| AVS 57th International Symposium & Exhibition | |
| Vacuum Technology | Tuesday Sessions |
| Session VT-TuP |
| Session: | Vacuum Technology Poster Session and Student Posters |
| Presenter: | K. Kellogg, University of South Florida |
| Authors: | K. Kellogg, University of South Florida P. Falvo, University of South Florida S. Lee, University of South Florida T. Wright, University of South Florida J. Wang, University of South Florida |
| Correspondent: | Click to Email |
A plasma enhanced atomic layer deposition reactor (PE-ALD) was built for the purpose of growing thin films on wafers up to 2.5” in diameter. Internationally, papers have been published describing characteristics of both homebuilt [1,2,3] and commercially available ALD reactors [4]. The construction of this reactor was strategically designed using these descriptions, within an allowable project time and budget. Design characteristics include an inert carrier gas, millisecond speed precursor valves, a remotely generated inductively coupled plasma, and a chamber with a high volume to surface ratio geometry. The reactor will act to complement and increase the current application repertoire versus our commercially available reactor located in the University’s thin films laboratory. In this regard, the chamber must be optimized to accommodate unique recipe applications currently unattainable with the in-house system. The functionality of this reactor will include three separate modes of operation: a thermal reaction mode (thermal ALD) for use with general recipe applications, an isolated chamber mode necessary for high aspect ratio substrates, and a plasma enhanced mode (plasma enhanced ALD) for greater process recipe versatility such as metals and nitrides. ALD allows for a precision unattainable with other deposition processes. Unlike CVD, ALD is not dependent upon precursor flux upon the substrate surface, instead relying upon step-wise A + B = P synthesis. Reactor characteristics such as laminar gas flow and plasma ion locality concentration and intensity will be modeled with COMSOL finite element simulations. ALD deposition cycle times are optimized according to ALD chemical reactions and by in-situ monitoring of sample growth rates by means of fiber optic spectroscopy. Important considerations included an optimized pumping rate and a minimization of unavoidable deposition upon all surfaces other than the process wafer. Process optimization was also pursued by means of vacuum gauge feedback and automation of precursor valve cycle sequence by means of a Lab View enabled PC. Other automated controllable growth parameters include substrate heater temperatures, reactor wall temperatures and the energies of plasma ion bombardment upon the substrate surface species. Safety concerns have also been addressed by ensuring suitable gas exhaust, pump maintenance, hard-wired safety valve shut-off programming and gas cylinder and hazardous materials safety training of individual users. The chamber design, multitude of process optimizations, and comparisons with existing designs and models allow for substantial research parameters to be explored and discussed.
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.