This paper presents the design, simulation, fabrication and experiment of a triaxial accelerometer based on differential resonant beams and force-balanced capacitive plates. The triaxial accelerometer is composed of a proof mass, four bridge resonators with both end clamped and operating in flexure vibration mode, four L-type supporting beams, a top plate and a bottom plate. The in-plane acceleration are measured by bridge resonators. The gravity centre of the proof mass and the neutral layer of L-type supporting beams are located within a same plane to minimize the rotation of the proof mass subjected to in-plane acceleration. The cross-axis sensitivities of X-axis and Y-axis resonant beams under lateral in-plane acceleration are 1.97% and 1.71%, respectively. A force-balanced differential plate capacitor composed of a proof mass, a top plate and a bottom plate is used to detect acceleration along Z-axis. The small displacement of the proof mass in the normal direction of the chip reduces the cross-axis sensitivity of the bridge resonators subjected to acceleration along Z-axis. The complementation of resonance detection mechanism and the force balance capacitance mode makes the triaxial accelerometer exhibit low cross-axis sensitivity. The simulated and experimental results prove this conclusion.

Microcantilever with integrated piezoresistor has been applied to in situ surface stress measurement in the field of biochemical sensors. It is well known that piezoresistive cantilever-based sensors are sensitive to ambient temperature changing due to highly temperature-dependent piezoresistive effect and mismatch in thermal expansion of composite materials. This paper proposes a novel method of temperature drift compensation for microcantilever-based sensors with a piezoresistive full Wheatstone bridge integrated at the clamped ends by subtracting the amplified output voltage of the reference cantilever from the output voltage of the sensing cantilever through a simple temperature compensating circuit. Experiments show that the temperature drift of microcantilever sensors can be significantly reduced by the method.

Although plasma enhanced chemical vapor deposition (PECVD) silicon nitride (Si _x N _y ) films have been extensively investigated by many researchers, requirements of film properties vary from device to device. For some applications utilizing Si _x N _y film as the mask Layer for deep wet etching of the silicon, it is very desirable to obtain a high quality film. In this study, Si _x N _y films were deposited on silicon substrates by PECVD technique from the mixtures of NH₃ and 5% SiH₄ diluted in Ar. The deposition temperature and RF power were fixed at 400 °C and 20 W, respectively. By adjusting the SiH₄/NH₃ flow ratio, Si _x N _y films of different compositions were deposited on silicon wafers. The stoichiometry, residual stress, etch rate in 1:50 HF, BHF solution and 40% KOH solution of deposited Si _x N _y films were measured. The experimental results show that the optimum SiH₄/NH₃ flow ratio at which deposited Si _x N _y films can perfectly protect the polysilicon resistors on the front side of wafers during KOH etching is between 1.63 and 2.24 under the given temperature and RF power. Polysilicon resistors protected by the Si _x N _y films can withstand 6 h 40% KOH double-side etching at 80 °C. At the range of SiH₄/NH₃ flow ratios, the Si/N atom ratio of films ranges from 0.645 to 0.702, which slightly deviate the ideal stoichiometric ratio of LPCVD Si₃N₄ film. In addition, the silicon nitride films with the best protection effect are not the films of minimum etch rate in KOH solution.