Singular Beam Nano-Defect Inspection via Bright Fringe Interference
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Solution Overview
Problem
Current optical wafer inspection methods face challenges in detecting nano-defects smaller than 20 nm due to low signal-to-noise ratio and throughput limitations, especially as these defects often reside in dark fringes where illumination intensity is near zero, making them difficult to detect.
Innovation Solution
The use of a singular laser beam with adjustable angle of incidence and polarization, generating standing waves with bright fringes that enhance illumination intensity on nano-defects, allowing for improved detection of scattered light signals from these defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional Gaussian beam illumination is used, then the illumination is uniform across the substrate, but the signal-to-noise ratio for detecting nano-defects is low
Solution Approach 1:
The patent transforms the illumination beam from a conventional Gaussian profile to a singular beam profile by modifying the wavefront curvature parameter. This parameter change creates a unique intensity distribution with a bright fringe that dramatically enhances the optical signal from nano-defects, improving the signal-to-noise ratio for defect detection
Solution Approach 2:
The singular beam creates a localized bright fringe region with enhanced illumination intensity specifically at the substrate surface where defects are located. This local quality enhancement concentrates the useful illumination where it is most needed for defect detection, rather than providing uniform illumination across the entire beam path
2Measurement precision
If stronger light sources are used to enhance defect signal, then the signal-to-noise ratio improves, but the throughput and detection capability for defects smaller than 20 nm remain limited
Solution Approach 1:
The patent changes the spatial intensity distribution parameter of the illumination beam from Gaussian to singular profile. This parameter transformation enables detection of sub-20 nm defects by creating a bright fringe that enhances the optical interaction with ultra-small defects, achieving high precision without sacrificing throughput
Solution Approach 2:
The patent introduces a new dimension to the illumination approach by creating a singular beam with a specific wavefront curvature that produces a bright fringe at the substrate surface. This dimensional change in the beam profile enables detection of previously undetectable defect sizes while maintaining inspection efficiency
3Measurement precision
If different illumination methods are used to detect nano-defects, then detection sensitivity may improve, but the complexity of the inspection system increases
Solution Approach 1:
The patent achieves enhanced defect detection by modifying a single critical parameter - the wavefront curvature of the illumination beam - to create a singular beam profile. This parameter change produces a bright fringe that dramatically improves defect signal detection while avoiding the need for complex multi-component illumination 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 significantly increases the signal-to-noise ratio and enables the detection of nano-defects as small as 5 nm by intensifying the light intensity on defects within bright fringes, overcoming the limitations of traditional Gaussian beam illumination.
Implementation Method 1
generating standing waves with bright fringes that enhance illumination intensity on nano-defects
Implementation Method 2
detecting, by an optical detection system, scattered light from nano-defects present on the substrate within the illuminated spot
Data Source
AI summary
Provided is a method, system, and apparatus for inspecting a substrate. The method comprises illuminating the substrate with a singular laser beam, the singular laser beam forming an illuminated spot on the substrate and a bright fringe at a surface of the substrate, the bright fringe extending over at least a portion of the illuminated spot, and detecting, by an optical detection system, scattered light from nano-defects present on the substrate within the illuminated spot.