Multi-Beam SEM Dark Field Imaging via Segmented Detector Array
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Solution Overview
Problem
Current multi-beam scanning electron microscope (SEM) systems lack dark field imaging capabilities, which limits their ability to detect features that are not visible in bright field images, such as raised features on semiconductor wafers and other thin polished plates.
Innovation Solution
The integration of an electron source and optical devices to produce multiple primary beamlets that interact with a target, combined with a multi-channel or high-density detector array to capture and process image beamlets, enabling the creation of dark field images by excluding unscattered beams and utilizing shadow information from outer detector channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-beam SEM systems are used to increase throughput, then productivity is improved, but dark field imaging capability is lost
Solution Approach 1:
The detection system is segmented into multiple independent detector channels, each capable of detecting specific beamlet characteristics. The multi-beam system divides the electron beam into multiple primary beamlets that scan different regions of the target simultaneously, and the detector array segments the detection function to capture scattered electrons from different angles, enabling dark field imaging while maintaining multi-beam throughput
Solution Approach 2:
The patent adds a new dimension to the detection capability by implementing angular-resolved detection. Instead of only detecting electrons along the primary beam direction (bright field), the system detects electrons scattered at various angles (dark field) by positioning detectors at different angular positions relative to the beam path, thus adding angular dimension to the imaging capability
2Measurement precision
If detector array density is increased to improve dark field imaging, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The detector array is segmented into multiple independent detection channels, each responsible for detecting electrons from specific angular ranges. This segmentation allows precise measurement of scattered electron intensity at different angles while keeping each individual detector channel relatively simple in design
Solution Approach 2:
The detector array is designed to serve multiple functions simultaneously: it can detect secondary electrons, backscattered electrons, and electrons scattered at various angles. This multi-functionality allows a single detector array structure to provide both bright field and dark field imaging capabilities, as well as compositional and topographical information, without requiring separate specialized detectors for each function
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 configuration enhances the inspection capabilities of multi-beam SEM systems by allowing the detection of defects and surface features that were previously invisible, improving defect inspection and metrology, and enabling the creation of three-dimensional topology and vertical distance measurements.
Implementation Method 1
The electrons interact with atoms in the target, producing various signals that contain information about the surface topography and composition of the target
Data Source
AI summary
Multi-beam scanning electron microscope (SEM) inspection systems with dark field imaging capabilities are disclosed. An SEM inspection system may include an electron source and at least one optical device. The at least one optical device may be configured to produce a plurality of primary beamlets utilizing electrons provided by the electron source and deliver the plurality of primary beamlets toward a target. The apparatus may also include an array of detectors configured to receive a plurality of image beamlets emitted by the target in response to the plurality of primary beamlets and produce at least one dark field image of the target.