Formation of Al2 O 3 ‐ Ta2 O 5 Double‐Oxide Thin Films by Low‐Pressure MOCVD and Evaluation of Their Corrosion Resistances in Acid and Alkali Solutions

Abstract

double‐oxide thin films with different cationic mole fractions of Ta, , were formed by metallorganic chemical vapor deposition using aluminum tetraisopropoxide and tantalum pentametoxide as source gases and oxygen as a reaction gas. The corrosion resistances of the films were examined in 6 and 12 M HCl and 1 M NaOH at 298 K by the ellipsometric measurement of thinning rates of the films. The films having values between 0.0 and 1.0 showed homogeneous amorphous structures. The thinning rate of the films in HCl solutions decreased with increasing value and reached the analytical limit of ellipsometry. The films with values larger than 0.35 hardly dissolved in 6 M HCl and those with values larger than 0.45 in 12 M HCl. The corrosion resistance of the films in 1 M NaOH increased significantly with an increase in : the dissolution rate of the film with value of about 0.5 is lower than that of pure film by six orders of magnitude. © 1999 The Electrochemical Society. All rights reserved.