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In recent years, lanthanum‐doped hafnium–zirconium dioxide (La‐HZO) has garnered attention as a material for application in ferroelectric devices; moreover, atomic layer deposition has been applied to prepare La‐HZO films with metal–ferroelectric–metal structures. This article describes the fabrication of ferroelectric La‐HZO thin films on Pt/Ti/SiO2/Si substrates via a solution process. The dependence of the electrical properties on the La concentration of La‐HZO films annealed at 800 °C in vacuum is also discussed. The film with a La concentration of 8 at% exhibits the highest remanent polarization, whereas undoped HZO exhibits paraelectric behavior. Additionally, the leakage current of La‐HZO specimens tends to be significantly lower than that of undoped HZO. Furthermore, a higher annealing temperature corresponds to better ferroelectric properties and a lower leakage current. The characterization of fabricated ferroelectric gate thin‐film transistors (FGTs) with an 8 at% La‐HZO gate insulator and indium‐tin‐oxide channel is shown to confirm typical n‐channel transistor operation, i.e., a counterclockwise hysteresis loop in the transfer curve; this is attributable to the ferroelectric nature of the La‐HZO gate insulator. The results demonstrate that the proposed FGT design offers a low subthreshold voltage swing, high on/off drain current ratio of 106, large on‐current, and large memory window. [ABSTRACT FROM AUTHOR]

N-channel planar [Al.sub.2][O.sub.3]/Si[O.sub.2]/SiC MOSFETs are fabricated and the effect of a Si[O.sub.2] layer inserted between [Al.sub.2][O.sub.3] and SiC is examined. The results have shown that the interface property of the ultrathin Si[O.sub.2]/SiC structure is very good, but the interface property has degraded when the Si[O.sub.2] thickness is larger than 2 nm due to interfacial layer formation.

We propose a three-terminal variable-area capacitor integrated with a ferroelectric-gate field-effect transistor (FeFET) and a paraelectric thin-film capacitor. Owing to the large charge controllability and nonvolatile memory function of the ferroelectric Hf0.86Ce0.14O2 (14% Ce-HfO2) gate insulator, the variable-area capacitors exhibited high capacitance tuning ratios of up to 184 with steep modulation to gate voltage swing (440 mV/decade), a capacitance-switching speed of less than 10 ms, and capacitance-memory-retention characteristics of up to 105 s. An FeFET with an indium tin oxide (ITO) channel and a ferroelectric 14% Ce-HfO2 gate insulator was fabricated as a switching FET via chemical solution deposition, followed by stacking a sputtered Al2O3 film as a variable capacitor. The fabricated FeFETs exhibited a high on-current of ∼0.15 A/mm, a large on/off current ratio of 107, a field-effect mobility of 15.6 cm2/V s, and a memory window of ∼5 V. The high on-current, i.e., low on-resistance (84 Ω), and the large on/off current ratio allow the ITO channel to act as a wiring that connects and disconnects two capacitors with different electrode areas; therefore, the proposed variable capacitor can achieve wide and steep modulation by ferroelectric gating. This study provides prospects for the future integration of passive and active components for advanced high-efficiency and miniaturized electronics such as power devices and communication equipment. [ABSTRACT FROM AUTHOR]

We report the improvement of ferroelectric (FE) amorphous InGaZnO4(a-IGZO) thin film transistors (TFT) by Ar/O2 plasma treatment and subsequent thermal annealing. The a-IGZO (In2O3:Ga2O3:ZnO = 1:1:1) and HZO (Hf:Zr = 1:1) layers were deposited by DC sputtering and spray coating, respectively. The Ar/O2 plasma exposure for 10s and thermal annealing at 300°C for 15 min on the a-IGZO/HfZrO(HZO) improves the field effect mobility from 18.6 to 20.0 cm2V−1S−1, subthreshold swing from 345 to 125 mV/decade, memory window from 0.45 V to 1.0 V, and polarization from $7 ~\mu \text{C}$ /cm2 to $9 ~\mu \text{C}$ /cm2. The improvement is mainly due to the reduction of oxygen vacancies at the a-IGZO/HZO interface by Ar/O2 plasma exposure and subsequent annealing. [ABSTRACT FROM AUTHOR]

The fabrication of a pulse frequency modulation type ferroelectric neuron circuit comprising metal-ferroelectric-semiconductor field effect transistor, is described.

The impact of reduced pressure annealing on ferroelectric properties in hafnium-zirconium oxide (HZO) films deposited by sputtering has been investigated. It is demonstrated that the HZO films annealed at 600 °C at less than 100 Pa show excellent ferroelectric properties, whereas the HZO films annealed at more than 1000 Pa show degraded electrical properties. This is presumably due to the introduction of oxygen vacancies, which stabilize the ferroelectric orthorhombic phase. Thermal stability can be also improved for the HZO films annealed at reduced pressures. In addition, ferroelectric gate transistor operation is demonstrated using an HZO gate insulator annealed at 100 Pa with the indium-tin-oxide channel. [ABSTRACT FROM AUTHOR]

There is increasing interest in a ferroelectric transistor, mainly using vacuum processed hafnium oxide based materials. We report in this paper a solution processed ZnO thin-film transistor (TFT) with improved ferroelectric performance in Hf0.5Zr0.5O2 (HZO) using a triple layer of ZrOx/HZO/AlOx by spray pyrolysis. The performance enhancement is due to the difference in thermal expansion coefficient between the bottom/top dielectric and HZO layers. Grazing incident x-ray diffraction, current–voltage, capacitance–voltage, polarization–voltage, and anticlockwise hysteresis in transfer curve confirm the excellent ferroelectricity of the triple layer. A memory window as large as ∼3 V, the maximum on/off ratio of 3.5 × 109, the field-effect mobility of 125 cm2/V s, and the subthreshold slope of 0.18 V/decade were obtained from the ZnO TFT with the ZrOx/HZO/AlOx gate insulator, demonstrating the high performance ferroelectric ZnO TFT. This result can open opportunities for ferroelectric oxide TFT for large area electronics on glass, including display. [ABSTRACT FROM AUTHOR]

Ferroelectric gate transistor (FGT) with yttrium doped hafnium-zirconium dioxide (Y-HZO) gate insulator and oxide channel with various thicknesses of In2O3 and ITO were fabricated by chemical solution deposition. First, ferroelectric properties of Y-HZO in the metal-ferroelectric-semiconductor structure with 5–22 nm thick In2O3 and 6–24 nm thick ITO, have been confirmed by polarization–voltage and capacitance–voltage (C–V) characteristics. The C–V curves showed clear butterfly loops showing the depletion of In2O3 and ITO layer. Secondly, the device performance of FGTs has been evaluated with various thicknesses of In2O3 and ITO channel layer. The fabricated FGTs exhibited typical n-channel transistor operation with a counterclockwise hysteresis loop due to the ferroelectric nature of the Y-HZO-gate insulator. It was found that FGT shows a low subthreshold voltage swing, high on/off drain current ratio of 106, large on current, and memory window. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ultraviolet-ozone (UV/O3) treatment was adopted to the fabrication of solution-processed amorphous In-Ga-Zn-O thin-film transistors (TFTs), with metal composition of In:Ga:Zn = 1:1:1 represented by InGaZnO4. By applying UV/O3 treatment In-Ga-Zn-O gel films, their condensation was notably enhanced through decomposition of organic- and hydrogen-based elements, which drastically improved the quality of the amorphous InGaZnO4 films. As a result, high TFT performance, with values of on/off ratio, 108; subthreshold swing, 150 mV/decade; threshold voltage, 9.2 V; and field-effect mobility, 5.1 cm2 V-1 s-1, was achieved. [ABSTRACT FROM AUTHOR]