CMP Aqueous Dispersion for Selective Silicon Nitride Polishing
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) aqueous dispersions are unable to effectively polish silicon nitride films at a practical rate, leading to issues with silicon oxide film removal and potential damage to underlying layers, necessitating the use of hot phosphoric acid for etching, which can result in incomplete removal or damage.
Innovation Solution
A CMP aqueous dispersion comprising colloidal silica with an average particle size of 10 to 60 nm, an organic acid with two or more carboxyl and one or more hydroxyl groups, and a quaternary ammonium compound, with a pH of 3 to 5, which selectively polishes silicon nitride films while controlling the polishing rate of silicon oxide films, thereby enabling simultaneous polishing of both materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP aqueous dispersions are used to polish silicon oxide films, then the silicon oxide film can be removed, but the silicon nitride film cannot be polished at a practical rate and may be damaged
Solution Approach 1:
The patent changes the chemical parameters of the CMP aqueous dispersion by introducing specific organic acids (tartaric acid, malic acid, or citric acid) with defined molecular structures containing carboxyl and hydroxyl groups, and adjusting the pH to 3-5. This chemical parameter modification enables the silicon nitride film to be polished at a practical rate while maintaining film integrity, resolving the contradiction between polishing productivity and film reliability.
Solution Approach 2:
The patent creates a composite polishing system by combining colloidal silica particles with specific organic acids (tartaric acid, malic acid, or citric acid) and quaternary ammonium compounds in an aqueous dispersion. This composite material formulation achieves both high polishing rate for silicon nitride and controlled polishing rate for silicon oxide, simultaneously improving productivity and reliability.
2Productivity
If hot phosphoric acid is used to remove silicon nitride film by etching, then the silicon nitride film can be removed, but the lower layer may be damaged or the etching may be incomplete
Solution Approach 1:
The patent replaces the chemical etching method (hot phosphoric acid) with a mechanical-chemical polishing method using CMP aqueous dispersion. This substitution provides more controlled and uniform removal of the silicon nitride film, achieving complete removal without damaging the lower layer, thus improving both productivity and manufacturing precision.
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 significantly increased polishing rate ratio of silicon nitride to silicon oxide films, allowing for selective and efficient removal of silicon nitride films without damaging the underlying silicon oxide films, enhancing the reliability and performance of semiconductor devices.
Implementation Method 1
chemical mechanical polishing
Implementation Method 2
chemical mechanical polishing
Implementation Method 3
polishing rate ratio of the silicon nitride film to the silicon oxide film
Data Source
AI summary
A chemical mechanical polishing aqueous dispersion includes (A) colloidal silica having an average particle size calculated from the specific surface area determined by the BET method of 10 to 60 nm, (B) an organic acid having two or more carboxyl groups and one or more hydroxyl groups in one molecule, and (C) a quaternary ammonium compound shown by the following general formula (1),wherein R1 to R4 individually represent hydrocarbon groups, and M− represents an anion, the chemical mechanical polishing aqueous dispersion having a pH of 3 to 5.