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 are newly observed. First, the threshold voltage shift (ΔVth) of the memory cell under gate stress 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 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