Coated Titania CMP Slurry for Molybdenum and Ruthenium Polishing
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) methods for transition metals like molybdenum and ruthenium suffer from low removal rates, high corrosion, and safety concerns due to toxic by-products, particularly in the polishing of ruthenium surfaces.
Innovation Solution
A CMP composition comprising titania abrasive particles coated with alumina or amorphous silica, along with a corrosion inhibitor, is used to polish transition metal surfaces, which includes a liquid carrier and optional oxidizing agents, to enhance removal rates and reduce corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silica abrasive compositions are used for molybdenum polishing, then the polishing process can be performed, but the removal rate is low
Solution Approach 1:
The patent changes the abrasive material parameter from conventional silica to titania (titanium dioxide) particles, which fundamentally alters the mechanical properties and cutting ability of the polishing slurry. This parameter change enables significantly higher removal rates for molybdenum while maintaining surface quality, directly resolving the contradiction between productivity and reliability in molybdenum polishing.
Solution Approach 2:
The patent employs composite material formulation by combining titania abrasive particles with specific corrosion inhibitors and oxidizing agents in a slurry system. This composite approach allows the titania to provide high removal rate while the corrosion inhibitor protects the molybdenum from excessive corrosion, and the oxidizing agent facilitates chemical mechanical polishing action, thereby simultaneously achieving high productivity and reliability.
2Productivity
If oxidizers such as hydrogen peroxide are used for molybdenum polishing, then removal rate improves, but corrosion rates become high
Solution Approach 1:
The patent introduces a corrosion inhibitor as an intermediary substance that mediates between the oxidizing agent and the molybdenum substrate. The corrosion inhibitor selectively adsorbs onto the molybdenum surface, forming a protective layer that prevents excessive corrosion while allowing the oxidizing agent to maintain its effectiveness in facilitating material removal, thus resolving the contradiction between improved removal rate and reduced corrosion.
Solution Approach 2:
The patent converts the potentially harmful corrosive action of oxidizers into a beneficial process by controlling the oxidation to produce a thin, uniform oxide layer that facilitates mechanical removal while the corrosion inhibitor prevents uncontrolled corrosion. This transforms the harmful corrosive effect into a controlled chemical mechanical polishing mechanism that improves removal rate without excessive corrosion damage.
3Productivity
If conventional silica and iodate chemistry are used for ruthenium polishing, then polishing can be performed, but removal rates are low and etching rates are high
Solution Approach 1:
The patent changes the chemical composition parameters of the polishing slurry by replacing conventional silica-iodate chemistry with a titania-based slurry system specifically optimized for ruthenium. This parameter change in abrasive material and chemical composition enables significantly higher removal rates for ruthenium while reducing etching rates and improving surface quality, directly addressing the limitations of conventional polishing chemistry for this material.
4Ease of operation
If neutral to alkaline pH conditions are used for ruthenium polishing, then polishing can proceed, but severe pad staining occurs
Solution Approach 1:
The patent changes the pH parameter of the polishing slurry from neutral to alkaline conditions to acidic conditions (pH 2-5). This parameter change prevents the formation of insoluble ruthenium oxidation by-products that cause pad staining, while still enabling effective polishing through the titania abrasive and controlled chemical action. The acidic environment keeps ruthenium oxidation products soluble, eliminating the staining problem while maintaining ease of operation.
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 achieves significantly improved removal rates, up to 200% higher than conventional methods, with reduced corrosion and minimal surface damage, and provides selectivity for molybdenum and ruthenium films.
Implementation Method 1
Chemical Mechanical Polishing or Planarization (CMP) is a process in which material is removed from a surface of a microelectronic device wafer, and the surface is planarized and polished by coupling a physical process such as abrasion
Implementation Method 2
titania abrasive particles, wherein the particles are at least partially coated with alumina or amorphous silica to provide coated titania abrasive particles
Implementation Method 3
a corrosion inhibitor
Implementation Method 4
oxidizing agents
Data Source
AI summary
The invention provides compositions useful in the polishing of transition metal-containing surfaces typically found on microelectronic devices. In one aspect, the invention provides a composition comprising: a liquid carrier; titania abrasive particles, wherein the particles are at least partially coated with alumina or amorphous silica to provide coated titania abrasive particles; wherein the coated titania abrasive particles have an average diameter of about 50 nm to about 250 nm; and a corrosion inhibitor. The invention, the compositions are advantageously utilized to polish microelectronic device substrates having transition metal-containing surfaces thereon. In certain embodiments, the surfaces are chosen from molybdenum and ruthenium-containing films and show markedly improved selectivity relative to thermal oxide.