Impact of annealing environment on electrical properties of yttrium-doped hafnium zirconium dioxide thin films prepared by the solution process

Abstract

Ferroelectric yttrium-doped hafnium zirconium dioxide (Y-HZO) was fabricated on Pt/Ti/SiO2/Si substrate by the solution process under various annealing environments. A metal–ferroelectric–metal structure with Pt as the top electrode was fabricated and characterized. Samples annealed at 600–800 °C in a vacuum environment showed ferroelectricity, which was confirmed by the polarization–electric field and capacitance–voltage measurements. The ferroelectric properties were dramatically improved when samples were annealed in a vacuum at 800 °C due to the decrease in leakage current compared to the Y-HZO films annealed at 800 °C in oxygen and nitrogen.

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

“…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. 26) In addition, we have demonstrated FGT using CSD ITO or CSD In 2 O 3 as a channel and CSD Y-HZO as a ferroelectric gate insulator. 27) In this work, a comparative study on stability of ferroelectricity of the sputtered HZO and vacuum annealed CSD Y-HZO films in metal-ferroelectric-semiconductor (MFS) structure has been performed.…”

“…Ferroelectric nature was observed with clear hysteresis and switching response for both sputtered HZO and CSD Y-HZO films, which is consistent with our previous report. [24][25][26][27][28] It is worth noting that the sputtered HZO film has superior ferroelectricity at the beginning before the re-annealing treatment. The switching current peak is more pronounced for the sputtered HZO thin film and P-E loop of CSD Y-HZO film may have some parasitic effects, although the P r value of the CSD Y-HZO looks similar to that of the sputtered film.…”

“…It was found from secondary ion mass spectrometry that the residual carbon content of CSD Y-HZO films were as large as 5%. 25,26) Such a large amount of carbon content could help prevent the formation of low symmetry phase or m-phase. 32) Takahashi et al reported in SSDM 2020, enhancement of polarization by controlling incorporation of carbon content in the HZO films.…”

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

“…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.…”

An Aqueous Route to Oxygen-Deficient Wake-Up-Free La-Doped HfO2 Ferroelectrics for Negative Capacitance Field Effect Transistors

“…The emergence of an o-phase is attributed to the formation of sub 10 nm grains owing to its lower volume compared to the m-phase. − Numerous attempts were reported to crystallize doped-HfO 2 with a nanostructured morphology, especially in the case of films from atomic layer deposition (ALD) and chemical solution deposition (CSD). − The former is known to deposit robust monolayers, and the latter is mainly employed to grow thicker films. − In both cases, a prominent mechanism of inhibiting the grain growth, i.e., kinetic stabilization of the o-phase, is used . The retained carbonaceous impurities arising from the incomplete oxidation of the precursor serve as a growth inhibitor. , However, the presence of small grains, i.e., a large grain boundary area with carbon segregation, leads to high leakage currents and low electrical breakdown. , Despite being cost-effective and having a high yield, with greater processing controllability for a wide range of chemical compositions, CSD-processed films (with grain boundaries decorated by carbonaceous impurities) face challenges in commercialization because the resulting film is not suitable for industry-grade application.…”