This paper describes the fabrication process and characteristics of ceramic thin-film pressure sensors based on Ta-N strain gauges for harsh environment applications. The Ta-N thin-film strain gauges are sputter-deposited on a thermally oxidized micromachined Si diaphragm with buried cavities for overpressure tolerance. The proposed device takes advantage of the good mechanical properties of single-crystalline Si as a diaphragm fabricated by SDB and electrochemical etch-stop technology, and in order to extend the temperature range, it has relatively higher resistance, stability and gauge factor of Ta-N thin-films more than other gauges. The fabricated pressure sensor presents a low temperature coefficient of resistance, high-sensitivity, low nonlinearity and excellent temperature stability. The sensitivity is 1.21-1.097 mV/V•kgf/cm2 in temperature ranges of 25-200°C and a maximum non-linearity is 0.43 %FS.
This paper describes anodic bonding characteristics of MLCA to Si-wafer using evaporated Pyres #7740 glass thin-films for MEMS applications. Pyrex #7740 glass thin-films with the same properties that were deposited on MLCA under optimum RF magneto conditions (Ar 100%, input power 1 W/cm2). After annealing in 450°C for 1 hr, the anodic bonding of MLCA and Si-wafer was successfully performed at 600 V, 400°C in - 760 mmHg. Then, the MLCA/Si bonded interface and fabricated Si diaphragm deflection characteristics were analyzed through the actuation and simulation test. It is possible to control with accurate deflection of Si diaphragm according to its geometries and its maximum non-linearity being 0.05-0.08 %FS. Moreover, any damages or separation of MLCA/Si bonded interfaces did not occur during actuation test. Therefore, it is expected that the anodic bonding technology of MLCA/Si wafers could be usefully applied for the fabrication process of high-performance piezoelectric MEMS devices.