Cobalt Dishing Control Agents in CMP Slurries
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Solution Overview
Problem
Current chemical-mechanical polishing methods for cobalt in integrated circuit fabrication face challenges with high removal rates, dishing, erosion, and defectivity, particularly due to the formation of passivating oxide-hydroxide coatings and soluble hydrated Co(II) species at different pH levels, requiring aggressive formulations and high particle loading.
Innovation Solution
A chemical-mechanical polishing composition comprising abrasive particles, a cobalt corrosion inhibitor with an anionic head group and C 13 -C 20 aliphatic tail group, an oxidizing agent, and water, applied at a pH of 3 to 8.5, which includes a cobalt dishing control agent to manage cobalt removal and prevent excessive erosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If aggressive formulations with high particle loading are used to achieve high cobalt removal rates, then cobalt removal rate is improved, but dishing and erosion increase
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by incorporating specific additives (corrosion inhibitors, dishing control agents, oxidizing agents) that modify the chemical interaction between the slurry and cobalt. This allows achieving high removal rates through enhanced chemical activity rather than mechanical aggression, thus avoiding excessive dishing and erosion that would result from high particle loading.
Solution Approach 2:
The patent creates a composite polishing composition that combines multiple functional components: abrasive particles for mechanical removal, corrosion inhibitors to prevent unwanted chemical reactions, dishing control agents to regulate material removal uniformity, and oxidizing agents to facilitate cobalt removal. This composite formulation achieves high productivity while maintaining manufacturing precision through synergistic interactions among components.
2Productivity
If high downforce pressure is applied to increase cobalt removal rate, then productivity is improved, but device complexity and processing cost increase
Solution Approach 1:
The patent modifies the chemical composition parameters of the polishing slurry to include corrosion inhibitors, dishing control agents, and oxidizing agents. These chemical modifications enable high cobalt removal rates at lower downforce pressures, simplifying the mechanical requirements of the polishing system and reducing processing complexity compared to mechanical-force-dependent approaches.
3Reliability
If pH is increased to 9.5 and above to form passivating oxide-hydroxide coating, then corrosion resistance is improved, but cobalt removal rate decreases
Solution Approach 1:
The patent optimizes the pH parameter within the 3-8.5 range and introduces oxidizing agents that enable effective cobalt removal at these moderate pH levels. The oxidizing agents facilitate cobalt oxidation and removal without requiring the high pH conditions that would form protective but removal-inhibiting oxide-hydroxide passivation layers, thus maintaining both productivity and controlled corrosion resistance.
Solution Approach 2:
The patent incorporates oxidizing agents that accelerate cobalt oxidation and removal processes. These strong oxidants enable efficient cobalt removal at pH levels below 9.5, preventing the formation of insoluble passivating oxide-hydroxide coatings while maintaining high removal rates, thus resolving the contradiction between corrosion resistance and productivity.
4Productivity
If pH is decreased below 9.5 to prevent passivating coating formation, then cobalt removal rate is improved, but erosion of dielectric materials increases
Solution Approach 1:
The patent introduces corrosion inhibitors and dishing control agents as intermediary substances that mediate between the polishing composition and the substrate materials. These intermediaries selectively protect dielectric materials from erosion while allowing cobalt removal to proceed at lower pH levels, thus enabling high productivity without the harmful erosion that would otherwise occur at acidic pH conditions.
Solution Approach 2:
The oxidizing agents in the patent enable cobalt removal through oxidative mechanisms that are selective to cobalt. This allows achieving high removal rates at lower pH levels without the non-selective chemical attack on dielectric materials that would otherwise occur, thus resolving the contradiction between productivity and minimizing harmful erosion.
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 achieves high cobalt removal rates with reduced dishing and erosion, while maintaining low defectivity, by effectively controlling cobalt removal and protecting the substrate surface through the use of anionic surfactants and oxidizing agents, thereby improving the planarization efficiency.
Implementation Method 1
an oxidizing agent that oxidizes cobalt
Implementation Method 2
a cobalt dishing control agent, wherein the cobalt dishing control agent comprises an anionic head group and a C 13 -C 20 aliphatic tail group
Data Source
AI summary
The invention provides a chemical mechanical polishing composition comprising (a) abrasive particles, (b) a cobalt corrosion inhibitor, (c) a cobalt dishing control agent, wherein the cobalt dishing control agent comprises an anionic head group and a C13 C20 aliphatic tail group, (d) an oxidizing agent that oxidizes cobalt, and (e) water, wherein the polishing composition has a pH of about 3 to about 8.5. The invention further provides a method of chemically-mechanically polishing a substrate with the inventive chemical mechanical polishing composition. Typically, the substrate contains cobalt.