Supercritical Precursor Spraying for Uniform Nanometer Thin Films
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Solution Overview
Problem
Conventional methods for depositing thin films on substrates, such as chemical vapor deposition and ultrasonic atomizing, face challenges in achieving continuous, nanometer-thick coatings due to surface tension and convective boundary layers, leading to uneven surfaces and inadequate film formation.
Innovation Solution
A system comprising a spraying module and a plasma reactor uses a supercritical carrier fluid to deposit a precursor mixture onto a substrate, with the plasma reactor generating radicals to counteract convective boundary layers and transform the sprayed layer into a solid film, allowing for precise control of film formation and removal of non-chemisorbed molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional atomizing nozzles are used to spray precursor, then droplet size can be adjusted by varying gas or liquid pressure, but the surface tension and uneven exposure result in uneven surfaces and inadequate continuous film formation
Solution Approach 1:
The patent changes the physical state of the carrier fluid from liquid to supercritical state, which fundamentally alters the spraying characteristics. Supercritical CO2 eliminates surface tension effects and produces uniform sub-10-micron droplets, resolving the contradiction between film uniformity and droplet control
Solution Approach 2:
The patent utilizes phase transition of CO2 from supercritical state to gas state after deposition. The supercritical fluid carries precursor uniformly, then transitions to gas leaving behind uniform film, solving the film formation problem while maintaining operational simplicity
2Manufacturing precision
If ultrasonic atomizing nozzle is used to produce small droplets, then droplet size is governed by vibration frequency, but the droplets form non-continuous and non-fully covered coating on substrate
Solution Approach 1:
The patent changes the carrier fluid to supercritical CO2, which has unique properties that enable both fine droplet formation and complete substrate coverage. The supercritical state provides low viscosity and high diffusivity, ensuring continuous coating while maintaining precise droplet size control
Solution Approach 2:
Supercritical CO2 acts as an intermediary carrier that delivers precursor uniformly across the substrate. It mediates between the spray system and substrate, ensuring continuous coverage while allowing precise control of deposition parameters
3Strength
If substrate is placed at high temperature for pyrolysis to convert sprayed coatings into solid film, then good mechanical and electrical properties are obtained, but convecting boundary layer rises and prevents light droplets from reaching substrate
Solution Approach 1:
The patent changes the carrier fluid to supercritical CO2, which produces extremely fine droplets that can penetrate the convecting boundary layer at high temperatures. The low viscosity and high diffusivity of supercritical CO2 enable efficient droplet delivery even in strong convection conditions
Solution Approach 2:
The patent uses phase transition of CO2 from supercritical to gas state, and the precursor from liquid/gas to solid film state. This allows deposition at high temperatures while maintaining droplet delivery efficiency, as the phase change occurs rapidly upon contact with the hot substrate
4Manufacturing precision
If multiple rounds of spray are performed to achieve continuous film, then film coverage is improved, but process time and complexity increase
Solution Approach 1:
The patent changes to supercritical CO2 as carrier fluid, which enables single-pass continuous film deposition. The unique properties of supercritical CO2 (low viscosity, high diffusivity, no surface tension) allow complete substrate coverage in one spray pass, eliminating the need for multiple rounds and reducing process time
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 enables the formation of continuous, thin films of nanometer thickness by overcoming surface tension and convective boundary layer issues, resulting in improved mechanical and electrical properties of the deposited films.
Implementation Method 1
The spraying module sprays a mixture of precursor and a supercritical carrier fluid onto the substrate
Implementation Method 2
expose the precursor for absorbing molecules as a source of the spraying film
Implementation Method 3
The plasma reactor exposes the substrate at a temperature below 150° C. to counteract the effects of a convecting boundary layer injected with the mixture to post-spraying radicals
Implementation Method 4
generating post-spraying radicals to transform the sprayed layer into a solid layer
Implementation Method 5
Due to the motion of fluids (e.g., ambient gas) on a hot surface of the substrate, hot fluid surrounding a hot substrate rises and forms convecting boundary layer over the substrate
Implementation Method 6
When using the spray, the liquid precursor forms droplets on the substrate due to the surface tension
Data Source
AI summary
Embodiments relate to surface treating a substrate, spraying precursor onto the substrate using supercritical carrier fluid, and post-treating the substrate sprayed with the precursor to form a layer with nanometer thickness of material on the substrate. A spraying assembly for spraying the precursor includes one or more spraying modules and one or more radical injectors at one or more sides of the spraying module. A differential spread mechanism is provided between the spraying module and the radical injectors to inject spread gas that isolates the sprayed precursor and radicals generated by the radical injectors. As relative movement between the substrate and the spraying assembly is made, portions of the substrate is exposed to first radicals, sprayed with precursors either one of the spraying modules or both spraying modules using supercritical carrier fluid, and then exposed to second radicals again.