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Nonvolatile memory devices with AlOx embedded Zr-doped HfO2 high-k gate dielectric stack J. Vac. Sci. Technol. B 32, 03D116 (2014); 10.1116/1.4867170The effect of thermal treatment induced inter-diffusion at the interfaces on the charge trapping performance of HfO2/Al2O3 nanolaminate-based memory devices

The charge trapping memory devices based on different HfO2/Al2O3 nanolaminated charge trapping layers were prepared and investigated. The memory device with 6 interfaces HfO2/Al2O3 shows a memory window of 4.7 V in its capacitance-voltage curve and a better retention property. It was suggested that the thermal treatment would reduce the defects inside the bulk HfO2, but cause an inter-diffusion at the interface HfO2/Al2O3, which could create additional defects at HfO2/Al2O3 interface. Increasing the number of the interfaces could enhance the charge trapping capability of the devices. The band alignments were established to explain the variation trend of the memory window and the retention characteristics of the memory devices with different laminated structures.

A memory device p-Si/SiO2/(TiO2)0.8(Al2O3)0.1(TAO-81)/Al2O3/Pt was fabricated, in which a composite of two high-k dielectrics with a thickness of 1 nm was employed as the charge-trapping layer to enhance the charge-trapping efficiency of the memory device. At an applied gate voltage of ±9 V, TAO-81 memory device shows a memory window of 8.83 V in its C-V curve. It also shows a fast response to a short voltage pulse of 10−5 s. The charge-trapping capability, the endurance, and retention characteristics of TAO-81 memory device can be improved by introducing double TAO-81 charge-trapping layers intercalated by an Al2O3 layer. The charge-trapping mechanism in the memory device is mainly ascribed to the generation of the electron-occupied defect level in the band gap of Al2O3 induced by the inter-diffusion between TiO2 and Al2O3.