Balanced Positioning System for Lithography Metrology
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Solution Overview
Problem
Existing lithographic metrology tools face performance limitations and increased footprint due to the need for balance masses to counteract acceleration forces, which can be challenging in space-constrained environments.
Innovation Solution
A balanced positioning system is implemented, featuring a balance mass positioned relative to a track arrangement such that the centers of gravity of the balance mass and the substrate table or sensor arrangement are aligned, allowing for precise displacement using a motor arrangement and bearing support, minimizing vibrations and footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a balance mass is provided to counteract acceleration forces, then vibrations are reduced and measurement precision is improved, but the footprint of the machine increases
Solution Approach 1:
The balance mass is positioned inside the sensor stage, nesting one functional component within another. This allows the balance mass to counteract vibrations while not increasing the external footprint of the measurement apparatus, as it occupies space that would otherwise be unused or structural.
Solution Approach 2:
The balance mass is positioned at a different vertical level (above or below) the sensor stage rather than horizontally adjacent to it. This three-dimensional arrangement allows vibration counteraction without increasing the horizontal footprint, utilizing the vertical dimension to resolve the spatial conflict.
2Stability of the object's composition
If a balance mass is provided to counteract acceleration forces, then stability is improved, but the device complexity increases
Solution Approach 1:
The balance mass functionality is merged with the sensor stage structure. Rather than being a separate external component, the balance mass is integrated into the sensor stage assembly, reducing the number of discrete parts and simplifying the overall device architecture while maintaining vibration counteraction capability.
3Ease of manufacture
If the balance mass is positioned away from the track arrangement, then ease of manufacture is improved, but manufacturing precision decreases
Solution Approach 1:
The balance mass is strategically positioned to create a counterbalancing effect where its center of gravity aligns with the track arrangement. This positioning optimizes both manufacturability and precision by creating a symmetric mass distribution that naturally compensates for manufacturing tolerances and minimizes gravitational effects on measurement accuracy.
Data Source
AI summary
An inspection apparatus for measuring a property of a substrate (W), includes a base frame, a substrate table (51) to hold the substrate, an illumination system arranged to direct a beam of radiation onto the substrate and a sensor arranged to detect radiation reflected off the substrate. Two balanced positioning systems displace the substrate table and sensor relative to the base frame in several directions. Each balanced positioning system includes a balance mass (59, 61), a bearing arrangement (65) to movably support the balance mass and tracks effective to guide the displacement in each direction. A motor arrangement causes the displacement in each direction. The balance mass is positioned relative to the track arrangement such that the centers of gravity of each balance mass and the substrate table or the sensor are substantially aligned in the direction substantially perpendicular to the plane including the direction of displacement.