Selective Nitride Film Removal via Oxidation and HF Etching
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Solution Overview
Problem
Existing methods for etching silicon nitride films on semiconductor wafers also remove the underlying thermally-oxidized films, leading to damage of the silicon substrate, as they do not allow for selective removal of the nitride films.
Innovation Solution
A substrate processing method involving oxygen-containing plasma contact followed by HF gas supply to convert the nitride film into an oxide film, which is then selectively etched by hydrofluoric acid, ensuring the nitride film can be removed without affecting the thermally-oxidized film or the silicon substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a compound gas containing fluorine is converted into plasma to etch the silicon nitride film, then the silicon nitride film can be removed, but the thermally-oxidized film is also etched and the silicon substrate is impaired
Solution Approach 1:
The patent applies preliminary action by first converting the silicon nitride film into a silicon oxide film through oxygen plasma treatment before etching. This preliminary oxidation step creates a chemical transformation that enables selective removal: the converted silicon oxide film from the nitride layer can be etched by HF gas, while the original thermally-oxidized silicon oxide film remains resistant to HF etching, thus protecting the substrate
Solution Approach 2:
The patent utilizes parameter changes by altering the chemical state of the silicon nitride film through oxidation. By changing the film composition from nitride to oxide form, and then exploiting the different etching characteristics of oxide films (converted vs. thermally-oxidized), the process achieves high selectivity. The parameter change in chemical composition enables the differentiation between the two oxide films during the HF etching step
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 removal of nitride films, preserving the thermally-oxidized films and preventing damage to the silicon substrate, thereby enhancing the reliability of semiconductor device manufacturing.
Implementation Method 1
The oxygen-containing plasma changes the nitride film into an oxide film
Implementation Method 2
the oxide film changed from the nitride film is selectively etched by hydrofluoric acid produced from the HF gas
Implementation Method 3
In the oxygen-containing plasma contact step, active species in the oxygen-containing plasma can move substantially parallel to the side surfaces of the conductive portion and can be in contact with the nitride film
Data Source
AI summary
A substrate processing method capable of selectively removing a nitride film. Oxygen plasma containing plasmarized oxygen gas is made to be in contact with a silicon nitride film, which is made of SiN, of a wafer to thereby cause the silicon nitride film to be changed to a silicon monoxide film. The silicon monoxide film is selectively etched by hydrofluoric acid generated from HF gas supplied toward the silicon monoxide film.