Quaternary Alkyl Ammonium Hypochlorite Storage Stability
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Solution Overview
Problem
Current quaternary alkyl ammonium hypochlorite solutions for cleaning semiconductor wafers suffer from poor storage stability due to fluctuations in hypochlorite ion concentration and high metal impurity content, which affects their cleaning efficiency and yield in semiconductor manufacturing.
Innovation Solution
A method to produce a quaternary alkyl ammonium hypochlorite solution by controlling the pH and reducing ammonia and amines in the reaction step, and using a reaction vessel made of organic polymer materials to minimize metal impurities, without adding stabilizers like triazole or imidazole, thereby maintaining hypochlorite ion concentration and reducing metal content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a quaternary alkyl ammonium hypochlorite solution is prepared without stabilizers, then metal impurity content is reduced, but storage stability deteriorates due to hypochlorite ion concentration fluctuations
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pH of the quaternary alkyl ammonium hydroxide solution to be 10.5 or more before reacting with chlorine gas. This pH control parameter is critical because it determines the stability of hypochlorite ions in the final solution. By maintaining this specific pH range and controlling carbon dioxide concentration to 100 ppm or less, the patent achieves both low metal impurity content (using organic polymer reaction vessels) and high storage stability (through pH-controlled hypochlorite ion stability).
Solution Approach 2:
The patent employs composite materials by using reaction vessels made of organic polymer materials (such as PFA or PTFE) instead of conventional metal or glass vessels. This material selection prevents metal contamination from the reaction vessel itself, achieving ultra-low metal impurity content in the final cleaning solution while maintaining the chemical compatibility needed for stable hypochlorite solution preparation.
2Ease of manufacture
If carbon dioxide concentration is not controlled in the reaction step, then pH fluctuates, but hypochlorite ion concentration decreases leading to poor storage stability
Solution Approach 1:
The patent applies preliminary action by pre-controlling the carbon dioxide concentration in the reaction environment to 100 ppm or less before initiating the reaction between quaternary alkyl ammonium hydroxide and chlorine gas. This preliminary control of the atmospheric composition prevents carbon dioxide from dissolving into the solution and causing pH fluctuations that would lead to hypochlorite ion decomposition. By establishing this controlled environment beforehand, the patent ensures both ease of manufacture through straightforward pH management and long-term storage stability.
3Stability of the object's composition
If stabilizers like triazole or imidazole are added to maintain hypochlorite ion concentration, then storage stability improves, but metal impurity content increases
Solution Approach 1:
The patent applies the extraction principle by completely eliminating the need for stabilizer additives (such as triazole or imidazole) through alternative means. Instead of adding stabilizers that would introduce metal impurities, the patent extracts the root cause of instability by controlling the pH at 10.5 or more and carbon dioxide concentration at 100 ppm or less. This approach achieves storage stability through fundamental parameter control rather than additive-based stabilization, thereby maintaining ultra-low metal impurity content suitable for semiconductor manufacturing.
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 achieves high storage stability and reduced metal content in the quaternary alkyl ammonium hypochlorite solution, enhancing its cleaning performance and preventing yield reduction during semiconductor manufacturing processes.
Implementation Method 1
a reaction step in which the quaternary alkyl ammonium hydroxide solution is brought into contact with chlorine gas
Implementation Method 2
the amount of hypochlorite ions, which exert an oxidizing effect
Data Source
AI summary
Provided is a method of producing a quaternary alkyl ammonium hypochlorite solution with an excellent storage stability. Specifically, provided is a method of producing a quaternary alkyl ammonium hypochlorite solution, the method including: a preparation step in which a quaternary alkyl ammonium hydroxide solution is prepared and the concentration of amines in the quaternary alkyl ammonium hydroxide solution is set to 20 ppm by mass or less; and a reaction step in which the quaternary alkyl ammonium hydroxide solution is brought into contact with chlorine gas, wherein the concentration of carbon dioxide of a gas phase in the reaction step is 100 ppm by volume or less and the pH of a liquid phase in the reaction step is 10.5 or more.