Miniature microphones have numerous applications but often exhibit poor performance which can be attributed to the challenges associated with capacitive detection at small size scales. Optical detection methods are able to overcome some of these challenges although miniaturized integration of these optical systems has not yet been demonstrated. An optical interferometric detection scheme is presented and is implemented using micro-scale optoelectronic devices which are used primarily in fiber optic data transmission. Using basic diffraction theory, a model is developed and used to optimize the micro-optical system within a 1mm3 volume. Both omnidirectional and directional optical microphone designs are presented and a modular packaging architecture is assembled in order to test these devices. Results from the 2mm diameter omnidirectional optical microphone structure demonstrate a 26dBA noise floor. The biomimetic directional optical microphone, which has an equivalent port spacing of 1mm, demonstrates a noise floor of 34dBA. Additionally, these results demonstrate an array of two biomimetic directional optical microphones located on the same silicon chip and separated by less than 5mm. These results confirm the micro-optical detection method as an alternative to capacitive detection especially for miniaturized microphone applications and suggest that this method in its modular packaging architecture is competitive with industry leading measurement microphones.

Planar £gPEM Fuel Cell Stacks are designed and fabricated in-house through a deep UV lithography technique, with SU 8 photoresist used as the microstructure mold for the fuel cell flow channel or bipolar plates when micro electroforming. The fuel cell stacks use a new design which means installing the fuel channel into PMMA, by which the fuel supply channel becomes convenient and simplified. The performance of the stack is measured in different inlets, and the effect of the hydrogen inlets is explained. The experimental results are presented in the form of polarization VI curves and PI curves for the different types of inlet. Furthermore, the influence of the inlets is presented and discussed.

In order to apply to S-Band (1-4.5 GHz) of wireless communication system, we designed and fabricated a high-insolating RF-MEMS switch by surface micromachining technology in this study. In terms of the micro switch, we performed the structural design, high frequency simulation, components process integration and high-frequency measurement in this study. Especially for making components be high-isolation, low-loss and low-driving voltage, we proposed the following three methods: (i) adjusting the space and width of the transmission lines to improve the RF performance; (ii) applying the stress imbalance, by using dual metal composite top electrode, to form a arched contact electrode and reduce the drive voltage efficiently; (iii) using non-isometric spring structure to stabilize the electrode movement of the components. Besides, we did the optimizing simulation for this study, which were supported by Ansoft-HFSS and ADS, in terms of the micro switch which has different structural design as mentioned above. The size of the optimized RF micro-switch which we developed for this study is only 145 £gm ¡Ñ 205 £gm. Switched from on-state to off-state, the component needs 36.5V drive voltage only. According to the result of the commercial network analyzer in 1-4.5GHz frequency range, the isolation rate of the components reaches -59.721dB while off-state; the insert los reaches -1.625dB while on-state.

Balun is a key component in radio frequency (RF) circuits. The conventional Si-based planar spiral balun presented a high insertion loss. To solve this problem, this thesis firstly develops a Si-based suspending spiral balun using electrochemical deposition and surface micromachining technology for the fourth generation of wireless communication system. To reduce the power dissipation of the conventional Si-based planar spiral balun, thesis utilized a suspending structure to reduce the power loss through the substrate and dielectric layer. The fabricated suspending spiral balun are constructed by three bottom GSG electrodes, thirty three supporting copper vias and a suspending spiral copper conducting layer. The main fabrication processes in this research including: (1) four thin-film deposition processes, (2) four photolithography processes, (3) two etching processes and (4) two copper electroplating processes. In addition, this thesis used the commercial software (Ansoft HFSS) to analysis the high frequency characteristic of Si-based suspending spiral balun. The finished Si-based suspending spiral balun were measured by a commercial network analyzer under 2~8 GHz testing frequency range. Based on the measurement results, the value of insertion loss is 1.26 dB at 5.2 GHz, magnitude imbalanced is lower than 0.86 dB, phase imbalanced is less than 3.4 degree and CMRR is more than 30 dB. Finally, this thesis successfully develops a Si-based suspending spiral balun using MEMS technology for the fourth generation wireless communication system.

A novel process which does not require the traditional Chemical Vapor Deposition (CVD) synthesis techniques and which works at temperatures lower than the conventional techniques was developed for synthesis of carbon nanotubes (CNT). The substrates used for this study involved MEMS (Micro Electrical Mechanical Systems) elements and passive elements. These were coated with Fullerene using Physical Vapor Deposition or through a solution in an organic solvent. Catalyst precursors were deposited on these Fullerene coated substrates using “wet processes”. These substrates were then heated using either the integrated microheaters or external heaters in an inert atmosphere to obtain CNT. Thus, in this process we tried to obviate the Chemical Vapor Deposition (CVD) process for synthesis of CNT (SWCNT and MWCNT). The synthesized CNT will be characterized using Scanning Electron Microscopy and Raman spectroscopy techniques. Also, conductivity measurements were carried out for the synthesized tubes using Dry (contact based) and Wet (electro-chemical) methods. This work also proves the concept for the feasibility for a portable hand held instrument for synthesis of CNT with tunable “on demand” chirality.

In the field of MEMS technology, all kinds of actuators are often regarded as the force source. However, some designs of actuators have good precision in position; the working distance to be driven is too short. Therefore, the actuator is often combined with a mechanism with displacement amplify function. The objective of this study is to synthesize the new pantograph mechanism using the concept of mechanism design according to the desirable motion and the requirement of the actuator. The cases of single degree-of-freedom and two degree-of-freedom are assumed simultaneously for the output of the basic design constraints so as to generate new pantograph mechanisms from the catalogue of kinematic chains. The suitable pantographs are then found out with the features such as: (1) single level plane using comb driver, (2) using compliant mechanisms as joints, and (3) suitable for MUMPs process. These constraints of design are considered as the procedures of process design, compliant mechanisms transformation, compliant joints design, actuator configurations design, FEM dynamic analysis and joint modifications. Finally, prototypes are evaluated and transform into planar micro compliant pantographs. Moreover, a test and a discussion of the displacement error are done under the consideration of the designed mechanism actuating using FEM analysis. The percentage of displacement error of planar micro compliant pantograph is defined, and the equation for estimating the percentage of displacement error is proposed so as to modify the motion error for controlling.

This paper aims to design a high-quality-factor suspending micro-inductor and to establish its equivalent circuit model for performance optimization. Two commercial software (Ansoft HFSS and Agilent ADS) are adopts to analysis the influences of quality factor on the geometric parameters and substrate materials. The designed micro-inductors are constructed by one bottom GSG electrode, two supporting copper vias and a spiral suspending copper conducting layer. As the simulated results of this research, the quality factor of the suspending micro-inductor is increased with the height of air gap, the thickness and width of suspending copper conducting layer and decrease with the number of turns, line space and outer diameter of suspending copper conducting layer. The influences of different shapes of the spiral suspending copper conducting layers on the quality factor of micro-inductors were also investigated. The simulation results well match to the theoretical prediction. Finally, this thesis has successfully derived two experiential formulas based on the analysis results to estimate quickly the inductance of the suspending micro-inductors with circular and square shape. Compared with the simulation results and realistic measurement results, these experiential formulas demonstrate 94-95% and 90% accuracies respectively.

Capacitive radio frequency (RF) micro-electromechanical (MEMS) switches are among the most promising applications in MEMS systems. They have been introduced in the last 15-20 years as a practical alternative over traditional semiconductor switches. Low-cost RF MEMS switches are prime candidates for replacing the conventional GaAs Field Effect Transistors (FET) and pin diode switches in RF and microwave communication systems, mainly due to their low insertion loss, good isolation, linear characteristic and low power consumption. Unfortunately, their commercialization is currently hindered by reliability problems. The most important problem is charging of the dielectric, causing unpredictable device behavior. The charging of the dielectric has been found to be a complicated process and is currently under intense research. Developing a good analytical model that would describe accumulating of charges in the dielectric and their influence on the device behavior would be the main step to achieving more reliable switches. This work intends to theoretically and experimentally investigate the dielectric charging effects of capacitive RF MEMS switches with silicon nitride and silicon dioxide as the dielectric layer. For the silicon nitride study, both MEMS switches and MIM capacitors were fabricated, and their charging behaviors were analyzed and compared. Several different dielectric stoichiometries, deposition temperatures, and thicknesses were examined in order to understand the effects of each parameter on the charging mechanisms of the dielectric. The goal was to determine the most favorable deposition conditions to induce minimum dielectric charging in silicon nitride capacitive switches. The switches were measured over a wide temperature range and the temperaturedependent behavior of the dielectric was examined to characterize and study its charging behaviors. For the silicon dioxide MEMS switches, several different actuation mechanisms were systematically analyzed, and their effects on the dielectric charging of the switches were studied. A general model of distributed charge and air gap was adopted and further developed to better explain the charging behavior of MEMS switches. The goal was to provide a deeper insight into the trapping processes in dielectric materials and their corresponding time constants. This will in turn aid in better modeling of charging processes in capacitive RF MEMS switches.

Atomic force microscope (AFM) is an invaluable tool for measurement of pico-Newton to nano-Newton levels of interaction forces in liquid. As such, it is widely used to measure single-molecular interaction forces through dynamic force spectroscopy. In this technique, the interaction force spectra between a specimen on the sharp tip of the cantilever and another specimen on the substrate is measured by repeatedly moving the cantilever in and out of contact with the substrate. By varying the loading rate and measuring the bond rupture force or bond lifetime give researchers information about the strength and dissociation rates of non-covalent bonds, which in turn determines the energy barriers to overcome. Commercially available cantilevers can resolve interaction forces as low as 5 pN with 1 kHz bandwidth in fluid. This resolution can be improved to 1 pN by using smaller cantilevers at the expense of microfabrication constraints and sophisticated detection systems. The pulling speed of the cantilever, which determines the loading rate of the bonds, is limited to the point where the hydrodynamic drag force becomes comparable to the level of the molecular interaction force. This level is around 10 um/s for most cantilevers while higher pulling speeds are required for complete understanding of force spectra. Thus, novel actuators that allow higher loading rates with minimal hydrodynamic drag forces on the cantilevers, and fast, sensitive force sensors with simple detection systems are highly desirable. This dissertation presents the research efforts for the development of membrane-based active probe structures with electrostatic actuation and integrated diffraction-based optical interferometric force detection for single-molecular force measurements. Design, microfabrication and characterization of the probes are explained in detail. A setup including optics and electronics for experimental characterization and biological experiments with the probes membranes is also presented. Finally, biological experiments are included in this dissertation. The "active" nature of the probe is because of the integrated, parallel-plate type electrostatic actuator. The actuation range of the membrane is controlled with the gap height between the membrane and the substrate. Within this range it is possible to actuate the membrane fast, with a speed limited by the membrane dynamics with negligible hydrodynamic drag. Actuating these membrane probes and using a cantilever coupled to the membrane, fast pulling experiments with an order of magnitude faster than achieved by regular AFM systems are demonstrated. The displacement noise spectral density for the probe was measured to be below 10 fm/rtHz for frequencies as low as 3 Hz with differential readout scheme. This noise floor provides a force sensitivity of 0.3 - 3 pN with 1 kHz bandwidth using membranes with spring constants of 1 - 10 N/m. This low inherent noise has a potential to probe wide range of biomolecules. The probes have been demonstrated for fast-pulling and high-resolution force sensing. Feasibility for high throughput parallel operation has been explored. Unique capabilities of the probes such as electrostatic spring constant tuning and thermal drift cancellation in AFM are also presented in this dissertation.

Air-gap structures are of particular interest for packaging of microelectromechanical systems (MEMS). In this work, an overcoat material is used to cover a sacrificial polymer, which protects the MEMS device during packaging. Once the overcoat is in place, the sacrificial polymer is thermally decomposed freeing the MEMS structure while the overcoat dielectric provides mechanical protection from the environment. An epoxy POSS dielectric was used as a high-selectivity etch mask for the PPC and a rigid overcoat for the structure leading to the process improvements. The packaging structures can be designed for a range of MEMS device sizes and operating environments. However, the air-cavity structures need additional rigidity to withstand chip-level packaging conditions. Metalized air cavity packages were molded under traditional lead frame molding pressures and tested for mechanical integrity. The experimental molding tests and mechanical models were used to establish processing conditions and physical designs for the cavities as a function of cavity size. A semi-hermetic package was created using an in-situ sacrificial decomposition/epoxy cure molding step for creating large cavity chip packages. Through the optimization of the air cavity, new materials and processes were tested for general microfabrication. The epoxy POSS dielectric provides a resilient, strong inorganic/organic hybrid dielectric for use in microfabrication and packaging applications. Polycarbonates can be used for low cost temporary adhesives in wafer-wafer bonding. An improved electroless deposition process for silver and copper was developed. The Sn/Pd activation was replaced by a cost efficient Sn/Ag catalyst. The process was shown to be able to deposit adherent copper on smooth POSS and silicon dioxide surfaces. Electroless copper was demonstrated on untreated silicon oxide wafers for TSV sidewall deposition.