Electrostatic Chuck In-Situ Particle Removal
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Solution Overview
Problem
Current methods for cleaning particulate contamination from the vicinity of a support in lithographic apparatuses, such as electrostatic chucks, are slow and inefficient, particularly in EUV technology where reticle particle contamination is a critical issue.
Innovation Solution
An electrostatic chuck generates an electric field to attract particles to the front side of a sacrificial cleaning reticle or modified substrate with a partial conductive coating, allowing the field to penetrate and combine with polarity switching and EUV exposure to effectively remove charged particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flushing gas flow is used to remove particles, then particle removal is achieved, but the cleaning process is slow and has limited efficiency
Solution Approach 1:
The patent replaces the mechanical flushing system (gas flow) with an electrostatic field-based particle removal system. The electrostatic chuck generates an electric field that extends through a sacrificial reticle to attract and remove particles from the reticle stage vicinity, providing faster and more efficient cleaning without the limitations of gas flow methods.
2Ease of operation
If a conductive coating is applied to the reticle backside, then electrostatic chucking is enabled, but the electric field cannot penetrate to attract particles
Solution Approach 1:
The patent applies local quality by using a sacrificial reticle with a partial conductive coating rather than a complete coating. The conductive coating is applied only to certain areas (e.g., peripheral regions) to enable electrostatic chucking, while leaving other areas (e.g., central regions) uncoated or with reduced conductivity to allow electric field penetration for particle attraction.
3Productivity
If polarity switching is implemented, then charged particles can be attracted to the substrate, but the system complexity increases
Solution Approach 1:
The patent implements self-service by utilizing the existing voltage supply system of the electrostatic chuck to generate the electric field for particle attraction. The same voltage supply that provides chucking force is used to create the particle-attracting field, eliminating the need for separate particle removal equipment and reducing overall system complexity.
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 method provides a faster and more efficient in-situ cleaning technique, reducing particle contamination near the reticle stage without disturbing the vacuum environment, enhancing cleaning efficiency by attracting and trapping particles on a nonconductive surface.
Implementation Method 1
an electric field generated by an electrostatic chuck is used to attract particles to the front (exposed) side of a sacrificial cleaning reticle or modified substrate
Implementation Method 2
an electric field generated by an electrostatic chuck is used to attract particles
Implementation Method 3
By polarity switching in combination with or without EUV exposure charged particles can be attracted to the front side of the substrate
Implementation Method 4
By polarity switching in combination with or without EUV exposure charged particles can be attracted
Data Source
AI summary
Methods and systems are described for reducing particles in the vicinity of an electrostatic chuck (300) in which a cleaning reticle or substrate (320) is secured to the chuck, the cleaning reticle or substrate having surfaces partially devoid of conductive material so that an electric field from the chuck can pass through to a volume adjacent the substrate to draw particles (360) in the volume to the surface of the substrate. Voltage supplied to the chuck may have an alternating polarity to enhance the attraction of particles to the surface.