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Title:Magnetic mitigation of energetic ions for extreme ultraviolet lithography sources
Author(s):Elg, Daniel
Advisor(s):Ruzic, David N.
Department / Program:Nuclear, Plasma, & Rad Engr
Discipline:Nuclear, Plasma, Radiolgc Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Extreme Ultraviolet (EUV)
Collector Optics
Debris Mitigation
Magnetic Mitigation
Abstract:For decades, the semiconductor industry has followed a trend known as Moore’s Law by doubling the number of transistors that can fit on a given area every two years. Moore’s Law has been obeyed with remarkable reliability. Now, however, the future of Moore’s Law is in doubt, as current methods of semiconductor manufacturing have reached their limits. The widely-used manufacturing process of lithography currently makes use of 193nm light, which is approximately an order of magnitude greater than the smallest feature size, 22nm. The use of 193nm light to etch such small features is done with advanced techniques that come at a great cost of money and time. Continued observance of Moore’s Law will only require this disparity to continue growing in the future, adding even more cost and difficulty to the semiconductor manufacturing process. A new wavelength of light is necessary to avoid this problem. The use of 13.5nm Extreme Ultraviolet (EUV) light for lithography presents a solution. Switching to this wavelength would enable many of the expensive advanced techniques to be abandoned. It would also allow for a smaller resolution without as much reduction in depth-of-focus. However, EUV cannot be produced by lasers. Instead, it must be produced by highly-ionized, energetic (20-30eV) plasmas. Additionally, no materials are known to easily transmit EUV. All EUV light must be collected by a collector optic mirror, which cannot be guarded by a window. The plasmas used in EUV lithography sources expel high-energy ions and neutral particles, which degrade the quality of collector optics. The mitigation of this debris is one of the main problems facing potential manufacturers of EUV sources. The use of magnetic fields to deflect ionic debris has been proposed and is investigated here. In this thesis, a detailed computational model of magnetic mitigation is presented, along with experimental results that confirm the correctness of the model. For the first time, trajectories of ions under significant magnetic deflection are modeled and verified. In a z-pinch gas discharge EUV source, measured ion energy distribution functions were used to predict deflection under the field of a 0.9T permanent magnet. Experimentally, ions of 4.3keV were deflected by 35° into a detector with an entrance orifice covering 0.07°. Ions of 2.2keV were deflected by 45° into the same detector. This detector also measured no ions at 0° with the magnetic present. The peak energies and distributions of experimentally-observed deflected ions were in agreement with the simulation. The simulation is easily adaptable to any EUV source and any well-modeled magnet, regardless of source or magnet topology.
Issue Date:2013-05-24
Rights Information:Copyright 2013 Daniel Elg
Date Available in IDEALS:2013-05-24
Date Deposited:2013-05

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