Wafer Mark Detection During Stage Movement
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Solution Overview
Problem
The lithography process for manufacturing microdevices faces a decrease in throughput due to the time-consuming alignment operation required for precise positional alignment between patterns on a wafer and a reticle, especially when the number of sample shots increases, which is exacerbated by the need for separate measurement stages in conventional systems.
Innovation Solution
A method and apparatus where the mark detection system moves in conjunction with the object, allowing for simultaneous pattern formation and detection, reducing the time required for mark detection and improving overall process throughput by performing detection during object movement and using detection results in parallel with pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment operation is performed prior to exposure with increased number of sample shots, then measurement precision is improved, but productivity deteriorates due to increased measurement time
Solution Approach 1:
The mark detection system performs preliminary detection of alignment marks during the wafer movement phase (from loading position to exposure position) before the actual exposure operation begins. This preliminary action allows alignment data to be collected in advance, enabling the exposure process to proceed without waiting for separate alignment measurements, thus improving throughput while maintaining alignment precision.
2Productivity
If twin stage system is used to perform parallel processing, then productivity is improved, but device complexity and cost increase
Solution Approach 1:
The mark detection system is designed to perform multiple functions: it detects alignment marks during wafer movement, provides alignment data for the exposure process, and can operate independently of the exposure optics. This multi-functionality allows a single system to achieve what would traditionally require separate alignment and exposure stages, improving throughput without requiring a twin stage configuration.
Solution Approach 2:
The mark detection system utilizes the existing wafer movement mechanism and optical path to perform alignment detection during the normal exposure workflow. Instead of requiring separate dedicated alignment stages or additional complex hardware, the system makes the existing components serve dual purposes - the wafer stage movement that is necessary for exposure also enables the mark detection process, achieving self-service functionality.
Data Source
AI summary
A plurality of wafer marks on a wafer is detected while a wafer stage moves from a loading position where a wafer is delivered onto the wafer stage to an exposure starting position where exposure of a wafer begins, with a part of an alignment system also moving, using the alignment system. Accordingly, the time required for mark detection can be reduced, therefore, it becomes possible to increase the throughput of the entire exposure process.