Functionality and Optimization of a Laminar Flow Reactor Utilizing Plasma Enhanced Atomic Layer Deposition

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Peter Falvo; Travis Wright
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Functionality and Optimization of a Laminar Flow Reactor Utilizing Plasma Enhanced Atomic Layer Deposition Peter Falvo1, Travis Wright2, Kevin Kellogg2, Shawn Lee2, Jing Wang21 Department of Mechanical Engineering2 Department of Electrical EngineeringKeywords: atomic layer deposition, chemical vapor deposition, nanotechnology, thin film deposition, plasma, ALD, CVD, Al2O3Atomic layer deposition (ALD) has been widely used in research laboratories and industry to grow pin hole free conformal thin films. Advantages of ALD films are highly controllable film thickness, high film purity, multi-layer structures, ease of doping films, and high aspect ratio. Unlike chemical vapor deposition (CVD), ALD is not dependent upon precursor flux upon the substrate surface, instead relying upon binary step-wise A + B = P synthesis. Standard ALD processes use thermal energy to create the desired chemical reactions via a substrate heater or a hot wall reactor. Plasma enhanced atomic layer deposition (PE-ALD) is an alternative ALD process that allow lower operating temperatures and better film characteristics. A homebuilt ALD system was constructed for the purpose of growing thin films on wafers up to 2” in diameter. Many researchers worldwide have reported relevant information of both homebuilt [1], [2], [3] and commercially available ALD reactors [4]. We have studied in detail, the relevant parts of their designs to improve the actual state of the art of PE-ALD system. Our design characteristics include an inert carrier gas, fast acting precursor valves, remotely generated inductively coupled plasma, high temperature substrate heater and a chamber with a high volume to surface ratio geometry. The functionality of this reactor includes three separate modes of operation: a thermal reaction mode (thermal ALD), an isolated chamber mode necessary for high aspect ratio substrates, and a plasma enhanced mode. System functionality and optimization was determined by comparing both thermal and plasma Al2O3 film of the homebuilt PE-ALD system to a commercially available ALD system. Optimization of the system was pursued by means of varying a number of controllable system parameters including substrate temperature, reactor pressure, reactor wall temperature, purge time, the amount of precursor used per pulse, and ion concentration at the substrate surface. Functionality of the homebuilt system was determined by comparing Al2O3 films to a commercial bought ALD system. Characterization of the Al2O3 films was done by means of CV curves, IV curves, and XPS. Future works for the system will include novel tunable nanolaminates for potential uses in super capacitors, and RF antennas. References:[1] J. W. Elam, M. D. Groner, and S. M. George, “Viscous Flow Reactor with Quartz Crystal Microbalance for Thin Film Growth by Atomic Layer Deposition,” Review of Scientific Instruments, Vol. 73 No. 8, Aug. 2002, pp. 2981-2987[2] H. C. M. Knoops, L. Baggetto, E. Langereis, M. C. M. van de Sanden, J. H. Klootwijk, F. Roozeboom, R. A. H. Niessen, P. H. L. Notten, and W. M. M. Kessels, “Deposition of TiN and TaN By Remote Plasma ALD for Cu and Li Diffusion Barrier Applications,” Journal of the Electrochemical Society, Vol. 155, No. 12, Oct 2008, pp. G287-G294[3] G. A. Ten Eyck, J. J. Senkevich, F. Tang, D. Liu, S. Pimanpang, T. Karaback, G. Wang, T. Lu, C. Jezewski, and W. A. Lanford, “Plasma-Assisted Atomic Layer Deposition of Palladium,” Chemical Vapor Deposition, Vol 11, No. 1, 2005, pp. 60-66.[4] S. B. S. Heil, J. L. van Hemmen, C. J. Hodson, N. Singh, J. H. Klootwijk, F. Roozeboom, M. C. M. van de Sanden, and W. M. M. Kessels, “Deposition of TiN and HfO2 in a Commercial 200mm Remote Plasma Atomic Layer Deposition Reactor,” Journal of Vacuum Science and Technology A, Vol. 25, No. 5, Sept/Oct 2007, pp. 1357-1366.