Method and device for recovering SiC MOSFET threshold voltage under electron irradiation

Abstract

The invention provides a method and a device for recovering a threshold voltage of a SiC MOSFET under electron irradiation, and belongs to the field of threshold voltage recovery of a SiC MOSFET. The method comprises: fixing a SiC MOSFET bare chip to be recovered, and leading out each electrode of the SiC MOSFET bare chip to be recovered; performing electron irradiation on the SiC MOSFET bare chip to be recovered for several times continuously; after the electron irradiation, measuring the threshold voltage of the SiC MOSFET to be recovered, and when the actual threshold voltage is compared with the healthy threshold voltage, if the two are equal, stopping the electron irradiation on the SiC MOSFET bare chip to be recovered; otherwise, continuing to perform electron irradiation on the SiC MOSFET bare chip to be recovered; the invention realizes the recycling and reuse of the failed SiC MOSFET.

Description

Technical Field

[0001] The present invention belongs to the field of threshold voltage recovery of SiC MOSFET, and more specifically, relates to a method and device for recovering the threshold voltage of SiC MOSFET under electron irradiation. Background Art

[0002] In recent years, with the increasing maturity of technologies related to wide bandgap semiconductor materials, more and more power devices have begun to transform from Si-based to wide bandgap; as a type of wide bandgap material, SiC has the characteristics of large bandgap, high breakdown electric field strength, fast saturated electron drift velocity, high thermal conductivity and strong radiation resistance; SiC MOSFET (Silicon Carbide Metal Oxide Field-Effect Transistor) shows better application prospects than Si MOSFET in applications such as high voltage, high temperature, high switching frequency and strong radiation.

[0003] Compared with Si MOSFET, SiC MOSFET has obvious instability in threshold voltage due to the presence of high interface state traps at the SiC / SiO2 interface. Threshold voltage instability has become a key issue that hinders the widespread application of SiC MOSFET. Due to the excellent properties of SiC materials, SiC MOSFET is more suitable for working in high temperature environments than Si MOSFET, and SiC MOSFET will aggravate threshold voltage drift when repeatedly switched at high temperature. Positive drift of threshold voltage will lead to increased on-resistance and loss of the device, while negative drift will cause the device to be turned on incorrectly, resulting in failure of power electronic devices. If there is a difference in the threshold voltage of the series and parallel chips inside the high-voltage, high-current SiC MOSFET module, the chip that is turned on first will also have overvoltage or overcurrent failure due to the different opening speeds of each chip. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to provide a method and device for recovering the threshold voltage of SiC MOSFET under electron irradiation, aiming to solve the problem that the existing SiC MOSFET is prone to aging and the threshold voltage changes in a high temperature environment, which leads to failure of the SiC MOSFET and low utilization rate.

[0005] To achieve the above object, on the one hand, the present invention provides a method for recovering the threshold voltage of SiC MOSFET under electron irradiation, comprising the following steps:

[0006] Fixing the SiC MOSFET bare chip to be restored, and leading out each electrode of the SiC MOSFET bare chip to be restored;

[0007] The SiC MOSFET bare chip to be restored is subjected to several consecutive electron irradiations, and the electron energy is selected to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored;

[0008] During the electron irradiation process, the drain and gate of the SiC MOSFET to be restored are short-circuited, and the actual threshold voltage is measured. When the actual threshold voltage is compared with the healthy threshold voltage, if the two are equal, the electron irradiation of the SiC MOSFET bare chip to be restored is stopped; otherwise, the electron irradiation of the SiC MOSFET bare chip to be restored continues;

[0009] Among them, the healthy threshold voltage is the threshold voltage of the SiC MOSFET chip in a normal state; the threshold voltage of the SiC MOSFET to be restored before electron irradiation is greater than the healthy threshold voltage.

[0010] Preferably, when experimentally verifying the method for recovering the threshold voltage of SiC MOSFET under electron irradiation, the SiC MOSFET bare chip to be recovered is a SiC MOSFET that has been subjected to high-temperature positive gate bias.

[0011] Preferably, the high temperature positive gate bias method comprises the following steps:

[0012] The drain and source of the SiC MOSFET bare chip in a normal state are short-circuited and placed in a temperature chamber;

[0013] When the temperature of the oven rises to the set temperature, a positive bias voltage is applied to the gate and the aging process continues for the preset time;

[0014] The aged SiC MOSFET bare chip is cooled by short-circuiting the gate and source. The cooling time is such that the threshold voltage of the SiC MOSFET bare chip no longer changes, thereby completing the high-temperature positive gate bias treatment of the SiC MOSFET.

[0015] Preferably, the method for obtaining the healthy threshold voltage is:

[0016] The drain and gate of the SiC MOSFET in a normal state are short-circuited to obtain the gate-source voltage of the SiC MOSFET in the normal state as a healthy threshold voltage; wherein the SiC MOSFET in the normal state and the SiC MOSFET to be restored belong to the same SiC MOSFET.

[0017] Preferably, Al bonding wires are used to lead out the electrodes of the SiC MOSFET bare chip to be restored.

[0018] Preferably, the electron irradiation method is:

[0019] The SiC MOSFET bare chip to be restored is subjected to several consecutive electron irradiations using an EBL device. The dose of each irradiation is equal and the electron energy is selected to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored.

[0020] On the other hand, the present invention provides a SiC MOSFET threshold voltage recovery device under electron irradiation, comprising:

[0021] An electrode lead-out module, used to fix the SiC MOSFET bare chip to be restored and lead out each electrode of the SiC MOSFET bare chip to be restored;

[0022] An electron irradiation module, used for performing several consecutive electron irradiations on the SiC MOSFET bare chip to be restored, and selecting the electron energy to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored;

[0023] The threshold voltage recovery test module is used to short-circuit the drain and gate of the SiC MOSFET to be recovered during the electron irradiation process, measure the actual threshold voltage, and when the actual threshold voltage is compared with the healthy threshold voltage, if the two are equal, stop the electron irradiation of the SiC MOSFET bare chip to be recovered; otherwise, continue to perform electron irradiation on the SiC MOSFET bare chip to be recovered;

[0024] Among them, the healthy threshold voltage is the threshold voltage of the SiC MOSFET chip in a normal state; the threshold voltage of the SiC MOSFET to be restored before electron irradiation is greater than the healthy threshold voltage.

[0025] Preferably, when experimentally verifying the SiC MOSFET threshold voltage recovery device under electron irradiation, the SiC MOSFET bare chip to be recovered is a SiC MOSFET that has been subjected to high-temperature positive gate bias.

[0026] Preferably, the high temperature positive gate bias method comprises the following steps:

[0027] The drain and source of the SiC MOSFET bare chip in a normal state are short-circuited and placed in a temperature chamber;

[0028] When the temperature of the oven rises to the set temperature, a positive bias voltage is applied to the gate and the aging process continues for the preset time;

[0029] The aged SiC MOSFET bare chip is cooled by short-circuiting the gate and source. The cooling time is such that the threshold voltage of the SiC MOSFET bare chip no longer changes, thereby completing the high-temperature positive gate bias treatment of the SiC MOSFET.

[0030] Preferably, the method for obtaining the healthy threshold voltage is:

[0031] The drain and gate of the SiC MOSFET in a normal state are short-circuited to obtain the gate-source voltage of the SiC MOSFET in the normal state as a healthy threshold voltage; wherein the SiC MOSFET in the normal state and the SiC MOSFET to be restored belong to the same SiC MOSFET.

[0032] Preferably, Al bonding wires are used to lead out the electrodes of the SiC MOSFET bare chip to be restored.

[0033] Preferably, the electron irradiation method is:

[0034] The SiC MOSFET bare chip to be restored is subjected to several consecutive electron irradiations using an EBL device. The dose of each irradiation is equal and the electron energy is selected to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored.

[0035] In general, the above technical solution conceived by the present invention has the following beneficial effects compared with the prior art:

[0036] Because the gate of SiC MOSFET is in a high-speed switching state in actual work, its gate oxide is degraded. The most intuitive manifestation is that the threshold voltage of SiC MOSFET will drift. Once the threshold voltage drifts, the SiC MOSFET fails and cannot be used. Based on the above problem, since the threshold voltage of SiC MOSFET will change with the cumulative radiation dose, the present invention provides an electron irradiation experiment for processing the failed SiC MOSFET. After the electron irradiation treatment, the threshold voltage of the failed SiC MOSFET can be restored to a healthy threshold voltage, so that the SiC MOSFET can continue to be used, thereby realizing the recycling and reuse of the failed SiC MOSFET.

[0037] When experimentally verifying the SiC MOSFET threshold voltage recovery method under electron irradiation of the present invention, the present invention ages the gate oxide to different degrees through high-temperature gate bias. Since this process will impose electrical stress and thermal stress on the SiC MOSFET gate oxide, high-temperature gate bias can be used to simulate the working environment of the SiC MOSFET, and then an electron irradiation experiment is carried out to extract and analyze the changes in the electrical characteristics of the SiC MOSFET, thereby providing strong support for the recovery of the threshold voltage under electron irradiation.

[0038] In order to prevent the aging of packaging materials such as epoxy resin or silicone gel at high temperature from affecting the SiC MOSFET chip and shielding the electron beam under electron irradiation, the SiC MOSFET bare chip is welded on DBC (Direct Bonding Copper), and the electrodes of the chip are led out to four terminals through Al bonding wires. No other potting materials are added, so that electron irradiation can have a more precise effect on the SiC MOSFET. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1( a ) is a schematic diagram of a high temperature gate bias in a stress application stage provided by an embodiment of the present invention;

[0040] FIG1( b ) is a schematic diagram of a high temperature gate bias in a cooling stage provided by an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the threshold voltage measurement principle provided by an embodiment of the present invention;

[0042] Figure 3 It is a schematic diagram of the change between the threshold voltage change and the cumulative irradiation dose under electron irradiation provided by an embodiment of the present invention;

[0043] Figure 4 Schematic diagram of electron irradiation on a SiC MOSFET bare chip provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] In one aspect, the present invention provides a method for recovering a threshold voltage of a SiC MOSFET under electron irradiation, comprising the following steps:

[0046] Fixing the SiC MOSFET bare chip to be restored, and leading out each electrode of the SiC MOSFET bare chip to be restored;

[0047] The SiC MOSFET bare chip to be restored is subjected to several consecutive electron irradiations, and the electron energy is selected to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored;

[0048] After electron irradiation, the drain and gate of the SiC MOSFET to be restored are short-circuited, and the actual threshold voltage is measured. When the actual threshold voltage is compared with the healthy threshold voltage, if the two are equal, the electron irradiation of the SiC MOSFET bare chip is stopped; otherwise, the electron irradiation of the SiC MOSFET bare chip continues;

[0049] Among them, the healthy threshold voltage is the threshold voltage of the SiC MOSFET chip in a normal state; the threshold voltage of the SiC MOSFET to be restored before electron irradiation is greater than the healthy threshold voltage.

[0050] Preferably, when experimentally verifying the SiC MOSFET threshold voltage recovery method, the SiC MOSFET bare chip to be recovered is a SiC MOSFET that has been subjected to high-temperature positive gate bias.

[0051] Preferably, the high temperature positive gate bias method is: the drain and source of the SiC MOSFET bare chip in a normal state are short-circuited and then placed in a temperature box;

[0052] When the temperature of the oven rises to the set temperature, a positive bias voltage is applied to the gate and the aging process continues for the preset time;

[0053] The aged SiC MOSFET bare chip is cooled by short-circuiting the gate and source. The cooling time is such that the threshold voltage of the SiC MOSFET bare chip no longer changes, thereby completing the high-temperature positive gate bias treatment of the SiC MOSFET.

[0054] Preferably, the method for obtaining the healthy threshold voltage is:

[0055] The drain and gate of the SiC MOSFET in a normal state are short-circuited to obtain the gate-source voltage of the SiC MOSFET as a healthy threshold voltage; wherein the SiC MOSFET in a normal state and the SiC MOSFET to be restored belong to the same SiC MOSFET;

[0056] Preferably, Al bonding wires are used to lead out the electrodes of the SiC MOSFET chip to be restored;

[0057] Preferably, the electron irradiation method is:

[0058] The SiC MOSFET bare chip to be restored is subjected to several consecutive electron irradiations using an EBL device. The dose of each irradiation is equal and the electron energy is selected to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored.

[0059] On the other hand, the present invention provides a SiC MOSFET threshold voltage recovery device under electron irradiation, comprising:

[0060] An electrode lead-out module, used to fix the SiC MOSFET bare chip to be restored and lead out each electrode of the SiC MOSFET bare chip to be restored;

[0061] An electron irradiation module, used for performing several consecutive electron irradiations on the SiC MOSFET bare chip to be restored, and selecting the electron energy to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored;

[0062] The threshold voltage recovery test module is used to short-circuit the drain and gate of the SiC MOSFET to be recovered during the electron irradiation process, measure the actual threshold voltage, and when the actual threshold voltage is compared with the healthy threshold voltage, if the two are equal, stop the electron irradiation of the SiC MOSFET bare chip to be recovered; otherwise, continue to perform electron irradiation on the SiC MOSFET bare chip to be recovered;

[0063] Among them, the healthy threshold voltage is the threshold voltage of the SiC MOSFET chip in a normal state; the threshold voltage of the SiC MOSFET to be restored before electron irradiation is greater than the healthy threshold voltage.

[0064] Preferably, when experimentally verifying the SiC MOSFET threshold voltage recovery device under electron irradiation, the SiC MOSFET bare chip to be recovered is a SiC MOSFET that has been subjected to high-temperature positive gate bias.

[0065] Preferably, the high temperature positive gate bias method comprises the following steps:

[0066] The drain and source of the SiC MOSFET bare chip in a normal state are short-circuited and placed in a temperature chamber;

[0067] When the temperature of the oven rises to the set temperature, a positive bias voltage is applied to the gate and the aging process continues for the preset time;

[0068] The aged SiC MOSFET bare chip is cooled by short-circuiting the gate and source. The cooling time is such that the threshold voltage of the SiC MOSFET bare chip no longer changes, thereby completing the high-temperature positive gate bias treatment of the SiC MOSFET.

[0069] Preferably, the method for obtaining the healthy threshold voltage is:

[0070] The drain and gate of the SiC MOSFET in a normal state are short-circuited to obtain the gate-source voltage of the SiC MOSFET in the normal state as a healthy threshold voltage; wherein the SiC MOSFET in the normal state and the SiC MOSFET to be restored belong to the same SiC MOSFET.

[0071] Preferably, Al bonding wires are used to lead out the electrodes of the SiC MOSFET bare chip to be restored.

[0072] Preferably, the electron irradiation method is:

[0073] The SiC MOSFET bare chip to be restored is subjected to several consecutive electron irradiations using an EBL device. The dose of each irradiation is equal and the electron energy is selected to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored.

[0074] Example

[0075] This embodiment provides a method for recovering the threshold voltage of a SiC MOSFET under electron irradiation, comprising the following steps:

[0076] (1) Preparation: Pre-treatment of SiC MOSFET

[0077] In order to prevent the aging of packaging materials such as epoxy resin or silicone gel at high temperature from affecting the SiC MOSFET chip and shielding the electron beam under electron irradiation, the SiC MOSFET bare chip is welded on DBC (Direct Bonding Copper), and the electrodes of the chip are led out to four terminals, namely the gate G, drain D, source S and Kelvin source KS, through Al bonding wires. No other potting materials are added. The parameters of the tested SiC MOSFET chip are 1200V 42A 80mΩ; specifically: the maximum drain-source voltage is 1200V; the maximum drain-source current is 42A; the on-resistance between the drain and source is 80mΩ;

[0078] (2) Experiment on high temperature gate bias

[0079] There is no reliable test for SiC MOSFET at present. Rohm uses JEITA ED-4701 / 100A-101A to test the gate oxide reliability of semiconductor devices. It can be seen from the test that high temperature gate bias has a great impact on the gate oxide of SiCMOSFET, and high electric field and high temperature stress will accelerate the aging of gate oxide.

[0080] This time, high temperature gate bias is used to accelerate the oxidation of gate oxide. The principle is shown in Figure 1(a). During the test, the drain and source are short-circuited, and the gate bias voltage is applied after the temperature of the incubator is raised to the set temperature. The set temperature is generally higher than room temperature and does not exceed 150°C.

[0081] Since the device degradation caused by the high-temperature gate bias experiment is recoverable to a certain extent, the gate and source of the device are short-circuited when cooling the device, as shown in Figure 1(b) to avoid the influence of recoverable degradation on the experimental results. The cooling time is set until the threshold voltage no longer changes;

[0082] According to the WolfSpeed ​​test results, in the high-temperature gate bias experiment, the greater the gate voltage, the lower the lifespan;

[0083] In order to age the gate oxide to different degrees without gate oxide breakdown and reduce the aging time, this aging experiment uses a high electric field stress method. The gate oxide aging mechanism under high electric field stress is also applicable to low electric field stress conditions;

[0084] like Figure 4 As shown, this embodiment uses a self-shielded low-energy electron beam source EBLab-200ebeam Technologies to perform electron irradiation experiments on SiC MOSFET bare chips. The electron energy is 0.2MeV, and multiple irradiations are performed, each time at the same irradiation dose, 10 2 ~10 3 Krad can cover most space application scenarios;

[0085] Electron irradiation mainly affects the gate oxide of SiC MOSFET, and the incident depth of 0.2MeV electrons in SiC material can reach 62.5μm, indicating that the electron beam can penetrate the gate oxide and affect it;

[0086] In order to better understand the influence of different degrees of gate oxide aging on the electron irradiation resistance of SiC MOSFET under 0.2MeV electron irradiation, an experimental scheme as shown in Table 1 was set up. First, the healthy device was irradiated, such as #1; in order to accelerate the aging of the gate oxide and ensure that the gate oxide is not broken down, the gate bias voltages of 39V, 30V and -10V were applied during the high-temperature gate bias experiment; #2 and #3 first carried out the high-temperature positive gate bias experiment and then the electron irradiation experiment; among them, #2 applied the gate bias voltage of 39V; #3 applied the gate bias voltage of 30V; #4 first carried out the high-temperature negative gate bias experiment and then the electron irradiation experiment, among which #4 applied the gate bias voltage of -10V; the irradiation doses of the four devices were the same;

[0087] Table 1

[0088]

[0089] When measuring the threshold voltage, the device drain and gate are short-circuited, and the gate-source voltage V is measured when the drain current is 3.9 mA. gs When is the threshold voltage, the measurement principle is as follows Figure 2As shown, the average threshold voltage of the four devices in the initial state is 3.36V; the devices are processed using the above-mentioned high temperature gate bias conditions;

[0090] When 0.2MeV electrons are irradiated at different doses, the threshold voltage measurement results of the four devices are as follows: Figure 3 As shown, ΔV at 0 kGy th is the threshold voltage change caused by the high-temperature gate bias experiment; the threshold voltages of the four devices all decrease with the electron irradiation dose and then basically saturate; #2 and #3 show that electron irradiation can offset the positive drift of the threshold voltage introduced by the high-temperature positive gate bias, but the irradiation dose that completely offsets it is difficult to determine; for #2, under the irradiation dose of 300kGy, the threshold voltage of the device has basically recovered to the initial value; for #3, its irradiation dose can offset the positive offset of the threshold voltage caused by the high-temperature gate bias at a dose less than 4kGy; for #4, electron irradiation will reduce the threshold voltage again after the high-temperature negative gate bias.

[0091] Compared with the prior art, the present invention has the following advantages:

[0092] Because the gate of SiC MOSFET is in a high-speed switching state in actual work, its gate oxide is degraded. The most intuitive manifestation is that the threshold voltage of SiC MOSFET will drift. Once the threshold voltage drifts, the SiC MOSFET fails and cannot be used. Based on the above problem, since the threshold voltage of SiC MOSFET will change with the cumulative radiation dose, the present invention provides an electron irradiation experiment for processing the failed SiC MOSFET. After the electron irradiation treatment, the threshold voltage of the failed SiC MOSFET can be restored to a healthy threshold voltage, so that the SiC MOSFET can continue to be used, thereby realizing the recycling and reuse of the failed SiC MOSFET.

[0093] When the reliability of the SiC MOSFET threshold voltage recovery method under electron irradiation of the present invention is verified, the present invention ages the gate oxide to different degrees through high-temperature gate bias. Since this process will apply electrical stress and thermal stress to the SiC MOSFET gate oxide, the high-temperature gate bias can be used to simulate the working environment of the SiC MOSFET, and then an electron irradiation experiment is carried out to extract and analyze the changes in the electrical characteristics of the SiC MOSFET, thereby providing strong support for the recovery of the threshold voltage under electron irradiation.

[0094] In order to prevent the aging of packaging materials such as epoxy resin or silicone gel at high temperature from affecting the SiC MOSFET chip and shielding the electron beam under electron irradiation, the SiC MOSFET bare chip is welded on DBC (Direct Bonding Copper), and the electrodes of the chip are led out to four terminals through Al bonding wires. No other potting materials are added, so that electron irradiation can have a more precise effect on the SiC MOSFET.

[0095] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for restoring the threshold voltage of SiC MOSFET under electron irradiation, characterized in that: The following steps are involved: Fixing the SiC MOSFET bare chip to be restored, and leading out each electrode of the SiC MOSFET bare chip to be restored; Performing electron irradiation on the SiC MOSFET bare chip to be restored for several times continuously, and selecting the electron energy to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored; After the electron irradiation, the drain and gate of the SiC MOSFET to be restored are short-circuited, and the actual threshold voltage is measured. When the actual threshold voltage is compared with the healthy threshold voltage, if the two are equal, the electron irradiation of the SiC MOSFET bare chip to be restored is stopped; otherwise, the electron irradiation of the SiC MOSFET bare chip to be restored continues; The healthy threshold voltage is the threshold voltage of the SiC MOSFET chip in a normal state; the threshold voltage of the SiC MOSFET to be restored before electron irradiation is greater than the healthy threshold voltage.

2. The method for recovering the threshold voltage of SiC MOSFET under electron irradiation according to claim 1, characterized in that: When experimentally verifying the above, the SiC MOSFET bare chip to be restored is a SiC MOSFET that has been subjected to high-temperature positive gate bias.

3. The method for recovering the threshold voltage of SiC MOSFET under electron irradiation according to claim 2, characterized in that: The high temperature positive gate bias method comprises the following steps: The drain and source of the SiC MOSFET bare chip in a normal state are short-circuited and placed in a temperature chamber; When the temperature of the incubator rises to a set temperature, a positive bias voltage is applied to the gate for a preset aging time; The aged SiC MOSFET bare chip is cooled by short-circuiting the gate and source. The cooling time is such that the threshold voltage of the SiC MOSFET bare chip no longer changes, thereby completing the high-temperature positive gate bias treatment of the SiC MOSFET.

4. The method for recovering the threshold voltage of SiC MOSFET under electron irradiation according to any one of claims 1 to 3, characterized in that: The method for obtaining the healthy threshold voltage is: The drain and gate of the SiC MOSFET in a normal state are short-circuited to obtain the gate-source voltage of the SiC MOSFET in the normal state as a healthy threshold voltage; wherein the SiC MOSFET in the normal state and the SiC MOSFET to be restored belong to the same SiC MOSFET.

5. The method for recovering the threshold voltage of SiC MOSFET under electron irradiation according to claim 1, characterized in that: Al bonding wires are used to lead out the electrodes of the SiC MOSFET bare chip to be restored.

6. The method for recovering the threshold voltage of SiC MOSFET under electron irradiation according to claim 1 or 5, characterized in that: The electron irradiation method is: The SiC MOSFET bare chip to be restored is subjected to several consecutive electron irradiations using an EBL device. The dose of each irradiation is equal and the electron energy is selected to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored.

7. A SiC MOSFET threshold voltage recovery device under electron irradiation, characterized in that: include: An electrode lead-out module, used to fix the SiC MOSFET bare chip to be restored and lead out each electrode of the SiC MOSFET bare chip to be restored; An electron irradiation module, used for performing several consecutive electron irradiations on the SiC MOSFET bare chip to be restored, and selecting the electron energy to ensure that the electrons can be incident on the gate oxide of the SiC MOSFET bare chip to be restored; A threshold voltage recovery test module is used to short-circuit the drain and gate of the SiC MOSFET to be restored after electron irradiation, measure the actual threshold voltage, and when the actual threshold voltage is compared with the healthy threshold voltage, if the two are equal, stop electron irradiation of the SiC MOSFET bare chip to be restored; otherwise, continue electron irradiation of the SiC MOSFET bare chip to be restored; The healthy threshold voltage is the threshold voltage of the SiC MOSFET chip in a normal state; the threshold voltage of the SiC MOSFET to be restored before electron irradiation is greater than the healthy threshold voltage.

8. The device for recovering the threshold voltage of SiC MOSFET under electron irradiation according to claim 7, characterized in that: When experimentally verifying the above, the SiC MOSFET bare chip to be restored is a SiC MOSFET that has been subjected to high-temperature positive gate bias.

9. The device for recovering the threshold voltage of SiC MOSFET under electron irradiation according to claim 8, characterized in that: The high temperature positive gate bias method comprises the following steps: The drain and source of the SiC MOSFET bare chip in a normal state are short-circuited and placed in a temperature chamber; When the temperature of the incubator rises to a set temperature, a positive bias voltage is applied to the gate for a preset aging time; The aged SiC MOSFET bare chip is cooled by short-circuiting the gate and source. The cooling time is such that the threshold voltage of the SiC MOSFET bare chip no longer changes, thereby completing the high-temperature positive gate bias treatment of the SiC MOSFET.

10. The method for recovering the threshold voltage of SiC MOSFET under electron irradiation according to any one of claims 7 to 9, characterized in that: The method for obtaining the healthy threshold voltage is: The drain and gate of the SiC MOSFET in a normal state are short-circuited to obtain the gate-source voltage of the SiC MOSFET in the normal state as a healthy threshold voltage; wherein the SiC MOSFET in the normal state and the SiC MOSFET to be restored belong to the same SiC MOSFET.

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