P-si Material And Tft Devices

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.