Deposition and characterization of MgO/Si gate stacks grown by molecular beam epitaxy

• Published in: Thin solid films Vol. 520; no. 14; pp. 4508 - 4511
• Main Authors: Su, Chen-Yi, Frederickx, Michiel, Menghini, Mariela, Dillemans, Leander, Lieten, Ruben, Smets, Tomas, Seo, Jin Won, Locquet, Jean-Pierre
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2012; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Defects and impurities: doping, implantation, distribution, concentration, etc; Exact sciences and technology; Gate stack; High K dielectric; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Molecular, atomic, ion, and chemical beam epitaxy; Oxide thin films; Physics; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Oxide thin films; Gate stack; High K dielectric; High-pressure effects; Amorphous thin film; Pressure effects; High density; CV characteristic; Thin films; Energy gap; Gallium tellurides; Molecular beam epitaxy; Silicon; Permittivity; Current density; Defect density; Annealing; Vacancies; Magnesium oxide; Layer thickness; High pressure; Interfaces; Silicon oxides; Magnesium silicate; Capacitance; High k dielectric; Gates
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2011.10.133

In this article, the deposition and characterization of amorphous MgO films grown on Si (001) using molecular beam epitaxy is reported. In order to ensure amorphous films, low substrate temperatures (200°C) and high oxygen pressures were used (up to 5×10−3Pa). Both atomic and molecular oxygen species were used at different pressures. Films ranging in thickness from 3nm till 30nm were grown and characterized using structural and electrical methods. The dielectric constant deduced from this thickness series corresponds to 8.74 close to the bulk value of 9.8. The best equivalent oxide thickness value observed for this series – grown under high oxygen pressure – corresponds to 1.2 nm for a current density measured at VFB−1V of 0.1A/cm2. The films grown with atomic oxygen display a lower capacitance and lower leakage compared to the films grown using molecular oxygen. This is due to the appearance of a thin SiO2 interface layer which is also responsible for the high defect density observed in the capacitance–voltage measurements. Upon annealing both types of films in forming gas for 15min at 450°C, the capacitance decreases further while the leakage increases. This change is assigned to the appearance of the lower bandgap (6.6eV), lower dielectric constant (6.6) phase of silicate, MgSiO3. Furthermore a VFB shift of −0.6V is observed and is related to the appearance of oxygen vacancies as Mg diffuses into the SiO2 interface layer.