Spectroscopic null ellipsometer using a variable retarder

Area of Science:

• Optics and Photonics
• Materials Science
• Surface Analysis

Background:

• Ellipsometry is a powerful technique for characterizing thin films.
• Traditional PCSA null ellipsometers often use fixed compensators, limiting flexibility.
• Developing adaptable ellipsometry systems is crucial for advanced material analysis.

Purpose of the Study:

• To present a modified polarizer-compensator-sample-analyzer (PCSA) null ellipsometer design.
• To demonstrate the direct determination of ellipsometric angles using a variable retarder.
• To validate the accuracy of this new system for thin film thickness measurements.

Main Methods:

• Utilized a variable retarder, specifically a Soleil-Babinet compensator with quartz plates, as the compensator in a PCSA setup.
• Maintained a fixed azimuthal angle for either the polarizer or analyzer.
• Calculated retarder delay at various wavelengths using dispersion data and a reference measurement at 632.8 nm.

Main Results:

• Successfully implemented a PCSA null ellipsometer with a variable retarder.
• Ellipsometric angles (ψ and Δ) were directly determined from the rotating component's azimuth and compensator delay.
• Accurate thickness measurements of silicon dioxide films on silicon wafers were achieved, consistent with traditional methods.

Conclusions:

• The developed variable retarder-based PCSA null ellipsometer offers a viable and accurate alternative for thin film characterization.
• This method simplifies data acquisition by directly relating angles to physical parameters.
• The system demonstrates excellent agreement with established ellipsometric techniques, highlighting its reliability.