Composite Signal Defect Detection in Particle Beam Inspection
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Solution Overview
Problem
Current scanning electron microscope (SEM) inspection systems face challenges in distinguishing real defects from false or nuisance defects due to inadequate utilization of data from multiple detectors, leading to suboptimal sensitivity and increased false defect reports, especially when inspecting substrates with small variations in surface topography.
Innovation Solution
The method involves combining and processing data sets from two or more detectors before determining if an anomaly is a significant defect, using techniques such as calculating composite difference signals and applying multi-dimensional defect thresholds to enhance sensitivity while minimizing false and nuisance defect reports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If data from multiple detectors are processed separately and independently, then the inspection system can maintain simple processing logic, but the sensitivity to detect real defects is reduced and false defect reports increase
Solution Approach 1:
The patent combines data sets from multiple detectors (secondary electron detector and backscattered electron detector) by calculating a composite difference signal that integrates information from both detectors. This merging of data sources improves defect detection sensitivity while reducing false defect reports, as the composite signal leverages the complementary strengths of each detector type.
Solution Approach 2:
The patent transitions from separate one-dimensional analysis of each detector's data to a two-dimensional composite analysis. By creating a composite difference signal that considers both secondary electron and backscattered electron data simultaneously, the system adds a dimensional aspect to the defect detection process, enabling better discrimination between real defects and false signals.
2Measurement precision
If a low defect threshold is applied to increase sensitivity, then more real defects are detected, but the number of false and nuisance defect reports increases significantly
Solution Approach 1:
By merging data from secondary electron and backscattered electron detectors into a composite difference signal, the system achieves high sensitivity with reduced false positives. The composite approach allows the use of effective thresholds that are both sensitive to real defects and selective against false reports, as each detector type provides complementary information that validates defect signals.
Solution Approach 2:
The patent implements a feedback mechanism where the composite difference signal from multiple detectors is used to adjust and optimize the defect threshold. The system analyzes the combined data to determine appropriate threshold levels that maximize real defect detection while minimizing false and nuisance defects, creating a self-optimizing inspection process.
3Reliability
If traditional single-detector SEM inspection is used, then the system structure remains simple, but the ability to distinguish real defects from surface topography variations is insufficient
Solution Approach 1:
The patent merges data from secondary electron detectors (sensitive to surface topography) and backscattered electron detectors (sensitive to material composition) to create a composite inspection signal. This combination enables reliable distinction between real defects and surface variations, as each detector type responds differently to various defect types, providing cross-validation capability.
Solution Approach 2:
The multi-detector system performs multiple inspection functions simultaneously: secondary electron detection for surface topography analysis, backscattered electron detection for material composition analysis, and composite analysis for comprehensive defect characterization. This multi-functionality increases defect classification accuracy without requiring separate inspection systems.
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 allows for the detection of virtually all critical defects while reducing the number of false and nuisance defects, providing operators with improved flexibility to selectively review specific defect types and classify defects based on attributes like size, shape, and material context.
Implementation Method 1
The electrons in the beam, known as 'primary electrons,' penetrate the substrate and dislodge electrons within the material. Some of these dislodged electrons, known as 'backscattered electrons' or 'secondary electrons,' escape from the surface of the substrate.
Data Source
AI summary
A method and apparatus for inspection and review of defects is disclosed wherein data gathering is improved. In one embodiment, multiple or segmented detectors are used in a particle beam system.