Spectral Ellipsometry

SPECTRAL ELLIPSOMETRY SERVICES

Spectral ellipsometry (also known as spectroscopic ellipsometry or simply ellipsometry) measures characteristics of transparent, thin-metal, and semi-opaque films (as well as stacks) such as thickness, refractive index, extinction coefficient and others. Generalized ellipsometry is essential for developing thin film stacks without fabricating cumbersome test structures. In general, Spectral ellipsometry is a complex technique that yields rich data when combined with powerful modeling techniques — a capability Covalent offers through several experts on staff in our ellipsometry lab.

APPLICATION AREAS FOR SPECTRAL ELLIPSOMETRY:

Companies in optics (laser, coatings, electrochromic and photochromic coatings), displays, anti-reflective and high-reflection coatings, semiconductors, and photosensitive materials are common users of Spectral Ellipsometry services.

MEASUREMENTS TAKEN USING SPECTRAL ELLIPSOMETRY:

  • From the raw collected data, advanced modeling allows to extract optical index (n,k) and film thickness
  • Generalized Ellipsometry (Anisotropy, Retardance, Birefringence)
  • Optical constants: refractive index (n), extinction coefficient (k), and reflectance (R) and transmittance (T) intensity
  • Film thickness 1nm-1um (~Å accuracy)
  • Electron mobility and density along the cross section
  • Band gap
  • The instrument itself measures the change in amplitude ( tan(psi) ) and the change in phase (delta) for polarized light after reflection or transmission on the sample (reflection or transmission ellipsometry). The measurement is performed for a range of wavelengths.

USES & LIMITATIONS OF SPECTRAL ELLIPSOMETRY:

  • What it is great for:
    • instrument of choice for thin film thickness and materials optical indices measurements
    • Data collected allows advanced optical modeling (optical indices gradients, stacks) and reverse engineering

EXAMPLE OUTPUTS FROM SPECTRAL ELLIPSOMETRY

SiO2 wafer Spectroscopic ellipsometry raw data

INSTRUMENTS USED FOR SPECTRAL ELLIPSOMETRY

JA Woollam Vase

JA Woollam M2000 DI: 193nm to 1690nm, 700 wavelengths