X. D. Huang

Fluorinated

Charge-trapping properties of SrTiO₃ with and without fluorine incorporation are investigated by using an Al/Al₂O₃/SrTiO₃/SiO₂/Si structure. The memory device with a fluorinated SrTiO₃ film shows promising performance in terms of large memory window (8.8 V) by ±8-V sweeping voltage, large flatband-voltage (V_FB) shift (2.5 V) at a low gate voltage of +6 V for 1 ms, negligible V_FB shift after 10⁵-cycle program/erase stressing, and improved data retention compared with that with out fluorine treatment. These advantages can be associated with generated deep-level traps, reduced leakage path, and enhanced strength of the film due to the fluorine incorporation.

\hbox{SrTiO}_{3}

The effects of fluorine treatment on the charge-trapping characteristics of thin ZrO2 film are investigated by physical and electrical characterization techniques. The formation of silicate interlayer at the ZrO2/SiO2 interface is effectively suppressed by fluorine passivation. However, excessive fluorine diffusion into the Si substrate deteriorates the quality of the SiO2/Si interface. Compared with the ZrO2-based memory devices with no or excessive fluorine treatment, the one with suitable fluorine-treatment time shows higher operating speed and better retention due to less resistance of built-in electric field (formed by trapped electrons) against electron injection from the substrate and smaller trap-assisted tunneling leakage, resulting from improved ZrO2/SiO2 and SiO2/Si interfaces.

as Charge-Trapping Layer for Nonvolatile Memory Applications

Charge-trapping characteristics of SrTiO3 with and without nitrogen incorporation were investigated based on Al/Al2O3/SrTiO3/SiO2/Si (MONOS) capacitors. A Ti-silicate interlayer at the SrTiO3/SiO2 interface was confirmed by x-ray photoelectron spectroscopy and transmission electron microscopy. Compared with the MONOS capacitor with SrTiO3 as charge-trapping layer (CTL), the one with nitrided SrTiO3 showed a larger memory window (8.4 V at ±10 V sweeping voltage), higher P/E speeds (1.8 V at 1 ms +8 V) and better retention properties (charge loss of 38% after 104 s), due to the nitrided SrTiO3 film exhibiting higher dielectric constant, higher deep-level traps induced by nitrogen incorporation, and suppressed formation of Ti silicate between the CTL and SiO2 by nitrogen passivation.

Charge-trapping characteristics of fluorinated thin ZrO2 film for nonvolatile memory applications

The charge-trapping properties of HfYON film are investigated by using the Al/HfYON/SiO2/Si structure. The physical features of this film were explored by transmission electron microscopy and x-ray photoelectron spectroscopy. The proposed device shows better charge-trapping characteristics than samples with HfON or Y2O3 as the charge-trapping layer due to its higher trapping efficiency, as confirmed by extracting their charge-trap centroid and charge-trap density. Moreover, the Al/Al2O3/HfYON/SiO2/Si structure shows high program speed (4.5 V at +14 V, 1 ms), large memory window (6.0 V at ±14 V, 1 s), and good retention property, further demonstrating that HfYON is a promising candidate as the charge-trapping layer for nonvolatile memory applications.

Nitrided SrTiO3 as charge-trapping layer for nonvolatile memory applications

The effects of positive gate-bias stress (PGBS) and temperature on the electrical instability of amorphous InGaZnO thin-film transistor with a thin ZrLaO film as gate dielectric were investigated. An abnormal negative PGBS-induced Vth shift (ΔVth, up to -3.3 V) without subthreshold swing (SS) degradation was found at 300 K, while a positive PGBS-induced ΔVth (+1.0 V at 250 K and +0.7 V at 200 K) without SS degradation appeared at low temperature. The negative PGBS-induced ΔVth at 300 K is due to carrier creation in the InGaZnO film, which is mainly resulted from the enhanced control ability of the gate on the channel by using thin high-k ZrLaO as the gate dielectric of the transistor. The positive PGBS-induced ΔVth at low temperature is caused by electron trapping happening near the ZrLaO/InGaZnO interface at low temperature.

Improved charge-trapping properties of HfYON film for nonvolatile memory applications in comparison with HfON and Y2O3 films

The charge-trapping properties of Gd2O3 with different Nb doping levels are investigated using an Al/Al2O3/Gd2O3/SiO2/Si structure. Compared with the memory device with pure Gd2O3, the one with lightly Nb-doped Gd2O3 shows better charge-trapping characteristics, including higher programming speed (6.5 V at +12 V programming voltage for 10 ms) and better retention property (92% retained charge at 85 °C after 104 s), due to its higher trapping efficiency that resulted from higher trap density and suppressed formation of a silicate interlayer at the Gd2O3/SiO2 interface induced by the Nb doping. Moreover, the one with heavily Nb-doped Gd2O3 shows improvement in erasing behavior but worse retention and lower programming speed than the one with lightly Nb-doped Gd2O3. Further analysis reveals that the Nb-doping level determines the type of dominant trap in the Nb-doped Gd2O3, thus leading to different charge-loss mechanisms and charge-trapping characteristics.

Positive Gate Bias and Temperature-Induced Instability of

The charge-trapping characteristics of Ga₂O₃ (Gd₂O₃) (denoted as GGO) with and without nitrogen incorporation were investigated based on Al/Al₂O₃/GGO/SiO₂/Si (metalalumina-nitride-oxide-silicon) capacitors. Compared with the capacitor without nitrogen incorporation, the one with nitrided GGO showed a larger memory window (10 V at ±16 V, 1 s), a higher program speed with a low gate voltage (2.2V at +8 V, 100 μs), and a better retention property (charge loss of 9.7% after 104 s at 125°C) mainly due to higher charge-trapping efficiency of the nitrided GGO film and the nitrogen-induced suppressed formation of the undesirable silicate interlayer at the GGO/SiO₂ interface, as confirmed by the transmission electron microscopy and the X-ray photoelectron spectroscopy.

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The origin of positive-gate-bias-stress (PGBS)-induced instability and the effects of fluorine treatment on the instability of an InGaZnO thin-film transistor (TFT) are investigated. The fluorine treatments on the dielectric/InGaZnO interface and InGaZnO back channel of the device can effectively modulate their electrical properties. By characterizing the TFTs with various fluorine treatments, it is found that the back channel rather than the dielectric/InGaZnO interface dominates the PGBS instability. Electrons induced by moisture absorption near the back channel migrate from the back channel to the interface under PGBS at room temperature, thus resulting in a threshold-voltage decrease. Moreover, the fluorine treatment on the back channel effectively suppresses the PGBS instability due to reduced moisture absorption caused by the fluorine passivation.

-InGaZnO Thin-Film Transistor With ZrLaO Gate Dielectric

Yttrium-doped Al₂O₃ (Y_xAI_yO) with different yttrium contents prepared by co-sputtering method is investigated as the inter-poly dielectric (IPD) for flash memory applications. A poor SiO₂-like interlayer formed at the IPD/Si interface is confirmed by X-ray photoelectron spectroscopy, and can be sup pressed by Y doping through the transformation of silica into silicate. Compared with Al₂O₃ and Y₂O₃ films, the optimized Y_xAI_yO film shows lower interface-state density, lower bulk charge-trapping density, higher dielectric constant, and smaller gate leakage, due to the suppressed interlayer and good thermal property ascribed to appropriate Y and Al contents in the film. Therefore, the optimized Y_xAI_yO film is a promising candidate as the IPD for flash memory.

Nb-doped Gd2O3 as charge-trapping layer for nonvolatile memory applications

MIS capacitors with a high-κ HfLaON or HfLaO gate dielectric are fabricated by using a reactive sputtering method to investigate the applicability of the films as a novel charge-storage layer in a metal-oxide-nitride-oxide-silicon nonvolatile memory device. Experimental results indicate that the MIS capacitor with a HfLaON gate dielectric exhibits a large memory window, high program/erase speed, excellent endurance property, and reasonable retention. The involved mechanisms for these promising characteristics with HfLaON are thought to be in part from nitrogen incorporation leading to higher density of traps with deeper levels and, thus, higher trapping efficiency, stronger Hf-N and La-N bonds, and more stable atomic structure and HfLaON-SiO2 interface, as compared to the HfLaO dielectric.