White-light ellipsometer with geometric phase shifter

Area of Science:

• Optical Physics
• Materials Science
• Spectroscopy

Background:

• Spectroscopic ellipsometry is a powerful non-destructive technique for thin film characterization.
• Traditional ellipsometers can be complex and expensive.
• Accurate measurement of thin film properties is crucial in semiconductor manufacturing and optical coatings.

Purpose of the Study:

• To present a simplified spectroscopic ellipsometer design.
• To demonstrate accurate thin film thickness measurements using the new instrument.
• To address and mitigate errors associated with non-ideal optical components.

Main Methods:

• Development of a spectroscopic ellipsometer employing a geometric phase shifter and a white-light source.
• Simultaneous acquisition of phase-stepped intensities across a wavelength range (450-850 nm).
• Calculation of ellipsometric angles (ψ and Δ) from recorded intensities.
• Optimization of incident light azimuth to minimize errors from the achromatic quarter-wave plate.

Main Results:

• The developed ellipsometer successfully measures phase-stepped intensities and calculates ψ and Δ simultaneously.
• Errors in Δ were minimized by adjusting the incident light azimuth.
• Accurate film thicknesses for two silicon dioxide (SiO2) films (1000.6±0.1 Å and 20.6±0.1 Å) were obtained.
• Results showed excellent agreement with measurements from a commercial ellipsometer.

Conclusions:

• The described spectroscopic ellipsometer offers a simple yet effective method for thin film analysis.
• The instrument provides high accuracy comparable to commercial systems.
• This simplified design has potential for broader application in optical metrology and materials characterization.