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New, stable aqueous solutions have been developed for the deposition of high-quality HfO2 thin films. The low ionic strength of the solution relative to a stoichiometric salt provides the means to directly spin coat a film without organic additives. Peroxide mediates particle interaction in the solution, while enabling relatively low-energy pathways for condensation of the precursor species to a film. Film structure, chemistry, and density are investigated by X-ray diffraction, FT-IR, electron-probe microanalysis, SEM, and X-ray reflectivity. Results from these measurements collectively reveal that smooth and dense HfO2 films are readily produced from the precursors with annealing at moderate temperatures. Optical properties of the films are studied by spectroscopic ellipsometry and transmission/reflection measurements. The observed refractive indices (1.89−1.93) are comparable to those achieved via vapor deposition techniques. Dielectric properties are evaluated through integration of the films into capacitors and thin film transistors. Performance as capacitor dielectrics is characterized by leakage current densities <10 nA/cm2 (at 1 MV/cm) and breakdown fields up to 5.5 MV/cm. As gate dielectrics in thin film transistors with amorphous indium gallium zinc oxide channels, the films exhibit small gate leakage, enabling transistor performance with incremental mobilities near 13 cm2/V·s.

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An indium–gallium–zinc oxide or a zinc–tin oxide thin‐film transistor (TFT) fabricated when the relative humidity in the laboratory is less than 50% is found to exhibit good electrical performance, with an abrupt, distortion‐free transfer curve and a turn‐on voltage close to 0 V. In contrast, when such an amorphous oxide semiconductor (AOS) TFT is fabricated at a relative humidity greater than 50%, its “as‐fabricated” electrical performance is very poor, typically characterized by a large amount of hysteresis, a strongly negative turn‐on voltage, and a kink‐like distortion in the subthreshold region of its transfer curve. However, the electrical performance of such a poor‐quality TFT is observed to improve over time, if it is simply stored in the dark at room temperature without being subjected to electrical stress. This recovery usually requires weeks (months) for an unpassivated (passivated) AOS TFT. Recovery is tentatively ascribed to the gradual removal of moisture from the AOS TFT channel layer.

Low-Energy Path to Dense HfO 2 Thin Films with Aqueous Precursor.-High-quality, smooth and dense HfO2 thin films are deposited by spin coating using an aqueous H2O2/HNO3 solution of the precipitate obtained from an aq. pH 8.5 solution of HfOCl2 and NH3 as a precursor. The films are characterized by XRD, FTIR, SEM, and X-ray reflectivity. Dielectric properties are evaluated through integration of the films into capacitors and thin film transistors. The performance as capacitor dielectrics is characterized by leakage current densities <10 nA/cm 2 (at 1 MV/cm) and breakdown fields up to 5.5 MV/cm. The optical and dielectric properties of the films substantively exceed those produced by any other solution technique and in most respects rival those produced via advanced vapor methods, enabling their use as a high-performance dielectric. -(JIANG, K.; ANDERSON, J. T.; HOSHINO, K.; LI, D.; WAGER, J. F.; KESZLER*, D. A.; Chem. Mater. 23 (2011) 4, 945-952, http://dx.doi.org/10.1021/cm102082j ; Dep. Chem., Oreg. State Univ., Corvallis, OR 97331, USA; Eng.) -W. Pewestorf 16-006

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The dielectric properties of ZrO 2-Al 2 O 3 nanolaminates, deposited via atomic layer deposition, and their impact on the performance and stability of indium gallium zinc oxide and zinc tin oxide amorphous oxide semiconductor thin-film transistors ͑TFTs͒ are investigated. It is found that nanolaminate dielectrics can combine the advantages of constituent dielectrics and produce TFTs with improved performance and stability compared to single layer gate dielectrics. It is also found that TFT performance and stability are influenced not only by the chemical composition of the gate dielectric/channel interface but also by the thickness and composition of the laminate layers in the dielectric near the interface.

Amorphous oxide semiconductor thin‐film transistors (TFTs) are moving towards commercialization for a variety of display applications. Invariably, display applications require a bottom‐gate TFT configuration in which passivation of the top channel layer surface is required. The objective of this work is to propose a conceptual model framework for assessing TFT passivation schemes, within the context of amorphous oxide semiconductor electronics. This model involves first estimating the energy of the charge neutrality levels (CNLs) for the channel and passivation layers. Then, an energy band diagram is drawn to establish the relative position of these CNLs prior to their establishment of intimate contact. A situation in which the passivation layer CNL is below that of the channel layer CNL is considered undesirable because interface state electronic transfer from the channel to the passivation layer leads to formation of an accumulation layer at this interface. Although the opposite case in which the passivation layer CNL is above that of the channel layer CNL is more desirable, the ideal situation would be when both CNLs align because no interface state electronic transfer would occur. This framework is then employed in a discussion of the passivation of indium gallium zinc oxide and zinc tin oxide bottom‐gate TFTs.