Angled Level Sensor Strokes for Substrate Topology Detection
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Solution Overview
Problem
Existing level sensing technologies in lithographic apparatuses have limited resolution, missing significant topological features on substrates, which can lead to errors in substrate positioning and pattern projection.
Innovation Solution
The implementation of a level sensor with measurement spots angled at less than 20 degrees relative to the scanning exposure direction, allowing for more reliable detection of deep scribe lines and topological features parallel to the scanning exposure direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If level sensing is performed using measurement spots scanning parallel to the scanning exposure direction, then the measurement process is simple and fast, but significant topological features (such as deep scribe lines) parallel to the scanning exposure direction are missed due to limited resolution
Solution Approach 1:
The patent introduces a new dimensional parameter - the angle between the stroke direction and scanning exposure direction. By changing the stroke direction from parallel (0 degrees) to angled (less than 20 degrees), the measurement system gains the ability to detect topological features that were previously invisible, effectively adding a new dimension to the measurement approach
Solution Approach 2:
The patent changes the angular parameter of the measurement stroke from 0 degrees (parallel to scanning exposure direction) to less than 20 degrees. This parameter change transforms the measurement geometry to enable detection of deep scribe lines and other topological features while maintaining measurement efficiency
2Productivity
If measurement spots are spaced further apart to cover the substrate faster, then the measurement duration is reduced for mass production, but the resolution of the height map decreases and more features are missed
Solution Approach 1:
By introducing an angular dimension to the measurement strokes, the system achieves better feature detection without requiring denser spot spacing. The angled strokes cause measurement spots to cross over topological features rather than run parallel to them, maintaining resolution while preserving measurement speed
3Measurement precision
If the level sensor scans with high resolution in all directions, then all topological features are detected accurately, but the measurement duration becomes too long for mass-production semiconductor manufacturing
Solution Approach 1:
The patent optimizes the angular parameter of measurement strokes to less than 20 degrees relative to the scanning exposure direction. This specific angular range provides the optimal balance between detecting topological features and maintaining measurement speed suitable for mass production, avoiding the need for exhaustive multi-directional scanning
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 resolution of the height map, ensuring that all significant topological features are detected, thereby improving the accuracy of substrate positioning and pattern projection in lithographic processes.
Implementation Method 1
The level sensor may make use of an optical measurement, by means of projecting a measurement beam onto the substrate and detecting a reflection thereof
Data Source
AI summary
A lithographic apparatus is disclosed. The lithographic apparatus comprises a substrate table configured to support a substrate; actuators configurable to move the substrate table in a plane substantially parallel to the surface of the substrate; a projection system configured to pattern the substrate with fields aligned in a scanning exposure direction; a level sensor configured to sense a height of the substrate using a plurality of measurement spots; and a controller configured to control the actuators to generate strokes of relative movement between the substrate and the level sensor for mapping the height of the substrate, said strokes being at an angle of less than 20 degrees relative to the scanning exposure direction. Also disclosed is an associated method of mapping the height of a substrate.