Semiconductor Coating Method for Uniform Thick Films
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Solution Overview
Problem
Conventional coating methods for semiconductor substrates struggle to achieve uniform thickness of thick coating liquid films at low rotation speeds, leading to non-uniform film distribution and difficulty in scattering the coating liquid from the periphery edge, resulting in thicker films at the edge and degraded uniformity.
Innovation Solution
A coating method involving a dispensing step for coating liquid application, a building-up step using centrifugal force to push excess liquid to the periphery edge, and a gas blowing step to exhaust excess liquid before drying, using a gas nozzle to balance the film thickness and prevent edge buildup due to surface tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the rotation speed is decreased to obtain a thicker coating liquid film, then the film thickness increases, but the uniformity in thickness of the coating liquid film on the wafer is degraded
Solution Approach 1:
Gas is blown to the periphery edge of the substrate before the coating liquid is completely dried by rotation, as a preliminary action to prevent the buildup of excess coating liquid at the periphery edge. This preemptive measure eliminates the mountain-shaped thickness distribution that would otherwise occur when rotating at low speeds to achieve thick film formation.
2Volume of moving object
If the rotation speed is decreased to allow the coating liquid film to become thicker, then the film thickness increases, but the centrifugal force acting on the coating liquid significantly decreases, leading to difficulty in scattering of the coating liquid from the periphery edge
Solution Approach 1:
Gas is introduced as an intermediary substance to act on the coating liquid at the periphery edge. The gas flow provides an additional force mechanism to scatter and remove excess coating liquid from the periphery edge, compensating for the insufficient centrifugal force that results from low rotation speeds required for thick film formation.
3Volume of moving object
If the viscosity of the coating liquid is increased to obtain a thick film, then the film thickness increases, but high-power pump, enlarged diameter of supply pipe, enlarged diameter of drain pipe, cup cleaning, and contamination of minute bubbles within the film occur
Solution Approach 1:
Instead of changing the viscosity parameter of the coating liquid to achieve thick film formation, the rotation speed parameter is changed (decreased) to allow thicker film formation. Additionally, gas blowing is introduced as a new parameter to control the distribution and scattering of coating liquid, enabling thick uniform film formation without increasing viscosity and its associated problems.
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 achieves a uniform thickness of the coating liquid film while forming it thick, by controlling rotation speed and gas blowing parameters to ensure even distribution and prevent edge thickening, thereby improving film uniformity and planarity.
Implementation Method 1
rotating the substrate with a holding rotator to form a liquid film of the coating liquid on the substrate and pushing at least a part of an excess of the coating liquid toward a periphery edge of the substrate with a centrifugal force cause by rotation of the substrate
Implementation Method 2
blowing gas through a gas nozzle to the periphery edge of the substrate before drying of the coating liquid on the substrate by the rotation of the substrate is finished to exhaust the excess of the coating liquid building up at the periphery edge outside the substrate
Data Source
AI summary
A substrate is rotated with a holding rotator to form a coating liquid film on the substrate, and at least a part of an excess of the coating liquid is pushed out toward a periphery edge of the substrate by a centrifugal force caused by the rotation of the substrate to build up the excess of the coating liquid along the periphery edge of the substrate. Moreover, gas is blown to the periphery edge of the substrate through a gas nozzle to exhaust the excess of the coating liquid building up at the periphery edge. Blowing the gas toward the periphery edge of the substrate through the gas nozzle makes the coating liquid unbalanced that builds up without being exhausted outside the substrate due to its surface tension. Accordingly, the rotation achieves the coating liquid film having a uniform thickness while the coating liquid film is formed to be thick.