Wafer Table Support Structure Using Low Thermal Expansion Struts
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Solution Overview
Problem
Existing support structures for wafer tables in lithography systems, which use low thermal expansion materials to maintain accurate positioning under changing thermal conditions, are costly and difficult to machine.
Innovation Solution
A support structure with a base and an interface member connected via struts made from low thermal expansion materials, allowing the interface member to move relative to the base while maintaining a constant distance, reducing material needs and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low thermal expansion materials are used for the entire support structure, then positioning accuracy under thermal changes is improved, but manufacturing cost and machining difficulty increase
Solution Approach 1:
The patent applies local quality by using low thermal expansion materials only in critical areas (interface member and struts) where dimensional stability is essential for positioning accuracy, while the base can be made from more economical materials. This localized application of special materials resolves the contradiction by achieving sufficient positioning accuracy without the high cost of using low thermal expansion materials throughout the entire structure.
Solution Approach 2:
The support structure is segmented into distinct functional components: a base, an interface member, and struts. This segmentation allows each component to be optimized independently - the interface member and struts use low thermal expansion materials for precision, while the base uses more cost-effective materials, thereby reducing overall manufacturing cost while maintaining positioning accuracy.
2Measurement precision
If low thermal expansion materials are used for the entire support structure, then positioning accuracy under thermal changes is improved, but machining difficulty increases
Solution Approach 1:
By applying low thermal expansion materials only to the interface member and struts rather than the entire structure, the patent reduces the volume of difficult-to-machine material while maintaining positioning accuracy in the critical positioning interface areas.
Solution Approach 2:
Segmenting the structure allows the base to be manufactured from more easily machined materials, while only the smaller interface member and struts require the specialized low thermal expansion materials that are more difficult to machine.
3Reliability
If the interface member has a large area to match the base, then thermal expansion compensation is improved, but material usage and costs increase
Solution Approach 1:
The patent extracts the thermal expansion compensation function from the base structure and relocates it to the struts made of low thermal expansion materials. This allows the interface member to have a smaller area than the base, reducing material usage while the struts maintain the constant distance between the interface member and reference surface despite thermal expansion of the base.
Solution Approach 2:
Thermal expansion compensation is applied locally through the struts rather than requiring the entire interface member to match the base area, achieving reliable thermal compensation with reduced material quantity.
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
The solution enables accurate positioning of the wafer table under thermal changes while minimizing material usage and machining costs, maintaining precise alignment and reducing stress on the struts.
Implementation Method 1
the at least one strut ensures that a distance between the reference surface and the interface member remains substantially constant, even when the base deforms in a manner different than the interface member, for instance due to thermal expansion
Implementation Method 2
a flexible support supporting said interface member on said base, wherein said flexible support allows movement of said interface member relative to said base substantially within a plane of movement
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
The invention relates to a support structure (1) for supporting a wafer table in a lithography system, said support structure comprising: a base (20) comprising a reference surface (40, 50), an interface member (30), made from a low thermal expansion ma¬ terial, arranged on top of said base and adapted for positioning said wafer table on the support structure, wherein said interface member is connected to said reference sur¬ face via at least one strut (60, 61, 66, 67), and wherein the at least one strut is made from a low thermal expansion material. The inven¬ tion further relates to a lithography system comprising such a support structure.