Dipole Formation and Electrical Properties According to SiO₂ Layer Thickness at an Al₂O₃/SiO₂ Interface
2021
Kim, Ryun Na | Yun, Hye Won | Lee, Jinho | Kim, Woo-Byoung
Interfacial and electrical properties of Al₂O₃/SiO₂/Si were analyzed to determine the change in interfacial defects and suboxide density according to the thickness of the SiO₂ layer and to determine the effect on dipole and flat-band voltage. As the thickness of the SiO₂ layer increased (5/7/10 nm), the density of the suboxide present at the interface (2.23/3.23/4.73 × 10¹⁴ atoms/cm²) also increased, respectively. In addition, the slow state density, fixed oxide charge density, and interface state density calculated through the capacitance–voltage (C–V) curve all differ depending on the thickness of the SiO₂ layer and are further reduced by postmetallization annealing (PMA). The flat-band voltages (VFB) of the SiO₂/Si sample with thicknesses of 5, 7, and 10 nm before PMA are −1.27, −1.32, and −2.20 V, respectively, and further decreased after PMA (−0.64, −0.80, and −1.74 V). Consequently, it was demonstrated that there was a difference in interfacial defects and suboxides according to the thickness. In addition, it was confirmed that when the interfacial defects and suboxides were reduced, the oxide charge state density and oxygen diffusion decreased, and thus the dipole layer strength and VFB shift decreased.
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