EUV Reflective Mask Absorber Film Hydrogen Gradient

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Solution Overview

Problem

In EUV lithography, the absorber pattern on reflective masks can peel off when exposed to a hydrogen gas atmosphere during EUV exposure, due to the absorption of hydrogen gas by the absorber pattern, leading to increased compressive stress and crack formation.

Innovation Solution

Incorporating hydrogen into the absorber film in advance to prevent new atomic hydrogen from entering and causing stress, and varying the hydrogen content in the film thickness direction to prevent peeling while avoiding thickening of the absorber film.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the absorber pattern is exposed to hydrogen gas atmosphere during EUV exposure, then the EUV exposure process can proceed, but the absorber pattern peels off due to hydrogen absorption and increased compressive stress

Engineering Contradiction:

ImproveEUV exposure capabilityVSAvoidabsorber pattern adhesion

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by incorporating hydrogen into the absorber film during the film formation process before EUV exposure. This pre-incorporation of hydrogen prevents additional hydrogen absorption during exposure that would otherwise cause compressive stress and peeling. The absorber film is prepared in advance with controlled hydrogen content to avoid subsequent damage during the exposure process.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If hydrogen is incorporated into the absorber film to prevent peeling, then absorber pattern stability improves, but the absorber film may thicken

Engineering Contradiction:

Improveabsorber pattern stabilityVSAvoidabsorber film thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent applies parameter changes by precisely controlling the hydrogen concentration and distribution within the absorber film. Instead of simply adding hydrogen, the invention optimizes the hydrogen content parameter and its spatial distribution to achieve peeling prevention while maintaining appropriate film thickness. The hydrogen concentration is adjusted as a controllable parameter during film formation to balance stability and thickness requirements.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by creating non-uniform hydrogen distribution within the absorber film structure. The hydrogen concentration varies at different depths or regions of the absorber film, with higher concentrations near the interface where peeling is most problematic. This localized hydrogen incorporation provides targeted stress management without requiring uniform thickening of the entire absorber film.

Inventive Principle:

Principle #3Local quality

3Reliability

If the absorber film thickness is increased to prevent peeling, then adhesion stability improves, but the manufacturing precision of fine patterns deteriorates

Engineering Contradiction:

Improveadhesion stabilityVSAvoidfine pattern accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by shifting from a thickness-based solution to a composition-based solution. Instead of increasing absorber film thickness to improve adhesion, the invention changes the chemical composition parameter by incorporating hydrogen at controlled concentrations. This allows maintaining thin film dimensions necessary for fine pattern accuracy while achieving improved adhesion stability through compositional modification.

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

This approach effectively suppresses the peeling of the absorber pattern and prevents thickening of the absorber film, ensuring stable performance during EUV exposure in hydrogen gas atmospheres.

Implementation Method 1

an absorber layer that absorbs EUV light

Methodology Applied

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

Implementation Method 2

a multilayer reflective film that reflects exposure light

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS12313968B2Reflective mask blank, reflective mask, and method for manufacturing semiconductor device

Publication Date: 2025.05.27 HOYA CORPORATION

AI summary

A reflective mask blank for manufacturing a reflective mask capable of suppressing peeling of an absorber pattern while suppressing an increase in the thickness of an absorber film when EUV exposure is conducted in an atmosphere including hydrogen gas. A reflective mask blank comprises a substrate, a multilayer reflection film on the substrate, and an absorber film on the multilayer reflection film. The reflective mask blank is characterized in that: the absorber film includes an absorption layer and a reflectance adjustment layer; the absorption layer contains tantalum (Ta), nitrogen (N), and at least one added element selected from hydrogen (H) and deuterium (D); the absorption layer includes a lower surface region including a surface on the substrate side, and an upper surface region including a surface on the side opposite to the substrate; and the concentration (at. %) of the added element in the lower surface region and the concentration (at. %) of the added element in the upper surface region are different.