Microscope Scan Alignment Using Confidence-Distance Markers
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Solution Overview
Problem
Existing methods for measuring samples with vertical structures face challenges in accurately aligning multiple scans taken at an angle, leading to potential errors in reconstructing the vertical evolution of structures due to defocusing issues with alignment markers.
Innovation Solution
A method that computes a confidence distance based on the angle of the focusing plane with respect to the sample's surface, allowing the selection of appropriate alignment markers within this distance for precise lateral alignment, eliminating the need for measuring defocusing characteristics and reducing the number of necessary markers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment markers are placed on the top surface for lateral alignment, then alignment can be performed, but markers far from the intersection become defocused and reduce measurement precision
Solution Approach 1:
The patent applies local quality by defining a confidence distance threshold that creates different zones for marker placement. Only markers within this local region near the intersection are considered reliable, as they maintain adequate focus. This spatial differentiation ensures that alignment operations use only markers with sufficient image quality, resolving the contradiction between having markers available and ensuring they remain in focus.
2Adaptability or versatility
If multiple alignment markers are used to ensure coverage, then alignment coverage is improved, but the complexity of selecting appropriate markers increases
Solution Approach 1:
The patent changes the parameter of marker selection from a complex multi-factor decision to a simple distance-based criterion. By using the confidence distance threshold as the sole selection parameter, the system maintains adaptability and coverage while dramatically reducing selection complexity. Any marker within the threshold distance automatically qualifies, eliminating the need for complex evaluation of multiple marker characteristics.
3Reliability
If the depth of field is increased to capture all markers in focus, then all markers remain sharp, but the scanning resolution and precision are reduced
Solution Approach 1:
The patent applies preliminary action by pre-calculating the confidence distance threshold based on the microscope's depth of field and slope angle before the scanning process. This allows the system to identify suitable markers in advance and plan the alignment strategy beforehand, eliminating the need to adjust focus settings during scanning. The threshold is determined by the formula involving depth of field and tangent of the slope angle, ensuring optimal balance between focus consistency and scanning resolution.
Data Source
AI summary
The present invention relates to a method for measuring a sample with a microscope, the method comprising scanning the sample using a focusing plane having a first angle with respect to a top surface of the sample and computing a confidence distance based on the first angle. The method further comprises selecting at least one among a plurality of alignment markers on the sample for performing a lateral alignment of the scanning step and/or for performing a lateral alignment of an output of the scanning step. In particular, the at least one alignment marker selected at the selecting step is chosen among the alignment markers placed within the confidence distance from an intersection of the focusing plane with the top surface.