Fabrication of high-reliability Cu BCE-structure IGZO TFTs

Abstract

Back channel etched (BCE) amorphous InGaZnO (a-IGZO) can be fabricated with fewer photolithography masks and achieve smaller parasitic capacitance. However, the back channel of the BCE a-IGZO TFT is vulnerable to acid and plasma damage, which leads to problems of TFT uniformity and stability. In particular, with the introduction of gate driver on array (GOA) technology, it is increasingly urgent to improve the electrical uniformity and stability of TFTs. Therefore, it is an urgent requirement for technology and market to develop high reliability BCE IGZO TFTs. The electrical characteristic of the BCE configuration based a-IGZO TFTs were studied. The passivation layer, the selection of color filter material and design of GOA TFT structure were modified for lessening the influence of H2O molecules adsorbing on the back channel of the BCE-structure. The negative and positive bias temperature stress(N/PBTS) results revealed that the optimized GOA TFTs exhibited good device reliability-the Vth shift under gate voltage of -30 V at 80℃ is less than 1 V for 2 000 s. Finally, a high performance 215.9 mm(85 in) 8K4K 120 Hz GOA LCD was demonstrated.