Electro/thermal measurements of RF MEMS capacitive switches

Abstract

An aspect-ratio-limited fabrication procedure for the secondary handling of miniaturized micromachined and fiber-fed gallium arsenide electrothermal probes is presented, and a completed probe is used to measure the electric field and temperature above an RF MEMS capacitive switch. The probe dimensions are 125 /spl mu/m /spl times/ 125 /spl mu/m /spl times/ 100 /spl mu/m. Measurements of switches with dimensions of 250 /spl mu/m /spl times/ 640 /spl mu/m are performed for RF powers between 252 mW and 6.7 W in the UP and DOWN states. Non-contact temperature measurements 25 /spl mu/m above the switch in the UP state show a thermal rise time of 0.63 /spl plusmn/ 0.05 seconds for an RF input power of 6.7 W. The accompanying temperature rise is 16.8 /spl plusmn/ 0.7/spl deg/C. In the DOWN state, the increase in temperature is 3.0 /spl plusmn/ 0.8/spl deg/C. Spatial line scans of temperature show the localization of heat energy in the UP state and its delocalization in the DOWN state due to conductive heat transfer into the substrate. Electric field measurements yield traveling waves in the UP state and standing waves in the down state. Standing waves in the DOWN state are consistent with preferential substrate heating on the input side to the switch.