Cerium Hydroxide Polishing Liquid Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor manufacturing, there is a need for a polishing liquid that can achieve excellent selectivity between silicon oxide and silicon nitride to prevent excessive polishing during the formation of shallow trench isolation and other micro-structuring processes, where conventional cerium oxide-based polishing liquids fail to provide sufficient selectivity as wiring dimensions continue to miniaturize.
Innovation Solution
A polishing liquid containing abrasive grains with a hydroxide of a tetravalent metal element, such as cerium hydroxide, and a nitrogen-containing compound with a hydrocarbon group, which promotes selective removal of silicon oxide over silicon nitride through electrostatic interactions and hydrophobic coverage, thereby enhancing polishing selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cerium oxide-based polishing liquid is used to achieve high polishing rate, then the polishing rate for silicon oxide is improved, but the polishing selectivity between silicon oxide and silicon nitride deteriorates
Solution Approach 1:
The patent transforms cerium oxide particles into cerium hydroxide particles through chemical conversion, fundamentally changing the chemical composition and surface properties of the abrasive grains. This parameter change enables selective removal of silicon oxide while preserving silicon nitride, achieving both high polishing rate and excellent selectivity simultaneously
Solution Approach 2:
The polishing liquid combines cerium hydroxide particles with silica particles in a specific ratio (cerium hydroxide: 0.01-5 mass%, silica: 0.1-10 mass%). This composite abrasive system leverages the high reactivity of cerium hydroxide with silicon oxide while using silica as a milder abrasive that contributes to overall polishing performance without compromising selectivity
2Productivity
If the abrasive grain content is increased to improve polishing rate, then the productivity is improved, but the generation of polishing scratches worsens
Solution Approach 1:
The patent changes the chemical nature of abrasive grains from cerium oxide to cerium hydroxide, which has different mechanical and chemical properties. Cerium hydroxide provides effective material removal through chemical reaction while its softer nature compared to cerium oxide reduces mechanical scratching, enabling high polishing rates with minimal scratch generation
Solution Approach 2:
The patent replaces primarily mechanical abrasion (cerium oxide-based) with a chemically-driven polishing mechanism (cerium hydroxide-based). The cerium hydroxide reacts chemically with silicon oxide to form soluble complexes, substituting mechanical force with chemical reaction as the primary removal mechanism, thereby reducing scratch generation while maintaining high polishing rates
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 achieves a polishing rate ratio of silicon oxide to silicon nitride of 10 or more, effectively preventing excessive polishing and ensuring precise control over micro-structuring, with the potential for even higher selectivity up to 5000 or more.
Implementation Method 1
promotes selective removal of silicon oxide over silicon nitride through electrostatic interactions
Implementation Method 2
promotes selective removal of silicon oxide over silicon nitride through electrostatic interactions and hydrophobic coverage
Data Source
AI summary
A polishing liquid containing: abrasive grains containing a hydroxide of a tetravalent metal element; and a nitrogen-containing compound having a hydrocarbon group having 6 or more carbon atoms and bonded to a nitrogen atom, in which the nitrogen-containing compound contains at least one selected from the group consisting of a quaternary ammonium salt, tertiary amine, and a heterocyclic compound having a quaternary nitrogen atom constituting a heterocyclic ring. A polishing method including a step of polishing a surface to be polished by using this polishing liquid.