Optical constants of germanium and thermally grown germanium dioxide from 0.5 to 6.6eV via a multisample ellipsometry investigation
Abstract
Thermal GeO2 oxides up to 136 nm thickness were produced by annealing Ge wafers in pure oxygen at 550 °C and 270 kPa pressure for up to 10 h. The oxidation kinetics followed the Deal–Grove law. Using multisample spectroscopic ellipsometry for a series of five thermal oxides with different thicknesses, the complex dielectric functions of Ge and GeO2 were determined from 0.5 to 6.6 eV, for thin-film metrology applications in Ge-based microelectronics and photonics. The dispersion of the GeO2 layer was modeled with a simple Tauc-Lorentz oscillator model, but a more complicated dispersion with eight parametric oscillators was required for Ge. A reasonable fit to the ellipsometric angles could be obtained by assuming that all thermal oxides can be described by the same dielectric function, regardless of thickness, but a slight improvement was achieved by allowing for a lower density oxide near the surface of the thickest films. The authors compare their results with literature data for Ge and bulk and thin-film GeO2.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 30, 2016
- Source ID
- 10.1116/1.4963075
Entities
People
- Amber A. Medina
- Cayla M. Nelson
- Jaime M. Moya
- Nalin S. Fernando
- Nuwanjula S. Samarasingha
- Stefan Zollner
- T. Nathan Nunley
Organizations
- Air Force Office of Scientific Research
- Army Research Office
- National Science Foundation
- New Mexico State University