MEMS capacitive switch with stable actuation voltage over a broad temperature range

The pull-in and up-state capacitance of two types of switch have been measured for temperatures from -25 to 75°C. In one device, the plate is suspended by meander springs, while in the second by straight springs. Experiments show that the change in the pull-in and capacitance in meander switch are only 0.2 V and 5 fF over the entire temperature range. The straight switch has a high measured slope of pull-in and capacitance change across the same temperature range: 0.34 V/°C and -0.53 fF/°C, respectively. Finite Element Method (FEM) simulation indicates that the high coefficient of temperature expansion of switch metal causes the movable electrode to expand as the temperature increases. In response to this effect the air-gap and capacitance in the straight switch significantly change, while in the meander switch the metal expansion is largely compensated for by the spring design.