Electrical characterization, modeling, and reliability investigation of Micro Electro-Mechanical Systems (MEMS) (linear inertial accelerometers, and switches for Radio Frequency applications)
Summary: A new research line concerning the characterization and reliability investigation of Micro-Electro-Mechanical-Systems (MEMS) has been started. The activity began with the investigation of linear inertial accelerometers, extending to the characterization and modeling of uncommon failure modes of electrostatically actuated switches for Radio Frequency (RF) applications. The main target of such activity has been (i) the analysis of the intimate way of working of MEMS (that combine electrical characteristics with mechanical ones as well); (ii) the evaluation of the most correct measurement methodology, taking a great care to the electro-mechanical nature of studied devices; (iii) the analysis of common and uncommon failure modes and mechanisms, by means of accelerated aging procedures ad-hoc developed for such highly promising devices; (iv) the testing of the reliability of MEMS devices stressed by means of uncommon phenomena typical of harsh environment like the spatial one (radiation and ESD stresses), and by means of mechanical shocks (with accelerations greater than 1000 g, in order to simulate the critical conditions that devices must withstand, for example, during the spacecraft launch or during the satellite solar panels opening).
Main results: The most important and original results can be summarized as follows:
- Development of test structures with the aim of (i) making easier the mechanical/electrical characterization, the (ii) failure analysis investigation, and (iii) trying to separate the effect of different failure mechanisms on the electrical parameters degradation.
- Ad-hoc measurement setups have been developed for the electrical/mechanical characterization of MEMS devices, and for speed-up possible failure mechanisms. Such setups have been used to evaluate contact degradation, charge trapping phenomena, elastic/plastic deformations, fractures, and structural elements stresses.
- Suitable accelerated aging procedures investigation and implementation, failure criteria definition, and electrical degradation modes analysis.
- Development of ad-hoc setups for the evaluation of reliability issues induced by radiation stresses, especially for the investigation of dielectric charge trapping phenomena.
Definition and implementation of realistic ESD stresses on RF-MEMS switches, taking particular care on failure criteria investigation and failure analysis under both off-state and fully working conditions.