Research on the modulation aberration numerical correction method of interference signals for high aspect ratio...

Area of Science:

• Optical Metrology
• Nanotechnology
• Surface Science

Background:

• Coherence scanning interferometry (CSI) is a non-destructive technique for surface topography measurement.
• Traditional CSI struggles with high aspect ratio (HAR) samples due to sidewall blockage, preventing bottom topography retrieval.
• Existing CSI modifications for HAR samples often increase system complexity and cost.

Purpose of the Study:

• To propose a numerical method for correcting sample-induced aberrations in CSI for HAR samples.
• To enhance the signal-to-noise ratio and reduce interference fringe widening in CSI measurements.
• To enable accurate microstructure topography construction without optical system modification.

Main Methods:

• A numerical correction method for interference signals affected by aberrations was developed.
• Aberration-modulated point spread function (PSF) was calculated using a rigorous numerical electromagnetic field solution and the angular spectrum method (ASM).
• Initial HAR trench dimensions were extracted from experimental data to match the calculated 3D-PSF for aberration correction.

Main Results:

• The proposed method successfully corrects for sample-induced aberrations in CSI for HAR samples.
• Accurate microstructure topography of HAR trenches was reconstructed using the corrected interference signals.
• Experimental validation on HAR trench samples (100-300 µm depth, 10-30 µm width) demonstrated the method's effectiveness.

Conclusions:

• The numerical correction method offers a cost-effective and less complex solution for aberration issues in CSI for HAR samples.
• This approach significantly improves the accuracy and reliability of surface topography measurements for challenging microstructures.
• The validated method has potential for advanced applications in microfabrication and semiconductor inspection.