Wafer defect detection by a polarization-insensitive external differential interference contrast module.

Area of Science:

• Materials Science
• Optical Engineering
• Semiconductor Manufacturing

Background:

• Traditional defect detection in semiconductor wafers often relies on bright-field imaging, which can struggle with subtle defects.
• Existing differential interference contrast (DIC) techniques typically require polarization optics and are sensitive to polarization variations, limiting their application.

Purpose of the Study:

• To develop and present a new external, polarization-insensitive differential interference contrast (DIC) module for enhanced semiconductor wafer defect detection.
• To demonstrate improved defect signal enhancement compared to bright-field imaging.
• To enable direct differential phase imaging with enhanced defect detection capabilities, even for sub-resolution defects.

Main Methods:

• Development of an external shearing interferometer-based DIC module connectable to standard optical microscopes.
• The module operates without polarization optics, making it insensitive to polarization.
• Provides full control over DIC shear and orientation for direct differential phase imaging on a camera.

Main Results:

• Achieved significant defect signal enhancement relative to the surrounding wafer pattern compared to bright-field imaging.
• Demonstrated effective imaging of thin samples, including wafer defects.
• Enabled direct differential phase imaging without additional digital processing, enhancing defect detection for sizes below the resolution limit.

Conclusions:

• The new polarization-insensitive DIC module offers superior defect detection capabilities for semiconductor wafers.
• Its external, polarization-insensitive design and direct imaging output present a significant advancement over traditional DIC methods.
• The technique shows strong potential for integration into semiconductor production lines for improved quality control.