Metal Oxide Interface Dipole for MONOS Memory Endurance
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Solution Overview
Problem
MONOS nonvolatile semiconductor memory devices face reliability issues due to degradation of the tunnel insulating film under repeated write and erase stress, leading to poor data retention characteristics.
Innovation Solution
Incorporating a metal oxide film between the tunnel insulating film and the charge trapping film, made from materials like Al2O3, HfO2, ZrO2, TiO2, or MgO, which generates dipoles and reduces hole injection during erasing, thereby accelerating electron emission and minimizing tunnel insulating film degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MONOS memory structure is used to reduce interference between adjacent cells, then cell isolation is improved, but tunnel insulating film degradation occurs under repeated write and erase stress
Solution Approach 1:
A charge blocking film is introduced as an intermediary layer between the tunnel insulating film and the charge trapping film. This mediator prevents direct interaction between electrons/holes and the tunnel insulating film during erase operations, thereby protecting the tunnel insulating film from degradation while maintaining the MONOS structure's cell isolation benefits
Solution Approach 2:
The gate insulating film stack is segmented into multiple functional layers: tunnel insulating film, charge blocking film, and charge trapping film. Each layer performs a specific function - the tunnel insulating film enables electron injection, the charge blocking film prevents electron back-injection during erase, and the charge trapping film stores charges. This segmentation allows optimization of each layer's properties independently
2Reliability
If high voltage is applied to inject electrons into charge trapping film during writing, then writing capability is achieved, but tunnel insulating film degradation is accelerated
Solution Approach 1:
The charge blocking film acts as a mediator that allows electron injection during write operations while preventing harmful back-injection during erase operations. This selective mediation enables writing capability while protecting the tunnel insulating film from degradation during erase cycles
3Reliability
If reverse bias is applied to gate electrode for erasing, then hole injection into charge trapping film is achieved, but electron back-injection degrades data retention
Solution Approach 1:
The charge blocking film serves as a selective mediator during erase operations - it allows hole injection from the substrate into the charge trapping film while blocking electron back-injection from the charge trapping film to the substrate. This selective permeability enables erasing capability while preserving data retention characteristics
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 endurance of the tunnel insulating film by facilitating electron emission during erasing, reducing degradation and improving data retention characteristics.
Implementation Method 1
a metal oxide exists in an interface between the tunnel insulating film and the charge trapping film
Implementation Method 2
writing is performed by applying a high voltage to the gate electrode to inject and store electrons from the substrate into the charge trapping film via the tunnel insulating film
Implementation Method 3
Erasing is performed by applying a reverse bias to the gate electrode to inject holes from the substrate into the charge trapping film via the tunnel insulating film
Implementation Method 4
electrons and holes stored in the charge trapping film pair-annihilate
Data Source
AI summary
A nonvolatile semiconductor memory apparatus according to an embodiment includes: a semiconductor layer; a first insulating film formed on the semiconductor layer, the first insulating film being a single-layer film containing silicon oxide or silicon oxynitride; a charge trapping film formed on the first insulating film; a second insulating film formed on the charge trapping film; and a control gate electrode formed on the second insulating film. A metal oxide exists in an interface between the first insulating film and the charge trapping film, the metal oxide comprises material which is selected from the group of Al2O3, HfO2, ZrO2, TiO2, and MgO, the material is stoichiometric composition, and the charge trapping film includes material different from the material of the metal oxide.