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The paper reports about the technology platform for the fabrication of RF-MEMS devices developed at FBK. The most important process features, requirements and possible applications are presented and described. The basic fabrication process, together with some of the more important process variations and its capabilities are reported. Finally, some examples of produced devices and their performances are briefly presented.

An ad hoc microfabrication technique was employed for the optimization of thin hydrogenated silicon membranes for the first experimental application in the field of laser-driven proton acceleration. The tetra methyl ammonium hydroxide wet etching and further microfabrication processes allowed the optimization of the target structure and geometry. Samples were doped in a H2 environment during an annealing process at 420 °C in order to increase the hydrogen concentration in the silicon matrix. This solution enabled the production of high-current (about 100 mA at 1 m from the source) and multi-MeV proton beams.

This paper presents an analytical method to calculate residual stress and Young's modulus in clamped-clamped beams. These types of structures are a typical building block of many MEMS devices, and this guarantees accurate transferability of the measured parameters. The method is based on the determination of beam bending as a function of applied load by means of a surface profiler, and as a function of beam length. By modeling analytically both the elastic and the stress contribution to beam bending, it is possible to obtain both the stress value and Young's modulus by a simple fitting of the experimental data. Results are presented for electrodeposited gold beam arrays of different widths, but the method is in principle exploitable for every type of suspended film where the residual stress strongly influences the material properties. Accuracy and limitations of the method are also discussed.

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