Microstructure and electrical characteristics of Ba0.65Sr0.35TiO3 thin films etched in CF4/Ar/O2 plasma

Radio frequency magnetron sputtered Ba0.65Sr0.35TiO3 (BST) thin films were etched in CF4/Ar/O2 plasma by magnetically enhanced reactive ion etching technique. The etching characteristics of BST films were characterized in terms of microstructure and electrical properties. Atomic force microscopy and X-ray diffraction results indicate that the microstructure of the etched BST film is degraded because of the rugged surface and lowered intensities of BST (1 0 0), (1 1 0), (1 1 1) and (2 0 0) peaks compared to the unetched counterparts. Dielectric constant and dielectric dissipation of the unetched, etched and postannealed-after-etched BST film capacitors are 419, 346, 37,0.01,0.039 and 0.031 at 100 kHz, respectively. The corresponding dielectric tunability, figure of merit and remnant polarization are 19.57%, 11.56%, 17.25%, 10.87, 2.96, 5.56, 3.62 muC/cm2, 2.32 and 2.81 muC/cm2 at 25 V, respectively. The leakage current density of 1.75 X 10-4 A/cm2 at 15 V for the etched BST capacitor is over two orders of magnitude higher than 1.28 X 10-6 A/cm2 for the unetched capacitor, while leakage current density of the postannealed-after-etched capacitor decreases slightly. It means that the electrical properties of the etched BST film are deteriorated due to the CF4/Ar/O2 plasma-induced damage. Furthermore, the damage is alleviated, and the degraded microstructure and electrical properties are partially recovered after the etched BST film is postannealed at 923 K for 20 min under a flowing O2 ambience.