Spin Coater Flow Controller for Uniform Photoresist Coating
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Solution Overview
Problem
In spin coating processes for photolithography, the viscous photoresist materials tend to splash and contaminate the substrate due to speed differences between the central and edge portions, leading to uneven layer thickness and particle contamination.
Innovation Solution
A spin coater with a flow controller is introduced between the bowl and the substrate's edge, separating the chemical and air flows into linear and non-linear streams, preventing flow loss and sedimentation at the edge and minimizing vertex formation, which reduces particle contamination and edge bead defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is rotated at high speed to control photoresist layer thickness, then the coating thickness can be controlled, but the photoresist materials splash and contaminate the substrate due to speed differences between central and edge portions
Solution Approach 1:
The patent introduces a flow controller that segments the air flow into multiple controlled streams. The flow controller divides the single air inlet into multiple outlets positioned at different locations, creating segmented air flows that independently control different regions of the substrate surface, preventing turbulent mixing and splash contamination while maintaining uniform coating thickness.
Solution Approach 2:
The flow controller acts as an intermediary device between the air source and the substrate. It mediates the air flow by regulating its velocity and distribution pattern, converting the harmful high-speed turbulent flow into controlled laminar flows that prevent photoresist splash while maintaining the necessary coating uniformity.
2Quantity of substance
If the air flow speed decreases from central to edge portion, then the photoresist layer becomes thicker at the edge, but this creates edge bead defects and contamination
Solution Approach 1:
The flow controller implements local quality control by providing different air flow velocities to different regions of the substrate. The multiple outlets are positioned and sized to deliver higher air flow velocity at the edge portions and appropriate velocity at the central portion, creating locally optimized flow conditions that prevent edge bead defects while maintaining overall coating uniformity.
Solution Approach 2:
The system dynamically adjusts air flow distribution across the substrate surface. The flow controller is designed to compensate for the natural velocity gradient, actively maintaining consistent photoresist layer thickness by adjusting local air flow rates to match the rotational speed variations of the substrate.
3Object-generated harmful factors
If a flow controller is added to separate linear and non-linear flows, then particle contamination is reduced, but the device complexity increases
Solution Approach 1:
The patent extracts the flow control function from the main spin coater system into a separate, detachable flow controller component. This modular approach isolates the complexity into a dedicated unit that can be easily attached and removed, simplifying the overall system maintenance and reducing the operational complexity despite adding a new component.
Solution Approach 2:
The flow controller manages complexity by focusing on parameter control rather than structural complexity. It uses adjustable parameters such as outlet positioning, outlet size, and flow rate distribution to achieve the desired flow separation, allowing for simple structural design with controllable performance through parameter optimization.
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 flow controller ensures a uniform coating layer thickness and minimizes particle contamination by maintaining higher flow speeds at the edge and reducing vertex formation, enhancing the quality and uniformity of the spin-coated layers.
Implementation Method 1
a flow controller detachably coupled to the bowl... to separate the flow into a linear flow and a non-linear flow
Implementation Method 2
the photosensitive materials are supplied onto a rotating substrate... the particles of the photosensitive materials, which are supplied to a central portion of the substrate, generally spread out on a surface of the substrate and flow from the central portion to the edge portion
Data Source
AI summary
A spin coater includes a rotatable chuck structure configured to hold a substrate, a bowl enclosing the substrate and guiding a flow of a fluid around the substrate to a bottom of the bowl, and a flow controller detachably coupled to the bowl such that the flow controller is arranged between the bowl and an edge of the substrate and separates the flow into a linear flow and a non-linear flow.