- SiC is known as potential material for a new generation of power devices. Hexagonal SiC polytypes seem to be more suited for high power applications (2000-10000V), while 3C-SiC is more suited for medium power applications (300-1200V, 10-100A) due to its smaller bandgap. For use in power applications, two types of devices should be available: rectifiers (diodes) and transistors (e.g. MOSFETs). Processes for both types of devices based on 3C-SiC were developed during the project and several device batches were carried out, including Schottky barrier diodes (SBD), junction-barrier controlled Schottky diodes (JBS), and pn-junction diodes (PND), as well as lateral and vertical MOSFET transistors.
All these devices work in principle as they should, but not with the expected performance. Especially their blocking capability is limited to about 100V by extended crystal defects like stacking faults. It was shown during the project that material improvements by reducing the number of crystal defects will enable the use of 3C-SiC devices for at least 300-600V applications. Especially vertical MOSFET devices have been shown to be able to carry high currents with typical gate control voltages of 15-20V and on-state resistances similar to state of the art hexagonal SiC devices.
- A full set of unit processes for the fabrication of 3C-SiC devices was established at ACREO. The process line includes epitaxial growth of n- and p-doped epilayers, ion implantation and post-implantation anneal, lithography, dry etching, ohmic contact formation, silicon dioxide and silicon nitride deposition, and thermal oxidation.