Vertical Memory Tunnel Insulation Layer Band Gap Engineering
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Solution Overview
Problem
Vertical memory devices face challenges in achieving optimal performance due to the trade-off between program/erase operation speed and retention characteristics, which are influenced by the thickness and nitrogen concentration of tunnel insulation layers, leading to reliability issues.
Innovation Solution
A tunnel insulation layer structure comprising multiple layers with varying band gap energies and nitrogen concentrations, including silicon oxide and silicon oxy-nitride, is implemented to improve reliability by adjusting the thickness and nitrogen content of each layer, and partially oxidizing processes are used to reduce shallow trap sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness or equivalent oxide thickness (EOT) of the tunnel insulation layer is increased, then the retention characteristic of the vertical memory device is improved, but the program/erase operation speed becomes slow
Solution Approach 1:
The tunnel insulation layer is divided into multiple sub-layers (first tunnel insulation layer, second tunnel insulation layer, third tunnel insulation layer, fourth tunnel insulation layer, and fifth tunnel insulation layer) with alternating high and low band gap energies. This segmentation allows each layer to contribute differently to charge blocking, achieving both retention and fast operation
Solution Approach 2:
Different regions of the tunnel insulation layer structure have different band gap energies and nitrogen concentrations optimized for specific functions. The high band gap layers provide strong charge blocking for retention, while the low band gap layers facilitate charge tunneling for fast program/erase operations
2Speed
If the thickness or equivalent oxide thickness (EOT) of the tunnel insulation layer is decreased, then the program/erase operation speed is improved, but the retention characteristic is degraded
Solution Approach 1:
The tunnel insulation layer is segmented into multiple sub-layers with alternating band gap energies, allowing the overall structure to be thinner while maintaining retention through the cumulative blocking effect of high band gap layers
Solution Approach 2:
The tunnel insulation layer uses composite materials with different band gap energies (silicon oxide and silicon oxy-nitride) to create a structure that provides both fast charge tunneling pathways and effective charge blocking, resolving the retention-speed tradeoff
3Reliability
If nitrogen concentration in the tunnel insulation layer is increased, then the retention characteristic is improved, but initial voltage shift problems occur
Solution Approach 1:
Nitrogen concentration is locally optimized in specific layers (second and fourth tunnel insulation layers have higher nitrogen concentrations >20 at %) to provide charge blocking, while other layers have lower nitrogen concentrations to minimize voltage shift
Solution Approach 2:
The nitrogen concentration parameter is varied across different layers rather than being uniform, with specific layers having nitrogen concentrations higher than 20 at % and others lower than 10 at %, optimizing both retention and voltage stability
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 reliability of vertical memory devices by optimizing the electrical characteristics of the tunnel insulation layers, reducing charge loss and initial voltage shift problems, while maintaining program/erase operation speed.
Implementation Method 1
The second tunnel insulation layer has a second band gap energy which is lower than the first band gap energy. The third tunnel insulation layer has a third band gap energy which is higher than the second band gap energy.
Implementation Method 2
partially oxidizing processes are used to reduce shallow trap sites
Data Source
AI summary
Tunnel insulation layer structures and methods of manufacturing the same are disclosed. The tunnel insulation layer structures may include a first tunnel insulation layer, a second tunnel insulation layer, a third tunnel insulation layer, a fourth tunnel insulation layer and a fifth tunnel insulation layer. The first tunnel insulation layer on a substrate has a first band gap energy. The second tunnel insulation layer on the first tunnel insulation layer has a second band gap energy which is lower than the first band gap energy. The third tunnel insulation layer on the second tunnel insulation layer has a third band gap energy which is higher than the second band gap energy. The fourth tunnel insulation layer on the third tunnel insulation layer has a fourth band gap energy which is lower than the third band gap energy. The fifth tunnel insulation layer on the fourth tunnel insulation layer has a fifth band gap energy which is higher than the fourth band gap energy.