Aqueous Acidic Cleaning Composition for Copper Oxide Removal
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Solution Overview
Problem
Copper redeposition during cleaning processes in copper-dual damascene microelectronic structures leads to defects, and existing cleaning compositions fail to prevent redeposition while maintaining the durability of metal capping layers like CoWP during etch and stripping processes.
Innovation Solution
A highly aqueous acidic cleaning composition with a pH of 4.3 to 5.5, comprising water, alkanolamine, metal chelating agents, tetraalkylammonium fluoride, and a non-ionic surfactant, optionally with a reducing agent, effectively removes copper oxide etch residue without redeposition and preserves the integrity of metal capping layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a diluted aqueous HF based acidic solution is used to remove copper oxide etch residue, then copper oxide removal is achieved, but copper redeposition occurs on the microelectronic structure
Solution Approach 1:
A chelating agent is introduced as an intermediary substance that binds to copper ions in the solution, preventing them from redepositing on the microelectronic structure. The chelating agent acts as a mediator between the copper ions and the substrate, ensuring copper remains in solution as stable complexes rather than precipitating out.
Solution Approach 2:
The pH of the cleaning composition is precisely controlled within the range of 4.3 to 5.5, which is optimized to maintain copper ions in a soluble state while preventing their reduction and redeposition. This specific pH parameter change creates conditions where copper oxide dissolves effectively but copper metal does not precipitate.
2Manufacturing precision
If acidic cleaning composition is used to remove copper oxide, then cleaning effectiveness is improved, but metal capping layer durability deteriorates
Solution Approach 1:
The pH is precisely controlled within the narrow range of 4.3 to 5.5, which is acidic enough to effectively dissolve copper oxide etch residue but not so acidic as to cause significant etching or damage to the metal capping layer. This optimized pH parameter achieves the balance between cleaning effectiveness and capping layer preservation.
Solution Approach 2:
The chelating agent serves as a protective intermediary that selectively binds to copper ions, allowing the acidic environment to remove copper oxide without the acid directly attacking the metal capping layer. The chelating agent mediates the interaction between the acidic solution and copper-containing species, protecting the capping layer from excessive acid exposure.
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 significantly reduces copper redeposition and maintains the durability of metal capping layers, ensuring effective cleaning of copper-dual damascene structures without defects, as demonstrated by lower redeposition scores and etch rate comparisons.
Implementation Method 1
comprising water, at least one alkanolamine or aminophenol, at least one metal chelating agent
Implementation Method 2
when employing a very diluted aqueous HF based acidic solution to produce a post-etch Cu-dual damascene structure on a silicon substrate, any CuOx and Cu(OH)2 films or residues on the surface are dissolved in the acidic fluoride environment
Implementation Method 3
As a result of copper vias in the structure, electrically connected through a P—N junction fabricated in the silicon substrate, there can occur significant undesirable redeposition (also called copper extrusion) where the copper vias are connected to the electron rich N doped regions by an electrochemical reaction as represented by the following reduction reaction equation. Cu2++2e−→Cu
Data Source
AI summary
A highly aqueous acidic cleaning composition for copper oxide etch removal from Cu-dual damascene microelectronic structures and wherein that composition prevents or substantially eliminates copper redeposition on the Cu-dual damascene microelectronic structure.