Temperature-insensitive silicon carbide resonant micro-extensometers

This work presents thin-film polycrystalline silicon carbide resonant micro-extensometers fabricated on a single-crystalline silicon substrate that are temperature-insensitive near room temperature. The slight difference in thermal expansion coefficient between the device layer and the substrate induces a slight tensile strain near room temperature, which counteracts material softening of the resonator. An analytical model that accounts for these thermal effects predicts that this system will exhibit a turnover temperature near room temperature. A temperature sensitivity of 0.7 Hz/degC (3.6 ppm/degC) from 17 to 65degC is measured experimentally, without compromising the strain-sensing capability of the resonator. This is nearly a 10-fold improvement over an equivalent epitaxial silicon resonant miro-extensometer (-30 ppm/degC).