RF CMOS-MEMS capacitor having large tuning range

Several CMOS-MEMS tunable capacitors have been designed, fabricated and tested. Large-tuning ranges and high Q values are achieved. The structures were made from the CMOS interconnect stack using a maskless CMOS micromachining process. The 1/sup st/ generation capacitors were fabricated using Austria Microsystems (AMS) 0.6 /spl mu/m and Agilent 0.5 /spl mu/m CMOS process. These devices have a measured nominal capacitance of 209 fF and a measured quality factor 28 at 1.5 GHz. The capacitance change is measured from 209 fF to 294 fF within a 24 V control voltage, and 72.4 mW power at 1.5 GHz. 2/sup nd/-generation tunable capacitors in TSMC 0.35 /spl mu/m CMOS process have larger tuning range and more power efficiency than the 1st generation designs. For these new designs, 3.52 to 1 tuning range has been measured with tuning from 42 fF to 148 fF within a 12 V control voltage, and 34 mW power at 1.5 GHz. This recent design has a measured Q of 52 at 1.5 GHz. Electro-thermal actuation is used for all tunable capacitor designs. The essential differences between this work and prior work are the CMOS compatibility and using a maskless CMOS micromachining process.