3D NAND Stacked Insulating Layers With Slit Wall Protection
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Solution Overview
Problem
In the production of three-dimensional nonvolatile memory, such as three-dimensional NAND memory, it is challenging to prevent the unintentional replacement of insulating layers with conductive material in regions where contacts are formed, leading to incomplete removal of sacrificial layers, which affects the integrity and insulation of the semiconductor storage device.
Innovation Solution
A method involving the formation of a silicon oxide film on the inner wall surfaces of slits using chemical dry etching and plasma enhanced atomic layer deposition to create a thicker protective film, ensuring that the sacrificial silicon nitride layer is not replaced with conductive material during the process, thereby maintaining the insulating properties and preventing unintended conductive material infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride film is formed as a sacrificial layer and oxidized to form a protective oxide film on slit wall surfaces, then the insulating layer protection is improved, but the oxide film thickness is limited and unintentional replacement with conductive material may still occur
Solution Approach 1:
A first protective film (silicon oxide) is formed on the slit wall surfaces before the sacrificial layer removal process. This preliminary protective layer prevents etchant from reaching and removing the sacrificial layer in contact regions, ensuring reliable insulation while allowing the sacrificial layer to be completely removed in memory regions. The protective film is formed in advance to establish protection before the replacement process begins.
Solution Approach 2:
The protective film is selectively formed only on the inner wall surfaces of the slits, creating a localized protective barrier. This local application ensures that the sacrificial layer is protected in contact regions where insulation is needed, while allowing complete removal in memory regions where conductive material should be deposited. The selective positioning of the protective film resolves the contradiction by providing thickness where needed without preventing necessary removal elsewhere.
2Reliability
If the protective oxide film is made thicker to prevent unintentional replacement, then insulation reliability is improved, but the formation process becomes more difficult and complex
Solution Approach 1:
The first protective film acts as an intermediary layer between the sacrificial layer and the etchant/conductive material. This intermediate protective barrier prevents direct interaction between the etchant and the sacrificial layer in contact regions, ensuring reliable insulation without requiring excessively thick films. The intermediary layer provides sufficient protection while maintaining processability and manufacturing ease.
3Productivity
If the sacrificial layer is completely removed to form conductive material, then memory cell functionality is improved, but insulating layers in contact regions may be unintentionally replaced
Solution Approach 1:
The first protective film is formed in advance to counteract the potential harmful effect of etchant reaching the sacrificial layer in contact regions. This preliminary protective measure prevents unintentional removal of the sacrificial layer where insulation is required, while allowing complete removal in memory regions. The anti-action is applied selectively to protect only the necessary regions during the replacement process.
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 resistance to etching and insulation performance, allows for a thicker protective film, and reduces production costs by ensuring the sacrificial layers remain as insulating layers, thus maintaining the structural integrity and functionality of the semiconductor storage device.
Implementation Method 1
a silicon oxide film is then formed on the inside wall surfaces of slits by oxidizing the silicon nitride film
Implementation Method 2
A method involving the formation of a silicon oxide film on the inner wall surfaces of slits using chemical dry etching
Implementation Method 3
plasma enhanced atomic layer deposition to create a thicker protective film
Data Source
AI summary
According to one embodiment, a semiconductor storage device includes a stacked body above a substrate. The stacked body includes a first stacked region in which a first insulating layer and a second insulating layer are alternately stacked and a second stacked region in which a conductive layer and the first insulating layer are alternately stacked. The semiconductor storage device includes a memory pillar that extends through the second stacked region of the stacked body in a stacking direction. The second insulating layer comprising a first insulating material within the first stacked region and a second insulating material on ends of the second insulating layer in a direction intersecting to the stacking direction.