We report on measurements of the time dependent capacitance of a RF MEMS shunt switch. A high time resolution detection setup is used to determine switching time and motion of the device. From the equation of motion the damping force is extracted. The measured damping force is found to be approximately proportional to the speed over the gap distance to the third power (F D ∝ v/z 3 ), in good agreement with squeeze film damping theory. Measurements at low pressure show underdamped harmonic oscillations in the opening motion and contact bounce effects in the closing motion. Effects of dielectric charging on the C-V curves are discussed. Experimental results are compared with electromechanical and damping simulations.

The switching time (ts) for polarization reversal in ferroelectric films of PbZr0.53Ti0.47O3 and La-substituted PbTiO3 has been investigated. The films were prepared by spin-on and metalorganic decomposition followed by processing into ferroelectric capacitors having electrode areas ranging from 9 to 50 000 μm2. Pulse measurements show that under all our experimental conditions ts is instrumentally limited and that therefore the true switching time is smaller than the experimental resolution of 1.8 ns. This very fast polarization reversal can be explained by a nucleation-rate-controlled switching mechanism.

A study of the stresses in a ferroelectric capacitor stack deposited on an oxidized silicon substrate is presented. The capacitor stack was prepared with sputtered Pt bottom and top electrodes and a ferroelectric film of composition PbZrxTi1−xO3 (PZT) with x≊0.5 which was deposited using a modified sol-gel technique. The stresses were determined by the changes in the radius of curvature of the wafer following the deposition steps, during and after annealing treatments, and after etching steps in which the top electrode, the PZT film, and the bottom electrode were successively removed. The largest stress effects are found in the Pt electrodes which are deposited under conditions giving an intrinsic compressive stress. An annealing treatment exceeding 500 °C changed the stress of the bottom electrode from ≊−750 MPa (compressive) to a large tensile stress (≊1 GPa). This stress is largely thermal and is caused by the differences in thermal-expansion coefficients of the Pt film and the Si substrate. The stress of the PZT film is numerically relatively small (below ≊200 Mpa) and it is found to be of both thermal and intrinsic origin. The deposition and annealing of the top electrode has a profound influence on the stress of the PZT film as well as on the electrical properties. The stress behavior of the as-deposited PZT film shows a poling direction mainly in the plane of the substrate. An annealing of the complete capacitor stack changes the poling direction of the ferroelectric film to be perpendicular to the substrate. This explains the observed electrical switching properties of as-prepared as well as annealed ferroelectric capacitors.