Etching characteristics and plasma-induced damage of Ba0.65Sr0.35TiO3 thin films etched in CF4/Ar/O2 plasma

Sol-gel-derived Ba0.65Sr0.35TiO3 (BST) thin films were etched in CF4/Ar/O-2 plasma using magnetically enhanced reactive ion etching technology. The maximum etch rate of BST film is 8.47 nm/min when CF4/Ar/O-2 gas mixing ratio is equal to 9/36/5. X-ray photoelectron spectroscopy analysis indicates the accumulation of fluorine-containing by-products on the etched surface due to their poor volatility, resulting in (Ba,Sr)-rich and (Ti,O)-deficient etched surface. Compared to the unetched counterparts, the etched Ba 3d(5/2), Ba 3d(3/2), Sr 3d(5/2), Sr 3d(3/2), Ti 2P(3/2), Ti 2p(1/2) and O 1s photoelectron peaks shift towards higher binding energy regions by amounts of 1.31, 1.30, 0.60, 0.79, 0.09, 0.46 and 0.50 eV, respectively. X-ray diffraction (XRD) analysis reveals that intensities of the etched BST (100), (110), (200) and (211) peaks are lowered and broadened. Raman spectra confirm that the Raman peaks of the etched film shift towards lower wave number regions with the values of 7, 6, 4 and 4 cm(-1), and the corresponding phonon lifetimes are longer than those of the unetched film because of the plasma-induced damage. When the etched films are postannealed at 650 degrees C for 20 min under an 02 ambience, the chemical shifts of Ba 3d, Sr 3d, Ti 2p and O 1s peaks, the variations for atomic concentrations of Ba, Sr, Ti and 0, and the Raman redshifts are reduced, while the corresponding XRD peak intensities increase. It is conceivable that the plasma-induced damage of the etched film could be partially recovered during the postannealing process. (c) 2007 Elsevier B.V. All rights reserved.