Performance and reliability improvement in poly-Si TFTs by fluorine implantation

High-performance and high-reliability TFTs were obtained using a fluorine ion implantation (FII) technique. The FII into the TFT gate poly-Si caused a positive Vth shift, increased the on current and decreased the leakage current significantly. Our investigation indicates that the Vth shift originates from negative charges generated in the gate oxide by the FII. The improvement of drain current are attributed to F passivation of trap states in the poly-Si and a modulation of offset potential due to the same negative charges under the offset region. Furthermore, high endurance for -BT stress and TDDB of the gate oxide was achieved by the FII. We consider that the strong Si-F bonds created by the FII raise the stress immunity. >