Electrical properties of yttrium-doped hafnium-zirconium dioxide thin films prepared by solution process for ferroelectric gate insulator TFT application

Abstract

Ferroelectric yttrium-doped hafnium-zirconium dioxide (Y-HZO) thin films were fabricated by solution process on Pt/Ti/SiO2/Si substrates. Both metal–ferroelectric–metal (MFM) structures with Pt top electrode and metal–ferroelectric–semiconductor (MFS) structures with indium tin oxide (ITO) top electrode were fabricated and characterized. Solution-derived Y-HZO films annealed at 600 °C–800 °C showed ferroelectric properties which were confirmed by polarization–voltage loops (P–V) and capacitance–voltage (C–V) curves. The ferroelectric properties of Y-HZO were superior to those of undoped HZO, Y-doped HfO2 and undoped HfO2 samples. C–V curves showed clear butterfly loops with depletion of top ITO layer in the case of MFS, while no depletion was observed in the case of MFM structures. Large memory window was obtained for MFS structures and ferroelectric properties were observed even after high temperature annealing process during the solution deposition of ITO electrodes. These results suggest that a solution processed Y-HZO is a promising candidate for ferroelectric gate thin film transistor.

Fabrication of Ferroelectric Gate Thin‐Film Transistors with a Lanthanum‐Doped HZO Gate Insulator and Indium‐Tin‐Oxide Channel via a Solution Process

“…These values suggest that the 8 at% La-HZO film crystallized at 800 °C had a lower leakage current density than the films crystallized at 600 and 700 °C; this is presumably attributable to the decrease in carbon with increasing annealing temperature, and the formation of more o-phases. [20] We observed a similar tendency for the CSD Y-HZO films. [20]…”

“…[ 19 ] Crystallization was performed by applying rapid thermal annealing at 600–800 °C for 3 min at a reduced pressure of 50 Pa; these settings were applied because the vacuum‐annealed films exhibited better ferroelectricity. [ 20 ] In this study, the maximum annealing temperature was 800 °C because the Ti layer in the Pt/Ti/SiO 2 /Si substrate was oxidized to TiO x at higher annealing temperatures and the Pt surface would become rough, consequently increasing the leakage current. The thickness of the La‐HZO film was 33 nm.…”

“…The remanent polarization results revealed a trend of increase with increasing annealing temperature; this is consistent with previous reports. [20,21] A 10 4 cycling regime was also applied to these specimens; the results are shown in Figure 3d-f for films with crystallization temperatures of 600, 700, and 800 °C, respectively. The P-E results show that the La-HZO films annealed at 600 °C did not significantly change after 10 4 cycles; conversely, the cycling resulted in significant improvement in the 700 and 800 °C specimens; particularly, they achieved a clearer hysteresis loop and sharper switching response.…”

Thermal stability of ferroelectricity in hafnium–zirconium dioxide films deposited by sputtering and chemical solution deposition for oxide-channel ferroelectric-gate transistor applications

“…Previously, we reported solution-processed yttrium doped HZO (Y-HZO) annealed in O 2 environment with solutionprocessed indium-tin-oxide (ITO) as a top electrode with a relatively high-temperature annealing process. 25) Even though oxygen annealed Y-HZO films show rounded P-V loops due to high leakage, but the clear butterfly curves were observed in capacitance-voltage (C-V ) curves. In addition, we reported ferroelectric polarization-electric field (P-E) loops and leakage current of Y-HZO films prepared by chemical solution deposition (CSD) can be drastically improved by vacuum annealing of Y-HZO films.…”

High-Endurance Ferroelectric (La, Y) and (La, Gd) Co-Doped Hafnium Zirconate Grown by Atomic Layer Deposition

“…Moreover, the beneficial effect of La doping on the endurance of polycrystalline HZO films may be accompanied by a degradation of the retention, reducing the performance of the device . Other dopants such as Y were also shown to induce ferroelectricity in HZO . However, according to a thorough ab initio study by Zhao et al of different group III dopants (which included La, Y, Al, and Gd), La remains the most favorable dopant in terms of stabilizing the ferroelectric phase in HZO.…”