The impact of 2 MeV protons and 10 keV X-rays radiation stresses on electrostatically actuated ohmic RF-MEMS switches has been analyzed at increasing radiation dose and during subsequent annealing at room temperature. Small variations of electrical parameters (actuation and release voltages) have been identified, accompanied by a strong rf-performances degradation. Monte Carlo TRIM simulations have been carried out to understand the mechanisms responsible of such degradations, finding that both NIEL and ionizing damages appear to play an important role

In this paper, the physical loss mechanisms in boron doped poly-SiGe are analyzed theoretically and experimentally. The phonon losses were calculated theoretically for different germanium and doping concentrations. The theoretical analysis showed that Akhiezer damping sets a fundamental lower limit to the internal damping. Calculated limits for the f×Q due to Akhiezer damping were ∼1×1014 Hz for SiGe with low Ge content and ∼2×1013 Hz for SiGe with high Ge content. However, in the experiments it was found that an internal friction loss mechanism limits the maximum achievable f×Q in our material to 3×1012 at a frequency of 130 MHz. Experimentally the loss mechanisms were studied further by preparing SiGe layers with different Ge/H/B content. The acoustical losses were measured by fabricating a micromechanical resonator from the layers. The measurements identified a thermally activated loss mechanism. By studying the microstructure of the SiGe layers, we identified interface defects and interstitial as the most important loss mechanisms. Furthermore, the experiments show that at high frequencies (>130 MHz) the achievable f×Q-products of SiGe are close to the values, which can be achieved with single crystal materials.

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