Giovanni Capoccia

A broadband toolbox for scanning microwave microscopy transmission measurements

In this paper, we present in detail the design, both electromagnetic and mechanical, the fabrication, and the test of the first prototype of a Scanning Microwave Microscope (SMM) suitable for a two-port transmission measurement, recording, and processing the high frequency transmission scattering parameter S21 passing through the investigated sample. The S21 toolbox is composed by a microwave emitter, placed below the sample, which excites an electromagnetic wave passing through the sample under test, and is collected by the cantilever used as the detector, electrically matched for high frequency measurements. This prototype enhances the actual capability of the instrument for a sub-surface imaging at the nanoscale. Moreover, it allows the study of the electromagnetic properties of the material under test obtained through the measurement of the reflection (S11) and transmission (S21) parameters at the same time. The SMM operates between 1 GHz and 20 GHz, current limit for the microwave matching of the cantilever, and the high frequency signal is recorded by means of a two-port Vector Network Analyzer, using both contact and no-contact modes of operation, the latter, especially minded for a fully nondestructive and topography-free characterization. This tool is an upgrade of the already established setup for the reflection mode S11 measurement. Actually, the proposed setup is able to give richer information in terms of scattering parameters, including amplitude and phase measurements, by means of the two-port arrangement.

Transmission microwave spectroscopy for local characterization of dielectric materials

In this work, the authors present a technique for the local characterization of the dielectric properties of materials. More in details, a setup will be described, and the related measurement modeling will be discussed. In this way, it is possible to obtain a calibrated and nondestructive determination of the dielectric constant in a submicrometric region; the detection of any surface or buried metallization is a straightforward application for microelectronics. The analysis is performed as a function of the frequency in the microwave range and, further on, the data can be transformed in time domain for one dimensional tomography. The authors will show that microwave spectroscopy can be performed by means of standard coaxial pins employed as probes for measurements both in reflection and transmission mode, giving the information of the frequency dependent properties of the exploited material or structure by means of the measured impedance. Experiments are performed in the range between 1 and 18 GHz, and d...

Wafer-level thin film micropackaging for RF MEMS applications

In this work, thin film packages were developed for radio-frequency microelectromechanical system (RF MEMS) configurations. The fabricated packages are suspended membranes in the multilayer SixNyHz/aSi/SixNyHz on conductive coplanar lines of different length. Several geometric parameters of the membranes, which are the length, the curvature radius at the vertices of the rectangular base, the density and the diameter of holes, were also varied. The mechanical properties of the suspended membranes were investigated by surface profilometry as a function of the geometric parameters. Finally, the RF characterization was performed to evaluate the impact of the package on the coplanar line performance. Hence, the proposed study provides results of crucial importance for the application of thin-film suspended microstructures for the packaging of RF MEMS devices.

Tailoring design and fabrication of capacitive RF MEMS switches for K-band applications

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.