Non-Volatile Memory Device Buffer Oxide Film Leakage Current
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Solution Overview
Problem
Non-volatile memory devices fabricated on glass substrates experience excessive leakage current due to the rough and non-uniform surfaces of the polysilicon layer, leading to abnormal programming and erasing operations.
Innovation Solution
A SiON layer is formed using nitrous oxide plasma between the polysilicon layer and the ONO stack, moderating the surface roughness, and a fabrication method involving a buffer oxide film, polysilicon layer, SiON layer, insulators, and electrodes is employed to reduce leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polysilicon layer is crystallized by laser irradiation to form a non-volatile memory device on a glass substrate, then the memory device structure is created, but the surface of the polysilicon layer becomes rough and non-uniform, resulting in excessive leakage current
Solution Approach 1:
A buffer oxide film is introduced as an intermediary layer between the glass substrate and the polysilicon layer. This buffer layer absorbs the surface roughness and non-uniformity caused by laser crystallization, providing a smoother interface for the subsequent ONO stack and reducing leakage current while maintaining memory device functionality
Solution Approach 2:
The invention changes the physical and chemical parameters of the interface by forming a buffer oxide film with specific thickness and composition. This parameter modification creates a transition zone that mitigates the harmful effects of surface roughness, enabling the polysilicon layer to maintain its electrical properties while reducing leakage current
2Ease of manufacture
If the polysilicon layer surface is rough and non-uniform, then the memory device can be fabricated, but leakage current increases significantly causing abnormal programming and erasing operations
Solution Approach 1:
The buffer oxide film serves as a mediator that decouples the fabrication process from the performance issue. It allows the polysilicon layer to be formed with laser crystallization (maintaining ease of manufacture) while the buffer layer absorbs the harmful surface roughness effects, preventing excessive leakage current and abnormal operations
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 approach effectively reduces leakage current, allowing the non-volatile memory device to function normally by smoothing the polysilicon surface, thus improving programming and erasing operations.
Implementation Method 1
A SiON layer is formed using nitrous oxide plasma between the polysilicon layer and the ONO stack
Implementation Method 2
The tunneling oxide film may tunnel electrons into a trap region inside the nitride film or a trap region of an interface of the nitride film
Data Source
AI summary
A non-volatile memory device includes a buffer oxide film on a substrate; a polysilicon layer on the buffer oxide film; a silicon oxy-nitride (SiON) layer on the polysilicon layer, a first insulator layer on the SiON layer, a nitride film on the first insulator, a second insulator layer on the nitride film, an electrode on the second insulator, and a source/drain in the polysilicon layer.