CMP Slurry Additive for Nitride Erosion and Dishing Control
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Solution Overview
Problem
In semiconductor manufacturing, the CMP process faces challenges in reducing the loss of silicon nitride films used as polishing stoppers and oxide films in trench portions, leading to increased erosion and dishing due to low selectivity between silicon oxide and nitride films, especially with miniaturization.
Innovation Solution
A polishing additive composition comprising an anionic polymer with a polymer distribution index (PDI) of 3.5 to 5.5, a cationic compound, a nonionic surfactant, a dishing inhibitor, and an amphoteric ionic compound, combined with cerium oxide particles and an anionic dispersant, is used to enhance the selectivity and reduce loss of both silicon nitride and oxide films during the CMP process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the passivation performance of silicon oxide film is improved to reduce polishing rate, then dishing is reduced, but the selectivity of silicon oxide film to silicon nitride film decreases to 20:1 causing increased erosion of nitride film
Solution Approach 1:
The invention changes the chemical composition parameters of the polishing slurry by introducing a specific organic acid component with controlled concentration (0.1-5.0 wt%). This parameter change modifies the chemical reactivity between the slurry and both oxide and nitride films, achieving a new balance where oxide film polishing rate is sufficiently reduced for dishing control while nitride film erosion is simultaneously minimized through selective chemical interaction
Solution Approach 2:
The invention creates a composite polishing slurry system combining inorganic polishing particles (cerium oxide, silicon oxide) with organic additives (specific organic acid, surfactants, polymers). This composite formulation works synergistically: the inorganic particles provide mechanical polishing action while the organic acid component provides chemical passivation control, achieving both dishing reduction and nitride film protection through the combined effect of multiple material components
2Loss of substance
If conventional slurry is used to maintain high oxide film/nitride film selectivity, then nitride film erosion is reduced, but dishing increases due to excessive oxide film loss in trench portions
Solution Approach 1:
The invention modifies the chemical parameters of the polishing slurry by adding specific organic acid components at controlled concentrations (0.1-5.0 wt%). This changes the chemical reaction kinetics between the slurry and the oxide film, reducing the oxide film polishing rate to an optimal range that prevents excessive loss in trench portions while maintaining adequate removal rate for planarization, thereby controlling dishing without compromising nitride film protection
3Productivity
If pattern density of silicon nitride films decreases due to miniaturization, then device integration is improved, but erosion of nitride film used as polishing stopper increases leading to increased dishing
Solution Approach 1:
The invention changes the chemical composition parameters of the polishing slurry by introducing specific organic acid components with optimized concentrations. This parameter modification reduces the chemical reactivity toward nitride film, thereby minimizing erosion even when pattern density is low due to miniaturization, allowing continued device integration improvement without sacrificing stopper film integrity
Solution Approach 2:
The organic acid component acts as a chemical intermediary that selectively interacts with the nitride film surface during polishing. This intermediary forms a protective complex or modifies the surface chemistry at the nitride film-slush interface, reducing direct abrasive attack and chemical etching on the nitride film, thereby protecting the polishing stopper function even as device features are miniaturized and pattern density decreases
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 inhibits erosion and dishing by improving the passivation of silicon nitride films and maintaining high oxide film/nitride film selectivity, resulting in reduced polishing loss and improved flatness in semiconductor processing.
Implementation Method 1
an anionic polymer having a polymer distribution index (PDI) of 3.5 to 5.5
Implementation Method 2
polishing of the wafer surface is performed by mechanical friction caused by polishing particles in the slurry
Implementation Method 3
chemical removal is simultaneously achieved through chemical reaction between the chemical components in the slurry and the wafer surface
Implementation Method 4
a cationic compound, a nonionic surfactant, a dishing inhibitor, and an amphoteric ionic compound
Data Source
AI summary
The present invention relates to a method for polishing an insulating film of a semiconductor element, the method comprising polishing an insulating film, which is formed by embedding conductive patterns formed on a substrate, with a polishing slurry composition comprising a polishing agent including cerium oxide particles and an anionic dispersant, and a polishing additive composition comprising an anionic polymer, a cationic compound, a nonionic surfactant, a dishing inhibitor, and an amphoteric ionic compound, wherein the anionic polymer has a polymer distribution index (PDI) of 3.5 to 5.5, to remove a step associated with the insulating film.