As a potential alternative to flash memory, HfO2/Al2O3 stacks appear to be a viable option as charge capture layers in charge trapping memories. The paper undertakes a review of HfO2/Al2O3 stacks as charge trapping layers, with a focus on comparing the number, thickness, and post-deposition heat treatment and γ-ray and white x-ray treatment of such stacks. Compared to a single HfO2 layer, the memory window of the 5-layered stack increased by 152.4% after O2 annealing at ±12 V. The memory window enlarged with the increase in number of layers in the stack and the increase in the Al/Hf content in the stack. Furthermore, our comparison of the treatment of HfO2/Al2O3 stacks with varying annealing temperatures revealed that an increased annealing temperature resulted in a wider storage window. The samples treated with O2 and subjected to various γ radiation intensities displayed superior resistance. and the memory window increased to 12.6 V at ±16 V for 100 kGy radiation intensity compared to the untreated samples. It has also been established that increasing doses of white x-rays induced a greater number of deep defects. The optimization of stacking layers along with post-deposition treatment condition can play significant role in extending the memory window.
