Yo-Tak Song

Low Actuation Voltage Capacitive Shunt RF-MEMS Switch Having a Corrugated Bridge

This paper presents the design, fabrication and characterization of a low actuation voltage capacitive shunt RF-MEMS switch for microwave and millimeter-wave applications based on a corrugated electrostatic actuated bridge suspended over a concave structure of coplanar waveguide (CPW), with sputtered nickel as the structural material for the bridge and gold for CPW line, fabricated on high-resistivity silicon (HRS) substrate using IC compatible processes for modular integration in a communication devices. The residual stress is very low because having both ends corrugated structure of the bridge in concave structure. The residual stress is calculated about 3-15 MPa in corrugated bridge and 30MPa in flat bridge. The corrugated bridge of the concave structure requires lower actuation voltages 20-80V than 50-100V of the flat bridge of the planar structure in 0.3 to 1.0 μm thick Ni capacitive shunt RF-MEMS switch, in insertion loss 1.0 dB, return loss 12dB, power loss 10 dB and isolation 28 dB from 0.5 up to 40 GHz. The residual stress of the bridge material and structure is critical to lower the actuation voltage.

Development of a Polymer Coating-Based Microlens Array on Isotropically Wet-Etched Quartz Substrates for Maskless Lithography Application

A polymer coating-based microlens array (MLA) was developed on an isotropically wet-etched quartz substrate for maskless photolithography application. The developed MLA showed excellent light focusing ability and uniformity, and a dense fill factor. The obtained focal length ranged from 32.2 to 45.4 µm depending on the curvature of quartz and the thickness of an ultraviolet (UV) adhesive. A small spot size of 1.55 µm and an uniformly focused beam intensity were obtained at the focal plane, confirming that the fabricated MLA has excellent uniformity and good focal ability. The fabricated MLA was applied to UV lithography. Beams were well focused onto a photoresist when UV passed through the MLA. Depending on the variable distance from the MLA, beam size on the photoresist was controlled. Variable micropatterns were realized on the photoresist. Even at high a temperature, the interface between quartz and the UV adhesive was thermally stable and lens performance characteristics remained unchanged.

Microstrip Silicon-MEMS Package for Wafer-Level Chip-Scale Microwave Packaging

A new Micro Electro Mechanical System (MEMS) microstrip package using two high resistivity silicon (HRS) substrates without metal shielding is fabricated for microwave device packaging. The simple package is manufactured using common silicon MEMS technology and the de-embedding measurement shows the small insertion loss (0.3 dB) below 20 GHz and no package resonance. This package also allows the wafer-level chip-scale packaging and is suitable for low cost packaging of various microwave devices.

Spherical and non-spherical high fill-factor microlens arrays fabricated by polymer coating on isotropically etched quartz

Various shapes of microlens arrays (MLAs) were developed by utilizing polymer coating on etched quartz substrates. Spherical and non-spherical plano-concave curvatures were realized via isotropic wet etching of quartz in buffered oxide etchant (BOE), based on diverse design parameters and calculated etching times. The fabricated curvatures showed a high fill-factor and uniform elements in the array. By coating a higher refractive index polymer on the etched quartz, the illuminated light was well focused at the focal plane forming a micronscale light spot array. The experimental focal length was increased from 39.8 to 49.6 μm, as the shape of microlens was flattened. These results well correspond to those obtained from an optical simulation.

Resonance-free HRS MEMS package for microwave and millimeter-wave

A silicon (Si) micro electro mechanical system (MEMS) package using a lightly-doped Si chip carrier for coplanar waveguide (CPW) microwave and millimeter-wave integrated circuits (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 a high resistivity silicon (HRS, 10 k/spl Omega//spl middot/cm) CPW on three types of carriers (conductor-back metal, lightly-doped Si, and HRS) in the frequency range 0.5 to 40 GHz. The proposed MEMS package using the lightly-doped (15 /spl Omega//spl middot/cm) Si chip carrier and the HRS shows low loss and is resonance-free since the lightly-doped Si chip carrier effectively absorbs and suppresses the resonant leakage. The Si MEMS package for CPW MMICs has an insertion loss (S/sub 21/) of 2.0 dB, a reflection loss (S/sub 11/) of 10 dB, and a power loss (PL) of 6.0 dB up to 40 GHz.

Resonance-free Millimeter-wave Coplanar Waveguide Si Microelectromechanical System Package using a Lightly-doped Silicon Chip Carrier

A silicon (Si) microelectromechanical system (MEMS) package using a lightly-doped Si chip carrier for coplanar waveguide (CPW) microwave and millimeter-wave integrated circuits (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 a GaAs CPW on two types of carriers (conductor-back metal and lightly-doped Si) in the frequency range 0.5 to 40 GHz. The proposed MEMS package using the lightly-doped (15 Ωcm) Si chip carrier and the high resistivity silicon (HRS, 15 kΩcm) shows the low loss and resonance-free since the lightly-doped Si chip carrier effectively absorbs and suppresses the resonant leakage. The Si MEMS package for CPW MMICs has an insertion loss (S21) of 2.0 dB, a reflection loss (S11) of 10 dB, and a power loss (PL) of 7.5 dB at 40 GHz.