Analytic Design of Segmented Phase Grating for Optical Sensing in High-Precision Alignment System.

Area of Science:

• Optics and Photonics
• Metrology and Measurement Science
• Semiconductor Manufacturing Technology

Background:

• Ultra-precision measurement systems are crucial for semiconductor manufacturing.
• Phase grating sensing alignment (PGA) systems rely on diffraction signal intensity and signal-to-noise ratio (SNR).
• Existing equally segmented gratings can increase stray light by strengthening zeroth and even diffraction orders.

Purpose of the Study:

• To address the challenge of uneven diffraction order responses in phase grating structures.
• To develop a method for optimizing grating structures to enhance desired diffraction orders while minimizing unwanted ones.
• To improve the accuracy and efficiency of phase grating sensing alignment systems.

Main Methods:

• Established an analytical relationship between diffraction efficiency and phase grating segment structure.
• Proposed a design methodology based on the analytic model to control diffraction orders.
• Verified the proposed design method using rigorous coupled-wave analysis (RCWA) numerical simulations.

Main Results:

• Successfully increased diffraction signal intensity at high odd orders.
• Significantly decreased signal intensity at the zeroth and even orders, reducing stray light.
• Demonstrated a fast and effective method for achieving globally optimal grating structures within valid scopes.

Conclusions:

• The proposed analytical model provides valuable insights into the diffraction theory of segmented gratings.
• The design method offers practical improvements for phase grating structures used in precision measurement.
• Enhanced grating designs can substantially improve the efficiency and performance of semiconductor manufacturing processes.