Magnetron Assembly with Segmented Magnetic Arrays for Target Erosion Control
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Solution Overview
Problem
Standard magnetron assemblies face challenges in providing adequate magnetic flux for thicker target materials, leading to inadequate magnetic flux at the target surface and increased erosion rates at the target ends, which shortens the target life.
Innovation Solution
A magnetron assembly with four independent linear arrays of magnets, where two inner rows and two outer rows of magnets are arranged to maintain magnetic flux strength close to the target surface, reducing excessive erosion at the ends while optimizing electron retention and plasma efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the target thickness is increased to improve economy and production campaign length, then the usable material increases and fabrication cost per unit decreases, but the magnetic flux at the target surface becomes inadequate
Solution Approach 1:
The magnetron assembly is segmented into four independent linear arrays of magnets (two inner rows and two outer rows) instead of using a single continuous magnet structure. This segmentation allows each row to be independently optimized for magnetic flux generation, enabling adequate magnetic flux penetration through thicker target materials while maintaining proper field distribution across the target surface.
2Reliability
If the magnetic flux is increased to maintain adequate flux for thicker targets, then the electron retention improves, but the turn-around width broadens causing increased erosion at target ends
Solution Approach 1:
Different regions of the magnetron assembly are given different magnetic field characteristics. The four linear arrays are positioned and configured to create localized magnetic flux density variations, with stronger fields where electron retention is critical and more distributed fields in turn-around regions to minimize erosion. This local optimization allows high magnetic flux for electron retention without excessive broadening of turn-around areas.
3Productivity
If the magnetic flux strength is increased to maintain adequate flux for thicker targets, then the sputtering efficiency improves, but the target life decreases due to increased erosion rate
Solution Approach 1:
The magnetron assembly employs four independently configurable linear arrays of magnets that can be dynamically adjusted in terms of magnet strength, spacing, and arrangement. This dynamic configuration allows optimization of magnetic flux for high sputtering efficiency during operation while managing the field distribution to minimize erosion hotspots, thereby extending target life without sacrificing productivity.
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 enhances magnetic flux strength, reduces target erosion, and extends the life of thicker targets by maintaining electron retention and plasma efficiency, improving the deposition process for materials like transparent conductive oxides.
Implementation Method 1
A magnetron assembly is disposed within the tube and supplies magnetic flux which permeates the target such that there is adequate magnetic flux at the outer surface of the target. The magnetic field is designed in a way such that it retains electrons emitted from the target so as to increase the probability that they will have ionizing collisions with the working gas
Implementation Method 2
This field retains the electrons and causes them to drift in a direction perpendicular to the magnetic field lines, which is parallel to the rows 102 of magnets. This is known as the ExB drift
Implementation Method 3
Magnetron sputtering of rotating targets is well known in the art and is used extensively for producing a wide variety of thin films on a wide variety of substrates
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
In one embodiment, a magnetron assembly comprises a plurality of magnets and a yoke configured to hold the plurality of magnets in at least four independent linear arrays. The plurality of magnets is arranged in the yoke so as to form a pattern comprising an outer portion and an inner portion. The outer portion substantially surrounds the perimeter of the inner portion. The magnets used to form the outer portion have a first polarity and the magnets used to form the inner portion having a second polarity. The outer portion of the pattern comprises a pair of elongated sections that are substantially parallel to one another. The outer portion of the pattern comprises a pair of turnaround sections, wherein each turnaround section substantially spans respective ends of the pair of elongated sections and wherein each turnaround section comprises a plurality of magnets having the first polarity. In another embodiment, a magnetron assembly comprises a yoke and a plurality of magnets reconfigurably positioned on the yoke so as to form a racetrack pattern having at least one stepped turnaround section.