Temperature dependence of vacuum encapsulated resonators for humidity measurement

Abstract

This paper demonstrates the effect o humidity measurements using a charge-b encapsulated single-anchored double-en resonator (DETF). The resonator is electr to a metal bond pad on the external dioxide. Changes in the ambient humidity decay characteristics of the resonator b surface resistance of the oxide. This chan by measuring the shift in resonant fr electrostatic spring softening. Varying from 12°C to 32°C and the relative humid to 60%, the temperature dependence of tim from -0.05/°C to -0.03/°C and the re dependence of time decay ranged from 0

Integrated sensor cross-sensitivity analysis

“…The relative permittivity of air changes approximately linearly with humidity at a rate of 1.4 ppm/%RH at 20 o C. This source of cross-sensitivity accounts for only -2.1 g offset of the y-axis accelerometer and -196 g of the z-axis, so there must be another mechanism in effect. Hennessy et al investigated the effects of humidity on bias electrode leakage using encapsulated MEMS resonators and found the major mechanisms were surface and through-oxide leakage [6]. They found that surface resistance decreases by approximately 10,000 times from 5 to 90 %RH as water molecules are adsorbed to the oxide surface and eventually form a contiguous sheet, leading to ohmic conduction at high humidity levels.…”

Vacuum encapsulated resonators for humidity measurement

“…We demonstrate here an indirect measurement technique to measure large surface resistances [8,9]. This technique utilizes three functional components: charge decay through the surface resistance, a MEMS resonator, and an oscillator (Fig.…”