Doped Ruthenium Capping Layer for EUV Mask Carbon Deposition

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In extreme ultraviolet lithography, hydrocarbon-containing gases in the vacuum environment lead to unwanted cross-linking with the ruthenium capping layer, causing carbon deposition and degrading the critical dimension of patterns on photoresist-coated substrates.

Innovation Solution

Doping the ruthenium capping layer with halogen, pentavalent, or hexavalent elements to form a stable coordination complex that prevents cross-linking with hydrocarbon fragments, thereby maintaining pattern integrity and preventing carbon deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a ruthenium capping layer is used in EUV lithography, then the multilayer stack provides good reflectivity, but hydrocarbon-containing gases cause cross-linking with the ruthenium layer leading to carbon deposition and pattern degradation

Engineering Contradiction:

Improvereflectivity of multilayer stackVSAvoidcarbon deposition on capping layer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A protective capping layer comprising alternating Mo/Si layers is introduced as an intermediary between the ruthenium layer and the hydrocarbon-containing environment. This capping layer acts as a barrier that prevents direct interaction between hydrocarbon fragments and the ruthenium, thereby eliminating carbon deposition while preserving the optical properties of the underlying multilayer stack.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The solution employs a composite structure where a Mo/Si capping layer is combined with the Ru-based multilayer stack. This composite material approach allows the system to benefit from both the high reflectivity of ruthenium and the protective properties of the Mo/Si capping layer, resolving the contradiction between maintaining optical performance and preventing harmful cross-linking reactions.

Inventive Principle:

Principle #40Composite materials

2Productivity

If hydrocarbon-containing gases are present in the vacuum environment, then the EUV lithography process can proceed, but unwanted cross-linking occurs degrading critical dimension of patterns

Engineering Contradiction:

ImproveEUV lithography process capabilityVSAvoidcritical dimension of patterns

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The protective Mo/Si capping layer is applied in advance to the ruthenium surface before exposure to hydrocarbon-containing gases during EUV lithography. This preliminary protective action prevents the harmful cross-linking reaction from occurring, thereby maintaining pattern critical dimensions while allowing the lithography process to proceed normally.

Inventive Principle:

Principle #9Preliminary anti-action

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

Prevents unwanted carbon deposition on the ruthenium capping layer, maintaining pattern integrity and reducing critical dimension degradation in EUV lithography processes.

Implementation Method 1

doping the ruthenium capping layer with the dopant to form a stable coordination complex

Methodology Applied

Scientific EffectCoordination complex formation: Chemical Bonding

Data Source

PatentUS12072633B2Extreme ultraviolet lithography method, extreme ultraviolet mask and formation method thereof

Publication Date: 2024.08.27 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method of forming an extreme ultraviolet (EUV) mask includes forming a multilayer Mo/Si stack comprising alternating stacked Mo and Si layers over a mask substrate; forming a ruthenium capping layer over the multilayer Mo/Si stack; doping the ruthenium capping layer with a halogen element, a pentavalent element, a hexavalent element or combinations thereof; forming an absorber layer over the ruthenium capping layer; and etching the absorber layer to form a pattern in the absorber layer.