Shunt capacitive radio-frequency microelectromechanical system (RF MEMS) switches were fabricated on silicon substrate and characterized in the RF domain. Various switch typologies were obtained by three different approaches, which are: (1) the change of the bridge geometric parameters, (2) the covering of the actuator with a floating metal, and (3) the deposition of the bridge directly on the actuator. The S parameters of the fabricated switches were measured in the up and down states, observing the impact on the RF performance of the variation of the geometric parameters and the fabrication process. The electromagnetic modelling of the fabricated switches was used to interpret the measured RF behaviour, allowing to elucidate the drawbacks of the non-perfect conforming of the bridge on the actuator. Finally, the reliability of the fabricated RF MEMS switches under a bipolar voltage excitation was evaluated by cycling tests. Hence, the study presented here provides guidelines to solve some issues of the tight correlation between design, fabrication, performance, and reliability of RF MEMS switches, in view of a large-scale development of these devices.

Space components need a ground characterization based on several solicitations, including mechanical and thermal stress, before their final qualification. In this paper, RF MEMS switches designed for redundancy logic have been extensively measured with promising results in terms of thermal and mechanical cycles. Packaging contributions have also been discussed.

Shunt capacitive radio-frequency microelectromechanical (RF MEMS) switches were modelled, fabricated and characterized in the K-band domain. Design allowed to predict the RF behaviour of the switches as a function of the bridge geometric parameters. The modelled switches were fabricated on silicon substrate, using a surface micromachining approach. In addition to the geometric parameters, the material structure in the bridge-actuator area was modified for switches fabricated on the same wafer, thanks to the removal/addition of two technological steps of crucial importance for RF MEMS switches performance, which are the use of the sacrificial layer and the deposition of a floating metal layer on the actuator. Surface profilometry analysis was used to check the material layer structure in the different regions of the bridge area as well as to investigate the mechanical behaviour of the moveable bridge under the application of a loaded force. The RF behaviour of all the fabricated switches was measured, observing the impact on the isolation of the manipulation of the bridge size and of the variations in the fabrication process.

This paper presents an electromagnetic modeling of a grounded metallic truncated cone to be used for calibration purposes of a microwave imaging system. The basic idea is to demonstrate the equivalence between the cone and a cylinder having a suitable radius, in order to simplify the computation of its capacity with respect to ground. A mathematical expression for the capacitance of the uniform cylinder is presented, and its validity is confirmed by comparing the data provided by this formula with numerical values given by a commercial simulator. Starting from this analytic result, the model of the cone is presented, and a procedure for the choice of the cylinder radius is discussed in detail. This methodology can be applied to calculate the contribution to the stray capacitance of a metallic tip used for scanning probe microscopy, and specifically for microwave sensing applications. In particular, the capacitance due to the conic part of the probe can be quantified, an operation that is usually a difficult task when trying to separate it from contribution of the experimental setup. In our opinion, this issue is very important to improve the accuracy of system calibration in the scanning microwave microscopy technique. (C) 2015 AIP Publishing LLC.

The paper presents a calibration of scanning microwave microscopy signals for doping profiling in MOS systems. The experimentally obtained S-parameters are matched through a linear relation to the calculated MOS system capacitance and then to doping. The proposed approach is verified by simulations with the equivalent LCR circuit as well as by experimental results obtained on a calibration sample with differently doped areas.

The analytical modelling of a grounded truncated metallic cone is presented in this work as a contribution to the de-embedding and calibration of a scanning microwave system based on capacitance measurements for imaging and spectroscopy purposes. First, an expression for the capacitance of a uniform cylinder is derived, and successively a procedure to determine an effective uniform cylinder radius for the truncated cone is developed. The truncated cone was chosen as a suitable geometry for the calculation of the stray capacitance versus ground of a metallic tip used for scanning probe microscopy and, more specifically, microwave sensing. An accurate calculation of the aforementioned capacitance is of outmost importance for system calibration in scanning microwave microscopy (SMM) technique.

Triangular metamaterial resonators, designed by RF MEMS cantilevers in coplanar waveguide (CPW) configuration, have been fabricated on alumina substrate and tested up to 40 GHz. A triangular split ring resonator has been etched in the central conductor of the CPW transmission line and the split is provided by a technologically actuated cantilever beam, i.e. with metal directly deposited without the sacrificial layer, to emulate the ideal actuation. Two main configurations of the triangular transmission line have been studied for narrowband microwave switching, the first one without the MEMS cantilever and the second one with a technologically actuated MEMS cantilever switch. Because of the contributions of both the resonator and the switch, the device has a narrow band switching feature. Moreover, the parameters extraction obtained by both the experiment and the simulation, show a metamaterial behavior of the exploited configuration.

A methodology towards de-embedding contact mode scanning microwave microscopy (SMM) reflection measurements is presented. A calibration standard that consists of differently doped stripes is required, while the reflection coefficient amplitude |S11|, is modeled and analyzed in the linear scale, instead of the commonly adopted dB scale. This allows the straightforward experimental determination of important parameters such as the effective tip radius and the magnitude of stray capacitances. Values of 145 nm and 22 fF have been obtained respectively. The proposed methodology can be easily and repeatedly performed during the experimental procedure, offering in this way the necessary de-embedding to get an enhanced accuracy on SMM measurements for semiconductors characterization.

This paper presents the design of distributed MEMS phase shifters by means of the image-parameters method. The proposed analytic approach utilizes a more precise modeling of the MEMS device with respect to that one usually adopted in literature. The most important analytic aspects concerning the synthesis technique are presented. As a demonstration of the method a structure characterized by a differential phase shift value of 90° is designed and simulated, exhibiting very good electric performance.

Space components need a ground characterization based on several solicitations, including mechanical and thermal stress, before their final qualification. In this paper, RF MEMS switches designed for redundancy logic have been extensively measured with promising results in terms of thermal and mechanical cycles. Packaging contributions have been also discussed.

This paper is focused on the design of the transmission lines utilized in microelectromechanical capacitive shunt connected switches. These transmission lines sections are employed as matching elements to improve the performance of the component in the on state. The image phase parameter is used to develop an analytic procedure for the synthesis of such transmission lines. The proposed method is applied for the design of a switch, adopting for the capacitive element the experimental data of a microelectromechanical device previously realized by the authors.

A 12×12 Switch Matrix Unit featuring silicon RF MEMS assembled on LTCC boards has been developed under a Contract with the European Space Agency (ESA) for satellite communication application. The Switch Matrix is a complete Engineering Model unit, housed in a mechanical box in aluminum with RF coaxial connectors and DC connectors for powering and commanding. To the authors' knowledge, it is the first complex equipment realized in Europe exploiting the advanced features of the RF MEMS and multilayer LTCC technology to achieve a significant mass and size reduction. Full wave simulations of entire structure are reported, as well as test results. Their agreement is good up to the satellite downlink C-band (3.7-4.2 GHz). An insertion loss of -20dB, return loss of -10dB and isolation of 40-45dB have been measured. The matrix is passive (not provided with amplifiers), having a DC power consumption of less than half watt due to the digital command circuitry.

We present a comprehensive analysis of the imaging characteristics of a scanning microwave microscopy (SMM) system operated in the transmission mode. In particular, we use rigorous three-dimensional finite-element simulations to investigate the effect of varying the permittivity and depth of sub-surface constituents of samples, on the scattering parameters of probes made of a metallic nano-tip attached to a cantilever. Our results prove that one can achieve enhanced imaging sensitivity in the transmission mode SMM (TM-SMM) configuration, from twofold to as much as 5× increase, as compared to that attainable in the widely used reflection mode SMM operation. In addition, we demonstrate that the phase of the S21 -parameter is much more sensitive to changes of the system parameters as compared to its magnitude, the scattering parameters being affected the most by variations in the conductivity of the substrate. Our analysis is validated by a good qualitative agreement between our modeling results and experimental data. These results suggest that TM-SMM systems can be used as highly efficient imaging tools with new functionalities, findings which could have important implications to the development of improved experimental imaging techniques.

We showed the capability of the SMM to measure calibrated capacitances and dopant densities on the nanoscale. In particular we have shown a noise level of 1 aF for capacitance measurements and a dynamic range of 10E14-10E20 atoms/cm3 for dopant profiling. The sensitivity for the dopant profiling varies with respect to the dopant density; overall we have a relative accuracy of 20% on both capacitance and dopant profiling measurement. Furthermore we were able to show a lateral resolution of 10 nm using standard electrical conductive cantilevers and semiconductor samples. There is upside potential along all the performance parameters in case they are required for the future VSMM project: the sensitivity of the capacitance measurement can potentially be improved to the sub-aF using standard PNA averaging capabilities while improved lateral resolution below 10 nm is envisioned using sharpened AFM tips. We tested the general useability of the capacitance calibration samples from MC2 including reproducibility, cleaning of dirt adhered to the gold caps, stability of the native oxide, the gluing of samples to steel plates for magnetic mounting etc. Overall the performance of the calibration samples is properly shown and verified by a large amount of test experiments. The MC2 calibration samples can be used for the further work in the VSMM project regarding SMM capacitance calibration, and the current SMM delivers enough sensitivity for the project objectives in terms of capacitance measurements and lateral resolution.

We have designed and fabricated a toolbox to perform S21 (transmission) measurements by using the Agilent 5600 LS AFM (SMM). In this type of measurement, an additional microwave emitter is located below the sample and the nano-scale probe of the SMM system (the tip) is located on the sample surface (or in close proximity) working as receiver of the transmitted wave. This set up allows to study the electromagnetic properties of the material under test obtained through the measurement of the S21 parameter by means of a two port VNA setup. Advanced microwave modelling software is used to study the measurement sensitivity, dynamic range, and other system characteristics like sub-surface depth resolution.

This paper is an extension of a previously published work concerning a novel approach for the design of RF MEMS switches in coplanar waveguide (CPW) configuration. The peculiarity of the method is to allow imposing the matching condition directly in analytic form. This result is obtained using the image parameter representation for the modeling of the device. Standard commercial simulators are used to develop a comparison among different switch configurations designed by means of the proposed modified approach. The numerical results confirm the validity of the method.

In this paper RF MEMS switches in coplanar waveguide (CPW) configuration designed for redundancy space applications have been analyzed, to demonstrate their reliability in terms of microwave performances when subjected to DC actuations up to one million cycles. As a result, both the investigated structures fulfill the current electrical requirements expected for redundancy logic purposes.