Silicon Nitride Polishing Composition Selective Convex Removal
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Solution Overview
Problem
Current polishing compositions fail to effectively remove irregularities from silicon nitride films during semiconductor manufacturing, leading to insufficient flatness and differences in height due to non-selective polishing of convex and concave parts.
Innovation Solution
An acidic polishing composition containing an anionic copolymer with specific unit structures and abrasive grains, which selectively scrapes off the convex parts of silicon nitride films at a pH less than 6, enhancing the polishing rate of convex parts relative to concave parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing compositions are used on silicon nitride films, then polishing can be performed, but irregularities cannot be sufficiently removed and differences in height remain
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by introducing an anionic copolymer with specific acidic groups that activate at pH less than 6. This creates a pH-dependent chemical reaction that selectively attacks convex parts of silicon nitride, transforming the polishing mechanism from non-selective mechanical removal to selective chemical-mechanical removal, thereby achieving both high flatness and adequate polishing rate
Solution Approach 2:
The invention uses a composite polishing composition containing abrasive grains combined with a specifically designed anionic copolymer. This composite formulation integrates mechanical abrasion with chemical etching, where the copolymer acts as a chemical agent that enhances the polishing rate on convex parts while the abrasive grains provide mechanical removal, achieving synergistic effect that resolves the contradiction between flatness and polishing rate
2Manufacturing precision
If polishing is performed on convex parts at high rate, then flatness improves, but concave parts are also excessively removed
Solution Approach 1:
The patent applies local quality by creating a polishing composition that exhibits spatially selective chemical reactivity. The anionic copolymer with acidic groups is designed to react preferentially with convex parts of the silicon nitride film, providing different chemical actions on different surface topographies. This localized chemical enhancement at convex regions while sparing concave regions achieves high flatness without excessive removal from concave parts
Solution Approach 2:
By controlling the pH parameter to be less than 6, the patent activates the chemical etching function of the anionic copolymer in a controlled manner. This parameter change creates a threshold effect where chemical reactivity is sufficiently high at convex parts to achieve rapid material removal and flatness improvement, while remaining low enough at concave parts to prevent excessive removal
3Manufacturing precision
If pH is increased to reduce chemical reactivity, then dishing is reduced, but polishing rate of silicon nitride decreases
Solution Approach 1:
The invention creates a composite polishing system combining abrasive grains with an anionic copolymer that has dual functionality: at pH less than 6, the copolymer provides chemical etching capability to enhance polishing rate, while the abrasive grains provide mechanical removal that ensures uniformity. This composite approach allows the system to achieve both high polishing rate and uniform material removal by leveraging the complementary mechanisms of chemical and mechanical action
Solution Approach 2:
The patent optimizes the pH parameter to a specific range (less than 6) where the anionic copolymer exhibits sufficient chemical reactivity to enhance polishing rate while maintaining controlled selectivity. This parameter optimization resolves the trade-off by finding the sweet spot where chemical etching is active enough to improve productivity but selective enough to maintain uniformity, unlike higher pH conditions where chemical reactivity is suppressed
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 a polishing rate of the convex parts at least 10 times higher than the concave parts, effectively removing irregularities and ensuring sufficient flatness of silicon nitride films.
Implementation Method 1
a convex part of silicon nitride of which surface is positively charged at a pH of less than 6 can be polished at remarkably higher polishing rate
Data Source
AI summary
The present invention provides a polishing composition with which differences in height of a SiN film can be sufficiently removed.The present invention is a polishing composition for use in polishing a polishing object having a surface which is positively charged at a pH of less than 6, containing water, abrasive grains, and an anionic copolymer having a specific unit structure, and having a pH of less than 6, wherein the anionic copolymer has at least two acidic groups having different acidities.