Patterning Device Alignment with Multi-Position Optical Measurements
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Solution Overview
Problem
Existing alignment methods in lithographic apparatuses using moveable optical components are inaccurate, leading to overlay errors during patterning due to inaccuracy in position measurement systems.
Innovation Solution
Perform multiple alignment measurements with moveable optical components in predetermined positions and combine these measurements to mitigate position errors, specifically addressing cyclic errors in interferometer-based systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If moveable optical components are used in the projection system, then the lithographic apparatus can perform patterning operations, but alignment accuracy deteriorates due to position measurement errors
Solution Approach 1:
The system performs preliminary alignment measurements at multiple predetermined positions of the moveable optical components before the actual patterning operation. By pre-characterizing the position-dependent measurement errors at different locations, the system can later compensate for these errors during patterning, thus resolving the contradiction between using moveable components and maintaining alignment accuracy
Solution Approach 2:
The system varies the position parameter of the moveable optical components to multiple predetermined positions and performs alignment measurements at each position. By changing the positional parameter and collecting multiple measurements, the system can identify and compensate for position-dependent errors, thereby maintaining alignment accuracy despite the use of moveable components
2Device complexity
If single alignment measurement is performed with fixed optical components, then measurement process is simple, but alignment accuracy deteriorates when components need to be moved during patterning
Solution Approach 1:
The system performs preliminary alignment measurements at multiple predetermined positions before actual patterning. This preliminary characterization of position-dependent errors adds some complexity to the alignment process, but it significantly improves the reliability of alignment during subsequent patterning operations when components are moved
Solution Approach 2:
The system uses the results from multiple alignment measurements at different positions to generate compensation data that is applied during patterning. This feedback mechanism allows the system to account for position-dependent measurement errors, improving alignment reliability while maintaining a manageable process complexity
Data Source
AI summary
A method of spatially aligning a patterning device and a substrate, wherein the patterning device and the substrate are separated by an optical path comprising one or more moveable optical components is described, the method comprising: —performing a plurality of alignment measurements, wherein for each alignment measurement the moveable optical components are arranged in respective predetermined positions, —combining the alignment measurements, and—spatially aligning the patterning device and the substrate based on the combination of the alignment measurements.