A High-Power Temperature-Stable Electrostatic RF MEMS Capacitive Switch Based on a Thermal Buckle-Beam Design

This paper presents the design, fabrication and measurements of a novel vertical electrostatic RF MEMS switch which utilizes the lateral thermal buckle-beam actuator design in order to reduce the switch sensitivity to thermal stresses. The effect of biaxial and stress gradients are taken into consideration, and the buckle-beam designs show minimal sensitivity to these stresses. Several switches with 4,8, and 12 suspension beams are presented. All the switches demonstrate a low sensitivity to temperature, and the variation in the pull-in voltage is ~ -50 mV/°C from 25-125°C. The change in the up-state capacitance for the same temperature range is <; ± 3%. The switches also exhibit excellent RF and mechanical performances, and a capacitance ratio of ~ 20-23 (Cυ. = 85-115 fF, C
_d
= 1.7-2.6 pF) with Q > 150 at 10 GHz in the up-state position is reported. The mechanical resonant frequencies and quality factors are f
_ο
= 60-160 kHz and Qm = 2.3-4.5, respectively. The measured switching and release times are ~ 2-5 μs and ~ 5-6.5 μs, respectively. Power handling measurements show good stability with ~ 4 W of incident power at 10 GHz.