Reticle EUV Cleaning to Control Lithography CD Uniformity

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Solution Overview

Problem

The buildup of particles and hydrocarbon contamination on reticles during lithographic processes leads to non-uniform critical dimensions (CD) in the pattern produced on the photo resist layer of wafers, which can degrade the masks and cause uniformity issues.

Innovation Solution

Irradiating the surface of reticles with EUV radiation for a predetermined time to decompose particles and hydrocarbon contamination without damaging the reticle structure, using a separate exposure device with a different radiation source to maintain CD uniformity (CDU) before performing lithography.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If reticles are stored under vacuum condition, then contamination is prevented, but particles and hydrocarbon contamination still build up during lithographic processes

Engineering Contradiction:

Improvereticle cleanlinessVSAvoidlithographic process continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies preliminary action by irradiating the reticle surface with EUV radiation before the lithographic process to decompose and remove particles and hydrocarbon contamination. This pre-cleaning action ensures the reticle surface is free from contaminants that would otherwise degrade mask performance and cause non-uniform critical dimensions during the lithographic process.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If contamination is removed by traditional cleaning methods, then mask defect impact is reduced, but additional particles may be introduced

Engineering Contradiction:

ImproveCD uniformityVSAvoidparticle introduction

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces traditional mechanical or chemical cleaning methods with EUV radiation-based decomposition. Instead of using physical contact or chemical solvents that may introduce new particles, the EUV radiation chemically decomposes contaminants into volatile species that are removed without contact, thereby maintaining CD uniformity without introducing additional particles.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the state of contamination from solid/adsorbed particles to gaseous volatile species through EUV radiation-induced decomposition. This parameter change in the physical state allows contaminants to be removed through evaporation/sublimation without mechanical contact, preventing particle introduction while achieving thorough cleaning.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If EUV radiation is used to clean reticle surface, then contamination is decomposed, but reticle structure may be damaged

Engineering Contradiction:

ImproveCD uniformityVSAvoidreticle structure integrity

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies local quality by selectively irradiating only the reticle surface where contamination exists, while leaving the bulk reticle structure unexposed. The EUV radiation is applied locally to decompose particles and hydrocarbons on the surface, maintaining the structural integrity of the reticle substrate and underlying layers while achieving effective cleaning.

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

This method effectively reduces the impact of contamination on reticles, ensuring optimal CDU without introducing additional particles or causing structural damage, thus improving the precision of the lithographic process.

Implementation Method 1

Irradiating the surface of reticles with EUV radiation for a predetermined time to decompose particles and hydrocarbon contamination

Methodology Applied

Scientific EffectPhotodissociation: Photodissociation

Data Source

PatentUS20250216804A1Reduce mask defect impact by contamination decompose

Publication Date: 2025.07.03 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method comprises cleaning a surface of a reticle by irradiating the surface of the reticle in a first exposure device for a predetermined irradiation time. A layout pattern of the reticle is projected onto a photo resist layer of a wafer in a second exposure device by an EUV radiation. The photo resist layer is developed to generate a photo resist pattern on the wafer. A surface of the wafer is imaged to generate an image of the photo resist pattern on the wafer. The generated image of the photo resist pattern is analyzed to determine critical dimension uniformity (CDU) of the photo resist pattern. The predetermined irradiation time is adjusted until the determined CDU satisfies a predetermined criterion.