FABRICATION OF EXCIMER-LASER ANNEALED POLY-SI THIN-FILM-TRANSISTOR BYUSING AN ELEVATED-TEMPERATURE ION SHOWER DOPING

We have investigated the effect of an ion shower doping of laser annea led poly-Si films at elevated substrate temperatures. The substrate te mperature was varied from room temperature to 300 degrees C when the p oly-Si film was doped with phosphorus by a non-mass-separated ion show er. Optical, structural, and electrical characterizations have been pe rformed in order to study the effect of the ion shower doping. The she et 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 res istance is due to the fact that the doped films do not become amorphou s but remain in the polycrystallinephase. The mildly elevated substrat e heating appears to contribute mainly to reduction of ion damages inc urred in the poly-Si films in addition to the activation of dopants du ring 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.