Nonvolatile Memory FN Tunneling Electric Field Concentration
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Solution Overview
Problem
The Channel Hot Electron (CHE) method for electron injection in charge-trapping nonvolatile semiconductor memories requires a large amount of current, leading to increased current consumption and larger element sizes, while the Fowler-Nordheim (FN) tunneling method has higher breakdown voltages and inefficiencies in electron injection.
Innovation Solution
The use of an electric field concentration between a second gate electrode and a charge trapping film, facilitated by a tunnel insulating film, enables efficient electron injection through FN tunneling, reducing the required applied voltage and element size, and minimizing current consumption by replacing the CHE method with FN tunneling for electron injection and ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the CHE method is used for electron injection, then electron injection can be achieved, but a large amount of current is required leading to increased current consumption and larger element sizes
Solution Approach 1:
The patent changes the fundamental parameter of the electron injection mechanism from CHE (channel hot electron) method to FN tunneling (Fowler-Nordheim tunneling) method. This parameter change transforms the injection process from a high-current conduction-based mechanism to a quantum tunneling mechanism, thereby reducing current consumption while achieving efficient electron injection into the charge trapping film
Solution Approach 2:
The patent replaces the mechanical/electrical conduction-based CHE method with a quantum mechanical tunneling effect (FN tunneling). By substituting the injection mechanism from classical electron flow through a conducting channel to quantum tunneling through a potential barrier, the system achieves lower current consumption and improved injection efficiency
2Ease of operation
If the FN tunneling method is used for electron ejection, then electron ejection can be achieved, but a high breakdown voltage is required leading to larger element sizes
Solution Approach 1:
The patent applies local quality by creating a convex portion specifically at the drain side of the channel region. This localized geometric modification concentrates the electric field at a specific location (the convex section), enabling efficient FN tunneling electron ejection without requiring high breakdown voltage across the entire device structure, thereby reducing element size
Solution Approach 2:
The patent introduces a convex (curved) portion in the channel region at the drain side. This curvature modification creates an electric field concentration point, enhancing the local electric field strength to facilitate FN tunneling electron ejection without requiring high overall breakdown voltage, thus reducing element size while maintaining ejection capability
3Power
If a convex section is formed in the channel region to concentrate electric field, then voltage at programming/erasing can be reduced, but device structure becomes more complex
Solution Approach 1:
The patent forms a convex portion in the channel region at the drain side, using geometric curvature to concentrate the electric field. This simple shape modification achieves electric field enhancement that reduces programming and erasing voltages without significantly complicating the device structure, as the convex portion can be integrated into existing fabrication processes
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 electron injection efficiency, reduces current consumption, and suppresses the increase in element size, improving programming and erasing speeds while maintaining data retention characteristics.
Implementation Method 1
The tunnel insulating film is formed between the charge trapping film and the second gate electrode. The use of an electric field concentration between a second gate electrode and a charge trapping film, facilitated by a tunnel insulating film, enables efficient electron injection through FN tunneling
Implementation Method 2
The silicon nitride film in the ONO film has a property of trapping charges. For example, it is possible to inject electrons into the silicon nitride film by applying appropriate voltages respectively to a gate electrode, source/drain and a substrate
Implementation Method 3
a surface of a channel region of a MNOS transistor is formed to be convex. When a voltage is applied between a gate electrode and the channel region, an electric field is intensified at the convex section
Data Source
AI summary
A nonvolatile semiconductor memory comprises: a semiconductor substrate; a first gate electrode formed on a surface of the semiconductor substrate through a first gate insulating film; a second gate electrode formed on the surface of the semiconductor substrate through a second gate insulating film and being adjacent to the first gate electrode through an insulating film; a charge trapping film formed at least in a trap region surrounded by the semiconductor substrate, the first gate electrode and the second gate electrode; and a tunnel insulating film formed between the charge trapping film and the second gate electrode. In one of programming and erasing, electrons are injected into the charge trapping film from the second gate electrode through the tunnel insulating film by Fowler-Nordheim tunneling.