Wafer Chuck Positioning via Segmented Magnetic Actuators
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Solution Overview
Problem
Existing positioning devices for wafer chucks in vacuum spaces face challenges in maintaining precise positioning across multiple degrees of freedom without fouling and are susceptible to environmental disturbances.
Innovation Solution
The positioning device employs a configuration with partially encircling coils around disc-shaped magnets and annular magnets with specific diameter relationships, along with Halbach arrays of permanent magnets, to provide actuation forces independent of distance and position, and incorporates a slide system with displacement means to enhance accuracy and reduce environmental interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wafer chuck is positioned in a vacuum space separated from positioning means, then fouling of the wafer chuck is prevented, but positioning accuracy over large distances deteriorates
Solution Approach 1:
The positioning system is segmented into two parts: a slide mechanism for coarse positioning over large distances and electromagnetic actuators for fine positioning. This segmentation allows the wafer chuck to be positioned accurately at any location within the vacuum chamber without requiring the entire positioning system to be in vacuum, thus preventing fouling while maintaining accuracy.
Solution Approach 2:
The slide acts as an intermediary mechanism between the base and the wafer chuck positioning system. It provides a mechanical platform that can move over large distances while carrying the electromagnetic actuators, thereby enabling accurate positioning without direct contact between positioning means and the vacuum environment.
2Force
If coils are placed inside the wafer chuck for actuation, then positioning force is achieved, but cable management complexity and wafer chuck height increase
Solution Approach 1:
Instead of placing coils inside the wafer chuck and leading cables to it, the invention inverts the arrangement by placing permanent magnets inside the wafer chuck and positioning coils outside on the slide. This eliminates the need for cables penetrating the vacuum seal while maintaining the electromagnetic actuation function.
Solution Approach 2:
The patent replaces the traditional coil-based electromagnetic actuation with a permanent magnet-based system. Permanent magnets eliminate the need for continuous electrical connections and cables, simplifying the mechanical design and reducing complexity in cable management while providing sufficient actuation force through magnetic interaction with external coils.
3Ease of manufacture
If positioning means are exposed to environmental conditions, then ease of manufacturing is improved, but positioning precision deteriorates due to environmental disturbances
Solution Approach 1:
The electromagnetic actuators and their coils are extracted from the vacuum environment and placed on the slide mechanism that operates in atmospheric conditions. This allows the majority of the positioning system to be manufactured using conventional methods while only the critical wafer chuck interface requires vacuum compatibility, thus maintaining precision without compromising manufacturing ease.
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 configuration allows for precise and disturbance-resistant positioning of the wafer chuck across six degrees of freedom, maintaining accuracy over larger distances with reduced environmental influence and minimizing the need for cables, thus optimizing the positioning device's performance in under-pressure environments.
Implementation Method 1
the coil is present partially around the disc-shaped round permanent magnet and partially present above it... as well as a coil and an annular permanent magnet... which vertical actuators each include gravity compensation means which comprise a disc-shaped round permanent magnet, as well as a coil and an annular permanent magnet
Implementation Method 2
permanent magnets, and positioning means for positioning the wafer chuck... which comprise at least six actuators... where from these actuators three vertical actuators position the wafer chuck in vertical direction
Data Source
Figure 1~2
Figure 3~5
AI summary
A positioning device (1) for a wafer chuck (13) comprises a housing (9) in which underpressure prevails, as well as the wafer chuck displaceable over the bottom (7) of the housing, and positioining means (17) located underneath the bottom for positioning the wafer chuck. The positioning means comprises eight actuators four of which form vertical actuators (23) which each have a disc-shaped round permanent magnet (25), as well as a coil (27) partly situated around it and partly above it, the bottom (27A) of which coil is present at a level in between the bottom (25A) and top (25B) of the disc-shaped magnet and whose inner diameter (D1) is larger than the outer diameter (D2) of the disc-shaped magnet. The wafer chuck accommodates an annular permanent magnet (29) above the coil, which magnet has an opening in the middle. The magnets (25, 29) are vertically polarized while the polarization of the one magnet is opposite to that of the other.