Silicon carbide MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) transfer characteristic curve testing method under bipolar switch stress

Abstract

The invention discloses a method for testing a transfer characteristic curve of a silicon carbide MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) under bipolar switch stress. The method comprises the following steps: S1, setting switch stress parameters: switch frequency f, duty ratio d, positive bias voltage VCC, negative bias voltage VEE and grid resistance R; s2, on the basis of the OTF technology, a silicon carbide MOSFET transfer characteristic curve extraction circuit is used for extracting a transfer characteristic curve, and a transfer characteristic curve in the transition period from the positive voltage to the negative voltage and a transfer characteristic curve in the transition period from the negative voltage to the positive voltage are extracted; and S3, drawing the two extracted transfer characteristic curves in the same coordinate axis, and representing and realizing accurate measurement of the hysteresis characteristics of the transfer characteristic curves by virtue of a closed graph enclosed by the two transfer characteristic curves. The method can effectively solve the problems that in a traditional extraction technology, complex preprocessing is needed before the transfer characteristic curve is extracted, and measurement delay exists in the extraction process, and the measurement accuracy is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of reliability assessment, and relates to a method for testing a transfer characteristic curve of a silicon carbide MOSFET, and in particular to a method for testing a transfer characteristic curve of a silicon carbide MOSFET under bipolar switch stress. Background Art

[0002] Silicon carbide (SiC) MOSFETs have been widely used to replace silicon (Si) MOSFETs in high-temperature, high-power electronic applications due to their excellent performance. However, due to the higher interface defect density in the gate oxide of SiC MOSFETs, their stability and reliability are more prominent. When subjected to a positive voltage, interface defects can cause electron capture, thereby reducing the electric field in the channel; when subjected to a negative voltage, these defects can release electrons, resulting in an increase in the channel electric field. Therefore, the transfer characteristic curve obtained during the transition from negative voltage to positive voltage shows a left shift compared to the transfer characteristic curve obtained during the transition from positive voltage to negative voltage. This unique phenomenon is often referred to as the hysteresis characteristic of the transfer characteristic curve.

[0003] The hysteresis of the transfer characteristic curve can reflect the level of interface defect density, which can be used as an important indicator to evaluate the health status of the device; on the other hand, it can significantly affect its speed, oscillation and other characteristics under high-speed switching working conditions, and is a key parameter in the application of silicon carbide MOSFET. Therefore, it is of great significance to accurately extract the transfer characteristic curve. Summary of the invention

[0004] The present invention provides a method for testing the transfer characteristic curve of a silicon carbide MOSFET under bipolar switch stress. The method can effectively solve the problems in traditional extraction technology, such as the need for complex preprocessing before extracting the transfer characteristic curve and the existence of measurement delays during the extraction process, thereby significantly improving the measurement accuracy.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A test circuit for transfer characteristic curve of silicon carbide MOSFET under bipolar switch stress includes a gate drive IC, a microcontroller, a DC-DC power supply module, an adjustable variable resistor and a non-inductive resistor, wherein:

[0007] The gate drive IC is used to provide a drive signal for the device under test;

[0008] The microcontroller is used to generate a PWM signal with adjustable switching frequency and duty cycle, and the PWM signal is input to the in-phase input terminal of the gate drive IC through the PCB wire;

[0009] The DC-DC power supply module is used to apply positive bias voltage and negative bias voltage to the device under test. The positive bias voltage is connected to the V CC The negative bias voltage is connected to the gate driver IC's V EE Department;

[0010] The adjustable resistor is connected to OUT+ and OUT- of the gate drive IC as a gate drive resistor, respectively, to adjust the gate drive resistor;

[0011] The non-inductive resistor is used for the load, and a DC-DC power supply module is used to provide a bus voltage for the load end.

[0012] A method for testing a transfer characteristic curve of a silicon carbide MOSFET under bipolar switch stress comprises the following steps:

[0013] Step S1: Setting switch stress parameters, which include switch frequency f (Hz), duty cycle d (%), positive bias voltage V CC (V), negative bias voltage V EE (V) and gate resistance R (Ω);

[0014] Step S2: Based on the On-The-Fly (OTF) technology, the transfer characteristic curve extraction circuit of the silicon carbide MOSFET is used to extract the transfer characteristic curve during the transition from the positive voltage to the negative voltage (Down) and the transfer characteristic curve during the transition from the negative voltage to the positive voltage (Up);

[0015] Step S3: Plot the two transfer characteristic curves extracted in step S2 on the same coordinate axis, and use the closed figure enclosed by the two to characterize and achieve accurate measurement of the hysteresis characteristics of the transfer characteristic curve.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The transfer characteristic curve of silicon carbide MOSFET is intrinsically linked to its practical application, but the complex preprocessing operation and measurement delay make it difficult to accurately extract the transfer characteristic curve. The present invention uses an OTF technology to extract the transfer characteristic curve of silicon carbide MOSFET. It can realize the transfer characteristic curve extraction with zero measurement delay based on synchronous sampling technology under continuous bipolar switching stress, ensuring that the charge in the interface defects can be released in time during the switching cycle, thereby improving the test accuracy, and the transfer characteristic curve can be directly extracted without any preprocessing operation, simplifying the control and extraction process.

[0018] 2. The present invention can plot the transfer characteristic curve (Down) during the transition from positive voltage to negative voltage and the transfer characteristic curve (Up) during the transition from negative voltage to positive voltage on the same coordinate axis, and the change in the hysteresis characteristic of the transfer characteristic curve can be significantly observed by means of the closed figure enclosed by the two.

[0019] 3. The present invention proposes a transfer characteristic curve test circuit for a silicon carbide MOSFET under bipolar switch stress. During the test, an oscilloscope is used to synchronously sample the gate-source voltage of the device under test and the current flowing through the load resistor to achieve accurate transfer characteristic curve extraction and analysis.

[0020] 4. Compared with the traditional method, the present invention does not require preprocessing operations and eliminates measurement delays, thereby improving the stability of the gate oxide layer charging state, thereby significantly improving the accuracy of transfer characteristic curve extraction.

[0021] 5. The present invention can significantly improve the accuracy of transfer characteristic curve extraction, and can lay the foundation for online monitoring and health management. It can provide strong support for the extraction and online monitoring of silicon carbide MOSFET transfer characteristic curves, and help the selection and application of silicon carbide MOSFET devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram comparing OTF technology with traditional technology;

[0023] Figure 2 This is the schematic diagram of the measurement circuit principle;

[0024] Figure 3 It is the transfer characteristic curve under different switching frequencies and duty cycles;

[0025] Figure 4 is the transfer characteristic curve under different switching speeds;

[0026] Figure 5 is the transfer characteristic curve under different positive bias voltages;

[0027] Figure 6 Transfer characteristic curves under different negative bias voltages. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0029] Conventional extraction methods require complex preprocessing and measurement delays, which makes it difficult to accurately extract the transfer characteristic curve under bipolar switch stress. To this end, the present invention provides a method for testing the transfer characteristic curve of a silicon carbide MOSFET under bipolar switch stress, such as Figure 1 As shown in the figure, this method uses OTF technology to extract the transfer characteristic curve. This method can realize the transfer characteristic curve extraction with zero measurement delay based on synchronous sampling technology under continuous bipolar switching stress. During the switching cycle, the charge in the interface defects can be released back to the channel in time, improving the accuracy of the test data. During the extraction process, an oscilloscope is used to synchronously sample the gate-source voltage of the device under test and the current flowing through the load resistor to achieve accurate data recording and analysis. The specific steps are as follows:

[0030] Step S1: Setting switch stress parameters, which include switch frequency f (Hz), duty cycle d (%), positive bias voltage V CC (V), negative bias voltage V EE (V) and gate resistance R (Ω).

[0031] Step S2: Based on the On-The-Fly (OTF) technology, the transfer characteristic curve is extracted using the silicon carbide MOSFET transfer characteristic curve extraction circuit to extract the transfer characteristic curve during the transition from positive voltage to negative voltage (Down) and the transfer characteristic curve during the transition from negative voltage to positive voltage (Up).

[0032] like Figure 2 As shown, the SiC MOSFET transfer characteristic curve extraction circuit includes a gate drive IC, a microcontroller, a DC-DC power supply module, an adjustable variable resistor, and a non-inductive resistor, wherein:

[0033] The gate drive IC is used to provide a drive signal for the device under test;

[0034] The microcontroller is used to generate a PWM signal with adjustable switching frequency and duty cycle, and the PWM signal is input to the in-phase input terminal of the gate drive IC through the PCB wire;

[0035] The DC-DC power supply module is used to apply positive bias voltage and negative bias voltage to the device under test. The positive bias voltage is connected to the V CC The negative bias voltage is connected to the gate driver IC's V EE Department;

[0036] The adjustable resistor is connected to OUT+ and OUT- of the gate drive IC as a gate drive resistor, respectively, to adjust the gate drive resistor;

[0037] The non-inductive resistor is used for the load, and a DC-DC power supply module is used to provide a bus voltage for the load end.

[0038] The specific extraction steps are as follows:

[0039] Step S21: using a gate driver IC to provide a driving signal for the device under test;

[0040] Step S22: using a microcontroller to generate a PWM signal with adjustable switching frequency and duty cycle, and the PWM signal is input to the in-phase input terminal of the gate drive IC through a PCB conductor;

[0041] Step S23: Use a DC-DC power supply module to provide positive bias voltage and negative bias voltage, wherein the positive bias voltage can be adjusted from +5V to +20V, and the negative bias voltage can be adjusted from -5V to -10V. Connect the positive bias voltage to the V CC The negative bias voltage is connected to the gate driver IC's V EE The circuit can flexibly adjust the gate-source voltage amplitude;

[0042] Step S24: Use a 0Ω-1kΩ adjustable resistor as a gate drive resistor and connect it to OUT+ and OUT- of the gate drive IC respectively, so that the circuit can flexibly adjust the gate drive resistance;

[0043] Step S25: Select a 5Ω non-inductive resistor with a heat sink as a load resistor, and use a DC-DC power module to provide a 3.3V voltage for the bus;

[0044] Step S26: placing the device under test (heat generating component) on the back of the circuit board and adopting copper cladding and window opening to increase heat dissipation, and minimizing loop inductance during wiring to reduce parasitic parameters and prevent oscillation;

[0045] Step S27: the heating element operates under a continuous pulse width modulation (PWM) signal, and an oscilloscope is used to synchronously sample the gate-source voltage of the heating element and the current flowing through the load resistor, thereby obtaining a transfer characteristic curve (Down) during the transition from a positive voltage to a negative voltage and a transfer characteristic curve (Up) during the transition from a negative voltage to a positive voltage;

[0046] Step S3: Plot the two transfer characteristic curves extracted in step S2 on the same coordinate axis, and use the closed figure enclosed by the two to characterize and achieve accurate measurement of the hysteresis characteristics of the transfer characteristic curve.

[0047] Example:

[0048] In order to ensure the reliability of the measurement results, this embodiment selects two representative silicon carbide MOSFETs as experimental test devices: one is a planar gate (DUT.P) and the other is a trench gate (DUT.T). Set the bipolar switch stress configuration: the switching frequency is 1kHz, the duty cycle is 50%, the positive bias voltage is +20V, the negative bias voltage is -10V, and the gate resistance is 200Ω. Modify the bipolar switch stress configuration by controlling the variables, extract the transfer characteristic curve (Down) during the transition from positive voltage to negative voltage and the transfer characteristic curve (Up) during the transition from negative voltage to positive voltage, draw the above two transfer characteristic curves on the same coordinate axis, and use the closed figure enclosed by the two to characterize the change in the hysteresis characteristics of the transfer characteristic curve. The specific steps are as follows:

[0049] Step S1: Measure at different switching frequencies (1kHz, 10kHz, 100kHz). Figure 3 As shown, the lower the frequency, the more obvious the hysteresis characteristic.

[0050] Step S2: Measure at different duty ratios (10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%). Figure 3 As shown, the higher the duty cycle, the more obvious the hysteresis characteristic.

[0051] Step S3: perform measurements at different gate resistances (10Ω, 50Ω, 100Ω, 150Ω, 250Ω, 300Ω, 350Ω). Figure 4 As shown, the higher the gate resistance, the more obvious the hysteresis characteristic.

[0052] Step S4: Measure at different positive bias voltages (+5V, +10V, +15V, +20V). Figure 5 As shown, the higher the positive bias voltage amplitude, the more obvious the hysteresis characteristic.

[0053] Step S5: Measure under different negative bias voltages (-5V, -8V, -10V). Figure 6 As shown, the higher the negative bias voltage amplitude, the more obvious the hysteresis characteristic.

[0054] In summary, the OTF technology effectively achieves zero measurement delay transfer characteristic curve extraction based on synchronous sampling technology under continuous bipolar switching stress, and no additional preprocessing is required, which significantly reduces the interface defects that are not detected during the extraction process, and also reveals obvious hysteresis characteristics. Increasing the amplitude of the positive and negative bias voltages, reducing the switching frequency, and selecting a slightly larger gate resistance can significantly observe the hysteresis characteristics of the transfer characteristic curve.

Claims

1. A test circuit for transfer characteristic curve of silicon carbide MOSFET under bipolar switch stress, characterized in that The test circuit includes a gate drive IC, a microcontroller, a DC-DC power supply module, an adjustable variable resistor and a non-inductive resistor, wherein: The gate drive IC is used to provide a drive signal for the device under test; The microcontroller is used to generate a PWM signal with adjustable switching frequency and duty cycle, and the PWM signal is input to the in-phase input terminal of the gate drive IC through the PCB wire; The DC-DC power supply module is used to apply positive bias voltage and negative bias voltage to the device under test. The positive bias voltage is connected to the V CC The negative bias voltage is connected to the gate driver IC's V EE Department; The adjustable resistor is connected to OUT+ and OUT- of the gate drive IC as a gate drive resistor, respectively, to adjust the gate drive resistor; The non-inductive resistor is used for the load, and a DC-DC power supply module is used to provide a bus voltage for the load end.

2. A method for testing transfer characteristic curves of silicon carbide MOSFET under bipolar switch stress, characterized in that The method comprises the following steps: Step S1: Setting switch stress parameters, wherein the switch stress parameters include switch frequency f, duty cycle d, positive bias voltage V CC , negative bias voltage V EE and gate resistance R; Step S2: Based on the OTF technology, the transfer characteristic curve is extracted by using the extraction circuit described in claim 1, and the transfer characteristic curve during the transition from positive voltage to negative voltage and the transfer characteristic curve during the transition from negative voltage to positive voltage are extracted; Step S3: Plot the two transfer characteristic curves extracted in step S2 on the same coordinate axis, and use the closed figure enclosed by the two to characterize and achieve accurate measurement of the hysteresis characteristics of the transfer characteristic curve.

3. The method for testing transfer characteristic curve of silicon carbide MOSFET under bipolar switch stress according to claim 2, characterized in that The specific steps of step S2 are as follows: Step S21: using a gate driver IC to provide a driving signal for the device under test; Step S22: using a microcontroller to generate a PWM signal with adjustable switching frequency and duty cycle, and the PWM signal is input to the in-phase input terminal of the gate drive IC through a PCB conductor; Step S23: Use a DC-DC power module to provide positive bias voltage and negative bias voltage, and connect the positive bias voltage to the V CC The negative bias voltage is connected to the gate driver IC's V EE The circuit can flexibly adjust the gate-source voltage amplitude; Step S24: Use an adjustable variable resistor as a gate drive resistor and connect them to OUT+ and OUT- of the gate drive IC respectively, so that the circuit can flexibly adjust the gate drive resistor; Step S25: Select a non-inductive resistor and a heat sink as the load resistor, and use a DC-DC power module to provide a 3.3V voltage for the bus; Step S26: placing the device under test on the back of the circuit board and adopting copper cladding and window opening to increase heat dissipation, and minimizing loop inductance during wiring to reduce parasitic parameters and prevent oscillation; Step S27: The device under test operates under a continuous pulse width modulation signal, and an oscilloscope is used to synchronously sample the gate-source voltage of the heat-generating component and the current flowing through the load resistor, thereby obtaining a transfer characteristic curve during the transition from positive voltage to negative voltage and a transfer characteristic curve during the transition from negative voltage to positive voltage.

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