A Polysilicon Capacitive Microaccelerometer with Unevenly Distributed Comb Electrodes

We present a surface-micromachined polysilicon capacitive accelerometer using unevenly distributed comb electrodes. The unique features of the accelerometer include a perforated proof-mass and the inner and outer comb electrodes with uneven electrode gaps. The perforated proof-mass reduces stiction between the structure and the substrate and the unevenly distributed electrodes shorten the electrode length required for a given sensitivity. The polysilicon accelerometer has been fabricated by the conventional 6-mask surface-micromachining process and showes a sensitivity of 1.03mV/g with a hybrid detection circuitry

A Magnetic Microsensor based on the Hall Effect in an AC Microplasma

This paper presents a new class of magnetic microsensors based on the Hall effect in AC microplasma. In the theoretical study, we develop a simple model of the plasma Hall sensor and express the plasma Hall voltage as a function of magnetic field, plasma discharge field, pressure, and electrode geometry. On this basis, we have designed and fabricated magnetic microsensors using AC neon plasma. In the experiment, we have measured the Hall voltage output of the plasma microsensors for varying five different conditions, including the frequency and the magnitude of magnetic field, the frequency and the magnitude of plasma discharge voltage, and the neon pressure. The fabricated magnetic microsensors show a magnetic field sensitivity of 8.87±0.18㎷/G with 4.48% nonlinearity

Electrical Noise Reduction and Stiffness Increase with Self Force-Balancing Effect in a High-Resolution Capacitive Microaccelerometer using Branched Finger Electrodes with High-Amplitude Sense Voltage

high-amplitude sense voltage. From the fabricated microacceleromcter, the total noise is obtained as 9 ㎍/√Hz at the sense voltage of 16.5V, while the conventional microaccelerometers have shown the noire level of 25~800 ㎍/√Hz. We reduce the mechanical noise level of the microaccelerometer by increasing the proof-class based on deep RIE process of an SOI wafer. We reduce the electrical noise level by increasing the amplitude of AC sense voltage. The nonlinearity problem caused by the high-amplitude sense volage has been solved by a new electrode design of branched finger type, resulting in self force-balancing effects for the enhanced linearity and bandwidth. The fabricated microaccelerometer shows the electrical noise of 2.4 ㎍/√Hz at the sense voltage of 16.5V, which is an order of magnitude reduction of the electrical noise of 24.3 ㎍/√Hz measured at 0.9V. For the sense voltage higher than 2V, the electrical noise of the microaccelerometer is lower than the voltage-independent mechanical noise of 11 ㎍/√Hz. Total noise, composed of the electrical noise and the mechanical noire, has been measured as 9 ㎍/√Hz at the sense voltage of 16.5V, which is 31% of the total noise of 28.6 ㎍/√Hz at the sense voltage 0.9V. The self force-balancing effect in the blanched finger electrodes increases the stiffness of the microaccelerometer from 1.1N/m to 1.61N/m as the sense voltage increases from 0V to 17.8V, thereby generating additional stiffness at the rate of 0.0016±0.0008 N/m/V2

High-resolution Capacitive Microaccelerometers using Branched Finger Electrodes with High-Amplitude Sense Voltage

This paper presents a navigation garde capacitive microaccelerometer, whose low-noise high-resolution detection capability is achieved by a new electrode design based on a high-amplitude anti-phase sense voltage. We reduce the mechanical noise of the microaccelerometer to the level of 5.5㎍/(equation omitted) by increasing the proof-mass based on deep RIE process of an SOI wafer. We reduce the electrical noise as low as 0.6㎍/(equation omitted) by using an anti-phase high-amplitude square-wave sense voltage of 19V. The nonlinearity problem caused by the high-amplitude sense voltage is solved by a new electrode design of branched finger type. Combined use of the branched finger electrode and high-amplitude sense voltage generates self force-balancing effects, resulting in an 140％ increase of the bandwidth from 726㎐ to 1,734㎐. For a fixed sense voltage of 10V, the total noise is measured as 2.6㎍/(equation omitted) at the air pressure of 3.9torr, which is the 51％ of the total noise of 5.1㎍/(equation omitted) at the atmospheric pressure. From the excitation test using 1g, 10㎐ sinusoidal acceleration, the signal-to-noise ratio of the fabricated microaccelerometer is measured as 105㏈, which is equivalent to the noise level of 5.7㎍/(equation omitted). The sensitivity and linearity of the branched finger capacitive microaccelerometer are measured as 0.638V/g and 0.044％, respectively

Potational Viscous Damping of On-substrate Micromirrors

In this paper, we present theoretical and experimental study on the viscous damping of the on-substrate torsional micromirrors, oscillating near the silicon substrates. In this theoretical study, we develop theoretical models and test structures for the viscous damping of the on-substrate torsional micromirrors. From a finite element analysis, we estimate the theoretical damping coefficients of the torsional micromirrors. From a finite element analysis, we estimate the theoretical damping coefficients of the torsional micromirrors, fabricated by the surface-micromaching process. From the electrostatic test of the fabricated devices, frequency-dependent rotationalvelocity of the micromirrors has been measured at the atmospheric pressure using devices, frequency-dependent rotational velocity of the micromirrors has been measured at the atmospheric pressure using the Mach-Zehnder interferometer system. Experimental damping coefficients have been extracted from the least square fit of the measured rotational velocity within the filter bandwidth of 150 kHz. We have compared the theoretical values and the experimental results on the dynamic performance of the micromirrors. The theoretical analysis overstimates the resonant frequency in the amount of 15%, while underestimating the viscous damping in the factors of 10%

Novel TFT with active layer buried in glass substrate

학위논문(석사) - 한국과학기술원 : 전기 및 전자공학과, 1996.2, [ iv, 56 p. ]한국과학기술원 : 전기 및 전자공학과