Three-dimensional imaging of undercut and sidewall structures by atomic force microscopy.

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Sidewall surface roughness is critical for electronic device performance.
• Existing high-resolution techniques cannot quantitatively assess undercut structures.

Purpose of the Study:

• To develop a novel method for high-resolution, quantitative characterization of sidewall surface roughness in undercut structures.
• To demonstrate the capability of the developed technique on various semiconductor components.

Main Methods:

• Development of a three-dimensional atomic force microscope (3D-AFM) with a probe capable of variable tilt (up to 40°).
• Utilizing nonorthogonal scanning to resolve surface topography, base width, and critical angles of undercut features.
• Testing the 3D-AFM on structures like metal overhangs and photonic device transmission lines.

Main Results:

• The 3D-AFM achieves nanometer precision in measuring sidewall surface roughness.
• The technique successfully characterized undercut structures, including their base width and critical angles.
• Demonstrated compatibility with standard cantilevers and potential for soft materials like photoresist.

Conclusions:

• The developed 3D-AFM is a breakthrough for quantitative analysis of sidewall surface roughness in semiconductor manufacturing.
• This technique provides essential data for optimizing electronic device fabrication and understanding material properties.
• The 3D-AFM shows significant promise for characterizing challenging geometries and soft materials.