Post-enabled flip-chip assembly for manufacturable RF-MEMS

This work demonstrates the design, fabrication, and testing of two-dimensional variable capacitor arrays, which are integrated with RF circuits. The devices are fabricated in a commercially available foundry process (MUMPs) and then flip-chip transferred to a RF circuit substrate using tethers and posts. This "post-enabled" flip-chip assembly allows 2/spl times/2, 3/spl times/3, and 4/spl times/4 variable capacitor arrays to be built with precise gap heights for multiple, repeatable digital capacitance levels. We design, measure, and test a total of 43 different plate/post configurations, which provided 18 different gap heights, spaced in 0.25 /spl mu/m increments. The post-enabled assembly significantly improves capacitive performance over previous work and it enables us to compare the RF performance. We measure a Q-factor above 200 at 0.936 GHz, a capacitance ratio of 4.69:1, and tuning range of 171 MHz in a resonator circuit.