Effect of growth and annealing temperatures on crystallization of tantalum pentoxide thin film prepared by RF magnetron sputtering method

Abstract

Crystalline tantalum pentoxide thin films have higher dielectric constants, and optical indices than in amorphous form. High temperature processes above 850 °C are generally required in previous researches. In this study, we investigate the effect of substrate heating and annealing temperatures as well as the target selection on crystallization of tantalum pentoxide thin film by RF magnetron sputtering method. Both metal tantalum and ceramic tantalum pentoxide targets are used as the substrate (silicon) temperature is varied. X-ray diffraction (XRD), field-emmision scanning electronic microscope (FESEM), ionic force microscope (AFM) and X-ray photoelectron spectroscope (XPS) measurements are carried out to identify the crystalline structure, surface morphology and chemical composition. The tantalum pentoxide thin films are amorphous when the substrate is not heated for either target. When the metal tantalum target is used, minor crystallization does take place if post-deposition annealing above 700 °C is applied. In general, the higher temperature the better oriented structure can be obtained. Finally, at reduced substrate temperature (400 °C) finely preferred oriented thin film can be directly deposited with the ceramic target in pure oxygen atmosphere even without annealing. The crystalline structure is identified as orthorhombic structure and the perfect chemical stoichiometric composition is also confirmed.