Multilayer Coating Optical Loss Reduction via Segmented Sputtering and Plasma Oxidation
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Solution Overview
Problem
Existing methods for producing thin coatings, particularly multilayer coatings with specific optical properties, face challenges in controlling composition and achieving low optical losses due to complex interdependencies of process parameters and material systems, leading to inconsistent results and high optical losses.
Innovation Solution
A method involving controlled substoichiometric reactive sputtering followed by plasma treatment to achieve stoichiometric oxidation, with a specific interface structure to minimize optical losses, using a dual-cathode sputtering system and plasma source to deposit layers with precise control over reactive components like oxygen, ensuring high-quality coatings with low optical reflection and high transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reactive sputtering is used to deposit oxide coatings, then the coating composition can be controlled, but the process parameters become complex and hard to predict due to competing ablation and oxidation processes on the target surface
Solution Approach 1:
The patent divides the coating process into two separate stages: (1) depositing a metallic or sub-stoichiometric oxide layer using sputtering, and (2) subsequently oxidizing the layer to achieve stoichiometric composition using a plasma source. This segmentation separates the deposition and oxidation processes, allowing independent optimization of each step and avoiding the complex interdependencies that occur when both processes occur simultaneously in reactive sputtering.
Solution Approach 2:
The patent performs the sputtering deposition of the coating layer before the oxidation step. By first depositing the metallic or sub-stoichiometric layer and then oxidizing it in a subsequent plasma treatment step, the process establishes the base coating structure beforehand, allowing precise control over the final stoichiometric composition without the unpredictable competing processes of simultaneous reactive sputtering.
2Adaptability or versatility
If multiple layers with special functional properties are deposited, then the optical functionality is improved, but the mutual influence of coating parameters makes the process harder to control
Solution Approach 1:
The patent applies the two-stage process (sputtering deposition followed by plasma oxidation) to each layer of the multilayer coating system independently. This allows each layer's thickness, composition, and optical properties to be controlled separately through its own deposition and oxidation parameters, preventing mutual interference between layers and enabling precise control of the overall multilayer optical functionality.
Solution Approach 2:
The patent allows different layers in the multilayer coating to have different properties by controlling the sputtering and oxidation parameters specific to each layer. Each layer can be optimized with its own thickness, stoichiometry, and refractive index through independent process control, enabling tailored optical functionality for each layer while maintaining overall system precision.
3Quantity of substance
If DC magnetron sputtering with reactive gas is used, then metallic compounds can be deposited, but flashovers and cathode arcing occur that disrupt the coating process
Solution Approach 1:
The patent separates the deposition process (using DC or pulsed DC magnetron sputtering with controlled reactive gas) from the oxidation process (using a separate plasma source). This segmentation allows the sputtering step to deposit the metallic compound layer without the instability of reactive sputtering, while the subsequent plasma oxidation step achieves the desired stoichiometric composition without causing flashovers or arcing during deposition.
Solution Approach 2:
The patent introduces a plasma source as an intermediary step between sputtering deposition and final oxide formation. The plasma source provides a controlled oxidation environment that converts the deposited metallic or sub-stoichiometric layer into stoichiometric oxide without the harmful effects of reactive sputtering, thereby ensuring process stability and reliability.
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 production of coatings with minimal optical losses and high precision, achieving excellent optical quality by controlling the stoichiometry and structure of multilayer coatings, reducing the impact of interface effects and maintaining optimal refractive indices across layers.
Implementation Method 1
by using an electrical field from which ions are accelerated against a target that is at a high electrical cathode potential, and these ions knock atoms out of the target which then deposit themselves on the walls of the vacuum chamber and on a substrate
Implementation Method 2
In the area B the content of the component O2 is increased in situ in coating 1, by means of plasma acting on coating 1
Data Source
AI summary
A method for reducing the optical loss of the multilayer coating below a predetermined value in a zone by producing coating on a displaceable substrate in a vacuum chamber with the aid of a residual gas using a sputtering device. Reactive depositing a coating on the substrate by adding a reactive component with a predetermined stoichiometric deficit in a zone of the sputtering device. Displacing the substrate with the deposited coating into the vicinity of a plasma source, which is located in the vacuum chamber at a predetermined distance from the sputtering device. The plasma action of the plasma source modifying the structure and/or stoichiometry of the coating, preferably by adding a predetermined quantity of the reactive component to reduce the optical loss of the coating.