Dissertations / Theses on the topic 'Microheaters'

Thesis (Ph. D.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

碩士
國立高雄應用科技大學
光電與通訊工程研究所
101
This study presents the design and fabrication of CMOS process compatible metal silicide microheaters. Metal silicide is an excellent candidate for the heating material of a microheater due to its high temperature stability, high CMOS process compatibility, and low electrical resistivity. In this work, the sheet resistance and the temperature coefficient of resistance of various metal silicide films at different annealed conditions were characterized. In addition, v-shaped three-dimensional heating structures were introduced into the design of the metal silicide microheaters in order to increase the surface area and enhance the mechanical strength of the devices. The material samples of metal silicides include titanium silicide, nickel silicide and titanium-nickel silicide. The material properties of metal silicides were characterized by SIMS and XRD, the thickness of material. The sheet resistance of titanium polycide is 0.975(Ω/□) and its has TCR 0.383(%/℃) at second RTA 900℃. The nickel silicide has sheet resistance 2.8(Ω/□) and TCR 0.29(%/℃) at first RTA 600℃. The results show that the TCR of metal silicides are higher than titanium (0.25%/℃) and platinum (0.25%/℃). Finally, the three-dimensional v-shaped structural metal silicide microheaters were fabricated successfully.

This thesis work focuses on the investigation of the pyroelectric effect from the –Z surface of Lithium (LiNbO3) crystal using different microheater (µH) designs fabricated on the +Z surface of the crystal. Thermal analyses of the microheater designs were performed both theoretically and experimentally using COMSOL™ Multiphysics and FLIR SC7000 thermocamera respectively. The pyroelectric effect was investigated analysing the current impulses detected using a metallic probe detector connected to an oscilloscope. The temperature variation induced by the microheater causes a spontaneous polarization in the crystal resulting in the formation surface bound charges. The electric field generated between the probe and the crystal surface causes the charge emission that appears as a voltage impulse on the oscilloscope. In an ambient condition, the air layer act as a dielectric thin film layer at few hundreds of microns between the detector probe and crystal surface gap spacing. It was demonstrated and validated that the threshold field strength require to generate the PE was near the dielectric breakdown of air. The pyroelectric emission shows a higher dependency on the rate of thermalization of the microheater and also the electric field generated between the probes to surface gap spacing’s of crystal. The deep characterization of µHs is investigated, in order to demonstrate the reliability and the effectiveness of these microdevices for all those applications where compact and low-power consuming electrical field sources are highly desirable.

Wire bonding is the process of creating interconnects between the circuitry on a microchip and PCB boards or substrates so that the microchip can interact with the outside world. The materials and techniques used in this bonding process can cause a wide variation in bond quality, so wire bond reliability testing is very important in determining the quality and longevity of wire bonds. Due to the fact that microchips are encased in protective resins after bonding and their substrates attached to the larger device as a whole, once any single wire bond fails then it could jeapordize the entire device as the wire bonds cannot be individually replaced or fixed. Current methods of reliability testing are lengthy and often destroy the entire sample in the process of evaluation, so the availability of novel non-destructive, real-time monitoring methods as well as accelerated aging could reduce costs and provide realistically timed tests of novel wire bond materials which do not form Intermetallic compounds (IMCs) as rapidly as Au wire on Al substrates. In this thesis, five new chip designs for use in wire bond reliability testing are reported, focusing on the first joint made in a wire bond, called the ball bond. These chips are scaled either to test up to 55 test bonds simultaneously or just one at a time, introducing different requirements for microchip infrastructure capabilities, such as on-chip sensing/data bus, multiplexer, and switches able to operate under High Temperature Storage (HTS) which ranges from temperatures of 150-220 ??C. There are different heating requirements for each of these microchips, needing to be heated externally or containing on-chip microheaters to heat only the ball bond under test, and not the rest of the microchip or surrounding I/O pads. Of the five chip designs, sample chips were produced by an external company. Experimental studies were then carried out with two of these chip designs. They were specifically made to test novel methods of determining ball bond reliability using in-situ, non-destructive sensing, in real-time, while the ball bond undergoes thermal aging. Pad resistance as an analysis tool for ball bond reliability is proposed in this thesis as a new way of evaluating ball bond quality and allows for the testing of electrical connection without the need for specialized measurement probes or difficult bonding processes that contact resistance measurements require. Results are reported for pad resistance measurements of a ball bond under very high temperature storage (VHTS) at 250 ??C, a temperature exceeding typical HTS ranges to accelerate aging. Pad resistance measurements are taken using the four-wire measurement method from each corner of the bond pad, while reversing current direction every measurement to remove thermo-electric effects, and then calculating the average square resistance of the pad from this value. The test ball bond is aged using a novel on-chip microheater which is a N+ doped Si resistive heater located directly underneath the bond pad, and can achieve temperatures up to 300 ??C while not aging any of the I/O pads surrounding it, which are located ~180 ??m away. A 50 ??? resistor is placed 60 ??m away from the heater to monitor the temperature. The use of a microheater allows the aging of novel wire types at temperatures much higher than those permitted for microchip operation while thermally isolating the test bond from the sensing and power bonds, which do not need to be aged. Higher temperatures allow the aging process to be sped up considerably. The microheater is programmatically cycled between 250 ??C (for 45 min) and 25 ??C (for 15 min) for up to 200 h or until the pad resistance measurements fail due breakdown of the bonding pad. Intermetallic compounds forming between the ball bond and the pad first become visible after a few hours, and then the pad becomes almost completely consumed after a day. The pad resistance is measured every few seconds while the sample is at room temperature, and the increase in pad resistance agrees with the fact that Au/Al IMC products are known to have much higher resistance than both pure Au or Al. Also discussed are some aging results of Au wires and Pd coated Cu (PCC) wires bonded to Al bonding pads and aged at a temperature of 200 ??C in an oven for 670 h. The oven aged Au ball bonds also saw IMC formation on the surface of the bonding pad, much like the microheater tests. The PCC ball bonds became heavily oxidized due to lack of Pd on the surface of the ball, the wire portions did not oxidize much. In conclusion, the new structures have been demonstrated to age ball bonds faster than with conventional methods while obtaining non-destructive data. Specifically, the new microheater ages a test bond at an accelerated rate without having an observable effect on the I/O connections used to monitor the test bond. Pad resistance measurements correlate to the aging of the test bond and ensure the electrical integrity of the joint is checked.

With the proliferation of industries world-wide, there is a growing need and interest in sensing and monitoring environmental pollutants and monitoring the concentration of chemicals/gases in industrial process control. There is also an increasing demand for chemical sensors in other applications such as home security, breath analysis and food processing. Design and development of metal-oxide based gas sensor system is reported in this thesis. The system consists of three components viz. micro heater(which aids inheating the sensor film to required temperatures), CMOS ASIC (the sensor interface circuit) and the thin film transducer(a semiconducting metal oxide thin film whose resistance changes with the concentration of the target gas). Microheaters were realized through PolyMUMPs process. Thermal characterization of surface-micromachined microheaters is carried out from their dynamic response to electrothermal excitations. An electrical equivalent circuit model is developed for the thermo-mechanical system. The mechanical parameters are extracted from the frequency response obtained using a Laser Doppler Vibrometer. The resonant frequencies of the microheaters are measured and compared with FEM simulations. The thermal time constants are obtained from the electrical equivalent model by fitting the model response to the measured frequency response. Microheaters with an active area of140m × 140m have been realized on two different layers(poly-1 andpoly-2) with two different air-gaps (2m and 2.75m). The effective time constants, combining thermal and mechanical responses, are intherangeof0.13msto0.22msforheatersonpoly-1,and1.9s to0.15ms for microheaters on poly-2 layer. The thermal time constants of the best microheaters are in the range of a few s, thus making them suitable for sensor applications that need faster thermal response. The mechanical deformation of the microheaters subjected to an electrothermal excitation, due to thermal stress, is also analyzed using lensless in-line digital holographic microscopy (DHM). The numerically reconstructed holographic images of the micro-heaters clearly indicate the regions under high stress. Double exposure method has been used to obtain the quantitative measurements of the deformations, from the phase analysis of the hologram fringes. The measured deformations correlate well with the theoretical values predicted by a thermo-mechanical analytical model. The results show that lensless in-line DHM with Fourier analysis is an effective method for evaluating the thermo-mechanical characteristics of MEMS components. A sensor interface circuit comprising a resistance-to-time period converter as the front-end circuit and a proportional temperature controller to control the microheater temperature is designed and realized in 130nm UMC CMOS technology. The impact of biasing the transistors in subthreshold versus saturation conditions on analog circuit performance is systematically analyzed. A cascode current mirror, designed in 130nm CMOS technology, is biased in subthreshold and saturation regions and its performance has been analyzed through rigorous analytical modeling. The analytical results have been validated with SPICE simulations. It is demonstrated that the subthreshold operation provides better performance in terms of linearity, power, area, output impedance and tolerance to temperature variation, making it a preferable option for applications such as signal conditioning circuitry for environmental sensors. On the other hand, biasing the circuit in saturation is preferable for applications like transceivers and data converters where high bandwidth, SNR and low sensitivity to process variations are the key requirements. Based on this analysis, a sensor interface circuit has been prototyped for resistance measurement on 130nm CMOS technology, using subthreshold cascode current mirrors as the key building blocks. This current mirror results in 14X lower power compared to above-threshold operation. The interface circuit spans 5 orders of magnitude of resistance, and consumes an ultra low power of 326W. A proportional temperature controller with an integrated on-chip power MOSFET is also realized on the same chip for heating and temperature control of microheaters. The microheater is reused as temperature sensor. The entire circuit works with 1.2V supply, except the power MOSFET and the heater driver circuit, which operate with 3.3V supply. ZnO, a semiconducting metal-oxide, is used as the sensing material. Thin films of ZnO are spin-coated over insulating substrates using sol-gel processing technique. Gold pads deposited over the sensing film act as electrodes. The sensor film is characterized at different temperatures for its sensitivity to ethanol. A peak response of 14% change in resistance is observed for 5ppm ethanol, at a working temperature of 275◦C.

With the proliferation of industries world-wide, there is a growing need and interest in sensing and monitoring environmental pollutants and monitoring the concentration of chemicals/gases in industrial process control. There is also an increasing demand for chemical sensors in other applications such as home security, breath analysis and food processing. Design and development of metal-oxide based gas sensor system is reported in this thesis. The system consists of three components viz. micro heater(which aids inheating the sensor film to required temperatures), CMOS ASIC (the sensor interface circuit) and the thin film transducer(a semiconducting metal oxide thin film whose resistance changes with the concentration of the target gas). Microheaters were realized through PolyMUMPs process. Thermal characterization of surface-micromachined microheaters is carried out from their dynamic response to electrothermal excitations. An electrical equivalent circuit model is developed for the thermo-mechanical system. The mechanical parameters are extracted from the frequency response obtained using a Laser Doppler Vibrometer. The resonant frequencies of the microheaters are measured and compared with FEM simulations. The thermal time constants are obtained from the electrical equivalent model by fitting the model response to the measured frequency response. Microheaters with an active area of140m × 140m have been realized on two different layers(poly-1 andpoly-2) with two different air-gaps (2m and 2.75m). The effective time constants, combining thermal and mechanical responses, are intherangeof0.13msto0.22msforheatersonpoly-1,and1.9s to0.15ms for microheaters on poly-2 layer. The thermal time constants of the best microheaters are in the range of a few s, thus making them suitable for sensor applications that need faster thermal response. The mechanical deformation of the microheaters subjected to an electrothermal excitation, due to thermal stress, is also analyzed using lensless in-line digital holographic microscopy (DHM). The numerically reconstructed holographic images of the micro-heaters clearly indicate the regions under high stress. Double exposure method has been used to obtain the quantitative measurements of the deformations, from the phase analysis of the hologram fringes. The measured deformations correlate well with the theoretical values predicted by a thermo-mechanical analytical model. The results show that lensless in-line DHM with Fourier analysis is an effective method for evaluating the thermo-mechanical characteristics of MEMS components. A sensor interface circuit comprising a resistance-to-time period converter as the front-end circuit and a proportional temperature controller to control the microheater temperature is designed and realized in 130nm UMC CMOS technology. The impact of biasing the transistors in subthreshold versus saturation conditions on analog circuit performance is systematically analyzed. A cascode current mirror, designed in 130nm CMOS technology, is biased in subthreshold and saturation regions and its performance has been analyzed through rigorous analytical modeling. The analytical results have been validated with SPICE simulations. It is demonstrated that the subthreshold operation provides better performance in terms of linearity, power, area, output impedance and tolerance to temperature variation, making it a preferable option for applications such as signal conditioning circuitry for environmental sensors. On the other hand, biasing the circuit in saturation is preferable for applications like transceivers and data converters where high bandwidth, SNR and low sensitivity to process variations are the key requirements. Based on this analysis, a sensor interface circuit has been prototyped for resistance measurement on 130nm CMOS technology, using subthreshold cascode current mirrors as the key building blocks. This current mirror results in 14X lower power compared to above-threshold operation. The interface circuit spans 5 orders of magnitude of resistance, and consumes an ultra low power of 326W. A proportional temperature controller with an integrated on-chip power MOSFET is also realized on the same chip for heating and temperature control of microheaters. The microheater is reused as temperature sensor. The entire circuit works with 1.2V supply, except the power MOSFET and the heater driver circuit, which operate with 3.3V supply. ZnO, a semiconducting metal-oxide, is used as the sensing material. Thin films of ZnO are spin-coated over insulating substrates using sol-gel processing technique. Gold pads deposited over the sensing film act as electrodes. The sensor film is characterized at different temperatures for its sensitivity to ethanol. A peak response of 14% change in resistance is observed for 5ppm ethanol, at a working temperature of 275◦C.

Recently, there has been an increasing interest in the electronics world for those aspects related to semiconducting gas sensor (SGS) materials. In view of the increasingly strict legal limits for pollutant gas emissions, there is a great interest in developing high performance gas sensors for applications such as controlling air pollution and exhaust gases in automotive industry. In this way, semiconductor gas sensors offer good advantages with respect to other gas sensor devices, due to their simple implementation, low cost and good stability and sensitivity. The first part of the thesis is dedicated to the synthesis, film structural and sensitivity study of the Tin Oxide film deposited by RF sputtering, doped with noble metal Palladium (Pd). Effects on the Gas Sensitivity due to the deposition parameters like thickness of the film, Substrate temperature, Ar /O2 ratio of the sputtering environment, annealing temperature and duration and doping metal weight % into the Tin Oxide films are studied and the results are shown in detail. The sensitivity and selectivity of the gas sensing film is decided by the operating temperature i.e. the temperature of the gas sensing film while it is in the target gas ambience, Microheaters happen to be the very important component in the gas sensor especially with wide band gap semiconducting metal oxides films such as tin oxide, gallium oxide or indium oxides. Other than gas sensing microheater also finds applications in many areas like thermal dip pen nanolithography, polymerase chain reaction (PCR), fluid pumping with bubbles, in vitro fertilization etc. So in this report due importance was given for the design and fabrication of the microheater. Microheaters are the most power consuming element of the integrated Gas sensors. This is also an important reason for the extensive microheater work in this research. Six different heater patterns were simulated by considering low power and temperature uniformity as an important goals. Among them the best three patterns named Double spiral, “Fan” Shape and “S” shape were chosen for fabrication and both thermal and electrical characterization results of them were presented in detail in the Microheater section of the thesis. It is believed that the intelligent design and integration of the electronic circuitry (for drive, signal conditioning/compensation, and read-out) with the gas sensing element can mitigate some of the significant issues inherent in solid-state gas sensors, such as strong temperature and humidity dependence, signal drift, aging, poisoning, and weak selectivity. The sensitivity of the gas sensors which has been indicated as the dynamic change of resistance in wide range should be read out properly. Towards this aim a low cast high efficient readout circuit is designed and implemented. Temperature monitoring and controlling is a key phenomenon in the metal Oxide based gas sensors since the selectivity mainly depends on the operating temperature of the sensing film. So focus was also shown on the design and implementation of the temperature monitoring and control unit, which been presented in the last part of this thesis.

Recently, there has been an increasing interest in the electronics world for those aspects related to semiconducting gas sensor (SGS) materials. In view of the increasingly strict legal limits for pollutant gas emissions, there is a great interest in developing high performance gas sensors for applications such as controlling air pollution and exhaust gases in automotive industry. In this way, semiconductor gas sensors offer good advantages with respect to other gas sensor devices, due to their simple implementation, low cost and good stability and sensitivity. The first part of the thesis is dedicated to the synthesis, film structural and sensitivity study of the Tin Oxide film deposited by RF sputtering, doped with noble metal Palladium (Pd). Effects on the Gas Sensitivity due to the deposition parameters like thickness of the film, Substrate temperature, Ar /O2 ratio of the sputtering environment, annealing temperature and duration and doping metal weight % into the Tin Oxide films are studied and the results are shown in detail. The sensitivity and selectivity of the gas sensing film is decided by the operating temperature i.e. the temperature of the gas sensing film while it is in the target gas ambience, Microheaters happen to be the very important component in the gas sensor especially with wide band gap semiconducting metal oxides films such as tin oxide, gallium oxide or indium oxides. Other than gas sensing microheater also finds applications in many areas like thermal dip pen nanolithography, polymerase chain reaction (PCR), fluid pumping with bubbles, in vitro fertilization etc. So in this report due importance was given for the design and fabrication of the microheater. Microheaters are the most power consuming element of the integrated Gas sensors. This is also an important reason for the extensive microheater work in this research. Six different heater patterns were simulated by considering low power and temperature uniformity as an important goals. Among them the best three patterns named Double spiral, “Fan” Shape and “S” shape were chosen for fabrication and both thermal and electrical characterization results of them were presented in detail in the Microheater section of the thesis. It is believed that the intelligent design and integration of the electronic circuitry (for drive, signal conditioning/compensation, and read-out) with the gas sensing element can mitigate some of the significant issues inherent in solid-state gas sensors, such as strong temperature and humidity dependence, signal drift, aging, poisoning, and weak selectivity. The sensitivity of the gas sensors which has been indicated as the dynamic change of resistance in wide range should be read out properly. Towards this aim a low cast high efficient readout circuit is designed and implemented. Temperature monitoring and controlling is a key phenomenon in the metal Oxide based gas sensors since the selectivity mainly depends on the operating temperature of the sensing film. So focus was also shown on the design and implementation of the temperature monitoring and control unit, which been presented in the last part of this thesis.

Nowadays the hospitals and the medical centres face a huge challenge finding solutions to improve the efficiency of medical diagnosis. The scope of this project was to develop a “Point-of-Care Diagnostic” (POCD) device, that can give a better alternative for genetic analysis, instead of the usual methods of PCR (polymerase chain reaction). This device is composed by three layers. The first layer which works as a transporter and filter was built on paper. The second layer is the substitute of the regular thermocycling phase in the PCR technique and the third layer incorporates an interdigital capacitor that works as a DNA (deoxyribonucleic acid) sensor with high sensitivity to detect DNA hybridisation. These last two layers were made in kapton film. The devices were produced with microfabrication methods using inkjet printing, lithographic and deposition processes. The device’s characterisation was based on impedance spectroscopy methods. With the purpose of testing the device, the capacitor was functionalised with the YWHAZ gene. However, this process can be performed with any other gene. Due to its characteristics, the device under study was designed to run RT-qPCR (Real time quantitative polymerase chain reaction) and presents itself as an effective way to substitute the traditional PCR techniques. Even more, as the transport of samples to a laboratory and the recruitment of specialised personnel are not necessary, costs and response time are reduced.

In recent years, intense efforts have been made towards the development of miniaturized gas-sensing devices for hazardous gas detection. Carbon monoxide, which is a result of incomplete combustion, is a colourless, odourless, poisonous, explosive and highly toxic gas. It binds with haemoglobin to form carboxyhemoglobin, which reduces the oxygen-carrying capacity of blood and, finally, leads to death. Hence, there is a need to develop a portable and cost-effective gas senor to detect low concentrations of CO gas. MEMS-based metal oxide semiconductor gas sensors offer several advantages compared to conventional optical and electrochemical techniques, such as compact size, low power consumption, quick response, high-temperature stability and low cost for mass production. However, a high-temperature is required for the optimum performance of metal oxide semiconducting gas sensors and such temperatures can be achieved with microheaters. The present thesis work deals with the design, fabrication and characterization of a MEMS gas sensor for the detection of low concentrations of carbon monoxide gas. The work is focused on five specific objectives: a) growth and characterization of sensing film; b) sensitivity enhancement using noble metal additives and nanowire structures; c) design, fabrication and characterization of microheaters; d) development of microhotplate integrated MEMS gas sensor; e) gas sensor packaging. The investigations undertaken are as follows: Titanium dioxide thin film sensing material is deposited using DC magnetron sputtering. The deposition conditions are optimized to obtain stoichiometric TiO2 thin films and are characterized for carbon monoxide gas detection. The influence of the operating temperature, annealing temperature, thin film thickness and the interdigitated electrode geometry on the sensor response is investigated. The TiO2 thin film sensor (annealed at 800 °C) shows a high response (79.5 %) to CO gas and a low response (<23%) to other reducing and oxidizing gases at 400 °C. It is observed that the sorption is completely reversible and the response and recovery times are of the order of 50 and 120 sec respectively. Noble metal additives such as Au, Pt, and Pd are decorated on the TiO2 surface to enhance the sensitivity and selectivity of the TiO2 thin film gas sensors. The pristine TiO2 thin film gas sensor (annealed at 400 °C) is found to exhibit a detectable response only when the operating temperature is above 300 °C; below this temperature there is no detectable change in resistance in the presence of 5000 ppb of CO gas. The response is found to increase with the operating temperature and it exhibits a maximum response of 58.6 % at 400 °C. The surface-modified TiO2 thin film based gas sensor shows a remarkable response event at 100 °C. The Au-TiO2 and Pt-TiO2 thin film gas sensor has been found to exhibit a maximum response of 83.46 and 79.64 % at 200 and 250 °C respectively, whereas, the Pd-TiO2 thin film gas sensor exhibits a n to p transition above 150 °C. TiO2 nanowires are synthesized using hydrothermal processes and are characterized for the detection of low concentrations of carbon monoxide gas. The TiO2 nanowire-based gas sensor shows a detectable change in its resistance even at 150 °C and its response is found to increase with the temperature. At 400 °C, the sensor is found to exhibit a maximum response of 80 % for 5000 ppb of CO. Further, under the same operating conditions, the sensor is found to exhibit a remarkable change in its resistance (a response of 5.6 %) for 100 ppb of CO. The response and recovery times of the sensor are of the order of 18 and 27 s respectively. Microheaters are designed and simulated using the CoventorWare MEMS design and analysis tool to optimize the geometry of the microheater structure for uniform temperature distribution and low power consumption. Low resistive molybdenum thin films are deposited for high temperature microheater applications. The molybdenum microheaters are fabricated and their electro-thermo-mechanical characteristics are studied. The microheater membrane stability is analyzed by measuring its deformation under high thermal stresses using an optical profilometer. The microheater response is characterized in both pulsed and constant temperature modes of operation; it is found to exhibit a negligible resistance drift after 600 hours of continuous operation, indicating its long-term thermal and mechanical stability. The response and recovery times are in the order of a few milliseconds (19 and 34 ms), which make them suitable for gas-sensing applications. Finally, microhotplate integrated MEMS gas sensors are fabricated, packaged and characterized for carbon monoxide gas detection at elevated temperatures (250 to 700 °C). The sensitivity, selectivity, repeatability and response and recovery times of the miniaturized MEMS gas sensors are investigated. The developed MEMS gas sensor is found to exhibit a high sensitivity and selectivity to CO gas compared to the TiO2 thin film based gas sensor. It shows a highest response of 96.14 % for 5000 ppb of CO and a minimum response (< 28%) to other reducing and oxidizing gases at 550 °C optimized temperatures. The MEMS gas sensor is found to exhibit quick response and recovery times (9 and 21 s) compared to thin film-based gas sensors (50 and 120 s).

碩士
國立成功大學
機械工程學系碩博士班
97
The target of this research is to establish an observation system of thermal bubble and to design and fabricate the micro-heater in order to discuss the thermal bubble behavior for combining the mixer in our Lab and helping to mix faster and good mixing efficiency. In fabrication of micro-heater, this research focus on the design of micro-heater and the choice of materials further. For design, we use single mask to fabricate the heater replacing several masks for saving the fabricating time. For the materials, we choose the Ta to be the material to replace polysilicon and expensive material Pt which were usually used in past. In the system of observation system, we design a flash observation system to substitute for the expensive high speed CCD for saving the money. Using high light LED to flash for freezing the thermal bubble instant behavior and using the ordinary CCD system to catch movie of bubbles. Finally, using the cutting soft to get the pictures of instant bubble behavior to know the bubble growth and shrink for the combination of our Lab mixer in the future. Finally, we’ll discuss bubble sizes between frequencies and voltages and the feasibility of observation system. We can know the micro-heater in this research can generate well bubbles in low frequencies. And the advantages of the micro-heater in this research, like low resistance, heat-resistant degree, and good heat dissipation, contribute to improve the heat dissipation and the strength of the Pt micro-heater for increasing the life of the heater.

Current gas sensor technology, although meeting the minimum requirements in many instances, suffers for a number of limitations. Hence, there is currently a considerable volume of research being undertaken at many laboratories of different countries. In the past, all chemical sensors and catalyst were optimized empirically by a trial and error method. Today, however, systematic research and development is becoming increasingly important in order to improve sensors and to find new sensing principles. Obtaining a long term stable gas sensor with improved sensitivity, selectivity, and low cost for mass production passes through fundamental research and material characterization to build new chemically sensitive devices or to improve existing ones. The bottom line in the design and manufacture of modern gas sensors is the transfer from ceramic(of Figaro type) to thin film gas sensors(TFGs). This transfer provides new opportunities for further microminiaturization, power consumption and cost reduction of gas sensors. Therefore, at the present time, thin film gas sensors are the basis for the design of the modern gas sensitive multi-parameter microsensor systems. Applications of these systems include environment, security, home systems, smart buildings, transportation, discrete manufacturing, process industries and so on. Microelectromechanical systems(MEMS) based integrated gas sensors present several advantages for these applications such as ease of array fabrication, small size, and unique thermal manipulation capabilities. MEMS based gas sensors; which are usually produced using a standard CMOS(Complimentary Metal Oxide Semiconductor) process, have the additional advantages of being readily realized by commercial foundries and amenable to the inclusion of on-chip electronics. In order to speed up the design and optimization of such integrated sensors, microheater designs for gas sensor applications have been presented as first part of the present thesis. As heater design is the key part for a gas sensor operation. So 3D simulations have been used to optimize micro-heater geometry. The application of MEMS Design Tool(COVENTORWARE) has been presented to the design and analysis of micro-hotplate (MHP) structures. Coupled Electro-thermal analysis provided an estimation of thermal losses and temperature distribution on the hotplate for realistic geometrical and material parameters pertinent to fabrication technology. Five microheater designs have been proposed in terms of different sizes and shapes in order to optimize the microhotplate structure to be used for gas sensor operation for the specified range of temperature and power consumption. To produce a gas sensor, which is able to detect LPG leak, thin films of tin oxide have been developed. FR sputtering has been used to deposit gas sensitive tin oxide thin filmls under various deposition conditions. Four different values of pressure in the range from high pressure(5 X 10-2 mbar) to lower pressure (2 X 10-3 mbar), three RF power values 50, 75, 100 W and varied oxygen percentage in sputtering atmosphere (0-18%) have been used to optimize the material properties of tin oxide thin films to study the sensitivity towards LPG. All the samples have been analyzed using various macro and microscopic characterization techniques. Extensive studies have been done on the sensor response for the samples deposited under different conditions. Finally the sample film deposited at 5 x 10-3 mbar, with applied power of 75 W in the presence of 8% oxygen, showed maximum sensitivity towards LPG.

Current gas sensor technology, although meeting the minimum requirements in many instances, suffers for a number of limitations. Hence, there is currently a considerable volume of research being undertaken at many laboratories of different countries. In the past, all chemical sensors and catalyst were optimized empirically by a trial and error method. Today, however, systematic research and development is becoming increasingly important in order to improve sensors and to find new sensing principles. Obtaining a long term stable gas sensor with improved sensitivity, selectivity, and low cost for mass production passes through fundamental research and material characterization to build new chemically sensitive devices or to improve existing ones. The bottom line in the design and manufacture of modern gas sensors is the transfer from ceramic(of Figaro type) to thin film gas sensors(TFGs). This transfer provides new opportunities for further microminiaturization, power consumption and cost reduction of gas sensors. Therefore, at the present time, thin film gas sensors are the basis for the design of the modern gas sensitive multi-parameter microsensor systems. Applications of these systems include environment, security, home systems, smart buildings, transportation, discrete manufacturing, process industries and so on. Microelectromechanical systems(MEMS) based integrated gas sensors present several advantages for these applications such as ease of array fabrication, small size, and unique thermal manipulation capabilities. MEMS based gas sensors; which are usually produced using a standard CMOS(Complimentary Metal Oxide Semiconductor) process, have the additional advantages of being readily realized by commercial foundries and amenable to the inclusion of on-chip electronics. In order to speed up the design and optimization of such integrated sensors, microheater designs for gas sensor applications have been presented as first part of the present thesis. As heater design is the key part for a gas sensor operation. So 3D simulations have been used to optimize micro-heater geometry. The application of MEMS Design Tool(COVENTORWARE) has been presented to the design and analysis of micro-hotplate (MHP) structures. Coupled Electro-thermal analysis provided an estimation of thermal losses and temperature distribution on the hotplate for realistic geometrical and material parameters pertinent to fabrication technology. Five microheater designs have been proposed in terms of different sizes and shapes in order to optimize the microhotplate structure to be used for gas sensor operation for the specified range of temperature and power consumption. To produce a gas sensor, which is able to detect LPG leak, thin films of tin oxide have been developed. FR sputtering has been used to deposit gas sensitive tin oxide thin filmls under various deposition conditions. Four different values of pressure in the range from high pressure(5 X 10-2 mbar) to lower pressure (2 X 10-3 mbar), three RF power values 50, 75, 100 W and varied oxygen percentage in sputtering atmosphere (0-18%) have been used to optimize the material properties of tin oxide thin films to study the sensitivity towards LPG. All the samples have been analyzed using various macro and microscopic characterization techniques. Extensive studies have been done on the sensor response for the samples deposited under different conditions. Finally the sample film deposited at 5 x 10-3 mbar, with applied power of 75 W in the presence of 8% oxygen, showed maximum sensitivity towards LPG.

The zebrafish has emerged as an important genetic model system for the study of vertebrate development. However, while genetics is a powerful tool for the study of early gene functions, the approach is more limited when it comes to understanding later functions of genes that have essential roles in early embryogenesis. There is thus a need to manipulate gene expression at different times, and ideally only in some regions of the developing embryo. Methods for conditional gene regulation have been established in Drosophila, C.elegans and the mouse, utilizing conditional gene activation systems such as the Gal4-UAS system (fly) and the cre/lox recombination system (mouse). While these tools are also being developed in zebrafish, the accessibility of the zebrafish embryo makes other approaches both possible and desirable. We have taken advantage of a heat-shock inducible system that uses the hsp70 promoter that is activated by cellular stress, such as heat. Having established that this global heat shock method allows temporal control of gene expression, we aimed to spatially control gene expression by applying controlled thermal heat to only a small region of the embryo. This would allow us to determine cell- and tissue-autonomous roles for developmentally important genes in an embryo with otherwise normal gene function. We have now developed a device that uses a laser to heat a defined region of the embryo, and thus activate the hsp70 promoter only in restricted regions of the embryo. The output of a 75 mW red laser pointer was focused into the 50 µm diameter core of an optical fiber, whose cleaved and coated end was used to heat, and thus induce, gene expression in a defined area. We have established conditions that allow controlled heating and trans-gene activation in small regions of the embryo without inducing cell death. This new tool will allow us to study the cell-autonomous roles of embryonic signaling molecules in cell differentiation, proliferation, and survival in a variety of tissues and at different times.

碩士
國立交通大學
機械工程系所
96
The present study purposes to experimentally examine the influence of liquid properties, hydrophilic conditions, and power on thermal bubble behavior. The CCD camera connected to a video recorder is utilized to visualize thermal bubble formation and growth process, and defined the advisable range for the application of bubble actuation for various viscosity of liquids, hydrophilic conditions, and power. Some significant physical parameters are define, and the thermodynamic behavior of thermal bubble is discussed in detail at various viscosity of liquids, hydrophilic conditions, power and various of the physical parameters. Experimental results show obvious influences of viscosity, hydrophilic conditions on the advisable range for application of bubble actuation. The instability of bubble formation and growth process take place for various hydrophilic conditions. Experimental results show the obvious influences of viscosity, hydrophilic conditions, and power on contact diameter between bubble and surface, height of the thermal bubble, and volume of the thermal bubble.

Silicon photonics has become one of the leading candidates for the next generation optical communication platform. In addition to being an inexpensive material and compatible with Complementary metal–oxide–semiconductor (CMOS) manufacturing, silicon exhibits low absorption at optical telecommunication bands. However, high propagation loss and poor light confinement in narrow Si waveguides have limited high-density optical integration.
In this work, we show the fabrication and characterization of a novel type of devices named E-skid devices that can reduce the skin depth and suppress the large spatial content of evanescent light. These devices use artificial anisotropic dielectric metamaterial to suppress the evanescent waves. Beside E-skid devices, we also discuss the fabrication and experimental characterization of mode filters using Silicon on Insulator that can block the fundamental TE0 and allow the higher order modes to pass through using Multi Mode Interference.
In this work, the mode is filtered using radiation, not by reflection.
Beside Silicon, Silicon Nitride has also gained much interest because of its low loss, smaller nonlinear absorption and higher Kerr effect. Silicon Nitride waveguides have widely
been used for lots of applications specially the optical frequency comb generation. One special case of coherent optical frequency comb is Soliton in which case the non-linearity and dispersion cancel each other’s effect and keep the pulse without distortion. In this work, we described the Silicon Nitride fabrication process and did a comparative analysis with other research groups who fabricates similar devices. We tried to improve our process by inserting a few additional steps in our fabrication process. We also investigated our process step by step and found out reasons for our low quality factor and low yield. We found a few factors that might be responsible for the low quality factor and addressed them. We fabricated real devices using our modified process and saw improvement in quality factors, yield and thermal performance of the devices.
Finally, we describe an edge polishing method for Silicon Nitride microring resonator devices, which we developed from scratch and we can polish edges down to sub-micron level. Thus, the edges become optically flat and it allowed us to do heterogeneous integration with an Indium Phosphide chip. This paves away for some exciting opportunities like on-chip frequency comb generation.