RF micro-electro-mechanical systems capacitive switches using ultra thin hafnium oxide dielectric

A π-type RF capacitive switch using about 45-nm-thick HfO₂ dielectric layer was fabricated. High isolation performance was obtained in wide-band range when the switch was down-state. The isolation was better than -40dB at the frequency range of 4-35 GHz. Particularly, the isolation was better than -50 dB in the frequency range of 8-12 GHz, i.e., X band. HfO₂ showed excellent process compatibility with conventional microfabrication procedure. The 45-nm-thick HfO₂ film was prepared using sputtering at room temperature so that it was feasible to be integrated into RF switch and other microwave circuits. The results of constant bias stressing showed that the ultra thin HfQ₂ had excellent reliability. The electric breakdown of HfO₂ was observed, which had no apparent negative effects on the reliability of the dielectric. HfO₂ dielectrics were attractive in the application of RF micro-electro-mechanical systems (MEMS) switch for new generation of low-loss high-linearity microwave circuits.