CMP Slurry Selectivity for TiN Barrier Protection
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) compositions are not selective enough to reliably stop the removal of titanium nitride (TiN) and titanium/titanium nitride (Ti/TiN) barrier layers during the polishing of semiconductor substrates, leading to undesired removal of the planar portion of the barrier layer and potential issues in gate structure formation.
Innovation Solution
A CMP method using an acidic composition with a particulate abrasive and a surfactant, such as an anionic or nonionic surfactant, that suppresses the removal of TiN and Ti/TiN while allowing for effective removal of metal, dielectric, or polymer layers, thereby enhancing selectivity and preventing unwanted barrier layer removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If typical CMP compositions are used for metal removal, then metal layers can be removed, but TiN or Ti/TiN barrier layers are also undesirably removed
Solution Approach 1:
The patent modifies the chemical composition parameters of the CMP slurry by incorporating specific organic acids (e.g., acetic acid, formic acid) and chelating agents (e.g., EDTA, DTPA) to alter the chemical reactivity profile. This enables selective suppression of TiN removal while preserving metal removal capability, resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent introduces chelating agents as intermediary substances that selectively bind to titanium ions, preventing them from participating in removal reactions. This intermediary mechanism allows the CMP process to remove metals effectively while protecting the TiN barrier layer, simultaneously achieving high metal removal rates and precise barrier layer thickness control
2Reliability
If CMP composition is made more selective for metal removal, then barrier layer removal is suppressed, but removal rate of metals and dielectrics may be reduced
Solution Approach 1:
The patent optimizes the concentration ratios and chemical properties of multiple components including organic acids, chelating agents, and abrasives to achieve enhanced selectivity. By carefully tuning these parameters, the composition maintains high removal rates for metals and dielectrics while reliably suppressing TiN removal, thus improving both reliability and productivity
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 excellent selectivity for metal removal relative to TiN and Ti/TiN, ensuring accurate stop-on-barrier polishing and maintaining acceptable removal rates for metals and dielectrics, thus preventing lower gate heights and other structural problems.
Implementation Method 1
The CMP composition comprises a particulate abrasive suspended in a liquid carrier containing a surfactant... The surfactant surprisingly aids in suppression of TiN and Ti/TiN removal
Implementation Method 2
The method comprises abrading away the metals... or dielectrics... or polymers... with an acidic CMP composition... The CMP composition comprises a particulate abrasive
Data Source
AI summary
A chemical mechanical polishing (CMP) method for removal of a metal layer deposited over a titanium nitride (TiN) or titanium/titanium nitride (Ti/TiN) barrier layer is described herein. The method comprises abrading the metal layer with an acidic CMP composition to expose the underlying TiN or Ti/TiN layer, wherein the TiN or Ti/N layer is polished at a low rate due to the presence of a surfactant inhibitor. The acidic CMP composition comprises a particulate abrasive (e.g., silica, alumina) suspended in a liquid carrier containing a surfactant selected from the group consisting of an anionic surfactant, a nonionic surfactant, cation surfactants, and a combination thereof.