Polishing Liquid Selectivity Silicon Oxide Nitride
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 widths continue to miniaturize.
Innovation Solution
A polishing liquid containing abrasive grains with a hydroxide of a tetravalent metal element, a monovalent acid component without a carboxy group, and a non-ionic polymer, with a pH of 4.5 or less, which selectively removes silicon oxide relative to silicon nitride by exploiting electrostatic interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional cerium oxide-based polishing liquid is used, then the polishing rate for silicon oxide is high, but the polishing selectivity between silicon oxide and silicon nitride is insufficient
Solution Approach 1:
The patent changes the chemical parameters of the polishing liquid by using cerium hydroxide particles instead of cerium oxide particles, and by adjusting the pH to 8.5 or higher. This parameter change transforms the chemical reactivity profile, enabling selective removal of silicon oxide while preserving silicon nitride, thus resolving the contradiction between polishing rate and selectivity
Solution Approach 2:
The patent employs a composite approach by combining cerium hydroxide particles with specific additives including carboxylic acids, polyacrylic acid, and polyvinyl alcohol. This composite formulation creates a synergistic effect that enhances both the polishing rate for silicon oxide and the selectivity against silicon nitride, addressing the technical contradiction
2Productivity
If the wiring width is miniaturized, then the integration density increases, but the polishing scratches become problematic
Solution Approach 1:
By adjusting the pH to 8.5 or higher and using cerium hydroxide particles with controlled size distribution (0.1-10 μm), the patent modifies the polishing mechanism to reduce mechanical scratching. The alkaline environment promotes chemical softening of silicon oxide, allowing smoother removal that is compatible with miniaturized wiring structures
Solution Approach 2:
The patent replaces purely mechanical abrasion with a chemically-assisted mechanical process. The alkaline polishing liquid chemically softens the silicon oxide surface before mechanical removal, reducing the formation of scratches and enabling surface quality suitable for further miniaturization
3Productivity
If the polishing rate for silicon oxide is increased, then the processing efficiency improves, but the excessive polishing of stopper material occurs
Solution Approach 1:
The patent achieves differential polishing rates by changing the chemical environment to pH 8.5 or higher, which creates a strong alkaline condition that selectively accelerates silicon oxide removal while having minimal effect on silicon nitride. This chemical parameter change enables high processing efficiency without excessive polishing of stopper material
Solution Approach 2:
The patent creates local chemical quality differences by using pH-sensitive chemistry that responds differently to silicon oxide versus silicon nitride surfaces. The alkaline environment locally activates chemical reactions at silicon oxide interfaces while leaving silicon nitride relatively unaffected, achieving selective removal with high processing efficiency
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
This solution enables a polishing rate ratio of silicon oxide to silicon nitride of 30 or more, providing effective selectivity and minimizing scratches on the polished surface, thus supporting further miniaturization in semiconductor manufacturing.
Implementation Method 1
selectively removes silicon oxide relative to silicon nitride by exploiting electrostatic interactions
Data Source
AI summary
A polishing liquid containing: abrasive grains containing a hydroxide of a tetravalent metal element; a monovalent acid component having no carboxy group; and a non-ionic polymer, in which a pH is 4.5 or less. A polishing method including a step of polishing a surface to be polished by using this polishing liquid.