Effect of Content Ratio on Solution-Processed High-k Titanium-Aluminum Oxide Dielectric Films

Abstract

In this paper, a solution-processing method for fabrication of the titanium-aluminum oxide (TAO) was proposed. Variation of band gap, permittivity, and leakage current density and permittivity of TAO films with different Ti content were investigated. The permittivity and leakage current density of TAO films were proportion to the Ti content, while the bandgap did the reverse. A remarkable enhancement in permittivity (16.5) could be achieved at Ti:Al=0.4:0.6, meanwhile the leakage current density was ∼4 × 10 −7 A/cm 2 at 2 MV/cm.With the development of flat panel display (FPD), thin film transistors (TFTs) based on oxide semiconductors have received widespread attention. 1 Due to the increase of display resolution, large threshold and high operating voltages become a major limitation for mobile, battery-powered applications. The commonly used dielectrics such as SiO 2 and Si 3 N 4 usually result in high operation voltage because of the weak capacitive coupling between the gate electrode and active channel. Using a high-k dielectric is unarguably the most promising method since it can increase the capacitive couple because of its higher permittivity than SiO 2 (4). Besides, higher k dielectrics enable us to employ a thicker insulator but with the same capacitance as the requirement of SiO 2 , consequently, ensure the low leakage current. 2 There are already numerous candidates that could be employed as the gate dielectrics in TFTs, such as etc. Among the various high-k materials, Al 2 O 3 is well studied owing to its wide band gap (8.9 eV), low leakage current density, and good interface characteristics. However, the permittivity of 9 for Al 2 O 3 8 could be the fly in the ointment. TiO 2 is another well-known high-k material for the desirable permittivity of 155 9 with environment-friendly feature. Nevertheless, TiO 2 suffers from its high leakage current due to a narrow band gap (3.0-3.2 eV) and poor suppression of leakage. Auciello et al., and Shi et al. have reported the investigation of TiO 2 -Al 2 O 3 (TAO) dielectric films fabricated by sputtering and pulsed laser deposition, respectively. 10,11 However, many optical and electrical properties of TAO, such as bandgap, permittivity, leakage current density, still need to be studied. In this paper, solution-processing method is adopted to prepare the target films due to the component-controllability advantage. Variation of TAO band gap, permittivity, and leakage current density with different Ti content were investigated. ExperimentalThe 0.4M precursor solution of TAO is prepared by dissolving Aluminum (III)-s-butoxide Al(C 4 H 9 O) 3 , tetrabutyl titanate Ti(C 4 H 9 O) 4 in 2-methoxyethanol (2ME) in turn, then hydrochloric acid is added dropwise till the solution becomes clear, the whole process is accompanied by intense oscillation. The mole ratio of Ti and Al is varied from 2:8 to 8:2. All the chemical reagents were bought from Sinopharm Chemical Reagent Co., Ltd. After a 6 h stirring resulting in a transparent solution, the TAO solution was aged in a contro...

Dielectric ceramics/TiO2/single-crystalline silicon nanomembrane heterostructure for high performance flexible thin-film transistors on plastic substrates

“…Multilayer gate stacks with high-k and high band gap materials have been also investigated in recent years. [26][27][28][29][30][31][32][33][34] The fabricating methods mainly include ALD, 28,29 solution process 30,31 and sputtering. [32][33][34] However, these multilayer structures are still not suitable for exible TFTs.…”

“…For example, ALD deposited or solution-processed gates with processing temperature at least 300 C (such as TiO 2 30 and TiO 2 /Al 2 O 3 (ref. 31) by solution process) exceed the maximum process temperature that exible substrates can withstand. On the other hand, lowering the processing temperature or roomtemperature magnetron sputtering will signicantly degrade the electrical properties of these dielectrics, such as high trap density, higher leakage current, higher subthreshold swing and thus poor subthreshold characteristics, etc.…”

Synthesis and characterization of mist chemical vapor deposited aluminum titanium oxide films

“…28,29) Because these models indicate that refractive index linearly depends on the film density. Pu et al 34) and Peng et al 35) obtained the direct optical bandgap of spin coated-Al 1-x Ti x O y films from transmittance spectra with simple Tauc plots. 36) We also determined the direct optical bandgap of mist-Al 1-x Ti x O y films for x = 0.19-0.72 with nominal thickness of 1 μm on sapphire substrate using ultraviolet/visible spectrophotometer equipment (Shimadzu UV-3600) with wavelength ranges from 185 to 2500 nm.…”

Improvement of self-heating effect in Ge vertically stacked GAA nanowire pMOSFET by utilizing Al2O3 for high-performance logic device and electrical/thermal co-design

“…In addition, it would be much better if a fabrication technology will be further developed and be capable of making an interfacial SiO 2 layer as thin as possible with good film quality. The fabrication method for making Al 2 O 3 with high permittivity 44,45) and making a good thin SiO 2 interfacial layer 46,47) have been broadly researched in many previous studies. Therefore, researchers who are reading this paper are recommended to look for these relevant previous researches and fabricate it based on their knowledge if possible.…”

“…For example, the quality of dielectric films (including the amount of fixed charge and carrier traps) may affect the electrical characteristics and reliability issue. As demonstrated in lots of previous research, [44][45][46][47] the quality of dielectric films depends heavily on the fabrication method. Therefore, we the authors would like to suggest future research to readers by fabricating our proposed device structure.…”