Formation and characterization of holmium oxide on germanium-based metal-oxide-semiconductor capacitor

• Main Authors: Onik, Tahsin Ahmed Mozaffor, Hawari, Huzein Fahmi, Sabri, Mohd Faizul Mohd, Wong, Yew Hoong
• Format: Article
• Published: John Wiley & Sons 2021
• Subjects: TJ Mechanical engineering and machinery
• Online Access: http://eprints.um.edu.my/26476/
• Institution: Universiti Malaya

The influence of different thermal oxidation/nitridation durations (5, 10, 15, and 20 minutes) at 400 degrees C for transforming metallic Ho sputtered on Ge substrate in N2O gas ambient have been systemically investigated to develop Ho2O3/Ge based on metal-oxide-semiconductor (MOS) device. The structural and chemical properties of the film were characterized using X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy. Cubic-Ho2O3 dielectric layer has been formed along with sandwiched interfacial layer (IL) between substrate Ge and high-k interface comprising tetragonal-GeO2, GeOx, and cubic-Ge3N4 compounds. Energy band alignment for Ho2O3/IL/Ge MOS stack has been determined from XPS spectrum where 10-minute sample exhibited maximum conduction band offset, Delta E-c similar to 2.47 eV and valance band offset, Delta E-v similar to 4.67 eV, inducing lower leakage current density, J similar to 10(-5) A cm(-2) at the higher electrical breakdown, E-BD similar to 8.59 MV cm(-1). The electrical results of this sample also revealed higher dielectric constant k similar to 13.60, lowest effective oxide charge, slow trap density, and interface trap density which has been attributed to the confinement of Ho2O3 dielectric interface and densification Ge3N4 interfacial compound. An oxidation/nitridation model related to Ho2O3/IL/Ge stack growth is being proposed. It has been anticipated that Ho2O3 could serve as a gate dielectric oxide for Ge-based MOS systems such as a capacitor.