Nonvolatile Memory With Nitrogen-Stabilized Cubic-Phase ZrO2 as Charge-Trapping Layer

A cubic ZrO2 film formed by annealing of amorphous ZrON has been investigated as the charge-trapping layer for nonvolatile memory. The memory with a nitrogen-stabilized cubic ZrO2 film shows promising performance in terms of 3.81-V hysteresis memory window by +/- 7-V program/erase voltage and 1.98-V flatband-voltage shift by programming at + 7 V for 10 ms. As compared to that with an amorphous ZrON film, the improved performance is due to the greatly enhanced kappa-value of 32.8 and the increased trapping sites provided by grain boundaries. Additionally, it shows 28.6% charge loss after ten-year operation at 85 degrees C. Although it is worse than that with an amorphous ZrON film, it is advantageous over an atomic-layer-deposition-grown tetragonal ZrO2 film in terms of reduced leakage current. Improved retention can be accomplished by passivation of grain boundaries and/or high-kappa double quantum barrier as the tunnel and blocking dielectric.