Etsuji Ogawa

An RF MEMS Variable Capacitor with Intelligent Bipolar Actuation

We propose an IBA scheme based on a pull-out detection, which is suitable for implementing in a circuit. The scheme is implemented in a driver IC that is part of a module with an RF MEMS variable capacitor. No failures are observed over 108 cycles at 85degC, which is an accelerated charging condition.

A high power-handling RF MEMS tunable capacitor using quadruple series capacitor structure

This paper presents an RF MEMS tunable capacitor that achieves an excellent power-handling property with relatively low actuation voltage. The tunable capacitor consists of two fixed MIM (Metal-Insulator-Metal) capacitors and two MEMS capacitor elements, all connected in series. This quadruple series capacitor (QSC) structure enables reduction of the actuation voltage without sacrificing the power-handling capability, since the MIM capacitor reduces the RF voltage amplitude applied to the MEMS capacitors. The measured result demonstrates +36dBm hot-switching at 85°C with 21V pull-in voltage.

A Robust RF MEMS Variable Capacitor with Piezoelectric and Electrostatic Actuation

An RF MEMS variable capacitor using hybrid actuation of piezoelectric and electrostatic forces is presented. A surface micromachining process is used to fabricate the device. The piezoelectric actuator, which uses thin film PZT, enables low voltage actuation while the electrostatic actuator realizes large capacitance ratio. The measured capacitance ratio is Cmax/Cmin=14 at 5V. We demonstrate that the hybrid actuation enables to lower the pull-in voltage without changing the pull-out voltage. We also show that the shift of pull-out voltage due to dielectric charging can be reduced drastically at actuation voltages below 10V. In this sense, the hybrid actuation can realize low voltage operation with enhanced robustness for stiction

Low profile double resonance frequency tunable antenna using RF MEMS variable capacitor for digital terrestrial broadcasting reception

It is difficult to realize the built-in antenna for wideband systems, because a frequency bandwidth of the low profile antenna is narrow. A frequency tunable antenna is a technique for wideband characteristics. In this paper a low profile double resonance frequency tunable antenna using MEMS variable capacitors is presented. It has high efficiency over a wide frequency band. Through both resonant portions from 465 to 665 MHz, the efficiency of more than −4 dB and the VSWR of less than 3 are observed in the measurement using the variable capacitor of 0.4–0.9 pF.

Highly reliable and manufacturable in-line wafer-level hermetic packages for RF MEMS variable capacitor

In this paper, we report a thin-film encapsulation technology for wafer-level micro-electro-mechanical systems (MEMS) variable capacitor package. The electrical characteristics of MEMS are adversely affected by moisture. In order to prevent moisture from permeating into a package, the top surface was protected with a plasma-enhanced chemical vapor deposition (PE-CVD) SiN layer. The developed packages become a hybrid thin-film hermetic encapsulation consisting of an internal shell using PE-CVD SiO, a seal layer coating with resin, and an external protective layer formed by PE-CVD SiN. The process is fully compatible with standard low-cost back-end-of-the-line (BEOL) technologies for LSIs as a wafer-level package (WLP). This hybrid structure was very effective for protecting the MEMS device from external moisture. Moreover, the electrode surface area has to be wide, because a wide range of capacities is necessary in MEMS variable capacitors. We have developed a large (1480 × 1080 µm) hermetic thin-film encapsulation as WLP.

A CMOS embedded RF-MEMS tunable capacitor for multi-band/multi-mode smartphones

This paper reports on 1-chip RF-MEMS tunable capacitor that equips CMOS driver circuit in the underlying layer. A Wafer Level Chip Scale Package (WLCSP) optimized for RF-MEMS is employed to minimize the module size. The MEMS actuation voltage is generated by an Actuation Voltage Generator (AVG). The boost mechanism employed in the AVG enables instant high voltage generation and reduction of the dielectric charging. The measured noise at RF frequencies is less than -120dbm, thanks to a shield metal layer formed between MEMS and CMOS layers. To achieve high power handing and high creep immunity, we employ the previously reported techniques, the Quadruple Series Capacitor (QSC) [1] and the SiN springs [2]. The quality factor measured in the WLCSP is larger than 100 at 1GHz. The capacitance can be changed from 1.4pF to 5pF by a step of 0.45pF.

A Catch-and-Release drive MEMS gyroscope with enhanced sensitivity by mode-matching

This paper presents a novel MEMS gyroscope that employs intermittent free vibration and mode matching. An intermittent operation is realized by a “Catch-and-Release (CR)” technique, which enables significant reduction of the drive power. Sensitivities of the mode-matching and mode-split conditions are investigated by electrostatically tuning the sense-mode frequency. A sensitivity as high as 2.14 mV/dps, 52 times higher than the mode-split case, is obtained when the drive and sense frequency difference Δƒ is reduced to 50 Hz. Optimization for mode matching and quadrature nulling is also demonstrated.

A 3V Operation RF MEMS Variable Capacitor using Piezoelectric and Electrostatic Actuation with Lithographical Bending Control

A 3 V operation RF MEMS variable capacitor using hybrid actuation of piezoelectric and electrostatic forces is presented. Bending of the piezoelectric actuator is controlled by a lithographical pattern formed on top of the actuator. The hybrid actuation and the optimized bending enabled 2.6 V pull- in voltage with the pull-out voltage as high as 2.0 V The measured capacitance ratio is 14.