A Low-Temperature-Sensitivity Resonant Pressure Microsensor Based on Eutectic Bonding

Abstract

This paper presented a temperature-insensitive resonant pressure microsensor where silicon based resonators anchored on a pressure-sensitive diaphragm were vacuum packaged by a silicon cap based on eutectic bonding. Incoming pressures deformed the pressure-sensitive diaphragm and built stresses around resonators for frequency modulation while under temperature challenges, deformations of silicon based resonators and the vacuum cap were consistent and thus no stresses were generated on resonators. The temperature-insensitive resonant pressure microsensor was analyzed in both theoretical analysis and numerical simulations with confirmed high pressure sensitivities and low temperature disturbances. The resonant pressure microsensor was then fabricated by key steps of photolithography, deep reactive ion etching, and eutectic bonding and characterized in both open-loop and close-loop testing systems. Characterization results showed that the quality factors of resonators were <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 10000$ </tex-math></inline-formula> with pressure sensitivity of 82.98 Hz/kPa and temperature disturbance of −0.63 Hz/° (the lowest result among previously reported resonant pressure microsensors). In summary, the temperature-insensitive resonant pressure microsensor developed in this study exhibited a fitting accuracy better than 0.02% FS within the pressure range of 10 to 120 kPa and the temperature range of −45 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$85^{\circ }\text{C}$ </tex-math></inline-formula> .