Lithography Beam-to-Chuck Alignment for Reproducible Wafer Positioning
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Solution Overview
Problem
Existing lithography systems face challenges in determining the position of a wafer with respect to the final projection system with high reproducibility, particularly when the wafer needs to be removed and repositioned between sessions, leading to alignment inaccuracies.
Innovation Solution
The system determines the spatial distribution of beam properties with respect to chuck position marks, allowing for precise alignment and positioning of the patterning beam relative to the target, using a support connecting the mark position system to the final projection system with low thermal expansion materials and flexures to minimize thermal deformations, and employing multiple beamlets for improved surface processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the wafer is removed and repositioned between sessions, then the lithography system can process multiple targets, but the position determination reproducibility deteriorates
Solution Approach 1:
The system performs preliminary characterization of the beam properties and spatial relationships before actual lithography sessions. By pre-determining the spatial distribution of beam properties with respect to chuck position marks and establishing reference frames in advance, the system eliminates the need for repeated position determinations when wafers are exchanged, thereby maintaining high reproducibility while enabling multi-target processing
Solution Approach 2:
The system creates a reference model of the beam spatial properties and chuck coordinate system relationships. This reference copy is established once during system initialization and then reused for all subsequent wafer processing sessions, allowing the system to rapidly determine wafer positions without repeated measurements, thus solving the contradiction between versatility and measurement precision
2Manufacturing precision
If the position of the patterning beam is determined with respect to chuck position marks, then the alignment precision is improved, but the system complexity increases
Solution Approach 1:
The system introduces chuck position marks as intermediary reference elements that mediate between the physical chuck and the beam coordinate system. These marks serve as a common reference frame that simplifies the alignment process by providing easily detectable positional references, thereby improving alignment precision without requiring complex direct measurement systems between the beam and wafer
Solution Approach 2:
The system replaces complex mechanical alignment mechanisms with optical/detector-based mark position detection. By using mark position systems that optically detect the positions of chuck position marks and compute spatial relationships through software, the system achieves high alignment precision while reducing mechanical complexity compared to traditional mechanical alignment systems
3Stability of the object's composition
If low thermal expansion materials and flexures are used to minimize thermal deformations, then the position stability is improved, but the manufacturing difficulty increases
Solution Approach 1:
The system changes the thermal parameter of the support structure by selecting materials with low thermal expansion coefficients. This parameter change ensures that the support maintains dimensional stability across temperature variations, thereby improving position stability. The manufacturing difficulty is accepted as a necessary trade-off for achieving the required thermal stability in precision lithography systems
Solution Approach 2:
The system employs composite construction combining low thermal expansion materials (such as invar or glass-ceramics) with flexible elements (flexures). This composite approach creates a support structure that simultaneously provides thermal stability and controlled flexibility for alignment adjustments, balancing position stability requirements with manufacturing feasibility
Data Source
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AI summary
The invention relates to a lithography system for processing a target, such as a wafer. The lithography system comprises a beam source arranged for providing a patterning beam, a final projection system arranged for projecting a pattern on the target surface, a chuck arranged for supporting the target and a mark position system connected to the final projection system and arranged for detecting a position mark on a surface.