Substrate Drying Using Mixed Solvent Gradient
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Solution Overview
Problem
Existing substrate drying methods, particularly using IPA, fail to completely dry substrates with high aspect ratio recesses, leading to water marks and device deterioration due to incomplete removal of deionized water from these areas.
Innovation Solution
A substrate treatment method involving a cleaning step with deionized water, followed by a pre-drying treatment step using a mixture of deionized water and a more volatile organic solvent, with increasing organic solvent proportion to ensure complete replacement and drying, utilizing solvents like IPA, methanol, or HFEs to enhance evaporation and surface tension properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If IPA is used for drying the substrate by replacing deionized water, then the drying speed is improved, but the completeness of water removal in high aspect ratio recesses deteriorates
Solution Approach 1:
The invention changes the surface tension parameter of the drying liquid by using a mixed solvent system (IPA and HFE) instead of pure IPA. The HFE component significantly reduces the surface tension, enabling the liquid to penetrate high aspect ratio recesses effectively while maintaining fast evaporation characteristics of the IPA component.
Solution Approach 2:
The invention uses a composite solvent system combining IPA (isopropyl alcohol) and HFE (fluorinated ether). This composite liquid leverages the high volatility of IPA for fast evaporation and the low surface tension of HFE for deep penetration into recesses, achieving both fast drying speed and complete water removal.
2Productivity
If IPA is supplied to replace deionized water in recesses, then the replacement efficiency in upper portions is improved, but the penetration to bottom portions deteriorates
Solution Approach 1:
The invention modifies the surface tension parameter of the replacement liquid by adding HFE to IPA. This parameter change enables the liquid to wet and penetrate deep into high aspect ratio recesses, ensuring that deionized water is completely replaced even in bottom portions that are inaccessible to pure IPA.
3Ease of manufacture
If deionized water remains in recesses, then the substrate cleaning is simplified, but water mark formation and device deterioration occur
Solution Approach 1:
The invention changes the physical parameters of the drying agent by using a mixed solvent with optimized surface tension and volatility characteristics. This enables complete displacement of deionized water from recesses without requiring complex multi-step cleaning processes, preventing water mark formation while maintaining process simplicity.
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 effectively prevents water marks by ensuring complete replacement of deionized water with a more volatile organic solvent, leading to speedy and sufficient drying of substrates with high aspect ratio features, even those with hydrophobic surfaces.
Implementation Method 1
a pre-drying treatment liquid containing an organic solvent more volatile than the deionized water
Implementation Method 2
IPA does not easily mingle with the deionized water. Even if IPA is brought into contact with the deionized water, the deionized water only partly mingles with IPA in an interface between the deionized water and IPA
Implementation Method 3
a drying step of removing the pre-drying treatment liquid supplied to the major surface of the substrate after the pre-drying treatment step to dry the substrate
Data Source
AI summary
The substrate treatment method includes: a cleaning step of supplying deionized water to a major surface of a substrate to clean the substrate; a pre-drying treatment step of supplying a pre-drying treatment liquid containing an organic solvent more volatile than the deionized water to the major surface of the substrate after the cleaning step to replace deionized water remaining on the major surface with the pre-drying treatment liquid; and a drying step of removing the pre-drying treatment liquid supplied to the major surface of the substrate after the pre-drying treatment step to dry the substrate. The pre-drying treatment step includes: a deionized water/organic solvent mixture supplying step of supplying a mixture of the deionized water and the organic solvent as the pre-drying treatment liquid to the major surface of the substrate; and a mixing ratio changing step of increasing the proportion of the organic solvent in the mixture of the deionized water and the organic solvent during the deionized water/organic solvent mixture supplying step.