Demonstration of SiC Pressure Sensors at 750 C

We report the first demonstration of MEMS-based 4H-SiC piezoresistive pressure sensors tested at 750 °C and in the process confirmed the existence of strain sensitivity recovery with increasing temperature above 400 °C, eventually achieving near or up to 100 % of the room temperature values at 750 °C. This strain sensitivity recovery phenomenon in 4H-SiC is uncharacteristic of the well-known monotonic decrease in strain sensitivity with increasing temperature in silicon piezoresistors. For the three sensors tested, the room temperature full-scale output (FSO) at 200 psig ranged between 29 and 36 mV. Although the FSO at 400 °C dropped by about 60 %, full recovery was achieved at 750 °C. This result will allow the operation of SiC pressure sensors at higher temperatures, thereby permitting deeper insertion into the engine combustion chamber to improve the accurate quantification of combustor dynamics.