Enhancement of electrical performance of Ge-based metal-oxide-semiconductor capacitor via formation of trigonal-Sm2O3

• Main Authors: Onik, Tahsin Ahmed Mozaffor, Hawari, Huzein Fahmi, Mohd Faizul, Mohd Sabri, Wong, Yew Hoong
• Format: Article
• Published: 2021
• Subjects: QC Physics; QD Chemistry
• Online Access: http://eprints.um.edu.my/26290/; https://doi.org/10.1016/j.surfin.2021.101289

In this study, Sm2O3/Ge stack based capacitor prepared from thermally oxidized/nitrided sputtered metallic Sm on Ge semiconductor in N2O ambient for several oxidation/nitridation durations, i.e., 5 - 20 min have been comprehensively investigated. The film crystallinity, chemical composition and interface chemical bonding states stability was characterized from X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Formation of trigonal-Sm2O3 dielectric interface together with an interfacial layer containing asymmetrically distributed (Ge-O, Sm-O-Ge and Ge-N) species has been verified. Suppression of GeO (g) volatilization was evident from the XPS analysis due to germanate (Sm-O-Ge) formation. Structural morphology characterization using high resolution transmission electron microscope (HRTEM) also validated double stack amorphous interfaces obtaining physical oxide thickness (t(ox)) from 4.25-6.91 nm. Band alignment and electrical measurements revealed that oxidation/nitridation duration of 15 min exhibited highest conduction band offset (CBO), Delta E-c of 2.60 eV and valence band offset (VBO) Delta E-v of 2.98 eV leading to lowest leakage current density J(g) similar to 8.38 x 10(-6) A cm(-2) at enhanced breakdown field, EBD of 13.31 MV cm(-1). The large breakdown field has been ascribed to fewest effective oxide charge (Q(eff)), slow trap density, (Q(it)) and interface traps density D-it at this duration. Additionally, a low equivalent oxide thickness, t(EOT) similar to 0.75 nm with a high dielectric constant k similar to 31.19 eV was achieved but with a price of high D-it similar to 10(13) eV(-1)cm(-2). These properties render that Sm2O3 could serve as dielectric material for future high-k/Ge stack based metal oxide semiconductor technology, although requires further investigation for D-it improvement.