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Optical and Discharge Physics
^ Startup Processes in Metal Halide Lamps
J. G. Eden, M. J. Kushner, T. Sommerer (GE)
General Electric R&D Center

High pressure, metal halide lamps are typically the lighting sources used for street lamps, stadiums, warehouses, and other large indoor arenas. Metal halide lamps start as room temperature, glow discharges. Upon heating, metal-halide compounds in the lamps vaporize to generate multi-atmosphere pressure plasmas, which then produce nearly continuum radiation. The starting process usually involves applying high-voltage pulses to tens to one hundred Torr of Ar gas with a small admixture of mercury or another low ionization potential rare gas. Optimizing this process will ultimately produce longer lived, more reliable lamps. In this research project, advanced computer modeling and laser diagnostics are being used to investigate the fundamental plasma processes which occur during startup of metal-halide lamps. Of particular interest are the plasma-surface interactions on the cathode that result in sputtering of cathode materials. Methods to minimize sputtering without using costly exotic materials are being formulated.

^ Advanced Plasma Equipment: Design and Optimization
M. J. Kushner,* R. Kinder, D. Zhang, J. Lu, A. Sankaran, P. Subramonium
Applied Materials Corp.

Computer simulations of plasma equipment for microelectronics fabrication have advanced to the point that new generations of equipment can be virtually designed and optimized prior to hardware prototyping. In a cooperative research program with Applied Materials Corp., plasma equipment models developed at the University of Illinois are being used to design new etching and deposition reactors. Emphasis is being placed on magnetically enhanced reactive ion etching (MERIE) and ionized metal physical vapor deposition (IMPVD) reactors. New computational algorithms are being developed and applied to the task.

^ Hollow Cathode Magnetron Metal Deposition
M. J. Kushner,* J. Lu
Novellus, Inc.

The wiring pathways in advanced microelectronics devices are becoming smaller (2 mm) and will have vias with progressively larger aspect ratios. Filling these pathways with metal is therefore becoming problematic. The pathways can be filled using ionized metal physical vapor deposition (IMPVD), by which sputtered metal atoms are ionized and vertically accelerated into the vias. The next generation of microelectronics devices will use copper interconnect wiring, and so techniques for copper IMPVD must be developed and optimized. In this project, computer models of copper IMPVD using an advanced hollow-cathode plasma source are being developed. The models are being used to investigate the unique quasi-magnetized plasma hydrodynamics of these devices and so improve their performance.

^ Modeling of Plasma Equipment for Microelectronics Fabrication
M. J. Kushner,* R. Kinder, J. Lu, V. Vyas, A. Sankaran, P. Subramonium
Semiconductor Research Corp.

Of the hundreds of processing steps in the manufacture of silicon microelectronics devices such as memory chips and microprocessors, approximately one-third use plasmas for etching, deposition, cleaning, or passivation. As wafer sizes continue to increase, the need for highly uniform, particle-free plasma-processing equipment also increases. In this project, researchers are developing plasma equipment models (PEMs) to study important plasma generation and transport processes and to investigate methods to scale plasma reactors to process larger wafers. The PEMs are geometrically flexible and are able to address a variety of chemistries. Particular attention is being paid to processes which generate particle contamination of the wafers and to coupling plasma transport codes to feature profile simulators.

^ Plasma Crystals
M. J. Kushner, V. Vyas, G. Hebner (SNLA)
Sandia National Laboratories

Plasmas are multicomponent systems consisting of electrons and ions as charged particles, and atoms, molecules, and radicals as neutrals. By virtue of their high mobilities, it is difficult to form identifiable thermodynamic phases of these species in plasmas. However, when small solid particles (a few microns in size) are added to plasmas, unique thermodynamic phases are created, called plasma crystals. When immersed in a plasma, small particles acquire electrical charge, which then allows them to interact with the electric fields and other charged species in the plasma, including themselves. Plasma fluids and crystals that have properties similar to conventional crystals are the end result. In this research project, computer simulations are being developed to investigate the fundamental properties of plasma crystals, and experiments are being conducted at Sandia National Laboratories to validate the models.

^ Plasma Remediation of Diesel Exhaust
M. J. Kushner,* R. Dorai, J. Hoard (Ford)
Ford Motor Co.

More stringent regulations on the allowable levels of toxic gases in the exhausts from internal combustion engines have motivated research into more efficient methods to treat those gas streams. Researchers are developing reaction mechanisms multidimensional plasma chemistry models to investigate plasma remediation as a method to remove toxins from atmospheric pressure gases and diesel exhaust in particular. In plasma remediation, electron impact reactions produce oxidizing or reducing radicals that either convert the toxin to a harmless gas or to a gas for which conventional remediation methods can be used. The research team is investigating reaction mechanisms and the plasma hydrodynamics in dielectric barrier and corona discharges for remediation of NOx. Scaling laws for energy efficiency are being developed.

^ Plasma-Surface Interactions for Polymer Treatment
M. J. Kushner, R. Dorai, A. Sankaran, M. Mastrobel (3M)
3M Inc.

Plasma treatment of polymers is an increasingly important industrial process to modify surface properties for wetability and functionality. In this collaborative research project, fundamental processes in the corona treatment of polymers are being investigated by computer modeling. In this treatment method, atmospheric pressure plasmas are used to create gas phase radicals, such as oxygen atoms or hydroxyl molecules, which then functionalize the surface. Of particular interest are treatment methods that can be used on temperature sensitive materials.

^ Radiation Transport in Low Pressure Plasma Lamps
M. J. Kushner, K. Rajaraman, G. Lister (Osram-Sylvania)
Osram Sylvania

Plasma-based lamps are the most efficient sources of artificial indoor and outdoor lighting. Most low pressure plasma lamps generate ultraviolet radiation which is converted to the visible through phosphors. The transport of this UV radiation through the plasma is important to the lamp's efficiency. In this research project, simulations of radiation transport are being developed using Monte Carlo techniques. The radiation transport models are being incorporated into comprehensive plasma equipment simulators to assess the consequences of radiation transport on the lamp's performance. These models are also being used to assess new designs for low pressure plasma lamps, and to determine the limiting processes for efficiency and improved lifetime.

^ Simulations of Three-dimensional Transport and Transients in Plasma Processing Reactors Using Moderate Parallelism
M. J. Kushner,* R. Kinder, J. Lu, A. Sankaran, P. Subramonium
National Science Foundation, CTS-99-74962

The manufacture of microelectronics devices uses a large variety of plasma sources for etching, deposition, and cleaning. Although a high degree of uniformity of processing across 20 to 30 cm diameter wafers is required, many of the plasma sources used, such as helicons and ECR, inherently have 3-D properties. In this research project, 3-D hybrid plasma hydrodynamic and plasma chemistry models are being developed and applied to the investigation of these multidimensional transport processes. Moderately parallel algorithms are being developed to enable simultaneous generation and utilization of electron energy distribution functions within the hybrid hierarchy. In doing so, long-term phenomena, such as start-up and shut-down transients, and recipe changes will be addressed.


Summary of Engineering Research