Stability improvement of solution-processed IGZO TFTs by fluorine diffusion from a CYTOP passivation layer
Kyung‐Mo Jung, Jongsu Oh, Hyo Eun Kim, Ariadna Schuck, KyungRae Kim, KeeChan Park, Jae‐Hong Jeon, Soo‐Yeon Lee, Yong‐Sang Kim
Abstract
Abstract This study investigated the effects of fluorine (F) diffusion from a CYTOP passivation layer into amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The F contained in the CYTOP passivation layer was diffused into a-IGZO through 350 °C annealing. The similar ionic radii of F and oxygen (O) allowed the passivation of oxygen vacancy (V o ) and weakly bonded oxygen by F. As a result, the a-IGZO TFTs with CYTOP passivation were highly stable under various stresses. The threshold voltage (V th ) shifts of a-IGZO TFTs without CYTOP passivation and with CYTOP passivation under a negative bias stress test for 10 000 s were −6.7 V and −2.5 V, respectively. In addition, the V th shifts of each device under a negative bias illumination stress test for 4000 s were −10.9 V and −5.3 V, respectively. This improvement was caused by a reduction of V o and a widened band gap of a-IGZO through the F diffusion effect. In addition, the CYTOP passivation layer maintained excellent properties as a barrier against moisture after 350 °C annealing.