SrTiO 3 and (Ba,Sr)TiO 3 Films Epitaxially Grown on SrRuO 3 Using Atomic Layer Deposition.

High dielectric constant ( k ) materials have been investigated to improve the performance of dynamic random access memory (DRAM) capacitors. However, the conventional binary oxides have reached their fundamental limit of k < 100. In this study, we investigated alternative ternary oxides, SrTiO 3 (STO) and (Ba,Sr)TiO 3 (BSTO), which were epitaxially grown on SrRuO 3 (SRO) using atomic layer deposition (ALD). The structural compatibility between SRO and STO enables the in situ crystallization of STO during ALD at a low temperature of 300 °C. Consequently, STO on SRO exhibited no film deformation, a common issue during high temperature postdeposition annealing, and maintained superior crystallinity at a thin thickness down to 50 Å. Furthermore, the dielectric constant of STO can be adjusted by modulating its tunable ferroelectric and dielectric properties through Ba doping. BSTO, with a high dielectric constant ( k max :527) achieved at a Ba doping concentration of approximately 50%, displayed a low leakage current density (3.9 × 10 -8 A cm -2 @ 1 V) and demonstrated excellent reliability of 10 12 cycles in the metal-insulator-metal capacitors. This study proposes a promising alternative to satisfy the extreme EOT required for next-generation DRAM capacitors.