Effects of Ion Implantation Doping on the Characteristics of Amorphous Indium Gallium Zinc Oxide Thin Films

We propose ion implantation combined with thermal annealing as a doping process for amorphous indium gallium zinc oxide (a-IGZO) thin films to reduce parasitic series resistance and contact resistance of a-IGZO thin-film transistors (TFTs). Various dopants were considered, including Al, As, B, In, and Si implants, in this work. The resistivity and specific contact resistance values obtained were on the order of 10(-3) Omega cm and 10(-1) Omega cm(2), respectively. The carrier generation efficiency by ion implantation was almost 100%. The implanted ions were oxidized by thermal annealing, resulting in the formation of oxygen deficiencies in the a-IGZO network, as well as an increase (decrease) in the shallow (deep) tail states. Thus, control over the carrier density and gap states is possible using ion implantation and thermal annealing processes. Additionally, the high thermal stress resistance of the ion implantation process will facilitate device fabrication processes that require a large thermal budget. Therefore, our method should be useful in improving device performance and expanding applications of a-IGZO TFTs.