Understanding of Trap-Assisted Tunneling Current - Assisted by Oxygen Vacancies in RuOx/SrTiO3/TiN MIM Capacitor for the DRAM Application

A transient leakage current was measured as a function of time for thin (~9 nm) strontium titanate (STO) capacitor dielectrics with RuOx as a bottom electrode and TiN as a top electrode at different temperatures under constant direct current (DC) bias stress. With the space-charge-limited (SCL) current theory, the mobility of oxygen vacancies (VO) and the activation energy (E0) of VO were extracted. By closely examining the time-zero current-voltage (I-V) curves for a positively and a negatively held DC bias conditions before and after the stresses, an understanding of trap-assisted-tunneling (TAT) current, initiated by oxygen vacancies (VO) is presented. Based on this understanding, a way to further reduce the leakage current for a sub-10 nm dielectric film is provided.