Lithography Balance Mass Vibration Control
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Solution Overview
Problem
Lithographic apparatuses face challenges in maintaining accuracy due to vibrations caused by balance mass arrangements and other disturbances, which affect the precision of measurement and exposure processes, leading to errors in overlay and critical dimension control.
Innovation Solution
A metrology or inspection apparatus with a system that includes a base structure, an object support, a balance mass to absorb reaction forces, an actuator to apply forces, and sensors to detect disturbances, with a control system that adjusts forces to mitigate vibrations and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a balance mass arrangement is used to counteract vibrations from substrate table acceleration, then vibration suppression is improved, but new vibrations are generated due to torque components acting on the illuminator
Solution Approach 1:
A balance mass is coupled to the substrate table through a gas bearing to counteract vibrations caused by substrate table acceleration. The balance mass moves in opposition to the substrate table motion, reducing the net vibration transmitted to the illuminator and improving measurement accuracy.
Solution Approach 2:
A gas bearing is introduced as an intermediary between the balance mass and the substrate table. This gas bearing allows the balance mass to follow substrate table acceleration while minimizing direct mechanical coupling, thereby reducing torque transmission to the illuminator mounting structure.
2Productivity
If the substrate table is accelerated to reposition the substrate, then productivity is improved, but vibrations are generated that affect measurement accuracy
Solution Approach 1:
The balance mass system allows rapid substrate table acceleration for improved productivity while the balance mass counteracts the inertial forces, preventing vibration transmission to the measurement system and maintaining measurement precision during dynamic operations.
Solution Approach 2:
The balance mass is coupled through a gas bearing that allows dynamic motion, enabling the system to adapt to rapid substrate table repositioning while continuously counteracting vibrations. This dynamic coupling maintains measurement accuracy during acceleration and deceleration phases.
3Device complexity
If the illuminator is mounted to the substrate table to reduce torque effects, then device complexity is reduced, but the illuminator becomes susceptible to balance mass vibrations
Solution Approach 1:
The gas bearing acts as an intermediary that decouples the illuminator from balance mass vibrations while maintaining the simplified mounting arrangement. The gas bearing filters out high-frequency vibrations from the balance mass, allowing the illuminator to remain mounted to the substrate table without direct vibration transmission.
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 solution effectively reduces vibrations and improves the accuracy of measurements and exposure processes, enhancing the precision of overlay and critical dimension control, thereby improving the quality of device manufacturing.
Implementation Method 1
a balance mass 650 supported by a gas bearing 410 between the balance mass 650 and the base structure 625
Implementation Method 2
an actuator connected to the balance mass 650 and the base structure 625, the actuator configured to apply a force to the balance mass 650 and the base structure 625
Data Source
AI summary
An apparatus having: a system configured to measure an object; a base structure; an object support constructed to hold the object, the object support movably supported on the base structure; a balance mass configured to absorb a reaction force arising from movement of the object support; an actuator connected to the balance mass and the base structure, the actuator configured to apply a force to the balance mass and the base structure; a sensor configured to produce a signal for a measured characteristic of the base structure corresponding to a disturbance, or its effect, acting on the base structure; and a control system configured to determine, based on at least the signal for the measured characteristic of the base structure, a signal for the actuator to apply a force to the base structure and/or the balance mass.