Charged Particle Beam Scanning Pattern for Charge Accumulation
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Solution Overview
Problem
In scanning electron microscopes, the influence of electric charge on semiconductor samples due to beam irradiation leads to image contrast variations and measurement precision issues, particularly when using low-dielectric constant materials, as existing methods like blanking do not effectively suppress charge accumulation between scan lines and frames.
Innovation Solution
A charged particle beam device with a scanning deflector and control device that scans using a pattern where scan directions are rotated by 90° and 180° between frames, minimizing beam irradiation outside the field of view and equalizing electric charge distribution without blanking, thereby reducing image drift and contrast unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If blanking is performed to suppress beam irradiation between scan lines and frames, then beam irradiation influence is reduced, but electric charge is still attracted during beam irradiation to stop plate and measurement precision deteriorates
Solution Approach 1:
The patent extracts the harmful blanking operation from the scanning system and replaces it with a continuous scanning method that connects scan lines and frames through extended trajectories. By removing the blanking step that deflects beams to stop plates, the system eliminates the associated electric charge accumulation while maintaining continuous sample irradiation for precise measurements.
Solution Approach 2:
The patent implements continuous scanning by extending scan lines beyond frame boundaries and connecting ending points of one frame to starting points of the next frame. This continuous trajectory eliminates interruptions and blanking operations, maintaining constant beam irradiation on the sample without causing charge accumulation, thereby preserving measurement precision.
2Object-affected harmful factors
If typical raster scanning with blanking is used, then beam irradiation between scan lines is suppressed, but electric charge distribution becomes uneven and image contrast varies
Solution Approach 1:
The patent introduces asymmetry by extending scan lines beyond traditional frame boundaries and connecting them to starting points of subsequent frames. This asymmetric scanning pattern redistributes beam irradiation uniformly across the sample surface, preventing localized charge accumulation and ensuring uniform image contrast throughout the field of view.
Solution Approach 2:
The patent transitions from conventional two-dimensional frame-based scanning to a three-dimensional continuous trajectory that spans across frame boundaries. By adding the temporal dimension of continuous scanning that connects frames sequentially, the system achieves uniform charge distribution while maintaining suppressed electric charge accumulation.
3Productivity
If scan direction is inverted for every scan line (reciprocating scanning), then scanning efficiency is improved, but electric charge influence at scan start and end points increases
Solution Approach 1:
The patent applies preliminary action by extending scan lines beyond frame boundaries in advance, so that the ending point of one frame naturally connects to the starting point of the next frame. This pre-planned continuous trajectory eliminates sudden beam deflections at frame transitions, preventing charge accumulation at scan start and end points while maintaining reciprocating scanning efficiency.
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 suppresses electric charge influence, improving measurement precision by reducing image blurring and contrast asymmetry, ensuring symmetric pattern edges and uniform electric charge distribution within the field of view.
Implementation Method 1
a scanning deflector that performs scanning with a charged particle beam emitted from a charged particle source
Implementation Method 2
when a sample is irradiated with an electron beam, secondary electrons emitted from the sample are detected
Data Source
AI summary
The objective of the present invention is to provide a charged particle beam device wherein scanning is performed through a scanning pattern that may suppress the influence from charge accumulation without having to perform blanking. In order to achieve this objective, a charged particle beam device is proposed wherein a first scan line is scanned by deflecting a charged particle beam in a first direction. The charged particle beam is deflected in a manner where the ending point of the first scan line is connected to the scan starting point of a second scan line which is arranged to be parallel to the first scan line so as to draw a scanning trajectory, thereby modifying the scan line position. The second scan line is scanned by scanning the charged particle beam from the scan starting point of the second scan line toward a second direction that is opposite to the first direction. After scanning the second scan line, the charged particle beam device scans the interior of a first frame by repeating the scan line position modification and the scanning of the charged particle beam toward the opposite direction. After scanning the first frame, the charged particle beam device starts the scanning of a second frame with the scan ending point contained within the first frame serving as the scan starting point.