Dual Beam Defect Scanner for Glass Substrates
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Solution Overview
Problem
Current techniques face challenges in accurately detecting defects in thin films on glass substrates due to low reflectivity and the difficulty in separating signals from the top and bottom surfaces, especially for fragile, asymmetric, or large glass samples, which are essential for high technology products.
Innovation Solution
A method involving a scanning system that irradiates the glass sample at or near the Brewster's angle, using dual beams with different wavelengths and angles of incidence, and employing dichroic mirrors and reflectors to direct the beams, allowing for defect detection by measuring scattered and reflected radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If glass samples are spun for inspection, then defect detection can be performed, but fragile, asymmetric, or large samples cannot be tested
Solution Approach 1:
Instead of spinning the glass sample to enable inspection, the patent inverts the approach by keeping the sample stationary and spinning the illumination beam. This is achieved by rotating a mirror or beam directing element to sweep the light source across the sample surface, thereby eliminating mechanical constraints on sample types while maintaining inspection capability
Solution Approach 2:
The patent replaces the mechanical spinning of the sample with an optical scanning mechanism. A rotating mirror or galvanometer-based beam steering system directs the illumination beam across the stationary sample, substituting mechanical sample manipulation with optical field manipulation that has no physical contact requirements
2Measurement precision
If single beam inspection is used, then system is simple, but signals from top and bottom surfaces cannot be separated
Solution Approach 1:
The patent segments the inspection process into two distinct measurement modes using two separate illumination beams: one beam configured to detect defects on the top surface at a first angle of incidence, and another beam configured to detect defects on the bottom surface at a second angle of incidence. This segmentation allows independent measurement of each surface while using a unified optical platform
Solution Approach 2:
The patent introduces angular dimensionality to the inspection system by varying the angle of incidence for different beams. By illuminating from different angles, the system can selectively enhance signals from specific surfaces (top or bottom) while suppressing others, adding an angular degree of freedom to achieve surface-specific detection
3Measurement precision
If Brewster's angle illumination is used, then sensitivity to thin films is improved, but signal separation from top and bottom surfaces becomes difficult
Solution Approach 1:
The patent employs dynamic angle adjustment where the illumination angle is varied during the inspection process. The system illuminates at Brewster's angle to maximize thin film sensitivity, then changes the angle to separate surface signals, allowing both high sensitivity and signal discrimination through temporal separation of measurement conditions
Solution Approach 2:
The patent uses periodic modulation of the illumination angle, alternating between Brewster's angle for enhanced sensitivity and non-Brewster angles for surface differentiation. This periodic switching between measurement modes enables the system to gather both high-sensitivity data and surface-specific information in a cyclic measurement sequence
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
Enables accurate detection of defects in thin films on glass substrates, separating signals from the top and bottom surfaces, and accommodating various glass sample shapes and sizes, improving sensitivity and efficiency in defect inspection.
Implementation Method 1
directing the first beam to irradiate a sample at an angle of incidence of ten degrees of Brewster's angle or less
Implementation Method 2
the first beam passes through a scan lens before irradiating the sample
Implementation Method 3
measuring scattered radiation data resulting from the irradiation of the sample by the second beam
Implementation Method 4
measuring reflected radiation resulting from irradiation of the sample by the first beam
Data Source
AI summary
A method includes enabling a first radiating source configured to output a first beam, enabling a second radiating source configured to output a second beam, directing the first beam to irradiate a sample at an angle of incidence of ten degrees of Brewster's angle or less, directing the second beam to irradiate a sample at an angle of incidence of ten degrees or less (the first beam and the second beam only pass through a single scan lens before irradiating the sample), measuring scattered radiation data resulting from the irradiation of the sample by the second beam, measuring reflected radiation resulting from irradiation of the sample by the first beam, and determining the presence of a defect based at least in part on one of the measurements. The radiating sources may be enabled in an alternating fashion so to improve resulting measurement performance.