Semiconductor Cleaning Liquid for Post-CMP Particle Removal
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Solution Overview
Problem
Current cleaning solutions for semiconductor substrates after chemical mechanical polishing (CMP) struggle to effectively remove fine particles without corroding metals like Cu and often retain alkali metals on the surface, leading to re-attachment issues and corrosion.
Innovation Solution
A cleaning liquid comprising an inorganic alkali, a chelating agent, an anionic surfactant, and an amine oxide type surfactant is used, which maintains a pH of 8 or more, ensuring efficient removal of fine particles and preventing alkali metal retention by enhancing wettability and reducing zeta potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an acidic cleaning liquid is used, then colloidal silica particles are positively charged and attracted to the negatively charged substrate surface, making particle removal difficult, but if an alkaline cleaning liquid is used, then both colloidal silica and substrate surface are negatively charged creating repulsion that facilitates particle removal, however Cu forms passive films and corrosion increases
Solution Approach 1:
The patent changes the pH parameter of the cleaning liquid to alkaline conditions (pH 9-11) to create negative charge on both colloidal silica particles and substrate surface, generating electrostatic repulsion that facilitates particle removal. Simultaneously, the patent controls the alkalinity level and uses buffered solutions to prevent excessive corrosion of Cu wiring by maintaining pH within a specific range.
Solution Approach 2:
The patent introduces surfactants as intermediary substances that adsorb onto particle surfaces and substrate surfaces, modifying their surface properties. The surfactants enhance the repulsive interaction between particles and substrate while providing protection to Cu surfaces, acting as a mediator that enables particle removal without direct harmful contact between alkaline solution and Cu.
2Manufacturing precision
If conventional cleaning liquids are used, then fine particles can be removed, but alkali metals are retained on the substrate surface causing re-attachment issues
Solution Approach 1:
The patent extracts and removes alkali metals from the substrate surface by using chelating agents that selectively bind to metal ions. The chelating agents form stable complexes with alkali metal ions, enabling their extraction and removal from the substrate surface through rinsing, thereby preventing re-attachment of particles.
Solution Approach 2:
The patent replaces simple mechanical rinsing with a chemical mechanism involving chelating agents that actively capture and remove alkali metals. This chemical substitution enhances the removal efficiency beyond what mechanical flushing alone could achieve.
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 effectively removes fine particles from semiconductor substrates post-CMP without corroding metals and prevents re-attachment, while minimizing alkali metal residue, thus enhancing cleaning efficiency and preventing corrosion.
Implementation Method 1
The surfactant plays an important role for enhancing an affinity of the cleaning liquid with a substrate surface which is subjective to cleaning. By enhancing the affinity of the cleaning liquid to the substrate surface due to the surfactant added in the cleaning liquid, it is also possible to enhance a cleaning performance which the cleaning liquid has.
Implementation Method 2
in the alkaline aqueous solution, since abundant OH- is present, both the colloidal silica and the substrate surface are negatively charged, and an electric repulsive force acts, so that it becomes easy to remove the colloidal silica.
Implementation Method 3
A cleaning liquid comprising an inorganic alkali, a chelating agent, an anionic surfactant, and an amine oxide type surfactant, which together enhance the affinity and cleaning efficacy while preventing alkali metal retention
Data Source
AI summary
An object of the present invention is to provide a good cleaning liquid for semiconductor device which is used after a CMP step, and the present invention relates to a cleaning liquid for semiconductor device containing the following components (1) to (5) or (1)′ to (4)′:(1) an inorganic alkali;(2) a chelating agent;(3) an anionic surfactant selected from sulfonic acid type and sulfuric acid type anionic surfactants;(4) an amine oxide type surfactant; and(5) water, or(1)′ an inorganic alkali;(2)′ a carboxyl group-containing chelating agent;(3)′ an anionic surfactant selected from a benzenesulfonic acid substituted with an alkyl group having from 8 to 20 carbon atoms and a salt thereof; and(4)′ water.