Enhanced Dielectric Constant by Al Gradient Doping on Atomic-Layer-Deposited HfO₂-Based Metal–Insulator–Metal Capacitor

As industries increasingly demand larger data capacities and faster processing, enhancing the capacitance of metal–insulator–metal (MIM) capacitors becomes crucial. This study investigates the effect of aluminum (Al) gradient doping on the dielectric constant of HfO₂-based MIM capacitors. Compared with conventional uniform doping, gradient doping more effectively accelerates the transition of HfO₂ to its high-k tetragonal phase, leading to higher capacitance. The study also explores factors such as the annealing temperature and atomic layer deposition conditions to optimize the high-k performance. Capacitors were fabricated and tested with gradient and uniform doping under 400°C, 500°C, and 600°C annealing conditions. Gradient doping significantly reduces the leakage current by an order of magnitude. The uniformly doped capacitors exhibit a dielectric constant of ∼44.7 and an equivalent oxide thickness (EOT) of 0.96 nm, whereas those with gradient doping achieve a dielectric constant of ∼60.7, which is the highest k-value of HfO₂ reported to date, and an EOT of 0.71 nm, representing a 35.8% improvement in dielectric constant and a 0.25 nm reduction in EOT. These findings highlight the potential of gradient doping to enhance MIM capacitor performance for high-capacitance applications.