The role of an academic in the area of SiC power devices can be categorized as: (1) Fundamental Theoretical Predictions; (2) Fundamental Scientific Knowledge; (3) Fundamental Device Structures; (4) Device Structural Innovations; (5) Device Physics and Analysis; and (6) Technology Feasibility Studies. This paper provides examples of these activities during my past 40 years of effort in this field as a retrospective. New prospective device ideas that will have a strong impact on power electronics in the future are then discussed.
Embedding diagnostic and prognostic into power electronics has the potential to increase the reliability and resiliency of and increasing automated adaptability in variable operating conditions has increased the reliability and resiliency of these systems, especially with the transition to wide bandgap semiconductors where higher voltages, lower on-state resistances, and faster switching speed can lead to rapid failures under conditions such as shoot through. This value proposition requires minimally invasive sensing elements that provide real-time monitoring of online system operations such that parasitic values are not introduced, which erode performance. Presented is an insitu current sensing circuit with integration to the controller to provide enhanced operational capabilities such as sub-microsecond short circuit protection and power semiconductor device on-state resistance measurement. Techniques developed for measurement and protection are not limited to the tested SiC devices and may be extended to numerous types of critical components. These techniques can provide detailed, real-time state of health estimation for critical components and system capabilities, thus, enhancing system reliability.
This paper presents further development of a module concept for Wide Bandgap (WBG) power devices. By embedding WBG power devices in ceramic substrates, high performance of the complete package can be achieved to fully make use of their potentials. In this work, optimizations for design concept and manufacturing processes have been performed to eliminate risk of failures, especially when embedding thin and sensitive devices with fine pad structures. Warpage of package and deformation of devices have been successfully minimized by adjusting volume and layer thickness of die attach and embedded components. Furthermore, processes such as die attach applying, pre-drying and die bonding have been evaluated and improved. Thus, a significant increase of solder and Ag sinter joint quality, especially in fine chip pad areas, have been achieved. Embedded WBG packages with single chip and half bridge topology have been successfully produced and tested in terms of their functionality.
Neutron-induced failures in power electronics are a source of concern in many high-reliability applications. This paper describes how to estimate the device’s decreased lifetime expectancy based on its usage. The physical mechanism, Failure in Time (FIT) statistics and FIT rate calculation methodology are presented. Several Microchip SiC MOSFETs and Schottky barrier diodes at different voltage ratings were tested, and the results for the excess FIT rate calculation based on various factors such as operation voltage, altitude, device area, latitude, and duty factor are presented.
