High-speed 3D imaging using two-wavelength parallel-phase-shift interferometry

Area of Science:

• Optical Metrology
• Nanotechnology
• Semiconductor Manufacturing

Background:

• Accurate 3D surface profiling is critical for microelectronics fabrication.
• Existing high-speed imaging techniques often lack the required vertical accuracy for complex structures.

Purpose of the Study:

• To present a high-speed, high-accuracy three-dimensional (3D) imaging technique.
• To enable video-rate imaging of high step profiles with nanometer precision.

Main Methods:

• Utilized two-wavelength parallel-phase-shift interferometry.
• Employed a polarization-based Linnik interferometer with three phase-masked CCD cameras.
• Incorporated two quasi-monochromatic modulated light sources for phase unwrapping.

Main Results:

• Successfully imaged step profiles up to 3.7 μm with ±2 nm accuracy and repeatability.
• Demonstrated video-rate imaging capabilities.
• Validated the technique on a certified very large scale integration (VLSI) step standard and semiconductor integrated chips with copper micro pillars.

Conclusions:

• The developed two-wavelength interferometry technique offers high-speed and high-accuracy 3D imaging.
• This method is suitable for critical dimension metrology in semiconductor manufacturing.
• The technique provides a robust solution for profiling complex microelectronic structures.