Plasma Etching Selectivity via Si-O Bonded Deposition
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Solution Overview
Problem
In semiconductor manufacturing, the etching of silicon nitride films on silicon oxide films faces challenges with high bias application, leading to reduced selectivity ratios due to ion/assist reaction mechanisms, and there is a need for improved etching ratios in highly microminiaturized devices.
Innovation Solution
A plasma etching method using a gas mixture that generates a deposited film containing Si—O bonding, such as CH3F, O2, and SiF4, to enhance the selectivity of silicon nitride etching over silicon oxide, preventing etching of the silicon oxide film and optimizing the etching speed of silicon nitride.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high bias is applied to improve etching speed of silicon nitride film, then etching speed increases, but etching of silicon oxide film also progresses and selection ratio decreases
Solution Approach 1:
The patent applies local quality by creating a deposited film with specific composition (containing Si—O bonding) that selectively modifies the silicon oxide film surface. This localized modification protects the silicon oxide film from ion/assist etching while allowing radical etching of silicon nitride to proceed, thus maintaining high selection ratio even at high bias conditions.
Solution Approach 2:
The deposited film acts as an intermediary layer between the plasma environment and the silicon oxide film. This intermediary film containing Si—O bonding preferentially forms on the silicon oxide surface and protects it from direct ion bombardment, enabling high bias application without compromising the selection ratio.
2Manufacturing precision
If fluorocarbon gas is used to deposit film on silicon oxide to reduce etching speed, then selection ratio increases, but etching speed of silicon nitride film decreases
Solution Approach 1:
The patent changes the compositional parameter of the deposited film by incorporating Si—O bonding through specific gas mixture composition (containing SiF4 and O2 along with fluorocarbon gas). This compositional change enables the deposited film to provide selective protection to silicon oxide while maintaining compatibility with silicon nitride etching, thus improving selection ratio without significantly reducing etching speed.
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 method significantly improves the selectivity ratio of silicon nitride to silicon oxide films, allowing for precise control of etching speeds and preventing damage to the silicon oxide film, which is crucial for microminiaturized semiconductor devices.
Implementation Method 1
plasma etching method
Implementation Method 2
a fluorocarbon deposited film is deposited on the silicon oxide film
Implementation Method 3
the silicon nitride film is etched on the basis of a radical reaction involving a fluorine radical (F*) as main etching species
Implementation Method 4
etching based on an ion/assist reaction mechanism mainly involving CF3 ions as main etching spices progresses for the silicon oxide film
Data Source
AI summary
A plasma etching method that can improve an etching selection ratio of a film to be etched to a film different from the film to be etched compared with the related art is provided. The present invention provides a plasma etching method for selectively etching a film to be etched against a film different from the film to be etched, in which plasma etching of the film to be etched is performed using a gas that can cause to generate a deposited film containing similar components as components of the different film.