• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.3
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• pp.124-132
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• 2000

In this paper, presented are an active surface-micromachined silicon accelerometer, force rebalance loop using parametric robust control method, and experimental results with a real micromachined accelerometer. And finally, a robust controller of the form of PID compensator was designed to construct force rebalance loop. Through the frequency response analysis, it is shown that the loop guarantees appropriate stability and robustness. Experiments with a real accelerometer demonstrated that the proposed loop effectively controls the position of the accelerometer's proof mass. It also demonstrated that the resolution of the fabricated accelerometer is better than 1mg. Compared with a commercial accelerometer the proposed force rebalance silicon accelerometer showed better performances.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3301-3303
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• 1999

A new method of measuring residual stresses in micromachined films using beam or ring structures is proposed. Using the proposed method, more exact value of residual stress can be obtained without any ambiguities in conventional buckling method. Theoretical modeling with respect to this method is described, and experiment is performed. The structure and fabrication process in this paper are simple and widely used in surface micromachining. Therefore, it is possible to obtain a synchronous measurement. A synchronous and reason -able estimation of residual stresses in micromachined films enables us to obtain the prediction of more exact performance in micromachined devices.

• ETRI Journal
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• v.38 no.4
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• pp.685-694
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• 2016

A surface micromachined piezoresistive pressure sensor with a novel internal substrate vacuum cavity was developed. The proposed internal substrate vacuum cavity is formed by selectively etching the silicon substrate under the sensing diaphragm. For the proposed cavity, a new fabrication process including a cavity side-wall formation, dry isotropic cavity etching, and cavity vacuum sealing was developed that is fully CMOS-compatible, low in cost, and reliable. The sensitivity of the fabricated pressure sensors is 2.80 mV/V/bar and 3.46 mV/V/bar for a rectangular and circular diaphragm, respectively, and the linearity is 0.39% and 0.16% for these two diaphragms. The temperature coefficient of the resistances of the polysilicon piezoresistor is 0.003% to 0.005% per degree of Celsius according to the sensor design. The temperature coefficient of the offset voltage at 1 atm is 0.0019 mV and 0.0051 mV per degree of Celsius for a rectangular and circular diaphragm, respectively. The measurement results demonstrate the feasibility of the proposed pressure sensor as a highly sensitive circuit-integrated pressure sensor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.317-322
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• 2010

This paper reports the fabrication and characterization of surface micromachined poly 3C-SiC capacitive pressure sensors on silicon wafer operable in touch mode and normal mode for high temperature applications. FEM(finite elements method) simulation has been performed to verify the analytical mode. The sensing capacitor of the capacitive pressure sensor is composed of the upper metal and the poly 3C-SiC layer. Measurements have been performed in a temperature range from $25^{\circ}C$ to $500^{\circ}C$. Fabrication process of designed poly 3C-SiC touch mode capacitive pressure sensor was optimized and would be applicable to capacitive pressure sensors that are required high precision and sensitivity at high pressure and temperature.

• International Journal of Control, Automation, and Systems
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• v.5 no.1
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• pp.35-42
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• 2007

This paper presents an INS(Inertial Navigation System) grade, surface micro-machined differential resonant accelerometer(DRXL) manufactured by an epitaxially grown thick poly silicon process. The proposed DRXL system generates a differential digital output upon an applied acceleration, in which frequency transition is measured due to gap dependent electrical stiffness change. To facilitate the resonance dynamics of the electromechanical system, the micromachined DRXL device is packaged by using the wafer level vacuum sealing process. To test the DRXL performance, a nonlinear self-oscillation loop is designed based on the extended describing function technique. The oscillation loop is implemented using discrete electronic elements including precision charge amplifier and hard feedback nonlinearity. The performance test of the DRXL system shows that the sensitivity of the accelerometer is 24 Hz/g and its long term bias stability is about 2 mg($1{\sigma}$) with dynamic range of ${\sigma}70g$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.11 s.254
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• pp.1369-1375
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• 2006

In this work, mechanical characteristics of stainless steel diaphragm have been studied as a potential robust substrate and a diaphragm material for micromachined devices. Lamination process techniques combined with traditional micromachining processes have been adopted as suitable fabrication technologies. To illustrate these principles, capacitive pressure sensors based on a stainless steel diaphragm have been designed, fabricated and characterized. The fabrication process for stainless steel micromachined devices keeps the membrane and substrate being at the environment of 8.65MPa pressure and $175^{\circ}C$ for a half hour and then subsequently cooled to $25^{\circ}C$. Each sensor uses a stainless steel substrate, a laminated stainless steel film as a suspended movable plate and a fixed, surface micromachined back electrode of electroplated nickel. The finite element method is adopted to investigate residual stresses formed in the process. Besides, out-of-plane deflections are calculated under pressures on the diaphragm. The sensitivity of the device fabricated using these technologies is 9.03 ppm $kPa^{-1}$ with a net capacitance change of 0.14 pF over a range 0$\sim$180 kPa.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.529-536
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• 2001

We investigate a surface-micromachined capacitive accelerometer with the grid-type electrodes surrounded by a perforated proof-mass frame. An electromechanical analysis of the microaccelerometer has been performed to obtain analytical formulae for natural frequency and output sensitivity response estimation. A set of prototype devices has been designed and fabricated based on a 4-mask surface-micromachining process. The resonant frequency of 5.8$\pm$0.17kHz and the detection sensitivity of 0.28$\pm$0.03mV/g have been measured from the fabricated devices. The parasitic capacitance of the detection circuit with a charge amplifier has been measured as 3.34$\pm$1.16pF. From the uncertainty analysis, we find that the major uncertainty in the natural frequency of the accelerometer comes from the micromachining error in the beam width patterning process. The major source of the sensitivity uncertainty includes uncertainty of the parasitic capacitance, the inter-electrode gap and the resonant frequency, contributing to the overall sensitivity uncertainty in the portions of 75%, 14% and 11%, respectively.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.6
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• pp.354-359
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• 2000

A new method of measuring residual stress in micromachined film is proposed. An estimation of residual stress is performed by using least squares fit with an appropriate deflection modeling. an exact value of residual stress is obtained without any of the ambiguities that exist in conventional buckling method, and a good approximation is also obtained by using a few data points. Therefore, the test structures area could be greatly decreased by using this method. The measurement can be done more easily and simply without any actuation or any specific measuring equipment. The structure and fabrication processes described in this paper are simple and widely used in surface micromachining. In addition, in-situ measurement is available by using the proposed method when the test structure and the measurement structure are fabricated on a wafer simultaneously.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2389-2391
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• 2005

In this paper, a compact S type resonator is presented, where the proposed resonator is surface micromachined over transmission lines or other resonators, in order to obtain a wide range of possible electromagnetic couplings. The structure has been applied in two compact, bandstop and bandpass filters with moderate fractional bandwidths (FBW) of 20% and 25% respectively. The bandstop filter presented, was designed by the combination of two design methods in order to obtain the proposed fractional bandwidth, where traditionally, coupled resonator bandstop filters have been used for narrow stopbands. The bandpass filter illustrates the use of the proposed suspended resonator structure to obtain a wide range of electric type coupling coefficients, and external quality factors for the filter. This paper describes the design methodology, concepts and fabrication method proposed for the design of these filters.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.1
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• pp.45-51
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• 2005

We have developed surface micromachined Infrared ray (IR) focal plane array (FPA), in which single $SiO_{2}$ layer works as an IR absorbing plate and $Pb(Zr_{0.3}Ti_{0.7})O_{2}$ thin film served as a thermally sensitive material. There are some advantages of applying $SiO_{2}$ layer as an IR absorbing layer. First of all, the $SiO_{2}$ has good IR absorbance within $8{\sim}12{\mu}m$ spectrum range. Measured value showed about 60% absorbance of incident IR spectrum in the range. $SiO_{2}$ layer has another important merit when applied to the top of Pt/PZT/Pt stack because it works also as a supporting membrane. Consequently, the IR absorbing layer forms one body with membrane structure, which simplifies the whole MEMS process and gives robustness Ito the structure.