Substrate Cleaning via Freeze Phase Transition

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Solution Overview

Problem

Current cleaning methods for substrates in imprint lithography, such as alkaline and acidic cleaning, are inadequate in removing small particles of 15 nm or less from patterned surfaces, resulting in uneven removal efficiencies for inorganic and organic particles, which can lead to pattern defects in semiconductor devices.

Innovation Solution

A method involving a two-step cleaning process: initial alkaline or acidic cleaning followed by freeze cleaning, where the surface tension of a liquid is regulated with a surfactant or alcohol to enhance the removal of small particles by allowing the liquid to permeate and lift particles off the surface during freezing and thawing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional cleaning methods are used, then the cleaning process is simple, but the patterned surface cleanliness is insufficient for high-precision imprint lithography

Engineering Contradiction:

Improvecleaning process complexityVSAvoidpatterned surface cleanliness

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The cleaning process is divided into multiple sequential steps: first alkaline cleaning to remove inorganic particles, then acidic cleaning, and finally freeze cleaning with regulated surface tension liquid to remove organic particles. Each step targets specific particle types, achieving comprehensive removal that a single method cannot accomplish.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The freeze cleaning method utilizes phase transition of the cleaning liquid from liquid to solid and back to liquid. The regulated surface tension liquid is frozen at controlled rates, causing expansion that lifts organic particles from the patterned surface, then thawed to allow particle removal, achieving high cleanliness without complex mechanical intervention.

Inventive Principle:

Principle #36Phase transitions

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 significantly improves the removal efficiency of both inorganic and organic particles, achieving a higher degree of cleanliness on the substrate surface, with increased removal efficiency for organic particles and maintaining high efficiency for inorganic particles, thus reducing pattern defects.

Implementation Method 1

the surface tension of a liquid is regulated with a surfactant or alcohol to enhance the removal of small particles by allowing the liquid to permeate and lift particles off the surface during freezing and thawing

Methodology Applied

Scientific EffectSurface tension: Surface Tension

Implementation Method 2

allowing the liquid to permeate and lift particles off the surface during freezing and thawing

Methodology Applied

Scientific EffectFreezing: Freezing

Implementation Method 3

during freezing and thawing

Methodology Applied

Scientific EffectPhase change: Phase Change

Data Source

PatentUS11264233B2Method for cleaning substrate and substrate processing apparatus

Publication Date: 2022.03.01 KIOXIA CORP

AI summary

According to one embodiment, a method for cleaning a substrate includes first cleaning process and second cleaning process. The first cleaning process subjects a substrate to a first cleaning method. The second cleaning process subjects the substrate to a second cleaning method that is different from the first cleaning method and is subsequent to the first cleaning process. The first cleaning method includes at least one of acidic cleaning or alkaline cleaning. The second cleaning method includes freeze cleaning.