Silicon Carbide High Temperature MEMS Capacitive Strain Sensor
MEMS and Nanotechnology
Strain sensing at high temperatures, greater than 700°F, is often difficult. Traditional strain sensing uses the piezoresistive effect, which is temperature dependent. To reduce the temperature dependence of the strain sensor one could be built from a robust material such as silicon carbide, SiC. Making measurements using capacitive effects eliminates the effects of temperature within the sensing element. Using the more traditional MEMS material silicon is only an option at lower temperatures. Silicon has good reliability as a mechanical structure to around 900°F, and good electrical properties to 300°F. Having good properties above 700°F, silicon carbide is a robust material that has the ability to be used in high temperature MEMS applications. Using the capacitive effect for measuring strain was the original way to perform this task until the piezoresistive effect was harnessed. MEMS based capacitive strain sensors that have been built previously are known as resonant strain sensors, or the double ended tuning fork resonator. One step further from the double ended tuning fork is a novel capacitive strain sensor device. An examination of the novel approach to measure strain is performed. Modeling and simulation is presented using L-Edit and Coventorware. This asserts the device’s characteristics and gives the novel design merit to be used as a strain sensor.