Abstract The 1-dimentional model of aerosol process which includes a hot aerosol stream flowing through a tube with thermal gradients between the aerosols stream and the reactor cooled walls was developed to predict the aerosol formation, growth and thermophoretic deposition in high-temperature reactors. The mass and energy conservation equations were solved to determine the concentration and temperature profiles of the components. The model includes particle formation by nucleation, growth by coagulation, Brownian diffusion as well as the loss of aerosol particles by thermophoretic deposition on the cold reactor walls. The developed model results in the system of ordinary differential equations which were solved in SCILAB software.

Process development of halide transport chemical vapor deposited (HTCVD) ZnS:Mn thin film has been studied. To this end, electrical characterization of HTCVD ZnS:Mn electroluminescent devices has been used. Process optimization focused on a simple design of experiment (DOE) with brightness as the major response. Deposition parameters such as HCl and H���S gas flow rates, ZnS and Mn source temperatures and substrate temperature were studied. A substrate temperature of 550��C gives the brightest devices. ZnS source temperature and H���S gas flow rate are insignificant parameters according to the statistical analysis. However HCl gas flow rate and Mn source temperature show strong interaction. It is proposed that the incorporation of Cl into the ZnS:Mn film causes the interaction. A Cl defect is also consistent with anomalous electrical behavior observed in the devices. Cl defects are thought to precipitate at the grain boundaries of the initial growth interface, then diffuse (or migrate) along the grain boundaries and possibly into the bulk crystal. This defect will easily form negative charge leading to asymmetric space charge in the bulk of the phosphor. Since the defects are believed to originate from the nucleation of Cl at high grain boundary density, one potential solution is to remove the Cl source as the grains begin to grow and only later expose the film to Cl. While film growth without HCl present at the beginning of deposition leads to brighter films, it is a sub-optimal solution. Part of the ZnS host does not have luminescent centers. It is believed other processing solutions need to be realized to make the HTCVD system viable. / Graduation date: 1999

Graduation date: 1995

In this work, various aerosol particle transport and deposition mechanisms were studied through the computational fluid dynamics (CFD) modeling, including inertial impaction, gravitational effect, lift force, interception, and turbophoresis, within different practical applications including aerosol sampling inlet, filtration system and turbulent pipe flows. The objective of the research is to obtain a better understanding of the mechanisms that affect aerosol particle transport and deposition, and to determine the feasibility and accuracy of using commercial CFD tools in predicting performance of aerosol sampling devices. Flow field simulation was carried out first, and then followed by Lagrangian particle tracking to obtain the aerosol transport and deposition information. The CFD-based results were validated with experimental data and empirical correlations. In the simulation of the aerosol inlet, CFD-based penetration was in excellent agreement with experimental results, and the most significant regional particle deposition occurred due to inertial separation. At higher free wind speeds gravity had less effect on particle deposition. An empirical equation for efficiency prediction was developed considering inertial and gravitational effects, which will be useful for directing design of similar aerosol inlets. In the simulation of aerosol deposition on a screen, a "virtual surface" approach, which eliminates the need for the often-ambiguous user defined functions, was developed to account for particle deposition due to interception. The CFD-based results had a good agreement compared with experimental results, and also with published empirical correlations for interception. In the simulation of turbulent deposition in pipe flows, the relation between particle deposition velocity and wall-normal turbulent velocity fluctuation was quantitative determined for the first time, which could be used to quantify turbulent deposition, without having to carry out Lagrangian particle tracking. It suggested that the Reynolds stress model and large eddy simulation would lead to the most accurate simulated aerosol deposition velocity. The prerequisites were that the wall-adjacent y+ value was sufficiently low, and that sufficient number of prism layers was applied in the near-wall region. The "velocity fluctuation convergence" would be useful criterion for judging the adequacy of a CFD simulation for turbulent deposition.

Fused deposition modeling is a rapid prototyping process that is widely used to create prototypes. Acrylonitrile butadiene styrene is the most widely used material for fused deposition modeling. The parts are fabricated in a layer by layer fashion and the individual layers are composed of fibers that are deposited, thus making them similar to parts made of a composite material. This study tries to model the behavior of this composite-like material to aid designers in designing parts made of such a “rapid prototyped” material. The mechanical material constants that need to be determined in order to obtain the compliance/ stiffness matrix of the material have been identified and appropriate experiments have been conducted to determine them. Biaxial tensile tests have been conducted to obtain the Young’s moduli and Poisson’s ratios. Torsion tests have been conducted to obtain the Shear moduli. Three point bending tests and combined loading tests have been conducted. Most of the experimental results are in excellent agreement with the analytical/finite element simulation results. Some that are not give a greater insight into the material behavior and have been discussed.

In this study we present the results of electroless deposition of silver (Ag) and electrophoretic deposition (EPD) of Al2O3 layers on glass for application in thin film transistor (TFT). Since Ag exhibits excellent resistivity, it is selected to be the material of conductive layer. Ag thin film electrical and physical parameters are studied as a function of the deposition time and working temperature. We study the thin-film electrical and mechanical properties using 4-point Probe, surface analyzer and nano indenter. The Ag film, thicker than 200 nm, exhibited a specific electrical sheet resistivity of about 500 m£[/¡¼. We also study the thin-film morphology and composition using SEM and FTIR, respectively. In this study, Mechanism and kinetics of the electrophoretic process in an Al2O3 cell are also studied. Al2O3 concentration levels are set from 1.25 to 7.5%, and deposition time from 5~20 seconds. Deposition time and Al2O3 particle concentration is experimentally discussed and characterized. The result shows that a linear relationship between the deposition rate and applied voltage is obtained. Besides, in this study, deposition of conductive layer silver and insulating layer Al2O3 for TFT are studied. A new process to deposit Ag layer and Al2O3 layer to be the conductivity layer and insulating layer of TFT is presented. First, the circuit pattern is defined by lithography process. Then, Ag is deposited with thickness of 200 nanometers. Second, the wafer is immersed in the stripper solution to remove the resist. After the deposition of the Ag on glass is finished, Al2O3 nano-scale particle concentration is prepared for electrophoretic deposition.

Diamond-Like carbon (DLC) films has a lot of advantages, such as high hardness, high thermal conductivity, low expansion coefficient, low friction coefficient, high chemical stability, high impedance. These properties make the DLC films suitable for becoming an insulator in metal insulator semiconductor structure. In this study, DLC films were deposited by electro-deposition technique onto silicon (Si) substrates, in which a mixture of acetic acid and water is used as the electrolyte. The structure of the DLC films is characterized by Raman Spectroscopy. The thermal evaporation technique was used to deposit an aluminum films on the DLC/Si-substrates, to make it as the structure of metal-insulator semiconductor (MIS), and the electrical properties of the MIS were measured by semiconductor parameter analyzer. DLC films were deposited by varying the parameters of electro-deposition process included mainly as the concentration of solution, the spacing between electrode and silicon substrate, deposition temperature, and the applied voltages. The properties and film growth of DLC attributed to the effect of parameters were described in detail. Finally, an electro-deposition model is obtained to describe the growth mechanism of electro-deposition of DLC film.

Abstract The development and advancement of microelectronics technology has been very dramatic. However the cost of creating new process technology by using experiment has been very high. By using computer simulation to evaluate the performance of these equipment, we are able to achieve the same goal at a much lower cost. The reactor of chemical vapor deposition (CVD) is very important to semiconductor production process. This research use numerical method (simulation) to study the process parameters of Low-Pressure Chemical Vapor Deposition (LPCVD) of silicon (Si). In this simulation, the CVD reactor modelings are constructed and discredited by using implicit finite volume method. The grids are arranged in a staggered manner for the discretization of the governing equations. Then the SIMPLE-type algorithm is used to solve all of the discretized algebra equations. Many people in the field are beginning to realize that these challenges can no longer be tackled with the traditional trial-and-error method which have dominated the CVD technology since its beginning, and that modeling may lead to better process and equipment design, reduced costs, and improved IC manufacturing. It is also to be expected that in the future, detailed CVD simulation models will not only be used in design and optimization, but also in real-time process control. Key word: chemical vapor deposition, flow simulation, natural convection.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 122-135). Also available in electronic version. Access restricted to campus users.