Power-Law Time Exponent n and Time-to-Failure in 4H-SiC MOSFETs: Beyond Fixed Reaction-Diffusion Theory.

Area of Science:

• Materials Science
• Electrical Engineering
• Semiconductor Physics

Background:

• Bias-Temperature Instability (BTI) is a critical reliability concern in power semiconductor devices.
• Classical Reaction-Diffusion models, established for silicon, are often assumed for SiC devices.

Purpose of the Study:

• Investigate BTI mechanisms in 1700 V 4H-SiC MOSFETs under realistic operating conditions.
• Determine the applicability of conventional silicon BTI models to SiC technology.
• Develop an improved reliability prediction framework for SiC devices.

Main Methods:

• Utilized 1700 V 4H-SiC MOSFETs subjected to 1 MHz switching with simultaneous gate and drain stress.
• Performed threshold-voltage measurements to quantify degradation.
• Conducted temperature-dependent stress tests to analyze activation energy.

Main Results:

• Observed BTI degradation deviating from classical Reaction-Diffusion behavior in SiC.
• Identified a field-driven trap-generation mechanism at high negative gate bias.
• Measured a negative activation energy (-0.466 eV), indicating accelerated degradation at lower temperatures.

Conclusions:

• Conventional silicon BTI models are inadequate for SiC technologies.
• Fixed-power-law exponent lifetime extrapolation leads to significant prediction errors.
• A proposed bias-dependent, field-driven framework offers more accurate reliability assessment for SiC converters.