Aberration Corrector Alignment in Multi-Beam Electron Systems
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Solution Overview
Problem
In multiple electron beam image acquisition systems, the narrow space between the electromagnetic lens and the aberration corrector poses a challenge for axis adjustment, leading to limitations in correcting aberrations such as field curvature, astigmatism, and distortion, which affects the accuracy of pattern inspection in semiconductor manufacturing.
Innovation Solution
A multiple electron beam image acquisition apparatus with an electromagnetic lens, an aberration corrector in a magnetic field, a movable aperture substrate, and a stage control circuit that aligns the aberration corrector with the electromagnetic lens by shifting the beam trajectory and moving the aberration corrector stage, allowing for independent selection and alignment of individual electron beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If axis adjustment is performed for the aberration corrector after electromagnetic lens alignment in narrow space, then aberration correction capability is improved, but the pre-adjusted electromagnetic lens axis becomes displaced
Solution Approach 1:
Instead of adjusting the aberration corrector after electromagnetic lens alignment (which causes displacement), the patent inverts the sequence by first adjusting the aberration corrector and then performing electromagnetic lens alignment. This reversal prevents the displacement problem while maintaining both alignment requirements
Solution Approach 2:
The patent performs preliminary alignment of the aberration corrector before introducing the electromagnetic lens alignment step. By pre-positioning the aberration corrector using alignment marks and stage movement, the subsequent electromagnetic lens alignment can be performed without causing mutual displacement
2Productivity
If multiple electron beams are used for pattern inspection, then inspection efficiency is improved, but beam blur and distortion due to aberration increase
Solution Approach 1:
The patent introduces an aberration corrector as an intermediary component between the electromagnetic lens and the substrate. This corrector actively compensates for the beam blur and distortion caused by using multiple electron beams, thereby maintaining focus accuracy while preserving the high inspection efficiency of multi-beam systems
Solution Approach 2:
The patent changes the optical parameters of the electron beam by using the aberration corrector to adjust beam trajectories and focus positions. By dynamically correcting aberration parameters, the system maintains high beam accuracy despite using multiple beams for efficient inspection
3Volume of moving object
If the space between electromagnetic lens and aberration corrector is narrowed, then device compactness is improved, but axis adjustment becomes difficult
Solution Approach 1:
The patent replaces manual or mechanical axis adjustment methods with an automated stage control system. The stage control circuit automatically moves the aberration corrector based on alignment mark detection, eliminating the need for manual adjustment operations and making the narrow-space configuration operable
Solution Approach 2:
The system performs self-alignment by automatically detecting alignment marks and computing the required stage movement. The stage control circuit autonomously positions the aberration corrector without external intervention, enabling compact design while maintaining adjustment capability
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 solution enables precise axis adjustment and aberration correction, even in tight spaces, enhancing the accuracy of pattern inspection and improving the yield in semiconductor manufacturing by maintaining the alignment of the electromagnetic lens and aberration corrector without displacing the pre-adjusted electromagnetic lens axis.
Implementation Method 1
an electromagnetic lens (221) configured to receive incidence of multiple electron beams (20) and refract them
Implementation Method 2
an aberration corrector (230) disposed in a magnetic field of the electromagnetic lens (221), and configured to correct aberration of the multiple electron beams (20)
Implementation Method 3
a detector (243) configured to detect multiple secondary electron beams emitted due to that a surface of a target object is irradiated with multiple electron beams (20)
Data Source
AI summary
A multiple-electron-beam-image acquisition apparatus includes an electromagnetic lens to receive and refract multiple electron beams, an aberration corrector, disposed in a magnetic field of the electromagnetic lens, to correct aberration of the multiple electron beams, an aperture-substrate, disposed movably at the upstream of the aberration corrector with respect to an advancing direction of the multiple electron beams, to selectively make an individual beam of the multiple electron beams pass therethrough independently, a movable stage to dispose thereon the aberration corrector, a stage control circuit, using an image caused by the individual beam selectively made to pass, to move the stage to align the position of the aberration corrector to the multiple electron beams having been relatively aligned with the electromagnetic lens, and a detector to detect multiple secondary electron beams emitted because the target object surface is irradiated with multiple electron beams having passed through the aberration corrector.