Al2O3/HfO2 MULTILAYER STACKS FOR NONVOLATILE FLASH MEMORY IT-05 APPLICATIONS

Abstract

Al2O3/HfO2 multilayer stacks deposited by atomic layer deposition (ALD) have been investigated from the view point of their application in emerging charge-trapping non-volatile flash memories. Dielectric and electrical properties, charge trapping, retention and endurance characteristics have been shown to depend strongly on the thickness of Al2O3 and HfO2 sublayers as well as on the post-deposition annealing (PDA) steps. O2 and N2 PDA introduce different kinds of electrically active defects in Al2O3/HfO2 stacks. The results give convincing evidence that PDA in O2 enhances substantially electron trapping in deep traps, hence charge storage ability of stacks. RTA in N2 results in negligible memory windows for thinner samples, i.e. it is not efficient in improving the charge storage ability. Multilayered HfO2/Al2O3 stacks have a potential for implementation as charge trapping layer in non-volatile memory devices and their charge storage ability could be tailored and enhanced by optimization of stack parameters as well as annealing processes.