Variable Substrate Velocity for Coating Uniformity
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Solution Overview
Problem
Existing methods for achieving extremely good layer thickness uniformity on large substrates, such as silicon wafers, face challenges in maintaining uniformity due to variations in deposition rate and substrate movement, leading to deviations greater than 0.5% and often exceeding 1% in industrial applications like semiconductor and photovoltaic production.
Innovation Solution
A method is developed to determine a velocity profile for the substrate movement relative to the coating source, using approximation functions to describe deposition rate and velocity, allowing for precise control of layer thickness uniformity by adjusting the substrate's velocity based on measured layer thickness profiles, thereby compensating for deviations and achieving uniformity better than 0.1%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If linear dynamic deposition method is used with constant substrate velocity, then coating operation can be performed on large substrates, but layer thickness uniformity deteriorates with deviations greater than 0.5%
Solution Approach 1:
The substrate velocity is changed from constant to variable during the coating process. The velocity profile is dynamically adjusted based on the position of the substrate relative to the coating source, allowing the system to maintain layer thickness uniformity across large substrate areas by compensating for position-dependent deposition rate variations.
Solution Approach 2:
The deposition parameters are changed by implementing a variable velocity profile instead of constant velocity. The velocity parameter is continuously adjusted during the coating process to compensate for changes in deposition rate, thereby maintaining manufacturing precision across the entire substrate area.
2Ease of manufacture
If elongated magnetron cathodes with typical target widths of 80-150 mm are used, then cathode structure requirements are met, but coating range is limited and cannot adequately cover large substrates
Solution Approach 1:
Instead of using a single large cathode or multiple cathodes, the system uses a single elongated cathode with variable substrate velocity. The dynamics of substrate movement compensate for the limited static coating range, allowing adequate coverage of large substrates while maintaining standard cathode dimensions.
Solution Approach 2:
The solution moves from expanding the cathode dimensions (width) to expanding the effective coating range through the time dimension. By varying substrate velocity during movement, the system extends the coating range beyond the static target width without modifying cathode structure.
3Area of stationary object
If wafer diameter is increased to 450 mm for larger substrate production, then production capacity is improved, but layer thickness uniformity deteriorates due to larger area coverage requirements
Solution Approach 1:
The variable velocity profile dynamically adapts to different substrate sizes. For larger 450 mm wafers, the velocity is adjusted more significantly to compensate for the increased distance from the coating source, maintaining layer thickness uniformity across the larger area that would otherwise be impossible with constant velocity.
4Quantity of substance
If tunnel barrier thickness is reduced to 1 nm or less for TMR layer systems, then device performance is improved, but manufacturing precision requirements become extremely stringent with deviations less than 0.1%
Solution Approach 1:
The velocity parameter is precisely controlled and varied to achieve the required manufacturing precision. For ultra-thin layers of 1 nm or less, even small variations in velocity would cause unacceptable deviations, so the system implements precise velocity control with tight tolerances to maintain uniformity within 0.1%.
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 achievement of target layer thickness profiles with deviations less than 0.1% across large substrates by optimizing the substrate's velocity profile, significantly improving layer thickness uniformity in industrial coating processes.
Implementation Method 1
The disclosure relates to a device and method of coating a substrate, in particular of coating a substrate with thin layers of magnetic or non-magnetic materials... using cathode sputtering
Implementation Method 2
These are cathodes with a rectangular target in which permanent magnets are used to generate a specific magnetic field in order to increase the sputtering effect
Implementation Method 3
The substrates are moved through the coating range of the cathode in a straight line and perpendicular to the longitudinal orientation and at a defined distance of the cathode. This method is called 'linear dynamic deposition' (LDD)
Data Source
AI summary
The disclosure relates to a method of determining a velocity profile for the movement of a substrate to be coated relative to a coating source.