Supercritical Drying Apparatus for Semiconductor Substrate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Supercritical drying methods for semiconductor substrates face issues with particle deposition due to the surface tension of liquids during the drying process, particularly when transitioning from a supercritical CO2 fluid to a gas, which can cause drying marks and re-absorption of IPA residues.
Innovation Solution
A method involving the use of a supercritical drying apparatus that substitutes IPA on a semiconductor substrate with a supercritical CO2 fluid, followed by a baking treatment with oxygen or ozone gas to eliminate organic components and reduce particle deposition, by shifting the CO2 from a supercritical state directly to a vapor state, thereby preventing capillary forces and minimizing damage to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a drying treatment is performed by substituting pure water with isopropyl alcohol (IPA), then the drying efficiency is improved, but the pattern on the wafer is collapsed by surface tension of the liquid
Solution Approach 1:
The patent utilizes the phase transition of CO2 from supercritical state to gas state to achieve drying without liquid surface tension. By maintaining CO2 in a supercritical state during the drying process and then transitioning it to a gas state, the method eliminates the harmful surface tension effects that cause pattern collapse, while still achieving effective drying through the phase change mechanism.
Solution Approach 2:
The patent changes the physical parameters (temperature and pressure) of CO2 to achieve a supercritical state, which allows it to function as both a liquid and gas simultaneously. By controlling temperature above 31.1°C and pressure above 73.0 atm, CO2 enters a supercritical state that enables effective drying without the surface tension problems of conventional liquid drying methods.
2Manufacturing precision
If IPA is dissolved into supercritical CO2 fluid for drying, then surface tension is nullified, but particle deposition occurs due to cohesion and re-absorption of IPA residues
Solution Approach 1:
The patent introduces oxygen or ozone gas into the chamber to perform a baking treatment that oxidizes and removes IPA residues from the wafer surface. This oxidation process prevents the cohesion and re-absorption of IPA that would otherwise cause particle deposition, thereby eliminating the harmful effects while maintaining the benefits of supercritical drying.
Solution Approach 2:
The patent performs a preliminary baking treatment with oxygen or ozone gas before the final drying step. This preliminary action removes organic residues and prepares the surface to prevent subsequent particle deposition, ensuring that the main drying process occurs on a clean surface without the risk of IPA re-absorption.
3Productivity
If pressure is reduced to transition CO2 from supercritical state to gas, then drying is completed, but drying marks are generated by cohesion of IPA
Solution Approach 1:
The patent uses oxygen or ozone gas to oxidize IPA residues before the pressure reduction step. By removing the organic residues through oxidation, the method prevents the cohesion and re-absorption that would otherwise occur during pressure reduction, thereby completing the drying process without generating drying marks on the wafer surface.
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 effectively reduces particle deposition on the semiconductor substrate, prevents etching of metal films, and maintains the integrity of the substrate's minute structures by eliminating organic components through the baking treatment, thereby enhancing the drying process without damaging the substrate.
Implementation Method 1
IPA on the wafer is dissolved into the supercritical CO2 fluid by bringing a wafer of which a surface is wet with IPA into a state of being impregnated into carbon dioxide (supercritical CO2 fluid) which is in a supercritical state in a chamber
Implementation Method 2
the supercritical CO2 fluid into which the IPA is dissolved is gradually discharged from the chamber. After that, the wafer is dried by causing a phase shift from the supercritical CO2 fluid to a gas (vapor) by reducing a pressure and a temperature inside the chamber
Implementation Method 3
performing a baking treatment by supplying an oxygen gas or an ozone gas to the chamber after the reduction of the pressure inside the chamber
Data Source
AI summary
A supercritical drying method for a semiconductor substrate is disclosed. The method may include introducing the semiconductor substrate into a chamber in a state, a surface of the semiconductor substrate being wet with alcohol, substituting the alcohol on the semiconductor substrate with a supercritical fluid of carbon dioxide by impregnating the semiconductor substrate to the supercritical fluid in the chamber, and discharging the supercritical fluid and the alcohol from the chamber and reducing a pressure inside the chamber. The method may also include performing a baking treatment by supplying an oxygen gas or an ozone gas to the chamber after the reduction of the pressure inside the chamber.