HZO ( $>$ 10 Nm) Films for Achieving High-TEXPRESERVE1 Near Morphotropic Phase Boundary at Low-Temperature Furnace Annealing Process

Recently, hafnium zirconium oxide (Hf $_{\textit{x}}$ Zr $_{{\text{1}}-{\textit{x}}}$ O $_{{\text{2}}}$ , HZO) films gained considerable attention in sensors, displays, and memory devices. However, one of the main drawbacks of HZO material is that as the film thickness increases, the dielectric constant ( $\kappa \text{)}$ can deteriorate. To address this issue, we investigated a study on the enhancement of dielectric constant for HZO films ( $>$ 10 nm) at a low thermal budget. We experimentally demonstrated the existence of a morphotropic phase boundary (MPB) in the HZO films by employing postmetallization annealing (PMA) process at 350 $^{\circ}$ C. A high dielectric constant was achieved by optimizing process parameters, such as HZO compositions (1:1, 1:3, and 1:5), HZO film thicknesses (15, 30, and 45 nm), and different annealing conditions (PMA 350 $^{\circ}$ C and PDA 350 $^{\circ}$ C). The maximum dielectric constant of TiN electrodes was found to be around 38 near MPB for the 15-nm-thick HZO (1:5) films due to the formation of a high tetragonal phase (t-phase) in Zr-rich films. As the film thickness increases, the dielectric constant also decreases. On the other hand, the PDA devices exhibit exclusively ferroelectric behavior due to the higher orthorhombic phase (o-phase). Also, endurance measurements were performed on both PMA and PDA, revealing that these devices are endurable up to 10 $^{\text{10}}$ cycles. Furthermore, the dielectric constant was enhanced greatly to 43 at 15-nm-thick HZO and 39 at 30-nm-thick HZO by utilizing the Mo top electrode. This work provides a promising method for achieving a high dielectric constant in HZO films for smart electronic systems.