Bo Woon Soon

National University of Singapore, Tumasik, Singapore

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Publications (15)31.31 Total impact

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    ABSTRACT: We experimentally demonstrated a free-standing two-dimensional (2-D) photonic crystal (PhC) aluminum nitride (AlN) membrane to function as a free space (or out-of-plane) reflector working in the mid infrared region. By etching circular holes of radius 620nm in a 330nm thick AlN slab, greater than 90% reflection was measured from 3.08μm to 3.78μm, with the peak reflection of 96% at 3.16μm. Due to the relatively low refractive index of AlN, we also investigated the importance of employing methods such as sacrificial layer release to enhance the performance of the PhC. In addition, characterization of the AlN based PhC was also done up to 450°C to examine the impact of thermo-optic effect on the performance. Despite the high temperature operation, the redshift in the peak reflection wavelengths of the device was estimated to be only 14.1nm. This equates to a relatively low thermo-optic coefficient 2.22 × 10−5 K−1 for AlN. Such insensitivity to thermo-optic effect makes AlN based 2-D PhC a promising technology to be used as photonic components for high temperature applications such as Fabry-Perot interferometer used for gas sensing in down-hole oil drilling and ruggedized electronics.
    Optics Express 04/2015; 23(8). DOI:10.1364/OE.23.010598 · 3.53 Impact Factor
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    ABSTRACT: This paper investigates the dependence of the quality factor (Q) of AlN contour mode resonators (CMRs) on the characteristics of the inactive regions located between the main resonator body (active region) and the stress-free surfaces placed beside the anchors. This paper shows that it is possible to reduce the energy leakage through the anchors by optimally sizing the width of such regions. To validate this concept, we built 16 different configurations of 225-MHz AlN CMRs, differing just by the size of the resonator inactive regions. [2015-0006]
    Journal of Microelectromechanical Systems 01/2015; DOI:10.1109/JMEMS.2015.2423663 · 1.92 Impact Factor
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    ABSTRACT: A vacuum-encapsulated silicon switch with a curved electrode is characterized for operation in harsh environments. An ultraclean vacuum encapsulation process (episeal) seals the switch after release, providing a pristine operating environment for switching operations. In these devices, the curved beam of the actuator enhances the overdrive voltage tolerance to be more than 100 V. The ON/OFF cycle tests were carried out up to $10^{5}$ cycles at room temperature, and at least $10^{4}$ cycles under an elevated temperature of 300 $^{circ}{rm C}$ . Throughout the 300 $^{circ}{rm C}$ tests, an average contact resistance of ${sim}{rm 28}~{rm k}Omega$ is measured, demonstrating the stability of the contact. Finally, high speed pulse $I{-}V$ monitoring unit was used to observe 13- $mu{rm s}$ switching speed.
    Journal of Microelectromechanical Systems 10/2014; 23(5):1121-1130. DOI:10.1109/JMEMS.2014.2305754 · 1.92 Impact Factor
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    ABSTRACT: This work demonstrates a cantilever based electrostatic microelectromechanical system device operating as a memory element. Volatile and non-volatile functions are engineered by manipulating molecular adhesion force through contact dimples and restoring force using the cantilever design. For non-volatile RESET operation, a method of detaching the cantilever with 3 V pulsating DC signal at 1 MHz is proposed. SET/RESET cycles are performed up to 103 times at 300 °C without any performance degradation. A writing speed of up to 0.94 μs is achieved, which is faster than conventional high temperature flash memories. With demonstrated attributes, the fabricated device offers excellent potential for harsh environment data storage applications.
    Applied Physics Letters 09/2014; 105(11):113503. DOI:10.1063/1.4895578 · 3.52 Impact Factor
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    ABSTRACT: An all metal based electrostatic nanoelectromechanical switch has been fabricated using a one mask process. High temperature cycling behavior is demonstrated in a vacuum chamber at 300 °C for more than 28 hours. The compelling results indicate that the design is promising for the realization of rugged electronics with three-dimensional integration.
    Nanoscale 04/2014; 6(11). DOI:10.1039/c3nr05255a · 6.74 Impact Factor
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    ABSTRACT: By using complementary-metal-oxide-semiconductor processes, a silicon based bi-stable nanoelectromechanical non-volatile memory is fabricated and characterized. The main feature of this device is an 80 nm wide and 3 μm high silicon nanofin (SiNF) of a high aspect ratio (1:35). The switching mechanism is realized by electrostatic actuation between two lateral electrodes, i.e., terminals. Bi-stable hysteresis behavior is demonstrated when the SiNF maintains its contact to one of the two terminals by leveraging on van der Waals force even after voltage bias is turned off. The compelling results indicate that this design is promising for realization of high density non-volatile memory application due to its nano-scale footprint and zero on-hold power consumption.
    Applied Physics Letters 08/2013; 103(5). DOI:10.1063/1.4817796 · 3.52 Impact Factor
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    ABSTRACT: We present a silicon nanofin (Si-NF) that can be actuated bidirectionally by electrostatic force between two contact surfaces. The switch is able to maintain its contact leveraging on van der Waals force, which holds the Si-NF to either terminal without an on-hold bias, thus exhibiting bistable hysteresis behavior. The measured pull-in voltage (VPI) and reset voltage (VRESET) are 10 and -12 V, respectively, confirming that the switch can be reset by the opposite electrode. Since the switch toggles between two stable states, it can be an ideal device for nonvolatile memory (NVM) applications.
    IEEE Nanotechnology Magazine 06/2013; 7(2):24-28. DOI:10.1109/MNANO.2013.2260461
  • Bo Woon Soon, N. Singh, J.M. Tsai, Chengkuo Lee
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    ABSTRACT: We present a silicon nanofin (Si-NF) which can be actuated bi-directionally by electrostatic force between two contact surfaces. The switch is able to maintain its contact leveraging on van der Waals force that holds the Si-NF to either terminal without on-hold bias, thus showing a bi-stable hysteresis behavior. The measured pull-in voltage VPI and VRESET is 10V and -12V respectively, confirming that the switch can be reset by the opposite electrode. Since the switch toggles between two stable states, therefore it can be an ideal device for non-volatile memory (NVM) application.
    Nano/Micro Engineered and Molecular Systems (NEMS), 2013 8th IEEE International Conference on; 01/2013
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    ABSTRACT: A novel electromagnetic energy harvester (EH) with multiple vibration modes has been developed and characterized using three-dimensional (3D) excitation at different frequencies. The device consists of a movable circular-mass patterned with three sets of double-layer aluminum (Al) coils, a circular-ring system incorporating a magnet and a supporting beam. The 3D dynamic behavior and performance analysis of the device shows that the first vibration mode of 1285 Hz is an out-of-plane motion, while the second and third modes of 1470 and 1550 Hz, respectively, are in-plane at angles of 60° (240°) and 150° (330°) to the horizontal (x-) axis. For an excitation acceleration of 1 g, the maximum power density achieved are 0.444, 0.242 and 0.125 µW cm−3 at vibration modes of I, II and III, respectively. The experimental results are in good agreement with the simulation and indicate a good potential in the development of a 3D EH device.
    Journal of Micromechanics and Microengineering 11/2012; 22(12):125020. DOI:10.1088/0960-1317/22/12/125020 · 1.73 Impact Factor
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    ABSTRACT: Aluminium-coated micromirrors driven by electrothermal and electromagnetic actuations have been demonstrated for 3-D variable optical attenuation applications. Three types of attenuation schemes based on electrothermal, electromagnetic and hybrid, i.e. combination of electrothermal and electromagnetic, actuations have been developed. In addition, two different designs have been fabricated and characterized to investigate the effects of the variations made to both the actuators on the optical attenuation performances of the micromirror. Our unique design of using both ET and EM actuators simultaneously to achieve attenuation is the first demonstration of such hybrid driven CMOS compatible MEMS VOA device.
    Optics Express 09/2012; 20(19):21598-611. DOI:10.1364/OE.20.021598 · 3.53 Impact Factor
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    ABSTRACT: Phononic crystal (PnC) resonators of Bloch-mode resonance made by replacing periodically arranged two or three rows of air holes with one row of air holes on a two-dimensional (2-D) silicon slab with air holes of square lattice have been investigated. Piezoelectric aluminum nitride (AlN) film is employed as the interdigital transducers to transmit and detect acoustic waves, thus making the whole microfabrication process CMOS compatible. We also fabricate a PnC structure which has a stopband of 140 MHz <; f <; 195 MHz which agrees well with the simulation results. From our experimental results, we found that the two kinds of microfabricated PnC resonators have different optimization conditions in terms of resonant frequency and Q factor, as well as insertion loss, despite their similar design approach. As compared to PnC resonators of hexagonal lattice, the proposed Bloch-mode PnC resonators of square lattice demonstrated higher resonant frequency, higher Q factor, and a smaller device area. The promising acoustic characteristics may be further optimized for applications such as microfluidics, biomedical devices, and radio-frequency communications in the gigahertz range.
    Journal of Microelectromechanical Systems 08/2012; 21(4):801-810. DOI:10.1109/JMEMS.2011.2174416 · 1.92 Impact Factor
  • B.W. Soon, N. Singh, J.M. Tsai, C. Lee
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    ABSTRACT: In this paper, we demonstrate wafer level encapsulation of MEMS using physical vapor deposition of aluminum (Al). A cavity area, which simulates the area of a MEMS device, is fully encapsulated by dual layer of amorphous silicon and Al. The encapsulation process takes place in the PVD chamber, thus the vacuum level in the sealed cavity is assumed to be high. The proposed processes are entirely CMOS compatible and readily deployed into any standard CMOS foundry and semiconductor wafer fabrication.
    Electronics Packaging Technology Conference (EPTC), 2012 IEEE 14th; 01/2012
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    ABSTRACT: A 2-D silicon phononic crystal (PnC) slab of a square array of cylindrical air holes in a 10-μm-thick freestanding silicon plate with line defects is characterized as a cavity-mode PnC resonator. A piezoelectric aluminum nitride (AlN) film is employed as the interdigital transducers to transmit and detect acoustic waves, thus making the whole microfabrication process CMOS compatible. Both the band structure of the PnC and the transmission spectrum of the proposed PnC resonator are analyzed and optimized using finite-element method. The measured quality factor ( Q factor) of the microfabricated PnC resonator is over 1000 at its resonant frequency of 152.46 MHz. The proposed PnC resonator shows promising acoustic resonance characteristics for radio-frequency communications and sensing applications.
    IEEE Electron Device Letters 07/2011; DOI:10.1109/LED.2011.2136311 · 3.02 Impact Factor
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    ABSTRACT: This paper shows the design, fabrication and characterization of a novel design micromechanical resonators with Bloch-mode resonance by creating defects on a two- dimensional (2-D) silicon phononic crystal (PnC) slab made by etching a square array of cylindrical air holes in a 10μm thick free-standing silicon plate. Piezoelectric aluminum nitride (AlN) film is deployed as the inter-digital transducers (IDT) to transmit and detect acoustic waves, thus making the whole microfabrication process CMOS-compatible. We also fabricate a PnC structure which has a stopband of 140MHz < f
    01/2011; DOI:10.1109/DSR.2011.6026876
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    ABSTRACT: A membrane pressure sensor with embedded piezoresistive silicon nanowires (NW) has been demonstrated to have an ultrasensitive piezoresistive response of (ΔR/R)/ΔP of 13 Pa−1. This was achieved through the effective tuning of the transverse electric field across the NW. The fabrication of the sensor is fully based on CMOS compatible technique. P-type 〈110〉 oriented NWs with a square cross-section of 100 nm were fabricated on silicon-on-insulator (SOI) wafers, acting as the sensing elements. The NWs’ exceptional properties and minute size will enable further shrinking of footprint of pressure sensors and other NEMS sensors with increased sensitivity, opening a way to new applications like implantable medical devices.
    Procedia Engineering 12/2010; 5:1127-1130. DOI:10.1016/j.proeng.2010.09.309