. I' RECEIVED MAR 2 5 8% CHEMICAL SOLUTION DEPOSITION OF SrBi,Ta,O, (SBT) FILMS FOR NON-VOLATILE MEMORY APPLICATIONS OSTI CHARLES D.E. LAKEMAN", TIMOTHY J. BOYLEb, JUDITH A. RUFFNERb, MARK A. RODRIGUEZc aTexas Instruments, Inc., P.O. Box 655012, Mail Stop 921, Dallas TX75265.; Sandia National Laboratories, Advanced Materials Laboratory, 1001 University Blvd., SE, Albuquerque, NM 87 106; "Sandia National Laboratories P.O. Box 5800,Mail Stop 1405, Albuquerque, NM 87185-1405 ABSTRACT SrBi2Ta2Oc~ (SBT) films have received considerable attention for use as non- volatile memory elements. We have developed a process to prepare SBT films with good ferroelectric properties at low temperatures. In this paper, we will present strategies used to optimize the properties of the films including film composition, the nature of the substrate (or bottom electrode) used, and the thermal processing cycle. Under appropriate conditions, -1700A films can be prepared which have a large switchable polarization (2P, >10pC/cm2), and an operating voltage 12.0V. Kevwords: SrBi2Ta209 (SBT), thin film, substrate,, composition, processing INTRODUCTION In the search for ferroelectric materials for use as non-volatile memory elements, the bismuth layered perovskites, such as SrBi,Ta,09 (SBT) have emerged as leading candidates owing to their remarkable polanzation fatigue resistance [l, 2, 3, 41. Much research has been directed at tailoring processing conditions to optimize microstructure and properties for use in such devices [5]. Ideal target parameters are: switchable polarization, 2P,, 2 10pC/cm2;coercive voltage, V,, <1V; and operating voltage (defined as the voltage at which 80% of the switchable polarization can be switched) 12V. These parameters indicate the need for thin films (12000A) for device applications. In addition, to be compatible with standard CMOS circuitry, maximum processing temperatures should not exceed 700°C. In order to test the feasibility of SBT for such applications, many researchers have turned to chemical solution deposition (CSD) as a straightforward, rapid method of preparing thin films [6,7]. From the various deposition technologies available, several common features emerge: either complex solution preparation is required to solubilize all components, or high L. a3 a3 0 * 0