Charged Particle Beam Imaging via Alternating Focused and Defocused Scan Lines
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Solution Overview
Problem
Current charged particle beam imaging systems face challenges in regulating sample surface charging, which can distort images due to initial or varying surface charging, and existing methods like pre-scan and post-scan techniques or using a flood gun are inefficient in maintaining uniform charging, especially for large imaging areas.
Innovation Solution
The method involves using a charged particle beam imaging system with a control module that selectively defocuses a charged particle beam probe to regulate sample surface charging by adjusting the condenser lens module, objective lens module, and sample stage, allowing for alternating focused and defocused scans to induce specific charging conditions, enhancing, mitigating, or reversing previous charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a focused charged particle beam probe is used for imaging, then image resolution is improved, but surface charging distortion increases
Solution Approach 1:
The imaging process is divided into multiple scan lines with alternating focus states. Some scan lines are focused for high-resolution imaging while others are defocused for charging regulation, segmenting the function across different scan lines rather than requiring a single beam state
Solution Approach 2:
The method employs periodic alternation between focused and defocused beam states across successive scan lines. This periodic switching allows the system to repeatedly cycle between high-resolution imaging and charging regulation, maintaining overall image quality while controlling surface charging effects
2Stability of the object's composition
If pre-scan or post-scan methods are used to regulate surface charging, then charging uniformity is improved, but imaging time increases
Solution Approach 1:
The method merges the imaging function and charging regulation function into a single integrated process. By combining focused scan lines (for imaging) and defocused scan lines (for charging regulation) into one alternating sequence, the system eliminates the need for separate pre-scan or post-scan regulation steps
Solution Approach 2:
Charging regulation is performed continuously throughout the imaging process rather than as a separate preliminary or follow-up step. The alternating scan lines ensure that charging control is maintained continuously as imaging progresses, preventing charge accumulation without interrupting the imaging workflow
3Stability of the object's composition
If a flood gun is used to scan the entire imaging area for charging regulation, then surface charging control is improved, but processing time increases significantly
Solution Approach 1:
Instead of uniformly scanning the entire imaging area with a flood gun, the method applies defocused charging regulation only to specific scan lines interspersed among focused imaging scan lines. This localized approach provides charging control where needed while maintaining high productivity for the overall imaging process
Solution Approach 2:
The method uses partial action by applying charging regulation to only some scan lines rather than all scan lines or using a separate comprehensive flood gun scan. This partial application of defocused beams provides sufficient charging control to prevent distortion while minimizing the time penalty
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 effectively improves image quality by maintaining optimal surface charging conditions during imaging, reducing distortion and ensuring consistent image quality across large areas without prolonged charging regulation times.
Implementation Method 1
scanning a sample surface in at least one first scan line using a first charged particle beam probe; scanning the sample surface in at least one second scan line using a second charged particle beam probe
Implementation Method 2
The first charged particle beam induces a first charging condition on the sample surface; the second charged particle beam induces a second charging condition on the sample surface
Implementation Method 3
One of the first and second charged particle beam probe is selected to be defocused. An image of the sample is selectively formed from the first, second and third scan lines
Data Source
AI summary
The method includes scanning a sample in at least one first scan line using a first charged particle beam probe; scanning the sample in at least one second scan line using a second charged particle beam probe, and scanning the sample in at least one third scan line using the first charged particle beam probe. The first or second charged particle beam probe is defocused by a control module of the imaging system through adjusting a condenser lens module, an objective lens module, a sample stage of the imaging system, or their combination. An image of the sample is selectively formed from the first, second and third scan lines. The first and the second charged particle beams induce a first charging condition and a second charging condition on the sample surface respectively. The second charging condition can enhance, mitigate, eliminate, reverse or have no effect on the first charging condition.