Oxygen Treatment for Nitride Etching Uniformity
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Solution Overview
Problem
Conventional etching techniques face challenges in achieving uniform lateral etching of silicon nitride in high aspect ratio trenches, leading to uneven cell formation and potential deformation of structures due to inadequate precursor diffusion and selectivity issues, particularly in 3D NAND processing where wet etching can be overly aggressive and dry etching struggles with complete penetration.
Innovation Solution
A dry etching method involving the use of oxygen-containing and fluorine-containing plasma effluents in a remote plasma system, where oxygen passivates silicon nitride surfaces before fluorine etching, allowing for controlled and uniform etching across the trench, maintaining selectivity and minimizing material loss, and potentially performed in a single processing chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet HF etching is used to laterally etch silicon nitride, then the etching speed is fast, but the etching becomes overly aggressive causing deformation of structures and uneven cell formation
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using oxygen plasma to modify the silicon nitride surface chemistry. This transforms the surface properties to enable controlled, uniform lateral etching while maintaining high etching speed, thus resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent employs a composite approach by combining oxygen plasma treatment with fluorine-based etching. This composite process creates a synergistic effect where oxygen modifies the surface to enhance subsequent fluorine etching uniformity, achieving both fast etching speed and uniform cell formation
2Length of moving object
If dry etching with local plasma is used to penetrate constrained trenches, then the penetration capability is improved, but substrate damage occurs through electric arcs
Solution Approach 1:
The patent introduces oxygen plasma as an intermediary step before fluorine etching. This intermediary treatment modifies the silicon nitride surface to facilitate more uniform and controlled fluorine etching, reducing the need for aggressive plasma conditions that cause substrate damage while maintaining effective trench penetration
Solution Approach 2:
The patent applies preliminary oxygen plasma treatment to the silicon nitride surface before performing the main fluorine etching process. This preliminary action prepares the surface to receive the fluorine etchant more uniformly, enabling effective penetration of constrained trenches without requiring damaging high-power plasma conditions
3Device complexity
If conventional etching is used on high aspect ratio trenches, then the etching process is simple, but precursor diffusion is inadequate leading to non-uniform etching
Solution Approach 1:
The patent implements a continuous two-step process where oxygen plasma treatment is immediately followed by fluorine etching without breaking vacuum. This continuous action ensures uniform precursor diffusion throughout the high aspect ratio trench while maintaining process simplicity through integration in a single chamber
Solution Approach 2:
The patent changes the chemical state of the trench environment by introducing oxygen plasma, which modifies the surface chemistry and enhances subsequent fluorine precursor diffusion. This parameter change enables uniform etching throughout high aspect ratio trenches while keeping the overall process relatively simple through sequential gas phase treatments
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 enables uniform etching profiles across the trench, reducing the difference in etched silicon nitride layers by less than 2 nm between top and bottom regions, preventing deformation and ensuring uniformly sized cells, while maintaining high selectivity and reducing the need for multiple chamber processes.
Implementation Method 1
passivating exposed surfaces of the silicon nitride with the oxygen-containing plasma effluents. The passivating may oxidize a portion of the silicon nitride.
Implementation Method 2
forming a plasma of the oxygen-containing precursor to produce oxygen-containing plasma effluents
Implementation Method 3
laterally etching the layers of silicon nitride from sidewalls of the trench
Implementation Method 4
forming plasma effluents of the fluorine-containing precursor and the oxygen-containing precursor
Data Source
AI summary
Exemplary methods for laterally etching silicon nitride may include flowing oxygen-containing plasma effluents into a processing region of a semiconductor processing chamber. A substrate positioned within the processing region may include a trench formed through stacked layers including alternating layers of silicon nitride and silicon oxide. The methods may include passivating exposed surfaces of the silicon nitride with the oxygen-containing plasma effluents. The methods may include flowing a fluorine-containing precursor into the remote plasma region while maintaining the flow of the oxygen-containing precursor. The methods may include forming plasma effluents of the fluorine-containing precursor and the oxygen-containing precursor. The methods may include flowing the plasma effluents into the processing region of the semiconductor processing chamber. The methods may also include laterally etching the layers of silicon nitride from sidewalls of the trench.