Three-dimensional imaging of copper pillars using x-ray tomography within a scanning electron microscope: a...

Area of Science:

• Materials Science
• Microscopy
• Nanotechnology

Background:

• Surface-sensitive techniques lack penetration depth for 3D microelectronic interconnections.
• 3D integration demands high-resolution, deep-penetrating imaging methods.
• X-ray tomography offers a suitable solution for characterizing complex 3D structures.

Purpose of the Study:

• To assess a versatile, turn-key 3D X-ray nanotomography system.
• To enable high-resolution 3D imaging of copper pillars for 3D integration.
• To quantify intermetallic volumes within copper pillars.

Main Methods:

• Utilized a scanning electron microscope (SEM) with a thin electron beam for X-ray generation.
• Employed cone beam tomography with sample rotation to acquire radiographs.
• Developed a 3D numerical model of a copper pillar, including intermetallics, for simulation.
• Reconstructed 3D data from simulated and experimental radiographs.

Main Results:

• Successfully reconstructed 3D images of copper pillars.
• Demonstrated the system's capability to quantify 3D intermetallic volumes.
• Validated the 3D numerical model against experimental data.

Conclusions:

• The developed 3D X-ray nanotomography system is effective for characterizing copper pillars.
• The system allows for accurate quantification of intermetallic phases in 3D.
• Further discussion on resolution limitations and future improvements is provided.