Two-Axis Spin Coating for Bubble-Free Uniform Thin Films
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Solution Overview
Problem
Conventional spin coating methods face issues with uneven surface leveling, inner layer air bubbling, and edge beading, which affect the quality and uniformity of coated films, particularly in semiconductor manufacturing.
Innovation Solution
A two-axis spin coating method and apparatus that utilizes horizontal and vertical rotations, with a 90° angle between the axes, generating elevated centrifugal acceleration to simulate artificial gravity, thereby controlling surface tension and viscosity, expediting bubble release, and redistributing edge thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional spin coating is used, then coating deposition is achieved, but surface leveling is uneven and air bubbles form in the inner layer
Solution Approach 1:
The patent introduces a vertical rotation axis perpendicular to the horizontal spin axis, creating a two-axis rotation system. This adds a vertical dimension to the coating process, generating artificial gravity that acts downward through the coating layer, thereby leveling the surface and expelling air bubbles from the inner layer simultaneously.
Solution Approach 2:
The patent changes the gravitational parameter by introducing artificial gravity through vertical rotation. By controlling the rotation speed, the artificial gravity acceleration can be adjusted to optimize surface leveling and bubble removal, transforming the insufficient gravity condition into a controlled gravitational field that improves film quality.
2Productivity
If fast spinning speed is used, then coating material spreads quickly, but edge beading occurs and surface leveling is poor
Solution Approach 1:
The vertical rotation component creates artificial gravity that acts independently of the horizontal spin speed. This vertical gravitational force continues to level the coating surface and prevent edge beading even at high spinning speeds, decoupling the relationship between spin speed and edge quality.
Solution Approach 2:
The artificial gravity generated by vertical rotation acts as a counterforce to the centrifugal force that causes edge beading. By introducing this opposing gravitational pull, the patent balances the forces acting on the coating material, preventing accumulation at the edges while maintaining fast deposition.
3Manufacturing precision
If vacuum chambers and solvent treatments are used, then air bubbles are removed and film quality is improved, but process complexity and cost increase
Solution Approach 1:
The patent enables the coating process itself to perform bubble removal and surface leveling through the two-axis rotation mechanism. The artificial gravity generated during coating automatically expels air bubbles and levels the surface, eliminating the need for separate vacuum chambers or solvent treatment steps.
Solution Approach 2:
The patent extracts the bubble removal and surface leveling functions from separate post-processing steps and integrates them into the coating deposition process itself. By taking out these functions from vacuum chambers and solvent treatments and embedding them in the spin coating mechanism, the process becomes simpler and more efficient.
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 achieves surface-level films without bubbles and uniform thickness, reducing defects and enhancing film density and resolution.
Implementation Method 1
The coating material is deposited at the center of a substrate which can be rotated by the spinning machine fast enough to spread the solution radially all over the substrate
Implementation Method 2
The outward exerted centrifuge acceleration perpendicular to the element of coating on the surface of the substrate can be considered as an elevated artificial gravity acceleration constantly in the downward direction
Implementation Method 3
This elevated heaviness overcomes coating viscosity and obliges the convex regions to flow toward the concave areas to form surface-level films
Implementation Method 4
This elevation increases the reduction of surface amplitude irregularities and forms level films... The velocity of Micro-Sized Air-Bubbles' motion toward the coating surface can be increased by increasing the values of elevated artificial gravity acceleration
Data Source
AI summary
A modified technology of spin coating which is named Two-Axis spin coating is disclosed. The innovative Two-Axis spin coating apparatus is a rotary device that spins the substrate horizontally the same as conventional spin coaters while the whole horizontal spinning system can be rotated vertically. The vertical rotation of the substrate generates a vertical centrifugal force perpendicular to the surface of the substrate which allows the coating face with an elevated artificial gravity acceleration. The elevation of gravity acceleration adjusts and normalizes the local high and low surface tension stresses on the surface of the coated film. This elevation of gravity also increases the weight of coating elements artificially and obliges the wavy surface convex regions to flow toward the concave areas. The elevation of gravity also obliges the lighter probable air bubbles inside the layer, immediately before the coating surface skinning process, move toward the surface and drain out from the layer. The invention provides a method to level the layer's edge beads, level the coated surface, drain out probable micro sized air bubbles inside the layer and form denser film simultaneously.