Lateral RF MEMS capacitive switch based on HfO2 film for millimeter wave applications

In this paper, we developed a thermal actuated lateral RF MEMS capacitive switch using the HfO₂ film as sidewall isolation dielectric based on atomic layer deposition (ALD) process to approve the isolation and reliability. In close state, the HfO₂ film provides strong capacitive coupling between the signal line and switching plate, as well as electrical isolation performance between the switching plate and actuation structure thank to its high permittivity, and excellent conformal coverage and thermal isolation properties. The measured insertion loss and isolation of the fabricated switch are 2.1dB and 37dB at 35GHz, respectively. Moreover, the isolation is 25dB or better in the range of 31-40GHz. These results demonstrate that the HfO₂ film is a good candidate material serving as sidewall dielectric of capacitive switch.