Thesis (Ph. D.)--Washington State University. / Includes bibliographical references.

As the demand for portable electronic devices increase, the need to replace off-chip discrete devices with on-chip devices is imperative. Inductors are one such passive device that is widely used in low noise amplifiers, oscillators, etc. Current on-chip spiral inductors suffer from large parasitics and area for a meager value of inductance and quality factor. The need to overcome these issues has led to the development inductors with new geometries housing magnetic cores that show an enhanced inductance compared to the air core coil. In this thesis, we discuss the design of a three-dimensional spiral inductor with a Co-Fe nanoparticle core that will be fabricated as per the process rules set by VT MT SPL. The changes in the value of the inductance, resistance, quality factor and parasitics are studied for varying number of turns of the coil, thickness of the coil, spacing between turns and different materials used as the coil. An optimum design incorporating the least parasitics and reasonable inductance is proposed. / Master of Science

MEMS gyroscopes are electromechanical devices that measure rate or angle of rotation. They are one of the fastest growing segments of the microsensor market. Advances in microfabrication technologies have enabled the implementation of chip scale monolithic gyroscopes (MEMS gyroscopes) with very small form factor that are lightweight and consume little power. Over the past decade, significant amount of research have been directed towards the development of high performance and very small size MEMS gyroscopes for applications in consumer electronics such as smart phones. In this dissertation, high aspect-ratio hemispherical shell structure with continuously curved surface is utilized as the high Q resonator. Being an axial symmetric structure, the 3D hemispherical shell is able to achieve low frequency (3 ~ 5 kHz) within 2 mm X 2mm die area. Detailed analysis on energy dissipation also shows its potential to achieve ultra-high quality factor with the selection of high Q material and proper design of support structure. This dissertation presents, for the first time, the analysis, design, fabrication and characterization of a micro-hemispherical resonating gyroscope (μHRG) that has the potential to be used as a whole angle micro-gyroscope. A three-dimensional high aspect-ratio poly- and single crystalline silicon (3D HARPSS) process is developed to fabricate free-standing, stem-supported hemispherical shell with self-aligned deep electrodes for driving, sensing and quadrature control of the gyroscope. This monolithic process consists of seven lithography steps and combines 3D micro-structure with curved surfaces with the HARPSS process to create capacitive electrodes with arbitrary gaps around the micro-hemispherical shell resonator (μHSR). Polysilicon is utilized as the structural material due to its isotropic mechanical properties and the potential of achieving high quality factor. The fabrication is demonstrated successfully by prototypes of polysilicon μHRG with diameter of 1.2 mm and thickness of 700 nm. Frequency response and gyro operation are electronically measured using the integrated electrodes. Quality factor of 8,500 is measured with frequency mismatch of 105 Hz. Electronic mode matching and alignment are successfully performed by applying tuning voltages and quadrature nulling voltages. An open loop rate sensitivity scale factor of 4.42 mV/°/s was measured. Design and process optimization of the support structure improved the quality factor to 40,000. Further improvement of quality factor will enable the demonstration of high performance RIG using polysilicon μHRG.

No / An efficient way to test for potential unsymmetrical nonlinear responses in biological tissue samples exposed to a microwave signal is to observe the second harmonic in a cavity resonant at the two frequencies, with collocated antinodes. Such a response would be of interest as being a mechanism that could enable demodulation of information-carrying waveforms. In this work, an electric circuit model is proposed to facilitate calibration of any putative nonlinear RF energy conversion inside a high quality-factor resonant cavity with a known nonlinear loading device. The first and second harmonic responses of the cavity due to loading with the nonlinear and lossy material are also demonstrated. The results from the proposed mathematical model give a good indication of the input power required to detect any very weak second harmonic signal in relation to the sensitivity of the measurement equipment. Hence, this proposed mathematical model will assist in determining the level of the second harmonic signal in the detector as a function of the specific input power applied. / EPSRC

Micromechanical resonators are used in a variety of sensing and filtering applications. In these applications, the accurate performance of micro resonators depends on the sensitivity of these devices to a particular resonance frequency. This sensitivity is measured using the quality factor Q, which is the ratio of the total input energy into the device to the energy dissipated within a vibration cycle. A higher quality factor indicates a smaller resonance bandwidth, which makes the micro-resonator more effective in identifying a desired signal. Higher Q values result from reductions in dissipation losses. Dissipation losses occur through damping by the ambient fluid, anchor losses, thermoelastic damping, and other sources. The squeeze-film effect is of particular interest in micro-resonators as the fluid enclosed between the resonating components can provide significant dissipation. This work covers investigations into the air damping of oscillating micromachined resonators that operate near a fixed wall, which is parallel to the oscillating surface. The main portion of this work focuses on the theoretical and numerical investigation of the air damping of micromachined resonators when the surrounding gas (air) is in the Free-Molecule regime. Errors and limitations of previous theoretical models have been found and corrected. A molecular dynamics simulation code that is suitable to handle a more general class of resonators has been developed. This code has been used to find the quality factor of a microbeam resonator. The results from the code were compared to existing experimental results, and were found to have very good agreement in the free molecular regime. The simulation was then used to investigate the effects of the oscillation mechanics on the energy dissipation and quality factor. The second part of this work focuses on the region between the bottom surface of a laterally-oscillating disk resonator and the substrate. The compressibility effects of a 1 micron thick film of air on a laterally-oscillating disk resonator were investigated. The pressure perturbation for this case was found to be minimal, which means that the compressibility effects of the fluid film will negligible.

The 1/4£f dual-mode resonators made from c-axis-oriented aluminum nitride films grown on different conduction material have been studied in this thesis. The RF/DC sputter system is used to grow on layers of reflector. During the porcess, 3.5 pairs of Bragg reflector alternating with W and SiO2 are composed by Si substractor. To achieve 0.999 reflective rate, fabrication parameters are adjusted to make W films become £\-phase structurre. On the other hand, piezoelectric layers as well as reflective layers that using reactive RF magnetron sputtering system and means of off-axis are combined to deposite optimal resonators of shear mode quality factor (Q) resonatros. While changing the substract and target distance between various bottom electrode materials, including Si, W/Si, and Mo/Si could deposit AlN with various c-axis tilting angle which resulted in stimulating longitudinal and shear acoustic waves. Futhermore, the finding is used to discuss the growth mechanism of inclined AlN by TEM. The analysis of various distances of AlN films shows that column inclining angle and XRD-Rocking Curve £s will increase with distance. The quality of shear mode would be better when column and £s are highly shifed. About the influence on AlN deposites, AlN/Si was grown away from the center by 6 cm. AlN/Si column inclining angle is about 20 degree, and RMS could reach 2.63nm beneath. Uner AlN/W/Si, column incling angle is about 30 degree, and £s shift angle 4.14 degree, the shear mode quality factor of freaquency response is obtained to 262. Under AlN/Mo/W/Si, column incling angle would be 25.4 degree, and XRD are better-choosed c-aixsm, £s tilting angle shifs 6.72 degree, and the shear mode quality factor is obtained to 290. Film intersurface appears bigger misfit by TEM to obtain better shear mode.

Improving the quality factor of the mechanical oscillations of micron scale beams in a viscous fluid, such as water, is an open challenge of direct relevance to the development of future technologies. We study the stochastic dynamics of doubly-clamped micron scale beams in a viscous fluid driven by Brownian motion. We use a thermodynamic approach to compute the equilibrium fluctuations in beam displacement that requires only deterministic calculations. From calculations of the autocorrelations and noise spectra we quantify the beam dynamics by the quality factor and resonant frequency of the fundamental flexural mode over a range of experimentally accessible geometries. We carefully study the effects of the grid resolution, domain size, linear response, and time-step for the numerical simulations. We consider beams with uniform rectangular cross-section and explore the increased quality factor and resonant frequency as a baseline geometry is varied by increasing the width, increasing the thickness, and decreasing the length. The quality factor is nearly doubled by tripling either the width or the height of the beam. Much larger improvements are found by decreasing the beam length, however this is limited by the appearance of additional modes of dissipation. Overall, the stochastic dynamics of the wider and thicker beams are well predicted by a two-dimensional approximate theory beyond what may be expected based upon the underlying assumptions, whereas the shorter beams require a more detailed analysis. / Master of Science

MEMS (Microelectromechanical Systems) acoustic sensors are a promising platform for Point-of-Care biosensing. In particular, piezoelectrically driven acoustic sensors can provide fast results with high sensitivity, can be miniaturized and mass produced, and have the potential to be fully integrated with sample handling and electronics in handheld devices. Furthermore, they can be designed as multiplexed arrays to detect multiple biomarkers of interest in parallel. In order to develop a microfabricated biosensing platform, a specific and high affinity biodetection platform must be optimized, and the microfabricated sensors must be designed to have high sensitivity and maintain good performance in a liquid environment. A biomolecular sensing system that uses high affinity peptide aptamers and a passivation layer has been optimized for the detection of proteins of interest using the quartz crystal microbalance with dissipation monitoring (QCM-D). The resulting system is highly specific to target proteins, differentiating between target IgG molecules and other closely related IgG subclasses, even in complex environments such as serum. Piezoelectrically actuated MEMS resonators are designed to operate in flexural microplate modes, with several modes shown to be ideally suited for fluid based biosensing due to improved performance in the liquid environment. The increase in quality factor of these MEMS microplate devices in liquid, as compared to air, is further investigated through the analytical and finite element modeling of MEMS fluid damping mechanisms, with a focus on acoustic radiation losses for circular microplate devices. It is found that the impedance mismatch at the air-water interface of a droplet is a key contributor to reduced acoustic radiation losses and thus improved device performance in water. Microplate acoustic sensors operating in flexural plate wave and microplate flexural modes are then integrated with a fluidic cell to facilitate protein sensing from fluid samples. Flexural plate wave devices are used to measure protein mass adsorbed to the sensor surface and initial results toward microplate flexural mode protein sensing are presented. Finally, challenges and areas of future research are discussed to outline the path towards finalization of a sensing platform taking advantage of the combination of the sensitive MEMS acoustic sensor capable of operating in a liquid environment and the specific and high affinity biomolecular detection system. Together, these form the potential basis of a novel Point-of-Care platform for simple and rapid monitoring of protein levels in complex samples.

Modern communication systems require high performance radio frequency (RF) and microwave circuits and devices. This is becoming increasingly challenging to realize in the content of cost/size constraints. Integrated circuits (ICs) satisfy the cost/size requirement, but performance is often sacri¯ced. For instance, high quality factor (Q factor) passive components are difficult to achieve in standard silicon-based IC processes.<p>In recent years, microelectromechanical systems (MEMS) devices have been receiving increasing attention as a possible replacement for various on-chip passive elements, offering potential improvement in performance while maintaining high levels of integration. Variable capacitors (varactor) are common elements used in various applications. One of the MEMS variable capacitors that has been recently developed is built using deep X-ray lithography (as part of the LIGA process). This type of capacitor exhibits high quality factor at microwave frequencies.<p>The complementary metal oxide semiconductor (CMOS) technology dominates the silicon IC process. CMOS becomes increasingly popular for RF applications due to its advantages in level of integration, cost and power consumption. This research demonstrates a CMOS voltage-controlled oscillator (VCO) design which is used to investigate methods, advantages and problems in integrating LIGA-MEMS devices to CMOS RF circuits, and to evaluate the performance of the LIGA-MEMS variable capacitor in comparison with the conventional on-chip CMOS varactor. The VCO was designed and fabricated using TSMC 0.18 micron CMOS technology. The core of the VCO, including transistors, resistors, and on-chip inductors was designed to connect to either an on-chip CMOS varactor or an off-chip LIGA-MEMS capacitor to oscillate between 2.6 GHz and 2.7 GHz. Oscillator phase noise analysis is used to compare the performance between the two capacitors. The fabricated VCO occupied an area of 1 mm^2.<p>This initial attempt at VCO fabrication did not produce a functional VCO, so the performance of the capacitors with the fabricated VCO could not be tested. However, the simulation results show that with this LIGA-MEMS capacitor, a 6.4 dB of phase noise improvement at 300 kHz offset from the carrier is possible in a CMOS-based VCO design.

Modern communication systems require high performance radio frequency (RF) and microwave circuits and devices. This is becoming increasingly challenging to realize in the content of cost/size constraints. Integrated circuits (ICs) satisfy the cost/size requirement, but performance is often sacri¯ced. For instance, high quality factor (Q factor) passive components are difficult to achieve in standard silicon-based IC processes.<p>In recent years, microelectromechanical systems (MEMS) devices have been receiving increasing attention as a possible replacement for various on-chip passive elements, offering potential improvement in performance while maintaining high levels of integration. Variable capacitors (varactor) are common elements used in various applications. One of the MEMS variable capacitors that has been recently developed is built using deep X-ray lithography (as part of the LIGA process). This type of capacitor exhibits high quality factor at microwave frequencies.<p>The complementary metal oxide semiconductor (CMOS) technology dominates the silicon IC process. CMOS becomes increasingly popular for RF applications due to its advantages in level of integration, cost and power consumption. This research demonstrates a CMOS voltage-controlled oscillator (VCO) design which is used to investigate methods, advantages and problems in integrating LIGA-MEMS devices to CMOS RF circuits, and to evaluate the performance of the LIGA-MEMS variable capacitor in comparison with the conventional on-chip CMOS varactor. The VCO was designed and fabricated using TSMC 0.18 micron CMOS technology. The core of the VCO, including transistors, resistors, and on-chip inductors was designed to connect to either an on-chip CMOS varactor or an off-chip LIGA-MEMS capacitor to oscillate between 2.6 GHz and 2.7 GHz. Oscillator phase noise analysis is used to compare the performance between the two capacitors. The fabricated VCO occupied an area of 1 mm^2.<p>This initial attempt at VCO fabrication did not produce a functional VCO, so the performance of the capacitors with the fabricated VCO could not be tested. However, the simulation results show that with this LIGA-MEMS capacitor, a 6.4 dB of phase noise improvement at 300 kHz offset from the carrier is possible in a CMOS-based VCO design.