Improvement of memory performance by high temperature annealing of the Al₂ O₃ blocking layer in a charge-trap type flash memory device

The effect of postdeposition annealing (PDA) of the Al₂ O ₃ blocking layer in a charge-trap type memory device is investigated. Significant improvements are achieved by high temperature PDA at 1100 °C, achieving faster operation speed, good charge retention, and a wide program/erase window. Experimental evidence shows that the underlying mechanism is not the changes in the band gap of the crystallized Al₂ O ₃ but is due to the higher trap density in the Si₃ N ₄ trapping layer at a deeper energy level by the intermixing between Al₂ O₃ and Si₃ N₄. The reduced trapping efficiency of the annealed Al₂ O₃ also helps improve the retention property.