Effect of excimer laser annealing on the structural and electrical properties of polycrystalline silicon thin-film transistors

The structural and electrical properties of excimer laser annealed polycrys talline silicon thin-film transistors (polysilicon TFTs) are investigated i n relation to the laser energy density. The devices were fabricated on 50 n m thick polysilicon films prepared by excimer laser crystallization (ELA) o f amorphous silicon or by a combined solid phase crystallization (SPC) and ELA process. The structural properties of the polysilicon films have been i nvestigated by transmission electron microscopy analysis. The effective den sity of states distributions in the polysilicon films and in the oxide trap s near the oxide/polysilicon interface have been determined from low freque ncy noise measurements. The TFT performance parameters are compared with re spect to their correlation with the structural properties of the polysilico n films and their electrically active defects, the basic variables being th e starting material (amorphous silicon or SPC polysilicon) and the laser en ergy density. (C) 1999 American Institute of Physics. [S0021-8979(99)08620- X].