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Photoresists
Measure film thickness and refractive index (n, and k) at 157nm, 193nm, 248nm.

Stepper Optics
Optical elements involved in lithography exposure tools can be enhanced with proper optical coatings. The coating merit will depend on refractive index and thickness. Fluorinated materials are candidates at 157nm, as they remain transparent into the VUV. The graph shows the index for various fluorides measured with VUV ellipsometry.

Birefringence
Ellipsometry can measure the orientation and retardance of birefringent materials. Measured retardance of a 20mm thick CaF optic is shown. Powerful software makes this measurement easy to perform.

Antireflective Coatings
Resists are used in conjunction with antireflective coatings to suppress reflections from the underlying substrate. Bottom AR coatings absorb light penetrating the photoresist and minimizes reflection back into the resist layer. The AR coating refractive index should match the photoresist to suppress reflections from the resist/AR interface. Convenient materials can 'tune' refractive index for this application.
AR performance depends strongly on index and thickness. Ellipsometers measure both values and are able to track changes with different process conditions (Figure shows SiO N with various x).

Reflection/Transmission
Transmission measurements are often important for increasing sensitivity to small values. The VUV-VASE uses a vertical sample mount allowing easy transmission measurements at any angle. Reflection measurements are acquired at any angle from 10° to 90°.

Anisotropy
Advanced anisotropic measurements (generalized SE) provide additional information to help fully characterize uniaxial (2 sets of optical constants) and biaxial (3 sets of optical constants) anisotropic materials.
The VUV-VASE can measure in both reflection and transmission ellipsometry modes. The graphs show ordinary and extraordinary dielectric functions of 4H SiC measured with VUV-VASE.

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