Substrate Surface Inspection Using Electron Beam Contrast
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Solution Overview
Problem
Conventional substrate surface inspection methods using light struggle to detect foreign materials smaller than 50 nm and often misidentify patterns as defects due to interference from background patterns, especially when dealing with irregular patterns.
Innovation Solution
A substrate surface inspection method and apparatus that uses an electron beam with a landing energy adjusted to create a contrast between materials, allowing for the elimination or weakening of surface patterns, enabling clear distinction between defects and background images, thereby facilitating precise detection of foreign materials as small as 50 nm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is used for foreign material inspection, then the inspection method is simple and fast, but the detection limit is about 50 nm and cannot detect smaller foreign materials
Solution Approach 1:
The patent replaces the optical inspection system with an electron beam inspection system. The electron beam has much higher resolution capability than light, enabling detection of foreign materials smaller than 50 nm. The electron beam interacts with the sample to generate signals that can be detected and processed to identify defects, overcoming the wavelength limitation of optical methods.
Solution Approach 2:
The patent changes the fundamental inspection parameter from optical wavelength to electron beam energy. By adjusting the electron beam energy and detection parameters, the system achieves superior resolution for detecting sub-50 nm foreign materials while maintaining inspection functionality.
2Productivity
If cell comparison inspection is used, then inspection speed is improved, but background patterns are misidentified as defects
Solution Approach 1:
The patent extracts and removes the background pattern information from the inspection image through image processing. By separating the background pattern signals from the defect signals, the system eliminates false positives while maintaining the ability to detect actual defects. This allows cell comparison inspection to proceed at high speed without misidentifying background patterns as defects.
Solution Approach 2:
The patent introduces an image processing intermediary that acts as a filter between the raw inspection data and the defect detection algorithm. This intermediary process removes background pattern interference, allowing the cell comparison method to accurately distinguish between actual defects and background variations, thereby improving both speed and accuracy.
3Measurement precision
If die comparison inspection is used, then pattern defects can be inspected, but the apparatus becomes expensive and inspection time increases
Solution Approach 1:
The patent segments the inspection process into two independent stages: first, acquire images at multiple cell pitches; second, process and compare these images. This segmentation allows the system to use simpler, less expensive apparatus by breaking down the complex die comparison task into manageable cell-level operations, reducing the requirements for stage positioning accuracy and control mechanisms.
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 easy and precise detection of defects, including foreign materials, by isolating them from the background, improving inspection accuracy and reducing false positives, especially in cases with irregular patterns.
Implementation Method 1
irradiating the surface of the substrate with an electron beam
Implementation Method 2
detecting electrons generated by the substrate
Data Source
AI summary
A substrate surface inspection method inspects for a defect on a substrate including a plurality of materials on a surface thereof. The inspection method comprises: irradiating the surface of the substrate with an electron beam, a landing energy of the electron beam set such that a contrast between at least two types of materials of the plurality of materials is within a predetermined range; detecting electrons generated by the substrate to acquire a surface image of the substrate, with a pattern formed thereon from the at least two types of materials eliminated or weakened; and detecting the defect from the acquired surface image by detecting as the defect an object image having a contrast by which the object image can be distinguished from a background image in the surface image. Defects present on the substrate surface can be detected easily and precisely by using a cell inspection.