Wafer Inspection Multi-Spot Illumination Detector Reduction
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Solution Overview
Problem
Current multi-spot wafer inspection systems require a large number of detectors to achieve optimal signal-to-noise ratio and defect classification, which increases costs and complexity, and not all collection channels provide equal benefits, making it inefficient to maintain high sensitivity across all defect types.
Innovation Solution
The system reduces the number of detectors by using a collection subsystem that images light from multiple spots onto fewer detectors, with some spots imaged onto a single detector, and employs a computer subsystem to detect defects using outputs from both first and second detection subsystems, optimizing detector usage based on the importance of each collection channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of detectors is increased to maintain high sensitivity for all defect types, then the signal-to-noise ratio is improved, but the system complexity and cost increase
Solution Approach 1:
The patent combines multiple collection channels into a single detector by using a dichroic beamsplitter to separate wavelengths and a single detector to detect both channels simultaneously. This merging approach maintains the signal-to-noise ratio benefits of multiple channels while reducing the number of detectors needed, thereby decreasing system complexity and cost.
Solution Approach 2:
The single detector is designed to perform multiple functions by detecting light from both collection channels through wavelength separation. The detector universally handles both defect types that were previously requiring separate detectors, achieving multi-functionality with a single component.
2Adaptability or versatility
If multiple collection channels are used to detect different defect types, then the classification capability is improved, but the number of detectors and system complexity increase
Solution Approach 1:
The patent merges multiple collection channels that detect different defect types into a single detector system. The dichroic beamsplitter combines the optical paths of both channels, allowing a single detector to capture and classify both defect types, thereby maintaining classification capability while reducing detector count.
Solution Approach 2:
The dichroic beamsplitter acts as an intermediary element that separates and redirects different wavelengths from multiple collection channels to a single detector. This mediator enables the detector to receive and classify signals from both channels without requiring separate detectors for each channel.
3Reliability
If a large number of detectors are used to cover all collection channels, then the defect detection sensitivity is improved, but the system cost increases
Solution Approach 1:
The patent combines multiple collection channels into a single detector using wavelength separation optics. This merging maintains the sensitivity benefits of having multiple channels while significantly reducing the number of detectors required, thereby lowering system cost without compromising detection sensitivity.
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 approach reduces the number of detectors needed while maintaining high sensitivity for critical defect types, improving defect capture and reducing system complexity and costs, while still achieving enhanced signal-to-noise ratio and classification capabilities.
Implementation Method 1
In order to separate these optical scattering signals, typically the collecting optics is constructed to separately resolve the scattering from each spot
Data Source
AI summary
Systems configured to inspect a wafer are provided. One system includes an illumination subsystem configured to illuminate a set of spots on a wafer and a collection subsystem configured to collect light from the set of spots. The collection subsystem separately images the light collected from each of the individual spots onto only a corresponding first detector of a first detection subsystem. The collection subsystem also images the light collected from at least some of the individual spots onto a number of second detectors of a second detection subsystem that is less than a number of spots in the set. Output produced by the first and second detectors can be used to detect defects on the wafer.