Formation and characterization of rare earth oxides as high-K gate dielectrics on germanium substrate / Tahsin Ahmed Mozaffor Onik

Tahsin Ahmed , Mozaffor Onik (2022) Formation and characterization of rare earth oxides as high-K gate dielectrics on germanium substrate / Tahsin Ahmed Mozaffor Onik. PhD thesis, Universiti Malaya.

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Abstract

In this study, Sm2O3/Ge and Ho2O3/Ge stack based metal oxide semiconductor (MOS) capacitors were prepared from radio frequency (RF) sputtered metallic Sm on Ge sub-strate and metallic Ho on Ge substrate followed by thermal oxidation/nitridation in N2O ambient. The effects of several oxidation/nitridation temperatures, i.e., 300 °C – 600 °C on the sputtered Sm/Ge and influence of various oxidation/nitridation durations, i.e., 5 – 20 min on both sputtered Sm/Ge and Ho/Ge system have been comprehensively investi-gated. The film crystallinity and phase identification, chemical composition, interface chemical bonding states stability and structural morphology were characterized from X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High-resolution transmission electron microscopy (HRTEM). Formation of stoichi-ometric trigonal-Sm2O3 dielectric interface has been verified for thermally oxidized/ni-trided sputtered Sm/Ge system. In contrary, sub-stoichiometric cubic-Ho2O3 has been identified for thermally oxidized/nitrided sputtered Ho/Ge system. Both the stacking structure produced sandwiched interfacial layer containing asymmetrically distributed Ge−O, and Ge−N contents while oxidized/nitrided Sm/Ge stack produced an additional stable interfacial germanate (Sm−O−Ge). Suppression of GeO (g) volatilization was ev-ident from the XPS analysis due to GeO (g) trapping mechanism instigated by interfacial germanate (Sm−O−Ge) formation for oxidized/nitrided Sm/Ge while IL rich with Ge3N4 contributed to inhibit the volatilization of GeO (g) for oxidized/nitrided Ho/Ge system. The HRTEM analysis also validated double stack amorphous interfaces obtaining physi-cal oxide thickness,

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