EUV Mask Substrate Holding Tool with Electrostatic Chuck
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Solution Overview
Problem
Conventional glass substrate-holding tools for EUV mask blank production face challenges in preventing displacement, deformation, scratches, and foreign substance deposition during the formation of reflective and absorber layers, due to insufficient holding force and increased pressure per unit area, which can lead to reduced holding efficiency and quality issues.
Innovation Solution
A glass substrate-holding tool employing an electrostatic chuck in a non-contact state with a supporting member that maintains a specific distance and area ratio to the glass substrate's quality-guaranteed region, providing a sufficient holding force while minimizing contact and pressure on critical areas, thus preventing scratches and foreign substance deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a mechanical chuck or electrostatic chuck is used to hold the glass substrate, then the substrate can be securely held during film formation, but the holding pressure may cause displacement, deformation, scratches, or foreign substance deposition on the substrate surface
Solution Approach 1:
The holding surface is divided into multiple electrode regions (central electrode, intermediate electrodes, peripheral electrodes) that can be independently controlled. This segmentation allows different holding forces to be applied to different areas of the substrate, preventing excessive pressure on critical regions while maintaining overall holding stability.
Solution Approach 2:
Different electrode regions provide different holding characteristics: the central electrode provides strong holding for the substrate center, intermediate electrodes provide gradient holding, and peripheral electrodes provide edge support. This local differentiation prevents uniform high pressure that causes substrate damage while maintaining adequate holding force.
2Reliability
If the holding pressure is increased to prevent substrate displacement, then holding stability improves, but the risk of scratches and foreign substance deposition increases
Solution Approach 1:
The holding voltage can be dynamically adjusted during the film formation process. The system can apply higher holding force initially to prevent displacement, then reduce pressure as the process progresses to minimize substrate damage risk, adapting to changing process conditions.
Solution Approach 2:
The substrate is positioned and preliminary holding is established before film deposition begins. This preliminary action ensures the substrate is securely positioned without requiring excessive continuous pressure during the actual film formation, reducing the risk of pressure-induced damage.
3Force
If the electrostatic chuck active surface area is increased to improve holding force, then holding efficiency increases, but the area exposed to potential foreign substances and scratches also increases
Solution Approach 1:
The electrostatic chuck is divided into multiple independently controllable electrode regions. This allows the active surface area to be effectively increased through distributed electrodes while limiting the exposed area in any one location, reducing the probability of foreign substance deposition or scratch propagation.
Solution Approach 2:
Different electrode regions have different active surface characteristics optimized for their specific functions. Central electrodes have smaller exposed areas for precise center holding, while peripheral electrodes have larger areas for edge support, optimizing the balance between holding force and exposed surface area.
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 tool effectively prevents glass substrate displacement, deformation, and foreign substance deposition, ensuring a stable and high-quality EUV mask blank production by maintaining a controlled electrostatic attractive force and using van der Waals attraction for additional support, thereby enhancing the holding force and reducing the risk of scratches.
Implementation Method 1
an electrostatic chuck for attracting a rear surface of a glass substrate in a non-contact state by an electrostatic attractive force
Implementation Method 2
using van der Waals attraction for additional support
Data Source
AI summary
A glass substrate-holding tool, adapted to be employed during the production of a reflective mask blank for EUV lithography (EUVL), includes an electrostatic chuck and a supporting member. The chuck attracts a rear surface of a glass substrate in a non-contact manner by electrostatic attractive force. The supporting member partly supports the rear surface. An area ratio of a projected area of an active surface of the chuck for providing the electrostatic force to an area of a quality-guaranteed region of the rear surface is from 0.5 to 1.0. The active surface is apart from the rear surface by more than 20 μm. The supporting member is configured to support only a region including at least two of four sides defining an outer portion outside the quality-guaranteed region.