Multi-Beam Wafer Inspection Ghost Correction for Crosstalk Noise
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Solution Overview
Problem
Multi-electron beam inspection devices face issues with crosstalk noise, ghost images, and difficulty in detecting defects due to sample charging, which affect image sensitivity and accuracy in semiconductor wafer inspection.
Innovation Solution
A processor system capable of communicating with a multi-charged particle beam device, which irradiates multiple scanning regions with charged particle beams and uses detectors to generate images, recognizes ghosts and modifies their occurrence regions to reduce crosstalk noise, allowing for accurate defect detection and measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple detectors are used to collectively acquire images from multiple irradiation spots, then throughput is improved, but crosstalk noise increases due to secondary electrons from different beams being mixed
Solution Approach 1:
The patent divides the image acquisition process into multiple sequential stages: a first image is acquired with a first charged particle beam, and a second image is acquired with a second charged particle beam. By processing beams and detectors separately in time rather than simultaneously, the patent segments the multi-beam operation to eliminate crosstalk while maintaining throughput through parallel processing of separated data streams.
Solution Approach 2:
The patent performs preliminary image acquisition with the first charged particle beam before acquiring the second image. This sequential approach ensures that the first image data is fully captured and processed before the second beam operation begins, preventing secondary electron mixing while allowing efficient utilization of multiple detectors in separate time slots.
2Measurement precision
If secondary electron images are used for defect detection, then sensitivity is improved, but ghost images interfere with observation and measurement accuracy
Solution Approach 1:
The patent extracts and removes ghost image components from the captured images through image processing. By identifying the characteristic patterns of ghost images (which appear at specific locations relative to the primary image based on charged particle beam deflection characteristics), the system separates and eliminates these harmful artifacts while preserving the genuine defect information.
Solution Approach 2:
The patent converts the ghost image phenomenon from a harmful interference into a useful indicator. By analyzing the position and characteristics of ghost images, the system can actually identify the locations of charged particle beam irradiation and use this information to improve defect detection accuracy, turning the interference into a diagnostic tool.
3Measurement precision
If charged particle beams are used for high-resolution inspection, then image resolution is improved, but sample charging effects increase causing measurement errors
Solution Approach 1:
The patent employs periodic alternation between different charged particle beam irradiation operations. By systematically switching between first and second beam operations with multiple detectors, the system creates a periodic measurement cycle that allows for compensation of charging effects through comparative analysis of images acquired at different time points in the cycle.
Solution Approach 2:
The patent implements feedback mechanisms where images from multiple detectors and multiple beam operations are compared and analyzed. The system uses the information from ghost image positions and image variations to detect and compensate for sample charging effects, adjusting measurements based on feedback from the actual observed image characteristics.
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 effectively reduces crosstalk noise and improves image sensitivity, enabling accurate defect detection and measurement on semiconductor wafers by correcting ghost images and accounting for sample charging effects.
Implementation Method 1
detect secondary electrons from at least the first scanning region by a first detector to generate a first image; detect secondary electrons from at least the second scanning region by a second detector to generate a second image
Data Source
AI summary
A processor system capable of communicating with the multi-charged particle beam device includes reducing an influence of first crosstalk caused by a first detector detecting secondary electrons from a second scanning region by recognizing a first ghost caused by the first crosstalk from a first image using the first image. The processor system modifies a first occurrence region of the first ghost, or outputs a defect candidate position as a defect position when the detected defect candidate position is outside the first occurrence region.