Investigation of Carrier Generation Mechanism in Fluorine-Doped n+-In-Ga-Zn-O for Self-Aligned Thin-Film Transistors

We investigated the carrier generation mechanism in the stacked film of fluorinated silicon nitride SiNx:F on InGaZnO IGZO/SiNx: F through post-annealing and compared its mechanism to that of the SiOx stack (GZO/SiOx). The resistivity and carrier concentration of two types of the stacked films through post-annealing were measured by the Hall measurement. The as-deposited n(+) a-IGZO film with the SiNx stack showed rho of 3.3 x 10(-3) Omega . cm and n of 1.0 x 10(20) cm(-3), which was approximately one order of magnitude higher than that with the SiOx stack. X-ray photoelectron spectroscopy (XPS) analyses indicated that V-O defect was the main source of free electrons in both of the as-deposited IGZO/SiO and IGZO/SiNx:F stacks. After post-annealing at 300 degrees C, the carrier generation mechanism in the IGZO/SiNx:F stack changed from defects related to V-O to the fluorine doping. XPS depth profile analyses also revealed that fluorine in IGZO film passivated V-O and substituted metal-oxygen to thermally stable metal-fluorine (M-F) bonds simultaneously. As a consequence, the thermal stability of in the IGZO/SiNx:F stack drastically improved, as compared with that in the IGZO/SiOx stack. Therefore, we consider that this fluorine doping method in IGZO is suitable for achieving self-aligned thin-film transistors [1] to improve operation speed of system-in-display.