Electrostatic Clamp Burls Dielectric Pinhole Mitigation
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Solution Overview
Problem
Existing electrostatic clamps in lithographic apparatuses, particularly in EUV environments, face challenges in effectively holding substrates without causing contamination or distortion due to vacuum constraints and issues with dielectric layer formation on rough resistive surfaces, leading to pinholes and uneven electric fields.
Innovation Solution
An electrostatic clamp is fabricated by sandwiching an electrode between resistive material layers with a dielectric layer on top, forming burls by etching to create a smooth surface, and adding conductive material to prevent charge buildup, ensuring a robust and even electric field for secure substrate holding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a dielectric layer is formed on a rough resistive surface, then the electrostatic clamp structure is completed, but pinholes and uneven electric fields occur leading to contamination and distortion
Solution Approach 1:
A smoothing layer is deposited on the rough resistive surface before forming the dielectric layer. This preliminary smoothing action prevents pinholes and ensures uniform electric field distribution in the subsequent dielectric layer, eliminating contamination and distortion issues.
Solution Approach 2:
A smoothing layer acts as an intermediary between the rough resistive surface and the dielectric layer. This intermediate layer bridges the roughness of the resistive material, providing a smooth foundation for the dielectric layer and preventing direct contact between the dielectric and surface irregularities that would cause pinholes.
2Reliability
If vacuum clamp is used in EUV lithographic apparatus, then substrate holding is achieved, but vacuum constraints prevent its practical use in certain regions
Solution Approach 1:
The vacuum clamp mechanism is replaced with an electrostatic clamp that uses electrostatic forces instead of vacuum pressure. This substitution allows substrate holding in regions where vacuum conditions are not practical, maintaining reliability while improving adaptability to different environmental constraints.
Solution Approach 2:
The holding mechanism changes from pressure-based (vacuum) to field-based (electrostatic). By changing the fundamental parameter from mechanical pressure to electric field strength, the system becomes adaptable to non-vacuum environments while maintaining substrate holding capability.
3Reliability
If electrostatic clamp is designed with electrode and dielectric layer, then substrate clamping is achieved, but charge buildup causes uneven electric fields reducing clamping effectiveness
Solution Approach 1:
A conductive layer is added to extract and dissipate excess charge that would otherwise build up on the dielectric layer. This extraction of accumulated charge maintains uniform electric field distribution, preventing distortion and improving clamping effectiveness.
Solution Approach 2:
The conductive layer continuously discards accumulated charge to the substrate or ground, preventing charge buildup that would cause electric field non-uniformity. This continuous charge management ensures stable and uniform electrostatic clamping throughout operation.
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 reliable and efficient electrostatic clamp that securely holds substrates without contamination or distortion, maintaining pattern accuracy and extending the clamp's operational lifespan by avoiding pinholes and uneven electric fields.
Implementation Method 1
An electrostatic clamp may be used instead. An electrostatic clamp may be used to electrostatically clamp (i.e., hold) an object
Data Source
Figure 1
Figure 2~3
Figure 4a~4d
AI summary
An electrostatic clamp (12) comprising an electrode (2), a layer of resistive material (6) located on the electrode, and a layer of dielectric (8) located on the resistive material, wherein the electrostatic clamp further comprises burls (10) which project from the layer of dielectric.