Stress-induced leakage current of tunnel oxide derived from flash memory read-disturb characteristics

This paper describes the characteristics of the stress-induced leakage current of tunnel oxide derived from flash memory read-disturb characteristics. The following three items were newly observed. First, the threshold voltage shift (ΔV_th) of the memory cell under the gate bias condition (read disturb condition) consists of two regions, a decay region and a steady-state region. The decay region is due to both the initial trapping or detrapping of the carriers in the tunnel oxide and the decay of the stress-induced leakage current of the tunnel oxide. The steady-state region is determined by the saturation of the stress-induced leakage current of the tunnel oxide. Second, the read disturb life time is mainly determined by the steady-state region for the oxide thickness of 5.7-10.6 nm investigated here. Third, a high-temperature (125°C) write/erase operation degrades the steady-state region characteristics in comparison with room temperature (30°C) operation. Therefore, accelerated write/erase tests can be carried out at higher operation temperatures