Multi-Layered Insulating Film for Semiconductor Data Retention
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Solution Overview
Problem
Current semiconductor devices with non-volatile memories face challenges in improving data retention characteristics and charge injection efficiency due to limitations in the structure and thickness of insulating films in the charge storage portion, leading to suboptimal performance in both data retention and operational efficiency.
Innovation Solution
The semiconductor device employs a multi-layered insulating film structure comprising silicon and oxygen, silicon and nitrogen films, with specific thicknesses and densities to optimize the charge storage portion, including a high-density silicon nitride film as the underlying charge storage film and a lower-density silicon nitride film with higher oxygen concentration as the upper charge storage film, along with a thin oxide film in between, to enhance data retention and charge injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer insulating film is used in the charge storage portion, then the device structure is simple, but data retention characteristics and charge injection efficiency are insufficient
Solution Approach 1:
The insulating film in the charge storage portion is divided into multiple layers (first insulating film, second insulating film, and third insulating film) with different compositions and functions. Each layer contributes differently to charge injection and retention, resolving the contradiction by achieving improved reliability through structured segmentation rather than a simple single-layer approach.
Solution Approach 2:
Different regions of the insulating film structure are assigned different material compositions and properties. The first insulating film contains silicon oxide for charge injection, the second contains silicon nitride for charge storage with trap states, and the third contains silicon oxide for protection. This local differentiation of properties enables simultaneous optimization of charge injection efficiency and data retention characteristics.
2Reliability
If the insulating film thickness is increased to improve charge retention, then data retention improves, but charge injection efficiency decreases
Solution Approach 1:
The total thickness required for charge retention is segmented across multiple layers. The first insulating film (silicon oxide) is made thinner to facilitate charge injection, while the second insulating film (silicon nitride) provides the necessary thickness for charge storage and retention. This segmentation allows each layer to optimize its thickness for its specific function, resolving the contradiction between retention and injection efficiency.
Solution Approach 2:
The material composition parameters are changed across different layers to achieve different electrical properties. The silicon oxide layers provide different characteristics than the silicon nitride layer, allowing the structure to simultaneously achieve thin enough regions for injection and thick enough regions for retention by varying material parameters rather than uniformly increasing thickness.
3Reliability
If high-density silicon nitride film is used for charge storage, then charge retention improves, but electron trap positions increase leading to electron leakage
Solution Approach 1:
The first insulating film (silicon oxide) acts as an intermediary layer between the semiconductor substrate and the high-density silicon nitride charge storage film. This intermediary layer prevents direct interaction that would cause electron leakage into the substrate while still allowing efficient charge injection from the substrate through its lower density region, thus resolving the contradiction between storage capability and leakage prevention.
Solution Approach 2:
The silicon nitride film is positioned specifically in the second insulating film layer where it provides charge storage functionality, while the silicon oxide layers in the first and third positions provide protective and injective functions. This local placement of different material qualities ensures that high-density silicon nitride is used only where charge storage is needed, while electron leakage paths are blocked by the oxide layers.
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 significantly improves data retention characteristics and charge injection efficiency by reducing shallow electron trap positions, preventing electron leakage and allowing for lower write voltages, thereby enhancing the overall performance of the semiconductor device.
Implementation Method 1
an insulating film portion formed on a semiconductor substrate, the insulating film portion including a first insulating film containing silicon and oxygen
Implementation Method 2
a second insulating film that is formed over the first insulating film and contains silicon and nitrogen
Implementation Method 3
a third insulating film that is formed over the second insulating film and contains silicon and oxygen
Data Source
AI summary
To improve the performance of a semiconductor device, the semiconductor device includes an insulating film portion over a semiconductor substrate. The insulating film portion includes an insulating film containing silicon and oxygen, a first charge storage film containing silicon and nitrogen, an insulating film containing silicon and oxygen, a second charge storage film containing silicon and nitrogen, and an insulating film containing silicon and oxygen. The first charge storage film is included by two charge storage films.