Segmented Charge Layer in Laminated Flash Memory
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Solution Overview
Problem
Flash memory devices with multilayered cells have low reliability in retaining data for long periods due to charge layer continuity, leading to electron diffusion and data loss.
Innovation Solution
A semiconductor memory device with a substrate having alternately laminated dielectric and electrode films, featuring a tunnel layer, a charge layer made of a different material, a block layer, and a conductor buried inside the through hole, where the charge layer is split for each electrode film to prevent electron leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dielectric films and electrode films are alternately laminated with a continuous charge layer in the through hole, then the manufacturing process is simplified, but electron diffusion occurs and data retention reliability deteriorates
Solution Approach 1:
The continuous charge layer is divided into multiple separate charge layers, each corresponding to a specific electrode film. The charge layers are isolated from each other by block layers, preventing electron diffusion between adjacent memory cells while maintaining the multilayered cell structure. This segmentation resolves the contradiction by sacrificing continuous charge layer formation (increasing manufacturing steps) to achieve reliable data retention.
2Device complexity
If a single continuous charge layer is formed in the through hole, then the device structure is simplified, but electron leakage occurs between adjacent electrode films leading to data loss
Solution Approach 1:
The single continuous charge layer is segmented into multiple discrete charge layers, each confined to a specific region between the tunnel layer and a corresponding electrode film. Block layers are inserted between adjacent charge layers to electrically isolate them, preventing electron leakage and data loss while maintaining manageable structural complexity.
Solution Approach 2:
Block layers are introduced as intermediary structures between adjacent charge layers. These block layers act as electrical insulators that prevent electron diffusion from one charge layer to another, thereby preventing data loss without requiring complete structural redesign of the charge storage mechanism.
3Quantity of substance
If the charge layer extends continuously through the through hole, then charge storage capacity is increased, but electron diffusion to adjacent cells increases causing data retention problems
Solution Approach 1:
The continuous charge storage medium is segmented into multiple discrete charge layers, each associated with a specific electrode film and memory cell. This segmentation maintains total charge storage capacity across multiple cells while preventing electron diffusion between cells through the introduction of block layers, thereby resolving the reliability issue.
Solution Approach 2:
Different regions of the through hole are assigned different functional qualities: tunnel layers for charge injection, charge layers for local charge storage adjacent to specific electrode films, and block layers for electrical isolation. This local differentiation allows each charge layer to store charge effectively while preventing unwanted electron diffusion to adjacent cells.
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
The solution enhances data retention reliability by confining electrons within the charge layer, reducing the likelihood of diffusion and maintaining data integrity over time.
Implementation Method 1
a tunnel layer formed on an inner side surface of the through hole and made of a dielectric material; a charge layer formed between the tunnel layer and the electrode film
Implementation Method 2
a block layer formed between the charge layer and the electrode film and made of a dielectric material different from that of the charge layer
Data Source
AI summary
A laminated body is formed by alternately laminating a plurality of dielectric films and electrode films on a silicon substrate. Next, a through hole extending in the lamination direction is formed in the laminated body. Next, a selective nitridation process is performed to selectively form a charge layer made of silicon nitride in a region of an inner surface of the through hole corresponding to the electrode film. Next, a high-pressure oxidation process is performed to form a block layer made of silicon oxide between the charge layer and the electrode film. Next, a tunnel layer made of silicon oxide is formed on an inner side surface of the through hole. Thus, a flash memory can be manufactured in which the charge layer is split for each electrode film.