Electrostatic Clamp with ULE Layers for Thermal Stress Management
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Solution Overview
Problem
Lithographic apparatuses using EUV radiation face challenges in securely holding objects and preventing heat-induced and stress-induced deformations due to the use of electrostatic clamps, which can cause stress and heat damage, especially when using coolant systems that introduce thermal stress.
Innovation Solution
An electrostatic clamp is designed with multiple ultra-low expansion (ULE) layers and a composite layer of alternating electrically conductive and insulating layers, along with fluid channels for thermally conditioned fluids, to securely hold objects and manage thermal stress without inducing deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrostatic clamp is used to hold objects in vacuum regions, then the object can be securely clamped, but stress and heat damage may be transferred to the object causing deformations
Solution Approach 1:
The clamp is constructed as a multi-layer composite structure combining ULE glass layers with metal layers. The ULE glass provides ultra-low thermal expansion to minimize stress and heat transfer, while the metal layers provide structural strength and electrical conductivity for electrostatic clamping. This composite design allows the clamp to securely hold objects while reducing harmful stress and heat transfer.
Solution Approach 2:
Different regions of the clamp have different material properties optimized for specific functions. The ULE glass layers are positioned where thermal stability is critical to protect the clamped object, while metal layers are positioned where structural strength and electrical conductivity are needed. This localized material assignment reduces overall stress and heat damage to the object.
2Temperature
If coolant is circulated through the electrostatic clamp to regulate temperature, then heat-induced deformation is reduced, but thermal stress is created in the clamp structure
Solution Approach 1:
The multi-layer composite structure of ULE glass and metal layers provides differential thermal expansion management. When coolant circulates through the clamp, the ULE glass layers experience minimal thermal expansion due to their ultra-low expansion properties, while the metal layers accommodate more thermal stress. This protects the clamped object from stress-induced deformation while still allowing temperature regulation.
Solution Approach 2:
The clamp's composite structure changes its thermal response parameters when coolant is introduced. The ULE glass layers maintain dimensional stability across temperature changes, while the metal layers flex to accommodate thermal expansion. This parameter adaptation allows effective cooling while minimizing thermal stress transfer to the clamped object.
3Manufacturing precision
If EUV radiation is used to reduce minimum printable feature size, then lithographic resolution is improved, but unwanted non-EUV radiation causes heat damage and loss of contrast
Solution Approach 1:
The clamp's multi-layer structure provides localized thermal management where ULE glass layers are positioned to protect the clamped object from heat generated by non-EUV radiation. These layers act as thermal barriers while allowing EUV radiation to pass through, selectively filtering harmful thermal effects while maintaining lithographic precision.
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 effectively reduces heat-induced and stress-induced deformations in clamped objects by using ULE materials and a composite layer to manage thermal expansion and stress, while maintaining the structural integrity and stability required for precise lithographic operations.
Implementation Method 1
an electrostatic clamp may be used to clamp an object, such as a patterning device and/or a substrate
Implementation Method 2
Each of the first, second, and third layer includes a first, second, and third ultra-low expansion (ULE) material, respectively
Implementation Method 3
The plurality of fluid channels may be configured to carry a thermally conditioned fluid
Data Source
AI summary
An electrostatic clamp (300) and a method for manufacturing the same is disclosed. The electrostatic clamp includes a first layer (302) having a first ultra-low expansion (ULE) material, a second layer (304) coupled to the first layer, having a second ULE material, and a third layer (306), coupled to the second layer, having a third ULE material. The electrostatic clamp further includes a plurality of fluid channels (316) located between the first layer and the second layer and a composite layer (308) interposed between the second layer and the third layer. The method for manufacturing the electrostatic clamp includes forming the plurality of fluid channels, disposing the composite layer on the third layer, and coupling the third layer to the second layer. The plurality of fluid channels is configured to carry a thermally conditioned fluid for temperature regulation of a clamped object.