Metal-Resist Cleaning Liquid With Liquid Strong Acid
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Solution Overview
Problem
Existing cleaning liquids for metal resists in semiconductor processing face challenges in effectively removing metal residues while preventing organic substance contamination and precipitation during drying, particularly when using solid acids like oxalic acid.
Innovation Solution
A cleaning liquid comprising a solvent and a liquid strong acid with a pH of 2.5 or less, preferably using organic solvents like propylene glycol methyl ethyl acetate and strong acids such as phosphoric acid, which are liquid at 20°C, to enhance metal removal properties and prevent organic residue formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a solid acid such as oxalic acid or benzenesulfonic acid is used in the cleaning liquid, then metal removing properties are improved, but the solid acid precipitates when the cleaning liquid is dried, causing organic substance to remain on the treated surface and contaminating the process apparatus
Solution Approach 1:
The patent changes the physical state parameter of the acid from solid to liquid by selecting liquid strong acids (sulfuric acid, phosphoric acid, methanesulfonic acid, trifluoroacetic acid) that remain liquid at 20°C. This parameter change prevents precipitation during drying while maintaining the strong acid's metal removal capability, thereby eliminating organic substance residue and apparatus contamination.
2Object-generated harmful factors
If a liquid acid such as acetic acid is used instead of a solid acid to prevent precipitation at the time of drying, then organic substance residual amount is reduced, but metal removing properties are insufficient compared to when a solid acid is used
Solution Approach 1:
The patent changes the acid strength parameter by selecting liquid strong acids with low pKa values (sulfuric acid pKa: -3, phosphoric acid pKa: 2.1, methanesulfonic acid pKa: 0.4, trifluoroacetic acid pKa: 0.5) instead of weak liquid acids like acetic acid (pKa: 4.76). This parameter change maintains strong metal removal capability while preventing precipitation, achieving both high metal removing properties and low organic substance residue.
3Manufacturing precision
If the pH value of the cleaning liquid is lowered to enhance metal removal, then metal removing properties are improved, but the risk of apparatus contamination increases due to precipitation
Solution Approach 1:
The patent changes the physical state parameter of the acid component from solid to liquid, enabling the use of strong acids at low pH values (pH ≤ 2.5 after 10-fold dilution) without causing precipitation. This parameter change allows aggressive metal removal while eliminating the contamination risk associated with solid acid precipitation during the drying process.
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 provides improved metal removal efficiency with reduced organic residue and prevents apparatus contamination, ensuring effective cleaning of metal resists without precipitation.
Implementation Method 1
a strong acid that is liquid at 20° C., in which a pH value, which is measured with a pH meter, of a liquid formed by subjecting the cleaning liquid to a 10-fold dilution with pure water is 2.5 or less
Data Source
AI summary
A metal resist remover containing a solvent and a strong acid that is liquid at 20° C., in which a pH value, which is measured with a pH meter, of a liquid formed by subjecting the cleaning liquid to a 10-fold dilution with pure water is 2.5 or less.