Wafer Drying with Solid Film Sublimation to Prevent Pattern Collapse
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Solution Overview
Problem
Conventional supercritical drying methods using isopropyl alcohol (IPA) face challenges such as de-wetting, spilling, and premature drying, which can damage the topographical features of semiconductor wafers during the drying process, especially as feature sizes shrink.
Innovation Solution
A method involving the formation of a solid film on the wafer surface, which is then transferred to a supercritical fluid chamber where it sublimates into a supercritical phase, eliminating surface tension and allowing for safe removal without the risks associated with liquid vapor transformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isopropyl alcohol (IPA) is used to displace rinsing liquid on the wafer surface, then the rinsing liquid can be removed, but de-wetting, spilling, and premature drying occur which can damage the topographical features of semiconductor wafers
Solution Approach 1:
The patent changes the physical state parameter of the drying agent from liquid (IPA) to solid (CO2 ice/film). This phase change eliminates surface tension effects that cause de-wetting and spilling, while the sublimation process provides controlled drying without premature evaporation, thereby protecting delicate topographical features during the drying process
Solution Approach 2:
The patent utilizes the phase transition of carbon dioxide from solid (ice/film) directly to supercritical fluid through sublimation. This phase transition occurs without passing through the liquid state, eliminating surface tension-related problems and providing a controlled drying process that prevents damage to semiconductor wafer features
2Manufacturing precision
If conventional supercritical drying is used to remove IPA, then the rinsing liquid is removed, but pattern collapse can occur due to surface tension during liquid vapor transformation
Solution Approach 1:
The patent changes the drying mechanism from liquid vapor transformation to solid sublimation. By depositing CO2 as a solid film that directly sublimates to supercritical fluid, the process eliminates surface tension forces that cause pattern collapse, thereby maintaining manufacturing precision of sub-10nm semiconductor features
Solution Approach 2:
The patent employs sublimation (solid to supercritical fluid transition) instead of evaporation (liquid to gas transition). This phase transition eliminates the formation of liquid menisci and associated surface tension forces, preventing pattern collapse and preserving the geometric precision of delicate semiconductor structures
3Productivity
If faster drying methods are used to improve productivity, then processing time is reduced, but the risk of film loss and feature damage increases
Solution Approach 1:
The patent uses sublimation of solid CO2 film to supercritical fluid, which occurs uniformly throughout the film without the runaway evaporation characteristic of liquid drying. This provides faster drying than conventional methods while maintaining film integrity until complete sublimation, thereby improving productivity without sacrificing reliability
Solution Approach 2:
The patent replaces the mechanical/thermal process of liquid evaporation with a controlled sublimation process. The solid CO2 film sublimates uniformly under controlled conditions, providing rapid drying while the solid state maintains film adhesion and prevents premature loss, achieving both high productivity and reliability
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 prevents pattern collapse and facilitates faster, more reliable drying with reduced risk of film loss, enabling the preservation of delicate surface features during the drying process.
Implementation Method 1
removing, in the second processing chamber, the first solid film from the surface of the first wafer by sublimating the first solid film into the supercritical phase of the fluid
Implementation Method 2
pressurizing the fluid to flow through the second processing chamber in a supercritical phase
Data Source
AI summary
In one example, a method for wafer drying includes providing a surface of a first wafer, the surface of the first wafer including a liquid to be removed with a drying process. The method further includes replacing the liquid with a first solid film in a first processing chamber, the first solid film covering the surface of the first wafer. The method further includes transferring the first wafer from the first processing chamber to a second processing chamber. The method further includes processing the first wafer in the second processing chamber by flowing a supercritical fluid through the second processing chamber, where the supercritical fluid removes the first solid film.