Magnetron Sputtering Cathode Assembly for Uniform Coating
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Solution Overview
Problem
Existing magnetron sputtering apparatuses face issues with overheating of permanent magnets due to thermal radiation, leading to loss of magnetic properties and failure, and struggle with uniform coating thickness on curvilinear surfaces, especially when operating under high temperature loads and complex shapes.
Innovation Solution
A multifunctional cathode assembly for unbalanced magnetron sputtering with a liquid-cooled casing and Z-shaped shield to protect magnets from thermal radiation, combined with a coaxial vacuum-sealed rotary feedthrough for target cleaning and preheating, and deformed coaxial toroids for magnetic and cooling systems to maintain magnetic field strength and achieve curvilinear target shape, enabling operation in DSSD mode and uniform coating on complex surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If permanent magnets are placed on the periphery of the target to create the required magnetic field configuration, then the magnetic field strength and DSSD mode operation are improved, but the magnets are exposed to thermal radiation from the target and chamber fitments, causing overheating and loss of magnetic properties
Solution Approach 1:
A liquid-cooled casing is introduced as an intermediary element between the permanent magnets and the thermal radiation sources (target and chamber fitments). The casing contains internal cooling channels through which a coolant circulates, actively removing heat from the magnets and preventing overheating while allowing the magnets to maintain their required peripheral positioning for generating the magnetic field
Solution Approach 2:
The thermal radiation that would otherwise harm the magnets by causing overheating is converted into a beneficial cooling process. The liquid cooling system uses the thermal energy from the magnets to drive coolant circulation, and the cooled casing simultaneously serves as a structural component of the magnetron assembly
2Productivity
If the target-to-substrate distance is increased to coat large and complex shape parts, then the coating area and productivity are improved, but the substrate ion current density decreases and coating quality deteriorates
Solution Approach 1:
The DSSD mode creates a feedback mechanism where the bottle-shaped magnetic field configuration maintains a stable plasma discharge region that continuously generates ions. This ion flux is sustained regardless of target-to-substrate distance, providing automatic compensation that maintains coating quality even when the distance is increased to accommodate large substrates
3Device complexity
If a flat base and target are used for simplicity, then the device complexity is reduced, but the coating thickness uniformity on curvilinear surfaces deteriorates
Solution Approach 1:
The base and target are designed with curved surfaces matching the curvilinear shape of the workpiece. This curvature allows the target to conform to the complex geometry of the substrate, ensuring uniform coating thickness distribution across the entire surface area, including recesses and protrusions, while maintaining a relatively simple overall device structure
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
Prevents demagnetization of permanent magnets, allows for effective cleaning and preheating without contamination, and ensures high uniformity of coating thickness on complex shapes, enhancing the reliability and performance of the magnetron sputtering apparatus under high temperature conditions.
Implementation Method 1
protect magnets from thermal radiation
Implementation Method 2
liquid-cooled casing
Implementation Method 3
magnetic system...in the form of deformed coaxial toroids...to maintain magnetic field strength
Implementation Method 4
target cleaning and preheating
Implementation Method 5
magnetron sputtering apparatus
Implementation Method 6
application of coatings
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present invention relates to a magnetron sputtering cathode assembly. The assembly consists of a body in the form of a rectangular cuboid (1) with a base (2), an extended flat target (3) containing a sputtered material and fixed to the base (2) of the body, as well as a magnetic system (4) and a cooler (5) in the form of coaxial toroids located between the base (2) of the body and the flat target (3) in the centre of the body, wherein the central region of the flat target (3) is perforated with holes or slits (6) along its extended side, wherein at the centre of the body an additional gas distribution system (7) is installed, and wherein the peripheral magnetic system is mounted to the base (2) on ferromagnetic supports (8).