Ion shower doping of polysilicon films on polyethersulfone substrates for flexible TFT arrays

Abstract

A technique of ion shower doping was performed to form source-drain contacts for polysilicon thin-film transistors (TFTs) on polyethersulfone (PES) substrates. The doped layer was subsequently annealed with an excimer laser to electrically activate the dopant atoms. The doped polysilicon films on the PES substrate showed much higher sheet resistances than those on the glass substrate with the identical doping and activation conditions. Moreover, the plastic substrates is easily heated up and caused a film failure for the prolonged exposure of the ion shower doping. The effective doping time and the resulting ion dose could be increased remarkably by reducing the radio-frequency power as well as by inserting interval pulses for dopants relaxation during the ion doping. As a result, a sheet resistance value as low as 300 ohmssq. was obtained, which is low enough for a good ohmic contact. © 2006 The Electrochemical Society.