Spin Coating Rotation Control for Resist Uniformity
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Solution Overview
Problem
Conventional spin coating methods for semiconductor wafers face challenges in achieving in-plane uniformity and reducing the supply amount of resist solution, leading to film thickness issues at the outer peripheral edge of the substrate.
Innovation Solution
A coating treatment method involving multiple rotation steps, including initial high-speed rotation, deceleration, acceleration, and slower rotation phases, with continuous solution supply, to ensure uniform coating and prevent drying of the resist solution at the substrate's edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the supply amount of resist solution is reduced, then the cost is reduced and coating efficiency is improved, but the in-plane uniformity deteriorates and film thickness at outer peripheral edge becomes insufficient
Solution Approach 1:
The patent applies dynamic rotation speed changes during the coating process. The substrate rotation speed is adjusted through multiple phases: initial high-speed rotation (first rotation number) to diffuse the resist solution, then deceleration to a second rotation number to improve fluidity, followed by acceleration to a third rotation number to diffuse to the whole surface, and finally deceleration to a fourth rotation number (500 rpm or less) to prevent drying at the outer edge. This dynamic adjustment resolves the contradiction by optimizing fluid distribution at different stages.
Solution Approach 2:
The patent changes physical parameters (rotation speed and supply timing) to achieve uniform coating with reduced material. By controlling the fourth rotation number to be 500 rpm or less during a specific phase, the system prevents excessive drying at the outer peripheral edge while maintaining overall uniformity, enabling reduced supply amounts without sacrificing coating quality.
2Productivity
If the supply amount of resist solution is reduced, then the coating efficiency is improved, but the film thickness at outer peripheral edge becomes insufficient
Solution Approach 1:
The patent uses dynamic rotation control with at least four distinct rotation phases to achieve efficient coating with reduced material. The fourth rotation phase at 500 rpm or less is critical for preventing film thickness reduction at the outer edge while maintaining overall productivity through optimized supply timing and rotation speed variations.
Solution Approach 2:
The patent maintains continuous supply of resist solution from the first step through the middle of the second step or during the first step, ensuring uninterrupted coating action. This continuous supply combined with dynamic rotation control ensures that even with reduced total supply amount, the film thickness remains uniform across the entire substrate surface.
3Loss of time
If the rotation speed is increased to diffuse the resist solution quickly, then the coating time is reduced, but the fluidity of resist solution deteriorates and drying occurs at outer peripheral edge
Solution Approach 1:
The patent employs periodic action through multiple rotation phases with different speed characteristics. The sequence includes high-speed rotation for rapid diffusion, deceleration for fluidity improvement, acceleration for surface coverage, and final deceleration to prevent drying. This periodic variation in rotation speed resolves the contradiction between coating time and fluidity maintenance.
Solution Approach 2:
The patent dynamically adjusts rotation speed through at least four distinct phases, with the fourth phase maintaining speed at 500 rpm or less to preserve fluidity and prevent drying at the outer peripheral edge. This dynamic control achieves both time efficiency and fluidity maintenance.
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 method allows for uniform coating of the substrate surface while significantly reducing the supply amount of the resist solution, preventing film thickness lowering at the outer peripheral edge and improving fluidity, thus enhancing coating efficiency.
Implementation Method 1
a so-called spin coating method is frequently used in which a resist solution is supplied from a nozzle to a central portion of the rotating wafer and a centrifugal force is utilized to diffuse the resist solution over the wafer
Data Source
AI summary
A coating treatment method includes: a first step of rotating a substrate at a first rotation number; a second step of rotating the substrate at a second rotation number being slower than the first rotation number; a third step of rotating the substrate at a third rotation number being faster than the second rotation number and slower than the first rotation number; a fourth step of rotating the substrate at a fourth rotation number being slower than the third rotation number; and a fifth step of rotating the substrate at a fifth rotation number being faster than the fourth rotation number. A supply of a coating solution to a central portion of the substrate is continuously performed from the first step to a middle of the second step or during the first step, and the fourth rotation number is more than 0 rpm and 500 rpm or less.