• Structural Engineering and Mechanics
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• v.35 no.4
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• pp.387-407
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• 2010

In this paper, using perturbation and Galerkin method, the response of a resonant viscoelastic microbeam to an electric actuation is obtained. The microbeam is under axial load and electrical load. It is assumed that midplane is stretched, when the beam is deflected. The equation of motion is derived using the Newton's second law. The viscoelastic model is taken to be the Kelvin-Voigt model. In the first section, the static deflection is obtained using the Galerkin method. Exact linear symmetric mode shape of a straight beam and its deflection function under constant transverse load are used as admissible functions. So, an analytical expression that describes the static deflection at all points is obtained. Comparing the result with previous research show that using deflection function as admissible function decreases the computation errors and previous calculations volume. In the second section, the response of a microbeam resonator system under primary and secondary resonance excitation has been obtained by analytical multiple scale perturbation method combined with the Galerkin method. It is shown, that a small amount of viscoelastic damping has an important effect and causes to decrease the maximum amplitude of response, and to shift the resonance frequency. Also, it shown, that an increase of the DC voltage, ratio of the air gap to the microbeam thickness, tensile axial load, would increase the effect of viscoelastic damping, and an increase of the compressive axial load would decrease the effect of viscoelastic damping.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.611-614
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• 2018

Laminate composites composed of $0.95Pb(Zr_{0.52}Ti_{0.48})O_3-0.05Pb(Mn_{1/3}Sb_{2/3})O_3$ piezoelectric ceramic and Fe-Si-B based magnetostrictive amorphous alloy are fabricated, and the effect of control of the areal dimensions and the thickness of the piezoelectric layer on the magnetoelectric(ME) properties of the laminate composites is studied. As the aspect ratio of the piezoelectric layer and the magnetostrictive layer increases, the maximum value of the ME voltage coefficient(${\alpha}_{ME}$) increases and the intensity of the DC magnetic field at which the maximum ${\alpha}_{ME}$ value appears decreases. Moreover, as the thickness of the piezoelectric layer decreases, ${\alpha}_{ME}$ tends to increase. The ME composites exhibit ${\alpha}_{ME}$ values higher than $1Vcm^{-1}Oe^{-1}$ even at the non-resonance frequency of 1 kHz. This study shows that, apart from the inherent characteristics of the piezoelectric composition, small thicknesses and high aspect ratios of the piezoelectric layer are important dimensional determinants for achieving high ME performance of the piezoelectric-magnetostrictive laminate composite.

• Korean Journal of Materials Research
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• v.31 no.3
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• pp.162-171
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• 2021

Dry etching of copper thin films is performed using high density plasma of ethylenediamine (EDA)/hexafluoroisopropanol (HFIP)/Ar gas mixture. The etch rates, etch selectivities and etch profiles of the copper thin films are improved by adding HFIP to EDA/Ar gas. As the EDA/HFIP concentration in EDA/HFIP/Ar increases, the etch rate of copper thin films decreases, whereas the etch profile is improved. In the EDA/HFIP/Ar gas mixture, the optimal ratio of EDA to HFIP is investigated. In addition, the etch parameters including ICP source power, dc-bias voltage, process pressure are varied to examine the etch characteristics. Optical emission spectroscopy results show that among all species, [CH], [CN] and [H] are the main species in the EDA/HFIP/Ar plasma. The X-ray photoelectron spectroscopy results indicate the formation of CuCN compound and C-N-H-containing polymers during the etching process, leading to a good etch profile. Finally, anisotropic etch profiles of the copper thin films patterned with 150 nm scale are obtained in EDA/HFIP/Ar gas mixture.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.769-772
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• 2005

This paper describes a low-voltage and low-power channel selection analog front end with continuous-time low pass filters and highly linear programmable-gain amplifier(PGA). The filters were realized as balanced Gm-C biquadratic filters to achieve a low current consumption. High linearity and a constant wide bandwidth are achieved by using a new transconductance(Gm) cell. The PGA has a voltage gain varying from 0 to 65dB, while maintaining a constant bandwidth. A filter tuning circuit that requires an accurate time base but no external components is presented. With a 1-Vrms differential input and output, the filter achieves -85dB THD and a 78dB signal-to-noise ratio. Both the filter and PGA were implemented in a 0.18um 1P6M n-well CMOS process. They consume 3.2mW from a 1.8V power supply and occupy an area of $0.19mm^2$.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.535-538
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• 1994

In this paper, an isolated ZVS-PWM boost converter is proposed for single stage line conversion. For power factor correction, we used the half bridge topology at the primary side of isolation transformer permitting switching devices to operate under ZVS by using circuit parastics and operating at a fixed duty ratio near 50%. Thus the relatively continuous input current distortion and small size input filter are also achievable. The ZVS-PWM boost operation of the proposed converter can be achieved by using the boost inductor $L_f$, main switch $Q_3$, and simple auxiliary circuit at the secondary side of isolation transformer. The secondary side circuit differ from a conventional PWM boost converter by introduction a simple auxiliary circuit. The auxiliary circuit is actived only during a short switching transition time to create the ZVS condition for the main switch as that of the ZVT-PWM boost converter. With a single stage, it is possible to achieve a sinusoidal line current at unity power factor as well as the isolated 48V DC output. Comparing to the two stage schemes, overall effiency of the proposed converter is highly improved due to the effective ZVS of all devices as well as single stage power conversion. Thus, it can be operated at high switching frequency allowing use of small size input filter. Minimum voltage and current stress make it high power application possible.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.1
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• pp.39-44
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• 2003

As the portable electronic equipments are developed and popularized, the batteies are more important. To prolong life of the equipments, engineers demand to have batteries of high-power density and they are used to use Li-ion batteries popularly Li-ion batteries are better than conventional batteries, Ni-cd, about power density per volume and weight, but they have a fault that discharge voltage of them goes down. In order to maximize life of the Li-ion batterries, we have to use a converter which is suitable for the characteristic of Li-ion batteries. Therefore, capacitive idling SEPIC(Single Ended Primary Inductance Converter) that is derived from the SEPIC topology is proposed as a source of the Portable low-power applications. The converter has characteristics of buck-boost porformance. Besides, that makes it possible to increase the switching frequency by partial soft commutation of power switches through adding a diode and a switch. This paper is presented the characteristics, DC voltage conversion ratio, circuits of operation modes, of the converter and it is analized and implemented.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.6
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• pp.297-301
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• 2006

In the present work, we investigate the characteristics of new composition material, chalcogenide $Ge_1Se_1Te_2$ material in order to overcome the problems of conventional PRAM devices. The Tc of $Ge_1Se_1Te_2$ bulk was measured $231.503^{\circ}C$ with DSC analysis. For static DC test mode, at low voltage, two different resistances are observed. depending on the crystalline state of the phase-change resistor. In the first sweep, the as-deposited amorphous $Ge_1Se_1Te_2$ showed very high resistance. However when it reached the threshold voltage(about 11.8 V), the electrical resistance of device was drastically reduced through the formation of an electrically conducting path. The phase transition between the low conductive amorphous state and the high conductive crystal]me state was caused by the set and reset pulses respectively which fed through electrical signal. Set pulse has 4.3 V. 200 ns. then sample resistance is $80\sim100{\Omega}$. Reset pulse has 8.6 V 80 ns, then the sample resistance is $50{\sim}100K{\Omega}$. For such high resistance ratio of $R_{reset}/R_{set}$, we can expect high sensing margin reading the recorded data. We have confirmed that phase change properties of $Ge_1Se_1Te_2$ materials are closely related with the structure through the experiment of self-heating layers.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.2
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• pp.47-55
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• 2012

A discrete-time(DT) filter with high-order temporal moving average(TMA) using actively-weighted charge sampling is proposed in this paper. To obtain different weight of sampled charge, the variable transconductance OTA is used prior to charge sampler, and the ratio of charge can be effectively weighted by switching the control transistors in the OTA. As a result, high-order TMA operation can be possible by actively-weighted charge sampling. In addition, the transconductance generated by the OTA is relatively accurate and stable by using the size ratio of the control transistors. The high-order TMA filter has small size, increased voltage gain, and low parasitic effects due to the small amount of switches and sampling capacitors. It is implemented in the TSMC $0.18-{\mu}m$ CMOS process by TMA-$2^2$. The simulated voltage gain is about 16.7 dB, and P1dB and IIP3 are -32.5 dBm and -23.7 dBm, respectively. DC current consumption is about 9.7 mA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.190-194
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• 2002

In this study, the etching of Au thin films have been performed in an inductively coupled CF4/Cl2/Ar plasma. The etch properties were measured as the CF4 adds from 0 % to 30 % to the Cl2/(Cl2 + Ar) gas mixing ratio of 0.2. Other parameters were fixed at a rf power of 700 W, a dc bias voltage of 150 V, a chamber pressure of 15 mTorr, and a substrate temperature of $30^{\circ}C$. The highest etch rate of the Au thin film was 370 nm/min at a 10 % additive CF4 into Cl2/(Cl2 + Ar) gas mixing ratio of 0.2. The surface reaction of the etched Au thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. From x-ray photoelectron spectroscopy (XPS) analysis, the intensities of Au peaks are changed. There is a chemical reaction between Cl and Au. Au-Cl is hard to remove on the surface because of its high melting point and the etching products can be sputtered by Ar ion bombardment. We obtained the cleaned and steep profile.

• ETRI Journal
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• v.24 no.3
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• pp.211-220
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• 2002

This study characterizes an oxide etching process in a magnetically enhanced reactive ion etching (MERIE) reactor with a $CHF_3/CF_4$ gas chemistry. We use a statistical $2^{4-1}$ experimental design plus one center point to characterize the relationships between the process factors and etch responses. The factors that we varied in the design include RF power, pressure, and gas composition, and the modeled etch responses were the etch rate, etch selectivity to TiN, and uniformity. The developed models produced 3D response plots. Etching of $SiO_2$ mainly depends on F density and ion bombardment. $SiO_2$ etch selectivity to TiN sensitively depends on the F density in the plasma and the effects of ion bombardment. The process conditions for a high etch selectivity are a 0.3 to 0.5 $CF_4$ flow ratio and a -600 V to -650 V DC bias voltage according to the process pressure in our experiment. Etching uniformity was improved with an increase in the $CF_4$ flow ratio in the gas mixture, an increase in the source power, and a higher pressure. Our characterization of via etching in a $CHF_3/CF_4$ MERIE using neural networks was successful, economical, and effective. The results provide highly valuable information about etching mechanisms and optimum etching conditions.