Je So Yeon, Son Byeong-Geun, Kim Hyun-Gwan, Park Man-Young, Do Lee-Mi, Choi Rino, Jeong Jae Kyeong
Department of Materials Science and Engineering, Inha University , Incheon 402-751, Korea.
ACS Appl Mater Interfaces. 2014 Nov 12;6(21):18693-703. doi: 10.1021/am504231h. Epub 2014 Oct 14.
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.
尽管可溶液加工的高k无机电介质已被用作高性能、低成本过渡金属氧化物场效应晶体管（FET）的栅极绝缘体，但实现可接受绝缘性能所需的高温退火（>300°C）仍然限制了柔性电子器件的轻松实现。本研究报告称，向全氢聚硅氮烷（PHPS）溶液中添加2-二甲基氨基-1-丙醇（DMAPO）催化剂可使所得SiO2电介质的固化温度大幅降低至180°C。即使在极低的固化温度下，DMAPO的存在也极大地增强了旋涂PHPS膜在湿度条件下的水解和缩合，这使得所得SiO2介电膜具有光滑的表面（粗糙度为0.31nm）和可接受的泄漏特性（在1MV/cm电场下为1.8×10(-6)A/cm(2)）。尽管所得铟锌氧化物（IZO）FET表现出261.6cm(2)/(V s)的明显高迁移率，但由于硅氮烷衍生的SiO2膜的吸湿性，它们的开/关电流（ION/OFF）比低且滞后大。通过在180°C的低温下通过溶胶-凝胶工艺在溶液加工的SiO2膜上覆盖高k LaZrOx电介质，同时保持24.8cm(2)/(V s)的高迁移率，改善了IZO FET的ION/OFF值和滞后不稳定性。具有旋涂LaZrOx/SiO2双层栅极绝缘体的IZO FET的这种优异性能可归因于IZO沟道中In(3+)离子5s轨道的有效嵌入、IZO/LaZrOx的良好界面匹配以及PHPS衍生的SiO2介电膜的载流子阻挡能力。因此，可溶液加工的LaZrOx/SiO2叠层有望成为低温、高性能和低成本柔性金属氧化物FET的栅极电介质候选材料。
