High‐performance In–Zn–O thin‐film transistors with a soluble processed ZrO₂ gate insulator

Abstract

Recently, amorphous metal-oxide thin-film transistors (TFTs) have attracted considerable interest as attractive backplane electronics for active matrix organic lightemitting diodes (AMOLEDs) and transparent displays because they offer high mobility, low-temperature processability and good transparency to visible light [1,2]. In particular, low power consumption is one of the key issues for the mobile applications, such as smart phones and tablet personal computers, due to the limited capacity of the rechargeable lithium-ion battery used as power source [3]. The use of a high-k dielectric film as a gate insulator is an effective approach for enhancing the capacitive coupling and reducing the power consumption. Many studies have examined the adoption of high-k dielectric materials, such as HfO 2 [4], TiO 2 [5], AlTiO [6], Ta 2 O 5 [7,8], HfLaO [9] and ZrO 2 [10] in the transition-metal-oxide TFTs. These have generally been fabricated by vacuum deposition methods, such as pulsed laser deposition (PLD) [4], atomic layer deposition (ALD) [5,6], evaporation [7-9] and sputtering [8,10], which require expensive vacuum equipment. In contrast, solution-based deposition techniques, such as spin coating would offer a range of merits, such as simplicity, low cost and high throughput. In this regard, very re-cently there have been many reports on the soluble processed high-k gate dielectrics such as ZrO 2 [11][12][13], Y 2 O 3 [14,15] and HfO 2 [16] for metal-oxide TFTs. Among these high-k dielectrics, the ZrO 2 material is promising due to its high relative permittivity, wide bandgap (5-8 eV) and good thermal stability [17]. Lee et al. reported the highmobility (27.3 cm 2 /V s) ZTO TFTs with soluble processed ZrO 2 gate insulator at an annealing temperature of 500 °C [13]. However, the annealing-temperature-dependent structural property and the resulting electrical performance was not examined in detail. In this Letter, we investigated the effect of annealing temperature on the soluble processed ZrO 2 gated indium zinc oxide (IZO) TFTs. It was found that the low-voltage, high-mobility IZO TFTs with soluble processed ZrO 2 gate insulator can be fabricated at an annealing temperature of 400 °C.A heavily doped p-type silicon (p ++ Si) wafer was used as the bottom gate electrode. A precursor solution for the ZrO 2 film was synthesized using a sol-gel process with ZrCl 4 , HNO 3 and H 2 O dissolved in ethanol. The concentration of the metal precursor was 0.5 M and the ratio of ZrCl 4 :HNO 3 :H 2 O was 1:10 :10. The solution was spincoated on a bare Si substrate for 30 s at 5000 rpm. The re-Spin-coated zirconium oxide films were used as a gate dielectric for low-voltage, high performance indium zinc oxide (IZO) thin-film transistors (TFTs). The ZrO 2 films annealed at 400 °C showed a low gate leakage current density of 2 × 10 -8 A/cm 2 at an electric field of 2 MV/cm. This was attributed to the low impurity content and high crystalline quality. Therefore, the IZO TFTs with a soluble ZrO 2 gate insula-tor exhibited a high field ef...

Properties-Adjustable Alumina-Zirconia Nanolaminate Dielectric Fabricated by Spin-Coating

“…However, the application of solution-process to fabricate nanolaminates were rarely reported, especially for spin-coating. Spin-coating has attracted more and more attention for low cost, simplicity, and high throughput [8]. Metal oxide dielectrics, such as Al 2 O 3 , HfO 2 , and ZrO 2 can be obtained easily by spin-coating [9,10,11].…”

A Simple Method for High-Performance, Solution-Processed, Amorphous ZrO2 Gate Insulator TFT with a High Concentration Precursor

“…In Figure 2 c–e, we fitted the oxygen 1s peak to a superposition of two peak components. The peaks centered at 530.0 ± 0.2 eV and 531.5 ± 0.2 can be assigned to the metal-oxygen-metal M-O-M species and M-OH species [ 8 , 16 ] in both films annealed at 300 °C, 400 °C, and 500 °C, respectively. The M-O-M species (530.0 ± 0.2 eV) is related to O 2− ions combined with the Zr 4+ ion, while the M-OH species (531.5 ± 0.2 eV) is attributed to oxygen defects in the film and the presence of loosely bonded oxygen molecules such as adsorbed O 2 and H 2 O.…”

“…Several methods [ 7 , 8 , 9 , 10 ] towards reducing the leakage current are mentioned in the previous study including doping, applying the modified layer, and increasing the annealing temperature. Most of them are related to a complicated operation in regulation of the precursor and interface engineering.…”

Effects of boron incorporation on the structural, optical and electrical properties of sol–gel-derived ZrO2 gate dielectrics

“…In addition, fabricating high-k metal oxide films using solution processing requires a high annealing temperature of above 450 C because of the high pyrolysis and dehydroxylation temperature of typical precursors [16]. High annealing temperature is effective in removing the impurities and oxygen vacancies from metal oxide films leading to acceptable leakage and capacitance characteristics [17]. Unfortunately, high annealing temperature is also one of the main bottlenecks of flexible electronics on plastic substrates.…”