# Research and Analysis of MEMS Switches in Different Frequency Bands
## 3 The Research Status of MEMS Switches in Different Frequencies
### Research on Temperature Intability of MEMS Switches
The circular structure was divided into several identical radial switches to achieve a symmetrical structure, which was insensitive to temperature and stress gradient effects. The switches showed a variation <9 V in their pull-down and release voltages from 25 \({}^{\circ}\)C to 95 \({}^{\circ}\)C.  
[PERSON] et al. [20] designed a novel vertical MEMS capacitive switch, which was not sensitive to thermal stresses based on a lateral thermal buckle-beam actuator design. A suspended plate was connected to two rigid anchors by N-beams. The thermal contraction/expansion of the plate was translated to an in-plane displacement. As a result, there was not displacement in the vertical direction for the suspended plate, and the pull-down voltage maintained a constant versus temperature. The variation of the pull-down voltage was 50 mV/\({}^{\circ}\)C from 25 \({}^{\circ}\)C to 125 \({}^{\circ}\)C. [PERSON] et al. [113] developed a temperature-stable metal contact RF MEMS switch using a thermal buckle-beam structure to reduce the temperature sensitivity. The structure could also weaken the sensitivity to stress gradients on the pull-down voltage. The variation of the pull-down voltage was \(-\)120 mV/\({}^{\circ}\)C from \(-\)20 \({}^{\circ}\)C to 100 \({}^{\circ}\)C.  
[PERSON] et al. [114] reported that the rate of change in actuation voltage using molybdenum as the mechanical material of MEMS capacitive switches was reduced from 0.1 V/\({}^{\circ}\)C to 0.3 V/\({}^{\circ}\)C for aluminum to less than 0.03 V/\({}^{\circ}\)C. The switches could operate at least 20 billion cycles without failure and work up to at least 150 \({}^{\circ}\)C without any buckling. [PERSON] et al. [115] demonstrated that a switch with the molybdenum membrane showed a significantly reduced sensitivity to the change of ambient temperature resulting an actuation voltage that varied by less than 0.035 V/\({}^{\circ}\)C, but varied by 0.3 V/\({}^{\circ}\)C for the aluminum membrane. Both aluminum and molybdenum switches showed a power-handling capacity of 600 mW, and the lifetime for the switch with molybdenum membrane exceeded 2 \(\times\) 10\({}^{9}\) cycles. [PERSON] et al. [116] reported novel MEMS tunable capacitors with low-temperature sensitivity. In the design, a cantilever beam was connected to rigid anchors using two small tethers. These tethers could reduce the initial deflection of the cantilever tip because of residual stress gradients. The two tethers were tilted by an angle from the y-axis to reduce the device temperature sensitivity. The designs presented measured pulldown voltage variation of <50 mV/\({}^{\circ}\)C at 20-120 \({}^{\circ}\)C.  
[PERSON] et al. [103] designed a MEMS metal-contact switch with stress and temperature stability for high-power applications. The switch was designed based on an inverted crab topology with four curved springs and a thick plate. This topology exhibited less sensitivity to stress gradients than fixed-free designs and less sensitivity to temperature and biaxial stress than fixed-fixed designs. The measured pull-down voltage was 71-77 V when the temperatures varied from 25 \({}^{\circ}\)C to 125 \({}^{\circ}\)C; the release voltage was 71-75 V from 25 \({}^{\circ}\)C to 105 \({}^{\circ}\)C.  
[PERSON] et al. [117] designed a thin-film packaged MEMS switched capacitor on silicon substrate. The MEMS capacitive structure was integrated into a protective dielectric shell of silicon nitride, and the actuation electrode was standing above the deflectable membrane. The membrane metal was Ti-Au, and the material of electrode was Al. The performance of the proposed switch was not sensitive to temperature changes. The variation of the pull-down voltage and release voltage was 77 mV/\({}^{\circ}\)C from 20 \({}^{\circ}\)C to 85 \({}^{\circ}\)C.  
[PERSON] et al. [118] designed a novel temperature-tolerant MEMS switch for Ka-band applications.