A Tunable Coplanar Patch Antenna, a Polymer MEMS Based Tunable Bandpass Filter, and a Chip-In-Polymer Packaging Technology

Abstract

This thesis presents a tunable coplanar patch antenna, a Polymer MEMS-based tunable bandpass filter, and a chip-in-polymer packaging technology. First, a Coplanar Waveguide (CPW) based patch antenna is integrated with a prepackaged diode. This diode functions as a variable capacitor (Varactor), which is used to adjust the effective length of the open-end resonator in the Coplanar Patch Antenna (CPA). An increase in the effective length decreases the resonant frequency of the CPA and vice versa. Thus, the resonant frequency of the antenna is tuned by changing the capacitance of the varactor through an applied bias voltage. Second, two Polymer MEMS varactors are integrated with an embedded bandpass filter to yield a tunable filter. In this project, each MEMS varactor is an electro static parallel plate actuator. The capacitance of the parallel plate actuator is varied by controlling the DC voltage applied between the plates. Two MEMS varactors are integrated with the two cascaded LC tank circuits to adjust the resonant frequency of each tank circuit independently and/or simultaneously to realize a tunable bandpass filter. The capacitance is varied by a DC bias voltage that is placed between the plate itself and the center and ground conductors of a CPW segment over which the plate hangs. When this voltage reaches the “pull-down voltage” of the parallel plate actuator, the plate will snap down to contact the dielectric and the capacitance will increase thereby effectively lowering the resonant frequency of the tank circuit as well as the filter’s overall corner frequency. The filter assembly consists of two main layers that are bonded together via a thermal compression bonding film. The lower substrate of the filter assembly consists of a lumped-element filter fabricated using embedded passives technology in Liquid Crystal Polymer (LCP) and the upper part of the filter assembly consists of MEMS varactors. The substrate was fabricated at the Georgia Institute of Technology and the MEMS layer was fabricated in the Alabama Microelectronics Science and Technology Center. Lastly, a “chip-in-polymer” packaging technology is presented that is being developed for the National Aeronautics and Space Administration’s (NASA) Jet Propulsion Laboratories (JPL). This approach is intended to yield two silicon die thinned down to be embedded in a flexible polymer film. In this process, a handle wafer has adhesion promoter spun on around the periphery of the wafer before a layer of PI2611 is spun on. After the initial layer is cured, several other layers, including the thinned die, are spun on and deposited using various methods. Once the device is complete, the handle wafer and the attached devices are diced, however the adhesion in the bulk of the center of the handle wafer between the wafer and the device is such that the device detaches from the handle wafer as desired. Experimental results are presented.