Magnetron Sputtering Target Homogeneity via Azimuthal Field Control
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Solution Overview
Problem
Existing sputter coating techniques for two-dimensionally extended substrates face challenges in achieving uniform layer thickness and minimizing net redeposition, particularly when using magnetron sputter sources, which can lead to variations in layer thickness and material redeposition on the target surface.
Innovation Solution
The method involves continuously rotating substrates around a common axis, with a magnetron sputter source having a circular target and a magnetron magnet arrangement that generates a controlled area of magnetron plasma, adjusting the azimuthal extent and magnetic field strength to minimize variations in layer thickness and net redeposition by creating specific azimuthal and magnetic field distributions, and rotating the target to ensure even sputtering across its surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a magnetron sputter source is used for coating substrates, then the sputtering efficiency is improved, but variations in layer thickness and net redeposition on the target surface occur
Solution Approach 1:
The magnetron magnet arrangement is designed to create a non-uniform magnetic field distribution across the target surface, with different azimuthal extents at different radial positions. This local variation in magnetic field strength optimizes plasma confinement and sputtering rate at each location, compensating for natural thickness variations and reducing net redeposition while maintaining high overall sputtering efficiency.
Solution Approach 2:
The system employs continuous rotation of substrates around a common axis, creating a dynamic coating process where each substrate position experiences varying exposure to the magnetron plasma over time. This dynamic approach allows for more uniform layer deposition across the substrate surface while maintaining the high productivity benefits of magnetron sputtering.
2Productivity
If the magnetron plasma area is increased to cover more of the target surface, then the sputtering rate is improved, but net redeposition on the target surface increases
Solution Approach 1:
The magnetron magnet arrangement creates a controlled plasma distribution where the azimuthal extent varies radially across the target. This ensures adequate plasma coverage for high sputtering rates while preventing excessive plasma concentration in any single area, thereby reducing net redeposition of target material.
3Productivity
If the magnetic field strength is increased to confine plasma better, then the sputtering efficiency is improved, but the azimuthal extent of plasma is reduced causing thickness variations
Solution Approach 1:
The magnetron magnet arrangement is specifically designed with varying magnetic field strengths at different radial positions on the target. This creates an optimized plasma confinement pattern where stronger fields provide good confinement where needed while maintaining appropriate azimuthal extents elsewhere, achieving both high sputtering efficiency and uniform layer thickness.
Solution Approach 2:
The system varies the magnetic field parameters (strength and azimuthal extent) as a function of radial position on the target surface. This parameter optimization allows the plasma to be sufficiently confined for efficient sputtering while maintaining the azimuthal extent necessary for uniform coating deposition.
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 results in improved homogeneity of sputter deposition on substrates and minimizes net redeposition on the target surface, optimizing the use of target material and reducing thickness variations, even in reactive gas atmospheres.
Implementation Method 1
The magnetron magnet-arrangement generates a magnetic field with magnetic field lines arcing over the sputter surface in at least one tunnel like pattern
Implementation Method 2
Due to the interaction of the angled electric field and magnetron magnetic field, electrons are trapped in and along the magnetron magnetic field
Implementation Method 3
It is along the area of magnetron plasma that the sputter surface is most eroded or sputtered off, leading to the so called 'racetracks' in the sputter surface. Accordingly, it is along the area of magnetron plasma, defined by the magnetron magnet-arrangement, that the substrate is most sputter coated.
Data Source
AI summary
Whenever substrates are rotationally and continuously conveyed in a vacuum recipient around a common axis and past a magnetron sputter source, sputtering of the target, rotating around a central target axis, by the stationary magnetron plasma is adapted to the azimuthal extents radially differently spaced areas of the substrates become exposed to the target thereby improving homogeneity of deposited layer thickness on the substrates and ensuring that the complete sputter surface of the target is net-sputtered.