A Wafer-Scale Packaging for RF DMTL Phase Shifter

In this paper, a wafer-scale gold-to-gold thermo-compression bonding packaging based on an RF distributed MEMS transmission line (DMTL) phase shifter is proposed. The DMTL phase shifter, based on a coplanar waveguide (CPW), has symmetrical saw-shaped structures in the CPW signal line under the MEMS bridge and an insulation layer in the middle of the structures. Two Si wafers are bonded together using gold-to-gold thermo-compression bonding with one as the cap wafer and the other as the substrate wafer which embodies RF DMTL phase shifter. A CST software is used for the modeling, simulation and optimization from 30 to 40 GHz. Results show that the proposed design, with a 35 GHz central resonant frequency, has a return loss less than -10 dB within 2.4 GHz bandwidth range and for each RF MEMS switch-type bridge, as high as 60 degrees phase shift is realized. Compared with the naked MEMS phase shifters, the return loss can be improved by 3 dB, and the performance of phase shift remains almost the same.