A low-pressure plasma is a unique state of a gas in which chemically active species coexist with free charge carriers. Plasmas are produced by applying electric fields to gases under low pressures of a few Pascal to several hundreds of Pascal. Plasma processes are widely used in microelectronics processing for the etching of sub-micrometer structures and the deposition of thin films. About 40% of the total number of processing steps of modern microprocessors and RAMs rely on low-pressure plasma processes.
Upendra Bhandarkar, Graduate Student Researcher
C. Eggs, Graduate Student Researcher
Chenbin He, Graduate Student Researcher
Vitaly A. Schweigert, Research Associate
Eli Kostadinova Stoykova, Supercomputing Institute Research Scholar
Mark Swihart, Graduate SUNY, Buffalo, New York
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"Kinetic Two-Dimensional Modeling of Inductively Coupled Plasmas Based on a Hybrid Kinetic Approach," U. Kortshagen and B. Heil, IEEE Transactions on Plasma Science, 27, p. 1297 (1999). |
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"Energy-Resolved Electron Particle and Energy Fluxes in Positive Column Plasmas," U. Kortshagen and J.E. Lawler, Journal of Physics D: Applied Physics, 32, p. 2737 (1999). |
99/188 |
"Kinetic Modeling and Experimental Studies of Large-Scale Low-Pressure RF Discharges," U. Kortshagen and B. Heil, University of Minnesota Supercomputing Institute Research Report UMSI 99/188, October 1999. Publication in press. |
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"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. |
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"Self-consistent Monte Carlo Simulations of the Positive Column of Gas Discharges," J.E. Lawler and U. Kortshagen, Journal of Physics D: Applied Physics, 32, p. 3188 (1999). |
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"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). |
The increasing speed of new developments in semiconductor processing requires fast design of new plasma processing equipment. Currently, the design phase of a new plasma processing tool, which costs several million dollars, is limited to eighteen months-its typical lifetime lasts for about three years. The development of new plasma processing equipment proceeds mostly empirically since no predictive computer aided design tools are currently available. The problems in computer modeling of plasmas are based on the presence of multiple species and the pronounced thermodynamic non-equilibrium of low-pressure plasmas. While heavy particles (ions and neutral gas atoms) have temperatures close to room temperature, the mean kinetic energy of the free plasma electrons is of the order of a few electronvolt (i.e., their temperature is several 10,000 Kelvin). The precise prediction of plasma-chemical reaction rates requires the accurate knowledge of the electron energy distribution function (EEDF).
These researchers are focusing on the development of new, efficient methods for the calculation of the EEDF by approximate solution of the Boltzmann equation. To gauge the accuracy of these approximation methods, comparisons to rigorous methods based on first principles are necessary. A fully self-consistent Monte Carlo code has recently been developed to calculate the EEDF in a low-pressure plasma system. This code is an MPI-parallel code that has been developed on the IBM SP. Studies of DC glow discharges are being continued with this code as a benchmark system, and testing of the accuracy of approximation methods is being done to solve the Boltzmann equation.
These researchers are also developing models for the nucleation, growth, and transport of nanometer-sized particles in processing plasmas. Currently, models for spatially one- and two-dimensional systems are under development.
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