Solution-Processable LaZrO_x/SiO₂ Gate Dielectric at Low Temperature of 180 °C for High-Performance Metal Oxide Field-Effect Transistors

Abstract

Although solution-processable high-k inorganic dielectrics have been implemented as a gate insulator for high-performance, low-cost transition metal oxide field-effect transistors (FETs), the high-temperature annealing (>300 °C) required to achieve acceptable insulating properties still limits the facile realization of flexible electronics. This study reports that the addition of a 2-dimetylamino-1-propanol (DMAPO) catalyst to a perhydropolysilazane (PHPS) solution enables a significant reduction of the curing temperature for the resulting SiO2 dielectrics to as low as 180 °C. The hydrolysis and condensation of the as-spun PHPS film under humidity conditions were enhanced greatly by the presence of DMAPO, even at extremely low curing temperatures, which allowed a smooth surface (roughness of 0.31 nm) and acceptable leakage characteristics (1.8 × 10(-6) A/cm(2) at an electric field of 1MV/cm) of the resulting SiO2 dielectric films. Although the resulting indium zinc oxide (IZO) FETs exhibited an apparent high mobility of 261.6 cm(2)/(V s), they suffered from a low on/off current (ION/OFF) ratio and large hysteresis due to the hygroscopic property of silazane-derived SiO2 film. The ION/OFF value and hysteresis instability of IZO FETs was improved by capping the high-k LaZrOx dielectric on a solution-processed SiO2 film via sol-gel processing at a low temperature of 180 °C while maintaining a high mobility of 24.8 cm(2)/(V s). This superior performance of the IZO FETs with a spin-coated LaZrOx/SiO2 bilayer gate insulator can be attributed to the efficient intercalation of the 5s orbital of In(3+) ion in the IZO channel, the good interface matching of IZO/LaZrOx and the carrier blocking ability of PHPS-derived SiO2 dielectric film. Therefore, the solution-processable LaZrOx/SiO2 stack can be a promising candidate as a gate dielectric for low-temperature, high-performance, and low-cost flexible metal oxide FETs.

Solution Processed Metal Oxide High‐κ Dielectrics for Emerging Transistors and Circuits

“…Several promising strategies have been proposed to address these issues, and achieve multicomponent and multilayered dielectrics, incorporating high κ and large E g into the same gate dielectric ( Table 4 ). Kats et al proposed a novel sodium beta‐alumina (SBA) film .…”

Identification of dipole disorder in low temperature solution processed oxides: its utility and suppression for transparent high performance solution-processed hybrid electronics

“…18–22 More recently, a few groups have reported solution processed dielectric layers formed at low process temperature (<300 °C); often these studies report unexpectedly high charge carrier mobilities, significant hysteresis in the device characteristics and rarely an attempt is made to characterize device stability. 23,24 Hence, there is an urgent need to understand these unexpected characteristics, instability and the device physics to enable full realization of all solution, low-temperature processed oxide TFTs.…”

Structural Study of Silica Coating Thin Layers Prepared from Perhydropolysilazane: Substrate Dependence and Water Penetration Structure

“…Nevertheless, further research on the nano-structure and detailed synthesis mechanisms for the preparation of SiO2 layers is important for the development of silicon-based coating materials. A variety of techniques, such as Fourier-transform infrared spectroscopy (FT-IR) [8,11], X-ray photoelectron spectroscopy (XPS) [8,11], and neutron reflectivity (NR) [5], have been used to study the structure of PHPS-derived silica (PDS) thin layers. Since the thickness, density, and roughness of the thin layer samples can be determined by NR techniques [12,13], here we use NR techniques to elucidate the nano-structure of PDS thin layers.…”