Crystallographic and morphological properties of magnetron sputtered Ti and Zr thin films
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Crystallographic and morphological properties of magnetron sputtered Ti and Zr thin films Eliane F. Chinaglia, Ivette C. Oppenheim Universidade de São Paulo, Instituto de Física PO Box 66318, 05315-970 São Paulo, SP, Brasil ABSTRACT Crystallographic and surface morphological characteristics of polycrystalline hcp Ti and Zr thin films were studied as a function of the homologous substrate temperature TS /TM and the thickness t of the films (28 nm t 380 nm). TS is the substrate temperature during deposition and TM is the melting point of the film's material. For the whole range of considered temperatures (0.14 TS / TM 0.48) Zr films presented a {0002} crystallographic orientation. As TS / TM increased, Ti films suffered a transition from a columnar grain structure with {0002} preferential crystallographic orientation to a cone-like-shape grain structure with {10 1 1} preferential crystallographic orientation. Our results suggest that Zr films suffer a structural transition from Zone T to Zone II at temperatures similar to those predicted by Thornton's Structure Zone Model for thick films while Ti films do not have a microstructure typical of Zone II even for relatively high values of TS / TM, presenting a transition from Zone I to Zone T in the studied range of temperatures. INTRODUCTION It is well known that the deposition technique and deposition parameters used for processing films have a strong influence on the films' structure (size, shape and crystallographic orientation of grains, grain boundaries characteristics, etc.), and that the structure on its turn has a strong influence on the physical and chemical properties of the films [1-4]. Structure Zone Models (SZM) [5-8] describe empirically the grain morphology of physical-vapor-deposited films. SZM are based on the characterization of e-beam [5, 7, 9] and sputter-deposited films [6, 8, 10] as a function of TS/TM. In case of sputter-deposited films, the morphological characteristics as a function of the Ar working gas partial pressure are also considered. Effects of impurities on thermally evaporated films [8, 11], and descriptions of structure evolution considering the grains' crystallographic orientation have been recently proposed by many authors [8, 11-13]. In this work we study crystallographic and morphological properties of sputter-deposited Ti and Zr films with 28 nm W nm, and prepared with 0.14 TS / TM 0.48. Thickness and impurity contents of the films were determined with Rutherford Backscattering Spectroscopy (RBS), and Nuclear Resonant Analysis (NRA). Degree of crystallographic orientation and crystalline grain size were obtained with θ-2θ X-ray Diffraction (XRD). Average grain diameter at the film's surface was estimated using Atomic Force Microscopy (AFM).
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EXPERIMENTAL PROCEDURE Ti and Zr films were deposited on amorphous substrates by DC magnetron sputtering in a commercial deposition system from AJA International - model ATC 2000. Substrates of Si (100) covered with an amorphous SiO2 layer (t ~ 300 nm) were used.
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