Electron-phonon coupling in Ti/TiN MKIDs multilayer microresonator

Over the last few years there has been a growing interest toward the use of superconducting microwave microresonators operated in quasi-thermal equilibrium mode, especially applied to single particle detection. Indeed, previous devices designed and tested by our group with X-ray sources in the keV range evidenced that several issues arise from the attempt of detection through athermal quasiparticles produced within direct strikes of X-rays in the superconductor material of the resonator. In order to prevent issues related to quasiparticles self-recombination and to avoid exchange of athermal phonons with the substrate, our group focused on the development of thermal superconducting microresonators. In this configuration resonators composed of multilayer films of Ti/TiN sense the temperature of an absorbing material. To maximize the thermal response, low critical temperature films are preferable. By lowering the critical temperature, though, the maximum probing power bearable by the resonators decrease abruptly because of the weakening of the electron-phonon coupling. A proper compromise has to be found in order to avoid signal to noise ratio degradation. In this contribution we report the latest measurement of the electron-phonon coupling

Assessment of ORDYL SY 355 dry film for RF MEMS 0-level packaging

RF MEMS must be protected by a suitable package. A simple and cheap solution is to use quartz caps bonded by a polymer. This work reports on the use of ORDYL SY 355, a photosensitive dry film. The caps fabrication and bonding process were developed and tests were performed to define performance. Shear tests demonstrated good adhesion to the substrate and water immersion the sealing capability. Caps bonded on CPW and microstrip lines demonstrated negligible or very low impact on the RF performance in the 0-30GHz tested frequency band. Preliminary tests on capped RF MEMS switches indicated good performance of both capacitive and ohmic contact switches. Yield of ohmic switches resulted more sensitive to process conditions requiring a more accurate control

RF-MEMS switches for a full control of the propagating modes in uniplanar microwave circuits and their application to reconfigurable multimodal microwave filters

This is a copy of the author 's final draft version of an article published in the journal Microsystem technologies. The final publication is available at Springer via http://dx.doi.org/10.1007/s00542-017-3379-8In this paper, new RF-MEMS switch configurations are proposed to enable control of the propagating (even and odd) modes in multimodal CPW transmission structures. Specifically, a switchable air bridge (a switchable short-circuit for the CPW odd mode) and switchable asymmetric shunt impedances (for transferring energy between modes) are studied and implemented using bridge-type and cantilever-type ohmic-contact switches, respectively. The switchable air bridge is based in a novel double ohmic-contact bridge-type structure. Optimized-shape suspension configurations, namely folded-beam or diagonal-beam for bridge-type switches, and straight-shaped or semicircular-shaped for cantilever-type switches, are used to obtain robust structures against fabrication-stress gradients. The switches are modelled using a coupled-field 3D finite-element mechanical analysis showing a low to moderate pull-in voltage. The fabricated switches are experimentally characterized using S-parameter and DC measurements. The measured pull-in voltages agree well with the simulated values. From S-parameter measurements, an electrical model with a very good agreement for both switch states (ON and OFF) has been obtained. The model is used in the design of reconfigurable CPW multimodal microwave filters.Peer ReviewedPostprint (author's final draft

RF-MEMS Switches Designed for High-Performance Uniplanar Microwave and mm-Wave Circuits

Radio frequency microelectromechanical system (RF-MEMS) switches have demonstrated superior electrical performance (lower loss and higher isolation) compared to semiconductor-based devices to implement reconfigurable microwave and millimeter (mm)-wave circuits. In this chapter, electrostatically actuated RF-MEMS switch configurations that can be easily integrated in uniplanar circuits are presented. The design procedure and fabrication process of RF-MEMS switch topologies able to control the propagating modes of multimodal uniplanar structures (those based on a combination of coplanar waveguide (CPW), coplanar stripline (CPS), and slotline) will be described in detail. Generalized electrical (multimodal) and mechanical models will be presented and applied to the switch design and simulation. The switch-simulated results are compared to measurements, confirming the expected performances. Using an integrated RF-MEMS surface micromachining process, high-performance multimodal reconfigurable circuits, such as phase switches and filters, are developed with the proposed switch configurations. The design and optimization of these circuits are discussed and the simulated results compared to measurements

High kinetic inductance NbTiN films for quantum limited travelling wave parametric amplifiers

A wide-bandwidth and low-noise amplification chain in the microwave regime is crucial for the efficient read-out of quantum systems based on superconducting detectors, such as Microwave Kinetic Inductance Detectors (MKIDs), Transition Edge Sensors (TESs), Magnetic Microcalorimeters (MMCs), and RF cavities, as well as qubits. Kinetic Inductance Travelling Wave Parametric Amplifiers (KI-TWPAs) operated in a three-wave mixing fashion have demonstrated exceptional dynamic range and low-noise performance, approaching the quantum limit. These amplifiers can be fabricated using a single layer of a high kinetic inductance film as weakly dispersive artificial transmission lines, with the ability to control the phase-matched bandwidth through dispersion engineering. In this study, we present the optimisation of the rf sputter-deposition process of NbTiN films using a Nb80%T20 target, with the goal of achieving precise control over film characteristics, resulting in high kinetic inductance while maintaining a high transition temperature. The parameter landscape related to the different sputtering conditions, such as pressure, power, and nitrogen flow, has been explored and the film thickness has been used as a fine-tuning parameter to adjust the properties of the final NbTiN films used for the fabrication of KI-TWPAs. As a final result, we have obtained a NbTiN film with a kinetic inductance of 8.5 pH/sq which we have exploited to fabricate KI-TWPA prototype devices, showing promising amplification performance

MARE, Microcalorimeter Arrays for a Rhenium Experiment: A detector overview

Abstract We describe and discuss the features of MARE, an experiment based on arrays of rhenium low temperature microcalorimeters that have the potential to bring the sensitivity to the neutrino mass down to 0.2 eV, by studying the beta spectrum of Re 187 ( Q -value = 2.47 keV)

Electro-Mechanical Performance Analysis of RF MEMS Switches

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 the devices a very pertinent issue and involves both the process and device characterization. In this paper we describe the experimental setup and measurement results on RF MEMS switches fabricated for DC to 30GHz applications. The on-wafer experimental setup, based on standard manual microprobe station provides dual pulse actuation voltage waveforms with programmable period and amplitude. The usefulness of the dual-pulse testing is demonstrated by the minimal charge generation in the dielectric layer and capacitance measurements with negligible variations over long measurement periods

Suspended connection array for ultra low temperature applications

A silicon MEMS based component is projected and fabricated, that allows for minimum heat conductivity. while providing electrical connection on many channels by adopting an array of suspended superconducting metal lines, for ultra low temperature applications in the order of hundreds of microkelvin. The device is designed with L-Edit™ software and is fabricated at ITC-IRST microelectronics facility. The process has three mask levels and is divided into two splittings: one splitting is based on SU8 as polymer underlayer, the other uses polyimide. Bulk micromachining by anisotropic wet etching is used to create a cavity underneath the metal lines, and the dielectric layers underneath the lines are then dry etched leaving them suspended. The components are fabricated and technology issues related to the processing are investigated: self aligning of the polymer to the metal layer is examined to evaluate the undercut during plasma etching, and final release of the structure by silicon oxide removal is studied