Laser Annealing of Ferroelectric SrBi 2 Ta 2 O 9 , Pb(Zr X Ti 1-X )O 3 and CeMnO 3 Thin Films
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Laser Annealing of Ferroelectric SrBi2Ta2O9, Pb(ZrXTi1-X)O3 and CeMnO3 Thin Films N.M. Sbrockey1, J.D. Cuchiaro1, L.G. Provost1, C.E. Rice1, S. Sun1, G.S. Tompa1, R.L. DeLeon2 and T.S. Kalkur3 1 Structured Materials Industries, Incorporated, 201 Circle Drive North Piscataway, NJ 08854, USA 2 AMBP Tech Corporation, 1576 Sweet Home Road Amherst, NY 14228, USA 3 Dept. of Electrical and Computer Engineering, University of Colorado Colorado Springs, CO 80918, USA ABSTRACT Excimer laser annealing studies were conducted of SrBi2Ta2O9, Pb(ZrxTi1-x)O3 and CeMnO3 thin films. The main incentive was to develop a low temperature process for SrBi2Ta2O9 thin films, which typically require a 750 C anneal to crystallize and achieve optimum ferroelectric properties. The results show that room temperature laser annealing can crystallize SrBi2Ta2O9, with a strong (200) preferred orientation. The Pb(ZrxTi1-x)O3 and CeMnO3 thin films investigated in this study were crystalline as deposited. Laser annealing of the Pb(ZrxTi1-x)O3 and CeMnO3 films did not result in a significant increase in crystallinity, as evidenced by the intensities of the x-ray diffraction peaks. Electrical characterization of laser annealed SrBi2Ta2O9 thin films showed good dielectric properties and the onset of ferroelectric behavior. Low temperature laser annealing is shown to be a viable approach to enable integration of ferroelectric SrBi2Ta2O9 films with silicon based micro-electronics, for ferroelectric memory applications.
INTRODUCTION Ferroelectric random access memory (FeRAM) devices offer the potential for high-speed and low-voltage operation, as compared to traditional non-volatile memory devices, such as flash memory and EEPROM [1]. FeRAM technology is currently being developed for both stand alone memory products and embedded memory for logic devices [2]. SrBi2Ta2O9 (SBT) and Pb(ZrxTi1-x)O3 (PZT) are presently the leading contenders for the ferroelectric material in FeRAM applications [3]. Cerium manganese oxide (CMO) is a promising new ferroelectric material, which is presently being investigated. Of these materials, PZT is the most well established technology. SBT offers the potential for lower voltage operation and better fatigue performance than PZT [4]. However, SBT films require a post deposition anneal of 700 C to 800 C in an oxidizing environment, in order to achieve optimum ferroelectric properties [5]. This high temperature anneal step is incompatible with present silicon CMOS fabrication. In this work, we investigated the use of excimer laser annealing, to selectively heat and crystallize ferroelectric oxide thin films on silicon substrates. We focused our investigation on SBT, since there is an immediate need for low temperature processing of SBT for FeRAM applications. For PZT, It is well established that thin films can be prepared with suitable ferroelectric properties at temperatures below 550 C [5]. Crystalline CMO thin films have also
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been prepared at Structured Materials Industries, at temperatures compatible with
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