PREPARATION OF PIEZOELECTRIC PZT THIN FILMS BY MOCVD FOR MEMS APPLICATIONS ING-SHIN CHEN*, DONG-JOO KIM**, JON-PAUL MARIA**, JEFFERY F. ROEDER*, AND ANGUS I. KINGON** *ATMI, Danbury, CT 06810, bchen(djatmi.com "**Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695 ABSTRACT Integration of piezoelectric Pb(Zr,Ti)0 3 (PZT) thin films promises to provide silicon-based microelectromechanical systems (MEMS) with added functionality. PZT films with compositions near the tetragonal/rhombohedral morphotropic boundary have been deposited on iridium-coated Si substrates by a thermal chemical vapor deposition (CVD) process using flash vaporized metalorganic precursors. Process variables including (A-site)-to-(B-site) ratios in the precursor mix and deposition times have been surveyed. Stoichiometric, perovskite films with nominal Zr/Ti ratios ranging from 40/60 to 60/40 were obtained. Parallel-plate capacitor structures have been fabricated by depositing Pt top electrodes using e-beam evaporation through shadow masks. Ferroelectric hysteresis loops were measured usin• a standard ferroelectric tester. Remenant polarization values in the range of 20-30 iLC/cmr were obtained. For films of 0.5 )im or thicker, piezoelectric hysteresis loops were characterized by dual-beam interferometry. Longitudinal piezoelectric coefficients (d 33 ) of 30-60 pm/V were observed on the films deposited between 550 and 600'C. INTRODUCTION Microelectromechanical Systems (MEMS) is an emerging field that has attracted much attention due to its potential to perform complex electromechanical functions in a miniature scale. Si-based MEMS has been the most rapid growing section of the development efforts because it benefits from the advance in integrated silicon microelectronics. At the same time, the need to incorporate piezoelectric materials for added functionality is being actively pursued [1,2]. ZnO and Pb(Zr,Ti)0 3 are two of the leading candidate materials for thin film piezoelectrics. Thin film ZnO is simple to fabricate but suffers from moderate piezoelectric responses and relatively high loss [3]. Pb(Zr,Ti)0 3 (PZT) with compositions near the morphotropic phase boundary are very promising due to their high piezoelectric coefficients, and there has been increasing emphasis on incorporating thin film PZT into MEMS devices. Solution deposition methods have been widely used to prepare thin film PZT piezoelectrics. Effective longitudinal piezoelectric coefficients d 33 approximately 60 pm/V are routinely obtained for submicron films at compositions near the tetragonal/rhombohedral morphotropic boundary (MPB) [4]. For many emerging MEMS applications, use of three-dimensional structures are very attractive or even essential to their innovative designs [5]. For these applications, metalorganic chemical vapor deposition (MOCVD) offers the enabling features needed for high performance piezoelectric coating: a unique combination of precise composition control, thickness uniformity, and conformality. Despite their excellent promises, there have been relatively few reports on piezoelectric properties of thin film PZT piezoelectrics by MOCVD. In an early effort, films prepared by MOCVD were shown to exhibit moderate longitudinal piezoelectric coefficients of 40 pm/V at compositions near the MPB [6]. Significant progress has since been made on MOCVD process 541 Mat. Res. Soc. Symp. Proc. Vol. 596 2000 M1etderIls Research Society