No description available.

In this thesis, the development of a novel electro-thermally actuated bi-stable out-of-plane two way actuated buckled micro-bridge for a potential application in optical switching is presented. The actuator consists of a bridge supported by 'legs' and springs at its four corners. The springs and the bridge are made of a tri-layer structure comprising of 2.5??m thick low-stress PECVD oxide, 1??m thick high-stress PECVD oxide and 2??m thick heavily phosphorus doped silicon. The legs, on the other hand, are 2??m thick single layer heavily phosphorus doped silicon. Both legs and springs provide elastically constrained boundary conditions at the supporting ends, without of which important features of the micro-bridge actuator could not have been achieved. This microbridge actuator is designed, simulated using ANSYS, fabricated and tested. The results from the testing have shown a good agreement with analytical prediction and ANSYS simulation. The actuator demonstrated bi-stability, two-way actuation and 31??m out-of-plane movement between the two-states using low voltage drive. Buckled shape model, design method for bi-stability and thermo-mechanical model are developed and employed in the design of the micro-bridge. These models are compared with Finite Element (FE) based ANSYS simulation and measurements from the fabricated micro-bridge and have shown a good agreement. In order to demonstrate the potential application of this actuator to optical switching, ANSYS simulation studies have been performed on a micro-mirror integrated with the micro-bridge actuator. From these studies, the optimum micro-mirror size that is appropriate for the integration has been obtained. This optimal mirror size ensures the important features of the actuator. Mirror fabrication experiments in (110) wafer have been carried out to find out the appropriate compensation mask size for a given etch depth and the suitable wafer thickness that can be used to fabricate the integrated system.

Powder injection molding (PIM) is a net fabrication technique that combines the complex shape-forming ability of plastic injection molding, the precision of die-casting, and the material selection flexibility of powder metallurgy. For this study, the design issues related to PIM for fabrication of thin-walled high-aspect ratio geometries were investigated. These types of geometries are typical to the field of microtechnology-based energy and chemical systems (MECS). MECS are multi-scale (sizes in at least two or more different length scale regimes) fluidic devices working on the principle of heat and mass transfer through embedded micro and nanoscale features. Stainless steel was the material chosen for the investigations because of its high-thermal resistance and chemical inertness necessary for typical microfluidic applications. The investigations for the study were performed using the state-of-the-art computer aided engineering (CAE) design tool, PIMSolver��. The effect of reducing part thickness, on the process parameters including melt temperature, mold temperature, fill time and switch over position, during the mold-filling stage of the injection molding cycle were investigated. The design of experiments was conducted using the Taguchi method. It was seen that the process variability generally increased with reduction in thickness. Mold temperature played the most significant role in controlling the mold filling behavior as the part thickness reduced. The effects of reducing part thickness, process parameters, microscale surface geometry and delivery system design on the occurrence of defects like short shots were also studied. The operating range, in which the mold cavity was completely filled, was greatly reduced as the part thickness was reduced. The single edge gated delivery system designs, with single or branched runners, resulted in a completely formed part. The presence of microchannel features on the part surface increased the possibility of formation of defects like short shots and weld-lines when compared to a featureless part. The study explored some typical micro-fluidic geometries for fabrication using PIM. The final aspect of this study was the PIM experiments performed using a commercial stainless steel feedstock. Experiments were performed to study the mold-filling behavior of a thin, high aspect ratio part and also to study the effect of varying processing conditions on the mold-filling behavior. These experiments also provided correspondence to the mold filling behavior simulated using PIMSolver��. The PIMSolver�� closely predicted the mold-filling patterns as seen in the experiments performed under similar molding conditions. The study was successful in laying down a quantitative framework for using PIM to fabricate micro-fluidic devices. / Graduation date: 2005

This research contributes to worldwide efforts to miniaturize one of the most powerful and versatile analytical tools, gas chromatography (GC). If a rapid, sensitive and selective hand-held GC system is realized, it would have a wide range of applications in many industries and research areas. As a part of developing a hand-held GC system, this research focuses on the separation column, which is the most important component of a GC system. This thesis describes the development of a miniature separation column that has low thermal mass and an embedded heating element for rapid thermal cycling. The worlds first thin polymer film (parylene) GC column has been successfully developed. This thesis includes: first, a study of theoretical column performance of rectangular GC column; second, the design optimization of parylene column and embedded heating element; third, the development of new processes such as parylene micromolding and stationary phase coating technique for parylene column; fourth, the fabrication of parylene GC column with an embedded heating element; and lastly, the testing and evaluation of parylene GC column through GC analysis.

This thesis reports on the design and fabrication of micro-electro-mechanical (MEM) resonators on silicon that are piezoelectrically-transduced for operation in the very high frequency (VHF) range. These devices have a block-type or beam-type design, and are designed to resonate in their in-plane and out-of-plane bulk extensional modes. Two piezoelectric materials were taken into consideration, zinc-oxide (ZnO) and lead-zirconate-titanate (PZT). The resonators are fabricated on silicon-on-insulator (SOI) wafers and the metal/piezo/metal stack of layers forming the device is built and patterned on the device layer silicon via photolithography techniques, RF sputtering (for the piezo-layer) and electron-beam evaporation (for the metal layers). The designing aspect involved ANSYS simulations of the mode-shapes and estimation of frequencies, and these have correlated well with experimental results. Devices with RF sputtered ZnO were successfully fabricated and tested to give high quality factors at reasonably high frequencies. A gold ground plane was implemented to reduce the feed-through level and increase the signal-to-noise ratio. Extensive characterization of PZT was also done as a replacement for ZnO, as the former material has a much higher piezoelectric coefficient (~20X that of ZnO) and can therefore extend the operation of these MEM resonators into the UHF range. Although the basic design of the device remains the same, incorporation of PZT complicates the process flow considerably with respect to the chemistry now involved with the patterning of different layers. The frequency response for ZnO-based resonators as well as all the characterization data for PZT has been reported.

As technology shrinks new types of defects are being discovered and new fault models are being created for those defects. Transition delay and path delay fault models are two such models that have been created, but they still fall short in that they are unable to obtain a high test coverage of smaller delay defects; these defects can cause functional behavior to fail and also indicate potential reliability issues. The first part of this dissertation addresses these problems by presenting an enhanced timing-based delay fault testing technique that incorporates the use of standard delay ATPG, along with timing information gathered from standard static timing analysis. Utilizing delay fault patterns typically increases the test data volume by 3-5X when compared to stuck-at patterns. Combined with the increase in test data volume associated with the increase in gate count that typically accompanies the miniaturization of technology, this adds up to a very large increase in test data volume that directly affect test time and thus the manufacturing cost. The second part of this dissertation presents a technique for improving test compression and reducing test data volume by using multiple expansion ratios while determining the configuration of the scan chains for each of the expansion ratios using a dependency analysis procedure that accounts for structural dependencies as well as free variable dependencies to improve the probability of detecting faults. Finally, this dissertation addresses the problem of unknown values (X’s) in the output response data corrupting the data and degrading the performance of the output response compactor and thus the overall amount of test compression. Four techniques are presented that focus on handling response data with large percentages of X’s. The first uses X-canceling MISR architecture that is based on deterministically observing scan cells, and the second is a hybrid approach that combines a simple X-masking scheme with the X-canceling MISR for further gains in test compression. The third and fourth techniques revolve around reiterative LFSR X-masking, which take advantage of LFSR-encoded masks that can be reused for multiple scan slices in novel ways. / text

This thesis is concerned with the design and implementation of radio frequency (RF) power amplifiers and micro-electromechanical systems---namely MEMS varactors. This is driven by the many wireless communication systems which are constantly moving towards increased integration, better signal quality, and longer battery life. / The power amplifier consumes most of the power in a receiver/transmitter system (transceiver), and its output signal is directly transmitted by the antenna without further modification. Thus, optimizing the PA for low power consumption, increased linearity, and compact integration is highly desirable. / Micro-electromechanical systems enable new levels of performance in radio-frequency integrated circuits, which are not readily available via conventional IC technologies. They are good candidates to replace lossy, low Q-factor off-chip components, which have traditionally been used to implement matching networks or output resonator tanks in class AB, class F, or class E power amplifiers. The MEMS technologies also make possible the use of new architectures, with the possibility of flexible re-configurability and tunability for multi-band and/or multi-standard applications. / The major effort of this thesis is focused on the design and fabrication of an RF frequency class AB power amplifier in the SiGe BiCMOS 5HP technology, with the capability of being tuned with external MEMS varactors. The latter necessitated the exploration of wide-tuning range MEMS variable capacitors, with prototypes designed and fabricated in the Metal-MUMPS process. / An attempt is made to integrate the power amplifier chip and the MEMS die in the same package to provide active tuning of the power amplifier matching network, in order to keep the efficiency of the PA constant for different input power levels and load conditions. / Detailed simulation and measurement results for all circuits and MEMS devices are reported and discussed.

A low-temperature (<300°C) method to fabricate electrostatically actuated microelectromechanical (MEM) clamped-clamped beam resonators has been developed. It utilizes an amorphous silicon carbide (SiC) structural layer and a thin polyimide spacer. The resonator beam is constructed by DC sputtering a tri-layer composite of low-stress SiC and aluminum over the thin polyimide sacrificial layer, and is then released using a microwave O 2 plasma etch. Deposition parameters have been optimized to yield low-stress films (<50MPa), in order to minimize the chance of stress-induced buckling or fracture in both the SiC and aluminum. Characterization of the deposited SiC was performed using several different techniques including scanning electron microscopy, EDX and XRD. / Several different clamped-clamped beam resonator designs were successfully fabricated and tested using a custom built vacuum system, with measured frequencies ranging from 5MHz to 25MHz. A novel thermal tuning method is also demonstrated, using integrated heaters directly on the resonant structure to exploit the temperature dependence of the Young's modulus and thermally induced stresses.

No description available.

In this thesis, the development of a novel electro-thermally actuated bi-stable out-of-plane two way actuated buckled micro-bridge for a potential application in optical switching is presented. The actuator consists of a bridge supported by 'legs' and springs at its four corners. The springs and the bridge are made of a tri-layer structure comprising of 2.5??m thick low-stress PECVD oxide, 1??m thick high-stress PECVD oxide and 2??m thick heavily phosphorus doped silicon. The legs, on the other hand, are 2??m thick single layer heavily phosphorus doped silicon. Both legs and springs provide elastically constrained boundary conditions at the supporting ends, without of which important features of the micro-bridge actuator could not have been achieved. This microbridge actuator is designed, simulated using ANSYS, fabricated and tested. The results from the testing have shown a good agreement with analytical prediction and ANSYS simulation. The actuator demonstrated bi-stability, two-way actuation and 31??m out-of-plane movement between the two-states using low voltage drive. Buckled shape model, design method for bi-stability and thermo-mechanical model are developed and employed in the design of the micro-bridge. These models are compared with Finite Element (FE) based ANSYS simulation and measurements from the fabricated micro-bridge and have shown a good agreement. In order to demonstrate the potential application of this actuator to optical switching, ANSYS simulation studies have been performed on a micro-mirror integrated with the micro-bridge actuator. From these studies, the optimum micro-mirror size that is appropriate for the integration has been obtained. This optimal mirror size ensures the important features of the actuator. Mirror fabrication experiments in (110) wafer have been carried out to find out the appropriate compensation mask size for a given etch depth and the suitable wafer thickness that can be used to fabricate the integrated system.