Multi-Layer Charge Storage Structure for Non-Volatile Memory
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Solution Overview
Problem
Charge retention characteristics and reliability of non-volatile memory devices are compromised due to lateral spreading of holes and electron leakage in the charge storage layer, particularly after extended periods following an erase operation.
Innovation Solution
A multi-layer charge storage structure is implemented, with specific energy band gaps and thicknesses for each layer, and varying nitrogen and oxygen concentrations to inhibit lateral hole spreading and electron leakage, including a first charge storage layer with a smaller energy band gap and greater thickness than subsequent layers, and additional layers with even smaller energy band gaps to create energy barriers preventing electron movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer charge storage layer is used, then the device structure is simple, but charge retention characteristics deteriorate due to lateral spreading of holes and electron leakage
Solution Approach 1:
The charge storage layer is divided into multiple sub-layers (first charge storage layer, second charge storage layer, third charge storage layer) with different energy band gaps and thicknesses. Each layer serves a specific function: the first layer with smaller energy band gap and greater thickness inhibits lateral hole spreading, while the second and third layers with larger energy band gaps prevent electron leakage, thereby resolving the contradiction between structural simplicity and charge retention reliability.
Solution Approach 2:
Different regions of the charge storage layer are assigned different material compositions and properties. The first charge storage layer has higher nitrogen concentration and lower oxygen concentration to reduce hole mobility, while the second and third layers have opposite compositions to create energy barriers against electron leakage. This local differentiation of properties enables simultaneous suppression of both hole spreading and electron leakage.
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 configuration minimizes residual hole increase and electron loss, enhancing charge retention and reliability by maintaining low-density hole distribution and preventing electron migration to adjacent layers.
Implementation Method 1
The first charge storage layer may be disposed between the semiconductor pattern and the gate electrodes, and may have a first energy band gap. The second charge storage layer may be disposed between the first charge storage layer and the semiconductor pattern, and may have a second energy band gap. The third charge storage layer may be disposed between the first charge storage layer and the gate electrodes, and may have a third energy band gap.
Implementation Method 2
A multi-layer charge storage structure is implemented, with specific energy band gaps and thicknesses for each layer, and varying nitrogen and oxygen concentrations to inhibit lateral hole spreading and electron leakage
Implementation Method 3
The charge tunneling layer and the charge blocking layer may be disposed under and over the charge trapping layer, respectively. Charges may be selectively stored in the charge trapping layer according energy band gap differences among these layers.
Data Source
AI summary
A non-volatile memory device includes gate electrodes stacked on a substrate, a semiconductor pattern penetrating the gate electrodes and connected to the substrate, and a charge storage layer between the semiconductor pattern and the gate electrodes. The charge storage layer includes a first charge storage layer between the semiconductor pattern and the gate electrodes, a second charge storage layer between the first charge storage layer and the semiconductor pattern, and a third charge storage layer between the first charge storage layer and the gate electrodes. An energy band gap of the first charge storage layer is smaller than those of the second and third charge storage layers. The first charge storage layer is thicker than the second and third charge storage layers.