Integration of high dielectric Ba0.5Sr0.5TiO3 films into amorphous TaSiN barrier layer structures

The high- k dielectric material (Ba,Sr)TiO 3 has been intensively investigated for possible applications in dynamic random access memory circuits. During the BST deposition process in O 2 ambient, typically at 650°C, the diffusion of oxygen through the bottom electrode into the poly Si plug must be prevented. Amorphous TaSiN films are excellent candidates as oxygen barrier layers. Ba 0.5 Sr 0.5 TiO 3 (BST) films with thickness of 100 nm were deposited on the electrode structure SiO 2 /TaSiN/Pt. The sol–gel method was used to grow the BST films. The barrier effect for oxygen diffusion is studied in TaSiN layers with thickness of 50 nm, which were deposited by a reactive sputter process. X-ray photoemission spectroscopy results confirm that this amorphous material is a suitable barrier against oxygen diffusion at 650°C. The BST films, deposited at 650°C and post-annealed at 650°C show a dielectric constant of 100 at 100 kHz and a dissipation factor of less than 5%.