Run-time Defect Location Correction Using Local Reference Sites
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Solution Overview
Problem
Prior automated inspection and review systems for semiconductors face positioning errors due to thermal effects and spatial variations in the stage, leading to inaccuracies in defect re-location, especially for fields of view less than one micron.
Innovation Solution
The method involves grouping defect locations by proximity to alignment marks, determining a local reference site for each group, and using this site to calculate a positional offset, enabling run-time correction of defects with submicron precision and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a coordinate transformation is established between the review microscope and defect location coordinates, then defect locations can be re-located for detailed viewing, but positioning errors occur due to thermal effects and spatial variations in the stage
Solution Approach 1:
The patent introduces alignment marks as intermediary reference objects between the inspection system and review microscope. These marks serve as mediators to establish accurate coordinate transformations, compensating for thermal effects and stage variations. The alignment marks provide stable reference points that enable precise defect re-location despite environmental changes during the review process.
2Ease of operation
If the substrate is aligned on the stage of the review microscope, then coordinate transformation can be established, but thermal effects cause positional drift during review
Solution Approach 1:
The patent performs preliminary alignment of the substrate using alignment marks before the actual defect review process. This preliminary action establishes the initial coordinate transformation and positions the substrate correctly. By completing the alignment operation beforehand, the system can then focus on maintaining precision during the review without repeated alignment disturbances.
Solution Approach 2:
The patent implements a feedback mechanism where the review microscope continuously monitors the positions of alignment marks during the review process. This feedback information is used to detect and compensate for thermal drift and stage variations in real-time, maintaining positioning accuracy throughout the review even as environmental conditions change.
3Measurement precision
If high-magnification scanning electron microscope is used for detailed viewing, then defect analysis capability is improved, but field of view is reduced making re-location more difficult
Solution Approach 1:
The patent segments the review process into multiple stages with different magnifications. First, alignment marks are located at low magnification to establish the coordinate system. Then, defect locations are calculated based on the transformation and re-located using the alignment marks as references. This segmentation allows the system to benefit from both wide field of view for alignment and high magnification for detailed defect viewing.
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 effectively corrects positioning errors caused by thermal expansion and spatial variations, ensuring precise re-location of defects during review, even in small fields of view, with improved accuracy and efficiency.
Implementation Method 1
electron beam (e-beam) based systems
Implementation Method 2
electron lenses configured to focus the electron beam onto a surface of a substrate being reviewed
Implementation Method 3
deflectors configured to scan the electron beam over a field of view
Implementation Method 4
a detector configured to detect electrons from the substrate
Data Source
AI summary
One embodiment relates to a method for run-time correction of defect locations on a substrate during defect review. The substrate is loaded into a stage of a review apparatus, and coordinates for the defect locations on the substrate is received. The defect locations are grouped, and at least one local reference site in proximity to each group of defect locations is determined. The local reference site(s) is (are) used to determine a positional offset for the defect locations in each group. Another embodiment relates to an apparatus for reviewing defect locations on a substrate which provides for run-time correction of the defect locations. Other embodiments and features are also disclosed.