SEM Beam Position Correction for High-Speed Wafer Stage Scanning
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Solution Overview
Problem
The challenge in manufacturing integrated circuits (ICs) is to obtain accurate scanning electron microscope (SEM) images without distortion or deformation, as the physical sizes of IC components continue to shrink, requiring improved accuracy and yield in defect detection.
Innovation Solution
A method and apparatus for correcting inspection image errors by acquiring beam positions at different velocities, calculating beam position displacement, and adjusting the beam position to compensate for displacement caused by eddy currents and disturbance magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wafer stage moves at high velocity during SEM inspection, then productivity is improved, but beam position displacement occurs due to eddy currents and disturbance magnetic fields, degrading measurement precision
Solution Approach 1:
The system performs preliminary calibration by acquiring beam positions at multiple known stage velocities, calculates beam position displacements, and stores correction values before actual inspection. This preliminary action enables real-time compensation during high-speed inspection without degrading beam position accuracy
Solution Approach 2:
The system changes the velocity parameter of the wafer stage during calibration to acquire beam positions at different speeds. By measuring beam position displacement at multiple velocities and interpolating, the system determines correction values for intermediate velocities, enabling accurate compensation across a range of inspection speeds
2Measurement precision
If eddy current effects are suppressed to maintain beam position accuracy, then measurement precision is improved, but device complexity increases due to specialized wafer stage requirements
Solution Approach 1:
The system introduces an intermediary calibration and correction mechanism that mediates between the moving wafer stage and the beam positioning system. By measuring actual beam positions at known stage velocities and calculating displacement corrections, the system compensates for eddy current effects without requiring modifications to the wafer stage structure
Solution Approach 2:
The system replaces mechanical suppression of eddy currents (which would require specialized non-conductive wafer stages or complex shielding) with a computational approach. By using software-based beam position correction algorithms that compensate for measured displacements, the system eliminates the need for complex mechanical modifications to the wafer stage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively offsets eddy current effects, allowing the use of conventional wafer stages while minimizing image quality degradation, thus enhancing the accuracy and reliability of SEM images for defect detection in IC manufacturing.
Implementation Method 1
beam position displacement of a beam while the wafer stage moves at a third velocity in a range of velocities from the first velocity to the second velocity
Implementation Method 2
offsets eddy current effects, allowing the use of conventional wafer stages while minimizing image quality degradation
Data Source
AI summary
An improved method and system for correcting inspection image error are disclosed. An improved method comprises acquiring a set of first beam positions on a test wafer while a wafer stage supporting the test wafer moves at a first velocity; acquiring a set of second beam positions, corresponding to the set of first beam positions, on the test wafer while the wafer stage moves at a second velocity; calculating a beam position displacement of a beam while the wafer stage moves at a third velocity in a range of velocities from the first velocity to the second velocity; and adjusting a beam position of the beam based on the calculated beam position displacement.