PLZT Ceramic Films on Copper Foils via Sol-Gel Processing
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Solution Overview
Problem
The challenge is to fabricate high capacitance density ceramic dielectric films on copper foils without oxidation, which is complicated by copper's tendency to form a low-permittivity copper oxide layer, degrading ferroelectric properties, and requires strict control of oxygen partial pressure and specialized gas mixtures.
Innovation Solution
A method involving the application of a sol-gel composition containing ceramic precursors in 2-methoxyethanol on copper substrates, followed by drying, pyrolysis, and crystallization under an inert gas atmosphere, eliminating the need for a buffer layer and specialized gas mixtures, thereby preventing copper oxidation and maintaining high-quality dielectric films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature annealing is performed in air to form desired crystalline phase of high-K ceramic, then dielectric constant is improved, but copper substrate oxidizes forming low-permittivity layer that degrades ferroelectric properties
Solution Approach 1:
The patent applies an inert atmosphere (nitrogen or argon) during high-temperature annealing to prevent copper substrate oxidation. The inert gas displaces oxygen from the processing environment, allowing the copper foil to maintain its metallic state while the ceramic dielectric layer forms its desired crystalline phase at temperatures up to 900°C. This resolves the contradiction by eliminating the harmful oxidation reaction while preserving the beneficial high-temperature crystallization process.
Solution Approach 2:
The patent introduces a buffer layer (such as platinum, palladium, or nickel) between the copper substrate and the ceramic dielectric layer. This intermediary layer serves dual functions: it prevents direct oxidation of the copper substrate during high-temperature processing and also prevents harmful reactions between the copper and the high-K ceramic material. The buffer layer acts as a protective mediator that enables high-temperature annealing while preserving both the substrate integrity and the ferroelectric properties of the dielectric film.
2Object-affected harmful factors
If low oxygen partial pressure is maintained during high temperature annealing to prevent copper oxidation, then copper substrate is protected, but dielectric losses increase due to reduction of dielectric materials
Solution Approach 1:
The patent uses an inert atmosphere (nitrogen or argon) that provides a controlled environment with negligible oxygen partial pressure to prevent copper oxidation during high-temperature annealing. The inert gas does not react with the ceramic dielectric materials, allowing them to maintain their stoichiometry and crystalline structure without reduction. This resolves the contradiction by providing oxygen exclusion for copper protection while simultaneously preventing dielectric material degradation through the chemical inertness of the atmosphere.
3Object-affected harmful factors
If buffer layer is used to prevent copper oxidation, then substrate protection is achieved, but manufacturing complexity increases due to additional deposition steps
Solution Approach 1:
The patent eliminates the need for buffer layers by implementing an inert atmosphere during high-temperature annealing. This single environmental control measure provides substrate protection without requiring additional material deposition steps. The inert gas environment directly prevents copper oxidation during the crystallization process, simplifying the fabrication process by removing the buffer layer deposition step while maintaining substrate protection.
Solution Approach 2:
The patent removes the buffer layer component from the multi-layer structure by using an inert atmosphere approach. Instead of adding an intermediate protective layer, the solution extracts the protection function from the structural layers and implements it through the processing environment. This reduces device complexity by eliminating an entire layer and its associated deposition processes.
4Ease of manufacture
If copper foil is used as substrate instead of Pt/Si, then manufacturing cost is reduced, but copper oxidation occurs during high temperature processing
Solution Approach 1:
The patent enables the use of low-cost copper foil substrates by implementing an inert atmosphere (nitrogen or argon) during high-temperature annealing. The inert gas environment prevents copper oxidation, allowing the copper foil to serve as a stable, low-cost substrate alternative to expensive Pt/Si structures. This resolves the contradiction by providing oxidation protection through environmental control rather than through expensive substrate materials.
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 successfully produces high-quality PLZT ceramic films on copper substrates with high capacitance density, preventing copper oxidation and achieving ferroelectric properties comparable to those on Pt/Si substrates, with improved dielectric constants and reduced dielectric losses.
Implementation Method 1
applying onto a copper substrate a layer of a sol-gel composition comprising a precursor of a ceramic material
Implementation Method 2
drying the layer
Implementation Method 3
pyrolyzing the dried layer to form a ceramic film from the ceramic precursor
Implementation Method 4
crystallizing the ceramic film
Implementation Method 5
high temperature annealing for formation of the desired crystalline phase
Implementation Method 6
preventing copper oxidation
Data Source
AI summary
The present invention provides copper substrate coated with a lead-lanthanum-zirconium-titanium (PLZT) ceramic film, which is prepared by a method comprising applying a layer of a sol-gel composition onto a copper foil. The sol-gel composition comprises a precursor of a ceramic material suspended in 2-methoxyethanol. The layer of sol-gel is then dried at a temperature up to about 250° C. The dried layer is then pyrolyzed at a temperature in the range of about 300 to about 450° C. to form a ceramic film from the ceramic precursor. The ceramic film is then crystallized at a temperature in the range of about 600 to about 750° C. The drying, pyrolyzing and crystallizing are performed under a flowing stream of an inert gas.