Maher Bakri-Kassem

Two movable-plate nitride-loaded MEMS variable capacitor

A MEMS variable capacitor having two movable plates loaded with a Nitride layer is proposed. A trench in the silicon substrate underneath the capacitor is used to decrease the parasitic capacitance. The use of an insulation dielectric layer on the bottom plate of the MEMS capacitor increases the capacitors tuning range and eliminates stiction. The tuning range was measured and found to be 280% at 1 GHz. The achievable tuning range far exceeds that of the traditional parallel plate MEMS variable capacitors. The proposed MEMS variable capacitor is built using the MetalMUMPs process.

Novel High-

Two microelectromechanical systems (MEMS) curled-plate variable capacitors, built in 0.35-mum CMOS technology, are presented. The plates of the presented capacitors are intentionally curled upward to control the tuning performance. A newly developed maskless post-processing technique that is appropriate for MEMS/CMOS circuits is also presented. This technique consists of dry-and wet-etching steps and is developed to implement the proposed MEMS variable capacitors in CMOS technology. The capacitors are simulated mechanically by using the finite-element method in ANSYS, and the results are compared with the measured results. Two novel structures are presented. The first capacitor is a tri-state structure that exhibits a measured tuning range of 460% at 1 GHz with a flat capacitance response that is superior to that of conventional digital capacitors. The proposed capacitor is simulated in Ansofts high frequency structure simulator (HFSS) and the capacitance extracted is compared with the measured capacitance over a frequency range of 1-5 GHz. The second capacitor is an analog continuous structure that demonstrates a measured continuous tuning range of 115% at 1 GHz with no pull-in. The measured quality factor is better than 300 at 1.5 GHz. The proposed curled-plate capacitors have a small area and can be realized to build a system-on-chip.

Q

This paper addresses the use of RF MEMS devices in wireless and satellite communication systems. Novel configurations are presented for MEMS variable capacitors, MEMS tunable inductors and RF MEMS multiport switches. The tuning range of the variable capacitor was measured and found to be 280%, which far exceeds that of the traditional parallel plate MEMS variable capacitors. The MEMS tunable inductor is realized using MEMS fixed inductors, capacitors and a variable MEMS capacitor. The proposed MEMS multiport switch has demonstrated a superior RF performance up to 20 GHz.

MEMS Curled-Plate Variable Capacitors Fabricated in 0.35-

This paper presents an integrated tunable bandpass filter with RF MEMS varactors fabricated using the TSMC 0.35 μm CMOS process. A maskless post-processing technique is developed which enables the fabrication of RF MEMS parallel-plate capacitors with a high quality factor and a very compact size. A 2-pole coupled line tunable bandpass filter with a center frequency of 9.5 GHz and a 9% relative bandwidth is designed, fabricated and tested. A tuning range of 17% is achieved using integrated variable MEMS capacitors with a quality factor exceeding 20. The filter has an insertion loss of 5.66 dB and occupies a chip area of 1.2 × 2.1 mm2.

\mu{\hbox {m}}

A microelectromechanical systems (MEMS) variable capacitor having additional carrier beams is proposed. The use of carrier beams makes it possible to obtain an equivalent nonlinear spring constant, which increases the capacitor’s tuning range and prevents the top plate from collapsing at a tuning range of 50%. A lumped element model and a continuous model of the proposed variable capacitor are developed. The continuous model is simulated using commercial software. A detailed analysis for the steady state of the capacitor is presented. The tuning range is measured and found to be 410% at 1GHz with a maximum dc bias voltage of 9.2V. The achievable tuning range exceeds that of the traditional parallel-plate MEMS variable capacitors. The self-resonance frequency is measured and found to exceed 11GHz. The proposed MEMS variable capacitor is built using the PolyMUMPs process.

CMOS Technology

A novel MEMS variable capacitor, built with arrays of supporting beams, is proposed. The supporting beams create different restoring forces, as the top plate deflects, increasing the tuning range of the capacitor. The tuning range was measured and found to be 470% at 1 GHz with a maximum DC bias voltage of 10.2 volt. The achievable tuning range exceeds that of any known parallel plate MEMS variable capacitor. The proposed capacitor promises to achieve a higher tuning range by optimizing the supporting beams array configuration. The experimental MEMS variable capacitors are built using the PolyMUMPs process.

RF MEMS devices

Latching RF MEMS Switches of Single-Pole-Single-Throw (SPST), Single-Pole-Double-Throw (SPDT) and Single-Pole-Triple-Throw (SP3T) types are proposed. The switches are built of a 20 μm thick nickel layer covered with a plated 2 μm gold on the top and side walls of nickel layer eliminating any potential warping due to thermal mismatch. The switches are actuated using a high stroke latching thermal actuator that exhibits a 32 μm displacement with a dc power of 250 mW under ambient pressure at 25 ^° C (298 ^° K) and 153 mW under vacuum at -193^° C (80 ^° K). The measured velocity for the actuator is 2.3 μm/msec. The RF measurement of the SPST switch is done under ambient and vacuum and over a wide range of temperatures from 25 ^° C (298 ^° K) to -193^° C (80 ^° K). The switches survived a temperature cyclic test from 25 ^° C (298 ^° K) to 85 ^° C (358 ^° K) with a total variation of 0.2 dB in insertion loss. The switch demonstrates a worst IP3 of 60.14 dBm and high power handling capabilities that exceeds 30 Watt, only tested for an hour in 1 cycle. The RF performance of the SPST, SPDT and SP3T exhibits a worst insertion loss of 0.8 dB, 1.2 dB and 1.5 dB up to 40 GHz, 40 GHz and 18 GHz, respectively.

An Integrated Tunable Band-Pass Filter Using MEMS Parallel-Plate Variable Capacitors Implemented with 0.35μm CMOS Technology

A curl-up-plate microelectromechanical system (MEMS) varactor with an almost linear response and high tuning capacitance ratio is presented. The curl-up in the top plate is realized by the residual stress in the two layers that construct the top plate of the varactor. The linear response is achieved by having the curl-up plate designed to relax on the bottom plate and by having unanchored cantilever beams that prevent the pull-in, while applying a dc bias voltage. The developed varactor exhibits a low parasitic capacitance through etching the lossy substrate underneath the varactors plates. A thin alumina dielectric layer of 100-nm thickness is deposited using an atomic-layer-deposition technique to provide electrical isolation between the two plates. This MEMS varactor exhibits an almost linear capacitance with a tuning ratio of 5 : 1.

A high-tuning-range MEMS variable capacitor using carrier beams

A MEMS variable capacitor having additional carrier beams is proposed. The use of the carrier beams increases the capacitors tuning range and prevents the top plate from collapsing at a tuning range of 50%. The tuning range was measured and found to be 410% at 1 GHz with a maximum DC bias voltage of 9.2 volt. The achievable tuning range exceeds that of the traditional parallel plate MEMS variable capacitors. The proposed MEMS variable capacitor is built using the PolyMUMPs process.

High Tuning Range Parallel Plate MEMS Variable Capacitors with Arrays of Supporting Beams

A MEMS variable capacitor having two movable plates loaded with a Nitride layer is proposed. A trench in the silicon substrate underneath the capacitor is used to decrease the parasitic capacitance. The use of an insulation dielectric layer on the bottom plate of the MEMS capacitor increases the capacitors tuning range and eliminates stiction. The tuning range was measured and found to be 280% at 1 GHz. The achievable tuning range far exceeds that of the traditional parallel plate MEMS variable capacitors. The proposed MEMS variable capacitor is built using the MetalMUMPs process.