Spectral Purity Filter for Lithography EUV Transmission

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Solution Overview

Problem

Lithographic apparatuses face challenges in achieving high spectral purity, particularly in reducing deep ultraviolet (DUV) and infrared (IR) radiation while maintaining high extreme ultraviolet (EUV) transmission, which is crucial for minimizing feature size in microelectronics manufacturing.

Innovation Solution

A spectral purity filter with a membrane formed from materials like polysilicon, multilayer materials, or graphene, positioned adjacent to the substrate table, is used to filter out DUV and IR radiation, ensuring an EUV transmission of at least 80% and DUV transmission of less than 30%, while being adaptable for movement and gas supply systems to prevent damage and maintain vacuum integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a spectral purity filter is introduced to reduce DUV and IR radiation, then spectral purity is improved, but device complexity increases

Engineering Contradiction:

ImproveDUV and IR radiationVSAvoidfilter system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent employs a thin film filter made of polysilicon or multilayer materials that can be integrated into the existing lithographic apparatus structure. This thin film approach provides effective spectral filtering while minimizing the addition of complex mechanical components, thus improving spectral purity with limited increase in device complexity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The spectral purity filter acts as an intermediary element positioned in the radiation beam path between the source and the substrate. This mediator selectively transmits EUV radiation while blocking DUV and IR radiation, achieving spectral purification without requiring fundamental redesign of the lithographic system.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If a filter is positioned adjacent to the substrate table to close the projection system opening, then spectral purity is improved, but reliability decreases due to potential damage from plasma or particles

Engineering Contradiction:

Improvespectral purityVSAvoidfilter durability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent incorporates protective measures such as positioning the filter in a location shielded from direct plasma exposure and implementing gas flow systems that prevent particle deposition on the filter. These preventive measures protect the filter from damage before it occurs, maintaining both spectral purity and reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The filter is designed as a replaceable component that can be quickly exchanged when degraded. This approach allows the system to maintain high reliability by having backup filters ready, while the primary filter continues to provide spectral purification functionality.

Inventive Principle:

Principle #26Copying

3Object-affected harmful factors

If a membrane filter is used to achieve high EUV transmission, then spectral purity is improved, but manufacturing precision requirements increase due to the need for thin, uniform membranes

Engineering Contradiction:

ImproveEUV transmissionVSAvoidmembrane thickness uniformity

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent employs composite material structures such as polysilicon layers or multilayer stacks that can be deposited with controlled thickness using standard semiconductor manufacturing techniques. These composite structures provide the necessary EUV transmission while being manufacturable with precision compatible with existing lithographic processes.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The filter design allows for adjustment of material composition and thickness parameters to optimize EUV transmission while staying within manufacturable precision limits. By tuning these parameters, the system achieves spectral purity without requiring impossible manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

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 effectively enhances the spectral purity of the radiation beam, allowing for smaller feature sizes in microelectronics manufacturing by minimizing unwanted radiation, thus improving the precision and reliability of the lithographic process.

Implementation Method 1

the filter has a deep ultraviolet (DUV) transmission of less than 30% and/or is an extreme ultraviolet (EUV) transmission filter with an EUV transmission of at least 80%

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS9606445B2Lithographic apparatus and method of manufacturing a device

Publication Date: 2017.03.28 ASML NETHERLANDS BV

AI summary

There is disclosed a lithographic apparatus provided with a spectral purity filter which may be provided in one or more of the following locations: (a) in the illumination system, (b) adjacent the patterning device, either a static location in the radiation beam or fixed for movement with the patterning device, (c) in the projection system, and (d) adjacent the substrate table. The spectral purity filter is preferably a membrane formed of polysilicon, a multilayer material, a carbon nanotube material or graphene. The membrane may be provided with a protective capping layer, and/or a thin metal transparent layer.