Lithographic Substrate Alignment Using Window Positioning Feedback
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Solution Overview
Problem
Current lithographic apparatuses face challenges in achieving high accuracy and throughput during substrate alignment due to limited dynamic range of measurement systems and variations in alignment methods across different equipment from different vendors, leading to increased tolerance and error in positioning alignment marks.
Innovation Solution
A method that determines the position of a window on a substrate based on geometric references, measures the alignment mark within this window, calculates and stores the relationship between the mark and window positions, and adjusts the window position for subsequent alignments using stored data to improve alignment accuracy and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the window size is increased to accommodate alignment mark position fluctuations, then the measurement system can handle larger tolerances, but the alignment accuracy decreases
Solution Approach 1:
The patent performs preliminary alignment using the wafer edge to define a window, then uses this window to locate alignment marks. This preliminary action establishes a search area that balances tolerance accommodation with measurement precision.
Solution Approach 2:
The patent measures the position of alignment marks within the window and uses this measurement feedback to refine the alignment. The measured position information is fed back to adjust the window position and improve subsequent alignment accuracy.
2Manufacturing precision
If high accuracy position measurement of alignment marks is implemented, then alignment precision improves, but the complexity and cost of the measurement system increases
Solution Approach 1:
The patent divides the alignment process into two segments: first determining the window position based on wafer edge geometric references, then measuring the alignment mark position within that window. This segmentation allows each measurement stage to be optimized independently.
Solution Approach 2:
The patent adds a spatial dimension to the measurement approach by defining a window area rather than attempting to measure the alignment mark position directly across the entire substrate. This dimensional approach reduces measurement system requirements.
3Manufacturing precision
If multiple alignment marks are used to improve alignment accuracy, then positioning precision increases, but the alignment process time increases
Solution Approach 1:
The patent performs preliminary window positioning using wafer edge references before measuring alignment marks. This preliminary action reduces the search space, allowing faster measurement of multiple alignment marks without proportionally increasing total alignment time.
Data Source
AI summary
A method for aligning a substrate in a lithographic apparatus includes determining from a geometric reference of the substrate a position of a window on the substrate. The window indicates an area in which an alignment mark of the substrate may be expected. Then, a position of the alignment mark is measured in the window. A relationship between the measured position of the alignment mark and the position of the window is determined. The relationship is stored in a database and the substrate is aligned making use of the measured position of the alignment mark.The above may be repeated for a following aligning of the substrate, prior however to the measuring of the position of the alignment mark in the window, the position of the window is amended making use of the relationship between the measured position of the alignment mark and the position of the window as stored in the database for one or more preceding alignings.