tester equipped with, The main body includes the measuring device described in any one of claims 1 to 10. The probe head is a semiconductor wafer tester that includes the main circuit excluding the object to be measured.

12. (a) A step of inputting the transient response voltage waveform of the object to be measured included in the main circuit, (b) A step of performing a simulation based on the equivalent circuit of the main circuit and the current-voltage model of the object under test, A measurement method comprising, The current-voltage model of the object under test is a function that takes an estimated voltage value applied to the object under test as input and outputs an estimated current value flowing through the object under test. The aforementioned function includes one or more parameters as coefficients, The above step (b) is, (b1) A step of obtaining a simulated voltage waveform corresponding to the transient response voltage waveform by the simulation, (b) A step of modifying the values ​​of the parameters included in the current-voltage model so that the transient response voltage waveform and the simulated voltage waveform match. (b3) A step of acquiring the current-voltage characteristics of the object under test based on a modified current-voltage model obtained by modifying the parameter values ​​in the parameter modification unit, It has, The measurement method comprising step (b3) above, wherein a modified simulation voltage waveform is obtained by performing a simulation again based on the modified current-voltage model, and if the error between the modified simulation voltage waveform and the transient response voltage waveform is within an acceptable range, the modified current-voltage model is considered to be the current-voltage characteristic of the object under test.

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