A device for measuring junction capacitance of SiC devices

Abstract

The present invention discloses a device for measuring the junction capacitance of a SiC device, comprising a non-polarity module, an isolation current limiting discharge module and an isolation test module, wherein the input end of the non-polarity module is connected to an external power supply, the output end is connected to the isolation current limiting discharge module, and the output end of the isolation current limiting discharge module is connected to the isolation test module; the isolation test module is provided with a test interface, and the two ends of the isolation test module are respectively connected to the test interface and a capacitance test instrument. The present invention protects the measured component and the capacitance test instrument by setting an isolation current limiting discharge module, and connects the measured component through the test interface of the isolation test module. The isolation test module can also protect the capacitance test instrument from being damaged by DC high voltage, thereby improving the accuracy and reliability of capacitance testing.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device testing, and in particular to a device for measuring junction capacitance of a SiC device. Background Art

[0002] SiC (Silicon Carbide) materials have excellent properties such as large bandgap, high breakdown electric field, saturation drift velocity and high thermal conductivity, making them ideal materials for making high-power, high-frequency, high-temperature resistant and radiation-resistant devices. In addition, SiC power electronic devices have great advantages over traditional Si devices in terms of blocking performance, switching speed, high-temperature characteristics, etc., and are gradually being widely used.

[0003] As the third generation wide bandgap semiconductor, SiC devices have higher withstand voltage and higher operating frequency than traditional Si-based devices. The high-frequency and high-voltage working environment is highly sensitive to the junction capacitance of the device. Due to the characteristics of capacitors passing AC and blocking DC, although the junction capacitance of the device is very small, the impact of the junction capacitance of the device on the circuit still needs to be considered when designing high-frequency circuits. Therefore, it is urgent to have technical means to test the junction capacitance of SiC devices.

[0004] Traditional capacitance test instruments can only test the capacitance of passive devices, while SiC devices are usually active devices. The power supply voltage connected to SiC active devices will change the size of the device junction capacitance. In addition, the power supply of SiC devices may damage the test instrument or affect the accuracy of the test results. Summary of the invention

[0005] The purpose of the present invention is to propose a device for measuring the junction capacitance of a SiC device in view of the deficiencies in the prior art, which can effectively protect the measured component and the test instrument and improve the accuracy of the test result.

[0006] The technical solution to achieve the purpose of the present invention is:

[0007] A device for measuring the junction capacitance of a SiC device comprises a non-polarity module, an isolation current limiting discharge module and an isolation test module. The input end of the non-polarity module is connected to an external power supply, and the output end is connected to the isolation current limiting discharge module. The output end of the isolation current limiting discharge module is connected to the isolation test module. The isolation test module is provided with a test interface, and the two ends of the isolation test module are respectively connected to the test interface and a capacitance test instrument.

[0008] Furthermore, the isolation current limiting discharge module includes a resistor R3 whose two ends are respectively connected to the non-polarity module, one end of the resistor R3 is sequentially connected in series with an inductor L1 and a resistor R1, and a capacitor C1 is connected in parallel to the inductor L1; the other end of the resistor R3 is sequentially connected in series with an inductor L2 and a resistor R2, and a capacitor C2 is connected in parallel to the inductor L2, and the other ends of the resistor R1 and the resistor R2 are respectively connected to the two ends of the test interface.

[0009] Furthermore, the isolation test module includes two instrument protection modules respectively connected in series at both ends of the test interface and at both ends of the capacitance test instrument, and the instrument protection module includes a first capacitor and a second capacitor arranged in parallel, and the capacitance value of the first capacitor is greater than the capacitance value of the second capacitor.

[0010] Furthermore, the non-polarity module (4) comprises a diode D1, a diode D2, a diode D3, a diode D4, an electronic filter capacitor C7, a resistor R4, a transistor Q1, a transistor Q2, a constant current diode, a bidirectional precision voltage-stabilizing diode and an adjustable resistor R5, wherein the positive electrode of the diode D1 and the negative electrode of the diode D2 are both connected to one output end of the external power supply, the negative electrode of the diode D3 and the positive electrode of the diode D4 are both connected to the other output end of the external power supply; the positive electrodes of the diode D2 and the diode D3 are both connected to the ... 7. A bidirectional voltage regulator diode and an adjustable resistor R5; the cathodes of the diode D1 and the diode D4 are connected to the resistor R4 and the C electrode of the transistor Q1 at the same time, and the other end of the resistor R4, the other end of the electronic filter capacitor C7, and the C electrode of the transistor Q2 are connected to the B electrode of the transistor Q1; the other end of the bidirectional voltage regulator diode and the positive electrode of the constant current diode are connected to the E electrode of the transistor Q2; the B electrode of the transistor Q2 is connected to the sliding arm of the adjustable resistor R5; the other end of the adjustable resistor R5 and the cathode of the constant current diode are connected to the E electrode of the transistor Q1.

[0011] By adopting the above technical solution, the present invention has the following beneficial effects:

[0012] (1) The present invention improves the test accuracy while protecting the measured component and the capacitor test instrument by providing an isolation current limiting discharge module. The measured component is connected through a test interface and an isolation test module is provided to prevent the branch voltage from being applied to the capacitor test instrument. The test accuracy is improved while protecting the capacitor test instrument from being damaged by DC high voltage, thereby improving the reliability and accuracy of the capacitor test.

[0013] (2) The present invention connects capacitor C1 and inductor L1 in parallel with capacitor C2 and inductor L2 respectively, so that they work in a parallel resonant state, and combines resistors R1 and R2 to generate a large impedance, thereby isolating the high-frequency signal of the capacitor test instrument and improving the test accuracy; by setting resistor R3, the capacitor voltage at both ends of the active device under test is prevented from continuously increasing due to the spike interference voltage of the connected power supply, thereby improving the test accuracy and protecting the test instrument.

[0014] (3) The present invention forms an instrument protection module by setting two capacitors in parallel. The circuit is simple. One capacitor has a large capacity and the other has a small capacity, thereby isolating the DC voltage transmitted by the isolation current limiting discharge module from the capacitor test instrument, protecting the instrument from damage by the DC high voltage. At the same time, the small-capacity capacitor will not affect the high-frequency signal passing through the capacitor test instrument, so that the capacitor test instrument can be used for normal measurement. The instrument protection module is connected in series with the equivalent capacitor of the device under test to improve the test accuracy.

[0015] (4) The present invention adds a non-polarity module to the input end of the isolation current limiting discharge module, so the circuit design is simple and the power conversion is reliable and stable. It is also applicable to the case where the external power supply is an adjustable voltage source, AC or DC. It automatically distinguishes and converts the input power supply. The input end can be positive, negative DC or AC, which increases the application range of the device and plays a role in reverse protection. The adjustable power supply is to meet the test requirements under different voltages because the equivalent capacitance of the device under test will change under different voltages. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments and in conjunction with the accompanying drawings, wherein:

[0017] Figure 1 It is a circuit diagram of the present invention.

[0018] The reference numerals in the accompanying drawings are:

[0019] Non-polarity module 1, isolation current limiting discharge module 2, isolation test module 3, test interface 4. DETAILED DESCRIPTION

[0020] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] (Example 1)

[0022] like Figure 1The device for measuring the junction capacitance of SiC devices shown in the figure includes a non-polar module 1, an isolation current limiting discharge module 2 and an isolation test module 3, wherein the input end of the non-polar module 1 is an external power supply, and the output end is connected to the isolation current limiting discharge module 2, and the output end of the isolation current limiting discharge module 2 is connected to the isolation test module 3, and the isolation test module 3 is provided with a test interface 4 for connecting the measured component, and the isolation test module 3 is simultaneously connected to a capacitance test instrument, and the capacitance test instrument is used to measure the measured component. By setting the isolation current limiting discharge module 2, the test accuracy is improved while protecting the measured component and the capacitance test instrument, and the isolation test module prevents the branch current voltage from being applied to the capacitance test instrument, and the test accuracy is improved while protecting the capacitance test instrument from being damaged by the DC high voltage, thereby improving the reliability and accuracy of the capacitance test.

[0023] Specifically, the non-polarity module 1 includes a diode D1, a diode D2, a diode D3, a diode D4, an electronic filter capacitor C7, a resistor R4, a transistor Q1, a transistor Q2, a constant current diode, a bidirectional voltage regulator diode and an adjustable resistor R5. Capacitors, resistors and inductors can be formed by calculating the equivalent of one or more components in series or in parallel. The isolation current limiting discharge module 2 includes a resistor R3, an inductor L1, a resistor R1, a capacitor C1, an inductor L2, a resistor R2 and a capacitor C2. The isolation test module 3 includes a capacitor C3, a capacitor C4, a capacitor C5 and a capacitor C6, wherein the capacitor C3 and the capacitor C4 are arranged in parallel to form one of the instrument protection modules, and the capacitor C5 and the capacitor C6 are arranged in parallel to form another instrument protection module. By setting a non-polarity module 1 at the input end of the isolation current limiting discharge module 2, it is equally applicable when the external power supply is an adjustable voltage source, AC or DC, and automatically distinguishes and converts the input power supply. The input end can be positive, negative DC or AC, which increases the application scope of the device and plays a role in reverse protection. The adjustable power supply is to meet the test requirements under different voltages, because the equivalent capacitance of the device under test will change under different voltages.

[0024] The positive electrode of diode D1 and the negative electrode of diode D2 are connected to one output terminal of the external power supply, and the negative electrode of diode D3 and the positive electrode of diode D4 are connected to the other output terminal of the external power supply. The positive electrodes of diode D2 and diode D3 are connected to the electronic filter capacitor C7, the bidirectional voltage regulator diode and the adjustable resistor R5 at the same time. The negative electrodes of diode D1 and diode D4 are connected to the resistor R4 and the C electrode of transistor Q1 at the same time, and the other end of resistor R4, the other end of electronic filter capacitor C7 and the C electrode of transistor Q2 are connected to the B electrode of transistor Q1. The other end of the bidirectional voltage regulator diode and the positive electrode of the constant current diode are connected to the E electrode of transistor Q2. The B electrode of transistor Q2 is connected to the sliding arm of adjustable resistor R5, and the other end of adjustable resistor R5 and the negative electrode of the constant current diode are connected to the E electrode of transistor Q1. Resistor R3 is connected in parallel with both ends of adjustable resistor R5, and one end is connected in series with inductor L1 and resistor R1 in sequence, and the other end is connected in series with inductor L2 and resistor R2 in sequence. Capacitor C1 is connected in parallel with inductor L1, and capacitor C2 is connected in parallel with inductor L2, so that it works in a parallel resonance state, and combines resistors R1 and R2 to generate a large impedance, thereby isolating the high-frequency signal of the capacitor test instrument and improving the test accuracy. The other ends of resistors R1 and R2 are connected to the two ends of the test interface respectively, and one end of the two instrument protection modules is connected to the other ends of resistors R1 and R2 respectively, and the other ends are connected to the two test ports of the capacitor test instrument respectively. By setting resistor R3, the capacitor voltage at both ends of the active device under test is prevented from continuously increasing due to the spike interference voltage of the connected power supply, thereby improving the test accuracy and protecting the test instrument. Capacitor C3 and capacitor C5 are large-capacity capacitors, i.e., first capacitors, and capacitor C4 and capacitor C6 are small-capacity capacitors, i.e., second capacitors, thereby isolating the DC voltage transmitted by the isolation current limiting discharge module 2 from the capacitor test instrument, protecting the instrument from damage by the DC high voltage, and at the same time, the small-capacity capacitor will not affect the high-frequency signal passing through the capacitor test instrument, so that the capacitor test instrument can be measured and used normally. The so-called large-capacity capacitor and small-capacity capacitor refer to the difference in capacitance value between the two by more than 100 times.

[0025] When testing, the two ends of the test interface 4 are connected to the component under test. In the figure, SiC diode D is taken as an example, and Cj is its equivalent capacitance. According to the capacitance formula 1 / C=1 / C1+1 / C2+1 / Cj, C is the value of the series equivalent capacitance, that is, the value displayed by the capacitance test instrument. According to the formula, the larger the capacitance C1 and capacitance C2, the closer the C value is to Cj. Therefore, the value measured by the capacitance test instrument is equivalent to the Cj value of diode D, and the junction capacitance of the SiC device is measured.

[0026] This embodiment can measure the junction capacitance of SiC devices, and by setting up an isolation current limiting discharge module 2, the test accuracy is improved while protecting the measured component and the capacitance test instrument. The measured component is connected through a test interface 4, and an isolation test module 3 is provided to further protect the capacitance test instrument from being damaged by DC high voltage, thereby improving the reliability of the capacitance test. At the same time, a non-polarity module 1 is provided, which can automatically distinguish and convert the input power supply, and the input terminal can be positive, negative DC or AC, thereby increasing the scope of application of the device and playing a role in anti-reverse protection.

[0027] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for measuring junction capacitance of SiC devices, Features: The invention comprises a non-polarity module (1), an isolation current limiting discharge module (2) and an isolation test module (3), wherein the input end of the non-polarity module (1) is connected to an external power supply, the output end is connected to the isolation current limiting discharge module (2), and the output end of the isolation current limiting discharge module (2) is connected to the isolation test module (3); the isolation test module (3) is provided with a test interface (4), and the two ends of the isolation test module (3) are respectively connected to the test interface (4) and a capacitance test instrument; The isolation current limiting discharge module (2) comprises a resistor R3 whose two ends are respectively connected to the non-polarity module (1); one end of the resistor R3 is sequentially connected in series with an inductor L1 and a resistor R1, and a capacitor C1 is connected in parallel to the inductor L1; the other end of the resistor R3 is sequentially connected in series with an inductor L2 and a resistor R2, and a capacitor C2 is connected in parallel to the inductor L2; the other ends of the resistor R1 and the resistor R2 are respectively connected to two ends of the test interface (4).

2. The device for measuring junction capacitance of a SiC device according to claim 1, Features: The isolation test module (3) comprises two instrument protection modules respectively connected in series at two ends of the test interface (4) and two ends of the capacitance test instrument, the instrument protection module comprising a first capacitor and a second capacitor arranged in parallel, the capacitance value of the first capacitor being greater than the capacitance value of the second capacitor.

3. The device for measuring junction capacitance of a SiC device according to claim 1, Features: The non-polarity module (1) comprises a diode D1, a diode D2, a diode D3, a diode D4, an electronic filter capacitor C7, a resistor R4, a transistor Q1, a transistor Q2, a constant current diode, a bidirectional precision voltage-stabilizing diode and an adjustable resistor R5, wherein the positive electrode of the diode D1 and the negative electrode of the diode D2 are both connected to one output end of an external power supply, the negative electrode of the diode D3 and the positive electrode of the diode D4 are both connected to the other output end of the external power supply; the positive electrodes of the diode D2 and the diode D3 are both connected to the electronic filter capacitor C7, the bidirectional precision voltage-stabilizing diode and the adjustable resistor R5. The cathode of the diode D1 and the diode D4 are both connected to the resistor R4 and the C pole of the transistor Q1, and the other end of the resistor R4, the other end of the electronic filter capacitor C7 and the C pole of the transistor Q2 are all connected to the B pole of the transistor Q1; the other end of the bidirectional voltage stabilizing diode and the anode of the constant current diode are all connected to the E pole of the transistor Q2; the B pole of the transistor Q2 is connected to the sliding arm of the adjustable resistor R5; the other end of the adjustable resistor R5 and the cathode of the constant current diode are all connected to the E pole of the transistor Q1.

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