Off-Axis Substrate Defect Detection Using Dark-Field and Photoluminescence
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Solution Overview
Problem
Existing techniques struggle to accurately detect and classify a wide variety of crystalline defects in monocrystalline substrates like silicon carbide, often confusing them with non-crystalline defects such as particles or scratches, and lack efficiency in throughput and versatility.
Innovation Solution
A device and method utilizing a combination of directional dark-field and photoluminescence detection schemes, with illumination light sources positioned at specific angles relative to the substrate's crystallographic axes, to enhance defect discrimination and classification, allowing high throughput and versatility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dark-field detection is used to reveal surface defects, then detection simplicity and efficiency are improved, but defect classification capability deteriorates due to inability to distinguish crystalline defects from non-crystalline defects
Solution Approach 1:
The patent combines dark-field detection and photoluminescence detection into a single integrated system. The dark-field detection unit reveals surface defects through light scattering, while the photoluminescence detection unit characterizes crystalline defects through light emission properties. By merging these two detection methods and processing their results together, the system achieves both high detection efficiency and accurate defect classification, resolving the contradiction between simplicity and classification capability.
Solution Approach 2:
The patent introduces an intermediary processing step that analyzes results from both detection methods. The processing unit compares dark-field scattering patterns with photoluminescence emission characteristics to distinguish crystalline defects from non-crystalline defects. This intermediary analysis layer enables accurate classification while maintaining the efficiency of dark-field detection.
2Measurement precision
If photoluminescence detection is used to characterize crystalline defects, then defect characterization capability is improved, but detection simplicity deteriorates and throughput decreases
Solution Approach 1:
The patent merges photoluminescence detection with dark-field detection in an integrated system. The dark-field detection provides rapid initial screening of surface defects, while photoluminescence detection provides detailed characterization of crystalline defects. By combining these methods and processing results together, the system achieves accurate defect characterization without sacrificing throughput, as the two methods work complementarily rather than sequentially.
3Measurement precision
If multiple detection techniques are combined to improve defect classification, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges dark-field detection and photoluminescence detection into a single integrated device with shared optical components and a unified processing unit. This merging approach enables accurate defect classification through multiple detection modalities while avoiding the complexity of separate independent systems, as the two detection methods are coordinated within a single device architecture.
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 method effectively distinguishes crystalline defects from non-crystalline defects, providing comprehensive characterization with high accuracy and efficiency, suitable for various defect types in off-axis monocrystalline substrates.
Implementation Method 1
Dark-field detection allows revealing the defects present at the surface of a substrate. This technique is based on an illumination of the surface and the collection of the scattered light.
Implementation Method 2
Photoluminescence is manifested by certain materials which, when subjected to an excitation radiation of a certain wavelength, emit a radiation of a different wavelength.
Data Source
Figure 1~2a
Figure 2b~2c
Figure 3a~3b
AI summary
The invention relates to a device (100, 200, 300) for detecting crystalline defects in an off-axis monocrystalline substrate (10), wherein the normal (2) to the surface of the substrate (10) is tilted with respect to the crystallographic growth axis (3) by a tilt angle (4), the tilt angle (4) being contained in a plane, called angle plane, perpendicular to the surface, the device (100) comprising: - at least one detector (14, 14', 14a, 14b, 14c), - at least one illumination light source (12) configured to illuminate the substrate (10) with an illuminating light beam (13), the at least one illumination light source (12) being arranged in at least one of a first position and a second position, - at least one excitation light source (19) configured to illuminate the substrate with an excitation light beam (20) configured to produce an emission of photoluminescence light by the substrate (10), - imaging means (16, 17) configured to image the substrate (10) according to a field of view on the at least one detector(14, 14', 14a, 14b, 14c), said at least one detector producing at least one image of the substrate (10), and - processing means (18) configured to detect crystalline defects using said at least one image of the substrate (10), wherein the at least one illumination light source (12) and the imaging means (16, 17) are arranged in a dark-field configuration, and wherein in the first position, the at least one illumination light source (12) is arranged such that the illuminating light beam (13) is parallel or quasi-parallel to the angle plane (4), and in the second position, the at least one illumination light source (12) is arranged such that the illuminating light beam (13) is parallel or quasi-parallel to a plane, called perpendicular plane, containing the normal (2) to the surface and being perpendicular to the angle plane. The invention also relates to a method for detecting crystalline defects in an off-axis monocrystalline substrate.