Effects of charge storage dielectric thickness on hybrid gadolinium oxide nanocrystal and charge trapping nonvolatile memory

The characteristics of hybrid gadolinium oxide nanocrystal (Gd ₂O₃-NC) and gadolinium oxide charge trapping (Gd ₂O₃-CT) memories were investigated with different Gd ₂O₃ film thickness. By performing the rapid thermal annealing on Gd₂O₃ films with different thickness, the Gd₂O₃-NCs with the diameter of 6-9 nm for charge storage, surrounded by the amorphous Gd₂O₃ (α-Gd ₂O₃) layer, were formed. The α-Gd₂O ₃ layer was considered to be the charge trapping layer, resulting in the large memory window of Gd₂O₃-NC/CT memories with thick Gd₂O₃ film. The charge trapping energy level of the Gd₂O₃-NCs and α-Gd₂O₃ layer was extracted to be 0.16 and 0.45 eV respectively by using the temperature-dependent retention measurement. Further, after a 10⁶ program/erase cycling operation, the memory with thin Gd₂O ₃ film can be predicted to sustain a 94% memory window of the first cycling one while the memory with thick Gd₂O₃ film suffered from a 30% charge loss because of the traps within the α-Gd ₂O₃ layer. The Gd₂O₃ film thickness of 10 nm was optimized to exhibit superior performances of the Gd ₂O₃-NC/CT memory, which can be applied into the nonvolatile memory.