Dry Etching Gas Composition for Selective Silicon Oxide Removal
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Solution Overview
Problem
Existing dry etching methods face challenges in selectively etching silicon oxide and silicon nitride films relative to low dielectric constant materials, often damaging these films due to ion penetration and ultraviolet radiation, which alters their electric characteristics.
Innovation Solution
A dry etching gas composition incorporating a hydrofluorocarbon gas with an unsaturated bond, specifically 1,1,4,4-tetrafluoro-1,3-butadiene, is used, which allows for selective etching of silicon oxide and silicon nitride films by producing ions with 3 to 5 carbon atoms, minimizing damage to mask materials and low dielectric constant films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etching methods using fluorocarbon or hydrofluorocarbon gas plasmas are used to selectively etch silicon oxide films, then etching selectivity is improved, but damage to mask materials and silicon occurs due to ion penetration and ultraviolet radiation
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas by using a specific hydrofluorocarbon compound (C3H3F3, C4H5F5, or C5H7F7) with a particular molecular structure containing unsaturated bonds. This parameter change in gas composition produces different plasma characteristics that reduce ion damage while maintaining etching selectivity
Solution Approach 2:
The invention uses a composite approach by combining specific hydrofluorocarbon compounds with unique molecular structures (unsaturated bonds with specific hydrogen and fluorine ratios) to create a plasma environment that simultaneously achieves selective etching and reduced damage, effectively combining multiple beneficial properties in one gas system
2Reliability
If fluorocarbon gas plasmas with unsaturated bonds or cyclic structures are used, then a protection film is deposited on silicon nitride, polysilicon, and resist, but the etching process becomes more complex and requires precise gas composition control
Solution Approach 1:
The patent simplifies the system by changing to a single hydrofluorocarbon compound with a specific molecular formula (C3H3F3, C4H5F5, or C5H7F7) that inherently provides both protection film formation and selective etching capabilities, eliminating the need for complex multi-gas mixture control
3Manufacturing precision
If HFC gas including one carbon atom is used to selectively etch silicon nitride film, then selectivity against silicon oxide and polysilicon is improved, but the etching rate and efficiency are reduced
Solution Approach 1:
The patent changes the carbon atom count parameter in the etching gas from one carbon atom (in conventional HFC gases) to three, four, or five carbon atoms in the hydrofluorocarbon compound. This parameter change increases etching rate while the unique molecular structure with unsaturated bonds maintains high selectivity
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 enables high-selectivity etching of silicon oxide and silicon nitride films relative to carbon-containing silicon-based films, reducing damage and preserving the electric characteristics of low dielectric constant materials, while simultaneously etching both films with improved precision.
Implementation Method 1
a dry etching gas composition incorporating a hydrofluorocarbon gas with an unsaturated bond, specifically 1,1,4,4-tetrafluoro-1,3-butadiene, is used, which allows for selective etching of silicon oxide and silicon nitride films by producing ions with 3 to 5 carbon atoms
Data Source
AI summary
A silicon oxide film or a silicon nitride film is selectively etched by using an etching gas composition including a hydrofluorocarbon that has an unsaturated bond in its molecule and is represented by CxHyFz, wherein x is an integer of from 3 to 5, and relationships y+z≤2x and y≤z are satisfied. Also, a silicon oxide film is etched with high selectivity relative to a silicon nitride film by controlling the ratio among the hydrofluorocarbon, oxygen, argon, etc., included in the hydrofluorocarbon-containing etching gas composition.