Lithographic Image Sensor for Overlay Error Reduction
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Solution Overview
Problem
Current lithographic apparatuses face challenges in achieving precise overlay and focus accuracy due to deformations caused by critical device structures following different transmission paths, leading to increased overlay and focus errors as patterns become smaller and more complex.
Innovation Solution
The implementation of a lithographic apparatus with advanced image sensors that measure the position of aerial images and aberrations, using multiple fiducial parts and lenses with high numerical aperture, and an amplification device to enhance imaging performance, allowing for precise alignment and optimization of illumination settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If critical device structures are used to create higher component densities, then productivity is improved, but manufacturing precision deteriorates due to overlay and focus errors from different transmission paths
Solution Approach 1:
The patent applies preliminary action by measuring the aerial image position and aberrations before actual pattern transfer using dedicated mark patterns. This allows the system to predict and compensate for transmission path deformations that will affect critical device structures, thereby maintaining overlay accuracy while producing high-density patterns.
Solution Approach 2:
The patent implements feedback by using sensors to detect the actual aerial image position and aberration characteristics, then feeding this information back to adjust illumination settings and alignment parameters. This closed-loop control compensates for transmission path variations, maintaining precision despite increased component density.
2Measurement precision
If sensors measure mark pattern position to evaluate imaging performance, then measurement precision is improved, but reliability deteriorates because critical device structures follow different transmission paths than mark patterns
Solution Approach 1:
The patent applies local quality by designing mark patterns with specific local characteristics that match the transmission path of critical device structures. Rather than using generic mark patterns, the system uses marks that experience the same optical conditions as the actual device features, making measurements locally representative and reliable for predicting overlay errors.
Solution Approach 2:
The patent uses parameter changes by varying illumination settings and measuring how the aerial image responds to these changes. By measuring at multiple illumination conditions, the system extracts more reliable information about transmission path characteristics that applies to critical device structures, improving the reliability of overlay error predictions.
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 solution enables improved accuracy in substrate positioning relative to the mask pattern, reduces overlay errors, and optimizes illumination settings, enhancing the precision of pattern transfer and reducing aberrations, thereby improving the yield of correctly manufactured devices.
Implementation Method 1
A TIS is a sensor that is used to measure at substrate level the position of a projected aerial image of a mark pattern at mask (reticle) level. The TIS measures aforementioned mark pattern using a transmission pattern with a photocell underneath it.
Implementation Method 2
a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies) of the substrate W
Data Source
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AI summary
The invention relates to an image for detection of an aerial pattern comprising spatial differences in radiation intensity in a cross section of a beam of radiation in a lithographic apparatus for exposing a substrate. The image sensor comprises a lens (5) arranged to form a detection image of the aerial pattern and an image detector (6) arranged to measure radiation intensities in a plurality, of positions in the detection image.