The Elimination of Ion Implantation Damage at the Source/Drain Junction of Poly-Si TFTs

Abstract

AbstractWe report a new poly-Si TFT, of which the troublesome implantation damage near the source/drain junction was eliminated, by performing source/drain ion implantation as well as excimer laser annealing (ELA) prior to the gate formation. The recrystallization of a-Si in the channel region and the dopant activation in the source/drain region were simultaneously accomplished by single ELA process step so that the implantation damage, which results in large leakage current of TFT, has been successfully eliminated. TEM image verifies that large poly-Si grains were successfully grown from the ion implanted source/drain region to the channel region. The proposed poly-Si TFT, of which mobility is 171 cm2/Vs, exhibits a large on/off current ratio exceeding 4.1 × 107 without LDD or offset structure while those of the conventional TFT, which has been fabricated simultaneously for the comparison purpose, are 86 cm2/Vs and 6.1 × 106.