EUV Reflective Mask Absorber Structure for Backside Layer Protection

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Solution Overview

Problem

EUV photo masks face damage to their backside conductive layers during the manufacturing process, which affects their performance and longevity in extreme ultraviolet lithography systems.

Innovation Solution

The development of an EUV reflective photo mask with a low reflective (high absorbing) absorber structure, comprising a substrate, a multilayer Mo/Si stack, a capping layer, an absorber layer, and a backside conductive layer, where the absorber layer is made of Cr-based materials with nitrogen incorporation to enhance EUV absorption and mechanical strength, and a photo catalytic layer for self-cleaning, preventing damage to the capping layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional absorber layer structure is used, then the EUV absorption is sufficient, but the backside conductive layer suffers damage during manufacturing

Engineering Contradiction:

Improvebackside conductive layer integrityVSAvoiddamage to backside conductive layer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A photo catalytic layer is introduced as an intermediary between the capping layer and the absorber layer. This layer acts as a mediator that prevents harmful factors from reaching the backside conductive layer while maintaining the EUV absorption function of the absorber layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent utilizes the photo catalytic properties of the intermediate layer to convert potentially harmful EUV radiation and processing conditions into beneficial self-cleaning effects. The photo catalytic layer activates under EUV exposure to decompose organic contaminants, thereby protecting the underlying structures without compromising performance.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If nitrogen is incorporated into the absorber layer to enhance EUV absorption, then the absorption efficiency improves, but the manufacturing complexity increases

Engineering Contradiction:

ImproveEUV absorption efficiencyVSAvoidabsorber layer composition complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent modifies the compositional parameters of the absorber layer by incorporating nitrogen into the chromium-based material. This parameter change enhances the EUV absorption efficiency by adjusting the electronic structure and optical properties of the absorber layer.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The absorber layer is designed as a composite material system combining chromium with nitrogen incorporation. This composite structure leverages the beneficial properties of both materials to achieve superior EUV absorption while maintaining structural integrity.

Inventive Principle:

Principle #40Composite materials

3Reliability

If a photo catalytic layer is added for self-cleaning, then the protection against damage improves, but the device complexity increases

Engineering Contradiction:

Improveresistance to manufacturing damageVSAvoidmultilayer structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The photo catalytic layer provides self-service functionality by automatically decomposing organic contaminants through photo catalysis when exposed to EUV radiation. This self-cleaning mechanism eliminates the need for additional manual cleaning steps and provides continuous protection during the manufacturing process.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The photo catalytic layer converts the potentially harmful EUV radiation and organic contaminants into beneficial cleaning action. By utilizing the energy from EUV exposure, the layer activates photo catalytic reactions that decompose contaminants, turning a harmful exposure into a protective cleaning function.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 suppresses damage to the backside conductive layer, enhances EUV absorption, and maintains the reflectivity of the EUV photo mask, improving its performance and durability in extreme ultraviolet lithography systems.

Implementation Method 1

an absorber layer, wherein the absorber layer includes a CrN, or CrON, layer

Methodology Applied

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

Implementation Method 2

a photo catalytic layer for self-cleaning, preventing damage to the capping layer

Methodology Applied

Scientific EffectPhoto catalysis: Catalysis

Data Source

PatentUS11829062B2EUV photo masks and manufacturing method thereof

Publication Date: 2023.11.28 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

In a method of manufacturing a reflective mask, a photo resist layer is formed over a mask blank. The mask blank includes a substrate, a reflective multilayer on the substrate, a capping layer on the reflective multilayer, an absorber layer on the capping layer and a hard mask layer, and the absorber layer is made of Cr, CrO or CrON. The photo resist layer is patterned, the hard mask layer is patterned by using the patterned photo resist layer, the absorber layer is patterned by using the patterned hard mask layer, and an additional element is introduced into the patterned absorber layer to form a converted absorber layer.