Nonvolatile memory using Al2O3 film with an embedded Al-rich layer

Abstract

This letter describes the capacitance-voltage (C-V) characteristics of a new nonvolatile Al2O3 memory with nanoscale thin film deposited by electron-cyclotron-resonance sputtering. Al-rich Al2O3 was fabricated at a reduced oxygen gas flow rate and used as a charge storage layer of the Al2O3 memory, which is located between the tunnel insulator and blocking insulator. C-V characteristics show a large hysteresis window due to the Al-rich structure, but there is no hysteresis window in the case of stoichiometric Al2O3 structure. This memory will stay nonvolatile for several years or more. The number of electrons injected into the insulator in the case of nanoscale memory cell length is discussed. A discussion of the statistical Gaussian distribution indicates that about 50 localization sites are necessary in Al2O3 memory with 10nm cell length for realizing a 1.8V change of the threshold voltage, which corresponds to the control of ten electrons in the insulator. This structure is easily achieved by the proposed Al-rich Al2O3 memory.