Novel applications of SU-8 and ALD materials in fabrication of micro- and nano-scale devices

This work explores further miniaturization of liquid lenses using electrowetting on dielectric (EWOD) technology and micro-/nano-eletro-mechanical resonators and switches by surface micro- and nano-machining techniques. Two types of materials, SU-8 and atomic layer deposited materials, are studied. SU-8 forms the main structure of variable focus liquid microlenses. ALD alumina and ALD tungsten are the main structural materials for micro-scale resonator and nano-scale electrical switches, respectively.;Micro-scale variable focus lenses are used in a broad range of applications, such as cameras in cell phones, bio-optical systems, and optical communications. The liquid lenses using EWOD technology provide a promising future for these applications. However, further miniaturization of these lenses is desired for micro-systems. A micro-scale SU-8 cavity with a slanted sidewall provides the desired shape for the microlenses and is achieved by ultraviolet overexposure. The novel fabrication process and the demonstration of a working lens are presented. The combination of SU-8 and EWOD technology provides a novel method for further miniaturization of these liquid lenses and expands their applications.;The integration of nano-scale electro-mechanical resonators and switches with CMOS circuits has attracted researchers' attention recently. A high quality material with a low deposition temperature is desired. The materials using atomic layer deposition (ALD) possess the potential to achieve the integration. This work explores two ALD materials as structural materials for micro-resonators and nano-switches. ALD alumina, of nanometer thicknesses in scale, forms a pinned-pinned micro-bridge as a resonator, while the bridge is actuated by electrostatic forces with a thin chromium layer on top. A setup with a scanning electron microscope (SEM) measures the resonant frequency as well as the quality factor. ALD-based resonators with Q > 39000 are measured. The residual stress of 258 MPa inside the structure is characterized by the resonant frequency measurements as well. Another ALD material, tungsten, forms the structure of electrostatically actuated nano-scale switches for nano-electronics. Two types of structures, cantilevers and bridges, demonstrate successful two-terminal nanoswitches. A 4 mum long ALD W bridge achieves an actuation voltage of 3.5 Volts while a 1.3 mum long ALD W cantilever achieves a footprint of 0.91 mum2.