Slit-Beam Defect Inspection for Complex Substrate Patterns
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Solution Overview
Problem
Conventional defect inspection methods fail to effectively detect very small particle-like contamination, thin-film-like contamination, scratches, and other defects on various substrates with complex patterns and regions, such as those with rough edges, mixed iterative and non-iterative patterns, and varying pattern densities, in a simple and efficient manner.
Innovation Solution
An apparatus and method utilizing a stage with a laser light source that guides beams into slit-shaped beams at specific angles to inspect substrates, combining a detection optical system with an objective lens and image sensor to detect and process signals from contamination or defects, and an image processor to extract defect signals, allowing for high-speed and accurate inspection across different substrate types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional defect inspection methods are used, then the inspection process is simple, but the detection capability for very small defects (0.05 μm) is insufficient
Solution Approach 1:
The inspection system divides the substrate into multiple regions (first region with iterative patterns, second region with non-iterative patterns) and applies different inspection methods to each region. The spatial filter is configured with different light-shielding patterns for different regions, enabling precise detection of small defects while maintaining system efficiency.
Solution Approach 2:
The inspection system dynamically adjusts the spatial filter configuration based on the pattern type in each region. The light-shielding pattern of the spatial filter is changed according to whether the current region contains iterative or non-iterative patterns, optimizing detection capability for each specific area.
2Measurement precision
If the spatial filter light-shielding pattern is changed according to pattern type, then detection accuracy improves, but inspection time increases
Solution Approach 1:
The inspection system pre-configures multiple light-shielding patterns in the spatial filter corresponding to different pattern types. By preparing these patterns in advance and switching between them based on the region being inspected, the system avoids real-time pattern generation and reduces inspection time while maintaining high detection accuracy.
Solution Approach 2:
The system changes the light-shielding pattern parameter of the spatial filter according to the pattern type in each region. This parameter adjustment enables optimized detection for iterative and non-iterative patterns respectively, improving accuracy without requiring complete reconfiguration of the inspection system.
3Measurement precision
If coherent light is used for inspection, then detection sensitivity increases, but pattern scattered light interference increases
Solution Approach 1:
The spatial filter extracts and removes the zeroth-order diffracted light from iterative patterns by positioning light-shielding members to block this specific component. This separation allows the detection system to focus on scattered light from defects while eliminating the dominant background signal from regular patterns.
Solution Approach 2:
The system converts the strong scattered light from iterative patterns, which was previously a harmful interference, into a useful signal by using it to define the light-shielding pattern in the spatial filter. The regular diffraction pattern itself becomes the basis for creating the filter configuration that removes it, while preserving defect detection capability.
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 high-speed and high-accuracy inspection of small defects down to 0.05 μm in size, including particle-like and thin-film-like contamination, and scratches on substrates with complex patterns, facilitating the construction of efficient manufacturing lines as an in-line monitor.
Implementation Method 1
a laser light source that guides a flux of beams emitted from the laser light source
Implementation Method 2
detect non-repeatable contamination or other defects in edge-enhanced form
Implementation Method 3
uses an objective lens to converge reflected/scattered light obtained from contamination or defects present on the substrate
Implementation Method 4
uses an image sensor to receive the reflected/scattered light that has been converged, convert the received light into a signal, and detect the signal
Data Source
AI summary
A defect inspection apparatus and method includes utilizing an irradiation optical system that focuses a beam flux emitted from a laser light source and formed into a slit-shaped beam so as to irradiate the beam onto the surface of the substrate to be inspected, utilizing a detection optical system that detects light from the substrate that has been irradiated with the slit-shaped beam, and utilizing a signal processor that processes a signal output from the detection optical system. The irradiation optical system includes a cylindrical lens for focusing the beam that has been emitted from the laser light source onto the substrate to be inspected, as the slit-shaped beam, wherein the cylindrical lens is disposed so as to obtain a distance between an incidence surface or emitting surface thereof and the slit-shaped beam upon the substrate to be inspected to be equal to a focal distance of the cylindrical lens.