Charged Particle Beam Scan Position Correction
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Solution Overview
Problem
The existing technique for moving the scan position of a charged particle beam using a deflector faces challenges in precision and accuracy, especially when dealing with multiple measuring points within the deflection region, where the degree of image shift error varies significantly, leading to difficulties in achieving the desired scan position due to the deflective function of lenses.
Innovation Solution
A method is proposed where a reference target object is used to set the scan position within the deflectable range, and the deflection amount is corrected based on the shift of each target object after deflection, allowing for accurate positioning by adjusting the charged particle beam conditions at individual deflection positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a deflector is used to move the scan position of a charged particle beam, then the scan position can be moved speedily, but the scan position cannot always be moved to a desired location due to lens deflection effects
Solution Approach 1:
The patent applies preliminary action by measuring and storing the sensitivity to image shift in advance at multiple deflection positions before actual measurement. The system pre-characterizes the deflective function of the lens at each position, allowing the control to compensate for position errors by referencing pre-measured sensitivity data, thus achieving both speed and accuracy.
2Device complexity
If a single sensitivity measurement is used for image shift correction, then the correction process is simple, but it cannot handle multiple measuring points where image shift error varies by position
Solution Approach 1:
The patent applies segmentation by dividing the measurement region into multiple discrete deflection positions and measuring the sensitivity to image shift at each position separately. This creates a position-specific correction map that allows accurate measurement across multiple points while maintaining a relatively simple correction process by selecting the appropriate sensitivity value based on the current deflection position.
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 approach enables precise and accurate deflection of the scan position within the deflectable range, ensuring proper optical conditions and improving the accuracy of measurement and inspection in scanning electron microscopes.
Implementation Method 1
A technique for moving the scan position of an electron beam on a specimen by the deflector
Implementation Method 2
under the influence of, for example, deflective function of lens
Data Source
AI summary
In a method of scanning a charged particle beam which can position the scan position to a proper location inside a deflectable range of the scan position of charged particle beam, the scan position of charged particle beam is deflected to a plurality of target objects inside a scan position deflectable region and on the basis of a shift of a target object at a scan location after deflection, the deflection amount at the scan location is corrected.