ALD Transparent Conducting Oxide Films Using Cyclopentadienyl Indium
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Solution Overview
Problem
Current atomic layer deposition (ALD) processes for indium oxide (In2O3) and indium-tin oxide (ITO) face limitations such as high growth temperatures, low growth rates, equipment damage from corrosive byproducts, and inability to coat nanoporous materials effectively, particularly due to the use of InCl3 and ozone precursors which lead to thickness and composition non-uniformities.
Innovation Solution
A method using cyclopentadienyl indium and tetrakis(dimethylamino) tin as precursors, combined with multiple oxidizing or reducing agents like oxygen and water, to enhance the growth rate and conductivity of transparent conducting oxide (TCO) films, allowing deposition on high aspect ratio and porous substrates at lower temperatures with improved uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If InCl3 is used as precursor for ALD deposition of indium oxide, then the deposition process can be performed, but the growth rate is low (0.25-0.40 Å/cycle) and high growth temperatures (300-500°C) are required
Solution Approach 1:
The patent changes the chemical parameters of the precursor system by replacing InCl3 with alternative indium precursors that have different volatility and reactivity characteristics, enabling deposition at lower temperatures while maintaining or improving growth rate
Solution Approach 2:
The patent employs composite precursor systems combining organometallic indium compounds with specific ligands, creating materials with optimized properties that balance volatility for low-temperature deposition and reactivity for high growth rates
2Ease of manufacture
If InCl3 is used as precursor, then deposition can proceed, but corrosive HCl byproduct damages deposition equipment
Solution Approach 1:
The patent eliminates the harmful HCl byproduct generation by using alternative precursor chemistries that produce benign byproducts, converting a harmful manufacturing process into a environmentally friendly one while maintaining deposition effectiveness
Solution Approach 2:
The patent extracts and removes the problematic chlorine component from the precursor system, replacing InCl3 with chlorine-free alternatives that do not generate corrosive HCl during deposition
3Adaptability or versatility
If InCl3 is used for coating nanoporous materials, then deposition can occur, but the long precursor exposures required to coat nanoporous materials completely remove the In2O3 from the outer portions
Solution Approach 1:
The patent changes the reactivity parameters of the precursor system to achieve self-limiting surface reactions that prevent over-exposure damage, allowing uniform coating of nanoporous materials with controlled film thickness
Solution Approach 2:
The patent introduces intermediary surface species and controlled reaction pathways that mediate between precursor adsorption and oxide formation, preventing direct etching of the deposited In2O3 while still allowing complete penetration into nanoporous structures
4Productivity
If ozone is used as oxidizing precursor, then acceptable growth rate (1.3 Angstrom per cycle) is achieved, but thickness and composition non-uniformities occur over large substrate areas
Solution Approach 1:
The patent introduces water vapor as an intermediary oxidizing agent that mediates the oxidation process, providing more uniform oxygen delivery across large substrate areas compared to direct ozone exposure, thereby reducing thickness non-uniformities
Solution Approach 2:
The patent changes the physical state and delivery mechanism of the oxidizing agent from gaseous ozone to vapor-phase water, improving diffusion characteristics and uniformity of oxidation across large substrate areas while maintaining acceptable growth rates
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 achieves a high growth rate of at least 1 Angstrom per cycle, reduces thickness non-uniformity to less than 3%, and enables deposition on various substrates, including nanoporous materials, with enhanced conductivity and optical properties, suitable for applications in flat panel displays and photovoltaics.
Implementation Method 1
A method is described for producing light transmitting (including light transparent) and highly conducting oxides using atomic layer deposition (ALD)
Implementation Method 2
reacting a first metal precursor with a first oxidizing reactant and a second oxidizing reactant to form a monolayer of indium oxide
Implementation Method 3
indium-tin oxide (ITO) has found wide application in flat panel displays, solar glass, and energy efficient window coatings. Significantly, ITO exhibits a combination of excellent optical and transport properties
Data Source
AI summary
A method of preparing light transmitting conducting metal oxide (TCO) films using atomic layer deposition (ALD) of a metal precursor multiple oxidizing reactants. The multiple metal oxidizing reactants may be selected to enhance growth of the TCO film. In a particular embodiment, an indium oxide TCO film is prepared using a cyclopentadienyl indium precursor and a combination of water and oxygen.