Configurable Detection Spot for Lithographic Alignment Sensors
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Solution Overview
Problem
Lithographic alignment sensors face challenges in accurately aligning substrates with complex patterns and varying mark sizes due to limitations in detection spot size and light scattering, which requires additional complexity and wavelengths, making it difficult to maintain reliable position information without increasing the system's footprint.
Innovation Solution
A detection system using selectively switchable optical fiber cores to define a configurable detection spot, allowing for adjustable detection area based on the size of alignment marks, with a dynamic field stop mechanism that does not require moving parts, enabling alignment on both small and large marks without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional wavelengths and polarizations are added to the alignment sensor to handle complex substrate patterns, then the reliability of position information is improved, but the device complexity increases
Solution Approach 1:
The alignment sensor is designed to handle multiple wavelengths and polarizations through a single integrated detection system. The detection circuit can process signals from different wavelengths (e.g., 193nm, 248nm) and polarizations using the same optical fiber core and detector infrastructure, eliminating the need for separate detection paths for each wavelength/polarization combination.
Solution Approach 2:
The system dynamically adjusts detection parameters such as wavelength selection and polarization sensitivity based on the specific measurement requirements. The detection circuit can switch between different operational modes to optimize performance for different substrate patterns and alignment mark types without requiring physical reconfiguration of the optical path.
2Ease of operation
If the detection spot size is increased to improve alignment on larger footprint marks, then the ease of operation is improved, but the measurement precision deteriorates due to detecting light from surrounding structures
Solution Approach 1:
The detection spot size is made dynamically adjustable rather than fixed. The system can adapt the detection spot dimensions based on the alignment mark footprint size and the specific alignment task at hand. This allows optimal detection spot sizing for each measurement scenario, balancing between capturing sufficient light from the mark and rejecting light from surrounding structures.
Solution Approach 2:
The detection system applies different detection characteristics to different spatial regions. By selectively activating portions of the detection spot or using spatially resolved detection, the system can optimize the detection area for each specific alignment mark while maintaining rejection of out-of-region light, effectively tailoring the detection quality to local requirements.
3Measurement precision
If a small detection spot is used for small footprint alignment marks, then the measurement precision is improved, but the ease of operation worsens due to reduced light collection from surrounding structures
Solution Approach 1:
The detection spot size is dynamically adapted to match the alignment mark footprint. For small footprint marks, the system automatically reduces the detection spot size to maintain measurement precision, while for larger marks, it expands the detection spot to improve signal collection. This dynamic adjustment maintains ease of operation across different mark sizes without sacrificing precision.
4Productivity
If more patterns are added to the substrate to increase complexity, then the productivity is improved, but the measurement precision deteriorates due to reduced light scattered by alignment marks
Solution Approach 1:
The system replaces reliance on mechanical/optical adjustments with electronic control of the detection parameters. By using electronic switching between different wavelengths, polarizations, and detection spot configurations, the system can compensate for reduced light scattering from alignment marks on complex substrates without requiring physical modifications to the optical path or additional mechanical components.
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 allows for precise alignment on various mark sizes with minimal system modifications, improving alignment accuracy and compatibility with existing sensors while maintaining efficient use of light and reducing complexity, thus enhancing the lithographic process.
Implementation Method 1
a plurality of optical fiber cores for transporting a measurement signal to the at least one detection circuit
Data Source
AI summary
A detection system for an alignment sensor, and an alignment sensor and lithographic projection apparatus comprising such a detection system is disclosed. The detection system comprises at least one detection circuit; and a plurality of optical fiber cores for transporting a measurement signal to the at least one detection circuit. At least as subset of the plurality of optical fiber cores are selectively switchable between a detection state and a non-detection state, thereby defining a configurable detection spot.