High Temperature Reverse Bias (HTRB) Reliability Test Operation Manual: Ensuring Long-Term Stability of Power Semiconductor Devices

1. Introduction

1.1 Background

With the continuous evolution of power electronic systems toward higher efficiency, higher power density, and enhanced reliability, the stability of power semiconductor devices under extreme operating conditions has become a critical bottleneck. In applications such as electric vehicles, photovoltaic power generation, and industrial power systems, devices are required to withstand prolonged exposure to both high voltage and elevated temperature environments.

Against this backdrop, the High Temperature Reverse Bias (HTRB) test has been widely adopted as a standard accelerated life evaluation method in power semiconductor reliability qualification frameworks. By applying reverse bias under high-temperature conditions, HTRB accelerates the evolution of latent defects within devices, enabling the assessment of long-term reliability within a significantly reduced time frame.

For emerging wide-bandgap semiconductor materials such as SiC and GaN, the importance of HTRB testing is further amplified due to their high electric field operating characteristics. As a result, HTRB has become an indispensable step in pre-production qualification workflows.

1.2 Significance of HTRB Testing

The core purpose of HTRB testing is to simulate extreme operating conditions that devices may encounter in real-world applications and to proactively expose potential failure risks, including:

• Evaluation of long-term stability under combined high temperature and high electric field stress
• Identification of key failure mechanisms such as leakage current increase, breakdown risk, and interface degradation
• A critical tool for pre-production reliability screening and quality control

Through systematic HTRB testing, the overall reliability and consistency of power semiconductor devices in practical applications can be significantly improved.

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2. Scope & Applicability

2.1 Applicable Device Types

HTRB testing is applicable to a wide range of power semiconductor devices, including but not limited to:

• MOSFETs (Silicon-based / Silicon Carbide SiC)
• IGBT power transistors
• GaN High Electron Mobility Transistors (HEMTs)
• Diode devices (Schottky Barrier Diodes, PN junction diodes)

2.2 Application Fields

This testing method is widely used in the following industries:

• Automotive electronics: EV powertrains and charging systems
• Photovoltaic energy systems: inverters and energy storage systems
• Industrial power systems: high-power conversion and motor drives
• High-voltage power systems: specialized and high-reliability power supplies

3. Standards & References

HTRB testing shall be conducted in accordance with internationally recognized standards to ensure data consistency and comparability:

• JEDEC JESD22-A108: High Temperature Reverse Bias Life Test Standard
• AEC-Q101: Qualification Standard for Discrete Semiconductors in Automotive Applications
• MIL-STD related high-temperature stress test specifications (where applicable)

4. Test Principle

HTRB testing is based on the synergistic interaction between thermal excitation and electric field stress.

Under high temperature conditions, carrier energy in semiconductor materials increases, making defect states more easily activated. Simultaneously, reverse bias induces a strong internal electric field, which accelerates multiple degradation processes within the device.

Typical failure mechanisms include:

• Leakage current increase (Leakage Current Increase)
• Threshold voltage shift (Threshold Voltage Shift)
• Surface and interface trap generation (Interface Trap Generation)
• Hot Carrier Injection (HCI) effects

These mechanisms collectively accelerate device aging, enabling early detection of long-term reliability issues.

5. Equipment & Materials

5.1 Major Equipment

• High-temperature aging chamber (150–200°C controllable range)
• Programmable high-voltage DC bias supply system
• Multi-channel burn-in test boards
• Real-time data acquisition and monitoring system

5.2 Auxiliary Materials

• High-temperature test fixtures
• Shielded and low-noise cables
• High-insulation packaging fixtures and mounting structures

6. Sample Preparation

Before testing, a standardized sample preparation procedure must be completed:

• Incoming inspection of samples to ensure no mechanical damage or contamination
• Baseline electrical characterization, including leakage current, threshold voltage, and breakdown voltage
• Sample grouping according to test design (control group and stress group)
• Establishment of a unique sample identification system for full traceability

7. HTRB Test Procedure

7.1 Pre-Test (Pre-test Characterization)

Prior to stress application, the following electrical measurements must be completed:

• I-V characteristic curve measurement
• Leakage current recording (Idss / Ir)
• Baseline measurement of threshold voltage and breakdown voltage

7.2 Loading Procedure

• Mount samples onto the burn-in board
• Verify electrical connectivity integrity
• Confirm absence of short circuits or insulation failures
• Complete grounding system verification

7.3 Temperature Ramp-Up

• Control heating rate at 2–5°C/min
• Reach target temperature (125°C / 150°C / 175°C)
• Maintain thermal stability to ensure uniform temperature distribution

7.4 Bias Application

• Apply reverse bias at 50%–80% of rated voltage
• Increase voltage gradually and stabilize
• Record initial current at t = 0

7.5 Stress Duration

Continuous stress testing under high temperature and reverse bias conditions:

• Standard durations: 168h / 500h / 1000h
• Real-time monitoring of key parameters:

Leakage current variation

Voltage stability

Abnormal fluctuations and alarm logs

7.6 Interim Monitoring (Optional)

• Data recording every 24h or 48h
• Optional interruption test may be performed, provided main stress conditions are not compromised

7.7 Cool-down & Unloading

• Turn off bias voltage first, then heating system
• Allow natural cooling to room temperature
• Complete sample removal and condition verification

8. Post-Test Characterization

8.1 Electrical Re-Measurement

• Leakage current change analysis
• Threshold voltage shift (ΔVth)
• Breakdown voltage variation (ΔBV)

8.2 Failure Criteria

• A device is considered failed if any of the following conditions occur:
• Leakage current exceeds 10× initial value
• Threshold voltage exceeds specification limits
• Hard electrical failure occurs

8.3 Statistical Analysis

• Weibull distribution analysis for lifetime evaluation
• Failure rate vs. time curve analysis
• Reliability modeling and lifetime prediction

9. Failure Analysis (Optional)

For failed samples, advanced failure analysis may be conducted:

• SEM (Scanning Electron Microscopy)
• FIB (Focused Ion Beam cross-sectioning)
• TEM (Transmission Electron Microscopy)
• Electrical mapping analysis
• Thermal imaging for hotspot localization

10. Key Influencing Factors

HTRB results are influenced by multiple factors, including:

• Temperature level and uniformity
• Reverse bias derating factor
• Device structural design (planar vs. trench structures)
• Packaging materials and processes
• Material system differences (Si, SiC, GaN)

11. Safety Considerations

Strict safety protocols must be followed during HTRB testing:

• High-voltage equipment must be equipped with interlock protection systems
• Opening of high-temperature chambers during operation is strictly prohibited
• ESD protection procedures must be enforced
• Automatic overcurrent and overtemperature protection must be enabled
• Operators must undergo specialized training

12. Reporting Format

A standard HTRB test report shall include:

• Complete test condition records
• Sample identification and traceability information
• Raw data logs (I-t / V-t / T-t curves)
• Failure analysis conclusions
• Compliance evaluation (Pass/Fail)

13. Conclusion

The High Temperature Reverse Bias (HTRB) test is a core method in the reliability evaluation framework of power semiconductor devices. By combining high temperature and high electric field stress, it effectively accelerates degradation mechanisms and reveals potential long-term failure risks.

For wide-bandgap semiconductor devices such as SiC and GaN, HTRB testing plays a critical role not only in reliability qualification but also in enabling the industrialization of high-performance power electronics systems. Within third-party testing frameworks, standardized HTRB testing provides essential data support for device design optimization, process improvement, and product certification, thereby significantly enhancing the overall reliability of the semiconductor industry chain.

Frequently Asked Questions (FAQ)