Zirconium-Aluminum-Oxide Dielectric Layer with High Dielectric and Relatively Low Leakage Prepared by Spin-Coating and the Application in Thin-Film Transistor

Abstract

In this paper, zirconium-aluminum-oxide (ZAO) dielectric layers were prepared by a solution method with intent to combine the high dielectric constant with a low leakage current density. As a result, dielectric layers with improved electrical properties as expected can be obtained by spin-coating the mixed precursor. The chemical and physical properties of the films were measured by thermogravimetric differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and a UV spectrometer. It is observed that the oxygen defects and the hydroxide in the films are reduced with the addition of high-bond-energy zirconia, while the films can remain large optical bond gaps thanks to the presence of alumina. The metal-insulator-metal (MIM) devices were fabricated, and it was seen that with a molar ratio of Zr:Al = 3:1 and an annealing temperature of 500 • C, the dielectric layer afforded the highest dielectric constant of 21.1, as well as a relatively low leakage current of 2.5 × 10 −6 A/cm 2 @ 1 MV/cm. Furthermore, the indium-gallium-zinc oxide thin-film transistors (IGZO-TFTs) with an optimal ZAO dielectric layer were prepared by the solution method and a mobility of 14.89 cm 2 /Vs, and a threshold voltage swing of 0.11 V/dec and a 6.1 × 10 6 on/off ratio were achieved at an annealing temperature of 500 • C.

Application of Amorphous Zirconium-Yttrium-Aluminum-Magnesium-Oxide Thin Film with a High Relative Dielectric Constant Prepared by Spin-Coating

“…This implies that it is more likely to obtain thin films with a higher relative dielectric constant under 400 °C. Similar results can be found in the study of Liang et al [ 24 ]. We speculated that the content of bound oxygen dropped as the temperature climbed, which is easier for solvent to decompose, but the oxygen defects increased as well after 400 °C.…”

“…The oxides applied to the insulating layer have been a single-metal or binary-metal system so far, for example, AlO x [ 19 , 20 ], HfO x [ 21 ], YO x [ 9 , 22 ], AlZrO x [ 23 , 24 ], YAlO x [ 25 ], LaZrO x [ 26 ], ZnMgO x [ 27 ], etc. However, most of them can only make one breakthrough in the band gap, leakage current or permittivity.…”

Research Progress of High Dielectric Constant Zirconia-Based Materials for Gate Dielectric Application

“…Incorporation of Al 2 O 3 into ZrO 2 gate dielectrics combines the advantages of constituent dielectrics and markedly increases the crystallization temperature [54], which produce devices with improved performance and stability compared to the pure ZrO 2 film. In addition, the doping of small-size Al atoms into ZrO 2 that have greater densification can reduce the oxygen vacancy and smooth the gate dielectric interface [55,56]. Thereby, reducing the interface defects and gate leakage current as well as weakening the carrier mobility reduction effect caused by surface roughness scattering.…”

Spray‐Pyrolyzed High‐k Zirconium‐Aluminum‐Oxide Dielectric for High Performance Metal‐Oxide Thin‐Film Transistors for Low Power Displays

“…Among these materials, a combination of high‐k (≈22) ZrO 2 and wide band gap (≈8.8 eV) aluminum oxide (Al 2 O 3 ), [ 2,5a ] zirconium‐aluminum‐oxide (ZAO) by solution process is a promising candidate to replace the vacuum‐processed SiO 2 GI due to its excellent properties in comparison with other ternary dielectrics. [ 17,18,25 ] Note that the very high crystallization temperature (>800 °C) of Al 2 O 3 provides a thermodynamically stable ZAO GI until 600 °C, which leads to an amorphous film. [ 17,26 ] In general, amorphous dielectric films are more favorable owing to the smoother surface, lower leakage current, and higher breakdown electric field compared to crystalline counterparts.…”

“…[ 17 ] Employing the same deposition technique, Jo et al reported ZAO GI for amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) TFTs, showing a saturation mobility (μ SAT ) of 7.71 cm 2 V −1 s −1 , threshold voltage ( V TH ) of 1.30 V, subthreshold swing (SS) of 153 mV dec −1 , and I ON / I OFF ratio of 2.42 × 10 9 . [ 18 ] Later, Liang et al investigated spin‐coated ZAO GI for a‐IGZO TFTs, exhibiting the μ SAT of 14.89 cm 2 V −1 s −1 , SS of 110 mV dec −1 , and I ON / I OFF ratio of 6.1 × 10 6 , but with high turn voltage ( V ON ) close to 4 V. [ 25 ] Based on these studies, we choose 1 : 1 composition ratio of Zr and Al for the ZAO precursor solution.…”