Very High Voltage Devices in Silicon Carbide: target 15kV – VHVD-SiC

This project focuses on the design and realization of very high voltage silicon-carbide devices, with the final objective of reaching a breakdown voltage over 15 kV. Compared to pure silicon, SiC presents a 7 times higher critical electric field, a 3 times larger band-gap and higher thermal conductivity. SiC devices can target the electrical distribution market, allowing size reduction of the converters through an increase of the switching frequency, together with higher temperature operating capability. Such converters, working in the range 3-10 kV, are key smart access components of the coming new generations of electric power distribution grids and networks with decentralized electrical energy production and management. The project proposes to demonstrate for the first time both rectifiers AND controllable switching devices with voltage handling over 10 kV. The societal and economical impacts of the project can therefore be considered as potentially enormous with strong impacts on sustainable energy sources implementation into existing or new power grids. For devices operating over 3kV, bipolar structures yield better cost/performance compromise. In a first run, we will use commercial SiC material to fabricate 10 kV device prototypes, then, in a second run, we will target 15 kV using thick (100 µm) ultra-pure epitaxial layers provided by University of Linköping in Sweden. The devices (PIN diodes, and BJTs or thyristors) will be fabricated in clean room facilities by subcontractors INL (Lyon) and CNM (Barcelona). CNM subcontractor is particularly concerned by the solid layer passivation realization, gaseous passivation being studied by partners AMPERE and ISL. A new approach for deep peripheral protection, based on VLS epitaxy, by partner LMI, and CMP planarization, by the Novasic SME company, will be validated. The behavior of the stacking faults, the main cause of failures in the SiC bipolar devices published today, will be monitored and visualized during device operation in direct regime current flow, by Partner GES in collaboration with subcontractors IMEP and LEPMI in Grenoble. Partner ISL will perform electric characterization of the devices under high voltage reverse bias in controlled atmosphere with correlative investigation and analysis of the peripheral protection behavior by optical beam induced current (OBIC) at AMPERE. This will allow the validation of the design and technological options. The detailed analysis of the on-state switching of the controllable devices will be performed at AMPERE.