Scalable Contact-Capacitive MEMS Switches With High Capacitance Ratio for Millimeter-Wave Applications

The regular down scaling in integrated circuits technologies stimulates the development of new solutions to increase the integrated circuit performances. Most efforts on size shrinking have been focused on active devices. Among technical solutions, the design and manufacturing of highly reliable integrated passive devices could be particularly relevant. Indeed, dielectrics thin films are used in a wide range of capacitive devices such as Metal Insulator Metal (MIM) capacitors, Metal Oxide Semiconductor (MOS) capacitor, gate for transistors and Memory applications or Radio Frequency Micro Electro MechanicalSystems(RFMEMS)switchingcapacitors.Theelectrical

Radio frequency micro electromechanical system (RF MEMS) based switches are widely used in microwave and millimeter wave communication systems for their low loss, excellent linearity, low power consumption and compact size compared to other contemporary solid state devices [1]. Surface micromachining technology is typically used to develop different types of single pole multi-throw (SPMT) switches like SPST, SPDT and SP4T. MEMS series and shunt switches are extensively used in SPMT RF switches for multiband selectors, filter banks, reconfigurable antennas and phase shifter applications in transmit/receive modules.

Epoxy based photo polymer - SU8 is evaluated as microwave packaging material for packaging of Radio Frequency Micro Electro Mechanical Systems (RFMEMS). Standard and Slotted Coplanar Waveguide transmission lines are chosen as test vehicles. Transmission lines of lengths up to 10mm are formed on ST-Cut Quartz substrates. The fabricated transmission lines are subjected to wafer level packaging. The measured S-parameter data shows a significant difference prior to and after packaging. Further, the effects due to the packaging are modeled using lumped components and the measured data are validated with simulations in Advanced Design System. The measured and simulated data agree favorably with each other, for both before and after packaging.

Radio Frequency Micro Electro Mechanical Systems (RF MEMS) are devices showing exceptional potential to satisfy the demands of emerging RF electronic technologies, including those considered for high-power applications, such as for long distance communication systems. Operation in this regime requires an alternative way of thinking for these devices and, for example, a more accurate control of the pull-in voltage is of major importance due to the self-actuation effect. Therefore, the studies focusing on the features of the moving bridges are of great importance. This work presents the fabrication of a full family of RF MEMS switches suitable for high-power implementations having bridges deposited by Au electroplating and released using purely standard wet processes, as well as a carefully designed experimental study of their pull-in voltage. Depositing the bridge of the high-power RF MEMS by using only a single electroplating step makes the device fabrication easier, whilst the utilization of a purely wet release process is an asset. This method relies on low temperature processes, applicable simultaneously in bridges with various geometrical and perforation details without the need of any specialised infrastructure. The experimentally obtained results suggest that for this technology the bridge thickness is a critical factor for controlling the pull-in characteristics between devices fabricated in the same run. Moreover, it is revealed that for thicker bridges, geometry and hole perforation effects are more pronounced. This technology is therefore suitable for developing RF MEMS where the bridge thickness could be potentially utilized for enabling optimization engineering between devices that should be fabricated in the same run but need to satisfy diverse specifications during their operation.

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.

Hexagonal Shape radiating patch with reconfigurable characteristics for WiMAX/C/WLAN band is presented which is simulated on RT Duroid5880 substrate and is fed by CPW. Fractional bandwidth of antenna corresponds to 153.62% with high rejection dual band-notch reconfigurable characteristics excluding interfering bands WiMAX (3.30GHz–3.80GHz)/C-Band (3.80GHz–4.20GHz)/WLAN (IEEE802.11a/h/j/n5.15GHz–5.35GHz, 5.25GHz–5.35GHz, 5.47GHz–5.725GHz,5.725GHz–5.825GHz) using radio frequency micro electro mechanical systems (RF MEMS) shunt switch. The proposed antenna exhibits 3.4dBi–6.32dBi gain and 78–94% radiation efficiency. The group delay ≤1.0ns is also maintained in the entire operating band. Good dipole like radiation pattern in E-plane and omni-directional pattern in H-plane is also well maintained in the operating band with less co polarization with compact dimensions of 20 × 22 × 0.782 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

To determine a micro electro mechanical systems (MEMS) inductor configuration that gives large inductance variations and high Q-factors, air-suspended MEMS inductor configurations are studied: (a) an inductor with two angularly meandered lines, (b) a solenoid inductor with a pair of movable shields, (c) a planar spiral inductor with a patterned shield of different areas, and (d) a planar spiral inductor with a metallic frame of different sizes. The configuration of (a) is shown to give a large inductance variation of 115%. However, its Q-factor is only about 10, and difficulties in fabrication are also expected. The configuration of (b) could be a reasonable engineering solution. The inductance variation is 67%, and the maximum Q-factor is over 22. The solenoidal inductor configuration is thus considered suitable for realizing an RF MEMS variable inductor with large inductance variations and high Q-factors.

RF MEMS (radio frequency micro electro mechanical systems) technology holds great promise for wireless communication and sensor systems. Excellent MEMS switching devices have recently been developed, but because of packaging problems, no commercial integrated product exists. The objective of the ongoing work at CFD Research Corporation (CFDRC) and Morgan Research Corporation (MORGAN) is to develop novel packaging concepts, design tools, and demonstrated RF MEMS packaged devices for high frequency applications.

Design, fabrication and characterization of miniature RF MEMS switched capacitor based phase shifter

There exists a growing demand on high performance variable filters for multi-function, multi-band wireless systems used in wide variety of applications. A variable capacitor with high capacitance ratio (CR) is one of the key devices to realize such controllable/reconfigurable filters. This paper reports the device structure, fabrication process, and the performance of a very high CR variable capacitor using pure water as dielectric material. The device holds two reservoir cells and was fabricated by microelectromechanical systems (MEMS) technology. It exhibited three digitally-stepped capacitances; varied from 0.93 pF to 32.9 pF (CR=35), then to 74.4 pF (CR=80) at 1 MHz by filling each of the cells with pure water. In order to confirm the electrical behavior for such a fluid MEMS capacitor, its microwave performance was evaluated. An equivalent RF circuit model with 9 elements has been introduced and the device performance was successfully simulated up to 4 GHz. It is also confirmed that the 3 step capacitance values stay effective in the same frequency range.

A vertical RF-MEMS (Radio Frequency Micro ElectroMechanical Switch) switch design is proposed in this work that features a shunt capacitive configuration and can operate at a very low actuation voltage. Besides operating on a low switching voltage, the switch behold a small value of insertion loss in Up (ON) state and offers a towering isolation factor in Down (OFF) state. A horizontal structure of bridge membrane is used in the proposed design and the switch function (with ON and OFF operating states) is provided by the vertical movement of this membrane structure that is controlled by the electrostatic actuation technique. The actuation pad is centrally fed by a Coplanar Waveguide structure. The switch performance has been analysed over a wide frequency range from 1 to 40 GHz. For obtaining a 1.5 μm vertical displacement of the bridge membrane, a sheer 3.0 Volts of pull-in voltage (VPI) is required. CoventorWare and HFSSv13 tools are used in this work for designing and analysing the proposed switch. The use of fixed-fixed flexure beam configuration is chosen for switch design. Simulation results showcase excellent RF characteristics with isolation factor of −47 dB (at 32.5 GHz) and insertion loss in range of −0.01 to −1.10 dB (for 1−40 GHz frequency).

We propose a design, micro fabrication process, and nuclear magnetic resonance (NMR) based evaluation, of a magnetic field gradient chip. The uni-axial linear z-gradient coil design was computed by a stream-function method, with the optimisation goal to exhibit minimum power dissipation. The gradient coils were implemented on two bi-planes, which were built-up with Cu electroplating in combination with photo definable dry-film laminates. In the presented fabrication process, the initial seed layer served as a self-aligning back-side mask to define the electroplating mould, and also to implement resistive temperature detectors. The coil design and the electroplating process were tailored to enhance the electroplated height to construct low-resistive coils. Thermographic imaging in combination with the integrated temperature sensors allowed for investigating the heat-up, in order to analyse the current rating of the coil dual stack. The gradient coil was assembled with a radio frequency micro coil in a flip-chip configuration. To demonstrate the field linearity, a micro-engineered phantom was fabricated and subjected to a one-dimensional NMR experiment.

RF MEMS capacitive switch on semi-suspended CPW using low-loss high-resistivity silicon substrate

In this work, a portable biosensor that has 60% effective surface area on the chip with 1fg sensitivity by using novel array configuration is designed, and sent for fabrication. High frequency shift, quality factor, capacitance ratio, and small response time during the AC actuation are the critical parameters for the biosensor design. By using a beam structure in contrast to the more common cantilever, the effective surface area increases from 41% to 71%. Flexible microfluidic channels are integrated with the CMOS chip to deliver the biomaterial and are used for the packaging.

Modern reconfigurable communication systems demand microwave voltage-controlled oscillators (VCOs) possessing an octave-wide bandwidth. Many advanced applications require also a low phase noise and a low current consumption for such VCOs. To meet an octave-bandwidth specification in combination with a low phase noise and a low current consumption it is desirable to implement a microwave monolithic integrated circuit (MMIC) technology. In-house gallium arsenide (GaAs) MMIC technology is implemented to build VCOs in this work. At the same time, in order to achieve a high-Q wide frequency tuning range, we implemented also a discrete variable capacitance diode (varicap). The discrete varicap is stacked above MMIC oscillator chip. A vertical design structure of the discrete varicap guarantees a high overlap capacitance ratio (K&gt;20) along with reduced affect of the parasitic reactance. A high overlap capacitance ratio is needed for an octave-wide frequency tuning, while reduced affect of the parasitic reactance increases Q-factor of the VCO resonator. Hence, a sequential integration of the discrete varicap over monolithic oscillator chip resolves referred tough challenges in the design of VCO. Integrated VCO is finally packaged as a surface-mount device (SMD). At that SMD ceramic package is sealed with the metal lid. The oscillator circuitry is based on the conventional negative resistance approach with a positive feedback realized by common-source capacitance. An active element of the oscillator is a pseudomorphic high electron-mobility transistor (pHEMT). The gate length of a transistor is 0.15 µm. The width of the gate varies from 240 µm to 360 µm depending on working frequencies of the VCO. The varicap is built on the GaAs epitaxial heterostructure having customized gradient doping profile with abrupt junction. Nonlinear behavioral model of the varicap is extracted from the diode measurements and is further used for VCO simulation. Two types of VCO have been designed, fabricated and tested. First (second) type of VCO provides a tuning range from 5 to 10 GHz (from 10 GHz to 20 GHz), respectively. The measurement results demonstrate an output power of 3.9 dBm; a current consumption of 30 mA at a supply voltage of 5 V; a phase noise of minus 90 dBc/Hz at 100 kHz offset (minus 85 dBc/Hz at 100 kHz offset) for the first (second) type of VCO, respectively.