Selective Silicon Oxide Etching via Carbon Deposition
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Solution Overview
Problem
The challenge in semiconductor manufacturing is to selectively etch silicon oxide films with respect to silicon nitride films without forming recesses, as the binding energies of Si—O and Si—N make it difficult to increase the selectivity of the silicon oxide film over the silicon nitride film, especially when using optical lithography for miniaturization.
Innovation Solution
An etching method involving a processing gas mixture with a CHF-based gas and a plasma excitation gas, where the flow rate ratio of CHF-based gas to plasma excitation gas is set to 1/15 or higher, generating a plasma to increase the etching rate of silicon oxide films while minimizing the etching rate of silicon nitride films by depositing carbon-based protective films on the silicon nitride surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ion energy of the plasma is increased to increase etching rate of silicon oxide film, then etching rate of silicon oxide film is improved, but etching rate of silicon nitride film also increases causing recess formation
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma by introducing CHF3 gas, which alters the etching chemistry from purely physical ion bombardment to a chemical reaction-based etching process. This enables selective etching of silicon oxide over silicon nitride by exploiting differences in chemical reactivity rather than relying on ion energy alone
Solution Approach 2:
The patent introduces carbon-based deposits as an intermediary protective layer on the silicon nitride film surface. These deposits act as a barrier that prevents direct contact between the plasma and silicon nitride, thereby protecting it from etching while allowing silicon oxide to be etched selectively
2Manufacturing precision
If chemical reactivity difference is used to increase selectivity, then etching selectivity is improved, but etching rate may be insufficient for high productivity
Solution Approach 1:
The patent optimizes the flow rate ratio of CHF3 gas to plasma excitation gas to be 1/15 or higher, which controls the concentration of reactive species in the plasma. This parameter adjustment enables simultaneous achievement of high etching rate and high selectivity by balancing chemical reactivity with process efficiency
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 approach enhances the selectivity of silicon oxide films over silicon nitride films, allowing for precise pattern formation without recesses, even at short pitches, by controlling the etching rates and reducing the formation of recesses on the silicon nitride surface.
Implementation Method 1
introducing a processing gas containing a plasma excitation gas and a CHF-based gas into a processing chamber... etching the silicon oxide film selectively with respect to the silicon nitride film formed on the substrate in the processing chamber by generating a plasma in the processing chamber
Implementation Method 2
carbon-based deposits are deposited on the surface of the silicon nitride film. Thus, even if the amount of fluorine contributing to etching increases, the etching rate of the silicon nitride film does not increase as much as that of the silicon oxide film
Data Source
AI summary
An etching method and apparatus for etching a silicon oxide film selectively with respect to a silicon nitride film formed on a substrate are provided. A processing gas containing a plasma excitation gas and a CHF-based gas is introduced into a processing chamber such that a flow rate ratio of the CHF-based gas to the plasma excitation gas is 1/15 or higher. By generating a plasma in the processing chamber, the silicon oxide film is etched selectively with respect to the silicon nitride film formed on the substrate in the processing chamber.