Rotatable Magnetron Shutter for Mixed Mode Deposition
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Solution Overview
Problem
Existing coating technologies face challenges in achieving stable and clean mixed mode deposition processes, particularly in mixed mode reactors, where PVD and CVD processes are combined, leading to target contamination and process instability due to the formation of compound layers on the target.
Innovation Solution
The use of a rotatable cylindrical magnetron target with a tubular shutter that can be axially extended or retracted, combined with a magnet array that creates racetracks on the target surface, reducing target contamination by continuously exposing fresh material and allowing for controlled plasma formation between the target and shutter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a mixed mode deposition process is used to deposit complex coating stacks, then coating functionality and performance are improved, but target contamination occurs leading to process instability
Solution Approach 1:
The deposition chamber is segmented into two distinct zones: a sputtering zone containing the target and a CVD zone containing substrates. This spatial segmentation prevents direct interaction between target and CVD atmosphere, eliminating target contamination while enabling mixed mode deposition of complex coating stacks with multiple functionalities.
Solution Approach 2:
The harmful CVD atmosphere (hydrocarbon precursors) is extracted from the sputtering zone by confining CVD processes to a separate zone. Only inert sputtering gases are present in the sputtering zone, protecting the target from contamination while still enabling deposition of functional coatings through controlled material transport.
2Reliability
If a planar target is used in mixed mode deposition, then the target surface gets covered with compound layers, but using a rotatable cylindrical target continuously exposes fresh material
Solution Approach 1:
The target is designed as a rotatable cylindrical structure rather than a static planar target. Rotation dynamically exposes fresh target material to the sputtering process, preventing compound layer accumulation and maintaining target cleanliness. The rotational motion transforms a static contamination problem into a dynamically solved issue.
Solution Approach 2:
The target geometry transitions from a flat planar surface to a cylindrical curved surface. This curvature enables rotational motion and continuous exposure of fresh material areas. The cylindrical shape with radius 5-15 cm provides optimal surface area for sputtering while facilitating rotation to prevent contamination.
3Reliability
If the shutter is constantly extended to protect the target, then target contamination is reduced, but coating deposition is blocked
Solution Approach 1:
The shutter operates periodically, extending during sputtering operations to protect the target and retracting during CVD operations to allow coating deposition. This periodic action synchronized with process requirements enables both target protection and productive coating deposition without mutual interference.
Solution Approach 2:
The shutter acts as an intermediary component between the sputtering zone and CVD zone. It selectively blocks or permits material transport based on process requirements, enabling clean separation of functions while maintaining system integration. The shutter mediates between conflicting requirements of target protection and coating deposition.
4Productivity
If plasma is allowed to contact the target directly, then sputtering efficiency is high, but target erosion and contamination increase
Solution Approach 1:
The plasma generation and target interaction are segmented from the bulk target environment. Plasma is generated in a controlled sputtering zone with inert gases, maintaining high sputtering efficiency, while the target is protected from contaminating atmospheres. The spatial segmentation allows efficient sputtering without target erosion from reactive gases.
Solution Approach 2:
The sputtering zone maintains an inert atmosphere (argon or other noble gases) isolated from CVD precursors. This inert environment enables high sputtering efficiency through plasma-target interaction while preventing target contamination and erosion from reactive hydrocarbon gases used in CVD processes.
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 configuration stabilizes the deposition process, reduces target contamination, and enables efficient coating of substrates with uniform layers, including metal carbides, nitrides, and diamond-like coatings, while maintaining a clean environment by controlling the plasma and gas flow.
Implementation Method 1
The plasma can be confined in the vicinity of the target surface by means of magnetic fields originating from magnets placed at the side of the target opposite to the plasma side
Implementation Method 2
The ions gain kinetic energy as they are accelerated towards the negatively biased target and eject the target atoms towards the substrate. Such a process is called 'sputter deposition'.
Implementation Method 3
The ions gain kinetic energy as they are accelerated towards the negatively biased target and eject the target atoms towards the substrate
Implementation Method 4
Physical vapour deposition relates to processes wherein the coating is built-up by a ballistic shower of the substrate with coating atoms
Implementation Method 5
With 'unbalanced' is meant that part of the magnetic field lines do not close on the target surface but fan out to the substrate. Electrons gyrating around these field lines then can reach the substrate and create a local plasma.
Implementation Method 6
A self-bias will then develop that attracts ions to the substrate. Such a current of impinging ions leads to a further densification of the deposited layer, a process that is known as 'ion plating'.
Implementation Method 7
Chemical vapour deposition is in essence a process in which a gaseous precursor—usually a hydrocarbon—is excited so that radicals form that subsequently chemically react at the surface of the blank or already coated substrate.
Implementation Method 8
Through excitement in a plasma (plasma activated CVD, PA CVD). To this end a noble gas atoms, usually argon, is mixed with the precursor gas in order to generate a plasma, that subsequently generates radicals in the precursor gas. The plasma can be excited by means of a radiofrequent electromagnetic field (typically 13.56 MHz).
Implementation Method 9
By thermal activation of the precursor. Heating of the gas can be achieved by heating the substrate or the walls of the reactor, or by using heater wires (hot wire CVD). Using heater wires has the additional advantage that thermally emitted electrons add to the activation degree of the precursor gas.
Data Source
AI summary
A coating apparatus is revealed that is designed to coat substrates by means of a physical vacuum deposition process or a chemical vacuum deposition process or a combination thereof. Said coating apparatus is particular in that it uses a rotatable magnetron (14) that is coverable with an axially moveable shutter (18). Such an arrangement enables to keep the magnetron target clean or to clean the target in between or even during subsequent coating steps. The shutter further provides for a controllable gas atmosphere in the vicinity of the target. The arrangement wherein the magnetron is centrally placed is described. Substrates are then exposed to the sputtering source from all angles by hanging them on a planetary carousel (24) that turns around the magnetron.