Nitride-Inhibiting CMP Composition for TiN SiN Selectivity
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Solution Overview
Problem
Current chemical-mechanical polishing (CMP) compositions struggle to selectively remove tungsten layers over titanium nitride (TiN) and silicon nitride (SiN) barrier layers, often leading to undesired removal of the planar barrier layer and inconsistent gate height in semiconductor manufacturing.
Innovation Solution
A CMP composition comprising alumina particles with an anionic polymer coating, a removal rate inhibitor with polyoxyalkylene functional groups and sulfonate or sulfate functional groups, an iron-containing catalyst, and a stabilizer, which selectively abrades TiN faster than SiN, achieving a TiN:SiN removal rate selectivity greater than 15:1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If typical CMP compositions are used for removing metal layers over TiN or SiN barrier layers, then metal layer removal is achieved, but the barrier layer is also undesiredly removed leading to loss of selectivity
Solution Approach 1:
The patent introduces a specific intermediary substance (polymer coating on alumina particles) that acts as a selective mediator between the abrasive and the barrier layer. This polymer intermediary prevents direct contact and damage to the TiN/SiN barrier layers while allowing effective metal layer removal, thus resolving the selectivity issue without sacrificing productivity
Solution Approach 2:
The patent changes the chemical parameters of the CMP composition by using polymer-coated alumina particles with specific surface chemistry. This parameter change enables selective interaction with metal layers while being inert toward nitride barrier layers, achieving both high removal rate and high selectivity simultaneously
2Productivity
If CMP compositions with high metal removal rate are used, then productivity is improved, but the removal rate of TiN and SiN is not sufficiently suppressed leading to barrier layer erosion
Solution Approach 1:
The polymer coating serves as a protective intermediary that selectively shields the barrier layer from abrasive damage. It allows aggressive polishing conditions for high metal removal rate while preventing harmful effects on the nitride barrier layers through selective chemical interaction
Solution Approach 2:
The patent applies local quality by giving different regions/functions to different components: the alumina core provides aggressive metal removal capability, while the polymer coating provides selective protection for nitride layers. This local differentiation of properties enables simultaneous achievement of high productivity and low harmful effects
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 ensures precise control over gate height by selectively removing TiN relative to SiN, minimizing the risk of barrier layer erosion and improving the consistency of tungsten gate formation in semiconductor devices.
Implementation Method 1
alumina particles having a surface that comprise an anionic polymer... to abrade at least a portion of the TiN layer... and at least a portion of the SiN layer
Implementation Method 2
an iron containing catalyst... wherein the TiN layer is selectively removed faster than the SiN layer
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition comprising (a) abrasive particles, b) a removal rate inhibitor selected from (I) a surfactant comprising a polyoxyalkylene functional group and a sulfonate functional group, (II) a surfactant comprising a polyoxyalkylene functional group and a sulfate functional group, (III) a first surfactant comprising a polyoxyalkylene functional group and a second surfactant comprising a sulfonate functional group, and (IV) a first surfactant comprising a polyoxyalkylene functional group and a second surfactant comprising a sulfate functional group, and (c) an aqueous carrier. The invention also provides a method of chemically-mechanically polishing a substrate comprising TiN and SiN with the inventive chemical-mechanical polishing composition.