Abstract
A nano-floating gate memory structure based on Ni nanocrystals (NCs) embedded HfOx film is deposited by means of radio-frequency magnetron sputtering. Microstructure investigations reveal that self-organized Ni-NCs with diameters of 4-8 nm are well dispersed in amorphous HfOx matrix. Pt/Ni-NCs embedded HfOx/Si/Ag capacitor structures exhibit voltage-dependent capacitance-voltage hysteresis, and a maximum flat-band voltage shift of 1.5 V, corresponding to a charge storage density of 6.0 × 1012 electrons/cm2, is achieved. These capacitor memory cells exhibit good endurance characteristic up to 4 × 104 cycles and excellent retention performance of 105 s, fulfilling the requirements of next generation non-volatile memory devices. Schottky tunneling is proven to be responsible for electrons tunneling in these capacitors.
Highlights
Since mid-1990s, nano-floating gate nonvolatile memory (NFG-NVM) devices based on complementary metal-oxide-semiconductor (MOS) field effect transistor structure have been extensively studied for potential application in generation flash memory device.[1]
A nano-floating gate memory structure based on Ni nanocrystals (NCs) embedded HfOx film is deposited by means of radio-frequency magnetron sputtering
Ni2p core level spectra (fig. 2(c)) further demonstrate the coexistence of Ni and NiOx-NCs, implying the partial oxidization of Ni nanocrystals (Ni-NCs) in amorphous HfO2 matrix during the process of deposition and annealing, but Ni-NCs are dominated in memory layer II, Strong Si0 peak (∼ 99.6 eV) originated from Si substrate is absent until the sample is etched to the interfacial layer IV(fig. 2(d)), illustrating that there are no Si atoms diffused into the HfOx matrix
Summary
Since mid-1990s, nano-floating gate nonvolatile memory (NFG-NVM) devices based on complementary metal-oxide-semiconductor (MOS) field effect transistor structure have been extensively studied for potential application in generation flash memory device.[1]. Due to the oxidization of Ni-NCs in oxide matrix and diversify of nickel oxides, the endurance and retention properties for Ni-NCs-based memory cell need to be further improved. Their tunneling mechanisms are still unclear, and effects of temperature on its leakage current characteristics are rarely discussed. Since HfOx films deposited by sputtering are usually oxygen-deficient, so the film prefers to capture diffused oxygen atoms in the oxide matrix; this may suppress the oxidization of embedded Ni-NCs. Microstructure, charge storage, endurance, retention, tunneling mechanism and temperature-dependent leakage current characteristics of the memory celled based on this capacitor structure have been studied
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