Rotating Substrate Drying via Surface Tension Gradient
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Solution Overview
Problem
Existing Rotagoni drying systems and methods are inadequate in completely removing liquids from semiconductor wafers, leading to watermark formation, decreased device yield, and increased process times, particularly at the edge of the substrate, due to evaporation rather than surface tension gradient (STG) drying and splash back issues.
Innovation Solution
A novel drying system and method involving a dryer assembly with a DIW and N2/IPA vapor dispensing nozzles, where the DIW nozzle leads the N2/IPA nozzle during a sweeping motion, utilizing proportional valves to control the flow and maintaining a consistent DIW film on the substrate, and employing a hydrophobic splash guard to minimize splash back, ensuring STG-driven drying across the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional evaporation drying is used, then the drying process is simple, but watermarks and residue form on the substrate surface
Solution Approach 1:
The patent replaces thermal evaporation with mechanical Marangoni flow driven by surface tension gradients. The drying fluid creates a surface tension gradient that mechanically pulls liquid across the substrate surface and off the edge, eliminating evaporation-related watermarks and residue while achieving complete liquid removal.
Solution Approach 2:
The patent changes the physical parameter of surface tension by introducing a drying fluid with different surface tension properties than the liquid being removed. This creates a surface tension gradient that drives the Marangoni flow, transforming the drying mechanism from passive evaporation to active fluid-driven transport.
2Manufacturing precision
If Marangoni drying is used to eliminate watermarks, then substrate surface cleanliness improves, but process time increases
Solution Approach 1:
The patent implements continuous Marangoni drying by maintaining a continuous supply of drying fluid across the substrate surface. The drying fluid continuously generates surface tension gradients that drive liquid removal, eliminating the need for intermittent heating or multiple drying stages, thereby reducing total process time while maintaining complete liquid removal.
3Productivity
If drying fluid is applied to accelerate liquid removal, then drying speed increases, but splash back occurs reducing effectiveness
Solution Approach 1:
The patent introduces a hydrophobic barrier layer as an intermediary between the drying fluid and the liquid being removed. This hydrophobic layer allows the drying fluid to apply stress to accelerate liquid removal while preventing direct contact between the drying fluid and the liquid, thereby eliminating splash back and maintaining drying effectiveness.
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 solution effectively minimizes watermarks and residue, increases device yield, and reduces process time by ensuring complete liquid removal through STG-driven drying, while the hydrophobic splash guard reduces splash back, enhancing the overall efficiency and cleanliness of the drying process.
Implementation Method 1
The drying fluid is absorbed along the surface of the liquid, with the concentration of the absorbed vapor being higher at the tip of the meniscus than in the bulk of the liquid. The increased concentration of absorbed vapor results in the surface tension being lower at the tip of the meniscus than in the bulk of the liquid. This differential in surface tension causes the liquid to flow from the meniscus toward the bulk bath liquid
Implementation Method 2
This differential in surface tension causes the liquid to flow from the meniscus toward the bulk bath liquid as the substrates are withdrawn from the liquid bath. Such a flow is known as a 'Marangoni' flow
Implementation Method 3
A plurality of substrates are immersed in a bath of liquid
Data Source
AI summary
A system for drying a surface of a substrate is provided. The system for drying a surface of a substrate comprising: a rotary support; a first dispenser fluidly coupled to a source of liquid, the first dispenser positioned above the surface of the substrate so as to be capable of applying a film of the liquid to the surface of the substrate; a second dispenser fluidly coupled to a source of drying fluid with a supply line, the second dispenser positioned above the surface of the substrate so as to be capable of applying the drying fluid to the surface of the substrate; and a proportional valve operably coupled to the supply line between the second dispenser and the source of drying fluid, the proportional valve capable of being incrementally adjusted from a closed position to an open position.