Large initial flatband voltage shifts in HfSiO2 high-k charge trapping memory

The impact of top blocking layers on initial flatband voltage are investigated in nMOS capacitors with a HfSiO2 charge-trapping layer for high-k charge trapping memory. We found that an initial flatband voltage that significantly affects the programing properties largely depends on the structure of the top blocking layers such as Al2O3 and stacked Al2O3/SiON/Al2O3. Our experimental results on the thickness dependence of each layer indicate that the initial flatband shift is related to oxygen vacancy formation in the HfSiO2 charge-trapping layer. The SiON thickness in the top blocking layer is a key factor in the control of the initial flatband voltage.