Substrate Drying Using Guard Switching and Low Surface-Tension Liquid
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Solution Overview
Problem
Existing substrate processing methods face challenges in satisfactorily drying the upper surface of substrates due to pattern collapse caused by high surface tension of rinse liquids and the generation of particles from splashed hydrophobic agents during the drying process.
Innovation Solution
A substrate processing method involving a substrate holding step with guards that switch states to receive and manage liquids, using a hydrophobic agent to lower surface tension, followed by a low surface-tension liquid to replace the hydrophobic agent, and precise guard positioning to prevent agent splashing and mist accumulation, ensuring effective drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If water is used as rinse liquid, then rinsing effect is improved, but surface tension is large causing pattern collapse
Solution Approach 1:
The patent changes the chemical composition parameter of the rinse liquid from water to a mixed solution containing isopropyl alcohol (IPA) and supercritical carbon dioxide. This parameter change reduces the surface tension of the liquid from water's high surface tension to a lower value, preventing pattern collapse while maintaining effective rinsing capability.
Solution Approach 2:
The patent uses a composite liquid system combining isopropyl alcohol and supercritical carbon dioxide. This composite material leverages the low surface tension properties of IPA and the unique solvation capabilities of supercritical CO2 to achieve both effective rinsing and pattern protection simultaneously.
2Object-affected harmful factors
If silylating agent is supplied to hydrophobize substrate, then pattern collapse is prevented, but particles are generated due to splashing and mist
Solution Approach 1:
The patent applies the silylating agent to hydrophobize the substrate surface before the rinsing step. This preliminary action ensures that the substrate surface is already protected against pattern collapse during subsequent liquid processing, eliminating the need for additional hydrophobizing steps that could generate more particles.
Solution Approach 2:
The patent extracts and removes the silylating agent and IPA from the substrate surface using supercritical carbon dioxide. The supercritical CO2 efficiently dissolves and carries away these liquid agents along with any potential particles, preventing their accumulation and subsequent particle generation during drying.
3Productivity
If spin drying is executed at high speed, then drying efficiency is improved, but rinse liquid enters pattern interior causing collapse
Solution Approach 1:
The patent changes the physical state parameter of the drying medium from liquid to supercritical fluid. Supercritical carbon dioxide maintains liquid-like density for effective drying while having gas-like diffusivity that allows it to penetrate and dry pattern interiors without the high surface tension forces that cause collapse during conventional liquid spin drying.
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 effectively lowers the surface tension of the applied liquid, suppresses particle generation, and ensures satisfactory drying of the substrate surface by managing the guards' states and liquid flow to prevent agent splashing and mist adherence.
Implementation Method 1
a hydrophobic agent supplying step of supplying to an upper surface of the substrate in a rotating state a hydrophobic agent which is a liquid for hydrophobizing the upper surface of the substrate
Implementation Method 2
a low surface-tension liquid supplying step of supplying a low surface-tension liquid to the upper surface of the substrate in the rotating state in order to replace the hydrophobic agent on the substrate by the low surface-tension liquid
Implementation Method 3
the silylating agent supplied to the upper surface of the substrate flows so as to spread from a center of the upper surface of the substrate to a peripheral edge thereof due to rotation of the substrate
Data Source
AI summary
A substrate processing method includes a substrate holding step of disposing a substrate at a position surrounded by a plurality of guards which have a first guard and a second guard in a plan view and of holding the substrate horizontally, a substrate rotating step of rotating the substrate around a vertical rotation axis which passes through a central portion of the substrate, a hydrophobic agent supplying step of supplying to the upper surface of the substrate in a rotating state a hydrophobic agent which is a liquid for hydrophobizing the upper surface of the substrate, a low surface-tension liquid supplying step of supplying the low surface-tension liquid to the upper surface of the substrate in the rotating state in order to replace the hydrophobic agent on the substrate by the low surface-tension liquid lower in surface tension than water, a first guard switching step of switching a state of the plurality of guards to a first state in which the first guard receives a liquid scattered from the substrate by moving at least one of the plurality of guards up and down before start of the low surface-tension liquid supplying step, and a second guard switching step of switching a state of the plurality of guards from the first state to a second state in which the second guard receives a liquid scattered from the substrate by moving the plurality of guards up and down during execution of the low surface-tension liquid supplying step.