Lithographic Substrate Edge Detection via Scattered Light
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Solution Overview
Problem
Lithographic apparatuses face challenges in accurately aligning complex substrates with increasing patterns, as existing alignment sensors require additional wavelengths and polarizations, leading to increased complexity and reduced production speed due to the need for additional processing steps to enhance visibility of alignment marks.
Innovation Solution
A method and apparatus that utilize a substrate table and optical system to determine the location of a substrate's edge and notch, allowing for alignment without additional processing steps by detecting light scattered by the edge, thereby improving visibility of alignment marks without requiring additional patterns or layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional wavelengths and polarizations are added to the alignment sensor, then the ability to measure position on complex substrates is improved, but the device complexity increases
Solution Approach 1:
The patent applies preliminary action by forming alignment marks with specific geometric features (edges and notches) during the substrate preparation phase. These marks are designed in advance to be detectable by the existing alignment sensor using standard wavelengths and polarizations, eliminating the need to add complex measurement capabilities later. The alignment marks are created with features that inherently provide measurable contrast against the substrate background.
Solution Approach 2:
The patent applies local quality by creating alignment marks with specific local geometric characteristics (edges and notches) that are optimized for detection. Rather than modifying the entire alignment sensor system, the solution focuses on creating locally distinct features on the substrate that provide the necessary measurement contrast. The alignment marks are designed with specific shapes and orientations that enhance their detectability by the existing sensor system.
2Illumination intensity
If additional patterns are applied to enhance alignment mark visibility, then the visibility of alignment marks is improved, but the production speed decreases due to additional processing steps
Solution Approach 1:
The patent applies preliminary action by incorporating alignment marks with detectable geometric features into the substrate during the initial preparation phase, before the main patterning process. This ensures that the alignment marks are already in place and visible to the alignment sensor when needed, eliminating the need for additional post-processing steps to enhance their visibility. The alignment marks are formed as part of the substrate preparation workflow.
Solution Approach 2:
The patent applies the taking out principle by extracting the alignment mark formation from the main patterning process. Instead of adding alignment enhancement patterns during the lithographic process, the alignment marks are prepared separately in advance. This separation allows the main patterning process to proceed at full speed without interruption for alignment mark enhancement, as the marks are already ready for detection.
3Measurement precision
If additional patterns are applied to align with the substrate, then the alignment capability is improved, but the time required for alignment increases
Solution Approach 1:
The patent applies preliminary action by pre-forming alignment marks with optimized geometric features during substrate preparation. These marks are designed to be immediately detectable and measurable by the alignment sensor, eliminating the need for time-consuming additional alignment procedures. The alignment marks are ready for use from the start of the lithographic process.
Solution Approach 2:
The patent applies self-service by designing alignment marks that are self-sufficient for the alignment measurement function. The geometric features (edges and notches) are inherently detectable by the existing alignment sensor system without requiring additional patterns or enhancement steps. The alignment marks serve their own alignment function directly, without needing external assistance from additional processing steps.
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 enhances the visibility of alignment marks, reducing the complexity and time required for alignment, thus increasing production speed and efficiency in lithographic processes.
Implementation Method 1
detecting light scattered by the edge
Data Source
AI summary
A lithographic apparatus has a substrate table on which a substrate is positioned, and an alignment sensor used to measure the alignment of the substrate. In an exemplary processing method, the alignment sensor is used to perform one or more edge measurements in a first step. In a second step, one or more edge measurements are performed on the notch of the substrate. The edge measurements are then used to align the substrate in the lithographic apparatus. In a particular example, the substrate is arranged relative to the alignment sensor such that a portion of the edge surface is positioned at the focal length of the lens. When the alignment sensor detects radiation scattered by the edge surface at the focal length of the lens, the presence of the edge of the substrate is detected.