Hot low cost sensors
Silicon carbide crystallizes in numerous different modifications (polylypes). The 3C-SiC (cubic unit cell) is particularly attractive for SiC-based devices as it can be grown on inexpensive Si substrates, making batch fabrication possible. However, the 3C-SiC/Si fabrication produces defects of high density in the 3C-SiC films, affecting the performance of electronic devices fabricated from these films. Aiming at the reduction of the defect density, the FLASiC-project developed a new process to produce epitaxial and bulk 3C-SiC on Si or silicon-on-insulator (SOI) substrates. The FLASiC process and material paved the way for the development of new sensors with higher performances in terms of resonance frequency, resonance amplitude and quality factor. These types of sensors can be used for gas detection or molecules identification. They can be used for high temperature emission monitoring and control, providing energy efficiency and limiting gases emitted in the atmosphere. Furthermore, the information which may arise from the application of these sensors in exhaust gas sensing will assist the optimization of the efficiency of the internal combustion engines or reactors. Throughout the fabrication stage of these devices several technological processes have been set up with special emphasis on deep SiC etching. The Inductively Coupled Plasma Etching (ICP) has been found to provide optimal etching condition. Furthermore, the process of doping and contact formation on the SiC layer has been developed and optimised. The SiC membrane formation process deployed can be also used for the fabrication of freestanding resonators for gas detection or of pressure/accelerometer sensors on SiC membranes. The excellent properties and low cost of the new sensors make them very attractive for future commercialisation. Their long-term reliability validation and the fabrication of a high temperature package for their housing in the final application systems are the next steps towards this direction.