Offset-Stage Optical Imaging for Low-Magnification Sample Navigation
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Solution Overview
Problem
Charged particle beam apparatuses face difficulties in accurately and easily obtaining low-magnification images of samples due to limited field of view, requiring additional optical observation systems for navigation.
Innovation Solution
Incorporating a charged particle beam optical system, a detector, an imaging device, a rotatable stage, and an image composition unit that combines multiple optical images to generate a composite low-magnification image, allowing the stage to be moved and rotated to minimize the movement range and reduce step differences between images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the stage is rotated around the center of the imaging range, then the imaging position remains stable, but the movement range required to capture the entire sample increases
Solution Approach 1:
The patent applies asymmetry by deliberately offsetting the rotation center from the center of the imaging range. The stage rotation center is positioned at a distance from the optical imaging device's center, creating an asymmetric configuration that allows the sample to be imaged at multiple rotation angles while keeping the stage movement range minimal, thereby reducing the required vacuum sample chamber size.
Solution Approach 2:
The patent transitions from a single-center rotation approach to an offset-center rotation approach, effectively utilizing the spatial dimension differently. By positioning the rotation center away from the imaging center, the system captures the entire sample within a smaller movement envelope, reducing the required chamber area while maintaining imaging capability.
2Area of stationary object
If multiple optical images are captured at different stage positions, then a complete low-magnification image can be obtained, but image seams and positioning accuracy deteriorate
Solution Approach 1:
The patent implements feedback by using the optical image to determine the stage position and then using this position information to accurately composite the multiple images. The system captures optical images at different rotation angles, determines the stage position based on these images, and uses this feedback to precisely align and composite the images, minimizing seams and maintaining positioning accuracy.
Solution Approach 2:
The patent creates multiple copies of the sample image at different rotation angles and positions, then composites these copies into a complete low-magnification image. By capturing and combining multiple optical image copies, the system achieves comprehensive sample coverage while maintaining accuracy through proper alignment based on stage position feedback.
3Adaptability or versatility
If an optical observation system is added for navigation, then low-magnification imaging capability is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by making the optical imaging device serve multiple functions: it provides low-magnification navigation imaging and simultaneously provides feedback for stage position determination during electron beam observation. This multi-functional approach adds navigation capability while avoiding the need for completely separate observation systems, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges the optical navigation system with the electron beam observation system by integrating the optical imaging device's positioning feedback into the stage control system. This combination allows both systems to work together synergistically, providing low-magnification imaging capability while reducing overall system complexity compared to having entirely separate systems.
Data Source
AI summary
The charged particle beam apparatus includes a charged particle beam optical system that irradiates a sample mounted on a sample stage with a charged particle beam; a detector that detects a signal generated from the sample; a charged particle beam imaging device that acquires an observation image from the signal detected by the detector; an optical imaging device that captures an optical image of the sample; a stage that rotatably holds the sample stage; a stage control device that controls movement and rotation of the stage; and an image composition unit that combines the plurality of optical images to generate a composite image. The stage control device is configured to move the stage so that the center of an imaging range of the optical imaging device is located at a position different from the rotation center of the stage and then, to rotate the stage, the optical imaging device acquires a plurality of optical images relating to different positions of the sample by rotation operation, and the image composition unit combines the plurality of optical images obtained by the rotation operation to generate a composite image.