| TFT( Thin Film Transistor )is widely used for displays. The main TFT is a-Si:H TFT which is switching device of active matrix liquid crystal display. With the wide application of a-Si:H TFT, the establishment of its models becomes a very important question for study. Accurate a-Si:H TFT models are required for SPICE simulators. Several papers have already been published regarding the physics and the models of a-Si:H TFT, but they are insufficient for today's advanced LCD simulations.This thesis mainly studied SPICE model for a-Si:H TFT, which is a part of national "863" project, "Study of Large Size and high quality a-Si TFT-OLED technology". The analysis and models are applicable to the simulation of today's optical characterizations of Flat-Panel-Displays.In this thesis, the new models of a-Si:H TFT are established for SPICE, on the basis of inverted-stagger structure a-Si:H TFT of back channel stopped types. Current-voltage and capacitance-voltage are also tested. From the capacitance curve, the process parameters are extracted, such as dopant concentration, fixed charge density, interface state, etc. This paper analyzed localized state, sub-threshold current, off-leakage current, the field effect mobility, bias- and frequency-dependent capacitance, the threshold voltage change with voltage stress and device temperature, etc. This thesis focuses on the establishment of new drain current models in the linear region, the saturation region, the forward and reverse sub-threshold region, and new off-leakage current models in the off region on based of MOSFET model. In addition, the precise bias- and frequency-dependent MIS capacitance models are established. Some model parameters are extracted, such as threshold voltage(VTO), mobility(μ0) etc. Simulation results by using these models and parameters show good agreement between measured and simulated data. The models are applicable to the a-Si:H TFT devices with different process structures. The modeling procedure is useful to TFT designers. |
