Lithography Sensor Wavefront Correction for Position Precision
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Solution Overview
Problem
Current sensor apparatuses in lithographic systems face challenges in accurately determining the position of targets on substrates due to errors from deformation, substrate structure, focus issues, and optical aberrations, which affect the precision of feature placement and alignment in semiconductor manufacturing.
Innovation Solution
A sensor apparatus equipped with projection and collection optics, a wavefront sensing system, and a measurement system that determines pupil function variations to correct for errors by analyzing phase and intensity changes in measurement radiation, enabling continuous monitoring and correction of optical aberrations and identifying contributing optical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional position measurement systems are used in lithographic apparatus, then alignment marks can be measured, but measurement precision deteriorates due to errors from target deformation, substrate structure, focus errors, and optical aberrations
Solution Approach 1:
The system employs a wavefront sensing system that provides feedback signals about optical aberrations and measurement conditions. The processor uses this feedback to dynamically adjust and correct position measurements, compensating for errors caused by target deformation, substrate structure, focus errors, and optical aberrations in real-time.
Solution Approach 2:
A wavefront sensing system acts as an intermediary between the measurement radiation and the position determination process. It separately measures pupil function variations caused by optical aberrations and provides correction data, allowing the main measurement system to achieve higher precision without directly being affected by these errors.
2Manufacturing precision
If alignment measurements are made before each process layer formation, then accurate feature placement can be achieved, but productivity decreases due to repeated measurements for each layer
Solution Approach 1:
The system performs preliminary characterization of optical aberrations and substrate properties during initial measurements. This preliminary data is stored and reused for subsequent layers, eliminating the need to repeat full characterization measurements for each layer while maintaining placement accuracy.
Solution Approach 2:
The measurement system is designed to serve multiple functions: it performs both initial comprehensive characterization and subsequent routine alignment measurements. The same apparatus can handle different measurement modes (full characterization vs. quick alignment checks), increasing versatility and reducing total measurement time across multiple layers.
3Measurement precision
If wavefront sensing system is added to measure pupil function variations, then measurement precision improves through error correction, but device complexity increases
Solution Approach 1:
The wavefront sensing system is integrated with the existing measurement optics, combining multiple measurement functions into a unified system. The same optical path is used for both primary position measurement and wavefront sensing, reducing the number of separate components and simplifying the overall system architecture.
Solution Approach 2:
The system uses a portion of the measurement radiation itself to perform wavefront sensing, rather than requiring separate illumination sources. The measurement radiation that would otherwise be partially unused or discarded is redirected through the wavefront sensing system, allowing the system to self-characterize its optical conditions without external assistance.
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 enhances the accuracy of target position determination, reduces measurement errors, and allows for continuous correction of optical aberrations, thereby improving the precision of feature placement and alignment in lithographic processes.
Implementation Method 1
collection optics configured to collect measurement radiation that has scattered from the target
Data Source
AI summary
A sensor apparatus (300) for determining a position of a target (330) of a substrate (W) comprising, projection optics (315;321) configured to project a radiation beam (310) onto the substrate, collection optics (321) configured to collect measurement radiation (325) that has scattered from the target, a wavefront sensing system (335) configured to determine a pupil function variation of at least a portion (355) of the measurement radiation and output a signal (340) indicative thereof, and a measurement system (350) configured to receive the signal and to determine the position of the target in at least partial dependence on the collected measurement radiation and the determined pupil function variation of at least a portion of the measurement radiation.