CMP Slurry for Cobalt Interconnects
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Solution Overview
Problem
Cobalt-containing interconnects in semiconductor substrates are prone to oxidation and corrosion, leading to galvanic corrosion and surface roughness issues during chemical mechanical polishing (CMP), which complicates the development of effective CMP slurries for planarization and defect reduction.
Innovation Solution
An aqueous slurry comprising hydrogen peroxide as an oxidizing agent, colloidal silica particles with specific structures, a cobalt corrosion inhibitor, and a complexing agent like L-aspartic acid, balanced to oxidize cobalt to Co+3 and control etch rates, reducing defects and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt-containing interconnects are used in semiconductor substrates, then copper seed layer deposition is improved and void formation is avoided, but galvanic corrosion and surface roughness occur during CMP
Solution Approach 1:
The patent introduces a specifically formulated CMP slurry containing hydrogen peroxide oxidizing agent, colloidal silica abrasive particles, complexing agents (such as L-aspartic acid, nitrilotriacetic acid, or nitrilotri(methylphosphonic acid)), and cobalt corrosion inhibitors as intermediaries to mediate between the cobalt-containing interconnect and the polishing process. These additives work together to suppress galvanic corrosion, control the polishing reaction, and prevent surface roughness while maintaining the benefits of cobalt interconnects
Solution Approach 2:
The patent changes the chemical parameters of the CMP slurry by incorporating specific concentrations of hydrogen peroxide (0.1-2 wt%), colloidal silica particles (0.5-3 wt%), complexing agents (0.5-2 wt%), and corrosion inhibitors. These parameter changes transform the slurry's chemical composition to specifically address the galvanic corrosion issue between cobalt and copper while maintaining effective polishing performance
2Manufacturing precision
If cobalt is polished during CMP, then planarity is achieved, but excessive corrosion and surface roughness occur
Solution Approach 1:
The patent converts the harmful corrosion tendency of cobalt during CMP into a beneficial controlled polishing process. By adding hydrogen peroxide as an oxidizing agent along with complexing agents and corrosion inhibitors, the slurry transforms the uncontrolled galvanic corrosion into a controlled chemical-mechanical removal process that achieves planarity while minimizing surface roughness and excessive material removal
Solution Approach 2:
The patent creates a composite CMP slurry system combining multiple functional components: hydrogen peroxide oxidizing agent for controlled oxidation, colloidal silica abrasive particles for mechanical removal, complexing agents for cobalt ion complexation, and corrosion inhibitors for protecting against excessive corrosion. This composite formulation works synergistically to achieve planarity while controlling surface quality
3Productivity
If high removal rate is achieved during cobalt polishing, then productivity increases, but surface roughness and defects increase
Solution Approach 1:
The patent optimizes the concentration parameters of multiple slurry components to achieve a balanced removal rate. By adjusting hydrogen peroxide (0.1-2 wt%), colloidal silica (0.5-3 wt%), complexing agents (0.5-2 wt%), and corrosion inhibitors to specific ranges, the slurry achieves high cobalt removal rates while maintaining surface quality through controlled chemical-mechanical action rather than aggressive mechanical polishing
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 slurry effectively polishes cobalt-containing features with reduced defects and surface roughness, achieving high cobalt removal rates while preventing excessive corrosion, by balancing oxidizer, abrasive, and complexing agent concentrations.
Implementation Method 1
oxidation potential of the slurry is sufficient to oxidize at least a portion of the Co0 to Co+3
Implementation Method 2
complexing agent (γ) selected from at least one of L-aspartic acid, nitrilotriacetic acid, nitrilotri(methylphosphonic acid), ethylenediamine-N,N′-disuccinic acid trisodium salt, and ethylene glycol-bis (2aminoethylether)-N,N,N′,N′-tetraacetic acid
Implementation Method 3
0.5 to 3 wt % colloidal silica particles (β), the colloidal silica particles containing primary particles, the primary particles having an average diameter of 25 to 50 nm linked together in conjoined spherical structures
Data Source
AI summary
The invention is an aqueous slurry useful for chemical mechanical polishing a semiconductor substrate having cobalt or cobalt alloy containing features containing Co0. The slurry includes 0.1 to 2 wt % hydrogen peroxide oxidizing agent (α), 0.5 to 3 wt % colloidal silica particles (β), a cobalt corrosion inhibitor, 0.5 to 2 wt % complexing agent (γ) selected from at least one of L-aspartic acid, nitrilotriacetic acid, nitrilotri(methylphosphonic acid), ethylenediamine-N,N′-disuccinic acid trisodium salt, and ethylene glycol-bis (2aminoethylether)-N,N,N′,N′-tetraacetic acid, and balance water having a pH of 5 to 9. The total concentrations remain within the following formulae as follows: wt % (α)+wt % (β)=1 to 4 wt % for polishing the cobalt or cobalt alloy; wt % (γ)≤2*wt % (α) for limiting static etch of the cobalt or cobalt alloy; and wt % (β)+wt % (γ)≤3*wt % (α) for limiting static etch.