Spiral Liquid Coating Nozzle Dynamics for Uniform Film Thickness
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Solution Overview
Problem
Existing liquid coating methods struggle to achieve uniform film thickness on substrates with varying in-plane thickness or warpage, as they rely on incomplete measurements of substrate thickness, leading to non-uniform coating films.
Innovation Solution
A liquid coating method that involves ejecting a coating liquid from a nozzle positioned above a rotating substrate, with the nozzle moving in a spiral pattern along the substrate's surface, maintaining a constant linear velocity by adjusting the substrate's rotation speed and nozzle height to ensure a consistent ejection flow rate, thereby achieving uniform film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the substrate is rotated at constant speed during spiral coating, then the coating process is simple to control, but the linear velocity at the ejection position varies causing non-uniform film thickness
Solution Approach 1:
The substrate rotation speed is dynamically adjusted based on the ejection position radius. As the nozzle moves from the center toward the periphery, the rotation speed is increased to compensate for the increasing linear velocity, maintaining constant coating deposition rate and uniform film thickness across the substrate surface.
Solution Approach 2:
The rotation speed parameter is changed as a function of the ejection position. By establishing a relationship between rotation speed and radial position, the system maintains constant linear velocity at the ejection point, ensuring uniform coating thickness while preserving the simplicity of spiral coating methodology.
2Device complexity
If the gap between the ejection port and substrate surface is kept constant, then the equipment structure is simple, but the ejection flow rate varies causing non-uniform film thickness on substrates with varying thickness
Solution Approach 1:
The gap between the ejection port and substrate surface is dynamically adjusted during the coating process. As the substrate thickness varies, the system modifies the gap distance to maintain a constant ejection flow rate, ensuring uniform film deposition without requiring complex real-time thickness measurement and feedback systems.
Solution Approach 2:
The gap adjustment is performed in advance based on predetermined substrate thickness characteristics. By pre-establishing the relationship between substrate position and optimal gap distance, the system ensures consistent ejection flow rate before coating begins, simplifying the overall control mechanism while achieving uniform film thickness.
3Productivity
If the coating liquid is ejected at high speed to shorten processing time, then the productivity increases, but the film thickness uniformity deteriorates due to varying linear velocity at different positions
Solution Approach 1:
The system maintains high coating speed by dynamically adjusting the substrate rotation speed to match the ejection position. This allows rapid coating while preserving film uniformity, as the rotation speed is continuously optimized to maintain constant linear velocity at the ejection point throughout the spiral coating path.
Solution Approach 2:
The coating process maintains continuous high-speed operation without interruptions or speed reductions. By implementing real-time rotation speed adjustment, the system sustains optimal coating conditions throughout the entire spiral path, achieving both high productivity and uniform film thickness without compromising either objective.
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
The method ensures a uniform film thickness across the substrate by maintaining a consistent ejection flow rate and avoiding overlap of the coating liquid, even on substrates with warpage or varying thickness, thus enhancing the precision and efficiency of the coating process.
Implementation Method 1
coating a coating liquid on a surface of a substrate by ejecting the coating liquid to the surface of the substrate from an ejection nozzle
Implementation Method 2
rotating the substrate around a rotary axis extending along a direction orthogonal to the surface of the substrate
Data Source
AI summary
Disclosed is a liquid coating method. The method executes processes of: coating a coating liquid in a spiral form on a surface of a substrate by ejecting the coating liquid from the ejection nozzle while moving the ejection nozzle in a predetermined direction between the rotary axis and a peripheral edge of the substrate during rotation of the substrate; making a linear velocity at an ejection position of the coating liquid from the ejection nozzle substantially constant by reducing a number of rotations of the substrate as the ejection position is positioned closer to the peripheral edge of the substrate; and making an ejection flow rate of the coating liquid ejected from the ejection nozzle substantially constant by changing a gap between the ejection port of the ejection nozzle and the surface of the substrate based on a flow rate of the coating liquid before ejection from the ejection nozzle.