This dissertation presents the theory, design, fabrication, and characterization of the novel low actuation voltage capacitive shunt RF-MEMS switch using a corrugated membrane with self-alignment HRS MEMS packaging for coplanar waveguide (CPW) microwave and millimeter-wave integrated circuits (MMICs) applications. Analytical analyses and experimental results have been carried out to derive algebraic expressions for the actuation mechanism of corrugated membrane for a low residual stress. It is shown that the residual stress of both types of corrugated and flat membranes can be modeled with the help of a mechanics theory. The residual stress in corrugated membranes is calculated using a geometrical model, confirmed by the finite element method (FEM) analysis and measured by the experimental results.
The corrugated electrostatic actuated bridge is suspended over a concave structure of CPW, with sputtered nickel (Ni) as the structural material for the bridge and gold for CPW line, fabricated on a high-resistivity silicon (HRS, 4~15 kΩ•cm) substrate. The corrugated switch on the concave structure requires lower actuation voltage than the flat switch on the planar structure in various thickness Ni RF-MEMS switch. The residual stress is very low by corrugating both ends of the bridge on the concave structure. The residual stress of the bridge material and structure is critical to lower the actuation voltage.
HRS MEMS package using a lightly-doped silicon (Si) chip carrier for CPW MMICs is proposed in order to reduce parasitic problems of leakage, coupling, and resonance. The proposed chip carrier scheme is verified by fabricating and measuring the package with a GaAs or a HRS CPW on three types of carriers (conductor-backed metal, lightly-doped Si, and HRS) in the frequency range from 0.5 to 40 GHz. The proposed HRS MEMS package using the lightly-doped (15 Ω•cm) Si chip carrier shows the low loss and no parasitic leakage resonance since the lightly-doped Si chip carrier effectively absorbs and suppresses the parasitic leakage resonance.
In this dissertation, the optimized actuation voltage is 30-50 V, the residual stress is 5-9 MPa, the spring constant is 4-12 N/m at the bridge thickness 0.5-0.7 µm and finally, the switching time is 6-9 µs.
The Self-alignment HRS MEMS package of the RF-MEMS switch with a 15 Ω•cm lightly-doped Si chip carrier also shows no parasitic leakage resonances and is verified as an effective packaging solution for the low cost and high performance coplanar MMICs. Therefore, this dissertation presents research results of the low actuation voltage capacitive shunt RF-MEMS switch using a corrugated membrane with self-alignment HRS MEMS packaging for the low cost and high performance CPW MMICs applications.
