Pattern Inspection Using Dual Reference Images to Reduce False Defects
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Solution Overview
Problem
Current pattern inspection apparatuses inaccurately detect defects in mask and semiconductor substrates due to the inclusion of auxiliary patterns, leading to false positives when comparing reference images with high precision, as they either miss necessary deviations or flag non-defective features as defects.
Innovation Solution
A pattern inspection apparatus and method that acquire measured images using electron beams or laser beams, storing both design patterns with and without auxiliary patterns, and comparing these images to determine defects by using one as a main reference and the other as a sub-reference, adjusting determination thresholds and image processing to differentiate between actual defects and non-defective features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inspection is performed based on design pattern including auxiliary patterns with high precision comparison, then measurement precision is improved, but false defect detection increases
Solution Approach 1:
The patent segments the design pattern into two distinct datasets: one including auxiliary patterns and another excluding them. This segmentation allows the inspection system to compare measured images against both references, thereby distinguishing between actual defects and acceptable variations caused by auxiliary patterns, thus reducing false defect detection while maintaining high measurement precision
Solution Approach 2:
The patent changes the inspection parameter by introducing dual-reference comparison instead of single-reference comparison. By evaluating measured images against both a reference including auxiliary patterns and a reference excluding them, the system dynamically adjusts defect determination criteria, reducing false positives while preserving accurate defect detection
2Reliability
If inspection is performed based on original design pattern without auxiliary patterns, then false defect detection is reduced, but actual defects in auxiliary pattern regions are missed
Solution Approach 1:
The patent segments the inspection process into two parallel comparison paths: one using a reference pattern including auxiliary patterns and another using a reference pattern excluding them. This dual-segmented approach ensures that both actual defects and auxiliary pattern variations are accounted for, preventing missed defects while controlling false positives
Solution Approach 2:
The patent merges the results from two separate comparison processes (one against reference with auxiliary patterns, another against reference without them). By combining these comparison outcomes, the system achieves comprehensive defect detection that captures both actual defects and acceptable auxiliary pattern variations, thereby improving overall measurement precision without increasing false defect rates
3Device complexity
If single reference image is used for comparison, then device complexity is reduced, but inspection accuracy deteriorates
Solution Approach 1:
The patent implements a universal inspection framework that processes multiple reference patterns through a single comparison mechanism. The same image acquisition and comparison hardware is used to evaluate against both reference types (with and without auxiliary patterns), achieving multi-functional inspection capability without proportionally increasing device complexity
Solution Approach 2:
The patent creates a virtual copy of the design pattern dataset, dividing it into two reference versions. This copying approach allows the inspection system to utilize both reference types without duplicating physical inspection hardware, thereby maintaining relatively low device complexity while improving measurement precision through dual-reference comparison
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 reduces the detection of non-defective features as defects, allowing for more accurate inspection and utilization of substrates by precisely distinguishing between necessary deviations and actual defects, enhancing the reliability of pattern inspection.
Implementation Method 1
irradiating a substrate with a single electron beam or multi-beams composed of a plurality of electron beams in order to detect a secondary electron, corresponding to each beam, emitted from the substrate
Implementation Method 2
irradiating a pattern on the substrate with a laser beam in order to capture its transmission image or reflection image
Data Source
AI summary
A pattern inspection apparatus includes a design pattern image generation circuit to generate a first design pattern image by developing an image of the first design pattern, and a second design pattern image by developing an image of the second design pattern for assisting the first design pattern, a comparison circuit to detect a defect candidate by comparing, for each pixel, the measured image with a main reference image which is a predetermined one of the first design pattern image and the second design pattern image, and a determination circuit to determine whether the defect candidate is a defect by using determination conditions obtained using, as a sub reference image, another predetermined one of the first design pattern image and the second design pattern image.