P‐7.2: Suppression of Ion Drop of ITO‐Decapped a:Si‐H TFT for ADS Pro Display

Abstract

The decay of Ion of ADS Pro‐type TFTs experienced 1ITO decap often brings about a lot of TFT devices scrapped. It is necessary and valuable to identify the reasons and to solve the Ion drop problem induced by decap. In the present work, the difference in procedure and electronic performance between the normal and the decap TFT process was first compared, then a series of controlled and confirmation experiments to get the mechanism of Ion drop were designed and carried out. It is found that not the extra etching, but the additional ITO film deposition procedure in the decap process is the cause of Ion degradation; during ITO deposition process, the plasma cleaning would lead to the plasma damage to the silicon island, and the In and O atoms in ITO target would intrude into the silicon to form p‐type doping or SiOx oxide, giving rise to the decrease of the carrier concentration and the increase of the resistance, which eventually account for the Ion drop. Finally, the measures to suppress the Ion degradation caused by 1ITO decap were proposed and verified, it shows that the decay percentage of Ion will decline from 15% in the normal decap process to 8.9%, 12.2% and 10.6% by turning off the plasma cleaning, cutting down the deposition power, and reducing the ITO annealing temperature, respectively. And when these three above methods are combined introduction together, the Ion drop after decap can be further lower to less than 5%, which meets the requirements of mass production. This study provides a way to suppress Ion degradation and a reference to optimize TFT properties and improve product yield.