Structural Design and Analysis of a Quasi-Abbé-Error Free Three-Axis Wafer Measuring Platform

This study proposes a new structural design and analysis of a metrology reference module for a quasi-Abbé-error-free three-axis measurement platform used in 12-inch wafer inspection, with travel ranges of 300 mm ( X / Y ) and 5 mm ( Z ). Based on a prior platform architecture with zero Abbé error in all three axes, this study focuses on optimizing the metrology reference module by integrating three-axis reference mirrors into a monolithic structure. This integration eliminates assembly errors, simplifies construction, and enhances structural performance. Finite element analysis (FEA) was used to optimize stiffness-to-weight ratio and minimize deformation under static loads, which improved interferometric measurement accuracy and reduced errors caused by the effect of structural deformation on the wafer. A prototype was built based on the FEA results and validated through experimental modal testing. The results show a 96.4% decrease in static deformation (from 15.62 µm to 564 nm) and a 45.67% increase in the first natural frequency, indicating significant improvements in both static and dynamic rigidity. The results of the modal testing further validated the strong correlation between experimental measurements and simulation, indicating that the established model accurately captures the dynamic characteristics of the structure. This confirms the high accuracy and reliability of the FEA model for structural performance prediction.