Alignment Measurement System Using Diffracted Beams
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Solution Overview
Problem
Current alignment measurement systems for substrates, such as semiconductor wafers, face challenges in accurately and precisely measuring the location of alignment marks, particularly in multi-dimensional environments, leading to inefficiencies in overlay control and position determination.
Innovation Solution
A system utilizing a laser source, two-dimensional target grating, beam splitter, and reference gratings with detectors in separate optical paths to generate and measure diffracted beams, allowing for precise alignment measurements in multiple dimensions by separating and focusing diffracted beams along different orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single optical path is used for alignment measurement, then the system structure is simple, but the measurement precision in multi-dimensional environments deteriorates
Solution Approach 1:
The optical path is segmented into multiple independent paths, with each path dedicated to measuring alignment marks in a specific dimension. This allows each optical path to be optimized for its specific dimensional measurement, improving overall measurement precision while maintaining manageable system complexity through modular design
Solution Approach 2:
The system transitions from a single optical path to multiple optical paths, adding the dimension of parallel measurement capability. This enables simultaneous measurement of alignment marks in different dimensions, resolving the contradiction by using dimensional expansion to improve precision without proportionally increasing complexity
2Measurement precision
If multiple optical paths are used for multi-dimensional alignment measurement, then the measurement precision improves, but the system complexity increases
Solution Approach 1:
Each optical path is designed as a universal module that can measure alignment marks in its designated dimension. The same basic optical components (lens, detector, grating) are reused across all paths, providing multi-functionality that reduces overall system complexity despite having multiple paths
Solution Approach 2:
The optical paths are nested within a unified system architecture, with each path containing nested optical elements (lens, grating, detector) arranged in a compact configuration. This nesting allows multiple functional paths to coexist in a space-efficient manner, improving precision without linearly increasing complexity
3Measurement precision
If alignment marks are measured in multi-dimensional environments, then the accuracy of position determination improves, but the sensitivity to lens aberrations increases
Solution Approach 1:
The measurement system is segmented into separate optical paths for different dimensions, allowing each path to be optimized for its specific dimensional requirements. This segmentation isolates lens aberration effects to individual paths, reducing the overall sensitivity to aberrations while maintaining multi-dimensional measurement accuracy
Solution Approach 2:
Each optical path is designed with local optimization for its specific dimension, using appropriately sized and positioned optical elements tailored to that dimension's measurement requirements. This local quality approach reduces aberration sensitivity by avoiding the use of overly complex optical systems for simple one-dimensional measurements
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 precise measurement of alignment marks on substrates, improving overlay control and position determination by simplifying alignment and reducing sensitivity to lens aberrations, while allowing for a more compact design.
Implementation Method 1
A laser source generates an incident laser beam which is directed to a two-dimensional target grating on a target substrate such that multiple diffracted beams are created
Implementation Method 2
A beam splitter transmits a first plurality of the multiple diffracted beams onto a first optical path and directs a second plurality of the multiple diffracted beams onto a second optical path
Implementation Method 3
The first plurality of the multiple diffracted beams is focused onto a first reference grating which generates a first diffraction, and the second plurality of the multiple diffracted beams is focused onto a second reference grating which generates a second diffraction
Data Source
AI summary
One embodiment relates to an apparatus for alignment measurement. A laser source generates an incident laser beam which is directed to a two-dimensional target grating on a target substrate such that multiple diffracted beams are created. A beam splitter transmits a first plurality of the multiple diffracted beams onto a first optical path and directs a second plurality of the multiple diffracted beams onto a second optical path. Each of the two optical paths includes a reference grating and a detector. Another embodiment relates to a method of measuring alignment of a target substrate. Other embodiments, aspects and features are also disclosed.