Beam Positioning Drift Correction in Dual-Beam Processing
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Solution Overview
Problem
Beam positioning in microfabrication processes, such as semiconductor manufacturing and transmission electron microscopy, is challenged by beam drift due to mechanical and thermal instabilities, which can lead to inaccuracies and damage to samples, especially when using fiducials for correction.
Innovation Solution
A method that predicts beam drift using a mathematical model and corrects the beam positioning continuously during processing, allowing for precise alignment and minimization of fiducial damage by imaging the fiducial near the processing area without stage movement, and periodically realigning based on measured drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the beam is periodically directed to image the fiducial to correct positioning drift, then the beam positioning accuracy is improved, but the fiducial is degraded by repeated scanning
Solution Approach 1:
The patent introduces a separate detection beam (electron beam) as an intermediary to image the fiducial, while the processing beam (ion beam) performs the actual sample processing. This mediator approach allows positioning correction without using the processing beam to scan the fiducial, thereby preventing fiducial degradation from repeated processing beam scanning.
Solution Approach 2:
The patent replaces the mechanical approach of using the same ion beam for both imaging and processing with a dual-beam system where an electron beam handles imaging/detection and an ion beam handles processing. This substitution eliminates the conflict between imaging and processing functions that causes fiducial degradation.
2Productivity
If the beam current is increased to improve processing speed, then the productivity is improved, but the sample damage increases
Solution Approach 1:
The patent segments the beam functions into two separate beams: the ion beam is dedicated to material processing (cutting, deposition) and the electron beam is dedicated to imaging and detection. This segmentation allows the ion beam to operate at high current for fast processing without concern for fiducial imaging, while the electron beam handles the delicate imaging tasks, thus enabling high productivity without excessive sample damage.
Solution Approach 2:
The electron beam serves multiple functions: it images the fiducial for positioning correction, images the sample during processing, and detects secondary ions for compositional analysis. This multi-functionality allows the system to maintain high ion beam current for productivity while the electron beam monitors and corrects positioning and detects sample conditions to prevent damage.
3Object-affected harmful factors
If the fiducial is positioned far from the processing area to avoid interference, then the fiducial is protected from damage, but the stage movement between fiducial imaging and processing increases positioning error
Solution Approach 1:
The patent replaces the mechanical stage movement approach with a dual-beam system where both the electron beam and ion beam can independently scan and focus on different locations. This allows the fiducial and processing area to be at different positions on the sample without requiring stage movement between them, eliminating the positioning errors that would result from stage repositioning while still allowing the fiducial to be positioned optimally for protection.
Data Source
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AI summary
An improved method and apparatus of beam processing corrects for beam drift while a beam is processing a sample. The beam position is aligned using a fiducial that is sufficiently near the working area so that the fiducial can be imaged and the sample processed without a stage moving. During processing, the beam positioning is corrected for drift using a model that predicts the drift.