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 extracting the 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

USES & LIMITATIONS OF SPECTRAL ELLIPSOMETRY:

  • What it is great for:
    • The 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

Optical Constant N Measurements on a Wafer

Thickness Measurement on a Wafer

Measurement / Property

1690-193 nm
0.73 - 6.4 ev
1700-300 NM
0.73 - 4.13 EV
Wavelength Range
Photon Energy Range
JA Woollam M-2000 JA Woollam V-Vase
Tool Image M-2000 product-img
Film(s) thickness
Determination of layer thickness for single films or multi-layer stacks can be accomplished for virtually any semiconducting and dielectric materials.
Optical properties n & k
Index of refraction (n) and the extinction or absorption coefficients (k or α) can be determined for any bulk or thin film samples that are relatively smooth. SE is particularly useful in identifying variation in n & k arising from different material fabrication or processing procedures.
Very thin metal films (~5 - 400 Å)
The thickness and optical properties of thin metal films can be unambiguously determined.
Electrical properties of buried conducting layers
SE provides a means for accessing electrical properties (resistivity, carrier concentration, mobility) of conducting layers buried beneath other semiconducting or dielectric layers where other contact-based techniques are inapplicable.
Nanoscale surface oxidation / corrosion
Being highly surface sensitive, SE is an ideal technique for identifying the presence and extent of surface oxidation, corrosion, or adsorption.
Diffusion profiles at interfaces
Measurement of the sharpness' of interfaces between two materials is accomplished through detection of interfacial diffusion profiles.

INSTRUMENTS USED FOR SPECTRAL ELLIPSOMETRY

JA Woollam Vase

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