Polymer-Coated CMP Abrasives for Low-Erosion Tungsten Buffing
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Solution Overview
Problem
Conventional chemical mechanical polishing methods for tungsten buffing applications face challenges in achieving good surface topography and planarity while minimizing erosion, particularly in tungsten plugs and interconnects, due to excessive metal removal within substrate features.
Innovation Solution
A chemical-mechanical polishing composition comprising abrasives such as ceria, titania, or zirconia surface-coated with a copolymer of sulfonic acid and carboxylic acid monomeric units, combined with hydrogen peroxide and ferric nitrate as an oxidizing agent, and water at a pH of 2 to 5, which balances material removal rates to optimize surface topography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional abrasive particles are used for tungsten buffing, then the buffing process can proceed, but the abrasive particles generate excessive heat and fail to produce a satisfactory mirror-like finish
Solution Approach 1:
The patent applies parameter changes by modifying the surface properties of abrasive particles through corona discharge treatment. This treatment alters the surface energy and chemical composition of the abrasive particles, enabling them to effectively buff tungsten at lower temperatures while achieving mirror-like finishes. The corona treatment introduces oxygen-containing functional groups on the abrasive surface, which changes the interaction mechanism between abrasive and workpiece, reducing heat generation while improving material removal efficiency.
2Reliability
If conventional abrasives are used, then the process is simple, but the abrasive particles are inconsistent in performance and generate heat
Solution Approach 1:
The corona discharge treatment uniformly modifies the surface parameters of all abrasive particles in the batch, creating consistent surface energy and chemical composition. This uniform treatment ensures that all particles perform reliably and consistently, eliminating the variability inherent in conventional abrasives. The controlled application of corona treatment allows precise adjustment of surface properties to optimize both performance consistency and temperature control.
3Productivity
If traditional buffing methods are used, then the process can continue, but productivity is reduced due to heat generation and inconsistent results
Solution Approach 1:
The patent applies preliminary action by pre-treating the abrasive particles with corona discharge before the actual buffing process. This pre-treatment prepares the abrasive surfaces to optimize their interaction with tungsten, ensuring that the subsequent buffing operation proceeds efficiently with minimal heat generation and consistent mirror-like finish results. The preliminary surface modification enables the abrasives to cut more effectively at lower speeds and temperatures, thereby increasing overall 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 solution effectively minimizes erosion and achieves improved surface planarity by balancing the removal rates of tungsten and other materials, such as silicon oxide and silicon nitride, during the buff polishing step, resulting in enhanced substrate topography.
Implementation Method 1
The abrasive particles are corona treated to modify their surface properties for improved performance in buffing tungsten to a mirror-like finish
Data Source
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AI summary
The invention provides a chemical mechanical polishing composition comprising (a) an abrasive selected from the group consisting of alumina, ceria, titania, zirconia, and combinations thereof, wherein the abrasive is surface coated with a copolymer comprising a combination of sulfonic acid monomeric units and carboxylic acid monomeric units a combination of sulfonic acid monomeric units and phosphonic acid monomeric units, (b) an oxidizing agent, and (c) water, wherein the polishing composition has a pH of about 2 to about 5. The invention further provides a method of chemically-mechanically polishing a substrate with the inventive chemical mechanical polishing composition. Typically, the substrate comprises tungsten or cobalt and silicon oxide.