Depth Profiling of Solution-Deposited Lead Zirconate Titanate Thin Films by Radio Frequency Glow Discharge Atomic Emissi
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Mat. Res. Soc. Symp. Proc. Vol. 596 © 2000 Materials Research Society
compositional depth profiling of PZT thin films fabricated by a chemical solution deposition method. In order to address the need for information on the compositional aspects of the films and device structures, we have investigated the use of the radio frequency glow discharge atomic emission spectroscopy (rf-GD-AES) technique [5-8]. Rf-GD-AES is a relatively new technique that permits the depth-resolved elemental analysis of metallic, semi-conducting, and insulating materials over depths of 20 nm - 150 .tm in a rapid fashion (< 0.1 - 5 g.m/min). The approach can be viewed as simply the analytical implementation of rf sputter etching, where the atomized material is analyzed by its characteristic optical emission. In this paper, we report the use of radio frequency glow discharge atomic emission spectroscopy to profile Pb, Zr, Ti, 0, and C stoichiometry in chemical solution deposited (CSD) PZT thin films. In this application, elemental analyses (including remnants of the organic deposition precursors) provide easily interpreted information regarding the chemical composition and physical structure of the layered systems. The comparatively large sampled spot size (-4 mm diameter circle) of this method may be prohibitive in the analysis of actual devices (due to the small, micron-scale size features that are often present), however its use in process development is of benefit, as the method provides rapid feedback on both the chemical and structural aspects of the primary layered materials, as well as device issues such as interdiffusion with the electrode stack. EXPERIMENTAL The PZT(53/47) films based on the chemical formula Pbl 1(Zr.53Ti. 47)0 3 examined in this study were fabricated by a chemical solution deposition process (CSD). The chemistry of the multicomponent solution was based on an aqueous acetate PZT system used by Webb [9] and Francis [10]. A 0.8M Pb-Zr-Ti solution was prepared by combining titanium isopropoxide (TIP) with glacial acetic acid (HOAc) (15:1 molar ratio HOAc:TIP) in a dry nitrogen glove box. After 10 minutes stirring, the TIP/HOAc solution was then combined with distilled water (32:1 H2 0: TIP). The hydrolyzed precursor formed a white precipitate which was dissolved under ultrasonic agitation for 45 minutes. Zirconium acetylacetonate, Zr(OC(CH 3)CHCOCH 3)4, and lead acetate trihydrate, Pb(OCOCH 3)2 3H20, powders were then added to the TIP/HOAc/water solution and refluxed under constant stirring for approximately 1 hour. The PZT solution was then split in two portions and one was modified with hydrogen peroxide, H20 2 (10% by volume). Films were prepared on Pt coated silicon substrates (Pt/Ti/Si0 2/Si) by spin coating at 3000 rpm for 30 seconds. After deposition, solvent removal and organic pyrolysis were accomplished by heat treatment at -300'C for 5 minutes on a hot plate. Two layers, - 100nm per-layer after firing, were deposited and pyrolyzed followed by firing at higher temperatures. The films of PZT and PZTH (p
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