Investigation and Application of Key Alignment Parameters for Overlay Accuracy in 3D Structures.

Area of Science:

• Semiconductor manufacturing
• Advanced metrology
• 3D integrated circuits

Background:

• 3D stacked memory adoption necessitates precise alignment and overlay control for multi-layer accuracy.
• Metrology accuracy and stability of alignment marks are vital for optimal alignment and overlay performance.

Purpose of the Study:

• To systematically investigate the contributions of Wafer Quality (WQ) and Alignment Position Deviation (APD) to alignment model residue in 3D structures.
• To analyze the interplay between WQ, APD, and overlay performance using experimental and simulation methods.

Main Methods:

• Experimental analysis of alignment parameters.
• Simulation of alignment processes in 3D structures.
• Correlation analysis between WQ, APD, and overlay performance metrics.

Main Results:

• APD shows a stronger correlation with uncorrectable alignment model residue, particularly under global process variations like etch non-uniformity.
• APD sensitivity varies directionally (X/Y marks) and spatially (wafer edge vs. center).

Conclusions:

• APD is a critical factor influencing overlay accuracy in 3D stacked memory.
• Targeted alignment mark designs are needed for process-sensitive zones to mitigate APD effects.
• Findings offer insights for optimizing alignment strategies and process monitoring in semiconductor manufacturing.