Jeffrey Bo Woon Soon

Piezoelectric ALN MEMS resonators with high coupling coefficient

Piezoelectric AlN resonators with novel checker-patterned electrode architecture are reported in this paper. An array of interdigitated electrodes is used to excite two-dimensional plate acoustic waves within a thin piezoelectric layer. The resonant frequency can be changed by adjusting the size of the electrode fingers and hence resonators with multiple frequencies can be fabricated on a single wafer. A high coupling coefficient of 3.95% has been measured for one of the checker-mode resonators. A comparison of measured S21 plots of a checker-mode resonator and a contour-mode resonator with similar resonant frequency shows that checker mode is highly specific over a large frequency range.

Vertical silicon nano-pillar for non-volatile memory

NanoElectroMechanical (NEM) switches have been proposed for non-volatile memory applications, but low device density remains a key challenge for horizontal switches. This paper presents a resistive, vertically oriented NanoElectroMechanical (NEM) nano-pillar cantilever switch made of mono-crystaline silicon, with a cell size of 8F2. Using a top-down CMOS-compatible process requiring two lithography masks, nano-pillar switches with a height of 500nm, tip thickness of 35nm, and 25nm air gap are fabricated.

Evaluation of Piezoelectric Properties of AlN Using MEMS Resonators

This paper presents an effective evaluation of piezoelectric coefficients (d31 and d33) and other mechanical properties of AlN thin films using resonator structures fabricated on a single wafer. The extracted value for d31 is 1.60pm/V and the d33 value is 3.15pm/V, which are comparable to the coefficient values published in literature. Fabrication of these resonator structures is straightforward and can be incorporated with other more complex steps. Hence, these resonators can serve as an excellent test structures to evaluate and predict the quality of AlN growth and piezoelectric properties of thin AlN films.

FBAR Resonators with Sufficient High Q for RF Filter Implementation

Film Bulk Acoustic Wave Resonators (FBAR) at 2.6GHz using AlN piezoelectric material have been fabricated and characterized in this work. A stack of Al bottom electrode, AlN layer and top Al electrode is used to excite the thickness extensional (TE) vibration mode. The FBAR resonator has a quality factor of about 400 and the piezoelectric coupling coefficient of 4.25%, which is critical for RF filter implementation. Moreover, FBAR resonator has been designed to suppress spurious modes in order to ensure higher quality factor. Different filter topologies of ladder/lattice architecture are then explored for effective implementation using several FBAR resonators to build band-pass RF filters.

Non-contact fluorescent bleaching-independent method for temperature measurement in microfluidic systems based on DNA melting curves

This report introduces a bleaching-independent temperature measurement method based on the analysis of the fluorescence emitted during the melting of DNA molecules with the SYBR-Green I intercalator, in a microvolume where the strong non-linearity of the signal is used to eliminate the photobleaching effect as well as to determine the heat transfer rate between a heater and the sample and the temperature non-uniformity within the sample.

RF-Designed High-Power Lamb-Wave Aluminum–Nitride Resonators

We report Lamb acoustic wave resonators that are suitable for RF applications and that exhibit high power handling at high frequencies above 1 GHz. Resonators use aluminum-nitride as acoustic layer and are fabricated in the Institute of Microelectronics (IME) Agency for Science, Technology and Research (A*STAR)s in-house RF microelectromechanical system silicon-on-insulator platform. We focus the study on devices operating at their first symmetric Lamb-wave mode (S0) at 900 MHz and 1.5 GHz, although demonstrate 400 MHz and 1.2 GHz as well. All devices are realized in the same multi-frequency platform. Assessment of devices covers gain compression point (P1dB), third-order intermodulation intercept point (IIP3), thermal management, impedance matching, and quality factor. Devices exhibit P1dB above +30 dBm, and IIP3 higher than +50 dBm with low insertion losses less than 3 dB and 50- Ω impedance matching.

Integration of RF MEMS resonators and phononic crystals for high frequency applications with frequency-selective heat management and efficient power handling

We report a radio frequency micro electromechanical system (RFMEMS) device integrated with phononic crystals (PnC) that provide a Lamb-wave resonator with frequency-selective heat management, power handling capability, and more efficient electromechanical coupling at ultra high frequency (UHF) and low microwave bands. The integrated device is fabricated in a silicon-on-insulator (SOI) aluminum nitride (AlN) platform and boosts thermal performance by 40%, power handling by 3 dB, and coupling coefficient by three times. Design approach is scalable to higher frequencies.

Detachment Dynamics of Cancer Cells

Cell adhesion and detachment are crucial components in cancer spreading, often leading to recurrence and patient death [1]. Probing the mechanical behavior at the whole cell level while the cell is undergoing spreading and detachment during would enhance our understanding on cancer metastasis. However, these processes are not well understood in a quantitative sense, especially for the cancer cells [2]. In this article, we propose a biohybrid micro-device for the investigation of cellular attachment and detachment dynamics. This device comprises of silicon nanowires as electromechanical strain sensors, embedded in a suspended doubly-clamped silicon dioxide (SiO2) microbridge (Fig. 1A & Fig. 2A) for breast cancer (MCF-7) cells seeding and attachment (Fig. 1B).

Analysis of spurious modes, Q, and electromechanical coupling for 1.22 GHz AlN MEMS contour-mode resonators fabricated in an 8″ silicon fab

A systematical study is performed to analyze the spurious modes, Q and electromechanical coupling of 1.22 GHz AlN MEMS contour-mode resonators. A total of 135 different geometrical configurations were studied. An unloaded Q of up to 3157, an electromechanical coupling of up to 2.3%, and a figure of merit of up to 61.6 were achieved. In particular, we found that Q is primarily affected by finger length and anchor type. Also, overhang extension and finger numbers are the only parameters that change the relative location of main mode and spurs. Ultimately, by optimizing these two parameters it is possible to attain a high figure of merit while pushing the spurious modes away from the main mode of resonance.

AlN Actuator for Tunable RFMEMS Capacitor

This paper presents a novel piezoelectric actuator design that achieves low curling due to residual film stress. The proposed actuator maintains the gap between the movable electrode and the fixed electrode nearly constant independent of the residual stress level, improving the reproducibility and reliability of piezoelectric devices. At 20V excitation, the actuator deflects more than 5 µm. The design also achieves a capacitor electrode around 6% of the total actuator area, which is 2.5 times greater than other reported designs. This paper demonstrates the novel actuator in a tunable capacitor, but the actuator may be used in many other applications, such as MEMS switches and micro-mirrors.