Lithography Substrate Holder Seal Geometry for Unloading Wear Control
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Solution Overview
Problem
The wear on support elements and damage to the underside of substrates during unloading in lithographic apparatuses leads to contamination and focusing/overlay issues, limiting the usable life of the substrate holder.
Innovation Solution
A substrate holder with support elements and a seal unit featuring a first seal member positioned radially outward, where the force applied to the seal member during loading/unloading is greater than that applied to the support elements, and a coating made of diamond-like carbon or other materials to reduce wear and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If support elements are used to support the substrate during unloading, then the substrate can be held and removed from the holder, but the support elements experience wear that limits the usable life of the substrate holder
Solution Approach 1:
The patent applies this principle by making the seal member a sacrificial component that is intentionally designed to wear faster than the support elements. The seal member acts as a disposable element that protects the more expensive and critical support elements from wear during substrate loading and unloading operations.
Solution Approach 2:
The seal member serves as an intermediary between the substrate and the support elements. During substrate manipulation, the seal member is the primary contact point, mediating the interaction forces and preventing direct wear on the support elements, thereby extending their service life.
2Object-affected harmful factors
If the seal member is positioned close to support elements to prevent immersion liquid contamination, then contamination is reduced, but the substrate may contact and wear both components during unloading
Solution Approach 1:
The seal member is designed as a sacrificial component that is replaced periodically. By positioning it close to the support elements and accepting that it will wear and generate particles, the system protects the support elements from wear. The seal member's shorter service life is an acceptable trade-off to maintain system reliability.
Solution Approach 2:
The patent converts the potential harm of seal member wear into a benefit by designing the seal member to be replaceable and positioning it to absorb wear that would otherwise damage the support elements. The wear of the sacrificial seal member actually protects the more critical components, turning a harmful effect into a protective mechanism.
3Ease of operation
If the substrate is deformed during unloading causing it to cantilever down, then the substrate can be released from the holder, but the deformed substrate contacts and wears the support elements and seal features
Solution Approach 1:
The seal member acts as an intermediary that contacts the deformed substrate during unloading. Instead of the substrate directly contacting and wearing the support elements, the seal member absorbs the contact, allowing the substrate to be released even in a deformed state without damaging the support elements.
Solution Approach 2:
The seal member is designed to withstand and absorb the wear from deformed substrates during unloading. As a sacrificial component with shorter service life, it protects the support elements from damage caused by substrate deformation, maintaining manufacturing precision for the critical components.
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
Reduces wear on support elements and damage to substrates, minimizing contamination and maintaining system stability by ensuring stable long-term performance of the substrate holder.
Implementation Method 1
a coating made of diamond-like carbon or other materials to reduce wear and damage
Data Source
AI summary
A substrate holder, for a lithographic apparatus, having a main body, a plurality of support elements to support a substrate and a seal unit. The seal unit may include a first seal positioned outward of and surrounding the plurality of support elements. A position of a substrate contact region of an upper surface of the first seal may be arranged at a distance from the plurality of support elements sufficient enough such that during the loading/unloading of the substrate, a force applied to the first seal by the substrate is greater than a force applied to the plurality of support elements by the substrate. A profile of the contact region, in a cross section through the seal, may have a shape which is configured such that during the loading/unloading of the substrate, the substrate contacts the seal via at least two different points of the profile.