Slit Nozzle Coating Apparatus for Uniform Wafer Film
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Solution Overview
Problem
The spin coating method results in significant waste of coating liquid due to scattering at the peripheral edges of the substrate, leading to non-uniform film thickness and inefficiencies in coating processes.
Innovation Solution
A coating processing apparatus with a slit-shaped ejecting port and a moving mechanism that controls the relative movement of the substrate and coating nozzle, preventing liquid diffusion at the edges by using capillary phenomena to ensure uniform coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the spin coating method is used to coat coating liquid on the substrate by high-speed rotation, then the coating liquid is quickly diffused on the substrate, but most of the coating liquid is scattered from the peripheral portion and wasted
Solution Approach 1:
The coating process is segmented into multiple stages: initial coating liquid supply, intermediate cessation period, and final coating completion. The coating nozzle is moved in steps rather than continuously, allowing the coating liquid to be applied in controlled segments that prevent peripheral scattering while ensuring complete coverage.
Solution Approach 2:
The coating liquid is supplied to the substrate in advance during the initial stage before the substrate completes its rotation. The coating nozzle is positioned to supply liquid early in the rotation cycle, allowing the liquid to be deposited on the substrate surface before centrifugal forces can cause peripheral scattering.
2Productivity
If the coating liquid is supplied continuously during substrate rotation, then the substrate is quickly coated, but the coating liquid diffuses to the peripheral edges causing non-uniform film thickness
Solution Approach 1:
The coating liquid supply is performed periodically rather than continuously. The coating nozzle supplies liquid at specific intervals during substrate rotation, ceases supply for a predetermined period, and then resumes. This periodic action allows the coating liquid to be deposited uniformly without excessive diffusion to the edges, achieving both efficiency and uniformity.
Solution Approach 2:
The coating process uses dynamic control of the coating nozzle position and movement speed based on the substrate's rotation state. The nozzle moves in coordinated steps with the rotating substrate, adjusting its position to maintain optimal coating conditions throughout the rotation cycle, thereby achieving uniform film thickness while maintaining productivity.
3Loss of substance
If the coating nozzle is positioned close to the substrate to use capillary phenomenon, then coating liquid waste is reduced, but the ejecting port may contact the substrate causing contamination
Solution Approach 1:
The coating nozzle is preliminarily positioned at a safe distance from the substrate surface before coating begins. The nozzle is moved close to the substrate only when needed for coating, and retracted when not in use. This preliminary positioning strategy allows the system to maintain the benefits of capillary phenomenon while preventing contact contamination through proper timing of the positioning action.
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 apparatus achieves uniform coating within the substrate plane by suppressing local thickening at the peripheral edges, reducing waste and improving coating efficiency.
Implementation Method 1
the coating liquid is drawn out from the ejecting port by the capillary phenomenon and coated on the substrate
Data Source
AI summary
At the time of initiating coating, when a first end of an ejecting port of a coating nozzle is located at one end of a peripheral edge of a wafer, the wafer and the coating nozzle are relatively moved by a moving mechanism while exposing a coating liquid from the ejecting port. During the coating, the wafer and the coating nozzle are relatively moved by the moving mechanism while the coating liquid ejected from the ejecting port is in contact with the wafer, to coat the coating liquid on the wafer. At the time of finishing the coating, when a second end of the ejecting port is located at the other end of the peripheral edge of the wafer, the wafer and the coating nozzle are relatively moved by the moving mechanism while exposing the coating liquid from the ejecting port.