Marangoni Wafer Drying via Surface Tension Gradients
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Solution Overview
Problem
Conventional high-speed spin processes for cleaning and drying semiconductor wafers can induce charge and damage, and are difficult to control, leading to low particle clean rates and wafer defects, especially when dealing with pyrophoric and toxic doping agents and contaminants.
Innovation Solution
A cleaning tool utilizing the Marangoni effect with a combination of de-ionized water and isopropyl alcohol/nitrogen spray, which reduces the need for high spin speeds by using surface tension gradients to move water away from the wafer surface, allowing for effective cleaning and drying at lower speeds of up to 1600 RPM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high speed spin process is used for cleaning and drying semiconductor wafers, then cleaning efficiency is improved, but wafer charge and damage increase
Solution Approach 1:
The patent replaces the conventional high-speed mechanical spin drying system with a chemical-Marangoni based drying system. Instead of relying on centrifugal force from high-speed rotation, the invention uses surface tension gradients created by isopropyl alcohol to drive liquid flow and achieve drying at low spin speeds (300-1600 RPM), thereby eliminating mechanical-induced wafer charge and damage while maintaining cleaning efficiency
Solution Approach 2:
The patent introduces isopropyl alcohol as an intermediary substance that facilitates the drying process. The isopropyl alcohol creates surface tension gradients (Marangoni effect) that drive liquid flow across the wafer surface, enabling effective drying without requiring high spin speeds. This intermediary chemical mechanism substitutes for the mechanical force that would otherwise be needed
2Speed
If high speed spin process is used for drying semiconductor wafers, then drying speed is improved, but water spray control becomes difficult
Solution Approach 1:
The patent replaces mechanical spin-induced water removal with a chemically-driven Marangoni flow system. The surface tension gradients created by isopropyl alcohol naturally drive water flow and evaporation at controlled rates, providing superior spray control while maintaining effective drying speeds without requiring high rotational velocity
3Object-affected harmful factors
If low spin speed is used for cleaning semiconductor wafers, then wafer charge is reduced, but particle clean rate decreases
Solution Approach 1:
The patent introduces isopropyl alcohol as a chemical intermediary that enhances the cleaning mechanism. The Marangoni effect created by the isopropyl alcohol generates strong surface flow patterns that effectively remove particles from the wafer surface even at low spin speeds, thereby maintaining high particle clean rates without requiring high rotational speeds that would induce wafer charge
Solution Approach 2:
The patent changes the physical-chemical parameters of the cleaning system by introducing isopropyl alcohol, which alters surface tension characteristics. This parameter change creates Marangoni flows that provide enhanced cleaning capability at low spin speeds, decoupling the relationship between spin speed and particle clean rate that exists in conventional systems
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 approach significantly reduces plasma-induced damage, improves particle clean rates, and minimizes wafer charging, while maintaining high surface dry efficiency, thus enhancing the semiconductor manufacturing process.
Implementation Method 1
A cleaning tool utilizing the Marangoni effect with a combination of de-ionized water and isopropyl alcohol/nitrogen spray, which reduces the need for high spin speeds by using surface tension gradients to move water away from the wafer surface
Data Source
AI summary
A method of cleaning and drying a semiconductor wafer including inserting a semiconductor wafer into a chamber of a cleaning tool, spinning the semiconductor wafer in a range of about 300 revolutions per minute to about 1600 revolutions per minute, and simultaneously spraying the semiconductor wafer with de-ionized water and a mixture of isopropyl alcohol and nitrogen.