有源层厚度对ZnO薄膜晶体管电学性能的影响

Effects of Active Layer Thickness on Electrical Properties of ZnO Thin-Film Transistors

为优化氧化锌薄膜晶体管(ZnO-TFT)的工艺参数,采用射频磁控溅射法沉积ZnO薄膜制备出不同有源层厚度的ZnO-TFT器件,探讨了有源层厚度对ZnO-TFT电学性能的影响.实验结果表明:有源层厚度在65nm附近时,ZnO-TFT器件的性能最好;有源层太薄时,ZnO薄膜的结晶性差,薄膜内部存在大量孔洞和缺陷,从而导致ZnO-TFT器件的载流子迁移率较低,开关电流比较小;有源层太厚(大于65 nm)时,ZnO-TFT的载流子迁移率和开关电流比随有源层厚度的增加而减小,这是因为随着有源层厚度的增加,载流子在源、漏电极附近高电阻区的导电路径增加.

In order to optimize the processing parameters of ZnO thin-film transistors （ZnO-TFTs）,ZnO-TFTs were fabricated by means of RF （Radio Frequency） magnetron sputtering,with the ZnO thin-films of different thickness as the active layer,and the effects of the active layer thickness on the electrical properties of ZnO-TFTs were investigated.Experimental results indicate that （1） the ZnO-TFT device shows the best performance at the active layer thickness of about 65 nm; （2） when the active layer is too thin,the ZnO film is of a poor crystallinity and is of a large number of holes and defects,thus resulting in a lower carrier mobility and a smaller on/off current ratio ; and （3） when the active layer is too thick （more than 65 nm）,the carrier mobility and on/off current ratio of the ZnO-TFT decrease with the increase of the active layer thickness,because the conductive path of high resistance region near the source and the drain electrodes increases with the increase of the active layer thickness.