• Transactions on Electrical and Electronic Materials
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• 제14권3호
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• pp.116-120
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• 2013

This paper proposes a novel RF MEMS dc-contact switch with stiff membrane on a quartz substrate. The uniqueness of this work lies in the utilization of a seesaw mechanism to restore the movable part to its rest position. The switching action is done by using separate pull-down and pull-up electrodes, and hence operation of the switch does not rely on the elastic recovery force of the membrane. One of the main problems faced by electrostatically actuated MEMS switches is the high operational voltages, which results from bending of the membrane, due to internal stress gradient. This is resolved by using a stiff and thick membrane. This membrane consists of flexible meanders, for easy movement between the two states. The device operates with an actuation voltage of 6.43 V, an insertion loss of -0.047 dB and isolation of -51.82 dB at 2 GHz.

• Transactions on Electrical and Electronic Materials
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• 제17권2호
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• pp.86-91
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• 2016

Ever increasing demand for microwave operated applications has cultivated need for high-performance universal systems capable of working on multi-bands. This objective can be realized using Multi-Dielectrics in RF MEMS capacitive switch. In this study, we present a detailed analysis of the effect of various dielectrics on switch performance. The design consists of a capacitive switch and performance is analyzed by changing the dielectric layers beneath the switch. The results are obtained using three different dielectrics including Silicon nitride (7.6), Hafnium dioxide (25) and Titanium oxide (50). Testing of proposed switch yields high isolation (- 87.5 dB) and low insertion loss (- 0.1 dB at 50 GHz) which is substantially better than the conventional switches. The operating bandwidth of the proposed switch (DC to 95 GHz) makes it suitable for wide band microwave applications.

• JSTS:Journal of Semiconductor Technology and Science
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• 제2권4호
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• pp.237-245
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• 2002

A new type of RF MEMS switch for low voltage actuation, high broadband application and high power capability is presented. Mechanical and electromagnetic simulations of this new RF MEMS switch type are shown and the fabrication process and measurement results are given. The switching element consists of a cantilever which is fixed by a suspension spring to the ground of the coplanar line. The closing voltage is 16V. The switches exhibit low insertion loss (<0.85dB@30GHz) with good isolation (>22dB@30GHz).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.282-283
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• 2007

본 논문에서는 저전압에서 구동 할 수 있는 압전구동 방식의 RF MEMS 스위치를 설계하였다. 설계는 유한요소기법(FEM)을 지원하는 시뮬레이터 (ConventorWare)를 사용하여 수행하였고, 이를 바탕으로 deflection, contact force, stress 등 기계적인 해석을 함으로써 최적화된 설계를 할 수 있었다. 이번 설계에서는 적절한 contact force를 유지하면서 hinge에서 받는 stress를 최소화하기 위하여 구동기를 2개 사용한 듀얼형식의 모델을 제안하였고, hinge의 모양은 'ㄷ'로 하여 deflection을 향상시켰다. 이 듀얼형식의 최적화된 모델은 signal line과 contact pad 간의 gap이 3.4${\mu}m$일 때, 최초 2.8V에서 contact이 이루어졌으며, 5V에서 12.4${\mu}N$의 contact force와 116MPa의 stress를 얻었고, 차후, SP4T나 SP6T 등의 설계시 공간 효율이 높은 다양한 형태의 구조를 설계할 수 있다.

• Transactions on Electrical and Electronic Materials
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• 제14권5호
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• pp.225-230
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• 2013

This paper presents a novel shunt radio frequency microelectromechanical system switch on a quartz substrate with stiff ribs around the membrane. The buckling effects in the switch membrane and stiction problem are the primary concerns with RF MEMS switches. These effects can be reduced by the proposed design approach due to the stiffness of the ribs around the membrane. A lower mass of the beam and a reduction in the squeeze film damping is achieved due to the slots and holes in the membrane, which further aid in attaining high switching speeds. The proposed switch is optimized to operate in the k-band, which results in a high isolation of -40 dB and low insertion loss of -0.047 dB at 21 GHz, with a low actuation voltage of only 14.6 V needed for the operation the switch. The membrane does not bend with this membrane design approach. Finite element modeling is used to analyze the stress and pull-in voltage.

• 한국통신학회논문지
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• 제35권11A호
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• pp.1091-1096
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• 2010

Stiction in microelectromechanical systems (MEMS) has been a major failure mechanism. Especially, in RF MEMS switches, moving parts often suffered in-use and release related stiction problems. Some materials and methods have been used to prevent this problem. Diamond-like carbon (DLC) has not only been used as a protective material owing to its good mechanical properties but also has been used as a hydrophobic material. Its properties could be controlled by post annealing treatment in various conditions. We synthesized DLC films using a radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gas. Then, the change of the hydrophobic property of the films was investigated undervarious annealing temperatures in nitrogen and in oxygen ambient. The films, that were annealed above $700^{\circ}C$ in nitrogen ambient, showed a high contact angle of water (> $90^{\circ}$) even though their mechanical property was sacrificed to some degree. The structural variation and the changes of the hydrophobic and mechanical properties of the DLC films were analyzed by Raman spectrum, contact angle measurement, surface profiler, and a nanoindentation test.

• 한국위성정보통신학회논문지
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• 제6권1호
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• pp.28-31
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• 2011

본 논문에서는 d33 모드로 구동하여 우수한 성능을 가지는 RF-MEMS 스위치의 구현을 위한 희생층과 구조층의 조합으로서 DLC와 포토레지스트를 제안하였다. 포토레지스트의 경화현상을 방지하기 위하여 DLC 구조층은 상온에서 RF-PECVD 방법을 이용하여 증착하였다. 그리고 PZT 압전층은 RF 마그네트론 스퍼터링 방법을 이용하여 상온에서 구조층 위에 증착하였으며, 희생층의 제거 후 결정화를 위하여 급속 열처리 (RTA) 장비를 이용하여 후 열처리하였다. PZT의 결정화 과정과 DLC의 기계적 성질의 변화를 다양한 온도조건에 따라 분석한 결과 DLC는 PZT의 결정화 온도까지 영률과 강도면에서 우수한 특성을 나타냄을 확인하였다. 또한 포토레지스트를 사용함으로서 공정을 단순화하고 낮은 비용으로 제작이 가능하였다.

• 한국광학회지
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• 제14권4호
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• pp.466-472
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• 2003

본 논문에서는 서로 다른 길이의 광섬유 지연선로를 광 2${\times}$2 MEMS 스위치로 선택하여 위상 배열 안테나의 각 안테나 소자에 급전되는 RF 신호의 위상을 고속으로 제어할 수 있는 광 실시간 지연선로의 구조를 제안하였다. RF 신호의 주사 방향이 8개인 10 GHz 선형 위상 배열 안테나용 광 실시간 지연선로를 구현하였으며, 실험 결과 최대 시간 지연 오차가 0.2 ps이하, 즉 최대 주사 각 오차 0.84$^{\circ}$로 측정되었다. 또한 제안된 실시간 지연선로에 의해 구동되는 8개의 마이크로 스트립 패치 안테나 소자로 구성된 10 GHz용 선형 위상배열 안테나를 설계하였고, 시뮬레이션을 이용하여 이 안테나의 방사 패턴을 분석하였다.

• 한국소음진동공학회논문집
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• 제21권6호
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• pp.553-561
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• 2011

A theoretical approach is carried out to predict the quality factors of flexible modes of a microcantilever on a squeeze-film. The frequency response function of an inertially-excited microcantilever beam is derived using an Euler-Bernoulli beam theory. The external force due to squeeze-film phenomenon is developed from the Reynolds equation. Slip boundary conditions are employed at the interfaces between the fluid and the structure to consider the gas rarefaction effect, and pressure boundary condition at both ends of fluid analysis region is enhanced to increase the exactness of predicted quality factors. To the end, an approximate equation is derived for the first bending mode of the microcantilever. Using the approximate equation, the quality factors of the second and third bending modes are calculated and compared with experimental results of previously reported work. The comparison shows the feasibility of the current approach.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2395-2397
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• 2005

A low voltage operated piezoelectric RF MEMS in-line switch has been realized by using silicon bulk micromachining technologies for advanced mobile/wireless applications. The developed RF MEMS in-line switches were comprised of four piezoelectric cantilever actuators with an Au contact metal electrode and a suspended Au signal transmission line above the silicon substrate. The measured operation dc bias voltages were ranged from 2.5 to 4 volts by varying the thickness and the length of the piezoelectric cantilever actuators, which are well agreed with the simulation results. The measured isolation and insertion loss of the switch with series configuration were -43dB and -0.21dB (including parasitic effects of the silicon substrate) at a frequency of 2GHz and an actuation voltage of 3 volts.