Liquid Immersion Exposure Member Cleaning via Alkali and Hydrogen Peroxide

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Solution Overview

Problem

In liquid immersion exposure methods for photolithography, foreign substances adhering to members in contact with the liquid can lead to contamination, compromising exposure accuracy and the performance of these members, ultimately affecting the quality of the mask pattern image.

Innovation Solution

A method involving sequential cleaning of members with an alkali solution followed by a hydrogen peroxide solution, utilizing ultrasonic waves to effectively remove contaminants and prevent re-adhesion, thereby maintaining the cleanliness and performance of the members in contact with the liquid.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If members in contact with liquid are used during exposure, then exposure process can be performed, but foreign substances may adhere to the members causing contamination

Engineering Contradiction:

Improveexposure process capabilityVSAvoidforeign substance adhesion

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by cleaning the nozzle member with alkali solution and hydrogen peroxide solution before exposure to prevent foreign substance adhesion. This preventive cleaning approach ensures the member starts in a clean state, addressing the contamination issue before it affects exposure quality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the chemical parameters of the cleaning process by using specific solutions (alkali solution with pH 11-14 and hydrogen peroxide solution with concentration 0.1-30%) and controlling cleaning conditions (temperature 20-80°C, time 1-60 minutes). These parameter changes optimize the cleaning effectiveness to remove contaminants while preventing re-adhesion.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If members are cleaned frequently to maintain cleanliness, then exposure accuracy is maintained, but cleaning time and operational complexity increase

Engineering Contradiction:

Improveexposure accuracyVSAvoidcleaning time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent optimizes cleaning parameters (solution concentration, temperature, time) to achieve effective cleaning in reduced time. By using alkaline solutions with pH 11-14 and controlling cleaning duration to 1-60 minutes at 20-80°C, the process maintains exposure accuracy while minimizing time loss.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements continuous cleaning action through sequential treatment with alkali solution followed by hydrogen peroxide solution. This continuous multi-stage cleaning process ensures thorough contamination removal in a single integrated operation, maintaining exposure accuracy without requiring multiple separate cleaning cycles.

Inventive Principle:

Principle #20Continuity of useful action

3Device complexity

If conventional cleaning methods are used, then simple process is maintained, but contaminants are not effectively removed and liquid contamination occurs

Engineering Contradiction:

Improvecleaning process simplicityVSAvoidliquid contamination

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the cleaning process into two distinct stages: first cleaning with alkali solution to remove organic contaminants, then cleaning with hydrogen peroxide solution to remove inorganic contaminants and prevent re-adhesion. This segmentation addresses different contamination types effectively while maintaining a relatively simple overall process structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the chemical composition parameters of cleaning solutions from conventional single-solution methods to a two-solution system with specific pH and concentration ranges. This parameter change enables effective removal of diverse contaminants and prevention of liquid contamination without significantly complicating the cleaning procedure.

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 cleaning method ensures the removal of contaminants from members, preventing liquid contamination and maintaining exposure accuracy, thus extending the period before re-cleaning is required and ensuring consistent performance in liquid immersion exposure processes.

Implementation Method 1

cleaning the member with an alkali solution

Methodology Applied

Scientific EffectSaponification: Hydrolysis

Implementation Method 2

cleaning the member with an alkali solution followed by cleaning the member with a solution including hydrogen peroxide

Methodology Applied

Scientific EffectChemical dissolution: Solvation

Implementation Method 3

cleaning the member with a solution including hydrogen peroxide

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 4

utilizing ultrasonic waves to effectively remove contaminants and prevent re-adhesion

Methodology Applied

Scientific EffectUltrasonic cavitation: Acoustic Cavitation

Data Source

PatentUS8619231B2Cleaning method, exposure method, and device manufacturing method

Publication Date: 2013.12.31 NIKON CORP

AI summary

A cleaning method includes cleaning a member, used at the time of exposing a substrate via liquid, which is in contact with the liquid. The method includes cleaning the member with an alkali solution followed by cleaning the member with a solution including hydrogen peroxide.