3D NAND Stack Notching via Oxygen-Modified Silicon Nitride
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Solution Overview
Problem
Conventional semiconductor processes struggle with uniformity and control during memory hole formation in 3D NAND structures due to material differences between silicon oxide and silicon nitride layers, as well as challenges in reactive-ion etching processes.
Innovation Solution
The method involves forming a stack of alternating layers of silicon oxide and silicon nitride, where the silicon nitride layers are characterized by an oxygen concentration greater than 5 at.%, and the oxygen concentration can vary through the layer to reduce notching and improve uniformity. This is achieved by adjusting the flow rate of oxygen-containing precursors during deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional reactive-ion etching is used to form memory holes through alternating silicon oxide and silicon nitride layers, then etching can proceed through the stack, but notching and striation occur due to material property differences between layers
Solution Approach 1:
The patent applies local quality by introducing oxygen specifically at the silicon nitride layer interfaces with silicon oxide layers, rather than uniformly throughout the entire stack. This localized oxygen concentration gradient (higher at interfaces, lower in bulk) modifies the etching behavior specifically at the problematic interface regions, reducing notching and striation while maintaining overall etching productivity through the stack.
Solution Approach 2:
The patent changes the material parameters of the silicon nitride layers by controlling oxygen incorporation during deposition. By adjusting deposition conditions to achieve specific oxygen concentration ranges (5-30 at.%), the etching response of silicon nitride is modified to better match silicon oxide, thereby improving uniformity of memory hole formation across the alternating layer stack.
2Ease of manufacture
If alternating layers of silicon oxide and silicon nitride are formed with conventional material properties, then the stack structure can be created, but inconsistent patterning occurs during etching
Solution Approach 1:
The patent modifies the chemical composition parameters of silicon nitride layers by incorporating oxygen during deposition. This parameter change (adding oxygen to achieve 5-30 at.% concentration) alters the etching characteristics of silicon nitride, making it more consistent with silicon oxide etching behavior, thereby eliminating inconsistent patterning while maintaining ease of stack formation.
Solution Approach 2:
The patent creates a composite material system where silicon nitride layers contain incorporated oxygen, effectively making them silicon oxynitride. This composite approach combines properties of both silicon oxide and silicon nitride, allowing the material to etch more uniformly with silicon oxide layers while maintaining the structural benefits of the alternating stack.
3Ease of manufacture
If silicon nitride layers are deposited without oxygen incorporation, then deposition is simpler, but lateral removal during etching extends too far causing excessive notching
Solution Approach 1:
The patent changes the deposition parameters by introducing oxygen-containing species during silicon nitride layer formation. This modification increases oxygen incorporation to 5-30 at.%, which fundamentally alters the etching behavior of the silicon nitride, reducing lateral removal extent to less than 50% of layer thickness and preventing excessive notching while maintaining reasonable deposition complexity.
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 uniformity and control of memory hole formation, reduces notching and striation, and improves the alignment of memory holes by modifying the material properties of the silicon nitride layers.
Implementation Method 1
forming a silicon oxide layer from a silicon-containing precursor and an oxygen-containing precursor
Implementation Method 2
forming a silicon nitride layer from a silicon-containing precursor, a nitrogen-containing precursor, and an oxygen-containing precursor
Data Source
AI summary
Exemplary semiconductor structures may include a stack of layers overlying a substrate. The stack of layers may include a first portion of layers, a second portion of layers overlying the first portion of layers, and a third portion of layers overlying the second portion of layers. The first portion of layers, the second portion of layers, and the third portion of layers may include alternating layers of a silicon oxide material and a silicon nitride material. One or more apertures may be formed through the stack of layers. A lateral notch in each individual layer of silicon nitride material at an interface of the individual layer of silicon nitride material and an overlying layer of silicon oxide material may extend a distance less than or about 100% of a distance corresponding to a thickness of the individual layer of silicon nitride material.