Automatic null ellipsometry with an interferometer

Area of Science:

• Optics and Photonics
• Materials Science
• Surface Science

Background:

• Traditional null ellipsometry (polarizer compensator sample analyzer - PCSA) relies on iterative measurements.
• Accurate characterization of thin films is crucial for semiconductor and optical industries.
• Existing methods can be time-consuming and complex.

Purpose of the Study:

• To develop a new, non-iterative automatic null ellipsometry approach.
• To enhance the speed and simplicity of ellipsometric measurements.
• To validate the accuracy of the novel technique against established methods.

Main Methods:

• Replaced the analyzer in a PCSA ellipsometer with a heterodyne Michelson interferometer.
• Modified one interferometer arm to produce a stable, linearly polarized reference beam.
• Interferometrically recombined beams and spatially separated polarizations to analyze fringe phase and amplitude.

Main Results:

• The relative phase of temporal fringes directly correlated with the polarizer angle, enabling non-iterative nulling.
• The reflected light's azimuthal angle was easily determined from fringe amplitude at null.
• Measurements on silicon native oxide films showed excellent agreement with traditional PCSA ellipsometry.

Conclusions:

• The heterodyne interferometer-based approach offers a faster, iterative-free method for automatic null ellipsometry.
• This technique provides accurate thin film characterization comparable to conventional ellipsometers.
• The new method simplifies the process of determining optical properties of materials.