EUV Mirror Capping Layer for Tin Particle Suppression

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Solution Overview

Problem

Existing extreme ultraviolet light generating apparatuses face challenges in maintaining the reflectance of EUV light due to accumulation of fine particles on the multilayer film, which reduces the effectiveness of the EUV light reflective mirrors.

Innovation Solution

A mirror configuration for extreme ultraviolet light that includes a substrate with a multilayer film and a capping layer comprising a first layer of metal oxide and a second layer of metal boride or nitride, which promotes a substitution reaction with tin fine particles to prevent accumulation and maintain reflectance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a simple capping layer is used on the multilayer film, then the device complexity is reduced, but fine particles accumulate on the multilayer film reducing reflectance

Engineering Contradiction:

Improvecapping layer structureVSAvoidreflectance maintenance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The capping layer is constructed as a composite structure with a first layer containing metal oxide and a second layer containing metal boride or nitride. This composite material structure provides both protection for the multilayer film and active substitution reaction capability against tin fine particles, resolving the contradiction between simple structure and effective particle suppression.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The capping layer acts as an intermediary between the external environment (tin fine particles) and the multilayer film. It provides a protective barrier that actively substitutes tin particles through chemical reactions, preventing direct contact and damage to the underlying multilayer film structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a thicker capping layer is used to prevent fine particle accumulation, then reflectance is maintained, but the device complexity and manufacturing difficulty increase

Engineering Contradiction:

ImprovereflectanceVSAvoidcapping layer fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The capping layer is segmented into two distinct functional layers: a first layer with metal oxide and a second layer with metal boride or nitride. This segmentation allows each layer to be optimized for specific thickness and composition, enabling effective particle suppression while controlling overall thickness to maintain manufacturability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention optimizes the thickness and compositional parameters of each capping layer to achieve the minimum effective thickness needed for substitution reactions. By carefully controlling these parameters, the design maintains high reflectance while avoiding excessive thickness that would complicate manufacturing.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a single-layer capping structure is used, then the manufacturing process is simplified, but the substitution reaction effectiveness is reduced

Engineering Contradiction:

Improvecapping layer depositionVSAvoidfine particle suppression

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The dual-layer composite structure combines materials with complementary properties: the metal oxide layer provides one type of substitution reaction capability while the metal boride/nitride layer provides another. This composite approach enhances overall particle suppression effectiveness without significantly complicating the deposition process.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Each layer in the capping structure is assigned specific local quality characteristics appropriate to its function. The first layer contains metal oxide optimized for certain substitution reactions, while the second layer contains boride or nitride optimized for other reactions, creating locally optimized zones within the overall capping structure.

Inventive Principle:

Principle #3Local quality

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 proposed configuration effectively suppresses the accumulation of tin fine particles, enhancing the life of the capping layer and maintaining high reflectance of EUV light by promoting a substitution reaction that converts tin fine particles into stannane, thereby preventing their accumulation on the multilayer film.

Implementation Method 1

promotes a substitution reaction with tin fine particles to prevent accumulation and maintain reflectance

Methodology Applied

Scientific EffectSubstitution reaction: Chemical Bonding

Implementation Method 2

a multilayer film provided on the substrate and configured to reflect extreme ultraviolet light

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS11614572B2Mirror for extreme ultraviolet light and extreme ultraviolet light generating apparatus

Publication Date: 2023.03.28 GIGAPHOTON INC

AI summary

A mirror for extreme ultraviolet light includes: a substrate (41); a multilayer film (42) provided on the substrate and configured to reflect extreme ultraviolet light; and a capping layer (53) provided on the multilayer film, and the capping layer includes a first layer (61) containing an oxide of a metal, and a second layer (62) arranged between the first layer and the multilayer film and containing at least one of a boride of the metal and a nitride of the metal.