Charged Particle Beam Scanning for Edge Sharpness
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Solution Overview
Problem
Scanning charged particle beam imaging apparatuses face challenges in effectively examining samples due to aliasing effects, reduced edge sharpness, and increased scanning time when scanning at tilted angles, which can lead to false defect detection and reduced throughput.
Innovation Solution
The method involves scanning a charged particle beam over a sample at a tilted angle neither parallel nor perpendicular to the image area, with optimized control to keep the beam within the image area and divert or turn it off when outside, minimizing charging and burn marks, and using a rhomboid or rectangular scan shape to fit the image area precisely, reducing unnecessary scanning time and area exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the charged particle beam is scanned parallel to the die orientation, then the scanning is simple and straightforward, but aliasing effects occur on edges and false defect detection increases
Solution Approach 1:
The patent applies asymmetry by scanning the charged particle beam at a tilted angle (e.g., 45 degrees) relative to the die orientation rather than parallel to it. This asymmetric scanning direction prevents the beam from traveling along sharp horizontal or vertical edges, thereby eliminating aliasing effects and false defect detection while maintaining operational simplicity through automated angle control.
2Measurement precision
If the charged particle beam is scanned at a tilted angle to avoid aliasing effects, then edge sharpness and image quality improve, but the scan area increases and throughput decreases
Solution Approach 1:
The patent resolves the throughput issue by rotating or tilting the entire image area orientation to match the scanning direction, rather than changing the scan angle relative to a fixed image area. This dimensional reorientation allows the tilted scan to cover the same effective area as a parallel scan would, maintaining high throughput while achieving the edge sharpness benefits of tilted scanning.
Solution Approach 2:
The system dynamically adjusts the relationship between scan area and image area orientation. By making the image area orientation adaptive to the scanning direction (or vice versa), the system optimizes the scan path to minimize the actual scan area required, thereby maintaining high scanning throughput while still utilizing tilted angles to avoid aliasing effects on edges.
3Measurement precision
If the scan area is made larger to accommodate tilted angle scanning, then aliasing effects are reduced, but adjacent image areas are exposed to the charged particle beam and suffer from charging and burn marks
Solution Approach 1:
The patent segments the scanning process into precisely controlled segments that exactly match the image area boundaries. By dividing the scan path into discrete segments corresponding to each image area and controlling beam activation only within those segments, the system prevents charged particle beam exposure to adjacent areas, eliminating charging and burn marks while maintaining the aliasing reduction benefits of tilted angle scanning.
Solution Approach 2:
The system uses feedback control to synchronize the charged particle beam activation with the scan position relative to image area boundaries. By continuously monitoring beam position and automatically adjusting beam activation timing, the system ensures the beam is turned off precisely when leaving an image area, preventing exposure and damage to adjacent areas while maintaining optimal scan parameters for aliasing reduction.
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 reduces aliasing effects, increases throughput, and minimizes adverse effects on adjacent areas, allowing for more accurate defect detection and improved image quality without unnecessary exposure to the charged particle beam.
Implementation Method 1
scanning the charged particle beam over the sample in a tilted angle over a least scan area that can render the desired image size with reduced aliasing effect and charging effects
Data Source
AI summary
A method for examining a sample with a scanning charged particle beam imaging apparatus. First, an image area and a scan area are specified on a surface of the sample. Herein, the image area is entirely overlapped within the scan area. Next, the scan area is scanned by using a charged particle beam along a direction neither parallel nor perpendicular to an orientation of the scan area. It is possible that only a portion of the scan area overlapped with the image area is exposed to the charged particle beam. It also is possible that both the shape and the size of the image area are essentially similar with that of the scan area, such that the size of the area projected by the charged particle beam is almost equal to the size of the image area.