Thermal stability and electrical properties of SrBi2Ta2-xNbxO9/IrOx capacitors with Pt top electrode

Abstract

Both SrBi2Ta2-xNbxO9 (SBTN) film and IrOx electrode were used for fabricating a capacitor of high-density ferroelectric random access memory. IrOx was deposited by reactive sputtering, and the spin-on technique was used for coating the SBTN layer. Marked evaporation was observed in 2000-Angstrom -thick IrOx film after electrode annealing at temperatures above 700 degreesC. The evaporation was caused by the reduction of IrOx to metallic iridium. However, SBTN/IrOx stack remained stable even after annealing up to 800 degreesC. Ferroelectric crystallization annealing during the integration was performed at 650 degreesC for the application of stacked capacitor architecture. Thus, the Pt/SBTN/IrOx capacitor could be fabricated up to metallization without damaging the microstructure, The switching polarization was about 10 muC/cm(2) at the 2.4 mum x 3.7 mum x 256 ea array capacitor after metallization and the leakage current density was about 4 x 10(-7) A/cm(2) The contact resistance of the SBTN/IrOx/Ir/TiN/plug was about 1500 Omega /plug at the contact size of phi 0.30 mum.