Ultrapure Water Mixing Control for ppb-Level Solute Concentration
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Solution Overview
Problem
Conventional methods for supplying dilute wash water for semiconductor wafer washing and rinsing fail to accurately control solute concentrations, particularly at low levels, due to complexity in reagent management and sensitivity limitations, leading to inconsistent liquid quality.
Innovation Solution
A method and apparatus that mix a conductive first liquid and a non-conductive second liquid at specified ratios with ultrapure water, using conductivity or resistivity meters for precise control, enabling efficient production and supply of water with specified concentrations, even at ppb levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If colorimetric titration methods are used to measure H2O2 concentration, then concentration measurement is possible, but reagent management and adjustment become complicated
Solution Approach 1:
The patent extracts the measurement function from complex chemical titration methods and implements it through a simple conductivity sensor that directly measures ionic concentration in real-time, eliminating the need for reagent management while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical/chemical titration system with an electrical measurement system using conductivity sensors, which detect ionic concentration through electrical properties rather than chemical reactions, thereby simplifying the measurement process
2Manufacturing precision
If PID control is used to control solute concentration, then concentration control is attempted, but control at ppb level is not sufficient and trace concentration range cannot be controlled
Solution Approach 1:
The patent changes the measurement parameter from chemical titration to electrical conductivity measurement, which provides sufficient sensitivity and precision for trace concentration control at ppb levels, enabling accurate monitoring and control that PID control alone cannot achieve
Solution Approach 2:
The patent implements real-time feedback control using conductivity sensors that continuously monitor ionic concentration and adjust the dosing rate accordingly, providing the precise feedback necessary for controlling trace concentrations at ppb levels
3Stability of the object's composition
If dilute wash water is produced in advance and stored in a large tank, then liquid stabilization is improved, but equipment space requirements increase and practicality decreases
Solution Approach 1:
The patent performs preliminary mixing of H2O2 and acid/alkali in a small volume reservoir to create a stable mixed solution, then maintains composition stability through real-time conductivity monitoring and automated dosing adjustments, eliminating the need for large storage tanks while preserving liquid stability
Solution Approach 2:
The system uses real-time conductivity measurements to automatically adjust the dosing rate, allowing the system to self-regulate and maintain composition stability without requiring large buffer volumes, thereby achieving stability with minimal storage space
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 allows for accurate and stable supply of water with precise solute concentrations, ensuring high-quality liquid for semiconductor processing by leveraging the responsiveness of conductivity or resistivity meters for real-time monitoring and control.
Implementation Method 1
a conductivity or specific resistance of the ultrapure water after the addition satisfies a specified value
Data Source
AI summary
Provided are a method for supplying water of specified concentration, including: a step of adding at least two liquids, a conductive first liquid and a non-conductive second liquid, to ultrapure water to produce water of specified concentration containing a first liquid-component and a second liquid-component at specified concentrations, in which a mixed solution in which the first liquid and the second liquid are mixed at a specified mixing ratio in advance is prepared; and the mixed solution is added to the ultrapure water so that a conductivity or specific resistance of the ultrapure water after the addition satisfies a specified value, and an apparatus therefor.