Spin Coating Speed Control for Uniform Resist Film
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Solution Overview
Problem
The existing spin coating method for semiconductor wafers is inefficient in uniformly applying a small amount of liquid resist, leading to uneven resist film thickness and high consumption of expensive liquid resists.
Innovation Solution
A novel coating method involving multiple rotating speed steps and nozzle position adjustments to spread and reshape the liquid resist uniformly across the wafer, reducing consumption by applying it in smaller amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a small amount of liquid resist is supplied onto the substrate and allowed to spread outwardly from the center, then the consumption of liquid resist is reduced, but the liquid resist is unlikely to spread uniformly in the peripheral region and can spread like a beard, making it impossible to make the thickness of the resist film uniform
Solution Approach 1:
The patent applies dynamic control of rotating speed throughout the coating process. The substrate rotates at different speeds at different stages: initially at a first rotating speed during liquid resist supply, then at a second lower speed during spreading, followed by a third higher speed for uniform distribution, and finally at a fourth intermediate speed for stabilization. This dynamic speed adjustment enables the liquid resist to spread uniformly across the entire substrate surface including peripheral regions while maintaining consistent film thickness, thereby resolving the contradiction between reduced material consumption and manufacturing precision.
2Quantity of substance
If a liquid resist is supplied in a small amount onto a substrate, then the cost is reduced, but the liquid resist cannot spread uniformly and forms non-uniform patterns
Solution Approach 1:
The patent employs periodic action through multi-stage rotating speed changes. The substrate undergoes sequential rotation at four different speed levels, creating periodic variations in centrifugal force that systematically control the liquid resist spreading process. This periodic speed modulation ensures uniform distribution of the limited liquid resist amount across the entire substrate surface, preventing non-uniform patterns while maintaining reduced material consumption.
3Loss of substance
If the liquid resist spreads outwardly from the center like a beard, then the supply amount can be small, but it is not possible to subsequently make the thickness of the resist film uniform at every point
Solution Approach 1:
The patent utilizes parameter changes by systematically varying the rotating speed parameter through four distinct stages. The rotation speed is changed from the first speed during supply to the second lower speed for initial spreading, then to the third higher speed for uniform distribution, and finally to the fourth intermediate speed for stabilization. These parameter changes transform the liquid resist behavior from non-uniform beard-like spreading to uniform distribution, achieving both reduced consumption and uniform film thickness.
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 efficiently applies a smaller amount of liquid resist uniformly across the wafer, reducing consumption and ensuring consistent film thickness, even on three-dimensional patterns.
Implementation Method 1
The liquid resist spreads radially outward on the wafer by centrifugal force
Data Source
AI summary
There is provided a coating method which can efficiently apply a coating liquid, such as a liquid resist, to the entire surface of a wafer even when the coating liquid is supplied in a smaller amount than a conventional one, and can therefore reduce the consumption of the coating liquid. The coating method includes: a first step of rotating the substrate at a first rotating speed while supplying the coating liquid onto approximately the center of the rotating substrate; a second step of rotating the substrate at a second rotating speed which is lower than the first rotating speed; a third step of rotating the substrate at a third rotating speed which is higher than the second rotating speed; and a fourth step of rotating the substrate at a fourth rotating speed which is higher than the second rotating speed and lower than the third rotating speed.