Abstract
The programming characteristics of charge trap flash memory device adopting amorphous In2Ga2ZnO7 (a-IGZO) oxide semiconductors as channel layer were evaluated. Metal-organic chemical vapor deposition (MOCVD) and RF-sputtering processes were used to grow 45nm-thick a-IGZO layer on 20nm-thick SiO2/p++-Si substrate, where the 5nm-thick low pressure CVD (LPCVD) SiO2 (tunneling oxide) and 15nm-thick LPCVD Si3N4 (charge trap) layers were intervened between the a-IGZO and substrate. Despite the identical stoichiometry and other physicochemical properties of MOCVD and sputtered a-IGZO, faster programming speed of MOCVD a-IGZO was observed. A comparable amount of oxygen vacancies was found in both MOCVD and sputtered a-IGZO, confirmed by X-ray photoelectron spectroscopy and bias-illumination- instability test measurements. Ultraviolet photoelectron spectroscopy analysis revealed the higher Fermi level (EF) of the MOCVD a-IGZO (~0.5eV) film compared with the sputtered a-IGZO. Since the programming in flash memory device is governed by the tunneling of electrons from channel to charge trapping layer, the faster programming performance could be the result of higher EF of MOCVD a-IGZO.