Evaluation of HfAlO high-k materials for control dielectric applications in non-volatile memories

In this paper, we evaluate the potentiality of hafnium aluminium oxide (HfAlO) high-k materials for control dielectric application in non-volatile memories. We analyze the electrical properties (conduction and parasitic trapping) of HfAlO single layers and SiO₂/HfAlO/SiO₂ triple layer stacks as a function of the HfAlO thickness and Hf:Al ratio. A particular attention is given to the electrical behaviour of the samples at high temperature, up to 250 °C. Experimental results obtained on silicon nanocrystal memories demonstrate the high advantage of HfAlO based control dielectrics on the memory performances for Fowler-Nordheim operation. Then an analytical model is presented, to simulate the program erase characteristics in the transient regime and at saturation, depending on the high-k control dielectric properties. A very good agreement is obtained between the experimental data and the simulation results.