【作者】 刘传珍；

【导师】 黄锡珉；

【作者基本信息】 中国科学院长春光学精密机械与物理研究所 ， 凝聚态物理， 2000， 博士

【摘要】 多晶硅薄膜晶体管（p-Si TFT）液晶显示器可以实现高分辨率、高度集成同时有效降低显示器的功耗，因而成为目前有源矩阵液晶显示领域主要研究方向。本论文系统地研究了低温p-Si材料的制备以及TFT器件设计和制作工艺。 本文采用金属Ni诱导（Ni-MIC）和准分子激光退火（ELC）两种方式制备了高质量的多晶硅薄膜，填补了国内研究空白。采用XRD、SEM、XPS、Raman等分析手段，研究了薄膜的组份和结构。a-Si薄膜在Ni的诱导下，晶化温度降低到440℃，晶化时间缩短到2小时。研究结果表明：薄膜的平均晶粒尺寸为200nm左右，迁移率为20～30cm²/V·s。对晶化的机理研究表明，a-Si在低温下的晶化是由于形成了Ni的硅化物，其晶化的发生是由于NiSi₂的迁移，其迁移的驱动力是由亚稳态的a-Si转变为c-Si。开创性地研究了在电场下薄膜的晶化，观察到晶粒随着电场方向的择优快速生长特性，薄膜的晶化温度降低到400℃。此创新成果，对多晶硅的定向生长具有重要意义。 对p-Si TFT的器件与阵列设计进行了初步探讨，考虑TFT的开态、关态电流、寄生电容以及信号延迟等方面的影响。同时对器件工艺中a-Si：H、Ta₂O₅和SiN_x薄膜的制备工艺条件进行了优化。 采用Ni-MIC的方式设计制作了p-Si TFT，开态电流大于10^-5A，开关比大于10⁴，阈值电压在1.5V左右。建立了简单的p-Si TFT模型，对p-Si薄膜和p-SiTFT的电学特性进行了理论模拟和计算，计算结果和实验值相一致。 研究了激光退火的工艺条件以及多晶硅薄膜迁移率与薄膜的晶化质量和掺杂关系。提出了改善薄膜平均晶粒尺寸的措施。通过优化工艺条件，制备的薄膜的最大平均晶粒尺寸近1μm，迁移率为150～400cm²/V·s，比金属诱导制备的多晶硅薄膜的迁移率高，为目前最好的报道值。 讨论了AMLCD周边集成驱动电路中的延迟导致的输出信号的失真。对不同尺寸的几种高分辨率显示屏的缓冲寄存器TFT的R_n以及W/L进行了分析模拟。更多还原

【Abstract】 Poly-Silicon thin film transistor (p-Si TFT) addressing liquid crystal display has been currently the research and development focus in the field of fiat panel displays, as it is the most feasible approach to high resolution, high integration and low power consumption as a result of its high aperture ratio. In this thesis, large area p-Si films with high mobility have been made at lower temperature, and TFT array has been designed and fabricated for a 3in diagnal display.Firstly, high quality p-Si thin films are obtained using metal Ni induced crystallization (MIC) and excimer laser crystallization (ELC), respectively. The composition and structure of as-obtained films are analyzed with XRD, SEM, XPS. Raman Spectra etc. The Ni-MIC temperature is reduced to as low as 400 癈, and crystallization time is shortened to 2 hours. The mobility and grain size of p-Si films are 20-30c m2/Vs and 200nm, respectively, and the average grain size is dependent oh the process temperature and time. The mechanism of crystallization is discussed. The onset crystallization temperature of a-Si is effectively lowered due to the formation of Ni silicide, and the crystallization depends strongly on the migration of NiSi2 precipitates. Driving force for the migration of NiSi2 precipitates is the difference in free energy associated with the transformation of metastable a-Si to stable c-Si. The crystallization of the thin films in the field of electric is firstly . proposed.A p-Si TFT device is designed based on a full optimization with taking into account Ion, Ioff, parasitic capacitance, and process capability, etc. The technical condition of a-Si:H ,Ta205 and SiNx films are optimized.P-Si TFT is fabricated, where the p-Si film is obtained by Ni-MIC, and on-state current is more than 10~5A, the current ratio of on/off-state is more than 104, and threshold voltage is about 1.5V. A simplified electric model of p-Si TFT is proposed, and the electric property of the device is simulated. The simulated results are in good agreement with the experiments.Processing conditions of excimer laser annealing are optimized to obtain high quality p-Si films. The mobility of p-Si is related to the doping concentration, namely the PH3/SiH4 flux ratio. For improving the average grain size, the buffer layer of SiNxis adopted. The largest average grain sizes are near 1000nm, and the mobility of p-Si ranges from 150 to 400cm2/Vs, which is much more than that of Ni-MIC. This result is, to our knowledge, the highest reported value in this field.Output signal distort of the drive circuit due to RC delay in peripheral integrated AMLCD is discussed. The Rn of buffer TFT is simulated with respect to various display resolutions; and the channel width and length is discussed regarding the mobility.更多还原