This work involves three related projects, all of which involve numerical modeling of industrially important systems in which thin films or particles are synthesized from the gas phase. All three projects involve experiments to which the models can be compared.
Ashok Gidwani, Graduate Student Researcher
Dimitrios I. Iordanoglou, Research Associate
John Larson, Graduate Student Researcher
Milind Mahajan, Graduate Student Researcher
Aaron Neuman, Graduate Student Researcher
Song-Moon Suh, Graduate Student Researcher
Mark Swihart, Research Associate
99/19 |
"The Effect of Substrate Temperature on the Properties of Nanostructured Silicon Carbide Films Deposited by Hypersonic Plasma Particle Deposition," J. Blum, N. Tymiak, A. Neuman, Z. Wong, N.P. Rao, S.L. Girshick, W.W. Gerberich, P.H. McMurry, and J. Heberlein, University of Minnesota Supercomputing Institute Research Report UMSI 99/19, February 1999. Publication in press. |
99/20 |
"Ab Initio Structures and Energetics of Selected Hydrogenated Silicon Clusters Containing Six to Ten Silicon Atoms," M.T. Swihart and S.L. Girshick, Chemical Physics Letters, 307, p. 527 (1999). |
99/21 |
"An Analysis of Flow, Temperature and Chemical Composition Distortion in Gas Sampling Through an Orifice During Chemical Vapor Deposition," M.T. Swihart, and S.L. Girshick, Physics of Fluids, 11, p. 821 (1999). |
99/23 |
"Thermal Plasma Deposition of Nanostructured Films," A. Neuman, J. Blum, N. Tymiak, Z. Wong, N.P. Rao, W.W. Gerberich, P.H. McMurry, J. Heberlein, and S.L. Girshick, IEEE Transactions on Plasma Science, 27, p. 46 (1999). |
99/26 |
"Thermochemistry and Kinetics of Silicon Hydride Cluster Formation during Thermal Decomposition of Silane," M.T. Swihart and S.L. Girshick, Journal of Physical Chemistry B, 103, p. 64 (1999). |
99/163 |
"Characterization of the Near-Surface Gas-Phase Chemical Environment in Atmospheric-Pressure Plasma Chemical Vapor Deposition of Diamond," J.M. Larson, M.T. Swihart, and S.L. Girshick, Diamond and Related Materials, 8, p. 1863 (1999). |
99/208 |
"Generation and Growth of Nanoparticles in Low-Pressure Plasmas," U. Kortshagen, U.V. Bhandarkar, M.T. Swihart, S.L. Girshick, University of Minnesota Supercomputing Institute Research Report UMSI 99/208, November 1999. Publication in press. |
99/245 |
"RF Themal Plasma Chemical Vapor Deposition of Diamond Does Film Morphology Evolve Differently in Acetylene-Rich Environments?," J.M. Larson and S.L. Girshick, Proceedings of the 14th International Syumposium on Plasma Chemistry, 4, p. 1663 (1999). |
99/246 |
"Hypersonic Plasma Particle Deposition of Nanostructured Silicon Carbide Films," N. Tymiak, D.I. Iordanoglou, D. Neumann, A. Gidwani, F. Di Fonzo, M.H. Fan, N.P. Rao, W.W. Gerberich, P.H. McMurry, J. Heberlein, and S.L. Girshick, Proceedings of the 14th International Syumposium on Plasma Chemistry, 4, p. 1989 (1999). |
99/247 |
"Modeling of Plasma Chemistry for Silicon Hydride Clustering in PECVD Processes," U.V. Bhandarkar, M.T. Swihart, U. Kortshagen, and S.L. Girshick, Proceedings of the 14th International Syumposium on Plasma Chemistry, 4, p. 2205 (1999). |
Plasma processes are used extensively in the microelectronics industry to deposit and etch thin films. Particle contaminants in such systems lead to defects and reduced product yield. Gas-phase nucleation is a major source of particle formation in these processes. These researchers are developing approaches for modeling particle formation, growth, charging, coagulation, and transport for these industrially relevant processes. The goal of this work is to develop and integrate particle nucleation and growth models with transport models of the processing environment. Detailed reaction mechanisms have been developed that describe silicon clustering chemistry in the silane-hydrogen system, and these mechanisms have been coupled to models of the reacting flow and particle growth and transport during the thermal chemical vapor deposition of silicon films. In the past year, this model has been substantially extended to account for plasma chemistry and for conditions typical of low-pressure silane plasmas. Based on the experience obtained for the silane-hydrogen system, a model of particle nucleation and transport is being developed in the more complicated silane-oxygen system, which is used for the deposition of dielectric SiO2 films. Work is now developing models of particle formation in the silane-oxygen system for the case of high density plasmas (i.e., high electron density but very low pressure), which are becoming the preferred mode for advanced processing in the semiconductor industry.
Because of its unparalleled combination of superlative properties, there is extraordinary interest in diamond for a broad range of applications. In the past year, these modeling efforts have been closely coupled to the experimental program. The spin/chemkin ii package was used to model the chemistry occurring in a gas chromatograph sample probe and the growth conditions in a newly designed reactor. These researchers have also developed two-dimensional models of the near surface region that accounts for the disturbance of the system due to sampling. Current modeling projects include development of a two-dimensional electrohydrodynamic model of the r.f. plasma torch used in the diamond CVD process and improving the treatment of surface chemistry in the one-dimensional modeling so that growth of different crystal orientations can be accounted for as predicted. The surface reaction model is partly based on the results of ab initio and kinetic Monte Carlo calculations of diamond growth processes being carried out in Professor Jeffrey Roberts' research group in the Chemistry Department at the University of Minnesota. These efforts, together with experiments, are defining the growth conditions that lead to high quality films and are providing a fundamental understanding of the processes that govern film orientation, defect density, and growth rate.
Nanophase materials show reduced sintering temperature, increased hardness, and interesting electronic and optical properties. These researchers have developed a process called hypersonic plasma particle deposition, in which reactants introduced into a high-temperature plasma are supersonically expanded through a nozzle. This expansion drives nucleation of ultrafine particles, which are then collected on a substrate located downstream of the nozzle by inertial impaction. These researchers have been developing this process in two modes-for the deposition of continuous films over large areas and for the deposition of lines and patterns by using aerodynamic focusing to create collimated nanoparticle beams. Work has been developing models of the two-dimensional, compressible, reacting flow in the nozzle and in the free jet expansion between the nozzle and the deposition substrate, as well as models for particle transport and heat transfer from the nozzle to the substrate. It is further planned to model particle nucleation and growth in the nozzle and to model the aerodynamic focusing process. The latter requires the development of new modeling approaches as the low pressure at the exit of the focusing lens probably invalidates the assumption of continuum flow.
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