Tungsten CMP Slurry with Positively Charged Silica
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Solution Overview
Problem
Conventional tungsten chemical mechanical polishing (CMP) slurries using hydrogen peroxide as an oxidizer often result in excessive tungsten etching, compromising planarity and device integrity in semiconductor manufacturing, as semiconductor feature sizes shrink, making it necessary to develop less corrosive CMP slurries that reduce tungsten etching rates.
Innovation Solution
A CMP composition comprising a water-based liquid carrier with colloidal silica abrasive having a permanent positive charge, an amine compound, an iron-containing accelerator, and a hydrogen peroxide oxidizer, along with a stabilizer, which reduces tungsten etching rates while maintaining effective polishing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrogen peroxide oxidizer is used in conventional tungsten CMP slurries, then polishing effectiveness is improved, but tungsten etching rate increases excessively
Solution Approach 1:
The patent changes the chemical parameters of the slurry by replacing hydrogen peroxide with potassium permanganate as the oxidizer, and using specific chelating agents (EDTA, DTPA, HEDPA) to control the chemical environment. This parameter change reduces tungsten etching while maintaining polishing effectiveness through the synergistic action of the new oxidizer-chelating agent system.
Solution Approach 2:
The patent introduces chelating agents as intermediary substances that mediate between the oxidizer and tungsten. These chelating agents form complexes with metal ions, controlling the oxidation process and reducing direct corrosive attack on tungsten, thereby reducing etching while maintaining polishing action.
2Manufacturing precision
If conventional CMP operations are performed to remove excess tungsten, then planarity is improved, but array erosion and plug recessing occur
Solution Approach 1:
The patent modifies the chemical composition parameters by using potassium permanganate instead of hydrogen peroxide and incorporating specific chelating agents. This changes the chemical interaction mechanism with tungsten and dielectric materials, reducing array erosion and plug recessing while maintaining the planarization function.
Solution Approach 2:
The patent creates different chemical environments for different materials being polished. The slurry composition is optimized to selectively interact with tungsten versus dielectric materials, providing different removal characteristics for different materials to prevent array erosion and plug recessing while achieving planarity.
3Reliability
If tungsten etching rate is reduced to improve device integrity, then device integrity is improved, but polishing rate may decrease
Solution Approach 1:
The patent changes multiple parameters simultaneously - oxidizer type, chelating agent concentration, and pH control - to achieve an optimal balance where tungsten etching is reduced for improved device integrity while the polishing rate is maintained through the synergistic chemical-mechanical action of the modified slurry system.
Solution Approach 2:
The patent creates a composite chemical system combining potassium permanganate oxidizer with specific chelating agents (EDTA, DTPA, HEDPA). This composite system provides dual functionality: reducing tungsten etching through controlled chemistry while maintaining effective polishing through the combined mechanical and chemical action of the composite slurry formulation.
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 reduces tungsten etching rates while ensuring high tungsten removal rates, thereby improving planarity and device integrity in semiconductor manufacturing by using colloidal silica with a permanent positive charge and specific amine and iron-containing components.
Implementation Method 1
The relative motion of the substrate and pad abrades and removes a portion of the material from the surface of the substrate, thereby polishing the substrate
Implementation Method 2
an iron containing accelerator
Implementation Method 3
a hydrogen peroxide oxidizer
Data Source
AI summary
A chemical mechanical polishing composition for polishing a substrate having a tungsten layer includes a water based liquid carrier, a colloidal silica abrasive dispersed in the liquid carrier and having a permanent positive charge of at least 6 mV, an amine containing polymer in solution in the liquid carrier, and an iron containing accelerator. A method for chemical mechanical polishing a substrate including a tungsten layer includes contacting the substrate with the above described polishing composition, moving the polishing composition relative to the substrate, and abrading the substrate to remove a portion of the tungsten from the substrate and thereby polish the substrate.