Cobalt CMP Slurry with Phosphonic Acid Rate Accelerators
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Solution Overview
Problem
Current polishing compositions for cobalt in integrated circuit fabrication do not provide satisfactory removal rates and fail to adequately protect the cobalt surface from static etching and corrosion, particularly when using rate accelerators designed for copper polishing.
Innovation Solution
A chemical-mechanical polishing composition comprising alumina or silica abrasives, phosphonic acid or N-heterocyclic compounds as rate accelerators, and amphoteric surfactants or sulfonates as corrosion inhibitors, along with an oxidizing agent and an aqueous carrier, is used to enhance cobalt removal rates while suppressing static etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copper polishing compositions with rate accelerators are used for cobalt, then cobalt removal rate increases, but static etching and corrosion of cobalt surface worsens
Solution Approach 1:
The patent modifies the chemical composition parameters of the polishing slurry by replacing copper-specific rate accelerators with cobalt-specific rate accelerators (such as phosphonic acids and N-heterocyclic compounds) and adjusting the pH level to alkaline conditions (pH 8-11). This parameter change enables the slurry to achieve high cobalt removal rates while suppressing static etching and corrosion through the action of corrosion inhibitors like amphoteric surfactants and sulfonates.
Solution Approach 2:
The patent introduces corrosion inhibitors as intermediary substances that mediate between the rate accelerator and the cobalt surface. These inhibitors (amphoteric surfactants, sulfonates, phosphonates, carboxylates, fatty acid amino acids, amines, or amides) form protective layers on the cobalt surface, preventing direct chemical attack while allowing the rate accelerator to maintain high removal rates. This intermediary mechanism resolves the contradiction by decoupling the removal rate enhancement from the harmful chemical attack.
2Productivity
If abrasive particles are increased to improve removal rate, then polishing efficiency increases, but surface quality and uniformity worsen
Solution Approach 1:
The patent employs a dual abrasive system with different particle types serving different functions: alumina particles (0.01-1 wt%) provide mechanical cutting for high removal rates, while silica particles (0.01-1 wt%) provide gentle abrasion for surface quality. This local differentiation of abrasive functions allows simultaneous optimization of productivity and surface quality by assigning specific roles to different abrasive components.
Solution Approach 2:
The patent creates a composite abrasive system combining alumina and silica particles with specific size distributions (0.01-1 wt% for alumina, 0.01-1 wt% for silica). This composite approach leverages the high hardness of alumina for efficient material removal while using silica's finer, more uniform abrasion characteristics to maintain surface quality, achieving both high productivity and manufacturing precision through material composition.
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 achieves effective cobalt removal rates while minimizing static etching, providing a planarized surface suitable for advanced circuit integration techniques.
Implementation Method 1
The polishing of the substrate typically is further aided by the chemical activity of the polishing composition and/or the mechanical activity of an abrasive suspended in the polishing composition or incorporated into the polishing pad
Implementation Method 2
contacting the surface of the substrate with a polishing pad saturated with the polishing composition
Implementation Method 3
The chemical-mechanical polishing of cobalt (Co) is becoming increasingly important in advanced circuit integration techniques
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition including (a) an abrasive comprising alumina particles, silica particles, or a combination thereof, (b) a rate accelerator comprising a phosphonic acid, an N-heterocyclic compound, or a combination thereof, (c) a corrosion inhibitor comprising an amphoteric surfactant, a sulfonate, a phosphonate, a carboxylate, a fatty acid amino acid, an amine, an amide, or a combination thereof, (d) an oxidizing agent, and (e) an aqueous carrier. The invention also provides a method of polishing a substrate, especially a substrate comprising a cobalt layer, with the polishing composition.