Metal Oxide Fine Particle Array Formation on Silicon Substrate

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Solution Overview

Problem

Conventional methods for forming fine particle arrays on substrates face issues with reoxidation of metal atom aggregates due to exposure to atmospheric air, leading to difficulties in fulfilling desired functions, especially during the lamination of insulating layers.

Innovation Solution

A method involving the steps of fixing metal oxide fine particles and protein complexes on a substrate, removing the hollow protein, laminating an insulating layer with a specific film thickness, and subjecting the substrate to a heat treatment in a reducing atmosphere to suppress reoxidation, using an insulating layer with a lower standard free energy of formation than the metal oxide fine particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If metal oxide fine particles are reduced to metal atom aggregates and then exposed to atmospheric air, then the reduction process is completed, but reoxidation occurs causing the metal atom aggregates to return to metal oxide state

Engineering Contradiction:

Improvestability of reduced fine particlesVSAvoidreoxidation from atmospheric air

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

An insulating layer is introduced as an intermediary barrier between the reduced metal fine particles and the atmospheric air. This insulating layer prevents direct contact between oxygen in the air and the reduced metal particles, thereby preventing reoxidation while allowing the particles to maintain their reduced functional state

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The insulating layer creates an inert protective environment around the reduced metal fine particles, isolating them from the reactive atmospheric air. This inert barrier ensures the particles remain in their reduced state without undergoing reoxidation, maintaining their desired functionality

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

2Reliability

If the insulating layer is formed before reduction treatment, then reoxidation is suppressed, but the insulating layer may be reduced along with the metal oxide fine particles

Engineering Contradiction:

Improveprotection from reoxidationVSAvoidintegrity of insulating layer

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The standard free energy of formation parameter is used to select insulating layer materials that are thermodynamically stable against reduction under the reduction treatment conditions. By choosing materials with lower standard free energy of formation than the metal oxide fine particles, the insulating layer remains intact while the metal oxide is reduced

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The insulating layer acts as a sacrificial protective barrier that can be temporarily present during the reduction process to prevent reoxidation, then removed or replaced in subsequent processing steps. This disposable protective layer enables the reduction to proceed without compromising the final device structure

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of manufacture

If conventional reduction methods are used without insulating layer protection, then the process is simple, but reoxidation occurs during lamination of insulating layers

Engineering Contradiction:

Improvesimplicity of reduction processVSAvoidfunctional stability after lamination

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The insulating layer is formed on the substrate before the reduction treatment of metal oxide fine particles. This preliminary formation of the insulating layer creates a protective environment that prevents reoxidation during subsequent lamination processes, ensuring the reduced particles maintain their functional state throughout manufacturing

Inventive Principle:

Principle #10Preliminary 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

This approach effectively prevents reoxidation and deterioration of metal oxide fine particles, ensuring stability and functionality of the semiconductor elements by reducing the metal oxide fine particles after forming the insulating layer, thus maintaining their reduced state even in ambient air.

Implementation Method 1

laminating an insulating layer having a film thickness of 3 nm or greater and 100 nm or less, which is hardly reduced compared to the metal oxide fine particles

Methodology Applied

Scientific EffectStandard free energy of formation:

Implementation Method 2

reducing the metal oxide fine particles by subjecting the substrate, on which the insulating layer was laminated in the step C, to a heat treatment in a reducing atmosphere

Methodology Applied

Scientific EffectReduction: Reduction

Data Source

PatentUS7419529B2Method of forming fine particle array on substrate and semiconductor element

Publication Date: 2008.09.02 PANASONIC HOLDINGS CORP

AI summary

An object of the present invention is to provide a method of forming fine particles on a substrate in which reoxidization of reduced fine particles is suppressed. Reduced fine particles (FeO fine particles) are formed by embedding metal oxide fine particles (Fe2O3 fine particles) fixed on a p type silicon semiconductor substrate into a silicon oxidized film, and carrying out a heat treatment in a reducing gas atmosphere. Presence of the silicon oxidized film enables suppression of reoxidization of the reduced fine particles (FeO fine particles) due to exposure to the ambient air.