Impact of AC Stress in Low Temperature Polycrystalline Silicon Thin Film Transistors Produced With Different Excimer Laser Annealing Energies

Abstract

This letter investigates degradation during alternating current (AC) operations in low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) produced using the selective excimer laser annealing (ELA). Different degrees of degradation, on-current increase and threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) shift were observed after AC operation stress in three devices with different ELA energies. Although a higher ELA energy device has a higher on-current, this will lead to higher protrusion and a stronger electrical field in the active layer. This stronger electrical field will cause serious electron trapping in the grain boundary trap (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">trap</sub> ), leading to more serious degradation than that found in the lower ELA energy devices. Finally, COMSOL simulations and C-V measurements were executed to verify the physical mechanism.