On-Chip Wafer Alignment Sensor for Fine Grating Distortion Measurement
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Solution Overview
Problem
Existing alignment systems in lithographic apparatuses are unable to accurately measure intra-field distortions and do not support finer alignment grating pitches, and are generally bulky and inefficient.
Innovation Solution
A compact sensor apparatus with an illumination system, detector system, and processor that generates a fringe pattern on a diffraction target using coherent off-axis illumination beams, allowing for precise measurement of alignment positions and intra-field distortions through adjustable optics and variable phase modulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing alignment systems are used, then alignment measurement is possible, but measurement precision for intra-field distortion is insufficient
Solution Approach 1:
The alignment mark is divided into multiple segments (first alignment mark portion and second alignment mark portion) with different orientations. This segmentation enables the measurement system to capture distortion information from multiple directions, significantly improving intra-field distortion measurement precision while maintaining alignment accuracy through the combined information from all segments.
Solution Approach 2:
The system changes the orientation parameter of alignment mark segments to create first and second alignment mark portions at different angles. This parameter variation allows the measurement of distortion in multiple directions, enhancing both the precision of intra-field distortion measurement and the reliability of overall alignment accuracy.
2Adaptability or versatility
If existing alignment systems are used, then alignment measurement is possible, but support for finer alignment grating pitches is limited
Solution Approach 1:
The illumination system is designed to dynamically adjust illumination angles to illuminate different segments of the alignment mark at different angles. This dynamic illumination approach enables the system to adapt to various grating pitches, from coarse to fine, while maintaining high measurement precision through optimized illumination geometry for each pitch size.
Solution Approach 2:
The alignment measurement system is designed with multi-functional capability to handle different grating pitch sizes. By using multiple alignment mark portions with different orientations and dynamic illumination angles, the system can universally measure both coarse and fine gratings, enhancing adaptability while preserving measurement precision across all pitch ranges.
3Area of stationary object
If compact sensor apparatus is implemented, then footprint is reduced, but device complexity increases
Solution Approach 1:
The illumination system combines multiple illumination paths and alignment mark portions into a single integrated measurement process. By merging the functionality of multiple separate measurement systems into one compact apparatus that uses segmented alignment marks and dynamic illumination, the system reduces overall footprint while managing complexity through functional integration.
Solution Approach 2:
The system transitions from a single-plane measurement approach to a multi-dimensional approach by introducing alignment mark portions at different orientations and illumination from different angles. This dimensional expansion allows compact packaging of measurement functionality while the structured complexity of multi-angle illumination and segmented marks provides the needed measurement capabilities without requiring proportionally larger device complexity.
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
Enables accurate and efficient measurement of alignment positions and intra-field distortions with a reduced footprint, improving alignment accuracy and scalability in lithographic processes.
Implementation Method 1
The transmitting generates a fringe pattern on the diffraction target
Implementation Method 2
A signal beam includes diffraction order sub-beams that are diffracted by the diffraction target
Data Source
AI summary
A sensor apparatus includes an illumination system, a detector system, and a processor. The illumination system is configured to transmit an illumination beam along an illumination path and includes an adjustable optic. The adjustable optic is configured to transmit the illumination beam toward a diffraction target on a substrate that is disposed adjacent to the illumination system. The transmitting generates a fringe pattern on the diffraction target. A signal beam includes diffraction order subbeams that are diffracted by the diffraction target. The detector system is configured to collect the signal beam. The processor is configured to measure a characteristic of the diffraction target based on the signal beam. The adjustable optic is configured to adjust an angle of incidence of the illumination beam on the diffraction target to adjust a periodicity of the fringe pattern to match a periodicity of the diffraction target.