Adaptive modal decomposition based overlapping-peaks extraction for thickness measurement in chromatic confocal...

Area of Science:

• Optical Metrology
• Thin Film Analysis

Background:

• Accurate thickness measurement of ultra-thin transparent films is crucial.
• Existing spectral axial response signal (sARS) fitting algorithms struggle with overlapping peaks, leading to errors.

Purpose of the Study:

• To develop an improved method for extracting multiple overlapping peaks from sARS for ultra-thin materials.
• To enhance the accuracy and precision of chromatic confocal thickness measurements.

Main Methods:

• Proposed an adaptive modal decomposition method to decompose sARS into sub-modes.
• Applied single peak extraction algorithms (e.g., centroid, Gauss fitting) to decomposed sub-modes.
• Validated the method using Monte Carlo simulations and experimental tests.

Main Results:

• The adaptive modal decomposition method effectively separates overlapping peaks.
• Demonstrated significant improvements in peak extraction accuracy compared to existing nonlinear fitting algorithms.
• Achieved enhanced precision in determining peak wavelengths for ultra-thin films.

Conclusions:

• The proposed adaptive modal decomposition method offers a robust solution for multi-peak extraction in sARS.
• This technique enhances the reliability of chromatic confocal thickness measurements for ultra-thin transparent films.