Fluorination of Aluminum Oxide Gate Dielectrics Using Fluorine Neutral/Ion Beams

Abstract

The effect of the fluorination of aluminum oxide (Al2O3) in an oxide-nitride-aluminum oxide (SiO2-Si3N4-Al2O3, ONA) layer through fluorine (F) ion and neutral-beam treatments on the characteristics of the ONA layer was investigated to study the effect of charge-related damage during F ion beam treatment. The treatment with an F beam at approximately 10 eV energy produced an about-5-nm-thick fluorinated alumina layer by replacing the aluminum-oxygn (Al-O) bonding with Al-F bonding for both the F neutral-beam and F ion beam treatments. Moreover, no significant differences in the physical and chemical properties of the ONA layers treated with the two beams were observed. When the electrical characteristics of the metal-oxide-semiconductor (MOS) devices were compared, however, the lowest leakage current and highest memory window characteristics were observed in the MOS device fabricated with an F neutral beam, due to the Al-F layer formed on the Al2O3 surface. In the case of the MOS device fabricated with the F-ion-beam-treated ONA layer, however, lower electrical characteristics were observed compared to the MOS device fabricated with the F-neutral-beam-treated ONA layer, possibly due to the charge-related damage that occurred during the F ion beam treatment, even though the memory characteristics were improved compared to the reference due to the Al-F layer formed on the Al2O3 surface.

Thermal Atomic Layer Etching of Aluminum Oxide (Al2O3) Using Sequential Exposures of Niobium Pentafluoride (NbF5) and Carbon Tetrachloride (CCl4): A Combined Experimental and Density Functional Theory Study of the Etch Mechanism

“…According to Morelock et al, aluminum trifluoride adopts a cubic form above 440 °C, which upon cooling changes to a rhombohedral phase. The X-ray diffraction (XRD) analysis of about 11 nm AlF X [O] layer revealed the rhombohedral phase (see the Supporting Information S4) and is thus consistent with the literature. − On the contrary, at 400 °C, the thickness of the fluorinated layer stayed around 3 nm even after prolonged total NbF 5 exposure of 2700 s. Chen et al showed the fluoride ions penetrating up to 2 nm thick aluminum oxide after treating fluorinated alumina at 400 °C, and neutral/ion beams-assisted fluorination lead to a thicker AlF X [O] layer . Moreover, up to 0.5 nm thick AlF 3 layer was obtained at a lower temperature of 300 °C with HF as a fluorinating agent .…”

“…40−44 On the contrary, at 400 °C, the thickness of the fluorinated layer stayed around 3 nm even after prolonged total NbF 5 exposure of 2700 s. Chen et al showed the fluoride ions penetrating up to 2 nm thick aluminum oxide after treating fluorinated alumina at 400 °C, 45 and neutral/ion beams-assisted fluorination lead to a thicker AlF X [O] layer. 46 Moreover, up to 0.5 nm thick AlF 3 layer was obtained at a lower temperature of 300 °C with HF as a fluorinating agent. 38 This temperature-dependent thickness of the converted fluorinated layer suggests that the conversion step is diffusion-limited.…”

Fluorination of Al2O3 blocking layer for improving the performance of metal‐oxide‐nitride‐oxide‐silicon flash memory

“…To obtain ideal tunnel layer with SiO 2 /HfO 2 / SiO 2 dielectric stack, fluorine incorporation by fluorine ion implantation at different stages of processing has been fully researched [10]. Recently, fluorination of Al 2 O 3 blocking layer for silicon-oxide-nitride-silicon devices has been investigated by treating Al 2 O 3 with a low-energy fluorine (neutral or ion) beam [11,12]. The study showed that the Al 2 O 3 blocking layer was composed of two layers (AlO x F y and Al 2 O 3 ), and the fluorination of Al 2 O 3 produced lower leakage current and significantly larger C-V hysteresis window, possibly due to defect passivation by fluorine incorporation [11,12].…”

“…Recently, fluorination of Al 2 O 3 blocking layer for silicon-oxide-nitride-silicon devices has been investigated by treating Al 2 O 3 with a low-energy fluorine (neutral or ion) beam [11,12]. The study showed that the Al 2 O 3 blocking layer was composed of two layers (AlO x F y and Al 2 O 3 ), and the fluorination of Al 2 O 3 produced lower leakage current and significantly larger C-V hysteresis window, possibly due to defect passivation by fluorine incorporation [11,12]. It is also demonstrated that plasma process can incorporate F in the ALD-grown Al 2 O 3 film more efficiently than the conventional implantation The characteristics of Al 2 O 3 film grown by atomic-layer deposition as blocking layer with and without fluorine plasma treatment were investigated based on a capacitor structure of Al/Al 2 O 3 /TaON/SiO 2 /Si.…”