Nanometer resolution optical coherence tomography using broad bandwidth XUV and soft x-ray radiation

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Optical coherence tomography (OCT) offers non-invasive cross-sectional imaging, valuable for deep or fast-moving samples.
• Conventional OCT, using infrared and optical wavelengths, has an axial resolution limited to approximately 1 micrometer.
• Existing limitations hinder detailed imaging of nanometer-scale structures.

Purpose of the Study:

• Introduce extreme ultraviolet coherence tomography (XCT) as a novel non-invasive imaging technique.
• Demonstrate XCT's capability for imaging nanometer structures with enhanced axial resolution.
• Explore XCT's potential for semiconductor metrology and water window imaging.

Main Methods:

• Utilized extreme ultraviolet (EUV) light sources with nanometer-scale coherence lengths.
• Exploited spectral transmission windows of materials like silicon.
• Performed tomographic imaging of buried nanostructures and nanometer-scale layers.

Main Results:

• Achieved axial resolution in coherence tomography improved from micrometers to a few nanometers.
• Demonstrated tomographic imaging of buried nanostructures with axial resolution better than 18 nm.
• Resolved nanometer-scale platinum layers with resolution better than 8 nm using water window wavelengths.

Conclusions:

• XCT significantly enhances axial resolution for non-invasive cross-sectional imaging.
• XCT provides nanometer-scale precision for subsurface imaging of nanostructures.
• XCT shows strong potential for advanced semiconductor metrology and specialized imaging applications.