# 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  
Although, MEMS switches show high linearity, low loss, and low power consumption [6], many MEMS switches are affected by high-temperature sensitivity, especially at high RF power levels [105]. This sensitivity is especially present in multilayer structures and clamped-clamped structures, leading to a change in the air gap and thus, a change in the up-state capacitance and the pull-down voltage [106]. [PERSON] et al. [107] found that double-clamped switches were more vulnerable to temperature compared with cantilever switches. The pull-down voltage variations were more than 40% from 25 \({}^{\circ}\)C to 70 \({}^{\circ}\)C for the clamped-clamped switches. The variations were 11% in the range of 25-100 \({}^{\circ}\)C for the cantilever switches. [PERSON] et al. [108] found that the drift of pull-down voltage increased with temperature, which accelerated switch failure. The drift of pull-down voltage at 40 \({}^{\circ}\)C was 2 V greater than that at 20 \({}^{\circ}\)C. [PERSON] et al. [109] found that pull-down voltage had a strong dependence on temperature. The pull-down voltage varied from 50 V to 77 V in the range of 25-50 \({}^{\circ}\)C. In order to reduce temperature sensitivity and residual stress sensitivity of MEMS switches, many efforts have been made. [PERSON] et al. [110] developed a novel MEM capacitor based on an optimized thermal compensation structure to minimize the reaction forces from anchors because of thermal expansion. The geometrical compensation was a square frame around a square-shaped suspended membrane, \begin{table}
\begin{tabular}{c c c c c} \hline
**Numbers** & **Contact Materials** & **Contact Resistance (f)** & **Lifetime (cycles)** & **Reference** \\ \hline
1 & RuO\({}_{2}\)-Au & 4 & \(1\times 10^{11}\) & [27] \\
2 & Au–Au & 0.1 & \(1.5\times 10^{5}\) & [88] \\
3 & Pt–Pt & 0.4 & \(1.4\times 10^{7}\) & [88] \\
4 & Au–Pt & 0.25 & \(1.6\times 10^{6}\) & [88] \\
5 & Au/(6.3\%)Pt–Au/(6.3\%)Pt & 0.72 & \(6\times 10^{5}\) & [88] \\
6 & Au/(15%)Pt–Au/(15%)Pt & 1.1 & - & [88] \\
7 & Ir–Ir & 0.79 & \(1.3\times 10^{7}\) & [88] \\
8 & Au–Ir & 0.49 & \(1.8\times 10^{6}\) & [88] \\
9 & Au–Au & 1.17 & \(1.02\times 10^{8}\) & [94] \\
10 & Au/(6.3\%)Pt–Au/(6.3\%)Pt & 1.87 & \(2.70\times 10^{8}\) & [94] \\
11 & Au/(7.8\%)Ni–Au/(7.8\%)Ni & 0.62 & - & [101] \\
12 & Au/(16.7\%)Ni–Au/(16.7\%)Ni & 0.88 & - & [101] \\ \hline \end{tabular}
\end{table} 
Table 8: Comparison of some commonly used contact materials. and the anchoring points were placed in the center of each face of the square. Measurement results verified that the pull-down voltage change was less than 5% when the temperature changed in the range of \(-\)30 \({}^{\circ}\)C to +70 \({}^{\circ}\)C. [PERSON] et al. [106] presented a MEMS capacitive switch with a thermal compensation structure using standard thin-film technology. The switch consisted of a suspended square plate with four sides connected to rigid anchors at a confined region; a cutout was defined next to each anchor to prevent direct reaction forces from the rigid anchors to the square plate in the event that the switch was exposed to temperature change. The dielectric layer bottom electrode and the bottom electrode were designed to be symmetrical in order to cause a uniform deformation in the plate. The switch demonstrated 50 mV/\({}^{\circ}\)C variation in the pull-down voltage at 25-125 \({}^{\circ}\)C.  
[PERSON] et al. [111] presented an RF MEMS switched capacitor based on a circularly symmetrical structure with arc-type springs placed between the suspended beam and the anchors, resulting in a pull-down voltage variation of only \(-\)50 mV/\({}^{\circ}\)C from \(-\)5 \({}^{\circ}\)C to 95 \({}^{\circ}\)C, but \(-\)340 mV/\({}^{\circ}\)C for standard rectangular devices. The symmetrical structure also reduced the sensitivity to stress gradients. [PERSON] et al. [112] designed compact single-pole, multiple-throw MEMS switches based on a symmetrical, circular switch topology.