A novel method for a smooth interface at poly-SiOx/SiO2 by employing selective etching

We have investigated the excimer laser recrystallization of slightly oxygen-added amorphous silicon (a-SiO/sub x/) films for the application to the active layer of thin film transistors. We also propose a new method to reduce the surface roughness of poly-SiO/sub x/ films by etching the grain boundaries selectively. SEM images show that the Si-O bonds are well segregated into the poly-Si grain boundaries after laser crystallization and the surface morphology is remarkably improved after the selective buffered oxide etchant (BOE) etching of the grain boundaries. The electrical conductivity measurement shows that the activation energies of poly-SiO/sub x/ and poly-Si films have an identical value of 0.52 eV. This may confirm that oxygen-induced defects do not cause any difference in the electrical performance even at the oxygen concentration of 0.18 at.%. Moreover, the electrical mobility and subthreshold slope of poly-SiO/sub x/ TFTs are considerably improved by employing the proposed method, which smooths the poly-SiO/sub x//SiO/sub 2/ interface.