Rugged SiC Device & Power Module Technology for Reliable Power Electronics

A. Morgan
NoMIS Power,
United States

Keywords: Power device packaging, Silicon Carbide (SiC), power electronics


NoMIS Power is accelerating the deployment of clean technologies by enabling the widespread adoption of silicon carbide (SiC); a compound semiconductor material with wide bandgap (WBG) properties capable of taking power device performance to a level where the incumbent silicon material simply cannot compete. WBG materials allow operation at higher voltages, frequencies, and temperatures enabling numerous new use applications within the global power management industry. These highly efficient power semiconductors support the development of a U.S.-based supply chain for key technologies such as solid-state transformers (SSTs), DC protection equipment, HVDC converters, locomotive traction drives, industrial motor drives, and EV fast chargers – all relying on power management systems that necessitate resilient power electronics. NoMIS Power has a two-fold solution at (1) the power semiconductor device and (2) the power module -level, that offers rugged SiC technology for the aforementioned applications across the energy, transportation, aerospace, and defense sectors. (1) SiC MOSFET Longer SCWT: SiC MOSFETs have been improved in regards to specific on-resistance (Ron,sp) and breakdown voltage (BV) with improvement in the gate oxide recipes and edge termination efficiencies, respectively. However, 4H-SiC MOSFETs still elicit reliability/ruggedness concerns. NoMIS Power has a novel approach to improve the trade-off relationship between SCWT and Ron,sp using MOSFETs with deep PN junction structures and low energy implants. Under the operation condition for forward conduction, the conventional and NoMIS Power SiC MOSFETs have almost identical Ron,sp. However, the maximum drain current of NoMIS Power SiC MOSFETs during the SC event is reduced by ~2.7 times, resulting in the increase of SCWT, which is ~4 times longer than the conventional SiC MOSFETs. Chiefly, the trade-off relationship between Ron,sp and SCWT was significantly improved, translating to highly efficient, highly reliable power electronics at a reduced cost. (2) Integrated Internal Busbar for SiC Power Modules: In order to build robust, high-power density SiC-based power conversion systems (PCS) that enable U.S. electrification, materials and packaging innovations are needed to enable integration of the power module with system-level components and passives. It is essential that SiC devices are packaged using materials/components capable of managing greater amounts of electrical and magnetic energy, while mitigating the negative impacts associated with the resulting thermos-mechanical issues that lead to failures. Unreliable SiC MOSFET performance occurs when the acceleration of performance parameters (Ron,sp, Vth, IDSS, IGSS) shifts from their nominal values. Furthermore, the degree to which the parameters shift of each individual SiC MOSFET inside the power module will differ, resulting in unequal stressing of the SiC MOSFETs. In order to help alleviate the impact of any SiC MOSFET parameter shift from occurring inside the power module, NoMIS Power has developed a functionally integrated internal busbar structure. Integration of current balancing inductors improves current sharing between parallel SiC power devices, with Vth variations, that make up the high and low –sides switches of the power module by means of passive impedance matching to facilitate distributed energy losses during repetitive switching events (i.e. improve reliability of the power module by reducing localized hot-spots).