Field-Effect Mobility Enhancement in Low Temperature ALD ZnO Thin-film Transistors via Contact Defects Engineering Suitable for BEOL Integration

Low temperature ZnO thin-film transistors suitable for beyond Backend-of-line integration were fabricated using low-temperature atomic layer deposition process. Using O-2/Ar plasma to engineer defects density at the contacts, significant contact resistance reduction to 0.44 k Omega/mu m (83%) was achieved. Consequently, the field-effect mobility improves >1 order to 23.7 cm(2)/V.s. The enhancement is due to several factors including ZnO crystallinity, smooth interface layer, and appropriate stiochiometry as characterized via XRD, AFM and XPS.