Conductive Diamond Anode for Sulfuric Acid Electrolysis
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Solution Overview
Problem
Conventional sulfuric acid electrolytic cells with conductive diamond electrodes face issues of mechanical weakness, corrosion, and inefficient performance due to pressure and stress from electrolyte solutions, leading to potential breakage and leakage, especially when used in semiconductor cleaning processes where high purity is required.
Innovation Solution
A sulfuric acid electrolytic cell design featuring a conductive diamond anode with a diamond film on a silicon substrate, supported by a rigid current collector and sealed with gaskets, and a diaphragm separating the anode and cathode compartments, along with a recycling system for the treatment liquid, enhances mechanical strength and prevents corrosion, ensuring high durability and efficient persulfuric acid production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin conductive diamond film is formed on a substrate to enable electrochemical reactions, then chemical stability and electrolytic oxidation efficiency are improved, but mechanical strength deteriorates due to the thin film's dependence on substrate strength
Solution Approach 1:
The invention uses a composite structure combining a conductive substrate (silicon or metal plate) with a conductive diamond film. The substrate provides mechanical strength while the diamond film provides chemical stability and electrochemical reactivity. This composite approach resolves the contradiction by allowing the thin diamond film to maintain its chemical properties while relying on the substrate for structural integrity.
Solution Approach 2:
The conductive substrate acts as an intermediary between the thin diamond film and the external environment. It provides mechanical support to the fragile thin film while allowing electrochemical reactions to occur at the diamond film surface. The substrate mediates the mechanical stress that would otherwise directly affect the thin diamond layer.
2Ease of operation
If conventional electrolytic cells are used with conductive diamond electrodes, then electrochemical reactions can occur, but mechanical weakness leads to breakage and leakage under pressure and stress from electrolyte solutions
Solution Approach 1:
The electrolytic cell uses composite electrode structures where robust metal or silicon substrates provide mechanical strength to withstand electrolyte pressure, while conductive diamond films on the surface enable efficient electrochemical reactions. This composite design prevents breakage and leakage while maintaining operational effectiveness.
Solution Approach 2:
The electrode is segmented into two functional parts: the substrate that handles mechanical stress and the diamond film that handles chemical reactions. This segmentation allows each component to optimize its specific function without compromising the other, improving overall reliability.
3Productivity
If industrial-scale persulfate production is used for cleaning, then cost-effective cleaning is achieved, but impurity levels exceed 1000 times the acceptable level for semiconductor cleaning processes
Solution Approach 1:
The invention applies local quality control by using highly purified sulfuric acid as feedstock and controlling the electrolytic process conditions to minimize impurity generation. The local purity of the produced persulfuric acid meets semiconductor industry requirements while maintaining effective cleaning capability.
Solution Approach 2:
The invention changes critical process parameters including using high-purity sulfuric acid feedstock, controlling electrolysis conditions, and selecting appropriate electrode materials to produce persulfuric acid with purity levels suitable for semiconductor cleaning, distinguishing it from conventional industrial persulfate production.
4Reliability
If CVD method is used to form conductive diamond film at over 1000 degrees Celsius, then film adherence and chemical stability are improved, but substrate corrosion and phase transition occur due to thermal stress
Solution Approach 1:
The invention selects substrates with thermal expansion coefficients matched to diamond to minimize thermal stress during CVD deposition at high temperatures. This thermal compatibility prevents substrate corrosion and phase transition while ensuring good film adherence through controlled thermal processing.
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 design provides a mechanically robust and durable sulfuric acid electrolytic cell that withstands severe electrolysis conditions, prevents corrosion, and maintains high efficiency in producing persulfuric acid for semiconductor cleaning, meeting the stringent purity requirements of the semiconductor industry.
Implementation Method 1
forms a solution containing chemical species of oxidation nature through electrolysis of sulfuric acid
Implementation Method 2
removal of used photoresist, metals and organic contaminants is commonly performed by SPM in which cleaning is carried out with mixed liquid of sulfuric acid and hydrogen peroxide
Implementation Method 3
an anode compartment and a cathode compartment separated by a diaphragm
Implementation Method 4
the substrate is required to withstand these environments with no volume change from corrosion or phase transition
Implementation Method 5
Removal effect of SPM is reported to be deriving from strong oxidizing power of persulfuric acid and mixing heat generated through oxidation while sulfuric acid is mixed with hydrogen peroxide
Data Source
AI summary
In a sulfuric acid electrolytic cell to electrolyze sulfuric acid supplied to an anode compartment and a cathode compartment comprising a diaphragm, said anode compartment and said cathode compartment separated by said diaphragm, a cathode provided in said cathode compartment and a conductive diamond anode provided in said anode compartment, as said conductive diamond anode, a conductive diamond film is formed on the surface of said conductive substrate, the rear face of said conductive substrate is pasted, with conductive paste, on an current collector comprising a rigid body with size equal to, or larger than, said conductive substrate, an anode compartment frame constituting said anode compartment is contacted via gasket with the periphery on the side of the conductive diamond film of said diamond anode, said diaphragm is contacted with the front face of said anode compartment, further, with the front face of said diaphragm, the cathode compartment frame constituting said cathode compartment, a gasket, and said cathode are contacted in sequence, the rear face of said cathode is pasted with conductive paste to the current collector comprising a rigid body with size equal to, or larger than, said cathode and electric power is supplied from one current collector to the other current collector via said conductive paste.