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.