Sheng-Ren Chiu

An Integrated Thermal Compensation System for MEMS Inertial Sensors

An active thermal compensation system for a low temperature-bias-drift (TBD) MEMS-based gyroscope is proposed in this study. First, a micro-gyroscope is fabricated by a high-aspect-ratio silicon-on-glass (SOG) process and vacuum packaged by glass frit bonding. Moreover, a drive/readout ASIC, implemented by the 0.25 μm 1P5M standard CMOS process, is designed and integrated with the gyroscope by directly wire bonding. Then, since the temperature effect is one of the critical issues in the high performance gyroscope applications, the temperature-dependent characteristics of the micro-gyroscope are discussed. Furthermore, to compensate the TBD of the micro-gyroscope, a thermal compensation system is proposed and integrated in the aforementioned ASIC to actively tune the parameters in the digital trimming mechanism, which is designed in the readout ASIC. Finally, some experimental results demonstrate that the TBD of the micro-gyroscope can be compensated effectively by the proposed compensation system.

A fully integrated circuit for MEMS vibrating gyroscope using standard 0.25um CMOS process

This paper presents an all-in-one fully integrated circuit solution for a vibrating micro-electromechanical gyroscope system using standard 0.25um 1P5M low voltage CMOS process. The analog parts of the system include a trans-impedance amplifier (TIA) with adaptive gain control (AGC) for the resonator driving loop, a sigma-delta modulator with gain/offset trimming function for the Coriolis signal read-out and a modified all PMOS charge pump for the high DC voltage. The digital signal processing parts include a trimming/control logic circuit and an I2C interface. SOG-bulk micromachining and deep reactive ion etching (DRIE) are adopted to fabricate the gyroscope sensor element with high aspect-ratio sensing structure and high yield. The experimental results indicate that the noise floor achieves 0.051° / s/ √Hz and the scale factor is 7mV/ °/s of the proposed two chip MEMS gyroscope system.

Design, fabrication and performance characterizations of an integrated dual-axis tuning fork gyroscope

This paper deals with the design, fabrication and preliminary experimental characterizations of a novel integrated dual-axis tuning fork gyroscope (DTFG). The DTFG is fabricated by high-aspect-ratio silicon-on-glass (SOG) process and vacuum packaged by glass frit bonding. Furthermore, a CMOS drive/readout ASIC chip, which is fabricated by a 0.25 μm 1P5M standard CMOS process, is integrated with the fabricated DTFG by directly wire-bonding. The experimental results of DTFG demonstrate that the rate sensitivities of Z-axis and X-axis sense modes are 1.47 mV/DPS and 0.18 mV/DPS respectively and the associated R2-linearity are 0.9995 and 0.9996. The noise-floors are 0.030 DPS/ Hz1/2 and 0.247 DPS/Hz1/2 for Z-axis and X-axis sense modes respectively.

Active thermal compensation of MEMS based gyroscope

This paper presents a new thermal compensation system for low temperature-bias-drift (TBD) MEMS based gyroscope. The temperature-dependent characteristics of proposed micro-gyroscope are firstly investigated and discussed in this work. The absolute temperature of the gyroscope is obtained by the frequency synthesizer, which is implemented by field programmable gate array (FPGA), in the thermal compensation system. Besides, the digital trimming mechanism, which implemented in CMOS readout ASIC, is actively tuned by the frequency synthesizer such that the temperature-bias-drift of gyrosocpe can be compensated. The experimental results shows that the temperature resolution of thermal compensation system is about 0.2° and the TBD of the uncompensated and compensated gyroscope is about 0.47 DPS/° and ±0.02 DPS/°.

A vibrating micro-resonator design for gyroscope applications using TIA

This paper presents a vibrating micro-resonator using transimpedance amplifier (TIA) for gyroscope applications. First, a gyroscope model is built for sensor design. The critical parameters are optimized by theoretical calculation and fine tuned by finite-element-analysis (FEM). Then, SOG-bulk micromachining and deep reactive ion etching (DRIE) are adopted to fabricate the gyroscope with high aspect-ratio sensing structure and high yield. Finally, an ASIC, TIA with large on-chip transimpedance is developed for driving loop to accomplish a self-oscillated micro-resonator.

Design of a thermal sensitive MEMS resonator and readout circuit for infrared sensing

This paper presents a novel thermal sensitive MEMS resonator (TSMR) and the readout circuit (ROIC) for uncooled infrared (IR) detection. The structure of the TSMR uses an optical resonance cavity co-constructed with a metal-oxide-metal (MIM) resonator to improve the IR sensing capability. The filling fraction and absorption coefficient of the micro-mechanical resonator can be up to 80%. In the ROIC design, the Maxwell-Wien bridge is adopted to detect the TSMRs impedance variation due to the IR radiation heating the resonator. A self-mixing mixer is also used to generate the corresponding dc output voltage for the following integrator and sample-and-hold circuit (SH) to do charge accumulation and hold the sampled-signal level. The simulated results show that the output voltage of the SH circuit is from 0.1 V to 2.3 V and the noise voltage is lower than 300 μVrms. The signal-to-noise ratio of the ROIC is higher than 77 dB.

Design, simulation and fabrication of MEMS Lorentz force sensor

This work deals with the MEMS electronic compass (e-compass) with the novel electrical signal decouple mechanism. The proposed e-compass includes of a resonant Lorentz-force magnetic sensor and a capacitive accelerometer. The accelerometer and magnetic sensor use the same mechanical structure to detect the acceleration and magnetic field. The corresponding readout circuits are designed and implemented by the standard 0.25um CMOS process. An equivalently diode-capacitor MEMS mechanical structure is proposed to suppress unexpected electrical AC and DC coupling. The prototype of the proposed sensor is with resonant frequency about 19.428 kHz and mechanical quality factor about 500. The preliminary results show that the output sensitivity is about 128 mV/Gauss and the corresponding R2-linearity is 0.9982 under current 2.39mA.

A miniature triaxial tactile sensor with calibratatele readout circuit

Industrial robot needed touch sensor to enhance the accuracy of the assembly and fabrication. In this paper, we designed and fabricated a novel tri-axial capacitive tactile sensor which can detect normal force and shear forces, simultaneously. The sensor consisted of a polymer bump, MEMS membrane, and readout circuit. The element of the sensor had individual sensing electrodes and polymer bump which can reduce the other-axis effect and enhance the sensitivity. The readout circuit calibrated the gain and offset of the output signal which can improve the error by the manufacture. The width and height of fabricated element are 950μm and 760μm, respectively. The measured sensitivities of the sensor with the calibratable readout circuit are 159 and 135mV/mN for the normal and shear force, respectively. The maximum other axis effect is 8.6% in the detection of normal force.

Design and experimental verifications of an integrated micro-gyroscope

An integrated Z-axis micro-gyroscope is proposed in this paper. At first, the details of the mechanical structure design and dynamical analysis of micro-gyroscope is thoroughly discussed. The proposed micro-gyroscope is fabricated by the proposed high-aspect-ratio silicon-on-insulator bulk micro-machining process and integrated with the CMO S drive/sense ASIC by direct wire bonding. Finally, the preliminary experimental results of the presented integrated micro-gyroscope are examined and discussed.

SOG micromechanical resonator utilizing single crystal Si and CMOS ASIC

In this paper, a micromechanical resonator utilizing single crystal Si and CMOS ASIC is presented. First, the critical parameters are optimized by theoretical calculation and fine tuned by finite-element-analysis (FEM). Then, SOG-bulk micromachining and deep reactive ion etching (DRIE) are adopted to fabricate the resonator as well as a glass wafer is used as the substrate to support the device, metal interconnections and signal I/O. The structure size of the designed resonator is 0.46 mm × 0.34 mm with 3 um minimum gap. Finally, a modified pierce oscillator ASIC and a temperature compensative methodology is developed to accomplish fully integrated reference oscillator design.