pH Buffered Cleaning Composition for Photoresist Residue Removal
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Solution Overview
Problem
Current cleaning compositions for semiconductor substrates are not effective for removing residues from newer materials like organosilica glass (OSG) dielectrics and other low-k dielectrics without damaging them, and they lack pH buffering and corrosion inhibition, which is crucial for maintaining substrate integrity.
Innovation Solution
A cleaning composition comprising water, a fluoride, a pH buffer system with an organic acid and a base in a specific ratio, and a corrosion inhibitor like ammonium thiosulfate or thioglycerol, which maintains a pH between 5 and 12 and is free of organic solvents, ensuring selective removal of residues without damaging the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If organic solvents are used in cleaning compositions, then photoresist residue removal effectiveness is improved, but damage to low-k dielectrics increases due to chemical reaction with organic and hydrogen substituents
Solution Approach 1:
The patent changes the chemical composition parameters by replacing organic solvents with water as the primary solvent and adding specific buffering agents (ammonium fluoride, glycine, triethanolamine) to control pH. This parameter change allows effective residue removal while preventing damage to low-k dielectrics by maintaining chemical compatibility
Solution Approach 2:
The patent introduces buffering agents as intermediaries that mediate between the cleaning action and the substrate. These buffers (ammonium fluoride, glycine, triethanolamine) act as protective intermediaries that enable effective cleaning while preventing direct harmful interactions with sensitive low-k dielectric materials
2Productivity
If highly acidic cleaning compositions are used, then cleaning power is improved, but corrosion of metal substrates increases
Solution Approach 1:
The patent changes the pH parameter from highly acidic to a controlled range (pH 7-10.5) by using buffering agents. This parameter change maintains sufficient cleaning power while preventing corrosion of metal substrates like copper, aluminum, and tungsten by eliminating extreme acidity
Solution Approach 2:
The patent converts the potential harm of strong cleaning agents into benefit by using mild alkaline buffering agents that provide cleaning power without corrosion. The buffering system transforms what would be harmful acidic cleaners into beneficial controlled-alkalinity cleaners that protect metal substrates
3Device complexity
If non-buffered cleaning compositions are used, then formulation simplicity is improved, but pH stability deteriorates leading to substrate damage
Solution Approach 1:
The patent implements self-service buffering where the cleaning composition contains its own pH stabilization system through ammonium fluoride, glycine, and triethanolamine. This buffering system automatically maintains pH stability during use without requiring external pH control mechanisms, providing both simplicity and stability
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 composition effectively removes residues from various substrates, including low-k and high-k dielectrics, with minimal etch rates of dielectric materials and compatibility with sensitive films like HSQ and TEOS, while preventing corrosion of metals like tungsten and copper.
Implementation Method 1
The RIE process typically leaves a residue or a complex mixture that may include re-sputtered oxide material, organic materials from photoresist
Implementation Method 2
U.S. Pat. No. 6,197,733 discloses a cleaning composition comprising water, an ammonium fluoride compound, and an amphoteric surfactant of which the cationic group is an ammonium salt and of which the anionic group is a carboxylate. The patent is silent regarding the pH of the composition.
Implementation Method 3
The wet chemical compositions formulated to remove the photoresist from the substrate should do so without damaging the substrate (e.g., corroding, dissolving, and/or dulling the surface of any metallic circuitry of the substrate)
Implementation Method 4
One common method of removing photoresist from a substrate is by wet chemical means
Data Source
AI summary
A residue cleaning composition for removing residue from a substrate includes: (a) water; (b) a fluoride; and (c) a pH buffer system including an organic acid, which is an aminoalkylsulfonic acid and/or an aminoalkylcarboxylic acid, and a base, which is an amine and/or a quaternary alkylammonium hydroxide. The composition is substantially free of an added organic solvent and has a pH ranging from about 5 to about 12. It is especially useful for remove residue from a substrate, resulting from etching a pattern through a photoresist into a substrate and heating the patterned substrate to a temperature sufficient to ash the photoresist.