Lanthanum Oxide Gate Insulator Stability in Flash Memory
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Solution Overview
Problem
The use of lanthanum oxide and lanthanum oxynitride as second gate insulating films in NAND flash memory devices leads to degradation of insulating performance due to moisture and carbon dioxide absorption, and interfacial reactions with silicon-based charge storage layers, causing shape changes and dopant diffusion.
Innovation Solution
Employing a second gate insulating film composed of lanthanum oxide or lanthanum oxynitride with aluminum and silicon, in conjunction with a silicon-based charge storage layer, where the composition ratio and heat treatment help maintain the amorphous state and chemical stability, preventing interfacial reactions and maintaining high insulating performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lanthanum oxide or lanthanum oxynitride is used as the second gate insulating film to achieve high dielectric constant, then the insulating performance is improved, but the film absorbs water and carbon dioxide causing degradation of insulating performance
Solution Approach 1:
A silicon-containing layer is introduced between the charge storage layer and the lanthanum oxide/lanthanum oxynitride second gate insulating film. This intermediary layer prevents direct contact and reaction between the silicon-based charge storage layer and the lanthanum-based insulating film, while also reducing moisture and carbon dioxide absorption. The silicon-containing layer acts as a protective barrier that maintains the high dielectric constant properties of the lanthanum-based film while eliminating its harmful interactions.
2Reliability
If lanthanum oxide or lanthanum oxynitride is used as the second gate insulating film, then high dielectric constant is achieved, but interfacial reactions with silicon-based charge storage layer cause shape changes and dopant diffusion
Solution Approach 1:
The silicon-containing layer serves as a chemical buffer between the silicon-based charge storage layer and the lanthanum-based second gate insulating film. This intermediary prevents direct chemical reactions at the interface, eliminating shape changes and dopant diffusion that would otherwise occur. The layer maintains chemical stability while allowing the high dielectric constant properties of the lanthanum-based film to be utilized.
3Object-affected harmful factors
If aluminum and silicon are added to lanthanum oxide or lanthanum oxynitride to improve chemical stability, then resistance to moisture and carbon dioxide absorption is enhanced, but the composition complexity increases
Solution Approach 1:
The composition of the second gate insulating film is modified by incorporating aluminum and silicon into the lanthanum oxide or lanthanum oxynitride matrix. This parameter change transforms the material properties to achieve resistance against moisture and carbon dioxide absorption. The multi-element composition creates a more stable and resistant insulating film while maintaining the high dielectric constant necessary for device performance.
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 enhances electron capture efficiency, suppresses back tunneling current, and maintains insulating performance even at high temperatures, while preventing chemical instability and capacitive coupling issues.
Implementation Method 1
Lanthanum oxide and lanthanum oxynitride have the property of easily absorbing water and carbon dioxide
Implementation Method 2
the composition ratio and heat treatment help maintain the amorphous state and chemical stability
Data Source
AI summary
According to one embodiment, a nonvolatile semiconductor memory device includes a semiconductor substrate, a first gate insulating film, a charge storage layer, a second gate insulating film, and a control gate electrode. The first gate insulating film is arranged on the semiconductor substrate. The charge storage layer is arranged on the first gate insulating film, and includes aluminum and silicon. The second gate insulating film is arranged on the charge storage layer, and includes aluminum, silicon, and lanthanum. The control gate electrode is arranged on the second gate insulating film.