Spin Coating Apparatus Multi-Stage Dispensing for Film Uniformity
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Solution Overview
Problem
Conventional spin coating methods require a large amount of coating liquid and struggle to uniformly coat substrates with large areas or complex geometries, leading to inefficiencies and incomplete coverage due to air resistance and turbulence during high-speed rotation.
Innovation Solution
A spin coating method and apparatus that dispense a first amount of coating liquid at a high number of revolutions, followed by a second amount at a lower number of revolutions, allowing the liquid to spread more evenly and reduce air resistance, with subsequent rotation at a specific number of revolutions to achieve the desired film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is rotated at a high number of revolutions to reduce coating time and achieve uniform thickness, then the film thickness uniformity is improved, but the coating liquid cannot spread uniformly due to air resistance, resulting in incomplete coverage
Solution Approach 1:
The spin coating process is divided into multiple stages with different rotation speeds: a first stage at high speed for initial spreading, a second stage at intermediate speed for uniform distribution, and a third stage at high speed for final thickness control. This segmentation allows each stage to optimize for its specific function, resolving the contradiction between speed and coverage.
Solution Approach 2:
The rotation speed is dynamically adjusted during the coating process rather than maintaining a constant speed. The system transitions between different rotational states (high → intermediate → high) to adapt to the changing coating liquid distribution, enabling both complete coverage and uniform thickness.
2Quantity of substance
If a large amount of coating liquid is supplied to ensure complete coverage of large area substrates, then the coverage is improved, but the amount of coating liquid required increases significantly
Solution Approach 1:
The coating liquid supply is segmented into multiple dispensing stages corresponding to different rotation speeds. The system dispenses liquid during the first high-speed stage, continues dispensing during the intermediate speed stage, and may add final adjustments during the third stage. This segmented approach ensures liquid is supplied when most effective, reducing total consumption while maintaining coverage.
Solution Approach 2:
The coating liquid is preliminarily dispersed during the first high-speed rotation stage before the substrate reaches its final coating configuration. This preliminary action allows the liquid to spread across the substrate surface early in the process, reducing the total amount needed compared to supplying all liquid at once or later stages.
3Manufacturing precision
If the substrate is rotated at high speed from the beginning to achieve uniform film thickness, then the film thickness is controlled well, but the coating liquid spatters and does not spread uniformly across the substrate
Solution Approach 1:
The rotation process is segmented into distinct phases: an initial high-speed phase for rapid liquid dispersion, an intermediate phase for stable uniform distribution, and a final high-speed phase for thickness precision. This segmentation prevents the instability that would occur if high speed were maintained throughout the entire coating process.
Solution Approach 2:
The spin coating process employs periodic changes in rotation speed rather than a continuous constant speed. The system cycles through different rotational regimes (high → intermediate → high) to periodically redistribute the coating liquid, ensuring uniform composition while maintaining control over final film thickness.
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 reduces the overall amount of coating liquid needed while ensuring uniform coverage across the substrate, even on larger or stepped surfaces, by optimizing the dispensing and rotation speeds to manage air resistance and spreading effectively.
Implementation Method 1
dispensing a first amount of coating liquid to a central part of the substrate while rotating the substrate about the central part of the substrate at a first number of revolutions
Implementation Method 2
the first number of revolutions is a number of revolutions at which the first amount of coating liquid does not uniformly spread over the substrate because of air resistance
Data Source
AI summary
A spin coating apparatus that supplies a coating liquid to a substrate and rotating the substrate to form a coating film, has a holding part that holds the substrate mounted thereon in a horizontal position; a rotationally driving source that rotationally drives the holding part about a rotational axis parallel with the vertical direction, thereby rotating the substrate; and a coating liquid supplying part that supplies the coating liquid to the substrate held by the holding part.