Progress in spectroscopic ellipsometry: Applications from vacuum ultraviolet to infrared

Abstract

Spectroscopic ellipsometry ͑SE͒ is a noncontact and nondestructive optical technique for thin film characterization. In the past 10 yr, it has migrated from the research laboratory into the semiconductor, data storage, display, communication, and optical coating industries. The wide acceptance of SE is a result of its flexibility to measure most material types: dielectrics, semiconductors, metals, superconductors, polymers, biological coatings, and even multilayers of these materials. Measurement of anisotropic materials has also made huge strides in recent years. Traditional SE measurements cover the ultraviolet, visible, and near infrared wavelengths. This spectral range is now acquired within seconds with high accuracy due to innovative optical configurations and charge coupled device detection. In addition, commercial SE has expanded into both the vacuum ultraviolet ͑VUV͒ and midinfrared ͑IR͒. This wide spectral coverage was achieved by utilizing new optical elements and detection systems, along with UV or Fourier transform IR light sources. Modern instrumentation is now available with unprecedented flexibility promoting a new range of possible applications. For example, the VUV spectral region is capable of characterizing lithographic materials for 157 nm photolithography. The VUV also provides increased sensitivity for thin layers ͑e.g., gate oxides or self-assembled monolayers͒ and allows investigation of high-energy electronic transitions. The infrared spectral region contains information about semiconductor doping concentration, phonon absorption, and molecular bond vibrational absorptions. In this work, we review the latest progress in SE wavelength coverage. Areas of significant application in both research and industrial fields will be surveyed, with emphasis on wavelength-specific information content.

Concurrent bandgap narrowing and polarization enhancement in epitaxial ferroelectric nanofilms

“…The optical properties of uncovered films and bulk crystals were probed using variable-angle spectroscopic ellipsometry (VASE), which allows for high-precision measurements of films with a thickness of only a few atomic layers and of separate macromolecules on top of arbitrary substrates [45]. Since accurate analyses of ellipsometric data for wide bandgap materials are only possible if the spectral range is sufficiently expanded into the high-energy (UV) region, an J A Woollam ellipsometer with an extended photon energy range was used.…”

Optical band gaps and composition dependence of hafnium–aluminate thin films grown by atomic layer chemical vapor deposition

“…Due to the relatively large band gaps ͑3.5-7 eV͒ of most high-k materials of technological importance, VUV-SE with a spectral range extended to Ϸ9.0 eV was found to be the most suitable technique to ascertain the optical properties near and above the fundamental band gap. [9][10][11][12][13] In this spectral range, E g can be readily determined. We show that the E g value deduced experimentally varied with the amount of the Al 2 O 3 used to grow Hf-aluminate films.…”

An Assemblable, Multi-Angle Fluorescence and Ellipsometric Microscope

“…While the spatial resolution is limited by diffraction optics, the thickness-resolution is typically sub-nm. The technique has applications in semiconductor industries [23] and biology, particularly supported lipid bilayers [24, 25]. Imaging ellipsometry is a variant of the technique which spatially resolves thin films on the surface [26].…”