Laser-Sintered Burl Substrate Holder for EUV Electrostatic Clamping

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Solution Overview

Problem

In high-throughput lithographic apparatuses, conventional substrate holders face challenges in securely clamping substrates due to high accelerations, especially in extreme ultraviolet (EUV) radiation lithography where vacuum clamping is not feasible, and existing methods require replacement of components if burls are damaged.

Innovation Solution

A substrate holder with burls formed by laser-sintering is used, which allows for secure clamping through electrostatic forces and enables the use of a wider range of materials, including those previously unsuitable for machining, and allows for repair and replacement of individual burls, extending the component's lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If vacuum clamping is used to secure substrates, then clamping effectiveness is improved, but it cannot be applied in EUV radiation lithography where vacuum conditions are not feasible

Engineering Contradiction:

Improveclamping effectivenessVSAvoidapplicability in different lithography environments

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent transitions from vacuum-based clamping (relying on pressure differential) to electrostatic clamping (relying on electric field forces). This parameter change in the clamping mechanism allows the system to function effectively in atmospheric pressure environments required for EUV lithography while maintaining secure substrate holding capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the mechanical vacuum clamping system with an electrostatic field-based clamping system. By using electrostatic forces generated between the substrate holder and substrate, the system achieves effective clamping without requiring vacuum conditions, thus enabling use in EUV lithography environments

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If conventional machining methods are used to form burls, then manufacturing precision is maintained, but the range of usable materials is limited to machinable materials

Engineering Contradiction:

Improveburl formation precisionVSAvoidmaterial selection range

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent replaces conventional mechanical machining methods with laser-sintering technology. This substitution enables the formation of precise burls on materials that would be difficult or impossible to machine conventionally, such as cordierite and other ceramics, thereby expanding material selection while maintaining manufacturing precision

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the manufacturing process parameter from mechanical removal (machining) to thermal processing (laser sintering). This parameter change allows working with a broader range of materials including ceramics and composites that have poor machinability but can be effectively formed through controlled laser heating and sintering

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the entire substrate holder component is replaced when burls are damaged, then reliability is restored, but productivity is reduced due to frequent replacements

Engineering Contradiction:

Improvesubstrate holder functionalityVSAvoiddowntime for component replacement

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent segments the substrate holder into modular components: the main holder body and the burls as separate replaceable elements. When burls become damaged or worn, only the burls themselves need to be replaced rather than the entire substrate holder assembly, significantly reducing replacement time and maintaining productivity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention enables selective replacement of consumable burl components while retaining the valuable main holder body. The burls can be removed, replaced, or re-sintered as needed, allowing the system to recover and reuse the primary component structure while replacing only the worn elements

Inventive Principle:

Principle #34Discarding and recovering

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 laser-sintered burls provide robust and durable support, enabling effective clamping and reducing the need for frequent component replacement, while allowing for the use of materials with unique properties such as cordierite, which enhances the substrate holder's longevity and wear resistance.

Implementation Method 1

forming at least part of at least one of the burls comprises laser-sintering

Methodology Applied

Scientific EffectLaser sintering: Selective Laser Sintering

Implementation Method 2

allows for secure clamping through electrostatic forces

Methodology Applied

Scientific EffectElectrostatic forces: Electrostatics

Data Source

PatentUS11376663B2Substrate holder and method of manufacturing a substrate holder

Publication Date: 2022.07.05 ASML NETHERLANDS BV

AI summary

An object holder for a lithographic apparatus has a main body having a surface. A plurality of burls to support an object is formed on the surface or in apertures of a thin-film stack. At least one of the burls is formed by laser-sintering. At least one of the burls formed by laser-sintering may be a repair of a damaged burl previously formed by laser-sintering or another method.