Chemical vapor deposition of barium strontium titanate films with direct liquid injection of single-mixture solution

Abstract

Chemical vapor deposition of barium strontium titanate (BST) thin films with direct liquid injection of a single-mixture solution of Ba(tmhd)(2)-Lewis base adduct (tmhd = 2,2, 6,6-tetramethyl-3,5-heptanedionate), Sr(tmhd)(2)-Lewis base adduct, and Ti(i- OPr)(2)(tmhd)(2) (i-OPr = iso-propoxide) was studied. Thermal characteristics of Ba and Sr precursor adducts with tetraethylene glycol dimethyl ether(tetraglyme) and pentamethyldiethylene triamine (PMDT) were compared. Using differential scanning calorimetry, the coordination of PMDT with metal-tmhd compound was found to be stronger than tetraglyme, and the thermal stability of Sr(tmhd)(2)-A (A = tetraglyme or PMDT) was higher than Ba(tmhd)(2)-A. The optimum window of the vaporizer temperature of PMDT adduct was wider than the tetraglyme adduct. Ba and Sr incorporation into (Ba,Sr)TiO3 mms was about the same for both adducts. Ti incorporation was increased up to the deposition temperature (T-s) of 470 degrees C and some humps and hazy deposition were detected below 470 degrees C due to the lack of Ti incorporation. Step coverage of (Ba,Sr)TiO3 films was about 0.8 at the T-s of 480 degrees C and 0.3 at 550 degrees C. Leakage current and the equivalent oxide thickness at 1.0 V were about 10(-7) A/cm(2) and 0.96 nm at the deposition temperature above 470 degrees C. (C) 1999 The Electrochemical Society. S0013-4651(99)02-001-7. All rights reserved.