CMP Slurry for Cobalt Planarization with Aspartic Acid Selectivity
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving high cobalt removal rates while maintaining low TiN removal rates during chemical mechanical polishing, which is crucial for planarization and preventing electro-migration in advanced technical nodes, especially at dimensions smaller than 10 nm.
Innovation Solution
A chemical mechanical polishing method using a composition comprising water, an oxidizing agent, aspartic acid or its salts, colloidal silica abrasive with a particle diameter of 25 nm or less, and optional corrosion inhibitors, surfactants, and biocides, applied to a substrate with a polyurethane polishing pad to achieve high cobalt removal rates and selective removal of TiN.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP slurry is used to achieve high cobalt removal rates, then cobalt removal rate increases, but TiN barrier layer removal rate also increases excessively
Solution Approach 1:
The patent changes the chemical composition parameters of the CMP slurry by incorporating specific organic acids (aspartic acid, citric acid, or oxalic acid) at controlled concentrations (0.1-5.0 wt%, 0.01-1.0 wt%, or 0.01-0.1 wt% respectively). These parameter changes modify the chemical reactivity of the slurry to achieve selective removal of cobalt while suppressing TiN removal, resolving the contradiction between high cobalt removal rate and controlled TiN removal rate.
Solution Approach 2:
The patent uses a composite slurry formulation combining colloidal silica abrasive particles (5-50 nm) with specific organic acid molecules. This composite material approach creates a synergistic effect where the silica provides mechanical abrasion for cobalt removal while the organic acids provide chemical selectivity, enabling high cobalt removal rates with suppressed TiN removal through the combined action of different material components.
2Productivity
If cobalt removal rate is increased for efficient planarization, then processing efficiency improves, but selectivity between cobalt and TiN deteriorates
Solution Approach 1:
The patent adjusts chemical parameters by introducing organic acids with specific molecular structures and functional groups that have selective affinity for cobalt oxides. By changing the pH, oxidation potential, and chemical composition parameters of the slurry, the process achieves high processing efficiency while maintaining reliable selectivity between cobalt and TiN removal through controlled chemical reactions.
Solution Approach 2:
The organic acids in the slurry act as intermediary substances that facilitate selective chemical reactions. These intermediary molecules mediate between the abrasive particles and the cobalt/TiN surfaces, enabling preferential attack on cobalt while protecting TiN through selective complexation or passivation, thus resolving the contradiction between efficiency and selectivity.
3Speed
If aggressive polishing is applied to remove cobalt quickly, then planarization speed increases, but barrier layer integrity deteriorates
Solution Approach 1:
The patent modifies the chemical parameters of the polishing environment by adding organic acids that change the reaction kinetics and selectivity. This allows aggressive mechanical action (high planarization speed) to be combined with controlled chemical action that protects the barrier layer, resolving the contradiction between speed and integrity through parameter optimization.
Solution Approach 2:
The organic acids in the slurry provide preliminary protective action on the TiN barrier layer by forming protective complexes or passivation layers before the abrasive particles can cause excessive removal. This preliminary anti-action prevents damage to the barrier layer while allowing fast cobalt removal, resolving the contradiction between planarization speed and barrier layer integrity.
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 method achieves cobalt removal rates of ≥1500 Å/min with enhanced cobalt:TiN removal rate selectivity, ensuring effective planarization and preventing excessive barrier layer removal, thus maintaining device functionality.
Implementation Method 1
providing a polishing composition, containing, as initial components: water; an oxidizing agent
Implementation Method 2
a colloidal silica abrasive having an average particle diameter of less than or equal to 25 nm
Data Source
AI summary
A process for chemical mechanical polishing a substrate containing cobalt and TiN to planarize the surface and at least improve surface topography of the substrate. The process includes providing a substrate containing cobalt and TiN; providing a polishing composition, containing, as initial components: water; an oxidizing agent; aspartic acid or salts thereof; and, colloidal silica abrasives with diameters of ≤25 nm; and, providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the polishing pad and the substrate; and dispensing the polishing composition onto the polishing surface at or near the interface between the polishing pad and the substrate; wherein some of the cobalt is polished away to planarize the substrate to provide improved cobalt:TiN removal rate selectivity.