Guideline for evaluating bias temperature instability of silicon carbide metal-oxide-semiconductor devices for power electronic conversion

Practical Application Case: V_T Measurement in Electric Vehicle Traction Inverters

In the SiC MOSFET module of the 800V battery platform, the device operates at a junction temperature of 150-175°C and a gate stress of ±20V.

According to the requirements of this standard, V_T measurement is performed using a gate-controlled diode configuration (as shown in Figure 3): Measurement conditions: Drain current reference ID = 1mA (corresponding to the on-state) Scan rate: ≤100mV/s to avoid capacitance effects Temperature control: ±1°C accuracy to ensure thermal stability Preprocessing: Standardized pre-conditioning pulse to eliminate historical effects Practice shows that improper measurement can lead to V_T reading deviations of up to 15%, severely affecting the accuracy of lifetime prediction. The fixed V_GS method provided in this standard (Figure 4) is particularly suitable for automated test systems, improving the consistency of test efficiency. Hysteresis measurement (Section 4.3.3) is a characteristic requirement of SiC devices. The standard specifies that the hysteresis measurement sequence (Figure 5-6) must include: forward scan → stress application → reverse scan → recovery cycle. A typical 1200V SiC MOSFET may exhibit a hysteresis window of 0.5-2V at 150°C, which directly affects the switching characteristics of the device.

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Comparative Analysis of Five BTI Evaluation Methods

Chapters 5-10 of the standard systematically describe five BTI evaluation methods, each targeting different application scenarios and accuracy requirements:

Industrial Application Comparison: Method Selection in Photovoltaic Inverters

For photovoltaic inverters with a service life requirement of 25 years or more, manufacturers need to evaluate the long-term reliability of SiC MOSFETs under day-night temperature cycling.

Practice shows that: General MSM method: Suitable for rapid screening on production lines; 1000 hours of testing can cover 90% of early failures. Gate scan MSM method: Used for design verification; a V_T-temperature model is established through scanning the entire temperature range (-40°C to 150°C). Triple detection method: Used for certification testing, especially to meet the reliability testing requirements of IEC 63275-1. Appendix B of the standard provides detailed measurement examples. Figures B.6-B.7 show typical response curves of the triple detection method under PBTI/NBTI stress, providing a benchmark for data interpretation. Life Prediction Model and Failure Determination Section 4.5 and Appendix D of the standard systematically explain the BTI life prediction model, which is the core of reliability assessment. Based on the power-law model: ΔV_T = A·t_n·exp(-E_a/kT)·exp(γV_G) Key parameters include: Time exponent n: Typical value for SiC devices is 0.1-0.3, lower than 0.25-0.5 for silicon-based devices. Activation energy E_a: Approximately 0.8-1.2 eV for PBTI and approximately 0.6-1.0 eV for NBTI. Electric field acceleration factor γ: Typical value is 2-4 decade/V. Standard Figures 7-8 show typical NBTI and PBTI drift curves and their power-law fit. It is particularly important to note that the BTI drift of SiC devices often exhibits a **two-stage characteristic**: rapid initial drift (t < 1s) and slow long-term drift (t > 1000s). Standards recommend using long-term drift data for lifetime extrapolation to avoid premature failure determination.

Failure Modes	Physical Mechanisms	Detection Methods	Recovery Characteristics	Preventive Measures
Permanent VTDrift	Interface State Generation	Triple Detection Method	Irreversible	Optimized Oxidation Process
Recoverable VTDrift	Charge Trapping	Hysteresis Method	Partial Recovery	Interface Passivation
Hysteresis Window Enlargement	Slow-State Response	Gate Scan Method	Temperature Dependence	Reduced Interface Density
Fast Transient Effects	Near-Interface Trap	Fast Leakage Current Method	Fast Recovery	Optimized Gate Oxide Quality

The standard explicitly does not define specific failure criteria, leaving this to negotiation between device manufacturers and users. However, it provides standardized data acquisition methods to ensure the comparability of data from different sources. Typical industrial practice is: a V_T drift exceeding the initial value ±20% or a hysteresis window exceeding 1V is used as a warning threshold.

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Standard Implementation Recommendations and Best Practices

Based on the content of this standard, the following implementation recommendations are provided for different stakeholders:

For Device Manufacturers

1. Standardization of Test Conditions: Establish internal test specifications based on Chapter 4 of this standard to ensure consistency of data across different batches.
2. Method Selection Matrix: Select appropriate BTI evaluation methods according to product grade (consumer, industrial, automotive).
3. Completeness of Data Recording: Record complete temperature, voltage, and time series data according to the sampling guidelines in Appendix A.
4. Accelerated Test Design: Design reasonable acceleration factors based on the model in Appendix D to avoid overtesting or undertesting.

For System Integrators

1. Supplier Evaluation Standards: Require suppliers to provide BTI test reports based on IEC 63601, focusing on test method details.
2. Application Condition Mapping: Map actual application conditions (temperature profile, voltage stress) to standard test conditions
3. Derating Design Basis: Develop reasonable voltage and temperature derating specifications based on BTI drift data
4. Lifetime Prediction Verification: Set up monitoring points in the actual system to verify the accuracy of accelerated test lifetime prediction

For Test Laboratories

1. Equipment Calibration Requirements: Ensure voltage measurement accuracy ≤1mV and temperature control accuracy ≤±0.5°C
2. Test Sequence Programming: Strictly program test sequences according to the standard diagram (Figure 9-19), especially timing control
3. Data Report Template: Develop standardized test report templates containing all necessary parameters and raw data
4. Uncertainty Analysis: Perform uncertainty analysis on measurement results, especially long-term drift measurements

Implementation Case: Compliance Testing of Rail Transit Traction Systems

A rail transit vehicle manufacturer developed a BTI test plan for its 3.3kV SiC MOSFET traction converter:

• Test Standards: Fully compliant with IEC 63601, while also referencing IEC 63275-1
• Test Methods: Triple testing method (Chapter 10), testing 3 samples at each stress point
• Stress Conditions: Temperatures 125°C, 150°C, 175°C; Gate voltages +25V, -10V (corresponding to the maximum value in actual applications)
• Test Duration: 1000 hours for each condition, extrapolated to a 30-year service life
• Acceptance Standards: V_T drift <±15%, hysteresis window <0.8V

Through standardized testing, the manufacturer successfully obtained EN 50155 railway application certification. The test data was accepted by multiple customers, reducing the cost of repeated testing.

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Technology Development Trends and Standard Outlook

As SiC devices develop towards higher voltages (3.3kV, 6.5kV) and lower specific on-resistance, BTI evaluation faces new challenges:

1. Evaluation of Ultra-High Voltage Devices: 6.5kV devices require higher gate stress, and existing test equipment may need to be upgraded
2. Evaluation of Dual-Gate Structures: New SiC devices adopt a dual-gate structure, requiring expanded test methods
3. Dynamic BTI Evaluation: In practical applications, gate voltage switches rapidly, requiring the development of dynamic BTI test methods
4. Coupling with Other Failure Mechanisms: The coupling effect of BTI with gate oxide breakdown and hot carrier injection needs to be studied

The stability date specified in this standard is 2028, at which time it will be revised according to technological developments.

Possible revision directions include: Adding dynamic BTI testing methods; Extending to wide bandgap devices (GaN, Ga₂O₃); Incorporating in-situ monitoring technology; Combining with artificial intelligence data analysis. As the first international standard for BTI evaluation of silicon carbide MOS devices, the release of IEC 63601:2025 marks a new stage of standardization in the reliability evaluation of third-generation semiconductors. By standardizing testing methods, regulating data reporting, and establishing comparable benchmarks, this standard will strongly promote the reliable application of silicon carbide power devices in key areas such as new energy, electric vehicles, and industrial control, providing technical support for the global carbon neutrality goal.