Effect of Plasma Excitation Mode on Rutile TiO₂ MIM Capacitors Grown on RuO₂ Seed Electrodes

Maintaining low leakage current with high capacitance density in metal-insulator-metal (MIM) capacitors is essential for next-generation dynamic random-access memory (DRAM) scaling. Rutile TiO₂ is a promising high-k dielectric; however, its narrow bandgap causes high leakage, while defect-free stabilization in ultrathin films remains challenging. RuO₂/TiO₂/Ru MIM capacitors were fabricated using a reactive direct current (DC)-sputtered RuO₂ bottom electrode, followed by TiO₂ growth by direct plasma atomic layer deposition (DP-ALD) or remote plasma atomic layer deposition (RP-ALD) and rapid thermal annealing in O₂ to reduce defects. Rutile TiO₂ was deposited directly on highly crystalline RuO₂ under both plasma modes, suggesting that RuO₂ crystallinity governs TiO₂ phase evolution. The RP-ALD film replicated the RuO₂ grain morphology, yielding higher roughness than that of the DP-ALD film. Moreover, the RP-ALD film exhibited lower oxygen-vacancy density and improved stoichiometric stability. The RP-ALD-fabricated capacitors exhibited a higher dielectric constant and lower leakage current density at 0.8 V than the DP-ALD-fabricated capacitors (~100 and ~1.76 × 10^-6 A/cm² vs. ~97 and ~1.41 × 10^-4 A/cm², respectively). Ion bombardment during DP-ALD likely promoted oxygen-vacancy-related defect formation, whereas RP-ALD mitigated such damage, improving leakage characteristics. This work highlights the potential of RP-ALD-based RuO₂/TiO₂/Ru MIM capacitors for next-generation DRAM.