Possible model of degradation mechanism that increments the gate current (nonbiased interval) after constant-current stress

Abstract

This article evaluates the time evolution of stress-induced leakage current (SILC) in metal-oxide-semiconductor capacitors during unstressed interval after electrical stressing sub-5-nm-thick SiO2 films. It is demonstrated that the normalized increment in gate leakage current increases and then saturates as unstressed interval is increased; this characteristic is basically independent of electrical stress conditions. The experiment is carried out at various temperatures during the unstressed interval in order to identify the diffusive species in the oxide film that impact SILC evolution during the unstressed interval. Important chemical reactions are identified and several diffusion-reaction equations to be solved are elucidated. Numerical simulations of SILC evolution are performed assuming the diffusion-reaction equation of likely species. Simulation results reproduce the experimental results. The results suggest that the increment in SILC component is identical to the increment in Si–OH bond density, and that the Si–OH bonds (neutral E′ center) raise the conduction of tunneling electrons after the unstressed interval rather than the neutral electron traps that are generated by the electrical stress.