Fabrication And Study Of The RF MEMS Switches

The emerging RF MEMS Switch has been key element in the field of low-oss microwave and mm-wave signal control. MEMS Switches have several advantages over their PIN diode or FET counterpart such as low insertion loss, low power consumption, high isolation, excellent compatibility with silicon and high linearity. Because of those significant advantages mentioned above, RF MEMS switch is more and more under focus lately.In this paper, two kinds of typical RF MEMS switches are analyzed: major working principle and mechanical-electromagnetic model of the capacitive RF MEMS and the DC contact RF MEMS are demonstrated respectively. Based on 1-D lumped model of switch, theoretical formulation of electrostatic actuation voltage of RF MEMS switch is deduced.In this paper, a series capacitive RF MEMS switch has been proposed, and the newly design can avoid the down state capacitance degradation due to the surface roughness preventing intimate contact between beam and dielectric. Moreover a new degree of freedom is introduced to improve on the capacitance ratio by an order of magnitude over the conventional designs. In order to decrease the actuation voltage of RF MEMS switch, the serpentine supports andadditional electrode has been designed. What is more, double Ta₂O₅ /SiN dielectric filmwhich aimed to deposit higher quality dielectric film with higher dielectric breakdown strength and higher dielectric-constant, is used in this paper. Based on comprehensive analysis of microwave characteristic and mechanical characteristic of RF MEMS switch, in this paper, optimal structure, fabrication process and relative parameter have been explored. Design and measurement of two kinds of typical RF MEMS switches are completed. The insertion loss of the designed switches was less than -1dB, and the isolation was measured to be higher than 20dB, in the frequency range from 1 to 10 GHz. Especially the isolation of the series capacitive RF MEMS switch was -42dB at 8GHz.By means of full-wave simulations (HFSS) the effect of metal plate on the series capacitive RF MEMS switch is analyzed and the performance of the cantilever beam RF MEMS switch is simulated, which in theory verifies the result of practical measured results.In order to further make clear of actuation mechanism of switch, in this paper ANSYS is used to simulate the real situation of actuating cantilever beam RF MEMS switch, which again verifies working principle of the actuation of switch.