Low frequency noise in polysilicon thin film transistors: effect of the laser annealing of the active layer

Abstract

AbstractLow‐frequency noise is studied in N‐channel polysilicon TFTs issued from two (low temperature ≤600 °C) technologies: furnace solid phase crystallized (FSPC) and laser solid phase crystallized (LSPC) TFTs. The distribution of the trap states (DOS) into the polysilicon bandgap determined for devices biased in the weak inversion is one decade lower for LSPC devices. The high range values (10–4 ≤ α ≤ 1) of the measured macroscopic noise parameter, defined according to the Hooge empirical relationship, are explained by the drain current crowding due to structural defects within the active layer. The higher values of α for the LSPC TFTs are attributed to a better structural quality of the active layer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)