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

Abstract

Stability of ferroelectricity in hafnium–zirconium oxide (HZO) films deposited by sputtering and chemical solution deposition (CSD) has been investigated. After confirming the ferroelectricity of both sputtered HZO and CSD yttrium-doped HZO (Y-HZO) films, indium-tin-oxide (ITO) was deposited by sputtering on sputtered HZO or CSD Y-HZO layer to fabricate metal-ferroelectric-semiconductor (MFS) structure. It was found that the sputtered HZO films in the MFS structure became paraelectric after re-annealing in N2 which was confirmed by both X-ray diffraction pattern and electrical measurements. On the other hand, the CSD Y-HZO films showed ferroelectric nature even after re-annealing with a negligible monoclinic phase.

Enhancement of ferroelectricity in sputtered HZO thin films by catalytically generated atomic hydrogen treatment

“…When the sputtered HZO film was crystallized in N 2 , it usually has both o/c/t and monoclinic (m) phases. 23) On the other hand, Fig. 3(b) shows the m-phase peak around 28.5°is negligible for the HZO film with Cat-H treatment, which was crystallized in N 2 and air.…”

“…The remanent polarization is as large as 20 μC cm −2 for the HZO film without the Cat-H treatment, whereas the 30 min Cat-H treated HZO film shows higher remanent polarization of 24 μC cm −2 . Since the stability of the ferroelectric o-phase is a concern in the sputtered HZO films especially for device applications, 23) next we examined the stability of reduced pressure annealed HZO films with and without the Cat-H treatment. The samples were re-annealed at 400 °C for 15 min in N 2 with Pt electrodes.…”

“…However, we reported that the sputtered HZO film became paraelectric after 400 °C, 15 min of re-annealing in N 2 ambient, even though good ferroelectric properties were initially observed. 22,23) This is in contrast to the films prepared by chemical solution deposition (CSD), which has robust ferroelectricity after the reannealing process and even after the oxide channel layer formation at 600 °C. 24,25) One of the reasons for the discrepancy is that the CSD Y-HZO has more oxygen vacancies than the sputtered HZO.…”

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

“…This is in contrast to previously reported results for an MFS structure with a sputtered ferroelectric HZO, which revealed that the ferroelectric properties were easily degraded by an additional O 2 annealing process. [ 23 ]…”

“…We applied the film to fabricate Pt/La-HZO/ITO/Pt metal-ferroelectric-semiconductor (MFS) structures to evaluate the stability of the o-phase because we found that the 8 at% La-HZO films annealed at 800 °C possessed good ferroelectric properties for the MFM structure. [23,24] We deposited a thin ITO layer by performing CSD on the La-HZO layer; it was crystallized at 800 °C. The CSD ITO channel layer was annealed at 600 °C in a N 2 or O 2 atmosphere.…”