Multi-Beam Electron Microscope Feedback for Charging Compensation
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Solution Overview
Problem
Existing multi-beam charged particle microscopes face challenges in maintaining high imaging contrast due to charging effects at semiconductor samples, which can lead to deteriorated image quality, increased crosstalk, or complete loss of secondary electron signals, particularly during wafer inspection tasks.
Innovation Solution
A multi-beam charged particle system with a detection unit that includes a cross-over detection system and actuation mechanism, connected to a contrast control module, dynamically compensates for charging effects by adjusting the lateral position of secondary electron beamlets' pupil distribution using a magneto-dynamic lens and aperture stop, allowing for a wide range of landing energies and rapid correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-beam charged particle microscope is used for wafer inspection, then productivity is improved through parallel scanning, but imaging contrast deteriorates due to charging effects at the sample surface
Solution Approach 1:
The patent implements a feedback mechanism where a monitoring detector continuously measures the pupil distribution of secondary electron beamlets. When charging effects cause the pupil distribution to shift laterally, the system detects this shift and automatically adjusts the beamlet positions or optical elements to compensate, thereby maintaining imaging contrast while preserving high productivity through parallel scanning
Solution Approach 2:
The system dynamically adjusts operational parameters including the lateral position of pupil distribution, beamlet energy, and optical element positions in response to detected charging effects. By changing these parameters in real-time, the system compensates for charging-induced degradation and maintains optimal imaging contrast during high-speed parallel scanning
2Measurement precision
If the secondary electron yield is increased to improve signal strength, then detection sensitivity is improved, but charging effects worsen due to imbalance with incident primary electron current
Solution Approach 1:
The monitoring detector measures pupil distribution shifts caused by charging effects resulting from high secondary electron yield. The system uses this feedback to adjust beamlet positions or optical parameters, compensating for the charging effects and allowing sustained high detection sensitivity without progressive image degradation
Solution Approach 2:
The system employs dynamic adjustment mechanisms that continuously adapt beamlet positions and optical element configurations in response to real-time measurements of pupil distribution. This dynamic compensation allows the system to maintain optimal detection sensitivity while managing charging effects through continuous adaptation rather than static operation
3Manufacturing precision
If electro-optical lenses are used to compensate for charging effects, then imaging contrast is improved, but device complexity increases significantly
Solution Approach 1:
The patent extracts and monitors only the critical parameter of pupil distribution lateral position using a dedicated monitoring detector. By focusing compensation efforts on this single key parameter rather than attempting to correct all imaging parameters simultaneously, the system achieves effective charging compensation with simpler control mechanisms and reduced overall system complexity
Solution Approach 2:
The system introduces a monitoring detector as an intermediary element that measures pupil distribution shifts and provides feedback information. This intermediary enables indirect compensation by detecting charging effects and triggering appropriate corrections, achieving imaging contrast improvement without requiring complex direct manipulation of multiple electro-optical parameters
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 achieves improved imaging contrast and accuracy in wafer inspection by effectively compensating for charging effects, enabling higher precision and accuracy in imaging semiconductor features.
Implementation Method 1
adjusting the lateral position of secondary electron beamlets' pupil distribution using a magneto-dynamic lens
Implementation Method 2
an aperture stop arranged in a cross-over or pupil plane of the detection unit for filtering the plurality of secondary electron beamlets
Implementation Method 3
The bundle of primary charged particle beamlets is focused by an objective lens on a surface of a sample
Data Source
AI summary
A multi-beam charged particle system with a secondary electron imaging system is configured to dynamically compensate charging effects. The multi-beam charged particle system comprises an improved cross-over detection system and a cross-over actuation mechanism, which are both connected to a contrast control module. The system allows for closed-loop control of an intensity distribution of a plurality of secondary electron beamlets within a cross-over or pupil plane. The disclosure can be applied to wafer inspection with multi-beam charged particle system.