A Solution-Processed La-Zr-O Dielectric at a Low Temperature for High-Performance In-Ga-O Transistors: Engineering a Precursor Solution

Abstract

For portable and low-power flexible devices, metal-oxide (M − O) materials offer high performance, superior stability, and a low-cost printing process that permits facile mass production. However, realization of printed flexible electronics using inorganic M − O materials has proven challenging because of obstacles associated with producing high-quality and dense dielectric films through a solution process at low temperatures. In this study, the effect of the solution stirring temperature and H2O2 loading on the structural and electrical properties of lanthanum zirconium oxide (LZO) dielectric films was investigated in detail. The surface roughness, mass density, and purity of H2O2–assisted LZO improved with increasing stirring temperature, resulting in a low leakage current of 4 × 10−8 A/cm2 at 2 MV/cm, a high-breakdown electric field of ~5.8 MV/cm, and relatively high permittivity (>12) at a low photochemical activation temperature of 180 °C for optimized LZO dielectric films. This can be attributed to the synergetic interaction of oxygen radicals introduced by H2O2 oxidants during deep ultraviolet photochemical annealing, causing hydrolysis of metal precursors, removal of organic residue, and formation of an M − O lattice. The fabricated indium gallium oxide thin-film transistor on a polyimide substrate at a maximum processing temperature of 180 °C exhibited a high mobility of 14.5 cm2/Vs, a high ION/OFF ratio of 107, negligible hysteresis, and a small driving voltage range (−2 to 2 V).