Persulfuric Acid Recycling System for Semiconductor Wafer Cleaning
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Solution Overview
Problem
Current methods for producing persulfuric acid in VLSI wafer cleaning processes face issues such as decreased oxidizing power due to self-decomposition, requiring continuous hydrogen peroxide supply, dilution, and frequent solution replacement, leading to inconsistent cleaning performance and high chemical consumption.
Innovation Solution
A sulfuric acid recycling system that regenerates persulfuric acid through electrolytic production of persulfate ions from sulfate ions, using a circulation line between a cleaning apparatus and an electrolytic reaction apparatus, with controlled temperature and electrode materials like conductive diamond to maintain high persulfuric acid concentration and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen peroxide solution is continuously supplied to compensate for persulfuric acid self-decomposition, then cleaning performance is maintained, but chemical consumption increases and solution must be frequently replaced
Solution Approach 1:
The patent changes the chemical composition parameters by replacing hydrogen peroxide with ozone as the oxidizing agent. Ozone reacts with sulfuric acid to form persulfuric acid in situ, changing the chemical reaction pathway and eliminating the need for continuous hydrogen peroxide supplementation. This parameter change resolves the contradiction by maintaining cleaning performance while reducing chemical consumption.
Solution Approach 2:
The system enables self-service by generating persulfuric acid in situ through the reaction of ozone with sulfuric acid. The persulfuric acid self-decomposes to provide cleaning action, and the system automatically replenishes it through continuous ozone generation, eliminating the need for external hydrogen peroxide supply and manual solution replacement.
2Quantity of substance
If high-concentration sulfuric acid and hydrogen peroxide are mixed at the beginning and hydrogen peroxide is added several times later, then persulfuric acid is produced, but the amount of persulfuric acid produced is limited and concentration is restricted
Solution Approach 1:
The patent implements continuity of useful action by continuously generating ozone and maintaining its reaction with sulfuric acid throughout the cleaning process. This continuous generation ensures a steady supply of persulfuric acid at high concentration, eliminating the limitation of batch-wise hydrogen peroxide addition and sustaining high cleaning performance throughout the entire operation.
3Reliability
If persulfuric acid solution is used for cleaning, then contaminants are removed effectively, but the solution decomposes and must be replaced frequently
Solution Approach 1:
The system implements self-service by automatically regenerating persulfuric acid through continuous ozone generation and reaction with sulfuric acid. The persulfuric acid that decomposes during cleaning is continuously replenished in situ, extending the solution's effective duration without requiring frequent manual replacement, thus maintaining both cleaning effectiveness and extended operation.
Solution Approach 2:
The patent changes the system from batch replacement to continuous regeneration by introducing ozone generation. This parameter change transforms the solution lifecycle from finite and replaceable to self-sustaining and continuously refreshed, extending the duration of action while maintaining cleaning 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
This system reduces sulfuric acid consumption, maintains consistent cleaning performance by regenerating high-concentration persulfuric acid on-site, and extends the solution replacement cycle, effectively removing contaminants from semiconductor wafers.
Implementation Method 1
an electrolytic reaction apparatus that performs electrolytic reaction to produce persulfate ions from sulfate ions contained in the solution
Data Source
AI summary
If incorporated in a cleaning system using persulfuric acid, the invention serves for continuous cleaning while increasing the persulfuric acid concentration adequately to ensure enhanced cleaning performance. The invention provides a feeding apparatus that feeds persulfuric acid to a cleaning apparatus. The cleaning system uses an electrolysis reactor 10 that regenerates the persulfuric acid solution by performing electrolytic reaction to produce persulfate ions from sulfate ions contained in the solution, and a circulation line 4, 5, 6 that circulates the persulfuric acid solution between the cleaning vessel 1 and the electrolysis reactor 10. Configured as above, the invention can provides a feeding apparatus. The cleaning system comprises said configuration and a cleaning vessel 1 that cleans objects 30 using a persulfuric acid solution 2 as cleaning fluid.