Metrology of optically-unresolved features using interferometric surface profiling and RCWA modeling.

Area of Science:

• Nanotechnology
• Optical Metrology
• Surface Science

Background:

• Characterizing sub-wavelength surface features is crucial for microelectronics and nanotechnology.
• Traditional microscopy methods often lack the resolution to accurately measure optically-unresolved dimensions.

Purpose of the Study:

• To demonstrate the capability of Rigorous Coupled Wave Analysis (RCWA) in interpreting 3D white-light interference microscopy profiles.
• To reveal the dimensions of optically-unresolved surface features with high accuracy and repeatability.

Main Methods:

• Utilized Rigorous Coupled Wave Analysis (RCWA) to process 3D white-light interference microscopy data.
• Measured silicon etch depth and lateral widths of grating structures with varying pitches.

Main Results:

• RCWA-interpreted measurements of silicon etch depth for a 450-nm pitch grating showed excellent correlation (R²=0.995) with Atomic Force Microscopy.
• Achieved a repeatability of 0.11 nm for etch depth measurements.
• Demonstrated sub-nanometer sensitivity (<1 nm) to 80-nm lateral widths on 190-nm pitch gratings.

Conclusions:

• RCWA is a powerful tool for quantitative analysis of 3D microscopy data, enabling precise measurement of nanoscale surface features.
• The technique offers high accuracy and repeatability, suitable for critical dimension metrology in semiconductor manufacturing and nanotechnology.