Lithography Optical System Preview Field Positioning
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Solution Overview
Problem
Existing optical systems for producing lithographic structures face challenges in achieving precise positioning of substrates over large areas due to the small size of the writing field compared to the overall substrate, leading to inaccuracies in structure placement.
Innovation Solution
An optical system with a projection unit and a preview unit, where the preview field is significantly larger than the writing field, allowing for the use of relative coordinates to accurately position the writing field, and including a substrate holder with translational freedom and a control unit to store and utilize these coordinates for precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a small writing field is used for structure production, then manufacturing precision is improved, but positioning accuracy over large substrate areas deteriorates
Solution Approach 1:
The system divides the large substrate area into multiple regions: a large preview field for positioning and a small writing field for structure production. The preview field (e.g., 10×10 mm²) allows for accurate positioning of the writing field across the entire substrate, while the writing field (e.g., 400×400 μm²) maintains high manufacturing precision for the actual structure fabrication.
Solution Approach 2:
The preview field acts as an intermediary between the large substrate area and the small writing field. By imaging the preview field with the preview optical unit and using stored relative coordinates, the system enables accurate positioning of the writing field without requiring the writing field itself to be large, thus resolving the contradiction between positioning accuracy and manufacturing precision.
2Measurement precision
If a large preview field is used to cover the entire substrate, then positioning accuracy is improved, but device complexity increases
Solution Approach 1:
The projection optical unit and preview optical unit are carried by a common frame, merging their mechanical support and alignment systems. This shared infrastructure reduces device complexity while enabling the preview field to cover large substrate areas for accurate positioning. The common frame ensures stable relative positioning between the two optical units.
Solution Approach 2:
The preview optical unit creates an optical copy (image) of the preview field on the substrate surface. This optical copy allows for non-contact, high-precision positioning measurements without requiring physical access to the entire substrate area, thereby improving positioning accuracy while avoiding the complexity of mechanical scanning systems.
3Manufacturing precision
If the writing field is made very small for optimized structure production, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The system performs preliminary positioning actions by imaging the preview field and calculating relative coordinates before the actual writing process. The control unit stores relative coordinates that specify the position of the writing field relative to the preview field, enabling rapid repositioning without repeated alignment procedures. This preliminary coordination of coordinates allows the small writing field to move quickly across the substrate, maintaining high productivity despite its limited size.
Data Source
AI summary
An optical system for producing lithographic structures is disclosed. Also disclosed is a method for determining relative coordinates of a position of a writing field relative to a position of a preview field in such an optical system, and a method for producing lithographic structures using such an optical system.