双层结构对ZnO TFT稳定性的影响

Effect of double-layer structure on hysteretic stability of ZnO thin film transistors

室温下采用射频磁控溅射方法在SiO_(2)/Si衬底上沉积了单层ZnO薄膜和高氧/低氧双层ZnO薄膜,采用电子束蒸发设备蒸镀Al电极,制备单沟道ZnO TFTs和双层沟道ZnO TFTs。比较两种结构ZnO TFTs的各种性能参数,分析双层结构对TFTs产生的影响。实验结果表明,底部高含氧量ZnO层和顶部低含氧量ZnO层构成了DAL同质结且高氧/低氧薄膜存在载流子浓度产差,利用载流子从高浓度向低浓度扩散的性质,可以填补栅介电层和沟道层之间的界面态缺陷,使器件界面类受主陷阱减少,有效降低TFTs的滞回现象。与单有源层TFTs相比,双沟道层TFTs还具有电学调制作用,其电学性能和稳定性均有明显的提高,得到最佳TFTs的开/关电流比达到3.44×10^(9),亚阈值摆幅为0.68 V/dec,阈值电压偏移为1.2 V。

Single-layer ZnO thin films and oxygen-enriched/oxygen-depleted double-layer ZnO thin films were deposited on SiO_(2)/Si substrates by RF magnetron sputtering at room temperature,and Al electrodes were evaporated by electron beam evaporation equipment to prepare single-channel ZnO TFTs and double-channel ZnO TFTs.The performance parameters of ZnO TFTs with two structures are compared,and the influence of double-layer structure on TFT is analyzed.The experimental results show that,the high-oxygen ZnO layer at the bottom and the low-oxygen ZnO layer at the top form a DAL homogeneous junction.By using the carrier concentration difference in the high-oxygen/low-oxygen thin film,carriers diffuse from high concentration to low concentration,which can fill the interface defects between the gate dielectric layer and the channel layer,reduce the acceptor trap at the device interface and effectively reduce the hysteresis phenomenon of the TFTs.Compared with the single active layer TFTs,The double channel layer TFTs also has the function of electrical modulation,and its electrical performance and stability are obviously improved.The best TFTs has an on/off current ratio of 3.44×10^(9),a subthre-old swing of 0.68 V/dec and a threshold voltage offset of 1.2 V.