Remaining useful lifetime prediction and extension of Si power devices have been studied extensively. Silicon carbide (SiC) power devices have been developed and commercialized. Specifically, SiC mosfet s have been utilized for the next generation high-voltage, high-power converters with smaller size and higher efficiency, covering various mainstream applications, including photovoltaic systems, electric vehicles, solid-state transformers, and more electric ships and airplanes. However, the SiC-based devices have different failure modes and mechanisms compared with Si counterparts. Therefore, a comprehensive review is critical to develop accurate lifetime prediction and extension strategies for SiC power converter systems. The SiC power device component-level failure modes and mechanisms are first investigated. Different accelerated lifetime tests and component-level lifetime models are then compared. Power converter system-level offline lifetime modeling techniques and software tools are further summarized. Besides, the SiC power converter condition monitoring strategies and health indicators are surveyed. The online measurement challenges are also studied. Furthermore, the system-level lifetime extension strategies are reviewed. By integrating device physics, statistical modeling, reliability engineering, and mechanical engineering with power electronics, this article is intended to provide a comprehensive overview, address existing challenges, and unfold new research opportunities regarding the SiC power converter real-time lifetime prediction and extension.

Overview of Real-Time Lifetime Prediction and Extension for SiC Power Converters

This paper deals with real-time estimation of the junction temperature of SiC power mosfet s. The junction temperature of a device with four-switch module is estimated in real-time by measuring its current and on-state voltage V ON at each switching period and entering the temperature in the lookup table of the device. The temperature model is preliminarily obtained in a dedicated commissioning session, where V ON is measured at different temperature and current conditions. The results show the feasibility of online temperature monitoring and even the active limitation of the junction temperature of the tested SiC power mosfet modules accurately and with an instantaneous dynamic response. Different modules with die from different manufacturers were tested in an H-bridge demonstrator power converter, emulating the operating conditions of real converters such as voltage source dc/ac or dc/dc conversion structures. The commissioning procedure is meant to be performed directly on the final application for each converter. The measurements obtained using the proposed temperature estimation technique are validated using a thermal camera and compared to the direct measurement of the die temperature with a thermistor, showing high accuracy and high feasibility.

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Online Junction Temperature Estimation of SiC Power mosfets Through On-State Voltage Mapping

SiC MOSFETs (silicon carbide metal-oxide semiconductor field-effect transistors) are replacing Si insulated gate bipolar transistors in many power conversion applications due to their superior performance. However, ruggedness and reliability of SiC MOSFETs are still big concern for their widespread applications in the market, especially in safety-critical applications. The objective of this study is to provide a comprehensive picture on the ruggedness and reliability of commercial SiC MOSFETs, discover their failure or degradation mechanism, and propose some possible mitigation methods through both literature survey and in-depth analysis. The ruggedness of SiC MOSFETs discussed here includes short-circuit (SC) ruggedness, avalanche ruggedness, and their failure mechanism. The reliability issues include gate oxide reliability, degradation under high-temperature bias stress, repetitive SC stress, avalanche stress, power cycling stress, body diode's surge current stress, and their degradation mechanism. Furthermore, this study discusses methods and solutions to improve their ruggedness and reliability.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2019.0587

Review and analysis of SiC MOSFETs’ ruggedness and reliability

The reliability analysis and lifetime prediction for SiC-based power modules is crucial in order to fulfill the design specifications for next-generation power converters. This paper presents a fast mission-profile-based simulation strategy for a commercial 1.2-kV all-SiC power module used in a photovoltaic inverter topology. The approach relies on a fast condition-mapping simulation structure and the detailed electro-thermal modeling of the module topology and devices. Both parasitic electrical elements and thermal impedance network are extracted from the finite-element analysis of the module geometry. The use of operating conditions mapping and look-up tables enables the simulation of very long timescales in only a few minutes, preserving at the same time the accuracy of circuit-based simulations. The accumulated damage related to thermo-mechanical stress on the module is determined analytically, and a simple consumed lifetime calculation is performed for two different mission profiles and compared in different operating conditions.

https://vbn.aau.dk/ws/files/308852879/Accepted.pdf

Mission-Profile-Based Lifetime Prediction for a SiC mosfet Power Module Using a Multi-Step Condition-Mapping Simulation Strategy

The temperature-sensitive electrical parameters (TSEPs) have been used in silicon carbide (SiC) mosfets junction temperature measurement for over-temperature protection and condition monitoring. However, the device aging can affect the TSEPs and thus leads to false ${\boldsymbol{T}}_{\boldsymbol{j}}$ measurement. In this article, the aging's impacts on various TSEPs are comprehensively investigated. Specifically, utilizing the dc power cycling test, both the gate oxide instability and package degradation are considered. Then the commercial devices with different structures are aged, and their temperature-dependent static and switching characteristics are evaluated at different aging cycles. Both the positive gate bias-induced threshold voltage shift and package degradation are observed, and their impacts on each TSEP are evaluated independently. Based on the evaluation results at various operating conditions, the temperature measurement errors due to different aging mechanisms are well summarized for each TSEP. From the dc power cycling test result, the package degradation's impact on TSEPs is found to be more significant than the gate oxide instability. It is pointed out that the aging's effect on TSEPs is an important factor that needs to be considered for accurate ${\boldsymbol{T}}_{\boldsymbol{j}}$ measurement in SiC mosfets .

Evaluation of Aging's Effect on Temperature-Sensitive Electrical Parameters in SiC mosfets

In silicon carbide (SiC) power MOSFETs, threshold voltage instability under high-temperature conditions has potential reliability threats to long-term operation. In this paper, the threshold voltage shifts caused by the instability mechanisms in accelerated power cycling tests for SiC MOSFETs are investigated. In conventional power cycling tests, the positive threshold voltage shift can cause successive ON-state resistance increases, which can sequentially increase junction temperature variations gradually under fixed test conditions. In order to distinguish the increased die voltage drop from the bond wire resistance degradation, an independent measurement method is used during the power cycling tests. As the number of cycle increases, SiC die degradation can be observed independently of bond wire increases during the tests. It is studied that the SiC die degradation is associated with the threshold voltage instability mechanisms. Unlike the bond wire lift-off failure, the die degradation and the related die resistance increase can stop the power cycling test earlier than expected. In addition, a new test protocol considering the die degradation is proposed for the power cycling test. By means of power device analyzer, the failure mechanism and the degradation performance of SiC MOSFETs before and after the power cycling test are compared and discussed. Finally, experimental results confirm the role of threshold voltage shifting and identify different failure mechanisms.

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Role of Threshold Voltage Shift in Highly Accelerated Power Cycling Tests for SiC MOSFET Modules

A highly accelerated power cycling test platform using current source converter for SiC-MOSFET power modules is proposed. The control principles of delta and average junction temperatures are introduced. By using isolated thermal fibers, the junction temperature (T j ) variations can be monitored during the test process without removal of silicone gel. The power module is tested in the conditions of ΔT j =60 °C, mean temperature T jm =145 °C and the maximum T j =175 °C. By means of device analyzer, the degraded conditions of electrical parameters after power cycling test are fully investigated and compared. As a result, the effects of degradation on the static and dynamic characteristics during conventional operation are discussed. Finally, the research results can help examine the failure precursors and then estimate the remaining useful lifetime of SiC MOSFET modules.

Marcello Turnaturi

Papers

Role of Threshold Voltage Shift in Highly Accelerated Power Cycling Tests for SiC MOSFET Modules

Aging precursors and degradation effects of SiC-MOSFET modules under highly accelerated power cycling conditions

Evaluation of electrochemical migration into an isolated sintered power module