Cobalt Polishing Accelerators for CMP Dishing Control
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Solution Overview
Problem
Current chemical-mechanical polishing methods for cobalt in integrated circuits face challenges with low removal rates, high dishing and erosion, and high defectivity, particularly due to the formation of passivating oxide-hydroxide coatings at certain pH levels.
Innovation Solution
A chemical-mechanical polishing composition comprising abrasive particles, a cobalt accelerator, a cobalt corrosion inhibitor, an oxidizing agent, and water, with a pH range of 3 to 8.5, which includes specific compounds like iminodiacetic acid and hydrogen peroxide to enhance cobalt removal rates while minimizing dishing and erosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high particle loading and high downforce pressure are used to achieve cobalt removal at pH 9.0 and above, then cobalt removal rate is improved, but dishing and erosion increase and defectivity increases
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by introducing specific accelerators (aminopolycarboxylic acids and their salts) and controlling pH levels to achieve effective cobalt removal at lower particle loading and downforce pressure, thereby resolving the contradiction between removal rate and surface quality
Solution Approach 2:
The patent creates a composite chemical system combining multiple components including accelerators, chelating agents, and abrasive particles that work synergistically to enhance cobalt removal efficiency while maintaining surface integrity, allowing effective polishing without excessive mechanical force
2Productivity
If high particle loading and high downforce pressure are used to achieve cobalt removal at pH 9.0 and above, then cobalt removal rate is improved, but defectivity increases
Solution Approach 1:
The patent modifies chemical parameters by using accelerator compounds that enable effective cobalt removal at reduced mechanical pressure, thereby minimizing defect generation while maintaining high removal rates
Solution Approach 2:
The patent introduces accelerator compounds as intermediaries that facilitate the chemical reaction between the polishing composition and cobalt surface, enabling removal without relying on high mechanical force that would cause defects
3Stability of the object's composition
If conventional polishing compositions are used at pH 9.5 and above, then an insoluble passivating oxide-hydroxide coating forms on cobalt, but cobalt removal rate decreases
Solution Approach 1:
The patent converts the harmful passivating effect into a beneficial controlled reaction by using accelerators that promote selective cobalt removal through the passivating layer rather than being blocked by it, achieving both surface protection and effective removal
Solution Approach 2:
The patent changes the chemical environment by introducing accelerators and controlling pH and ionic strength parameters to prevent excessive passivation while maintaining stable cobalt surface chemistry for controlled removal
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 significantly higher cobalt removal rates, reduced dishing and erosion, and lower defectivity, as demonstrated by comparative examples, with the cobalt accelerator and corrosion inhibitor working in concert to manage the cobalt surface chemistry effectively.
Implementation Method 1
a cobalt accelerator selected from a compound having the formula: NR1R2-CH2-CO-M where M is a divalent metal or a group 13 or 14 element
Implementation Method 2
an oxidizing agent
Implementation Method 3
abrasive particles
Data Source
AI summary
The invention provides a chemical mechanical polishing composition comprising (a) abrasive particles, (b) a cobalt accelerator selected from a compound having the formula: NR1R2R3 wherein R1, R2, and R3 are independently selected from hydrogen, carboxyalkyl, substituted carboxyalkyl, hydroxyalkyl, substituted hydroxyalkyl and aminocarbonylalkyl, wherein none or one of R1, R 2 , and R3 are hydrogen; dicarboxyheterocycles; heterocyclylalkyl-α- amino acids; N (amidoalkyl)amino acids; unsubstituted heterocycles; alkyl substituted heterocycles; substituted-alkyl substituted heterocycles; N aminoalkyl -α- amino acids; and combinations thereof, (c) a cobalt corrosion inhibitor, (d) an oxidizing agent that oxidizes a metal, 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.