Wideband and high reliability RF-MEMS switches using PZT/HfO2 multi-layered high K dielectrics

The novel approach using a PZT/HfO₂ multi-layered dielectric with high equivalent dielectric constant was investigated for obtaining high switching isolation of capacitive contact type MEMS switches. Compared with the use of Si₃N₄, PZT/HfO₂ demonstrated high dielectric constant, high breakdown voltage and very low leakage current, which advantage isolation performance and low power consumption. To test dielectric reliability, the charging effects on Si₃N₄ and PZT/HfO₂ were studied by measuring leakage current density via constant bias stressing. After 10⁴-second test, the PZT/HfO₂ shows the current density of nearly 10^-3 times lower than Si₃N₄. To test the necessary stressing time until reaching the current level of 10^-6A, this PZT/HfO₂ also performed nearly 140 times longer than Si₃N₄. Regarding to switching performance, the preliminary results demonstrated insertion loss of less than -0.5dB with operating bandwidths of 40GHz (one-bridge switch) and 30GHz (π-match switch), respectively. Furthermore, the it-match switches also demonstrated significantly high isolation of -35∼-65dB with operating bandwidth from 50MHz to 50GHz, which have better isolation than one-bridge switches.