Plasma Etching Gas for Selective Silicon Nitride Removal
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Solution Overview
Problem
Existing etching methods using fluorocarbon gases do not effectively differentiate between silicon nitride and other materials, leading to non-selective etching and environmental concerns due to high global warming potential gases like CF4 and SF6.
Innovation Solution
An etching method employing a fluorine compound with 3 or fewer carbon atoms, containing a carbon-oxygen double bond and an ether bond, is used in plasma etching to selectively target silicon nitride, with concentrations between 0.5 vol% and 40 vol%, along with dilution gases like nitrogen and noble gases, to achieve selective etching without using high global warming potential gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If perfluorinated compound gases (CF4, SF6) are used for etching, then etching capability is improved, but global warming potential increases
Solution Approach 1:
The invention changes the chemical composition parameters of the etching gas from perfluorinated compounds to fluorocarbon compounds with specific structural characteristics (unsaturated bonds, 3 or fewer carbon atoms). This parameter change maintains etching capability while reducing global warming potential, as the new gas composition differs fundamentally from the high-GWP perfluorinated compounds.
Solution Approach 2:
The invention replaces long-lived perfluorinated compounds that persist in the atmosphere with fluorocarbon compounds that have shorter atmospheric lifetimes. The used etching gas is discharged to the atmosphere, and the alternative gases are designed to degrade more quickly, reducing long-term environmental accumulation and global warming impact.
2Object-affected harmful factors
If fluorocarbon gases are used to reduce global warming potential, then environmental impact is reduced, but selective etching capability is insufficient
Solution Approach 1:
The invention specifies particular local chemical structures within fluorocarbon compounds - specifically requiring unsaturated bonds and limiting carbon atoms to 3 or fewer. These localized structural features create reactive sites that enable selective etching of silicon nitride while maintaining low global warming potential, thus resolving the contradiction between environmental friendliness and etching selectivity.
Solution Approach 2:
The invention uses composite gas compositions combining fluorocarbon compounds with specific structural characteristics. This composite approach - mixing gases with complementary properties - achieves both selective etching of silicon nitride and reduced global warming potential, overcoming the limitations of single-gas systems.
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 allows for the selective etching of silicon nitride while minimizing environmental impact by using lower global warming potential gases, enhancing etching selectivity and reducing environmental burden, and is applicable in semiconductor manufacturing for structures like 3D-NAND flash memory and logic devices.
Implementation Method 1
bringing, in the presence of plasma, an etching gas containing a fluorine compound
Data Source
AI summary
An etching method including an etching step of bringing, in the presence of plasma, an etching gas containing a fluorine compound with three or fewer carbon atoms having at least one bond of a carbon-oxygen double bond and an ether bond in a molecule into contact with a target etching member having an etching target and a non-etching target, and selectively etching the etching target in comparison with the non-etching target. A concentration of the fluorine compound in the etching gas is 0.5 vol% or more to 40 vol% or less, and the etching target has silicon nitride.