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

Summary The influence of different thermal oxidation/nitridation durations (5, 10, 15, and 20 minutes) at 400°C for transforming metallic Ho sputtered on Ge substrate in N 2 O gas ambient have been systemically investigated to develop Ho 2 O 3 /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‐Ho 2 O 3 dielectric layer has been formed along with sandwiched interfacial layer (IL) between substrate Ge and high‐ k interface comprising tetragonal‐GeO 2 , GeO x , and cubic‐Ge 3 N 4 compounds. Energy band alignment for Ho 2 O 3 /IL/Ge MOS stack has been determined from XPS spectrum where 10‐minute sample exhibited maximum conduction band offset, Δ E c ~ 2.47 eV and valance band offset, Δ E v ~ 4.67 eV, inducing lower leakage current density, J ~ 10 −5 A cm −2 at the higher electrical breakdown, E BD ~ 8.59 MV cm −1 . The electrical results of this sample also revealed higher dielectric constant k ~ 13.60, lowest effective oxide charge, slow trap density, and interface trap density which has been attributed to the confinement of Ho 2 O 3 dielectric interface and densification Ge 3 N 4 interfacial compound. An oxidation/nitridation model related to Ho 2 O 3 /IL/Ge stack growth is being proposed. It has been anticipated that Ho 2 O 3 could serve as a gate dielectric oxide for Ge‐based MOS systems such as a capacitor.