Performance Improvement of RF MEMS Capacitive Switch with Highdielectric constant materials

摘要

A novel approach to improve the performance of a capacitive shunt switch using high dielectric constant materials and monolithic integration based on copper interconnection process is investigated here. To get a high isolation and low actuation voltage, a high dielectric constant material (Ba_(0.65)Sr_(0.35)TiO_3) was used in the MIM (metal-insulator-metal) structure, which determines switching isolation characteristics. The realized dielectric constant of this BST thin film was 367 for a thickness of 1500A. When the BST film is used between the membrane and transmission line instead of silicon nitride, the air gap can be reduced into 1.85 mu m with isolation ratio of 4500:1 and actuation voltage of 18V. In case of 0.85mu m air gap, it is expected to give the isolation ratio of over 2000:1 and actuation voltage less than 7V. We have also investigated a monolithic integration process of RF MEMS switch with CMOS circuitry using a back-end-of-line process of Cu interconnection technology. This process integration is based on the 6 level Cu interconnection process that includes the MIM capacitor structure.