Extraction method for polycrystalline TFT above and below threshold model parameters

A procedure is presented to extract above and sub-threshold model parameters in polysilicon TFTs. It is based on the integration of the experimental data current, which has the advantage of reducing the effects of experimental noise. This method is applied to the linear and saturation regions for the above-threshold regime and allows the extraction of all the above-threshold and sub-threshold parameters. We already presented a unified extraction method for the above threshold parameters of a-Si:H and polysilicon TFTs, where the above-threshold regime the mobility is modeled as a function of the gate voltage to a power. An integration procedure is used to extract the device model parameters. In this paper, we complete the extraction procedure to cover all the device operation regions, that is the sub-threshold and above-threshold regimes. The extraction procedure provides in addition the possibility of monitoring the crystallization process of a-Si:H TFTs into polysilicon, which has become a widely used process of fabricating low temperature polysilicon TFTs. The process of polycrystallization manifests itself by a variation and change in sign of one of the model parameters. Extracted parameters can be correlated to input parameters required by AIM-Spice circuit simulator for device modeling. The accuracy of the simulated curves using the extracted parameters is verified with measurements. (C) 2002 Elsevier Science Ltd. All rights reserved.