High-k dielectrics for application in broadband radio frequency- microelectromechanical system capacitive shunt switch

130 nm-thick lead zirconate titanate(PZT)/45 nm-thick HfO₂ stack and single 45 nm-thick HfO₂ dielectric film were utilized as insulator layer in π-type radio frequency (RF) capacitive shunt switches for achieving high isolation performance in broadband application. Thin PZT film in perovskite structure mainly with (1 1 1) orientation was successfully prepared at low temperature (500°C) using sol-gel method. The thin PZT film exhibited excellent ferroelectric properties and high dielectric constant (κ ≈ 1185). Thin HfO₂ film was prepared by sputtering method in a gas mixture of O₂ and Ar. The thin HfO₂ film had the dielectric constant of about 17 and the dielectric strength of about 24 MV/cm. The switch of PZT/HfO₂ stack dielectric showed isolation performance better than -20 dB in the frequency range of 1 ∼ 35 GHz. The switch of HfO₂ had isolation performance better than -40 dB in the frequency of 5 ∼ 35 GHz, suggesting its attractive prospective in practical broadband application.