EUV Mask Position Measuring Apparatus with Segmented Support
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Solution Overview
Problem
The challenge lies in accurately measuring pattern positional deviations on EUV masks, particularly due to the complexity of sub-resolution assistant features and the difficulty in maintaining a clean electrostatic chuck surface, which affects image positional accuracy and reproducibility in extreme ultraviolet lithography processes.
Innovation Solution
A position measuring apparatus using a combination of a three-point support member and a vacuum chuck to hold the mask substrate, allowing for precise measurement of positional deviations without the need for an electrostatic chuck, while maintaining the substrate in a clean and controlled environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrostatic chuck is used to hold the EUV mask, then the mask can be held stably in a vacuum chamber, but the chuck surface becomes contaminated with particles and residues, affecting measurement accuracy
Solution Approach 1:
The holding function is segmented into two distinct methods: electrostatic chucking for stable vacuum holding, and three-point support for clean measurement. The system separates the contamination-prone holding function from the precision measurement function by providing alternative support mechanisms for different operational phases.
Solution Approach 2:
A three-point support member acts as an intermediary device that provides a clean, particle-free reference frame for measurement. This intermediary support system allows measurements to be taken without direct contact between the mask and the contaminated electrostatic chuck surface.
2Manufacturing precision
If sub-resolution assistant features are added to correct optical proximity effects, then pattern printing accuracy improves, but the mask pattern complexity increases, affecting writing time and inspection difficulty
Solution Approach 1:
The patent replaces optical correction methods (sub-resolution assistant features) with a mechanical/physical measurement and correction approach. By directly measuring pattern positions and calculating deviations, the system substitutes complex optical corrections with simpler measurement and data processing.
Solution Approach 2:
The system creates a digital copy or model of the mask pattern positions through measurement, then uses this copied information to calculate and correct positional deviations. This allows correction without physically modifying the mask with complex assistant features.
3Measurement precision
If the backside of the EUV mask is held by three points without vacuum chucking, then the mask surface remains clean, but gravitational sag causes positional deviation in the written pattern
Solution Approach 1:
The system performs preliminary measurement of the mask backside topography to detect gravitational sag effects before pattern writing. By measuring and storing the sag characteristics in advance, the system can compensate for these effects during the writing process through coordinate transformation.
Solution Approach 2:
The system uses feedback from backside topography measurements to adjust and correct pattern positions. The measured sag information feeds into a calculation process that determines positional deviations, which then feed back into the writing process to compensate for gravitational effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables highly accurate measurement of pattern positional deviations, improves reproducibility, and maintains the cleanliness of the chuck surface, addressing the limitations of existing methods in EUV lithography.
Implementation Method 1
a vacuum pump to hold and chuck the substrate through the vacuum chuck member
Data Source
AI summary
A position measuring apparatus includes a holder having storage spaces in which a three-point support member for supporting a backside of a substrate being a mask at three points, and a vacuum chuck member for holding a backside of a substrate being a mask are prepared, a stage on which one of the three-point support member and the vacuum chuck member prepared in the storage spaces of the holder is mounted, a vacuum pump to hold and chuck the substrate through the vacuum chuck member in a state of being mounted on the stage, and a recognition unit to recognize a position of a pattern written on the substrate supported by the three-point support member mounted on the stage and a position of a pattern written on the substrate held by the vacuum chuck member on the stage.