Compositionally Modulated Charge Trap Layer for 3D Memory
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in achieving high-density storage and efficient charge retention due to limitations in the composition and structure of charge storage layers in vertical NAND strings.
Innovation Solution
A three-dimensional memory device is developed with a compositionally modulated charge storage layer comprising vertically alternating stacks of silicon nitride and silicon oxynitride portions, integrated with a tunneling dielectric and vertical semiconductor channel, formed through an alternating stack of insulating and sacrificial layers over a substrate, enabling enhanced charge storage and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform charge storage layer is used in vertical NAND strings, then the device structure is simple, but charge retention and trapping capabilities are insufficient for high-density storage
Solution Approach 1:
The charge storage layer is segmented into multiple distinct portions: a first charge storage layer (silicon nitride) and a second charge storage layer (silicon oxynitride) with different compositions and functions. This segmentation allows each layer to specialize in specific charge trapping tasks, improving overall charge retention while managing complexity through functional division
Solution Approach 2:
Different regions of the charge storage layer are given different local qualities through the use of silicon nitride in the first portion (optimized for charge trapping) and silicon oxynitride in the second portion (optimized for charge retention). This local differentiation of material properties enables enhanced performance in specific functional zones without requiring complete structural redesign
2Quantity of substance
If higher density storage is implemented in vertical NAND strings, then storage capacity increases, but charge retention time decreases
Solution Approach 1:
The charge storage layer uses a composite structure combining silicon nitride and silicon oxynitride materials. The silicon nitride portion provides high charge trapping density for increased storage capacity, while the silicon oxynitride portion contributes to extended charge retention time. This composite material approach enables simultaneous achievement of high density and long retention without compromising either parameter
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 charge trapping capabilities and retention time in three-dimensional NAND memory devices, improving their performance and efficiency in high-density storage applications.
Implementation Method 1
the silicon nitride portions of the compositionally modulated charge storage layer have a greater capacity to trap electrical charges than the silicon oxynitride portions
Data Source
AI summary
Threshold voltage shift due to programming of a neighboring memory element can be reduced or suppressed by forming a compositionally modulated charge storage layer in a three-dimensional memory device. The compositionally modulated charge storage layer can be formed by providing an oxygen-containing dielectric silicon compound layer outside a tunneling dielectric layer, and subsequently nitriding portions of the oxygen-containing dielectric silicon compound layer only at levels of the control gate electrodes. An alternating stack of sacrificial material layers and insulating layers can be employed to form a memory stack structure therethrough. After removal of the sacrificial material layers, a nitridation process can be performed to convert physically exposed portions of the oxygen-containing dielectric silicon compound layer into silicon nitride portions, which are vertically spaced from one another by remaining oxygen-containing dielectric silicon compound portions that have inferior charge trapping property to the silicon nitride portions.