非晶铟锌氧化物薄膜晶体管的研究

【作者】 周俊；

【导师】 张群；

【作者基本信息】 复旦大学 ， 物理电子学， 2010， 硕士

【摘要】 本文重点对以铟锌氧化物作为沟道层的氧化物薄膜晶体管进行研究,首先进行了沟道层、绝缘层材料的制备和性能分析,然后再结合掩模制备了薄膜晶体管器件,从沟道层制备条件、器件结构方面对薄膜晶体管性能进行了优化。首先,在室温下于玻璃基板上采用直流反应磁控溅射In/Zn合金靶材制备了IZO薄膜。测试表明所制备的IZO薄膜均为非晶结构,且表面平整。通过在沉积过程中适当调节氧气压强,a-IZO薄膜电阻率可以在10-3～106Ω·cm范围变化；α-IZO薄膜具有良好的光学透明性,在可见光范围内平均透射率可达87%；通过拟合外推计算得到α-IZO薄膜的光学禁带宽度大致为3.34～3.62 eV,介于In2O3和ZnO之间。直流反应磁控溅射制备的α-IZO薄膜在光学性能和电学性能方面均能满足薄膜晶体管的要求。其次,在室温下于玻璃基板上采用脉冲等离子体沉积法制备了Si02薄膜。通过电容-电压测试计算得到在氧气压强为2.4×10-2Pa,2.6×10-2Pa,2.8×10-2Pa三种条件下制备的SiO2薄膜的相对介电常数分别为3.82、3.88、3.92；SiO2薄膜具有良好的光学透明性,在可见光范围内平均透射率可达87%。脉冲等离子体沉积法制备的SiO2薄膜具有较好的光学性能和介电性能,有希望作为绝缘层应用于薄膜晶体管。最后,基于沟道层和绝缘层研究之上结合掩模制备了薄膜晶体管,研究了沟道层制备条件以及器件结构对薄膜晶体管性能的影响,得到以下结论：1)以5.0×10-2Pa氧气压强制备的α-IZO作为沟道层的薄膜晶体管的输出特性最佳,具有明显的饱和现象,并且在相同的偏压下具有较大的输出电流；所以认为5.0×10-2Pa的氧气压强是制备α-IZO沟道层的最佳条件。2)由于具有较为平整的沟道层-绝缘层界面,顶栅结构薄膜晶体管各项性能全面优于底栅结构薄膜晶体管。该薄膜晶体管工作在n型沟道增强模式,电流开关比约为103,阈值电压Vth,为0.57 V,场效应迁移率为4.08cm2v-1s-1。更多还原

【Abstract】 Thin film transistors (TFTs) based on indium zinc oxide as channel layer were studied in this thesis.The channel layer and dielectric layer were fabricated and characterized, respectively. Thin film transistors were fabricated with shadow mask. The performance of device was improved by optimizing the deposition parameter of channel layer and configuration of TFTs.Firstly, indium zinc oxide (IZO) thin films were deposited on glass substrates by DC reactive magnetron sputtering at room temperature. The structure of IZO films is amorphous, and the surface of IZO films is smooth. The resistivity of the thin films can be adjusted from 10-3 to 106 Q-cm through the proper control of the oxygen pressure during the deposition process.As-deposited amorphous IZO (a-IZO) films show high optical transmission, the average transmittance in the visible region is about 87%,and the optical band gap exhibits from 3.34 eV to 3.62 eV, which is between zinc oxide and indium oxide. a-IZO films deposited by DC reactive magnetron sputtering show good semi-conductive and optical properties which can satisfy the requirements of TFTs.Secondly, SiO2 films were deposited on glass substrates by pulsed plasma deposition (PPD) at room temperature. For the SiO2 films deposited at oxygen pressure of 2.4×10-2 Pa,2.6×10-2 Pa and 2.8×10-2 Pa, the relative dielectric constant was 3.82,3.88 and 3.92,respectively. SiO2 films also show high optical transmission, the average transmittance in the visible region is about 87%.SiO2 films deposited by PPD show good dielectric and optical properties, which have potential application in TFT as insulator layer.Finally, TFTs were fabricated using shadow mask based on the studies of channel layer and dielectric layer. The dependence of performance on the deposition parameter of channel layer and configuration of TFTs were investigated in detail. The main results show that:1) TFTs with a-IZO channel layer which were deposited at oxygen pressure of 5.0×10-2 Pa show the best output characteristics with distinct saturation and the largest output current at the same bias voltage. Oxygen pressure of 5.0×10-2 Pa was considered as the optimal parameter to depositα-IZO channel layer.2) With smoother interface between channel layer and dielectric layer, the performance of top-gated TFT was better than bottom-gated TFT. The top-gated TFT operated in n-type enhancement mode with a field-effect mobility of 4.08 cm2V-1s-1, an on-off current ratio of 103 and a threshold voltage of 0.57.更多还原