Lithographic Apparatus Alignment Inspection During Exposure
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Solution Overview
Problem
Conventional lithographic apparatuses face challenges in achieving high overlay accuracy without significant reductions in throughput, particularly as critical feature sizes diminish and alignment requirements increase, leading to increased time for locating and inspecting alignment marks.
Innovation Solution
A lithographic apparatus and method that involves a projection system, a detector for inspecting the substrate while it is moved, and a substrate table for precise positioning, allowing for exposure adjustments based on real-time inspection data to improve overlay accuracy without compromising throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If alignment marks are inspected before exposure to determine substrate position, then overlay accuracy is improved, but processing time increases and throughput decreases
Solution Approach 1:
The patent merges the alignment inspection function with the exposure process by positioning the detector within the exposure path. The detector inspects alignment marks on the substrate while the radiation beam is being prepared for or is undergoing exposure, combining what were previously separate sequential operations into a integrated simultaneous process. This eliminates the need for separate pre-exposure inspection steps, thereby maintaining overlay accuracy while improving throughput.
2Adaptability or versatility
If critical feature size is reduced, then device complexity and functionality are improved, but alignment requirements increase and overlay accuracy becomes more difficult to achieve
Solution Approach 1:
The patent replaces mechanical positioning and alignment methods with optical detection. Instead of relying solely on mechanical precision of substrate table positioning, the system uses a detector to optically inspect alignment marks and electronically determine substrate position. This substitution of mechanical alignment with optical-mechanical-electronic integration enables higher precision alignment required for smaller critical feature sizes.
3Manufacturing precision
If substrate is moved to alignment measuring area for inspection before exposure, then overlay accuracy is improved, but processing time increases
Solution Approach 1:
The patent enables continuous inspection and exposure operations by positioning the detector to inspect alignment marks during the substrate's continuous movement through the exposure area. Rather than stopping or pausing the substrate for separate inspection, the system performs alignment verification continuously during the normal exposure process, eliminating idle time and maintaining continuous productive operation.
Data Source
AI summary
A lithography apparatus includes a projection system configured to project a radiation beam onto a substrate, a detector configured to inspect the substrate, and a substrate table configured to support the substrate and move the substrate relative to the projection system and the detector. The detector is arranged to inspect a portion of the substrate while the substrate is moved and before the portion is exposed to the radiation beam.