CMP Slurry Composition for Cobalt Corrosion and Selectivity Control
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) slurries are inadequate for polishing cobalt-containing surfaces due to cobalt's susceptibility to corrosion, leading to unacceptable defects and selectivity issues in semiconductor manufacturing, particularly as chip features shrink and require thinner, more conformal interconnects.
Innovation Solution
A polishing composition comprising an abrasive, pH adjuster, barrier film removal rate enhancer, TEOS removal rate inhibitor, cobalt removal rate enhancer, azole-containing corrosion inhibitor, and cobalt corrosion inhibitor, which is designed to maintain a non-selective polishing rate for cobalt and dielectric materials, minimizing corrosion and achieving a 1:1 dielectric/cobalt polishing selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copper and tungsten CMP slurries are used on cobalt layers, then polishing of traditional interconnect materials is achieved, but cobalt corrosion and unacceptable defects occur
Solution Approach 1:
The patent modifies the chemical composition parameters of the CMP slurry by incorporating specific corrosion inhibitors (benzotriazole and tolyltriazole) and adjusting pH levels to create a formulation that maintains polishing effectiveness while preventing cobalt corrosion. This parameter adjustment resolves the contradiction between polishing productivity and cobalt layer reliability.
Solution Approach 2:
The patent introduces corrosion inhibitor molecules as intermediary substances that mediate between the abrasive particles and the cobalt layer. These inhibitors form protective complexes with cobalt ions, preventing direct corrosive interaction while allowing the mechanical polishing action to proceed, thus maintaining both productivity and reliability.
2Productivity
If traditional CMP slurries are used, then copper and tungsten removal is effective, but barrier film selectivity and wafer topography defects occur
Solution Approach 1:
The patent adjusts multiple slurry parameters including pH level, abrasive particle size distribution, and chemical composition to optimize the polishing mechanism. These parameter changes enable controlled material removal that maintains both high productivity and precise wafer topography by reducing non-uniform polishing and defect formation.
3Manufacturing precision
If thinner Cu and Ta/TaN barrier films are used, then interconnect resistivity is maintained in BEOL, but polishing selectivity and flexibility in deposition are compromised
Solution Approach 1:
The patent develops a multi-parameter slurry formulation that can be adjusted to match different film thicknesses and material compositions. By optimizing abrasive size, chemical composition, and pH parameters, the slurry achieves appropriate selectivity for polishing thinner barrier films while maintaining deposition process flexibility and interconnect resistivity control.
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 effectively polishes cobalt and dielectric materials at moderate removal rates without significant cobalt corrosion, achieving desired surface topography and selectivity, thereby addressing the challenges of cobalt corrosion and selectivity in advanced semiconductor nodes.
Implementation Method 1
chemical mechanical polishing (CMP)
Implementation Method 2
azole-containing corrosion inhibitor and a cobalt corrosion inhibitor
Data Source
AI summary
A polishing composition includes an abrasive; an optional pH adjuster; a barrier film removal rate enhancer; a TEOS removal rate inhibitor; a cobalt removal rate enhancer; an azole-containing corrosion inhibitor; and a cobalt corrosion inhibitor.