Supercritical CO2 Drying for High Aspect Ratio Features
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Solution Overview
Problem
Current wet cleaning techniques for semiconductor substrates with high aspect ratio features face challenges in drying, leading to deformation and stiction due to capillary forces, which can damage the substrate and leave residues.
Innovation Solution
A substrate processing method involving the use of supercritical CO2 to displace solvents and dry the substrate, eliminating capillary forces by transitioning CO2 into a supercritical state and then to a gaseous phase, thereby preventing line stiction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet cleaning techniques are used to clean semiconductor substrates, then cleaning effectiveness is improved, but capillary forces during drying cause line stiction and substrate damage
Solution Approach 1:
The patent changes the physical state of CO2 from liquid to supercritical phase by adjusting temperature and pressure parameters. This parameter change eliminates the liquid-gas interface that creates capillary forces, thereby preventing line stiction while maintaining effective cleaning
Solution Approach 2:
The patent utilizes the phase transition of CO2 from liquid to supercritical state during the drying process. This phase transition allows CO2 to penetrate and displace cleaning liquids from high aspect ratio features without creating harmful capillary forces, then transitions back to gas phase for easy removal
2Productivity
If traditional drying methods are used after wet cleaning, then drying speed is improved, but deformation of high aspect ratio features occurs due to capillary pressure
Solution Approach 1:
The patent uses phase transition of CO2 to supercritical state and then to gas phase for drying. This eliminates liquid-gas interfaces within high aspect ratio features, removing capillary pressure that causes deformation, while maintaining fast drying speed through the efficient mass transfer properties of supercritical fluids
Solution Approach 2:
By changing temperature and pressure parameters to achieve supercritical state, the patent modifies the physical properties of the drying medium. This allows rapid drying without the formation of menisci that create capillary pressure, thus preventing feature deformation while maintaining high productivity
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 line stiction and residue formation by utilizing the unique properties of supercritical CO2 to penetrate and remove contaminants without surface tension, ensuring clean and undamaged high aspect ratio features.
Implementation Method 1
The liquid CO2 may be phase transitioned to supercritical CO2 in the processing chamber
Implementation Method 2
Additional liquid CO2 may be delivered to the processing chamber in an amount greater than a volume of the processing chamber to displace the solvent
Implementation Method 3
The substrate may be dried by isothermally depressurizing the processing chamber and exhausting gaseous CO2 from the processing chamber
Data Source
AI summary
A method for processing a substrate is disclosed. The method includes delivering a solvent to a processing chamber and delivering a substrate to the processing chamber. The amount of solvent present in the processing chamber may be configured to submerse the substrate. Liquid CO2 may be delivered to the processing chamber and the liquid CO2 may be mixed with the solvent. Additional liquid CO2 may be delivered to the processing chamber in an amount greater than a volume of the processing chamber to displace the solvent. The liquid CO2 may be phase transitioned to supercritical CO2 in the processing chamber and the substrate may be dried by isothermally depressurizing the processing chamber and exhausting gaseous CO2 from the processing chamber.