Correlation between spin density and Vth instability of IGZO thin-film transistors

The electron spin resonance (ESR) detects point defect of the In-Ga-Zn oxide (IGZO) like singly ionized oxygen vacancies and excess oxygen, and get spin density as a parameter of defect state. So, we demonstrated the spin density measurement of the IGZO film with various deposition conditions and it has linear relationship. Moreover, we matched the spin density with the total BTS and the threshold voltage (V_th) distribution of the IGZO thin film transistors. The total BTS ΔV_th and the V_th distribution were degraded due to the spin density increases. The spin density is the useful indicator to predict V_th instability of IGZO TFTs.