Supercritical IPA Drying for Semiconductor Substrates
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Solution Overview
Problem
Conventional drying methods for semiconductor substrates, such as rotary drying and IPA drying, can cause fine patterns to merge due to surface tension, and supercritical CO2 drying may lead to decomposition reactions that degrade semiconductor device electrical characteristics.
Innovation Solution
A supercritical drying method using isopropyl alcohol (IPA) where the substrate is placed in a chamber with an inert gas purge to prevent oxidation, and the IPA is heated to a supercritical state and then discharged, preventing etching and maintaining the integrity of the semiconductor material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional drying methods (rotary drying or IPA drying) are used, then the drying process is simple and fast, but fine patterns on the wafer merge together due to surface tension of remaining liquid
Solution Approach 1:
The patent changes the physical parameters of the drying environment by introducing a controlled atmosphere with specific humidity and temperature conditions. This modifies the evaporation rate and surface tension characteristics, allowing liquid to recede without causing pattern merging while maintaining drying efficiency.
Solution Approach 2:
The patent employs a controlled atmospheric environment within the drying chamber, using inert or low-reactivity gas composition to prevent unwanted chemical reactions during drying. This controlled atmosphere also helps manage surface tension effects and prevents liquid bridging between fine patterns.
2Manufacturing precision
If supercritical CO2 drying is used to eliminate surface tension, then pattern separation is improved, but CO2 decomposition reactions occur that degrade semiconductor device electrical characteristics
Solution Approach 1:
The patent replaces the problematic supercritical CO2 drying method with a conventional drying process operating under controlled atmospheric conditions. This substitutes a harmful but effective method with a safer, conventional approach that achieves sufficient pattern separation without causing decomposition reactions.
Solution Approach 2:
The patent introduces a controlled inert atmosphere in the drying chamber to prevent oxidative decomposition reactions. By maintaining specific gas composition and environmental conditions, the method eliminates the harmful chemical reactions associated with supercritical CO2 while preserving the benefits of improved pattern separation.
3Ease of manufacture
If alcohol is used as substitution liquid for rinse pure water, then the liquid can be easily put into supercritical state, but at high pressure and temperature the alcohol undergoes decomposition reaction that etches metal material on the substrate
Solution Approach 1:
The patent abandons the supercritical alcohol drying approach in favor of conventional drying with controlled atmosphere. This replaces a method that is easy to implement but causes harmful etching with a conventional approach that avoids decomposition reactions entirely.
Solution Approach 2:
The patent uses a controlled inert atmosphere during the drying process to prevent alcohol decomposition and subsequent etching of metal materials. By eliminating oxygen and other reactive components from the drying environment, the method prevents harmful chemical reactions 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 etching of metal films on semiconductor substrates, thereby preserving the electrical characteristics of the devices and avoiding pattern merging issues.
Implementation Method 1
discharging oxygen from the chamber by supplying an inert gas into the chamber
Implementation Method 2
putting the alcohol into a supercritical state by increasing temperature in the chamber to a critical temperature of the alcohol or higher
Implementation Method 3
lowering pressure in the chamber and changing the alcohol from the supercritical state to a gaseous state
Data Source
AI summary
According to one embodiment, a supercritical drying method comprises cleaning a semiconductor substrate with a chemical solution, rinsing the semiconductor substrate with pure water after the cleaning, changing a liquid covering a surface of the semiconductor substrate from the pure water to alcohol by supplying the alcohol to the surface after the rinsing, guiding the semiconductor substrate having the surface wetted with the alcohol into a chamber, discharging oxygen from the chamber by supplying an inert gas into the chamber, putting the alcohol into a supercritical state by increasing temperature in the chamber to a critical temperature of the alcohol or higher after the discharge of the oxygen, and discharging the alcohol from the chamber by lowering pressure in the chamber and changing the alcohol from the supercritical state to a gaseous state. The chamber contains SUS. An inner wall face of the chamber is subjected to electrolytic polishing.