Fabrication of excimer laser annealed poly-Si thin film transistor by using an elevated temperature ion shower doping

Abstract

We have investigated the effect of an ion shower doping of laser annealed poly-Si films at elevated substrate temperatures. The substrate temperature was varied from room temperature to 300 degrees C when the poly-Si film was doped with phosphorus by a non-mass-separated ion shower. Optical, structural, and electrical characterizations have been performed in order to study the effect of the ion shower doping. The sheet resistance of the doped poly-Si films was decreased from 7 x 10(6) Omega/sq to 700 Omega/sq when the substrate temperature was increased from room temperature to 300 degrees C. This large change in sheet resistance is due to the fact that the doped films do not become amorphous but remain in the polycrystallinephase. The mildly elevated substrate heating appears to contribute mainly to reduction of ion damages incurred in the poly-Si films in addition to the activation of dopants during the ion shower doping. From the fabricated n-channel poly-Si TFTs, the current crowding effect do not occur because of the low contact source-drain resistance and the field effect mobility of 120 cm(2)/(V s) has been obtained. (C) 1997 Published by Elsevier Science S.A.