An Electro-Thermal MEMS Variable Capacitor

A tunable capacitor based on the Micro-Electro-Mechanical Systems (MEMS) technology is designed and simulated which can be used for various applications such as oscillators, phase shifters, tunable filters, etc. There is no moving component in its structure so problems such as pull-in effects are passed over. Variations of this capacitor are based on the chemical properties of used material. Barium titanate with dielectric coefficient above 1000 and thickness of 300 nm is used as dielectric. Relative permittivity of this material varies linearly in a wide range between 1000 and 7000 for temperature changes from 100° to 125 °C, respectively meanwhile a heater made of nickel, cobalt and iron alloy is utilized with applying voltage between 1.47 V to 2.05 V. We use trench in the structure of capacitor with 2 μm opening diameter and 5 μm depth for better using wafer area, so a 0.81 pF capacitor at room temperature is formed. We replicate trenches with pitch of 3 μm in different arrays for the construction of proper variable capacitors for different applications from low to high frequencies. Capacitor tuning range in this design is about 600% linearly for different arrays of trench capacitor. COMSOL Multiphysics Software is utilized for exploring different parameters in this paper.