A Fast-Switching (1.35-μs) Low-Control-Voltage (2.5-V) MEMS T/R Switch Monolithically Integrated With a Capacitive Micromachined Ultrasonic Transducer (CMUT).
A Fast-Switching (1.35-μs) Low-Control-Voltage (2.5-V) MEMS T/R Switch Monolithically Integrated With a Capacitive Micromachined Ultrasonic Transducer (CMUT).
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一种与电容式微机械超声波换能器 (CMUT) 单片集成的快速开关 (1.35μs) 低控制电压 (2.5V) MEMS T/R 开关。
DOI：
10.1109/jmems.2017.2781255
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Oralkan,Ömer
中科院分区：
文献类型：
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作者：
Zhang,Xiao;Adelegan,OluwafemiJoel;Yamaner,FeyselYalçın;Oralkan,Ömer
本文介绍了一种静电微机电系统（MEMS）开关的设计和制造，该开关可以与电容式微机械超声换能器（CMUT）作为发射/接收开关在同一衬底上共同制造。开关的结构由单个CMUT单元修改而来。在电池的中心设置一条中断传输线，两侧有控制电极，以拉下可移动板。所述板下有绝缘层，在绝缘层上形成金属凸点，并与传输线间隙对齐，用静电力拉下所述板，使金属凸点闭合传输线间隙即可接通开关。该开关采用有限元模型设计，并采用阳极键合技术在玻璃基板上制造。首先对开关测试结构进行了静态表征，结果表明直流开关电压为68 V，导通电阻为50 Ω。在医学超声成像常用的频率范围内，rfin -to- rout隔离测量值约为66 dB，插入损耗约为4.85 dB。然后，我们进行了浸入式动态表征。通过将直流偏置设置为67 V，我们发现开关可以在低至2.5 V的控制电压下工作。开关时间和释放时间分别与控制信号的上升时间和下降时间有关。最小开关时间为1.34 μs，控制信号上升时间为300 ns；最小释放时间为80 ns，控制信号下降时间为20 ns。我们进一步证明，具有优化的上升和下降时间的1 khz控制信号可用于传导和阻断频率为1 mhz、幅度为300 mvpp的正弦信号，以及幅度为5 vpp、脉宽为500 ns、重复率为2 khz的单极脉冲。所提出的MEMS开关可以潜在地消除基于cmut的超声成像系统对片上前端电子器件的高压工艺要求，从而提高整体系统效率。
This paper describes the design and fabrication of an electrostatic microelectromechanical systems (MEMS) switch that can be co-fabricated on the same substrate with a capacitive micromachined ultrasonic transducer (CMUT) as a transmit/receive switch. The structure of the switch is modified from a single CMUT cell. An interrupted transmission line is defined across the center of the cell with control electrodes on both sides to pull a movable plate down. The plate has an insulation layer underneath, and a metal bump is formed on the insulation layer and aligned to the transmission line gap, so that the switch could be turned ON by pulling down the plate with electrostatic force and making the metal bump close the gap in the transmission line. The switch was designed using a finite-element model and fabricated on a glass substrate using anodic bonding. A static characterization was first performed on a switch test structure, which showed that the dc switching voltage was 68 V and the ON-resistance was 50 Ω. The RFin-to-RFout isolation was measured as approximately 66 dB and insertion loss was approximately 4.85 dB for the frequency range commonly used for medical ultrasound imaging. Then, we performed the dynamic characterization in immersion. By setting the dc bias at 67 V, we found that the switch could be operated with a control-voltage as low as 2.5 V. The switching and release times are related to the rise time and fall time of the control signal, respectively. The minimum switching time was measured as 1.34 μs with a control signal rise time of 300 ns, and the minimum release time was measured as 80 ns with a control signal fall time of 20 ns. We further demonstrated that a 1-kHz control signal with the optimized rise and fall times can be used to conduct and block a sinusoidal signal with 1-MHz frequency and 300-mVpp amplitude, as well as unipolar pulses with 5-Vpp amplitude, 500-ns pulse width, and 2-kHz repetition rate. The presented MEMS switch could potentially eliminate the high-voltage process requirement for the on-chip front-end electronics of a CMUT-based ultrasound imaging system and thus improve the overall system efficiency.