Silicon carbide power MOSFET early failure screening method and system
The gate detection voltage and temperature are determined by current-voltage scanning and temperature screening methods. Combined with carrier mobility analysis, this solves the problem of insufficient screening strength in existing technologies, achieves efficient screening of early failures of silicon carbide power MOSFETs, and improves device reliability.
Patent Information
- Application Number
- CN202510981479.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-16
- Publication Date
- 2025-10-17
AI Technical Summary
Existing screening methods are insufficient for early-stage gate oxide failures in silicon carbide power MOSFETs and are unable to effectively identify devices with long 'non-intrinsic' failure times, leading to potential failure hazards.
The gate detection voltage and screening temperature are determined by current-voltage scanning. Combined with the carrier low-field mobility and temperature relationship curve, the gate leakage current is detected to determine early oxide failure, and more extreme voltage and temperature screening conditions are adopted.
Without compromising device reliability, the screening effort is enhanced, enabling rapid identification and screening of high-risk early oxide failure devices to ensure product reliability.
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Figure CN120801975A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of power tube quality inspection, in particular to a silicon carbide power MOSFET early failure screening method and system. BACKGROUND
[0002] The reliability of commercial silicon carbide (SiC) power MOSFET widely used in industrial and automotive applications faces a key challenge: early breakdown of the gate oxide layer. This is mainly due to the easy introduction or residual impurity defects in the gate oxide layer during the manufacturing process. Such defects constitute a weak point of the electric field, significantly reducing the intrinsic dielectric strength of the oxide layer, which may cause irreversible breakdown failure under normal operating voltage or accelerated stress conditions. This early failure is unrelated to the inherent life of the device, and is the main problem restricting the long-term stable operation of SiC MOSFET in actual harsh working conditions (such as high temperature and high power density).
[0003] In order to identify and eliminate SiC power MOSFET devices with potential early gate oxide failure risks before they are shipped, the industry usually adopts screening methods based on electrical stress acceleration. The core idea is to accelerate the exposure process of hidden defects (such as impurities, traps, and weak points) in the gate oxide layer under the conditions of applying a stress higher than the normal operating voltage (Vstress), increasing the environmental temperature (T), and maintaining a certain test time (t). Those devices containing serious defects will break down within a predetermined time, thus being screened out, aiming to ensure the reliability of the delivered products.
[0004] However, the above mainstream screening methods face significant technical limitations in practice. The effectiveness of these methods is constrained by the "voltage-temperature-time" three elements, resulting in the inability to completely eliminate the "non-intrinsic failure tail". Especially when the failure time distribution is close to the edge of the SiC intrinsic, truly aging-induced TDDB (Time Dependent Dielectric Breakdown, long-term dielectric breakdown test) failure region, the screening intensity of the existing screening methods is severely insufficient. Therefore, some devices with longer but still "non-intrinsic" failure times (i.e., devices with relatively mild defects but not enough to fail under shorter time / lower stress) may "survive" in the screening process and cannot be effectively identified. These "slippery fish" once flow into the market, deployed in critical positions such as the power system of electric vehicles (EV), will pose a potential failure risk, bringing unpredictable safety risks and high after-sales service costs to actual industrial applications. SUMMARY
[0005] The problem to be solved by the present application is that the screening intensity of the existing screening means is seriously insufficient, and some devices with a relatively long "non-intrinsic" invalidation time cannot be screened out.
[0006] To solve the above problems, in a first aspect, the present application provides a silicon carbide power MOSFET early failure screening method, comprising:
[0007] According to the specification information and the gate oxide layer thickness of the silicon carbide power MOSFET, the gate detection voltage is determined by a current-voltage scanning method.
[0008] According to the relationship curve of the drain current and the gate voltage at different temperatures, the relationship curve of the low-field mobility of the carrier of the silicon carbide power MOSFET and the temperature is analyzed to determine the screening temperature.
[0009] At the screening temperature, the gate detection voltage is applied to the silicon carbide power MOSFET to be tested for a preset time, and the gate leakage current is detected.
[0010] If the gate leakage current is greater than the current threshold value, it is determined that the silicon carbide power MOSFET to be tested has a high risk of early oxide failure and is screened out.
[0011] Optionally, the determination of the gate detection voltage according to the specification information and the gate oxide layer thickness of the silicon carbide power MOSFET by the current-voltage scanning method comprises
[0012] According to the specification information and the gate oxide layer thickness of the silicon carbide power MOSFET, the initial gate scanning voltage is set.
[0013] Starting from the initial gate scanning voltage, the gate scanning voltage applied to the silicon carbide power MOSFET is gradually increased, and the gate leakage current corresponding to each gate scanning voltage is detected every time the gate scanning voltage is applied for a preset time. It is determined whether the gate leakage current is close to the preset leakage current, wherein when the gate leakage current is within the fluctuation range based on the preset leakage current or the gate leakage current is unchanged for a plurality of times, the gate leakage current is considered to be close to the preset leakage current.
[0014] When the gate leakage current is not close to the preset leakage current, the gate scanning voltage is continuously increased.
[0015] When the gate leakage current is close to the preset leakage current, the last gate scanning voltage is taken as the gate detection voltage.
[0016] Optionally, the determination of the screening temperature according to the relationship curve of the drain current and the gate voltage at different temperatures and the analysis of the change curve of the low-field mobility of the carrier of the silicon carbide power MOSFET and the temperature comprises:
[0017] Linear fitting is performed on the curve of drain current and gate voltage to obtain the low-field mobility of the carrier of the silicon carbide power MOSFET;
[0018] The peak value of the curve is taken as the screening temperature.
[0019] Optionally, when the silicon carbide power MOSFET to be measured is a 1200V SiC power MOSFET, the gate detection voltage is 40V, the screening temperature is 170℃, the preset time is 100ms, and the current threshold is 10uA.
[0020] Optionally, when the silicon carbide power MOSFET to be measured is a 1200V SiC power MOSFET, the initial gate scanning voltage is 30V, the preset time is in the range of 1ms-500ms, and the preset leakage current is 1uA.
[0021] In a second aspect, the present application further provides a silicon carbide power MOSFET early failure screening system, comprising:
[0022] A gate detection voltage analysis module is configured to determine the gate detection voltage by means of current-voltage scanning according to the specification information of the silicon carbide power MOSFET and the gate oxide layer thickness.
[0023] A screening temperature analysis module is configured to determine the screening temperature by analyzing the relationship curve between the low-field mobility of the carrier of the silicon carbide power MOSFET and the temperature according to the relationship curve between the drain current and the gate voltage at different temperatures.
[0024] A detection module is configured to apply the gate detection voltage on the silicon carbide power MOSFET to be measured for a preset time at the screening temperature, and detect the gate leakage current.
[0025] A screening module is configured to determine that the silicon carbide power MOSFET to be measured has a high-risk early oxide failure if the gate leakage current is greater than the current threshold, and to be screened out.
[0026] Optionally, the gate detection voltage analysis module comprises:
[0027] An initial gate scanning voltage is set according to the specification information of the silicon carbide power MOSFET and the gate oxide layer thickness.
[0028] Start from an initial gate scanning voltage, gradually increase the gate scanning voltage applied on the silicon carbide power MOSFET, the application time of each gate scanning voltage is a preset time length, detect the gate leakage current corresponding to each gate scanning voltage, and judge whether the gate leakage current is close to the preset leakage current, wherein, when the gate leakage current is within the fluctuation range based on the preset leakage current, or the gate leakage current is unchanged for a plurality of times, the gate leakage current is considered to be close to the preset leakage current;
[0029] When the gate leakage current is not close to the preset leakage current, the gate scanning voltage is continuously increased;
[0030] When the gate leakage current is close to the preset leakage current, the last gate scanning voltage is taken as the gate detection voltage.
[0031] Optionally, the screening temperature analysis module comprises:
[0032] Linear fitting is performed on the relationship curve of the drain current and the gate voltage to obtain the low-field mobility of the silicon carbide power MOSFET carrier.
[0033] The relationship curve of the low-field mobility and the temperature is analyzed, and the temperature corresponding to the peak value of the curve is taken as the screening temperature.
[0034] The present application provides a kind of silicon carbide power MOSFET early failure screening method and system.Compared with prior art, it has the following beneficial effects:
[0035] According to the specification information and the gate oxide layer thickness of the silicon carbide power MOSFET, the gate detection voltage is determined by current-voltage scanning mode;According to the relationship curve of the drain current and the gate voltage at different temperatures, the relationship curve of the low-field mobility of the silicon carbide power MOSFET carrier and the temperature is analyzed, and the screening temperature is determined;Without damaging the silicon carbide power MOSFET, the more extreme gate detection voltage and screening temperature are determined, the gate detection voltage and screening temperature are applied to the silicon carbide power MOSFET to be tested, and the gate leakage current is detected, if the gate leakage current is greater than the current threshold, it is determined that the silicon carbide power MOSFET to be tested has high risk early oxide failure, and is screened out.The method detects the silicon carbide power MOSFET to be tested with more extreme gate detection voltage and screening temperature, and the reliability of the normal device is not damaged, the screening strength is stronger, and the method is convenient and fast, and has certain universality. BRIEF DESCRIPTION OF DRAWINGS
[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.
[0037] Figure 1 A gate leakage current measurement value distribution diagram provided by the prior screening method for the embodiments of the present application;
[0038] Figure 2 A Weibull diagram of oxide layer failure time of a sample provided by the embodiments of the present application;
[0039] Figure 3 A relationship diagram between initial gate leakage current and oxide layer failure time of SiC power MOSFET in TDDB test provided by the embodiments of the present application;
[0040] Figure 4 A flowchart of a silicon carbide power MOSFET early failure screening method provided by the embodiments of the present application;
[0041] Figure 5 A relationship diagram between gate leakage current and gate scanning voltage provided by the embodiments of the present application;
[0042] Figure 6 A relationship curve diagram between drain current and gate voltage provided by the embodiments of the present application;
[0043] Figure 7 A relationship curve diagram between low field mobility and temperature provided by the embodiments of the present application;
[0044] Figure 8 A correlation diagram between oxide layer lifetime under 38V and gate leakage current at 40V provided by the embodiments of the present application;
[0045] Figure 9 A structure diagram of a silicon carbide power MOSFET early failure screening system provided by the embodiments of the present application. DETAILED DESCRIPTION
[0046] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.
[0047] In the actual test, 40 samples were randomly selected and their gate leakage current values (Igss) were measured. Figure 1 As shown, it can be found that the sample measurement values are all within the normal range (gate-source leakage current MAX=300 in Table 1). Figure 2 The gate oxide failure distribution of SiC power MOSFETs at a gate voltage of 38V is shown. Based on the Weibull plot of oxide failure time for 40 samples, it can be observed that the intrinsic lifetime distribution of 38 samples is tight, with a Weibull slope of approximately 4. The two devices highlighted have experienced extrinsic failures. This indicates that even for devices with parameter values within the normal range, a small number of defective devices will fail prematurely. This also shows that the existing screening methods are not strong enough, and the screening method of this application is needed to quickly locate devices with long extrinsic failure tails.
[0048] By extracting the initial gate leakage current and oxide failure time of each device from a large number of TDDB test results, Figure 3 As shown in the figure, the oxide lifetime is negatively correlated with the initial gate leakage current. The higher the initial oxide current, the shorter the oxide failure time. This means that devices with higher gate leakage current have shorter oxide lifetimes. Conventional TDDB measurement and screening consumes a large number of device samples and measurement time, and cannot exclude devices at risk of early failure.
[0049] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.
[0050] like Figure 4 As shown, an embodiment of the present application provides a method for screening early failure of silicon carbide power MOSFETs, comprising:
[0051] S1: Determine the gate detection voltage through current-voltage scanning according to the specifications of the silicon carbide power MOSFET and the thickness of the gate oxide layer.
[0052] S2: Based on the relationship curve between drain current and gate voltage at different temperatures, analyze the relationship curve between low-field mobility of silicon carbide power MOSFET carriers and temperature to determine the screening temperature.
[0053] S3: At the screening temperature, a gate detection voltage is applied to the silicon carbide power MOSFET to be tested for a preset time, and the gate leakage current is detected.
[0054] S4: If the gate leakage current is greater than the current threshold value, it is determined that the silicon carbide power MOSFET to be tested has a high risk of early oxide failure, and is screened out. If the gate leakage current is less than or equal to the current threshold value, it is determined that the silicon carbide power MOSFET to be tested is a qualified normal device.
[0055] In the embodiment, according to the specification information and the gate oxide layer thickness of the silicon carbide power MOSFET, the gate detection voltage is determined by the current-voltage scanning method; then the relationship curve between the low-field mobility of the silicon carbide power MOSFET carrier and the temperature is analyzed according to the relationship curve between the drain current and the gate voltage at different temperatures, and the screening temperature is determined; without damaging the silicon carbide power MOSFET, the more extreme gate detection voltage and screening temperature are determined, the gate detection voltage and screening temperature are applied to the silicon carbide power MOSFET to be tested, and the gate leakage current is detected. If the gate leakage current is greater than the current threshold value, it is determined that the silicon carbide power MOSFET to be tested has a high risk of early oxide failure, and is screened out. The method detects the silicon carbide power MOSFET to be tested with more extreme gate detection voltage and screening temperature, and has stronger screening strength without damaging the reliability of normal devices. The method is convenient and fast, and has certain universality.
[0056] The steps are described in detail below.
[0057] S1: According to the specification information and the gate oxide layer thickness of the silicon carbide power MOSFET, the gate detection voltage is determined by the current-voltage scanning method.
[0058] S11: According to the specification information and the gate oxide layer thickness of the silicon carbide power MOSFET, the initial gate scanning voltage is set.
[0059] S12: Starting from the initial gate scanning voltage, gradually increase the gate scanning voltage applied to the silicon carbide power MOSFET, and the application time of each gate scanning voltage is a preset time length. The gate leakage current corresponding to each gate scanning voltage is detected, and it is judged whether the gate leakage current is close to the preset leakage current. When the gate leakage current is within the fluctuation range based on the preset leakage current, for example, the preset leakage current is 1uA, and the gate leakage current is within 0.95uA-1uA, or the gate leakage current is unchanged for a plurality of times, the gate leakage current is considered to be close to the preset leakage current.
[0060] S13: When the gate leakage current is not close to the preset leakage current, the gate scanning voltage is continuously increased.
[0061] S14: When the gate leakage current is close to the preset leakage current, the last gate scanning voltage is taken as the gate detection voltage.
[0062] Specifically, taking a certain commercial 1200V SiC power MOSFET as an example, the related parameter information is shown in Table 1, and the maximum acceptable screening oxide layer electric field strength E ox is 9 MV / cm.
[0063] Reasonable selection of gate detection voltage and screening temperature is needed to screen early failure devices to ensure the accuracy of screening and avoid the impact of the screening process on the performance of the device. The specific steps are as follows: first, measure the relationship between the gate leakage current of the SiC power MOSFET and the gate scanning voltage by means of fast current voltage scanning, and ensure that the application time of the scanning voltage of the gate is greater than 1 ms and does not exceed 500 ms (i.e. the preset time is within the range of 1 ms-500 ms) to ensure the accuracy of the measurement. According to the specifications and gate oxide thickness of the device, and in order to save measurement time, the initial scanning voltage of the gate voltage can start from 30V, gradually increasing from a smaller voltage. If it is judged that the maximum gate leakage current is less than 1uA, gradually increase the gate scanning voltage to prevent device breakdown or damage, and the step size can be set to 1V or 0.5V. When the maximum gate leakage current is close to 1uA, stop increasing the gate scanning voltage; for example, the initial gate scanning voltage is selected to be 35V, and the scanning obtains a maximum gate leakage current much less than 1uA (preset leakage current), then increase the gate scanning voltage to 36V, as shown in Figure 5 , when the gate scanning voltage increases to about 40V, the maximum gate leakage current is very close to 1uA and reaches a small platform, at this time 40V is used as the gate detection voltage.
[0064] Table 1 Parameter information table of 1200V SiC power MOSFET
[0065] Parameter Standard value Threshold voltage V th @150 °C (V) 2.2 Conduction resistance R on (mΩ)@RT 300 Gate-source leakage current (nA) @ Vgs = 20 V MAX = 300 Average breakdown voltage @ 150 °C (V) 50 Gate oxide thickness estimate (nm) 45
[0066] S2: According to the relationship curve of the drain current and the gate voltage at different temperatures, analyze the relationship curve of the low-field mobility of the carrier of the silicon carbide power MOSFET and the temperature, and determine the screening temperature.
[0067] S21: Linear fitting is performed on the relationship curve of the drain current and the gate voltage to obtain the low-field mobility of the carrier of the silicon carbide power MOSFET.
[0068] S22: Analyze the relationship curve of the low-field mobility and the temperature, and take the temperature corresponding to the peak value of the curve as the screening temperature.
[0069] Specifically, high temperature mainly affects the carrier mobility of the device, so by judging the change of the mobility of the device with temperature, a suitable temperature is selected. It is necessary to measure the I d -V gThe mobility variation of the device can be obtained from the curve. d -V g The curve measurement is taken at an initial V d = 50 mV, V g The scan voltage is in the range of 0-20 V with a step size of at least 0.5 V to ensure the accuracy of the extracted mobility. Next, the mobility is extracted from the I d -V g curve by constructing a Y function. The SiC power MOSFET drain current is expressed as:
[0070]
[0071] where W and L are the effective channel width and length, respectively, C ox is the gate oxide capacitance, μ0 is the low field mobility, θ is the mobility degradation coefficient, V t is the charge threshold voltage, V g and V d are the gate and drain voltages, respectively.
[0072] The transconductance g m of the MOSFET is easily obtained by differentiating the above equation:
[0073]
[0074] By appropriately combining equation 1 and equation 2, a function is constructed that eliminates the effect of the drain voltage on the mobility degradation. This can be easily achieved by dividing the current expression by the square root of the transconductance:
[0075]
[0076] It is clear from equation 3 that I d / g m 1 / 2 should be linear with respect to the gate voltage, and the charge threshold voltage V t and the low field mobility parameter μ0 can be determined by the intercept and slope, respectively. Thus, by performing a linear fit on the I d -V g curve, the low field mobility μ0 of the SiC power MOSFET is obtained. By measuring the I d -V g curve at different temperatures (as shown in Figure 6 ), with a temperature range from 100 to 200 degrees Celsius in steps of 10 degrees, the low field mobility variation with temperature can be relatively efficiently obtained, as shown in Figure 7As shown in the figure, it can be found that the low-field mobility of the device reaches its highest value near 170°C, and the low-field mobility of the device decays significantly at higher temperatures. Therefore, choosing 170°C as the screening temperature for the device can effectively and safely screen the device.
[0077] S3: At the screening temperature, a gate detection voltage is applied to the silicon carbide power MOSFET to be tested for a preset time, and the gate leakage current is detected.
[0078] S4: If the gate leakage current is greater than the current threshold, the silicon carbide power MOSFET to be tested is determined to have a high risk of early oxide failure and is screened out.
[0079] Specifically, the gate detection voltage is selected to be 40V and the screening temperature is 170℃. At the same time, it will not cause damage to the device. A screening time of 100ms is used to save the processing time. At the same time, when the screening time is 100ms, the negative threshold voltage shift caused by hole capture can be avoided. At an ambient temperature of 170℃, a constant voltage of 40V is applied to the gate of the SiC power MOSFET to be tested for 100ms; the gate leakage current value I is monitored and recorded in real time. g ;if I g >10μA (current threshold), the device is judged to have a high risk of early oxide failure and is screened out. Figure 8 As shown in the figure, under high-temperature, high-voltage screening, five devices with gate leakage currents exceeding 10μA at a gate voltage of 40V were detected and rejected. The remaining devices had gate leakage currents less than 10μA and were considered normal devices. At 38V, the oxide layer lifetime of normal devices ranges from 40 to 80 hours, while the oxide layer failure time of the rejected devices was much shorter than that of normal devices. By using transient gate leakage current measurements at high temperature and high electric fields, devices with high gate leakage currents are screened out, thereby quickly and conveniently identifying devices with extrinsic defects and the risk of early failure.
[0080] like Figure 9 As shown, an embodiment of the present application provides a silicon carbide power MOSFET early failure screening system, comprising:
[0081] The gate detection voltage analysis module 10 is used to determine the gate detection voltage through a current-voltage scanning method according to the specification information of the silicon carbide power MOSFET and the thickness of the gate oxide layer.
[0082] The screening temperature analysis module 20 is used to analyze the relationship curve between the low-field mobility of the silicon carbide power MOSFET carriers and temperature according to the relationship curve between the drain current and the gate voltage at different temperatures, and determine the screening temperature.
[0083] The detection module 30 is configured to apply a gate detection voltage to the to-be-tested silicon carbide power MOSFET at a screening temperature for a preset time, and detect a gate leakage current.
[0084] The screening module 40 is configured to determine that the to-be-tested silicon carbide power MOSFET has a high-risk early oxide failure if the gate leakage current is greater than the current threshold, and screen out the to-be-tested silicon carbide power MOSFET.
[0085] In an optional embodiment of the present application, the gate detection voltage analysis module comprises:
[0086] The initial gate scanning voltage is set according to the specification information of the silicon carbide power MOSFET and the gate oxide layer thickness.
[0087] The gate scanning voltage applied to the silicon carbide power MOSFET is gradually increased from the initial gate scanning voltage, and the gate leakage current corresponding to each gate scanning voltage is detected and determined whether the gate leakage current is close to the preset leakage current, wherein the gate leakage current is considered to be close to the preset leakage current when the gate leakage current is within a fluctuation range based on the preset leakage current or the gate leakage current is unchanged for a plurality of times.
[0088] The gate scanning voltage is continuously increased when the gate leakage current is not close to the preset leakage current.
[0089] The last gate scanning voltage is taken as the gate detection voltage when the gate leakage current is close to the preset leakage current.
[0090] In an optional embodiment of the present application, the screening temperature analysis module comprises:
[0091] The relationship curve between the drain current and the gate voltage is linearly fitted to obtain the low-field mobility of the carrier of the silicon carbide power MOSFET.
[0092] The relationship curve between the low-field mobility and the temperature is analyzed, and the temperature corresponding to the peak value of the curve is taken as the screening temperature.
[0093] In the present embodiment, the beneficial effects of the silicon carbide power MOSFET early failure screening system are similar to those of the silicon carbide power MOSFET early failure screening method, and will not be repeated here.
[0094] It is to be noted that, in the present text, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
[0095] The above examples are merely used to illustrate the technical solutions of the present application, but not to limit it; even though the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still make modifications to the technical solutions recorded in the foregoing examples, or make equivalent replacements to some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A method for screening early failure of silicon carbide power MOSFET, characterized in that: include: According to the specifications of the silicon carbide power MOSFET and the thickness of the gate oxide layer, the gate detection voltage is determined by current-voltage scanning; According to the relationship curve between drain current and gate voltage at different temperatures, the relationship curve between low-field mobility of silicon carbide power MOSFET carriers and temperature is analyzed to determine the screening temperature; At the screening temperature, a gate detection voltage is applied to the silicon carbide power MOSFET to be tested for a preset time, and the gate leakage current is detected; If the gate leakage current is greater than the current threshold, the silicon carbide power MOSFET to be tested is determined to have a high risk of early oxide failure and is screened out.
2. The method for screening early failure of silicon carbide power MOSFET according to claim 1, wherein: Determining the gate detection voltage by current-voltage scanning according to the specification information and gate oxide thickness of the silicon carbide power MOSFET includes: Set the initial gate scan voltage based on the silicon carbide power MOSFET's specifications and gate oxide thickness; Starting from an initial gate scan voltage, gradually increase the gate scan voltage applied to the silicon carbide power MOSFET, with each gate scan voltage applied for a preset duration, detect the gate leakage current corresponding to each gate scan voltage, and determine whether the gate leakage current is close to the preset leakage current. The gate leakage current is considered to be close to the preset leakage current when the gate leakage current is within a fluctuation range based on the preset leakage current or when the gate leakage current remains unchanged for multiple consecutive times; When the gate leakage current is not close to the preset leakage current, continuously increasing the gate scan voltage; When the gate leakage current is close to the preset leakage current, the last gate scanning voltage is used as the gate detection voltage.
3. The method for screening early failure of silicon carbide power MOSFET according to claim 1, wherein: The method of analyzing the relationship curve between the drain current and the gate voltage at different temperatures and the low-field mobility and temperature change curve of the silicon carbide power MOSFET carriers to determine the screening temperature includes: The relationship curve between drain current and gate voltage is linearly fitted to obtain the low-field mobility of carriers in silicon carbide power MOSFET. The relationship curve between low-field mobility and temperature was analyzed, and the temperature corresponding to the peak of the curve was used as the screening temperature.
4. The method for screening early failure of silicon carbide power MOSFET according to claim 1, wherein: When the silicon carbide power MOSFET to be tested is a 1200V SiC power MOSFET, the gate detection voltage is 40V, the screening temperature is 170°C, the preset time is 100ms, and the current threshold is 10μA.
5. The method for screening early failure of silicon carbide power MOSFET according to claim 2, wherein: When the silicon carbide power MOSFET to be tested is a 1200V SiC power MOSFET, the initial gate scan voltage is 30V, the preset time length is in the range of 1ms-500ms, and the preset leakage current is 1uA.
6. A silicon carbide power MOSFET early failure screening system, characterized in that: include: The gate detection voltage analysis module is used to determine the gate detection voltage through current-voltage scanning according to the specifications of the silicon carbide power MOSFET and the thickness of the gate oxide layer; The screening temperature analysis module is used to analyze the relationship curve between the low-field mobility of the silicon carbide power MOSFET carriers and temperature based on the relationship curve between the drain current and the gate voltage at different temperatures, and determine the screening temperature; A detection module is used to apply a gate detection voltage to the silicon carbide power MOSFET to be tested for a preset time at a screening temperature to detect the gate leakage current; The screening module is used to determine that the silicon carbide power MOSFET to be tested has a high risk of early oxide failure and screen it out if the gate leakage current is greater than the current threshold.
7. The silicon carbide power MOSFET early failure screening system according to claim 6, characterized in that: The gate detection voltage analysis module includes: Set the initial gate scan voltage based on the silicon carbide power MOSFET's specifications and gate oxide thickness; Starting from an initial gate scan voltage, gradually increase the gate scan voltage applied to the silicon carbide power MOSFET, with each gate scan voltage applied for a preset duration, detect the gate leakage current corresponding to each gate scan voltage, and determine whether the gate leakage current is close to the preset leakage current. The gate leakage current is considered to be close to the preset leakage current when the gate leakage current is within a fluctuation range based on the preset leakage current or when the gate leakage current remains unchanged for multiple consecutive times; When the gate leakage current is not close to the preset leakage current, continuously increasing the gate scan voltage; When the gate leakage current is close to the preset leakage current, the last gate scanning voltage is used as the gate detection voltage.
8. The silicon carbide power MOSFET early failure screening system according to claim 6, characterized in that: The screening temperature analysis module includes: The relationship curve between drain current and gate voltage is linearly fitted to obtain the low-field mobility of carriers in silicon carbide power MOSFET. The relationship curve between low-field mobility and temperature was analyzed, and the temperature corresponding to the peak of the curve was used as the screening temperature.