Deposition, Annealing, and Characterization of Tantalum Pentoxide Films
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DEPOSITION, ANNEALING, AND CHARACTERIZATION OF TANTALUM PENTOXIDE FILMS H. Treichel 1, A. Mitwalsky 2, G. Tempel 2, G. Zorn 2 ,W. Kern 3, N. Sandier 4, A.P. Lane 5 1 Siemens AG, Semiconductor Group, Process Engineering and Support, 8900 Munich Germany 2 Siemens AG, Corporate Research and Development, 8900 Munich, Germany 3 Werner Kern Associates, East Windsor, 08520, NJ, USA 4 Lam Research Corporation, Fremont, 94538, CA, USA 5 Texas Instruments, SPL, Dallas, 75265, TX, USA
ABSTRACT Films of tantalum pentoxide (Ta 2 0 5 ) have been fabricated by use of different precursor materials, deposition techniques and annealing procedures. Several analytical methods were applied to study the layers. Fundamental properties and new data are reported and related to practical features that are of importance in device design and manufacturing of advanced, highly integrated devices. This overview may facilitate the choice of an optimal combination of precursor, deposition technique and corresponding annealing procedure for a specific application of these films in microelectronics, since the electrical properties reveal the potential of Ta 2 0 5 films for the use in 64Mbit and 256Mbit DRAM devices as high dielectric constant material.
I. INTRODUCTION Films of dielectric materials offer a great variety of applications in semiconductor device technology, e.g., as etching-masks, barrier layers, gate oxide, varactor dielectrics, separation of active and passive components, electrical isolation between conductive regions. For storage capacitor dielectrics in advanced ULSI silicon devices a high dielectric constant is needed in order to replace the conventionally used thin (< 5nm) Si02 or ONO (silicon-oxide/-nitride/-oxide) films by thicker dielectrics which can be deposited much more easily and reliably [1-6,12,14,16,19,32]. Several metal oxides such as Ta 2 0 5 , Nb2 0 5 , A12 0 3 , Y2 0 3 , HfO 2 , ZrO 2 , and TiO 2 , have dielectric constant values (6r) ranging from 10 to 100 (depending on material, microstructure, crystalline phase, and crystal orientation) and provide a near-term solution for future ICs, such as the 64Mbit DRAM, the 256 Mbit DRAM and the 1Gbit DRAM [1,35,37,39]. The application of these alternative dielectrics to three-dimensional device structures (i.e., trench-cells) greatly reduces the cell area [19]. However, the films must maintain their electrical, physical, and chemical properties during subsequent device processing. In this paper we present new data for tantalum pentoxide, the most extensively developed high dielectric constant metal oxide (Er - 25) and relate some of its fundamental properties to practical features that are of importance in device design and manufacturing. Mat. Res. Soc. Symp. Proc. Vol. 282. ©1993 Materials Research Society
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II.EXPERIMENTAL II.A. Film Deposition Methods and Annealing Techniques The Ta 2 0 5 films were deposited by use of various organometallic precursors, consisting of metal alkoxides. Various deposition techniques were used, including plasma enhanced chemical vap
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