Adaptive Mirror Detection for Charging-Distorted Electron Beamlets
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Solution Overview
Problem
Existing multi-beam charged particle microscopes face challenges in maintaining high imaging contrast and throughput due to charging effects at the sample surface, which can lead to distorted secondary electron beamlets and reduced image quality, particularly in semiconductor inspections.
Innovation Solution
A multi-beam charged particle beam system with an adaptive detection system that includes an electron to photon conversion unit, relay optical system with an adaptive mirror array, and high-resolution sensor to individually adjust focus spots, compensating for charging-induced distortions by adjusting mirror angles and aperture positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electron-optical mechanisms with multiple electro-optical lenses are used to compensate charging effects, then imaging contrast can be maintained, but device complexity increases significantly
Solution Approach 1:
The patent extracts the charging effect compensation function from the complex electron-optical lens system and implements it separately through a dedicated distortion correction unit that processes secondary electron beamlets independently, removing the need for multiple electro-optical lenses while maintaining compensation capability
Solution Approach 2:
The patent introduces a distortion correction unit as an intermediary component between the secondary electron detection and imaging systems. This unit acts as a mediator that corrects charging-induced distortions without requiring complex electron-optical mechanisms, thereby simplifying the overall system while maintaining imaging contrast
2Device complexity
If simple electron-optical mechanisms are used for charging compensation, then device complexity is reduced, but the magnitude of correction is insufficient
Solution Approach 1:
The distortion correction unit employs dynamic adjustment mechanisms that can individually control the position and focus of each secondary electron beamlet. This dynamic capability allows the system to achieve large correction magnitudes by adaptively adjusting each beamlet's trajectory and focal point in response to charging effects
Solution Approach 2:
The patent segments the secondary electron beam into multiple individual beamlets, each of which can be independently corrected by the distortion correction unit. This segmentation allows for precise, individualized correction of each beamlet's distortion without requiring complex global electron-optical adjustments
3Productivity
If multi-beam scanning is used to improve throughput, then productivity increases, but charging effects cause beamlet distortion and reduce image quality
Solution Approach 1:
The patent implements a feedback mechanism where the positions and focal points of secondary electron beamlets are continuously monitored and adjusted by the distortion correction unit. This real-time feedback allows the system to maintain high image quality despite the charging effects that occur during multi-beam scanning operations
Solution Approach 2:
The distortion correction unit performs preliminary correction of secondary electron beamlets before they reach the detector. By pre-correcting the beamlet positions and focal points, the system maintains image quality throughout the multi-beam scanning process without requiring post-processing corrections
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
The system maintains high imaging contrast and throughput by accurately detecting and correcting distortions in secondary electron beamlets, enabling precise and accurate wafer inspections despite charging effects.
Implementation Method 1
converting a plurality of second focus spots into a plurality of light beams
Implementation Method 2
individually adjusting a position of at least one third focus spot... by adjusting mirror angles
Data Source
AI summary
A multi-beam charged particle beam system includes a detection unit configured for a dynamic compensation of charging effects of a sample. The detection unit comprises a relay optical system comprising an adaptive mirror array for keeping signal beams at the position of entrance apertures of lightguides od detection elements. Thereby, beam distortions induced by charging effects can be compensated. The disclosure can be applied to, for example, wafer inspection with multi-beam charged particle beam system.