The large carbon dioxides produced by highly developed industries not only result in serious air pollution and health problems, but also cause ocean acidification and decrease the survival rate of fry in aquaculture. Therefore, to develop a system for real-time detection of the concentration of carbon dioxide in aquaculture has become a very important research issue. Optical analysis and gas-chromatography are the two main methods adopted in conventional gas detection. Although the conventional carbon dioxide detectors presented high sensitivity and accuracy, the high fabrication cost, large dimension, low capability of batch fabrication and without real-time monitoring function will limit their applications. This thesis utilizes MEMS technology to implement an extended-gate field-effect transistor (EGFET) with an integrated gas permeable membrane for development of a high-sensitivity, small size and low cost carbon dioxide microsensor. The main material of the carbon dioxide gas permeable membrane adopted in this research is dioctyl sebacate. The main processing steps of the proposed microsensor include four photolithography and four thin-film deposition processes. In addition, the influences of the channel width/length ratio of EGFET and the coating of gas permeable membrane on the sensing performances of presented microsensor are also investigated in this study. The chip size of the implemented carbon dioxide microsensor is 11 mm¡Ñ13 mm¡Ñ 0.5 mm and the sensing area is 1 mm¡Ñ1 mm. As the carbon dioxide concentration varies from 0.25 mM to 50 mM, a very high sensitivity (42.3 mV/ppm) and sensing linearity (99.2%) of the proposed EGFET microsensor can be demonstrated. In addition, the response time of the presented carbon dioxide microsensor is only about 100 seconds, hence it is very suitable for developing a real-time monitoring microsystem.

Utilizing self-assembled monolayer nanotechnology, micro-electro-mechanical systems (MEMS) and IC technologies, a novel flexural plate-wave (FPW) biosensor is developed in this dissertation for detecting the immunoglobulin-E (IgE) concentration of human serum. The acoustic waves of the proposed FPW devices are launched by the 25-pair inter-digital transducer (IDT) input electrodes and propagated through the 4.82 £gm-thick Si/SiO2/Si3N4/Cr/Au/ZnO floating thin-plate. Since the thickness of such floating thin-plate is much smaller than the designed wavelength of FPW device (80 £gm), most of the propagating wave energy will not be dissipated into outside of thin-plate and the mass sensitivity is very high. To further reduce the insertion loss of the proposed FPW devices, two 3 £gm-thick Al reflection grating electrodes (RGE) are designed beside the input and output IDTs. To implement a FPW-based IgE biosensor, a Cr/Au electrode layer has to be deposited on the backside of the floating thin-plate to serve as a substrate for further coating the cystamine SAM/glutaraldehyde/IgE antibody layers. Once the IgE antigens of human serum are bound to the IgE antibody layer, the small change in the mass of floating thin-plate will result in a shift of center frequency of the testing FPW-based biosensor. Compared to the reference FPW biosensors, the shift of center frequency generated by the testing FPW biosensor under different IgE antigen concentration can be detected by commercial network analyzer or the frequency-shift readout system developed by our collaboration laboratory (VLSI Design Lab. of NSYSU). Compared to commercial enzyme linked immunosorbent assay (ELISA) analyzer (sample volume >25 £gl/well, testing time >60 min, dimension>40 cm ¡Ñ30 cm¡Ñ10 cm), the implemented FPW-based IgE biosensor presents a smaller sample volume (<5 £gl), faster response (<10 min) and smaller size (<9 mm¡Ñ6 mm¡Ñ0.5 mm). In addition, a very low insertion loss (-9.2 dB), a very high mass sensitivity (-6.08¡Ñ109 cm2 g-1) and a very high sensing linearity (99.46 %) of the proposed IgE biosensor can be demonstrated at 6.6 MHz center frequency. This study successfully developed a novel FPW-based allergy biosensor by MEMS technology, which has great potential to be further applied into point-of-care testing (POCT) microsystem.

This thesis presents the first fully tunable substrate integrated waveguide (SIW) filter implemented with PIN diodes and RF MEMS switches. The methodology for tuning SIW filters is explained in detail and is used to create three separate designs. Each SIW cavity is tuned by perturbing via posts connecting or disconnecting to/from the cavity's top metal layer. In order to separate the biasing network from the SIW filter, a three-layer PCB is fabricated using Rogers RT/duroid substrates. The first tunable design utilizes the Philips BAP55L PIN diode. This two-pole filter provides six frequency states ranging from 1.55 GHz to 2.0 GHz. Fractional bandwidth ranges from 2.3 percent – 3.0 percent with insertion loss and return loss better than 5.4 dB and 14 dB respectively for all frequency tuning states. The second tunable design utilizes the Radant RMSW-100 MEMS switch, providing six states ranging from 1.65 GHz to 2.1 GHz. Fractional bandwidth for this filter varies from 2.5 percent - 3.0 percent with insertion loss and return loss better than 12.4 dB and 16 dB respectively for all states. The third design utilizes the OMRON 2SMES-01 RF MEMS relay, providing fourteen states ranging from 1.19 GHz to 1.58 GHz. Fractional bandwidth ranges from 3.6 percent - 4.4 percent with insertion loss and return loss better than 4.1 dB and 15 dB respectively for all frequency states. Two of the three designs (Philips PIN diode and OMRON MEMS) produced good results validating the new SIW filter tuning methodology. Finally, to illustrate the advantage of microstrip planar structures integrated with SIW structures, low pass filters (LPFs) are implemented along the input and output microstrip-to-SIW transition regions of the tunable SIW filter. With minimal change to the overall filter size, this provides spurious suppression for the additional resonant modes inherently present in waveguide structures. The implemented design utilizes the same OMRON MEMS tunable SIW filter specifications. This two-pole tunable filter provides the same performance as the previous OMRON MEMS design with exception to an added 0.7 dB insertion loss and spurious suppression of -28 dB up to 4.0 GHz for all frequency tuning states.

The main components of the vibration-based microgenerator incorporate vibratile structure, magnetic thin film, and coils. In this thesis work, bulk-micromachining technology and laser-micromachining technology were used to fabricate the vibratile structure of the microgenerator. And this is the beginning of the development of the microgenerator. Bulk-micromachining technology was widely used in micro-electromechanical system (MEMS). The most advantage of the technology is that it can be integrated with IC process in the future. And the roughness of the wafer is the key point of the etching process. In addition, 355nm UV Nd:YAG laser was also used to fabricate the vibratile structure. The period of fabricating prototype can be shortened by laser-micromachining. In laser-micromachining system, the dual-prism was used to change the direction of the laser beam by adjusting the initial phase of one of the prisms. When the laser beam moves relatively to workstation, the cutting process can be proceeded. By this system, the cutting linewidth is controllable. This technology has be used to fabricate the microstructure successfully, and the aspect ratio is up to 10, and the feature size is 50&#x00B5;m. Circular spiral spring structure was fabricated successfully, and it is to be the vibratile structure of the microgenerator. Finite element software ANSYS was used to simulate the dynamic characterization of the vibratile structure and the vibration testing experiment was carried out. The result shows that the experimental resonant frequency is very close to the simulative resonant frequency. So this vibratile structure can be used in microgenerator.

This thesis reports the development and analysis of high performance CMOS readout electronics for increasing the performance of MEMS gyroscopes developed at Middle East Technical University (METU). These readout electronics are based on unity gain buffers implemented with source followers. High impedance node biasing problem present in capacitive interfaces is solved with the implementation of a transistor operating in the subthreshold region. A generalized fully differential gyroscope model with force feedback electrodes has been developed in order to simulate the capacitive interfaces with the model of the gyroscope. This model is simplified for the single ended gyroscopes fabricated at METU, and simulations of resonance characteristics are done. Three gyroscope interfaces are designed by considering the problems faced in previous interface architectures. The first design is implemented using a single ended source follower biased with a subthreshold transistor. From the simulations, it is observed that biasing impedances up to several gigaohms can be achieved. The second design is the fully differential version of the first design with the addition of a self biasing scheme. In another interface, the second design is modified with an instrumentation amplifier which is used for fully differential to single ended conversion. All of these interfaces are fabricated in a standard 0.6 &micro / m CMOS process. Fabricated interfaces are characterized by measuring their ac responses, noise response and transient characteristics for a sinusoidal input. It is observed that, biasing impedances up to 60 gigaohms can be obtained with subthreshold transistors. Self biasing architecture eliminates the need for biasing the source of the subthreshold transistor to set the output dc point to 0 V. Single ended SOG gyroscopes are characterized with the single ended capacitive interfaces, and a 45 dB gain improvement is observed with the addition of capacitive interface to the drive mode. Minimum resolvable capacitance change and displacement that can be measured are found to be 58.31 zF and 38.87 Fermi, respectively. The scale factor of the gyroscope is found to be 1.97 mV/(&deg / /sec) with a nonlinearity of only 0.001% in &plusmn / 100 &deg / /sec measurement range. The bias instability and angle random walk of the gyroscope are determined using Allan variance method as 2.158 &deg / /&amp / #8730 / hr and 124.7 &deg / /hr, respectively.

This thesis presents a novel monolithic phased array implemented using the RF MEMS technology. The structure, which is designed at 15 GHz, consists of four linearly placed microstrip patch antennas, 3-bit distributed RF MEMS low-loss phase shifters, and a corporate feed network. The RF MEMS phase shifter employed in the system consists of three sections with a total of 28 unit cells, and it occupies an area of 22.4 mm &amp / #61620 / 2.1 mm. The performance of the phase shifters is improved using high-Q metal-air-metal capacitors in addition to MEMS switches as loading elements on a high-impedance coplanar waveguide transmission line. The phased array is fabricated monolithically using an in-house surface micromachining process, where a 1.2-&amp / #61549 / m thick gold structural layer is placed on a 500-&micro / m thick glass substrate with a capacitive gap of 2 &amp / #61549 / m. The fabrication process is simple, requires only 6 masks, and allows the implementation of various RF MEMS components on the same substrate, such as RF MEMS switches and phase shifters. The fabricated monolithic phased array occupies an area of only 6 cm &amp / #61620 / 5 cm. The measurement results show that the phase shifter can provide nearly 20&amp / #61616 / /50&amp / #61616 / /95&amp / #61616 / phase shifts and their eight combinations at the expense of 1.5 dB average insertion loss at 15 GHz. The phase shifters can be actuated with 16 V, while dissipating negligible power due to its capacitive operation. It is also shown by measurements that the main beam can be steered to 4&amp / #61616 / and 14&amp / #61616 / by suitable settings of the RF MEMS phase shifters.

In this thesis, the integration of a MEMS based inertial measurement unit and a three axis solid state magnetometer are studied. It is a fact that unaided inertial navigation systems, especially low cost MEMS based navigation systems have a divergent behavior. Nowadays, many navigation systems use GPS aiding to improve the performance, but GPS may not be applicable in some cases. Also, GPS provides the position and velocity reference whereas the attitude information is extracted through estimation filters. An alternative reference source is a three axis magnetometer, which provides direct attitude measurements. In this study, error propagation equations of an inertial navigation system are derived / measurement equations of magnetometer for Kalman filtering are developed / the unique method to self align the MEMS navigation system is developed. In the motion estimation, the performance of the developed algorithms are compared using a GPS aided system and magnetometer aided system. Some experiments are conducted for self alignment algorithms.

In this thesis 10x10 reconfigurable reflectarray is designed at 26.5 GHz where the change in the progressive phase shift between elements is obtained with RF MEMS switches in the transmission lines of unit elements composed of aperture coupled microstrip patch antenna (ACMPA). The reflectarray is illuminated by a horn antenna, and the reflected beam is designed to switch between broadside and 40&deg / by considering the position of the horn antenna with respect to the reflectarray. In the design, the transmission line analysis is applied for matching the ACMPA to the free space. The full wave simulation techniques in HFSS are discussed to obtain the phase design curve which is used in determining two sets of transmission line lengths for each element, one for the broadside and the other for switching to the 40&deg / at 26.5 GHz. The switching between two sets of transmission line lengths is sustained by inserting RF MEMS switches into the transmission lines in each element. Two types of RF MEMS switches, series and shunt configurations, are designed for the switching purpose in the reflectarray. The phase errors due to nonideal phase design curve and type of the RF MEMS switch are reduced. The possible mutual coupling effects of the bias lines used to actuate the RF MEMS switches are also eliminated by the proper design. To show the validity of the design procedure, a prototype of 20x20 reflectarray composed of ACMPA elements is designed at 25GHz and produced using Printed Circuit Board (PCB) technology. The measurement results of the prototype reflectarray show that the main beam can be directed to the 40&deg / as desired. The process flow for the production of the reconfigurable reflectarray is suggested in terms of integration of the wafer bonding step with the in-house standard surface micromachined RF MEMS process.

This thesis presents fabrication of shunt, capacitive contact type RF MEMS switches which are designed according to given mm-wave performance specifications. The designed switches are modified for investigation in terms of reliability and lifetime. To observe the real-time performance of switches a time domain measurement setup is established and a CV (capacitance vs. voltage) curve measurement system is also included to measure CV curves, pull-in and hold-down voltages and the shifts of these due to actuations. By using the established setup reliability and lifetime measurements under different bias waveforms in different environments are performed. After investigation for the most suitable condition for improving lifetime long-term tests are performed and the outstanding result of more than 885 hours of operation under cycling bias waveform is obtained.

A novel complementary metal oxide semiconductor (CMOS) compatible microchannel heat sink is designed, fabricated, and tested for electronic cooling applications. The proposed microchannel heat sink requires no design change of the electronic circuitry underneath. Therefore, microchannels can be fabricated on top of the finished CMOS wafers by just adding a few more steps to the fabrication flow. Combining polymer (parylene C) and metal (copper) structures, a high performance microchannel heat sink can be easily manufactured on top of the electronic circuits, forming a monolithic cooling system. In the design stage, computer simulations of the microchannels with several different dimensions have been performed. Microchannels made of only parylene showed poor heat transfer performance as expected since the thermal conductivity of parylene C is very low. Therefore an alternative design comprising structural parylene layer and embedded metal layers has been modeled. Copper is selected as the metal due to its simple fabrication and very good thermal properties. The results showed that the higher the copper surface area the better the thermal performance of the heat sinks. Based on the modeling results, the final test structures are designed with full copper sidewalls with a parylene top wall. Several different microchannel test chips have been fabricated in METU-MEMS Research &amp / Application Center cleanroom facilities. The devices are tested with different flow rates and heat loads. During the tests, it was shown that the test devices can remove about 126 W/cm2 heat flux from the chip surface while keeping the chip temperature at around 90&deg / C with a coolant flow rate of 500 &mu / l/min per channel.