Ring-Shaped Member for Laminar Airflow in Spin Coating
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Solution Overview
Problem
The challenge in forming a coating film on a substrate, such as a semiconductor wafer, is the reduction in in-plane uniformity of film thickness due to turbulent air flows caused by high substrate rotation speeds, which lead to coating spots and irregularities, especially as wafer sizes increase.
Innovation Solution
A coating film forming apparatus and method that includes a ring-shaped member positioned to straighten air flows above the substrate's peripheral edge, with a control unit managing the ring's position and the substrate's rotation speed to prevent turbulence, ensuring uniform film thickness by diffusing the coating liquid with centrifugal force and adjusting the revolution number to maintain laminar airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the substrate rotation speed is increased to rapidly dry the coating liquid, then the drying speed is improved, but the air flow becomes turbulent causing coating spots and reducing film thickness uniformity
Solution Approach 1:
A baffle plate is introduced as an intermediary component between the substrate and the air flow path. The baffle plate has a specific structure with a plate body and a protruding portion that acts as a flow guide, mediating the air flow to prevent turbulence while allowing the high rotation speed necessary for rapid drying to continue.
Solution Approach 2:
The invention changes the physical parameters of the air flow path by introducing the baffle plate structure. The plate body and protruding portion create specific flow path characteristics that modify the Reynolds number and flow regime, enabling transition from turbulent to laminar flow conditions while maintaining high rotation speeds.
2Manufacturing precision
If a baffle plate is installed to prevent turbulent air flow, then film thickness uniformity is improved, but the drying speed is reduced
Solution Approach 1:
The baffle plate structure is designed to be dynamic in its interaction with the air flow. The protruding portion specifically guides the air flow to maintain laminar conditions only in the critical region where coating spots would form, while allowing adequate air flow overall to maintain drying speed. The structure adapts to the rotation speed and air flow conditions.
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 effectively suppresses the generation of coating spots and enhances the uniformity of film thickness across the substrate, allowing for higher substrate rotation speeds without reducing the drying speed of the coating film, thus improving the efficiency and quality of the coating process.
Implementation Method 1
a first revolution number at which the coating liquid supplied to the central portion of the substrate is diffused toward the peripheral edge portion by a centrifugal force
Implementation Method 2
positioning the ring-shaped member at a processing position where an air flow flowing above the peripheral edge portion of the substrate is straightened
Data Source
AI summary
A coating film forming apparatus includes a substrate holding unit, a ring-shaped member annularly installed along a circumferential direction of the substrate so as to cover an upper side of a peripheral edge portion of the substrate, and a control unit that outputs a control signal so as to perform: positioning the ring-shaped member at a processing position where an air flow flowing above the peripheral edge portion of the substrate is straightened; rotating the substrate at a first revolution number such that a coating liquid supplied to a central portion of the substrate is diffused toward the peripheral edge portion by a centrifugal force; bringing the ring-shaped member to a retreated position where an air flow flowing near a front surface of the substrate is prevented from becoming turbulent; and reducing the revolution number of the substrate to a second revolution number lower than the first revolution number.