Test method and apparatus for bipolar degradation of diode, and device

Abstract

A test method and apparatus for bipolar degradation of a diode, and a device. The method comprises: respectively performing static characteristic tests on a first diode and a second diode, so as to obtain a first static characteristic test result and a second static characteristic test result; setting a pulse test current, a pulse test time and a pulse cycle time, so that, on the basis of the pulse test current, the pulse test time and the pulse cycle time, a power semiconductor pulse current test device performs repeated short pulse current power cycle tests on the first diode under normal temperature conditions, and performs repeated short pulse current power cycle tests on the second diode under high temperature conditions; then, performing static tests, so as to obtain a plurality of static characteristic test results; and on the basis of the static characteristic test results, obtaining a bipolar degradation test result of a diode. By means of the method, bipolar degradation of the diode is tested, and the accuracy and reliability of the test result are improved.

Description

A method, equipment and apparatus for testing the bipolar degradation of diodes Technical Field

[0001] This invention relates to the field of SiC power semiconductor device technology, and in particular to a method, equipment and apparatus for testing the bipolar degradation of diodes. Background Technology

[0002] Compared with silicon-based semiconductor materials, SiC power semiconductors have superior material properties such as a larger band gap, higher thermal conductivity, and higher electron saturation velocity. They also have stronger temperature resistance and can be used at higher frequencies, making them widely used in power electronic systems with high power density and high conversion efficiency.

[0003] Like silicon-based MOSFETs, SiC MOSFETs also have a body diode formed by the PN junction. The body diode of a SiC MOSFET has a short reverse recovery time and low recovery loss, exhibiting excellent forward operating characteristics. Therefore, it can be used in circuits to absorb current generated by inductive loads, acting as a freewheeling diode. Unlike silicon-based MOSFETs, when current continuously flows through the body diode of a SiC MOSFET, the forward voltage of the body diode may increase over time; this phenomenon is called "body diode bipolar degradation." When electron-hole recombination occurs for a long time in SiC power semiconductor devices and the recombination energy exceeds a certain value, the SiC power semiconductor device ages, and pre-existing plane dislocations (BPDs) expand into stacked layers (SFs), severely affecting the performance of SiC bipolar power devices. For example, minority carrier lifetime decreases and forward voltage drop drift occurs, which is very detrimental to the long-term reliability of SiC bipolar power devices.

[0004] Currently, due to limitations in SiC epitaxial wafer manufacturing processes, the generation of base plane dislocations cannot be completely avoided. Research has revealed significant differences in the occurrence of base plane dislocations in SiC epitaxial wafers from different manufacturers, and even within the same manufacturer, the density of base plane dislocation defects varies between different batches. Therefore, SiC MOSFET manufacturers and users need to test the bipolar degradation of the body diode. To study the bipolar degradation mechanism, SiC MOSFETs are typically subjected to DC current stress power cycling at room temperature. Once the device has aged to a certain extent, the forward IV characteristics and on-resistance Rdson are measured. However, this testing method involves complex power cycling control, high costs, real-time junction temperature monitoring, and complex switching control to avoid the impact of thermal runaway and other factors on the package. Furthermore, it is usually conducted at room temperature, resulting in low aging efficiency. Summary of the Invention

[0005] To address the aforementioned technical problems, embodiments of the present invention provide a diode bipolar degradation testing method, equipment, and apparatus, which enables the testing of diode bipolar degradation and improves the accuracy and reliability of test results.

[0006] A first aspect of this invention provides a diode bipolar degradation testing method, the method comprising:

[0007] Static characteristic tests were performed on the first diode and the second diode respectively, and the results of the first static characteristic test and the second static characteristic test were obtained.

[0008] The pulse test current, pulse test time, and pulse cycle time are set so that the power semiconductor pulse current test equipment performs a repetitive short pulse current power cycle test on the first diode under normal temperature conditions and a repetitive short pulse current power cycle test on the second diode under high temperature conditions, based on the pulse test current, pulse test time, and pulse cycle time.

[0009] Obtain the third static characteristic test result of the first diode after repeated short pulse current power cycle test, and the fourth static characteristic test result of the second diode after repeated short pulse current power cycle test.

[0010] The results of the first static characteristic test, the second static characteristic test, the third static characteristic test, and the fourth static characteristic test are compared to obtain the comparison results. Based on the comparison results, the bipolar degradation test results of the diode are obtained.

[0011] In one possible implementation of the first aspect, static characteristic testing is performed on the first diode and the second diode, including:

[0012] The forward IV characteristics and on-resistance Rdson of the first and second diodes were tested.

[0013] In one possible implementation of the first aspect, the pulse test current, pulse test time, and pulse cycle time are obtained by using a power semiconductor pulse current testing device. The specific testing process is as follows:

[0014] A reverse voltage is applied between the gate and source of the diode under test, the second power switching device, and the third power switching device, and a positive pulse voltage is applied between the gate and source of the first power switching device, so that the first power switching device, the inductor, and the electrolytic capacitor form a first circuit, thereby obtaining a first driving signal and a first pulse current, wherein the diode under test is either the first diode under test or the second diode under test.

[0015] After the positive pulse of the first power switching device, a positive pulse voltage is applied between the gate and source of the second power switching device to form a second circuit with the diode under test, inductor and the second power switching device, thereby obtaining a second drive signal and a second pulse current.

[0016] A positive pulse voltage is applied between the gate and source of the third power switching device to obtain a third driving signal. This causes the diode under test, the third power switching device, and the resistor to form a third circuit. The power semiconductor pulse current test equipment is then fully discharged. The pulse duration of the first driving signal is determined as the pulse test time. The pulse cycle time is obtained based on the pulse start time and pulse end time of the first, second, and third driving signals. The pulse test current is determined based on the first pulse current, the second pulse current, and the third pulse current.

[0017] In one possible implementation of the first aspect, after performing a test using a power semiconductor pulse current testing device, it further includes:

[0018] Record the single-pulse IV characteristics, calculate the instantaneous temperature during the single-pulse current based on the pulse IV characteristics, and ensure that the instantaneous temperature is lower than the preset case temperature of the first or second diode during repeated short-pulse current power cycle testing.

[0019] In one possible implementation of the first aspect, the pulse test time is 20µs and the pulse cycle time is 1000h to 1500h.

[0020] A second aspect of this invention provides a power semiconductor pulse current testing device, including a drive circuit and a main circuit. The main circuit includes a first power switching device, a second power switching device, a third power switching device, an inductor, a resistor, and an electrolytic capacitor. The positive terminal of the electrolytic capacitor is connected to a power supply, and the negative terminal of the electrolytic capacitor is grounded.

[0021] The source of the third power switch is connected to the power supply after being connected in series with a resistor. The drain of the third power switch is connected to the drain of the second power switch. The source of the second power switch is connected to the drain of the first power switch after being connected in series with an inductor. The source of the second power switch is connected to the power supply. The source of the first power switch is grounded. The drains of the second power switch, the third power switch, and the first power switch serve as the access points for the SiC MOSFET module.

[0022] In one possible implementation of the second aspect, the drive circuit includes multiple single-channel isolated gate drivers, an on-resistor, an off-resistor, and a Schottky diode, wherein the single-channel isolated gate drivers are connected to a signal generator.

[0023] The single-channel isolated gate driver is connected to the signal generator via a first connector, a second connector, and a third connector, and is connected to the power supply via a fourth connector, a fifth connector, a sixth connector, and a seventh connector.

[0024] The single-channel isolated gate driver is used to isolate and amplify small input signals of a specific frequency and pulse width to generate signals that drive the diodes.

[0025] In one possible implementation of the second aspect, a single-channel isolated gate driver is used to input a first drive signal with a first set frequency and a first set pulse width at the first connection point, and after isolation amplification by the first single-channel isolated gate driver, output a drive signal to drive the first power switching device.

[0026] A second drive signal with a second set frequency and a second set pulse width is input at the second connector. After isolation and amplification by the second single-channel isolated gate driver, the drive signal of the second drive power switching device is output.

[0027] A third drive signal with a third set frequency and a third set pulse width is input at the third connector. After isolation and amplification by the third single-channel isolated gate driver, a drive signal for driving the third power switching device is output.

[0028] A second aspect of the present invention provides a diode bipolar degradation testing device, including a power supply, a power semiconductor pulse current testing device, and a SiC MOSFET module, wherein the SiC MOSFET module includes a first diode and a second diode, the power supply is connected to the power semiconductor pulse current testing device, and the power semiconductor pulse current testing device is connected to the SiC MOSFET module.

[0029] In one possible implementation of the third aspect, the power semiconductor pulse current test equipment is used to perform a repetitive short pulse current power cycle test on the first diode under normal temperature conditions and a repetitive short pulse current power cycle test on the second diode under high temperature conditions, based on the pulse test current, the pulse test time, and the pulse cycle time.

[0030] The SiC MOSFET module is used to perform repetitive short-pulse current power cycle tests under normal temperature conditions or under high temperature conditions, based on the pulse test current, pulse test time, and pulse cycle time.

[0031] The diode bipolar degradation testing method provided in this invention performs static characteristic tests on a first diode and a second diode respectively, obtaining first static characteristic test results and second static test results. A pulse test current, pulse test time, and pulse cycle time are set so that a power semiconductor pulse current testing device performs repetitive short-pulse current power cycle tests on the first diode under normal temperature conditions and on the second diode under high temperature conditions, based on the pulse test current, pulse test time, and pulse cycle time. A third static characteristic test result is obtained after the repetitive short-pulse current power cycle test on the first diode, and a fourth static characteristic test result is obtained after the repetitive short-pulse current power cycle test on the second diode. The first, second, third, and fourth static characteristic test results are compared to obtain a comparison result, and the diode bipolar degradation test result is obtained based on the comparison result. Through this method, the accuracy and reliability of the test results are improved by realizing the testing of diode bipolar degradation. Attached Figure Description

[0032] Figure 1: A schematic flowchart of a test method for an embodiment of the diode bipolar degradation test method provided by the present invention;

[0033] Figure 2: A schematic diagram of the first circuit of an embodiment of the diode bipolar degradation test method provided by the present invention;

[0034] Figure 3: A schematic diagram of the second circuit of an embodiment of the diode bipolar degradation test method provided by the present invention;

[0035] Figure 4: A schematic diagram of the third circuit of an embodiment of the diode bipolar degradation test method provided by the present invention;

[0036] Figure 5: A schematic diagram of the waveforms of PWM1, PWM2, PWM3, I1 and I2 in one embodiment of the diode bipolar degradation test method provided by the present invention;

[0037] Figure 6: A schematic diagram of the main circuit of an embodiment of the diode bipolar degradation test method provided by the present invention;

[0038] Figure 7: A schematic diagram of the first-stage driving circuit of an embodiment of the diode bipolar degradation test method provided by the present invention;

[0039] Figure 8: A schematic diagram of the driving circuit in the second stage of an embodiment of the diode bipolar degradation test method provided by the present invention;

[0040] Figure 9: A schematic diagram of the driving circuit in the third stage of an embodiment of the diode bipolar degradation test method provided by the present invention;

[0041] Figure 10: A block diagram of an embodiment of the diode bipolar degradation test method provided by the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0044] Currently, due to limitations in SiC epitaxial wafer manufacturing processes, the generation of base plane dislocations cannot be completely avoided. Research has revealed significant differences in the occurrence of base plane dislocations in SiC epitaxial wafers from different manufacturers, and even within the same manufacturer, the density of base plane dislocation defects varies across different batches. Therefore, SiC MOSFET manufacturers and users need to evaluate the bipolar degradation of the body diode. To study the bipolar degradation mechanism, SiC MOSFETs are typically subjected to DC current stress power cycling at room temperature. Once the device has aged to a certain extent, the forward IV characteristics and on-resistance Rdson are measured to assess degradation. However, this testing method involves complex power cycling control, high costs, real-time junction temperature monitoring, and complex switching control to avoid the impact of thermal runaway and other factors on the package. Furthermore, it is usually conducted at room temperature, resulting in low aging efficiency.

[0045] Based on this, embodiments of this application provide a diode bipolar degradation testing method, equipment, and apparatus, aiming to test diode bipolar degradation and improve the accuracy and reliability of test results.

[0046] Please refer to Figure 1, which is a flowchart illustrating an embodiment of the diode bipolar degradation testing method provided by the present invention, including steps S101 to S104, each of which is as follows:

[0047] S101. Perform static characteristic tests on the first diode and the second diode respectively to obtain the first static characteristic test results and the second static test results.

[0048] It is worth noting that both the first diode and the second diode refer to SiC MOSFET body diodes. The first diode is a SiC MOSFET body diode, and the second diode is a SiC MOSFET body diode II. The first diode and the second diode are SiC MOSFET body diodes of the same model and with the same packaging process. The first static characteristic test result refers to the result obtained by performing static characteristic tests on the first diode, and the second static test result refers to the result obtained by performing static characteristic tests on the second diode.

[0049] Static characteristic tests were performed on SiC MOSFET body diode one and SiC MOSFET body diode two respectively, and the static characteristic test results of SiC MOSFET body diode one and SiC MOSFET body diode two were obtained.

[0050] In some embodiments, step S101, "performing static characteristic tests on the first diode and the second diode," includes, but is not limited to, the following steps:

[0051] The forward IV characteristics and on-resistance Rdson of the first and second diodes were tested.

[0052] Specifically, the static characteristics include the forward IV characteristics and on-resistance Rdson of the body diode, i.e., the forward IV characteristics and on-resistance Rdson of SiC MOSFET body diode one and SiC MOSFET body diode two are tested. The forward IV characteristics and on-resistance Rdson of the body diode are tested using a power device analyzer.

[0053] S102. Set the pulse test current, pulse test time, and pulse cycle time so that the power semiconductor pulse current test equipment can perform a repetitive short pulse current power cycle test on the first diode under normal temperature conditions and a repetitive short pulse current power cycle test on the second diode under high temperature conditions, based on the pulse test current, pulse test time, and pulse cycle time.

[0054] A test platform was set up to generate a predetermined pulse test current and determine the test pulse duration. Temperature assessments were conducted at both room temperature and high temperature to ensure that the instantaneous temperatures of SiC MOSFET body diode 1 and SiC MOSFET body diode 2 did not exceed the maximum case temperature of the devices during the test. Based on the obtained pulse test current, pulse test duration, and pulse cycle time, a power semiconductor pulse current testing device was used to perform repetitive short-pulse current power cycle tests on SiC MOSFET body diode 1 under normal temperature conditions, and on SiC MOSFET body diode 2 under high-temperature conditions.

[0055] The high temperature is determined based on the highest heat resistance temperature of the semiconductor material; the pulse duration of the short pulse is 20µs-50µs.

[0056] In some embodiments, step S102, "setting the pulse test current, pulse test time, and pulse cycle time," includes, but is not limited to, the following steps:

[0057] A reverse voltage is applied between the gate and source of the diode, the second power switching device, and the third power switching device, and a positive pulse voltage is applied between the gate and source of the first power switching device, so that the first power switching device, the inductor, and the electrolytic capacitor form a first circuit, thereby obtaining a first driving signal and a first pulse current, wherein the diode is either a first diode or a second diode.

[0058] After the positive pulse of the first power switching device, a positive pulse voltage is applied between the gate and source of the second power switching device, so that the diode, inductor and the second power switching device form a second circuit, and a second drive signal and a second pulse current are obtained.

[0059] A positive pulse voltage is applied between the gate and source of the third power switching device to obtain a third driving signal. This forms a third circuit with the diode, the third power switching device, and the resistor. The power semiconductor pulse current test equipment is then fully discharged. The pulse duration of the first driving signal is determined as the pulse test time. The pulse cycle time is obtained based on the pulse start time and pulse end time of the first, second, and third driving signals. The pulse test current is determined based on the first pulse current, the second pulse current, and the third pulse current.

[0060] It is worth noting that the diode under test refers to the body diode of the SiC MOSFET under test, the second power switch device refers to power switch device Q2, the third power switch device refers to power switch device Q3, and the first power switch device refers to power switch device Q1. The first drive signal refers to PWM1, the second drive signal refers to PWM2, and the third drive signal refers to PWM3.

[0061] Specifically, before testing, the SiC MOSFET body diode to be tested is connected to a power semiconductor pulse current testing device. Multiple tests are performed using the power semiconductor pulse current testing device to determine the short pulse current and pulse duration for the test. One test process is as follows:

[0062] In the first stage, a reverse voltage is applied between the body diode of the SiC MOSFET under test and the gate and source of power switching devices Q2 and Q3, respectively, to ensure that the body diode of the SiC MOSFET under test and power switching devices Q2 and Q3 are in a completely off state. A positive pulse voltage is applied between the gate and source of power switching device Q1. The driving signal for the gate voltage of power switching device Q1 is PWM1. At this time, power switching device Q1, inductor L1 and electrolytic capacitor CE1 form the first loop, as shown in Figure 2, generating pulse current I1.

[0063] In the second stage, after the positive pulse of power switch Q1, the body diode of the SiC MOSFET under test and power switch Q1 and power switch Q3 are kept in the off state. A positive pulse voltage is applied between the gate and source of power switch Q2. The driving signal of the gate voltage of power switch Q2 is PWM2. At this time, inductor L1, power switch Q2 and SiC MOSFET body diode form a second loop, as shown in Figure 3. The current through the body diode of the SiC MOSFET module under test is I2.

[0064] In the third stage, the body diode of the SiC MOSFET under test and the power switching devices Q1 and Q2 are kept in the off state. A positive pulse voltage is applied between the gate and source of the power switching device Q3. The driving signal for the gate voltage of the power switching device Q3 is PWM3. At this time, the body diode of the SiC MOSFET under test, the power switching device Q3 and the resistor R1 form a third loop, as shown in Figure 4. The power semiconductor pulse current test equipment is completely discharged. Thus, one test cycle is completed.

[0065] The waveforms of PWM1, PWM2, PWM3, I1, and I2 are shown in Figure 5. PWM1, PWM2, and PWM3 have the same period. The pulse duration of PWM1 is the set pulse time. The start time of the first pulse of PWM2 is the end time of the first pulse of PWM1. The pulse duration of PWM2 is greater than the pulse duration of PWM1. The start time of the first pulse of PWM3 is the end time of the first pulse of PWM2. The pulse duration of PWM3 is greater than the pulse duration of PWM2.

[0066] In some embodiments, step S102, "after performing a test using a power semiconductor pulse current testing device", includes, but is not limited to, the following steps:

[0067] Record the single-pulse IV characteristics, calculate the instantaneous temperature during the single-pulse current based on the pulse IV characteristics, and ensure that the instantaneous temperature is lower than the preset case temperature of the first or second diode during repeated short-pulse current power cycle testing.

[0068] Specifically, at the end of a test cycle, the single-pulse IV characteristic is measured and recorded using a power semiconductor pulse current test device. Based on this characteristic, the instantaneous temperature during the single-pulse current is calculated and evaluated to ensure that the instantaneous temperature does not exceed the maximum case temperature of the SiC MOSFET body diode under test during the test, so as to prevent adverse effects on the packaging characteristics of the diode.

[0069] After repeated testing, under the conditions of a pulse current of 1000A, a pulse time of 20us, and a pulse duty cycle of 2%, the instantaneous temperature at both room temperature and high temperature does not exceed the maximum case temperature of the device of 175℃. There is no continuous heat accumulation, and no need for a real-time junction temperature monitoring system and complex switching control. At this time, the predetermined 1000A pulse current can be generated.

[0070] After generating the predetermined 1000A pulse current, during the test, SiC MOSFET body diode one and SiC MOSFET body diode two of the same model and packaging process were used to conduct repetitive short pulse current power cycling tests with continuous pulse duration at room temperature and high temperature, respectively. Then, the static characteristics were tested to conduct bipolar degradation research.

[0071] In some embodiments, step S102, "setting the pulse test current, pulse test time, and pulse cycle time," includes, but is not limited to, the following steps:

[0072] The pulse test time is 20µs, the duty cycle is 2%, and the pulse cycle time is 1000h to 1500h.

[0073] When performing repetitive short pulse current power cycle tests: the pulse test time is 20us, the duty cycle is 2%, the short pulse current is 1000A, and the pulse cycle time is 1000h-1500h.

[0074] S103. Obtain the third static characteristic test result of the first diode after repeated short pulse current power cycle test, and the fourth static characteristic test result of the second diode after repeated short pulse current power cycle test.

[0075] After performing a repetitive short-pulse current power cycling test with a continuous pulse duration on SiC MOSFET body diode one at room temperature, its static characteristics were tested again. After performing a repetitive short-pulse current power cycling test with a continuous pulse duration on SiC MOSFET body diode two at high temperature, its static characteristics were tested again, and then the static characteristic test results were obtained.

[0076] S104. Compare the first static characteristic test results, the second static characteristic test results, the third static characteristic test results, and the fourth static characteristic test results to obtain the comparison results. Based on the comparison results, obtain the bipolar degradation test results of the diode.

[0077] The static characteristics of SiC MOSFET body diode 1 measured at room temperature and SiC MOSFET body diode 2 measured at high temperature are compared, and the bipolar degradation mechanism of SiC MOSFET body diode at high temperature is analyzed.

[0078] By repeatedly subjecting bipolar devices to short-pulse current power cycling at both room temperature and high temperature and comparing their static characteristics, this study overcomes the limitations of DC current stress power cycling. It offers simple control, high reliability, and avoids thermal runaway by preventing continuous heat accumulation during testing. It also has no impact on package characteristics and can be conducted in high-temperature environments, improving aging efficiency and accelerating bipolar degradation. This provides a new degradation method for studying the bipolar degradation mechanism of SiC bipolar power devices at high temperatures and the dislocation defects in SiC materials. Furthermore, it improves the long-term reliability of SiC bipolar power devices and provides guidance for their development.

[0079] This application also implements the technical solution provided in the embodiments of this application. After generating a predetermined 1000A pulse current, during the test, SiC MOSFET module one and SiC MOSFET module two of the same model and packaging process are used to conduct repetitive short pulse current power cycling tests with continuous pulse time at room temperature and high temperature, respectively. Then, the static characteristics are tested to conduct bipolar degradation research. The specific test process is as follows:

[0080] Conduct a power cycling test on SiC MOSFET module one: After adjusting the 1000A pulse current, connect SiC MOSFET module one to a power semiconductor pulse current test equipment, as shown in Figure 6 (DUT location). Apply a reverse voltage between the gate and source. The specific voltage should be based on the values ​​given in the product manual's test conditions for the body diode forward voltage. Set a 1000A repetitive pulse current with a pulse duration of 20µs and a duty cycle of 2% for a cycle time of 1000h. Perform a repetitive pulse current power cycling test on the body diode of SiC MOSFET module one at room temperature. Remove the module after the set cycle time is reached.

[0081] Test the forward IV characteristic and on-resistance Rdson of the body diode of SiC MOSFET module one again, and compare the static characteristic degradation of the body diode before and after power cycling. If the body diode shows significant degradation, analyze the degradation mechanism. If the body diode does not show significant degradation, repeat the above power cycling test until the body diode shows significant degradation, and then analyze the degradation mechanism.

[0082] Conduct a power cycle test on SiC MOSFET module two: Place SiC MOSFET module two on a high-temperature heating platform, setting the platform to 125°C. Note that the temperature should not exceed the module's maximum case temperature of 175°C. Connect SiC MOSFET module two to a power semiconductor pulse current test device, applying a reverse voltage between the gate and source. The specific voltage should be based on the values ​​given in the product datasheet for the body diode's forward voltage test conditions. Set a 1000A repetitive pulse current with a pulse duration of 20µs and a duty cycle of 2%, and a cycle time of 1000 hours. Perform a repetitive pulse current power cycle test on the body diode of SiC MOSFET module two at a high temperature of 125°C. Remove the device after the set cycle time has elapsed.

[0083] Test the forward IV characteristic and on-resistance Rdson of the body diode of SiC MOSFET module 2 again, and compare the static characteristic degradation of the body diode before and after power cycling. If the body diode shows significant degradation, analyze the degradation mechanism. If the body diode does not show significant degradation, repeat the power cycling test above until the body diode shows significant degradation, and then analyze the degradation mechanism.

[0084] The degradation phenomena of the body diode of SiC MOSFET module 1 and SiC MOSFET module 2 are compared, the influence of temperature on the degradation phenomenon is analyzed, and the degradation mechanism is studied.

[0085] Tables 1 and 2 present the test data for this embodiment. After a repetitive pulsed current power cycling test at room temperature, the body diode of SiC MOSFET module one showed significant degradation in both its forward IV characteristic and on-resistance Rdson. Compared to the body diode of SiC MOSFET module one, under the same repetitive pulsed current, the same pulse time interval, and the same test time, the body diode of SiC MOSFET module two showed even greater degradation in its forward IV characteristic and on-resistance Rdson after a repetitive pulsed current power cycling test at a high temperature of 125°C. Based on the changes in the corresponding static characteristics, it can be concluded that the degradation of the body diodes in both cases is bipolar degradation. Furthermore, compared to DC current stress power cycling tests in other literature, neither SiC MOSFET module one nor SiC MOSFET module two exhibited package-related degradation.

[0086] Table 1. Static parameter test results of SiC MOSFET module before and after bipolar degradation test

[0087] Table 2. Static parameter test results of SiC MOSFET module before and after bipolar degradation test.

[0088] Compared to the DC current stress power cycling method, the high-temperature repetitive short-pulse current power cycling method eliminates the need for an external real-time junction temperature monitoring system and complex switching control. It offers simpler control, higher reliability, and avoids continuous heat accumulation during power cycling, thus preventing thermal runaway and having virtually no impact on package characteristics. Compared to the room-temperature repetitive short-pulse current power cycling method, the addition of a high-temperature factor improves aging efficiency and accelerates the occurrence of bipolar degradation in the SiC MOSFET body diode. This facilitates the analysis of its bipolar degradation mechanism, and the analysis results can effectively improve the long-term reliability of SiC bipolar power devices, enabling the development of reliable SiC bipolar power devices.

[0089] It should be understood that although the steps in the flowchart of Figure 1 are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in Figure 1 may include multiple steps or multiple stages, which are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps.

[0090] In some embodiments, the power semiconductor pulse current testing device provided in this application includes a drive circuit and a main circuit. The main circuit includes a first power switching device, a second power switching device, a third power switching device, an inductor, a resistor, and an electrolytic capacitor. The positive terminal of the electrolytic capacitor is connected to the power supply, and the negative terminal of the electrolytic capacitor is grounded.

[0091] The source of the third power switch is connected to the power supply after being connected in series with a resistor. The drain of the third power switch is connected to the drain of the second power switch. The source of the second power switch is connected to the drain of the first power switch after being connected in series with an inductor. The source of the second power switch is connected to the power supply. The source of the first power switch is grounded. The drains of the second power switch, the third power switch, and the first power switch serve as the access points for the SiC MOSFET module.

[0092] Specifically, the power semiconductor pulse current testing equipment can generate preset repetitive pulse current and pulse time. The power semiconductor pulse current testing equipment includes a drive circuit and a main circuit. The main circuit is designed according to the dual-pulse principle and includes multiple power switching devices, inductors and electrolytic capacitors. The gate voltage drive signal of each power switching device is a different PWM wave. The drive circuit is used to control the on and off of the power switching devices in the main circuit, so that different components in the main circuit form different circuits with the SiC MOSFET module under test.

[0093] As shown in Figure 6, the main circuit includes three power switching devices, namely power switching device Q1, power switching device Q2 and power switching device Q3, as well as an inductor L1, an electrolytic capacitor CE1 and a resistor R1.

[0094] The positive terminal of electrolytic capacitor CE1 is connected to the power supply, and the negative terminal of electrolytic capacitor CE1 is grounded. The source of power switch Q3 is connected to the power supply in series with resistor R1. The drain of power switch Q3 is connected to the drain of power switch Q2. The source of power switch Q2 is connected to the drain of power switch Q1 in series with inductor L1. The source of power switch Q2 is also connected to the power supply. The source of power switch Q1 is grounded. The drains of power switch Q2 and power switch Q3, and the drain of power switch Q1, serve as the access points for the SiC MOSFET module under test.

[0095] During testing, calculate and select appropriate capacitor CE1 and inductor L1 according to the following formula: V set =L·dI set / d t 1 / 2 C·V 2 set ·K=V set ·I set ·t

[0096] Where K is the allowable voltage drop percentage, ranging from 0.5% to 2%, and V set The set power supply voltage, d is the calculus symbol, I set For the set current, dI se =I se d t The pulse time is set, t = dt; L is the value of inductor L1, and C is the value of electrolytic capacitor CE1.

[0097] Because the pulse duration applied in the experiment was very short (on the order of microseconds), it can be considered as I set =dI set , t = dt;

[0098] In some embodiments, the drive circuit includes multiple single-channel isolated gate drivers, an on-resistor, an off-resistor, and a Schottky diode, wherein the single-channel isolated gate drivers are connected to a signal generator.

[0099] The single-channel isolated gate driver is connected to the signal generator via the first connector, the second connector, and the third connector, and is connected to the power supply via the fourth connector, the fifth connector, the sixth connector, and the seventh connector.

[0100] A single-channel isolated gate driver is used to isolate and amplify a small input signal of a specific frequency and pulse width to generate a signal that drives the diode.

[0101] Specifically, the drive circuit includes a single-channel isolated gate driver, an on-resistor, an off-resistor, and a Schottky diode. A signal generator or microcontroller inputs a small signal with a preset frequency and preset pulse width to the gate driver. After isolation and amplification by the gate driver, a signal sufficient to drive the SiC MOSFET under test is generated. Connectors X1, X2, and X3 are connected to the signal generator to provide different drive signals to the single-channel isolated gate driver at different stages. Connectors X4, X5, X6, X7, and X8 are connected to the power supply to provide the operating voltage to the single-channel isolated gate driver.

[0102] In some embodiments, a single-channel isolated gate driver is used to input a first drive signal with a first set frequency and a first set pulse width at a first connection point, and after isolation and amplification by the first single-channel isolated gate driver, output a drive signal to drive the first power switching device.

[0103] A second drive signal with a second set frequency and a second set pulse width is input at the second connector. After isolation and amplification by the second single-channel isolated gate driver, the drive signal of the second drive power switching device is output.

[0104] A third drive signal with a third set frequency and a third set pulse width is input at the third connector. After isolation and amplification by the third single-channel isolated gate driver, a drive signal for driving the third power switching device is output.

[0105] It is worth noting that the first connector refers to connector X1, the second connector refers to connector X2, and the third connector refers to connector X3.

[0106] Specifically, the driving circuit works as follows:

[0107] Phase 1: As shown in Figure 7, a small signal (PWM1) with a first set frequency and a first set pulse width is input at connector X1. After isolation and amplification by the single-channel isolated gate driver U1, a drive signal sufficient to drive the power switching device Q1 is output. Simultaneously, a low level is applied at connectors X2 and X3, and the single-channel isolated gate driver U2 and U3 are not operating. At this time, power switching device Q1 is in the operating state, while power switching devices Q2 and Q3 are in the off state.

[0108] Second stage: As shown in Figure 8, a small signal (PWM2) with a second set frequency and a second set pulse width is input at connector X2. After isolation and amplification by the single-channel isolated gate driver U2, a drive signal sufficient to drive switch Q1 is output. At the same time, a low level is applied at connectors X1 and X3, and the single-channel isolated gate driver U1 and U3 are not working. At this time, power switch Q2 is in the active state, while power switches Q1 and Q3 are in the off state.

[0109] The third stage: As shown in Figure 9, a small signal (PWM3) with a third set frequency and a third set pulse width is input at connector X3. After isolation and amplification by the single-channel isolated gate driver U3, a drive signal sufficient to drive switch Q3 is output. At the same time, a low level is applied at connectors X1 and X2, and the single-channel isolated gate driver U1 and U2 are not working. At this time, power switch Q3 is in the operating state, while power switches Q1 and Q2 are in the off state.

[0110] It should be noted that the first set frequency, the first set pulse width, the second set frequency, the second set pulse width, the third set frequency, and the third set pulse width are signal frequencies and pulse widths determined after testing.

[0111] In some embodiments, as shown in FIG10, a block diagram of a diode bipolar degradation test apparatus 1000 provided in this application embodiment is shown, including a power supply 1001, a power semiconductor pulse current test device 1002, and a SiC MOSFET module 1003. The SiC MOSFET module includes a first diode and a second diode. The power supply is connected to the power semiconductor pulse current test device, and the power semiconductor pulse current test device is connected to the SiC MOSFET module.

[0112] In some embodiments, the power semiconductor pulse current testing equipment is used to perform a repetitive short pulse current power cycle test on a first diode under normal temperature conditions and a repetitive short pulse current power cycle test on a second diode under high temperature conditions, based on the pulse test current, pulse test time, and pulse cycle time.

[0113] The SiC MOSFET module is used to perform repetitive short-pulse current power cycle tests under normal temperature conditions or under high temperature conditions, based on the pulse test current, pulse test time, and pulse cycle time.

[0114] The specific implementation of this diode bipolar degradation test device is basically the same as the specific implementation of the diode bipolar degradation test method described above, and will not be repeated here.

[0115] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0116] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method of testing a diode-bipolar degeneration, characterized by, The method comprises the following steps: respectively testing the static characteristics of the first diode and the second diode to obtain first static characteristic test results and second static characteristic test results; setting pulse test current, pulse test time and pulse cycle time, so that the power semiconductor pulse current test equipment performs repeated short pulse current power cycle test on the first diode under normal temperature conditions and performs repeated short pulse current power cycle test on the second diode under high temperature conditions according to the pulse test current, the pulse test time and the pulse cycle time; obtaining third static characteristic test results of the first diode after repeated short pulse current power cycle test and fourth static characteristic test results of the second diode after repeated short pulse current power cycle test; comparing the first static characteristic test results, the second static characteristic test results, the third static characteristic test results and the fourth static characteristic test results to obtain comparison results, and obtaining diode bipolar degradation test results according to the comparison results.

2. The method of claim 1, wherein the diode is a bipolar degeneration test diode. The method of testing the static characteristics of the first diode and the second diode comprises: testing the forward IV characteristics and the on-resistance Rdson of the first diode and the second diode.

3. The method of claim 1, wherein the step of applying a voltage to the diode includes applying a voltage to the diode that is less than the breakdown voltage of the diode. The pulse test current, the pulse test time and the pulse cycle time are obtained by using the power semiconductor pulse current test equipment, and the specific test process is as follows: applying a reverse voltage between the gate and the source of the to-be-tested diode, the second power switching device and the third power switching device, and applying a forward pulse voltage between the gate and the source of the first power switching device, so that the first power switching device, the inductor and the electrolytic capacitor form a first loop to obtain a first driving signal and a first pulse current, wherein the to-be-tested diode is a first to-be-tested diode or a second to-be-tested diode; after the forward pulse of the first power switching device, applying a forward pulse voltage between the gate and the source of the second power switching device, so that the to-be-tested diode, the inductor and the second power switching device form a second loop to obtain a second driving signal and a second pulse current; applying a forward pulse voltage between the gate and the source of the third power switching device to obtain a third driving signal, so that the to-be-tested diode, the third power switching device and the resistor form a third loop to obtain a third driving signal, and the power semiconductor pulse current test equipment is completely discharged, the pulse duration of the first driving signal is determined as the pulse test time, the pulse cycle time is obtained according to the pulse start time and the pulse end time of the first driving signal, the second driving signal and the third driving signal, and the pulse test current is determined according to the first pulse current, the second pulse current and the third pulse current.

4. The method of claim 3, wherein the diode is a bipolar degeneration test diode. After one test by using the power semiconductor pulse current test equipment, the method further comprises the following steps: recording single pulse IV characteristics, calculating the instantaneous temperature during single pulse current according to the pulse IV characteristics, and making the instantaneous temperature lower than the preset case temperature of the first diode or the second diode when performing repeated short pulse current power cycle test.

5. The method of claim 1, wherein the diode is a bipolar degeneration test diode. The pulse test time is 20us, and the pulse cycle time is 1000h-1500h.

6. A power semiconductor pulse current test apparatus characterized by comprising: The main circuit comprises a first power switching device, a second power switching device, a third power switching device, an inductor, a resistor and an electrolytic capacitor, the positive electrode of the electrolytic capacitor is connected to a power supply, and the negative electrode of the electrolytic capacitor is grounded, The source electrode of the third power switching device is connected to the power supply in series with the resistor, the drain electrode of the third power switching device is connected to the drain electrode of the second power switching device, the source electrode of the second power switching device is connected to the drain electrode of the first power switching device in series with the inductor, the source electrode of the second power switching device is connected to the power supply, the source electrode of the first power switching device is grounded, and the drain electrode of the second power switching device and the drain electrode of the third power switching device serve as the access point of the SiC MOSFET module.

7. The power semiconductor pulse current test apparatus according to claim 6, wherein The drive circuit comprises a plurality of single-channel isolated gate drivers, turn-on resistors, turn-off resistors and Schottky diodes, wherein the single-channel isolated gate drivers are connected to a signal generator, The single-channel isolated gate drivers are connected to the signal generator through first, second and third connectors, and are connected to a power supply through fourth, fifth, sixth and seventh connectors; The single-channel isolated gate drivers are used to isolate and amplify small signals of specific frequencies and specific pulse widths to generate signals for driving diodes to work.

8. The power semiconductor pulse current test apparatus according to claim 7, wherein The single-channel isolated gate drivers are used to input a first driving signal of a first set frequency and a first set pulse width at the first connection, isolate and amplify the first driving signal through the first single-channel isolated gate driver, and output a driving signal for driving the first power switching device; A second driving signal of a second set frequency and a second set pulse width is input at the second connector, isolated and amplified through the second single-channel isolated gate driver, and a driving signal for driving the second power switching device is output; A third driving signal of a third set frequency and a third set pulse width is input at the third connector, isolated and amplified through the third single-channel isolated gate driver, and a driving signal for driving the third power switching device is output.

9. A diode-bipolar degeneration test apparatus characterized by comprising: The power semiconductor pulse current test equipment is used to perform repeated short pulse current power cycle tests on the first diode under normal temperature conditions and perform repeated short pulse current power cycle tests on the second diode under high temperature conditions according to the pulse test current, the pulse test time and the pulse cycle time.

10. The diode double-dissipation test apparatus of claim 9, wherein, The power semiconductor pulse current test equipment is used to perform repeated short pulse current power cycle tests on the first diode under normal temperature conditions and perform repeated short pulse current power cycle tests on the second diode under high temperature conditions according to the pulse test current, the pulse test time and the pulse cycle time. The SiC MOSFET module is used to perform a repetitive short-pulse current power cycle test under normal temperature conditions or a repetitive short-pulse current power cycle test under high temperature conditions according to the pulse test current, the pulse test time, and the pulse cycle time.

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