Relatively thick Hafnia strategies to obtain high dielectric constant near MPB for display applications

Abstract

In recent years, thick films (> 30 nm) based hafnium zirconium oxide (HZO) devices gained considerable attention in sensors, displays, logic and memory devices. However, one of the main drawbacks of HZO material is that as the film thickness increases, dielectric constant (κ) can deteriorate. To address this issue, we investigated a study on the enhancement of dielectric constant for thick HZO films at low thermal budget process. In this work, we experimentally demonstrated the existence of a morphotropic phase boundary (MPB) in the relatively thick HZO films with Al2O3 insertion thin film by employing microwave annealing process at 350 °C. A high dielectric constant was achieved by optimizing processes parameters such as HZO compositions (1:1, 1:3, and 1:5), HZO film thicknesses (15, 30, and 45 nm), different annealing conditions (PMA 350 °C and PDA 350 °C), different electrode and annealing approaches (MWA and FA) near MPB. The optimized dielectric constant was found to be around 42 near MPB for the 30nm-thick HZO (1:5) films due to the formation of high tetragonal phase (t-phase) in Zr rich films. Further, GIXRD reveals the formation of higher tetragonal phase (t-phase) in the case of HZO (1:5) films under the PMA condition, resulting in an increased dielectric constant. On the other hand, Mo electrode has larger tensile stress than TiN, and different electrodes in HZO capacitors can prevent the etching issue in thin-film-transistor integration process. To better understand device reliability, endurance measurements were performed, revealing that devices with TiN electrode are endurable up to 109 cycles, while Mo can only endurance to 105 cycles. The present work provides a promising method for achieving a high dielectric constant in thick HZO films for sensors, display devices and smart electronic systems in the contemporary electronic industry.