SiN Film Etching Uniformity via Basic Gas Pre-treatment
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Solution Overview
Problem
The existing methods for etching silicon nitride (SiN) films using halogen-containing gases face challenges with reduced etching amounts and non-uniformity, leading to inconsistent transistor characteristics due to oxidation of the SiN film surface, which prevents efficient penetration of the etching gas.
Innovation Solution
The etching process is divided into two stages, with an initial supply of a basic gas like ammonia to convert the oxidized SiNO film into a reaction product film that allows halogen-containing gases to penetrate, ensuring uniform etching of the SiN film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If RIE or plasma etching is used to etch SiN film, then etching amount is sufficient, but physical damages are inflicted on films other than SiN film
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using halogen-containing gases (CF4, SF6, CCl4, or CBr4) instead of traditional plasma etching methods. This chemical approach reduces physical damage to other films while achieving sufficient etching of the SiN film through selective chemical reactions.
2Object-affected harmful factors
If halogen-containing gas is used to etch SiN film with chemical reaction, then physical damages on other films are reduced, but etching amount decreases and etching amount distribution becomes non-uniform
Solution Approach 1:
The patent applies preliminary action by performing surface treatment on the SiN film before the main etching process. This pre-treatment modifies the surface properties of the SiN film, enabling more uniform penetration and reaction of the halogen-containing gas, thereby achieving uniform etching distribution across the wafer surface.
Solution Approach 2:
The patent introduces an intermediary substance or process step that facilitates the interaction between the halogen-containing gas and the SiN film. This intermediary mechanism ensures uniform gas distribution and reaction across the film surface, resolving the non-uniform etching problem while maintaining the chemical etching approach.
3Reliability
If SiN film surface is oxidized, then a protective layer is formed, but etching gas cannot sufficiently penetrate through the oxidized layer
Solution Approach 1:
The patent performs preliminary surface treatment to modify the oxidized SiN film surface before etching. This pre-treatment creates pathways or alters the surface chemistry to allow halogen-containing gas to penetrate through the oxidized layer, enabling subsequent efficient etching while the oxidized layer remains as a protective barrier.
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 enables efficient and uniform etching of SiN films with reduced damage, improving throughput and achieving desired thicknesses for stress films in semiconductor devices.
Implementation Method 1
since the etching is performed by chemical reaction with the SiN film, physical damages caused by a plasma on a film other than the SiN film may be reduced
Implementation Method 2
an initial supply of a basic gas like ammonia to convert the oxidized SiNO film into a reaction product film that allows halogen-containing gases to penetrate
Data Source
AI summary
A method for manufacturing a semiconductor device by etching a SiN film on a surface of a substrate by using a gas containing a halogen element includes supplying a gas containing a basic gas at the initial stage of a process for supplying the gas containing the halogen element to the surface of the SiN film. By supplying the gas containing the basic gas at the initial stage of the etching, a SiNO film covering the surface of the SiN film is changed to a film of reaction products mainly including water (H2O) and ammonium hexafluorosilicate ((NH4)2SiF6).