ポリシルセスキオキサンゲート絶縁膜の表面平坦化によるペンタセン薄膜トランジスタのキャリア移動度の向上

The surface flatness of photo-curable polysilsesquioxane (PSQ) films for gate dielectric layers of pentacene thin film transistors (TFTs) was considerably improved by ultra-violet light (UV)/O3 treatment; the root-mean-squared (RMS) roughness was improved from 0.35 to 0.23 nm after 40-minute treatment. However, the PSQ surfaces became hydrophilic because hydroxyl groups, which degraded transistor performances, replaced the organic functional groups such as methyl groups by the UV/O3 treatment. Therefore, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) treatment was successively performed after the UV/O3 treatment to replace the hydroxyl groups with hydrophobic silyl groups. It was found that four-hour HMDS treatment under dry nitrogen was enough to reduce off current of pentacene TFTs. As a result, the carrier mobility of the pentacene TFT fabricated with UV/O3 and HMDS-treated PSQ layers became 0.59 cm2V-1s-1, which was more than seven times higher than that of the pentacene TFTs with untreated PSQ layers.