Wear-Resistant Substrate Holder Bonding for Low-Friction Lithography
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Solution Overview
Problem
Lithographic substrate holders coated with diamond-like carbon (DLC) wear faster than expected due to the presence of sp2 hybridized carbon, leading to increased friction and focus/overlay errors during substrate exposure, requiring frequent re-polishing and re-conditioning.
Innovation Solution
A method involving a body made of glass, ceramic, or glass-ceramic with a wear-resistant material having a hardness of more than 20 GPa, such as diamond or cubic boron nitride, is brazed or laser-welded onto the substrate holder to enhance durability and reduce friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If diamond-like carbon (DLC) is deposited on the substrate holder to reduce wear and friction, then the friction coefficient is reduced, but the wear resistance is insufficient and the coating wears 10 times faster than desirable
Solution Approach 1:
The patent applies a composite material structure consisting of a ceramic substrate (SiC or SiSiC) combined with a diamond coating layer. This composite structure leverages the low friction properties of diamond while providing the structural integrity and thermal stability of ceramic materials, resolving the contradiction between ease of operation (low friction) and reliability (wear resistance).
Solution Approach 2:
The patent changes the material parameters by selecting specific ceramic materials (SiC, SiSiC) with controlled grain structures and combining them with diamond coatings. By optimizing the ceramic matrix composition and diamond layer properties, the patent achieves both low friction and high wear resistance simultaneously.
2Ease of operation
If DLC is deposited directly onto the burls of the substrate holder, then the friction between substrate holder and substrate is reduced, but the DLC layer wears quickly requiring frequent re-polishing
Solution Approach 1:
The patent creates a composite structure where a diamond coating is applied to the ceramic substrate holder surface. The diamond layer provides sustained low-friction properties over extended operational periods, significantly extending the lifespan of the substrate holder while maintaining ease of operation.
Solution Approach 2:
The patent uses a diamond-like carbon coating that replicates the desirable low-friction properties of natural diamond on the ceramic substrate surface. This copied diamond structure provides the same operational benefits without requiring the substrate holder itself to be made of diamond, thus extending operational lifespan while maintaining low friction.
3Ease of manufacture
If the substrate holder is made of ceramic material (SiC or SiSiC), then the material can be readily machined to desired shape, but the ceramic material wears quickly and has high frictional coefficient
Solution Approach 1:
The patent employs a composite material system where a ceramic substrate (easy to machine) is combined with a diamond coating layer (high wear resistance and low friction). This composite structure allows the substrate holder to be easily manufactured using conventional ceramic machining techniques while the diamond coating provides enhanced durability and reduced friction during operation.
Solution Approach 2:
The patent applies the hard, wear-resistant diamond material only to the specific surface areas that contact the substrate (the burls), while the bulk ceramic material maintains its machinability advantages. This local application of enhanced properties resolves the contradiction between ease of manufacture and wear resistance.
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 provides a significantly longer operational lifespan for substrate holders by reducing wear and friction, minimizing the need for frequent re-conditioning and improving exposure accuracy by maintaining a flat, unstressed substrate state.
Implementation Method 1
brazing or laser welding the wear-resistant material to the body
Implementation Method 2
brazing or laser welding the wear-resistant material to the body
Implementation Method 3
The comparably high frictional coefficient of the ceramic material may also prevent the substrate from relaxing into a flat unstressed state
Data Source
AI summary
A method for providing a wear-resistant material on a body. A composite body that may be obtained by the method. The composite body may be a substrate holder or a reticle clamp for use in a lithographic apparatus. The method includes providing a body made of glass, ceramic or glass-ceramic; providing a wear-resistant material having a hardness of more than 20 GPa; and brazing or laser welding the wear-resistant material to the body.