Reflectometer-based metrology for high-aspect ratio via measurement

Area of Science:

• Materials Science
• Semiconductor Manufacturing
• Optical Metrology

Background:

• Accurate metrology is crucial for advanced semiconductor manufacturing, especially for 3D interconnects.
• Through-silicon vias (TSVs) are critical components in 3D integrated circuits, requiring precise dimensional control.
• Existing metrology methods for TSVs face limitations in accuracy and non-destructive capabilities.

Purpose of the Study:

• To develop an enhanced spectral reflectometry method for non-destructive TSV inspection.
• To improve the accuracy of measuring TSV profile diameters and aspect ratios.
• To enable precise characterization of via bottom profiles.

Main Methods:

• Modification of a thin film model to adjust illuminated surface area ratios for reflectivity calculations.
• Integration of a half oblate spheroid model with a reflectance modulation algorithm.
• Implementation of a novel theoretical model and measurement algorithm within a spectral reflectometer.
• Application of the developed metrology to actual 3D interconnect processing wafers.

Main Results:

• Accurate reflectivity calculations for deep via structures.
• Successful extraction of via bottom profiles from measured reflectance spectra.
• Non-destructive measurement of TSV profile diameters down to 5 micrometers.
• Measurement of TSVs with aspect ratios exceeding 13:1.
• Achieved measurement precision within 0.02 micrometers.

Conclusions:

• The enhanced spectral reflectometry method provides a powerful non-destructive solution for TSV inspection.
• The developed model and algorithm enable precise measurement of critical TSV dimensions.
• This technique is suitable for quality control in advanced 3D interconnect processing.