Jiao Jiwei

A digital demodulation solution to achieve stable driving for a micro-machined gyroscope with an AGC mechanism

This paper presents a digital solution to restrain the impact of the unwanted low-frequency signal on the practical driving signal, i.e. carrier signal, in a MEMS gyroscope with automatic gain control (AGC) mechanism. For this purpose, an ASIC has been designed and fabricated. With digital signal processing (DSP) techniques, the digital demodulated angular rate signal is adjusted by using a self-multiplied practical carrier signal after LPF in a digital divider. The simulation gives an SNR of better than 70 dB, which indicates that good device performance can be possibly achieved with this principle even though the driving is not ideal.

Doubly Clamped Nanobeam as a Piezoresistive Mass Sensor

In this paper, we present a novel technology to realize a doubly clamped nanobeam, which is preferred to cantilever because of its higher natural frequency with a same dimension, as a piezoresistive mass sensor. Ar selective bombardment was applied on a 200 nm thick doubly clamped nanobeam to form a piezoresistor in a Wheaston bridge along with other ordinary resistors. The device was electrostatically actuated and readout piezoresistively. The achieved merit product of Q-factor and f0 in air is as high as 3.5 times 108 , which hints a better mass detection resolution compared with its counterpart of micro cantilever, while our approach is simple and easily controlled.

Fast pore etching on high resistivity n-type silicon via photoelectrochemistry

In this paper, five factors, namely the HF (hydrofluoric acid) concentration, field strength, illumination intensity as well as the oxidizing-power and conductivity of electrolytes were found to strongly affect the fast pore etching. The oxidizing power of aqueous HF electrolyte of different concentrations was especially measured and analysed. A positive correlation between optimal bias and HF concentration was generally observed and the relationship was semi-quantitatively interpreted. Pore density notably increased with enhanced HF-concentration or bias even on patterned substrates where 2D (two-dimensional) nuclei were densely pre-textured. The etch rate can reach 400 μm/h and the aspect ratio of pores can be readily driven up to 250.

Observation of a diverse deviation from macropore-formation theory in silicon electrochemistry

Via anodizing patterned and unpatterned samples with a high HF concentration ([HF]), the degree of deviation from pore-formation theory was found to be markedly different. Based on the analysis of scanning electron microscope (SEM) micrographs and current–voltage (I – V) curves, the variation of physical and chemical parameters of patterned and unpatterned substrates was found to be crucial to the understanding of the observations. Our results indicate that the initial surface morphology of samples can have a considerable influence upon pore formation. The electric-field effect as well as current-burst-model was employed to interpret the underlying mechanism.

Novel all-light optically readable thermal imaging sensor based on MEMS technology

This paper presents a novel all-light optically readable thermal imaging sensor based on the bulk-MEMS technology. The sensor contains a focal plane array (FPA) consisting of m /spl times/ n movable micromirrors supported by bimaterial beams. As infrared radiation applied on FPA, a temperature gradient generated on the bimaterial beams leads to the deflection of beams and resulting in proportional displacement of this movable micromirror. A visible optical system is used to measure the displacement of the movable micromirrors of the FPA using Fabry-Perot interferometry. Our Al/SiO/sub 2/ micromirror structure is optimized to achieve a thermo-mechanical sensitivity of 10/sup -8/m/K. The FPA consisting of 50/spl times/ 50 movable micromirror array has been successfully fabricated by using bulk MEMS technology.