Wafer alignment measurement in lithography systems based on vortex beam interference

Area of Science:

• Optics and Photonics
• Semiconductor Manufacturing Technology
• Metrology

Background:

• Overlay accuracy is crucial for integrated circuit manufacturing.
• High-performance wafer alignment is essential for achieving overlay accuracy.
• Existing phase grating alignment methods meet requirements for advanced lithography but alternatives are sought.

Purpose of the Study:

• To propose and validate an alternative optical measurement scheme for high-precision wafer alignment.
• To develop a rapid and high-precision wafer alignment technique.
• To explore the potential of vortex beam interferometry for lithography applications.

Main Methods:

• Utilizing vortex beam interferometry to convert grating diffraction orders into vortex beams.
• Employing a displacement-to-angle conversion mechanism based on interference pattern rotation.
• Establishing a theoretical model and conducting experimental validation.

Main Results:

• Demonstrated a linear relationship between lateral displacement and interference pattern rotation (R² > 0.999 over 1 μm).
• Achieved measurement repeatability better than 1.8 nm.
• Validated the performance of the vortex beam interferometry scheme under laboratory conditions.

Conclusions:

• Vortex beam interferometry offers a precise solution for real-time position sensing in wafer alignment.
• The proposed method has significant potential for enhancing overlay accuracy in DUV and EUV lithography.
• This technique provides a viable alternative to existing phase grating alignment systems.