Structured Electrostatic Wafer Clamp for Lower Charging and Wafer Sag
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Solution Overview
Problem
Existing wafer clamps in lithographic apparatuses face challenges in maintaining tribological properties and preventing wafer sagging due to uneven surfaces and electrostatic clamping forces, particularly in EUV radiation systems.
Innovation Solution
The development of electrostatic wafer clamps with a support structure featuring burls, a dielectric layer, and embedded electrode layers, where the electrode layer is shaped to reduce charge effects and coupled to ground potential, using post bond structuring techniques like laser beam processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wafer table surface is made ultra-smooth, then the wafer can be held securely by electrostatic clamping, but the wafer becomes stuck and cannot be disengaged
Solution Approach 1:
The surface is segmented into multiple burls (protrusions) rather than being uniformly smooth. This segmentation creates discrete contact points that maintain electrostatic clamping while allowing air gaps for easy wafer release.
Solution Approach 2:
The surface has non-uniform local properties with burls providing localized contact points. The burls create areas of high electrostatic field concentration while maintaining overall surface functionality for both clamping and release operations.
2Ease of operation
If burls are formed on the wafer table surface to reduce smoothness, then wafer disengagement is improved, but the wafer sags in areas between burls due to applied forces
Solution Approach 1:
The burls are interconnected by grounding lines that create equipotential regions. This ensures uniform electrostatic potential distribution across the wafer surface, preventing sagging while maintaining the non-smooth surface geometry for easy disengagement.
Solution Approach 2:
The grounding lines act as intermediaries that connect the burls electrically. These grounding lines distribute the electrostatic forces uniformly, preventing wafer sagging in the regions between burls while the burls themselves provide the necessary surface texture for disengagement.
3Manufacturing precision
If grounding lines are added to interconnect burls, then wafer sagging is prevented, but the device complexity increases
Solution Approach 1:
The grounding lines are merged with the dielectric layer formation process. The grounding lines are coated on the dielectric layer in the same manufacturing sequence as the burl formation, combining multiple functions into a single integrated structure rather than adding separate components.
Solution Approach 2:
The dielectric layer serves multiple functions: it provides electrical insulation, supports the burl structure, and carries the grounding lines. This multi-functionality reduces the need for separate components and simplifies the overall device structure despite the added functionality.
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
This design enhances the stability and precision of wafer clamping, reducing sagging and improving the tribological properties of the wafer table surface, ensuring accurate and reliable patterning processes in lithographic applications.
Implementation Method 1
an electrostatic clamp for use in EUV radiation systems
Implementation Method 2
The shaping can be done by post bond structuring. The post bond structuring is performed using a laser beam.
Data Source
AI summary
Disclosed herein are embodiments that relate to an electrostatic wafer clamps and methods for forming and modifying electrode structures for electrostatic wafer clamps. Wafer clamps include electrode structures in a dielectric layer with a plurality of burls interconnected via grounding lines. By modifying the electrode structures near the grounding lines by post bond structuring or the like, the electric field can be reduced, resulting in lower cycle inducing charging.