Xingguo Xiong

A dual-mode built-in self-test technique for capacitive MEMS devices

A built-in self-test (BIST) scheme which partitions the fixed (instead of movable) capacitance plates of a capacitive MEMS device is proposed. The BIST technique divides the fixed capacitance plate(s) at each side of the movable microstructure into three portions: one for electrostatic activation and the other two equal portions for capacitance sensing. Due to such partitioning, the BIST technique can be applied to surface-, bulk-micromachined MEMS devices and other technologies. Further, sensitivity and symmetry BIST methods based on this partitioning are also introduced. The combination of both BIST modes covers a larger defect set, thus a robust testing for the device can be expected. The BIST technique is verified by three typical capacitive MEMS devices. Simulation results show that the proposed technique is an effective BIST solution for various capacitive MEMS devices.

Design and analysis of self-repairable MEMS accelerometer

In this paper, a self-repairable MEMS (SRMEMS) accelerometer design is proposed. The accelerometer consists of (n + m) identical modules: n of them serve as the main device, while the remaining m modules act as the redundancy. If any of the working module in the main device is found faulty, the control circuit will replace it with a good redundant module. In this way, the faulty device can be self-repaired through redundancy. The sensitivity loss due to device modularization can be well compensated by different design alternatives. The yield model for MEMS redundancy repair is developed. The simulation results show that the BISR (built-in self-repair) design leads to effective yield increase compared to nonBISR design, especially for a moderate nonBISR yield. By implementing the fault tolerance feature into MEMS devices, the yield as well as the reliability of a MEMS device implemented in a SoC can be improved.

Reliability Analysis of Self-Repairable MEMS Accelerometer

MEMS (micro electromechanical system) yield and reliability have been a very critical issue. In our previous paper, the authors have proposed a self-repairable MEMS comb accelerometer device, and the yield analysis has demonstrated effective yield increase due to the BISR (built-in self-repair) design. In this paper, the authors developed a MEMS reliability model for quantitative assessment of the MEMS reliability analysis. Based on this model, analysis of the reliability of both non-BISR and BISR MEMS comb accelerometers under z-axis shocking environment. Simulation results demonstrate very effective reliability enhancement due to the BISR design. The reliability model can also be applied to other MEMS devices under various failure mechanisms in a similar way

Balance-approach for load–displacement measurement of microstructures

Abstract A simple and effective method using a balance to measure micro force and corresponding deflection is presented. The method is proved to be very practical in testing the force–deflection behavior of silicon cantilever, in which the Youngs modulus of the material can be calculated, and in investigating the static performance of bulk micromachined capacitive accelerometers. The same value of the Youngs modulus was obtained on much different microstructures including the single silicon cantilevers and the beam-island structures of capacitive accelerometers. The balance approach for micro force–displacement measurement is very attractive for its easiness in operation, low cost and higher resolution.

A bulk-micromachined comb accelerometer with floating interconnects

In this paper, a silicon-on-glass bulk-micromachined comb accelerometer with floating interconnect is introduced. The device uses unique floating back interconnect for the connection of the fixed comb fingers, which leads to more compact design. Based upon the analysis of the device behavior, an optimized device design is proposed. Simulation results show that the device has a static capacitance of 2.8pF and sensitivity of 17.9nm/g. The fabrication sequence of the accelerometer is discussed. The floating interconnection technique may be applied to other bulk-micromachined MEMS devices for 3D interconnection

Balance-approach for mechanical properties test of micro fabricated structure

A simple and effective method using a balance to measure micro force and corresponding deflection is presented. The method is proved to be very practical in testing the force-deflection behavior of silicon cantilever, in which the Youngs modulus of the material can be calculated, and in investigating the static performance of bulk micromachined capacitive accelerometers. The balance approach for micro force- displacement measurement is very attractive for its easiness in operation, low cost and higher resolution.

Structure design and fabrication of symmetric force-balance micromachining capacitive accelerometer

A novel KOH silicon maskless anisotropic etching technology is adopted to fabricate micromachining silicon mass-beam structure accelerometer. Lateral sensitivity effect in normal accelerometer is eliminated because the beams which are thinner than 15 micrometers have been formed in the middle of the seismic mass. Based on the calculation of sensitivity and basic resonance frequency of two kinds of bulk micromachining accelerometers, the structure parameters of cantilever and double-side-supported accelerometer have been optimized by using the sensitivity-frequency product as the figure of merit of a structure. The different etching characteristics of {311} and {100} plane of silicon in KOH maskless anisotropic etching process have been investigated thoroughly and utilized in the fabrication of symmetric mass- beam structure. Special damping design has been proposed to reduce the damping ratio of the device in order to improve the dynamic performance of the accelerometer. Preliminary measurement of the static characteristics of the structure has been performed with a force-deflection balance measurement apparatus.

Prototyping of Robotic Systems: Applications of Design and Implementation

As a segment of the broader science of automation, robotics has achieved tremendous progress in recent decades due to the advances in supporting technologies such as computers, control systems, cameras and electronic vision, as well as micro and nanotechnology. Prototyping a design helps in determining system parameters, ranges, and in structuring an overall better system. Robotics is one of the industrial design fields in which prototyping is crucial for improved functionality.Prototyping of Robotic Systems: Applications of Design and Implementation provides a framework for conceptual, theoretical, and applied research in robotic prototyping and its applications. Covering the prototyping of various robotic systems including the complicated industrial robots, the tiny and delicate nanorobots, medical robots for disease diagnosis and treatment, as well as the simple robots for educational purposes, this book is a useful tool for those in the field of robotics prototyping and as a general reference tool for those in related fields.

MEMS Yield Simulation with Monte Carlo Method

In this paper, Monte Carlo method is used for the simulation of point-stiction defects in MEMS accelerometer devices. The yield of MEMS devices is estimated based on the simulation results. Comparison between simulated yields of BISR/non-BISR MEMS accelerometers demonstrates effective yield increase due to self-repairable design. The simulation results of yield increase versus different initial yields for BISR MEMS accelerometers are in good agreement with theoretical prediction based on previous MEMS yield model. This verifies the correctness of the MEMS yield model.

Design and simulation of aluminum bifunctional spatial light modulator

In this paper, a bifunctional aluminum MEMS spatial light modulator (micromirror) device design is introduced. The bifunctional mirror can work in both torsional and piston modes, depending on the voltage applied to the bottom driving electrodes. The mirror was fabricated with thick photoresist sacrificial layer technique. The working principle and performance of the micromirror are analyzed. Based upon the analysis, an optimized micromirror design is proposed. The mirror can deflect for a maximum displacement of 1.3/spl mu/m in its piston mode, and rotate for a maximum angle of 3.1/spl deg/ in its torsional mode. The micromirror can be used to modulate the phase as well as the direction of the incident light due to its bifunctional modes.