Spin Coater Annular Member Protrusion Gas Flow Rectification
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Solution Overview
Problem
The existing spin coating methods face challenges in achieving uniform film thickness and high throughput due to turbulent gas flows on larger substrates, leading to concave-convex portions and increased drying times, especially with larger semiconductor wafers like 450 mm in diameter.
Innovation Solution
A coating film forming apparatus and method that includes an annular member with a protrusion along its inner periphery to rectify the gas stream above the substrate, preventing turbulent flow and reducing the component of the gas stream directed downward near the inner peripheral edge, thereby enhancing film thickness uniformity and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotational speed of the substrate is increased to rapidly dry the resist, then the drying speed is improved, but the Reynolds number increases causing turbulent flow and concave-convex portions on the resist film
Solution Approach 1:
A ring-shaped plate is introduced as an intermediary component between the substrate and the gas stream. This plate modifies the gas flow pattern, creating a controlled gas stream that prevents turbulent flow while maintaining effective drying. The plate acts as a mediator that decouples the conflict between drying speed and film uniformity.
Solution Approach 2:
The ring-shaped plate creates different gas flow conditions at different locations on the substrate. By controlling the gas stream direction and distribution, the plate ensures uniform drying across the entire substrate surface, preventing local variations in film thickness while maintaining overall drying efficiency.
2Productivity
If the size of the wafer is increased to 450 mm diameter, then the throughput is improved, but the upper limit of rotational speed is lowered due to increased Reynolds number
Solution Approach 1:
The ring-shaped plate serves as a mediator that enables higher rotational speeds on larger wafers by controlling the gas stream. It prevents turbulent flow patterns that would otherwise limit the rotational speed, allowing 450 mm wafers to be processed at optimal speeds without sacrificing film quality.
Solution Approach 2:
The plate modifies the gas flow parameters (Reynolds number, flow direction, velocity distribution) to maintain laminar flow conditions even at higher rotational speeds. This parameter control allows larger wafers to be processed at speeds that would normally produce turbulent flow and film defects.
3Manufacturing precision
If a ring-shaped plate is provided to rectify the gas stream, then the turbulent flow is reduced, but the gas stream is rapidly directed downward near the inner peripheral edge causing local thickness increase
Solution Approach 1:
Protrusions are added at specific locations (inner peripheral edge) of the ring-shaped plate to create localized modifications in gas flow. These protrusions generate upward gas flow components that counteract the downward flow direction near the periphery, ensuring uniform drying conditions across the entire substrate surface.
Solution Approach 2:
The ring-shaped plate is modified with asymmetric protrusions at the inner peripheral edge, creating non-uniform gas flow distribution. This asymmetric design specifically addresses the downward flow problem at the periphery while maintaining the overall rectification function, achieving balanced drying across the substrate.
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 solution effectively prevents local thickness variations and enhances the uniformity of the coating film across the substrate, improving the drying process efficiency and reducing the time required for film drying, even at higher rotational speeds.
Implementation Method 1
The substrate is then rotated such that a centrifugal force causes the resist to expand to a periphery of the substrate
Implementation Method 2
the Reynolds number increases. If the Reynolds number exceeds a certain value, a flow of the gas stream on the substrate becomes turbulent
Implementation Method 3
the substrate continues to be rotated to dry the resist on the surface of the substrate, thereby forming the resist film
Data Source
AI summary
A coating film forming apparatus includes: a substrate holding unit to horizontally hold a substrate; a rotating mechanism to rotate the substrate held by the substrate holding unit; a coating liquid supplying mechanism to supply coating liquid to form a coating film on the substrate; an annular member to rectify a gas stream above a periphery of the substrate when liquid film of the coating liquid is dried by rotation of the substrate, the annular member being provided above the periphery of the substrate and along a circumferential direction of the substrate so as to cover the periphery of the substrate; and a protrusion provided on an inner periphery of the annular member along circumferential direction of the annular member so as to protrude upward to reduce component of the gas stream flowing directly downward near an inner peripheral edge of the annular member.