An LC-tank network with reconfigurable resonance frequency is designed and implemented fully in R... more An LC-tank network with reconfigurable resonance frequency is designed and implemented fully in RF-MEMS technology. An ohmic switch with interdigitated signalactuation electrodes is exploited in a shunt configuration for selectively bypassing an inductor. The resulting two alternative resonance frequencies are predicted by circuit simulations and validated through s-parameter based on-wafer characterisation. Frequencies of 1.375 GHz and 3.605 GHz are obtained for the up and down switch states, with Q-factors of 7.2 and 14.4 respectively. Lumped element equivalent circuit analysis identifies main loss mechanisms in lossy coupling to ground and ohmic contact series resistance.
We propose the design of a reconfigurable impedance matching network for the lower RF frequency b... more We propose the design of a reconfigurable impedance matching network for the lower RF frequency band, based on a developed RF-MEMS technology. The circuit is composed of RF-MEMS ohmic relays, metal-insulator- metal (MIM) capacitors and suspended spiral inductors, all integrated on a high resistivity Silicon substrate. The presented circuit is well-suited for all applications requiring adaptive impedance matching between two in principle unknown cascaded RF-circuits. The fabrication and testing of a monolithic integrated prototype in RF- MEMS technology from ITC-irst is currently underway.
This paper describes a method to manufacture through wafer via holes with tapered walls for RF ap... more This paper describes a method to manufacture through wafer via holes with tapered walls for RF applications. The main purpose was the need to obtain tapered walls for via holes that allow to deposit seed and barrier layers by Physical Vapor Deposition (PVD). Method consist in consecutively using of the two basic process types for DRIE technique: isotropic and anisotropic etchings. Thus via holes with 20μm and 100μm having tapered walls with angles between 14° and 18° were manufactured. Also, thin metal layers were deposited on the walls by e-beam technique.
RF MEMS based switch matrices have several advantages compared to the mechanical or solid-state s... more RF MEMS based switch matrices have several advantages compared to the mechanical or solid-state switch based ones for space applications. They are compact, light and less lossy with a high linearity up to high frequency. In this work, a 12 × 12 switch matrix with RF MEMS and LTCC technologies is presented based on the planar Beneš network. The simulated performance of the 12 × 12 switch matrix is below −12 dB IL (Insertion Loss) up to C band and −15 dB RL (Return Loss) up to Ku band. Moreover, it has a good isolation better than −50 dB. A 4 × 4 switch matrix with the same design process and technologies is fabricated and measured to verify the 12 × 12 switch matrix design process. The measured performance agrees very well to the simulations.
Experimental numerical dynamic characterization of series rf mems
ABSTRACT In this paper a coupled numerical and experimental approach to analyze the mechanical be... more ABSTRACT In this paper a coupled numerical and experimental approach to analyze the mechanical behaviour of series resistive RF M.E.M.Switches produced by Microsystems Division of ITC-irst is demonstrated. The switch consists in a thin gold-chromium membrane suspended on both an interrupted RF line and a pad. In the narrow central part two wings realize the contact with the dimples placed at the end of the underpass line when a difference of potential is applied between the pad and the bridge, generating an electrostatic force that pulls down the structure. The problem of reliability, today, is the principal obstacle for a complete diffusion of these switches in several RF applications. The aim of this work is the study of the influence of the parameters (geometry, material elastic properties, residual stress, physics conditions of the fluid that surrounds the bridge) on the MEMS dynamic. A Finite Element Model has been developed to characterize the mechanical behaviour of the system, with a particular focus to the fluid-structure interactions that strongly affect the motion of the switch. A experimental laser doppler vibrometry based technique has been applied in order to validate the model.
We hereby discuss effects and consequences of using certain measurements approaches on the charge... more We hereby discuss effects and consequences of using certain measurements approaches on the charge trap analysis of RF-MEMS switches during cycling tests. We analyze how measurements are affected when the shape of the pulse changes, when the cycling frequency decrease and when measurements are carried out as a function of temperature. The trends here presented must to be taken into account when devices, that suffer of severe charge trapping phenomena, like those used in the following experiments, are considered. The real goal in fact, is to fully characterize the real performances of the devices separating the effects that different measurements analysis have on the device itself.
Lucrarea prezintă o metodă nouă de realizare a unor treceri prin plachetele de siliciu cu pereţi ... more Lucrarea prezintă o metodă nouă de realizare a unor treceri prin plachetele de siliciu cu pereţi înclinaţi, utilizând un proces de corodare uscată de tip DRIE (Deep Reactive Ion Etching) cu izotropie variabilă. Sunt prezentate principiul de realizare a trecerilor (bazat pe utilizarea unei corodări anisotrope de tip Bosch) şi optimizarea procesului pentru obţinerea unui control bun al unghiurilor de înclinare a pereţilor. This paper presents a new method of tapered walls through silicon wafers via holes (TSV) manufacturing, using a variable isotropy DRIE (Deep Reactive Ion Etching) process type. TSV manufacturing method is presented (based on Bosch type anisotropic etching), as well as process optimization for a very good control over the wall angles.
RF MEMS are assuming a great importance in the fast evolving telecommunication market and space a... more RF MEMS are assuming a great importance in the fast evolving telecommunication market and space applications. In the last years a flexible technology platform has been developed and continuously optimized at FBK (Italy) for the fabrication of RF MEMS basic components as well as complex RF circuits working in the frequency range from sub-GHz up to more than 100 GHz. The paper reports about the fabrication process and its capabilities. The most important process features are described together with some modifications required for the manufacturing of specific devices, like dielectric less RF MEMS switches. Examples of produced devices and their performances are briefly presented.
International Journal of Microwave and Wireless Technologies, 2012
Two different topologies of radio frequency micro-electro-mechanical system (RF MEMS) series ohmi... more Two different topologies of radio frequency micro-electro-mechanical system (RF MEMS) series ohmic switches (cantilever and clamped–clamped beams) in coplanar waveguide (CPW) configuration have been characterized by means of DC, environmental, and RF measurements. In particular, on-wafer checks have been followed by RF test after vibration, thermal shocks, and temperature cycles. The devices have been manufactured on high resistivity silicon substrates, as building blocks to be implemented in different single-pole 4-throw (SP4 T), double-pole double-throw (DPDT) configurations, and then integrated in Low Temperature Co-fired Ceramics (LTCC) technology for the realization of large-order Clos 3D networks.
Euv, X-Ray, and Gamma-Ray Instrumentation for Astronomy V, 1994
We are developing Si-implanted thermistors to realize high resolution microcalorimeters. We plan ... more We are developing Si-implanted thermistors to realize high resolution microcalorimeters. We plan to use these devices in an experiment for the determination of the neutrino mass. The measure implies the evaluation of the correct end-point energy of a beta spectrum with a calorimetric approach. Our study is devoted to outline the optimum fabrication process concerning performances and reproducibility. For such reasons we have realized Si thermistors with different concentration of dopant impurities and with different implant geometries. Tests are performed between 4.2 and 1 .2 K using a pumped helium cryostat, and selected samples are characterized at very low temperatures in a dilution refrigerator. Good reproducibility of the devices is necessary for producing an array of detectors. At the same time suitable electronics are developed to optimize the detectors preamplifiers link: minimization of the parasitic capacitance is necessary to reduce the integration of signal and to maximize the speed response of the detector.
Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment, 1998
Massive bolometric detectors operated at very low temperatures (K10 mK) can be used to search for... more Massive bolometric detectors operated at very low temperatures (K10 mK) can be used to search for rare events, such as Double Beta Decay and interactions of Dark Matter candidates. In experiments of this type it is important to keep the detector response steady within 0.1% level over periods of the order of one year or more, often in conflict with the intrinsic instabilities of the cryogenic setups. Here, a powerful method to stabilize detector response is described: using calibrated amounts of energy, injected by means of alpha particles or resistive heaters, a correlation between pulse amplitude and detector bias can be established. This correlation can be used to correct off-line the amplitudes of every pulse. The satisfactory results achieved with this technique are reported and discussed. For this purpose heavily doped Si heaters with steady resistances at cryogenic temperatures were designed and succesfully tested.
Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment, 2006
Neutrino oscillation experiments have proved that neutrinos are massive particles, but can't dete... more Neutrino oscillation experiments have proved that neutrinos are massive particles, but can't determine their absolute mass scale. Therefore the neutrino mass is still an open question in elementary particle physics. An international collaboration is growing around the project of Microcalorimeter Arrays for a Rhenium Experiment (MARE) for directly measuring the neutrino mass with a sensitivity of about 0.2eV/c 2. Many groups are joining their experiences and technical expertise in a common effort towards this challenging experiment. We discuss the different scenarios and the impact of MARE as a complement of KATRIN.
On-wafer electro-mechanical characterization of silicon MEMS switches
Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS 2003.
Abstract The feasibility of integrating the RF MEMS switches in space and wireless communication ... more Abstract The feasibility of integrating the RF MEMS switches in space and wireless communication systems has generated tremendous interest in related design, fabrication and characterization methodologies. The space applications make long term reliability of ...
An interdigitated design for MEMS RF-switches is applied to both a shunt and a series ohmic conta... more An interdigitated design for MEMS RF-switches is applied to both a shunt and a series ohmic contact con- figuration. Interdigitated Al-Ti-TiN RF-signal paths and poly actuation electrodes are arranged underneath an electrodeposited gold plate, suspended by four thin- ner gold beam springs. Ohmic contact occurs at pull- in between the gold plate and the RF-signal elecrodes only. Measurements show insertion loss better than 0.8 dB and isolation better than 20 dB up to 13 GHz. Ex- tracted lumped element equivalent circuits show intrin- sic contact resistances of 1.6 Ω in the shunt and 4.5 Ω in the series switch. The interdigitated topology of RF- signal and actuation electrodes results in uniform con- tact pressure distribution and consistently low contact resistance.
In this paper, a numerical simulation technique suitable for device-level analysis of ion-sensiti... more In this paper, a numerical simulation technique suitable for device-level analysis of ion-sensitive devices (ion-sensitive field-effect-transistor (ISFET) and light-addressable potentiometric sensor (LAPS)) is presented. Models of the charge layers which develop at the electrolyte–insulator interface of an electrolyte insulator-semiconductor (EIS) system are incorporated into the device equations, thus providing a self-consistent picture of charge and field distribution within the semiconductor domain. To accomplish the simulation of LAPS devices, an AC-modulated optical generation rate has been introduced as well. A TCAD tool, based on the proposed approach, has been developed, which allows for the electrical characterization and for the extraction of circuit-simulation parameters of ion-sensitive devices. Validation of the device-analysis technique comes from the comparison between predicted electrical responses and actual device measurements.
Polysilicon mesoscopic wires coated by Pd as high sensitivity H2 sensors
Sensors and Actuators B: Chemical, 2002
In this paper, a new class of H2 sensors made up of mesoscopic polysilicon wires coated by pallad... more In this paper, a new class of H2 sensors made up of mesoscopic polysilicon wires coated by palladium is presented. Using surface micromachining combined with an usual microelectronic planar process, polysilicon wires of the following dimensions have been constructed: from 0.25 up to 3.7μm wide, from 100 up to 140μm long, about 600nm thick. Because of their high surface/volume ratio,
High statistics calorimetric measurements of the β spectrum of 187 Re are being performed with ar... more High statistics calorimetric measurements of the β spectrum of 187 Re are being performed with arrays of silver perrhenate crystals operated at low temperature. After a modification of the experimental setup , which allowed to substantially reduce the background of spurious counts and therefore to increase the sensitivity on the electron antineutrino mass, a new measurement with 10 silver perrhenate microbolometers is running since July 2002. The crystals have masses between 250 and 350 µg and their average FWHM energy resolution, constantly monitored by means of fluorescence X-rays, is of 28.3 eV at the β end-point. The Kurie plot collected during 4485 hours×mg effective running time has an end-point energy of 2466.1 ± 0.8stat ± 1.5syst eV, while the half lifetime of the decay is found to be 43.2 ± 0.2stat ± 0.1syst Gy. These values are the most precise obtained so far for 187 Re. From the fit of the Kurie plot we can deduce a value for the squared electron antineutrino mass m 2 νe of 147 ± 237stat ± 90syst eV 2. The corresponding 90% C.L. upper limit for m νe is 21.7 eV.
dei Materiali, I-38050 Mesiano (TN), Italy We report on a new method to measure the electron anti... more dei Materiali, I-38050 Mesiano (TN), Italy We report on a new method to measure the electron antineutrino mass, consisting of the end-point study of la7Re P-spectrum (Q-vahre=2.6 keV) collected calorimetrically (source=detector approach) with high energy resolution and statistics. The proposed detector is a micro-bolometer, single or in an array structure, containing a total rhenium mass of N 1 mg, operated at a temperature of a few tens of mK and able to reach 10 eV energy resolution. As phonon sensors, we are developing silicon thermistors doped by implantation; some tests are performed also with neutron transmutation doped germanium thermistors. We have obtained up to now promising energy resolutions down to N 11 eV with tin absorbers (as test devices) and N 70 eV with rhenium absorbers.
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Papers by Benno Margesin