MOCVD法によるPLZT超薄膜の作製とDRAMキャパシターとしての基礎特性

抄録

Lanthanum-modified lead zirconate titanate (PLZT) thin films (50-200nm) were deposited on Pt/SiO₂/Si substrate by metalorganic chemical vapor deposition (MOCVD). The electrical properties of the films were investigated as a function of the La content or the substrate temperature. Ferroelectric PZT (0/50/50) films were obtained at a substrate temperature as low as 500°C, and their electric characteristics were improved with increasing substrate temperature. La was adequately solid-dissolved into the PZT above 650°C. PLZT (15/45/55) films having a thickness of 100nm were found to have good properties for application to capacitors of dynamic random access memory, (DRAM), i, e., effective charge density of 80fF/μm², dielectric constant of 1000, SiO₂ equivalent thickness of 0.4nm and leakage current density of 5×10^-8A/cm². La addition to PZT was effective in reducing the leakage current with an increase in the registration rate. RuO₂ and IrO₂ bottom electrodes for ferroelectric PLZT films were also investgated. The RuO₂ films were found to serve as effective diffusion barriers for NIT and MgO. Significant interdiffusion at RuO₂/Si and RuO₂/SiO₂ interfaces occurred during the deposition of PLZT films, and annealing of RuO₂ film considerably depressed the interface reactions.