3D Memory Discrete Charge Storage via Selective Oxidation
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently integrating discrete charge storage elements and width-modulated memory elements, particularly in forming vertical stacks with precise lateral spacing and conductive layers, which affects storage capacity and operational efficiency.
Innovation Solution
The method involves forming an alternating stack of insulating and sacrificial material layers, creating memory openings, and then selectively replacing the sacrificial layers with conductive materials while oxidizing silicon nitride layers to form discrete charge storage elements and semiconductor channels, ensuring precise lateral spacing and conductive pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If discrete charge storage elements are integrated in three-dimensional memory devices, then storage capacity is improved, but manufacturing precision requirements increase due to the need for precise lateral spacing and conductive pathways
Solution Approach 1:
The memory device is divided into discrete charge storage elements arranged in vertical stacks, with each element separated by insulating layers. This segmentation allows independent control and precise positioning of each charge storage element, achieving high storage capacity while maintaining manufacturing precision through modular assembly.
Solution Approach 2:
Insulating layers are introduced as intermediary structures between conductive layers to define precise lateral spacing. These insulating layers act as mediators that control the position and separation of charge storage elements, enabling accurate lateral spacing while allowing vertical stacking for high capacity.
2Productivity
If width-modulated memory elements are formed with precise lateral spacing, then operational efficiency is improved, but device complexity increases due to the alternating stack structure and selective replacement processes
Solution Approach 1:
Sacrificial material layers are deposited in advance during the formation of alternating stacks, serving as temporary structures that enable precise pattern definition. These sacrificial layers are later selectively removed to create voids for conductive pathways, simplifying the overall process by breaking down complex patterning steps into sequential, manageable actions.
Solution Approach 2:
Sacrificial material layers are intentionally discarded after serving their temporary function of defining structural patterns. By removing these sacrificial layers selectively, the device achieves its final complex structure through a simplified process of deposition and removal, reducing manufacturing steps.
3Quantity of substance
If vertical stacks of charge storage material portions are formed, then storage capacity is improved, but the manufacturing process becomes more complex due to selective oxidation and replacement steps
Solution Approach 1:
The manufacturing process utilizes parameter changes in material properties during thermal oxidation to selectively convert silicon nitride layers into silicon oxide. This chemical transformation enables selective formation of insulating layers at specific vertical positions, simplifying the manufacturing of vertical charge storage stacks through controlled chemical reactions rather than complex physical patterning.
Solution Approach 2:
Selective thermal oxidation replaces complex mechanical or lithographic patterning processes with a chemical etching mechanism. By using oxygen diffusion and oxidation reactions, the process selectively transforms silicon nitride to silicon oxide at desired locations, simplifying the manufacturing of vertical stacks compared to direct mechanical patterning methods.
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 the creation of efficient three-dimensional memory devices with enhanced storage capacity and operational efficiency by forming discrete charge storage elements and semiconductor channels with precise lateral spacing, improving data storage and retrieval processes.
Implementation Method 1
oxidizing portions of the silicon nitride layers and the continuous silicon nitride charge storage material layer exposed in the laterally-extending cavities to form silicon oxide insulating layers
Data Source
AI summary
A method of forming a memory device includes forming an alternating stack of disposable material layers and silicon nitride layers over a substrate, forming a memory opening through the alternating stack, forming a memory film and a vertical semiconductor channel in the memory opening, where the memory film includes a continuous silicon nitride charge storage material layer and a tunneling dielectric layer, forming a backside trench through the alternating stack, forming laterally-extending cavities by removing the disposable material layers selective to the silicon nitride layers through the backside trench, oxidizing portions of the silicon nitride layers and the continuous silicon nitride charge storage material layer exposed in the laterally-extending cavities to form silicon oxide insulating layers and to separate the continuous silicon nitride charge storage material layer into a vertical stack of discrete silicon nitride charge storage material portions, and replacing remaining portions of the silicon nitride layers with electrically conductive layers.