Hydrogen behavior from ALD Al2O3 passivation layer for amorphous InGaZnO TFTs

The characteristics of amorphous indium gallium zinc oxide (a-InGaZnO) thin-film transistors (TFTs) fabricated using atomic layer deposition (ALD) Al
₂
O
₃
passivation layer and hydrogen distribution in a-InGaZnO were investigated by comparison with plasma enhanced chemical vapor deposition (PECVD) passivation layer. TFTs fabricated using PECVD passivation layer showed conductive or hump behavior, while that fabricated using ALD passivation layer showed enhancement type characteristics. According to secondary ion mass spectroscopy analysis, hydrogen was introduced into a-InGaZnO during PECVD, while it was hardly introduced during ALD regardless of considerable hydrogen in Al
₂
O
₃
. Thus, the behavior of hydrogen in a-InGaZnO is one possible cause of the difference in TFT characteristics between PECVD and ALD passivation.