Reflective Mask Blank Absorption Film for Fine EUV Pattern Etching

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Solution Overview

Problem

Existing EUV lithography technologies face challenges in forming fine absorption film patterns due to the use of high-absorbent materials with poor processability and low etching rates, leading to shadowing effects and difficulties in electron beam repair etching.

Innovation Solution

A reflective mask blank and mask are designed with an absorption film containing at least 50% tin oxide or indium oxide, mixed with materials easily etched by fluorine-based or chlorine-based gases, allowing for reduced film thickness and improved etching capabilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a material with high extinction coefficient k is used for the absorption film to reduce the shadowing effect, then the EUV light absorptivity is improved and film thickness can be reduced, but the dry etching rate becomes low making it difficult to form fine patterns

Engineering Contradiction:

Improveshadowing effectVSAvoiddry etching processability

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The absorption film uses a composite material comprising a high-absorbent material (such as Ta, W, Pt, Pd, Ir, or their alloys) combined with a material having a high dry etching rate (such as Si, Ge, Sn, Sb, Bi, or their compounds). This composite structure enables both high EUV light absorptivity for reducing the shadowing effect and sufficient dry etching rate for forming fine patterns, resolving the contradiction between optical performance and manufacturability.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If a material with high extinction coefficient k is used for the absorption film to reduce the shadowing effect, then the EUV reflectance is suppressed, but the etching rate becomes extremely low making electron beam repair etching difficult

Engineering Contradiction:

ImproveEUV reflectanceVSAvoidelectron beam repair etching

Core Design Contradiction:

Object-affected harmful factorsVSEase of repair

Solution Approach 1:

The absorption film combines a high-absorbent material (for suppressing EUV reflectance) with a material having a high dry etching rate (such as Si, Ge, Sn, Sb, Bi, or their compounds). This composite structure enables both effective suppression of EUV reflectance for reducing the shadowing effect and sufficient etching rate for enabling electron beam repair etching, resolving the contradiction between optical performance and repairability.

Inventive Principle:

Principle #40Composite materials

3Manufacturing precision

If the absorption film thickness is reduced to minimize the shadowing effect, then the transfer performance is improved, but the pattern formation becomes more difficult due to material processability issues

Engineering Contradiction:

Improvetransfer performanceVSAvoidpattern formation

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The absorption film uses a composite material that provides both high EUV light absorptivity (enabling thin film design for minimal shadowing effect and improved transfer performance) and sufficient dry etching rate (enabling fine pattern formation). The composite structure allows the film to be made thin while maintaining manufacturability, resolving the contradiction between transfer performance and pattern formation capability.

Inventive Principle:

Principle #40Composite materials

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

This design enables the formation of fine absorption film patterns with reduced shadowing effects and enables electron beam repair etching, improving transfer performance and reducing line width errors on wafers.

Implementation Method 1

an absorption film absorbing the EUV light formed on the protective film... the material having a high extinction coefficient k to the EUV... increasing the absorption of the EUV light

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

a reflective film reflecting an EUV light... an optical system member of an exposure machine is not a lens but a mirror... guiding a reflected light reflected at an angle of −6°

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS12510818B2Reflective mask blank and reflective mask

Publication Date: 2025.12.30 TEKSCEND PHOTOMASK CORP

AI summary

There are provided a reflective mask blank in which a fine absorption film pattern is formed even when a high-absorbent material is used as an absorption film of an EUV mask, whereby the shadowing effect can be reduced and electron beam repair etching can be performed and a reflective mask blank for producing the same. A reflective mask blank (10) according to this embodiment includes: a substrate (1); a multi-layer reflective film (2) reflecting an EUV light having a multi-layer structure formed on the substrate (1); a capping layer (3) protecting the multi-layer reflective film (2) formed on the multi-layer reflective film (2); and an absorption film (4) absorbing the EUV light formed on the capping layer (3), in which the absorption film (4) contains 50% by atom or more of elements constituting at least one of tin oxide (SnO) and indium oxide (InO) and contains a material easy to be etched by a fluorine-based gas or a chlorine-based gas.