Thermal Stability and Electrical Properties of SrBi2Ta2-xNbxO9/IrOx Capacitors with Pt Top Electrode

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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-Å-thick IrOx film after electrode annealing at temperatures above 700°C. The evaporation was caused by the reduction of IrOx to metallic iridium. However, SBTN/IrOx stack remained stable even after annealing up to 800°C. Ferroelectric crystallization annealing during the integration was performed at 650°C 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 $\mu$C/cm2 at the $2.4\,\mu\text{m}\times 3.7\,\mu\text{m}\times 256\,\text{ea}$ array capacitor after metallization and the leakage current density was about $4\times 10^{-7}$ A/cm2. The contact resistance of the SBTN/IrOx/Ir/TiN/plug was about 1500 $\Omega$/plug at the contact size of $\phi$ 0.30 $\mu$m.
2001-09-15