Dual-Layer Charge Blocking in Nonvolatile Memory Fabrication
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Solution Overview
Problem
Conventional charge-trapping type nonvolatile memory devices face issues with the formation of metal oxide charge blocking layers, which can lead to deterioration of threshold voltage window characteristics due to potential oxidation of layers, resulting in reduced integration density and increased leakage current.
Innovation Solution
A method of fabricating nonvolatile memory devices involves forming two charge blocking layers with different oxidizing powers, where the first layer is formed using a weak oxidizing gas like water vapor and the second layer using a stronger oxidizing gas like ozone, to minimize oxidation of the charge trapping layer and enhance the threshold voltage window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a metal oxide charge blocking layer is formed using a strong oxidizing gas like ozone, then the oxidation capability is improved, but the charge trapping layer may be oxidized, deteriorating threshold voltage window characteristics
Solution Approach 1:
The charge blocking layer is divided into multiple sub-layers with different oxidation capabilities. The first charge blocking layer uses a weak oxidizing gas to minimize charge trapping layer oxidation, while the second charge blocking layer uses a strong oxidizing gas like ozone to achieve complete oxidation and reduce leakage current. This segmentation allows each layer to perform its specific function without compromising the other.
Solution Approach 2:
Different regions of the charge blocking layer are formed with different oxidation characteristics. The first charge blocking layer adjacent to the charge trapping layer has weak oxidation properties to protect the trapping layer, while the second charge blocking layer has strong oxidation properties to ensure complete oxidation and reduce leakage. This local differentiation of oxidation quality resolves the contradiction between oxidation capability and charge trapping layer protection.
2Productivity
If the charge blocking layer thickness is reduced to improve high density integration, then integration density is improved, but leakage current increases
Solution Approach 1:
The charge blocking layer is constructed as a composite structure with two distinct sub-layers having different oxidation characteristics. This composite approach allows the first layer to protect the charge trapping layer while the second layer provides strong oxidation to reduce leakage current, achieving both high integration density and low leakage current through material composition rather than simply increasing total thickness.
3Reliability
If oxidizing gas is supplied to form metal oxide charge blocking layer, then charge blocking capability is improved, but oxidation of charge trapping layer occurs, increasing leakage current
Solution Approach 1:
The first charge blocking layer acts as an intermediary between the charge trapping layer and the strong oxidizing environment of the second charge blocking layer. This intermediate layer with weak oxidation capability protects the charge trapping layer from direct exposure to strong oxidizing gases, preventing unwanted oxidation while still allowing the second layer to achieve complete oxidation for reduced leakage current.
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 results in improved threshold voltage window characteristics, increasing memory storage capacity and reliability by preventing oxidation of the charge trapping layer, thereby enhancing the overall performance of the nonvolatile memory device.
Implementation Method 1
forming a first charge blocking layer on the charge trapping layer by supplying a metal source gas and a first oxidizing gas onto the charge trapping layer
Implementation Method 2
forming a second charge blocking layer on the first charge blocking layer by supplying a metal source gas and a second oxidizing gas onto the first charge blocking layer
Data Source
AI summary
A method of fabricating a nonvolatile memory device includes forming a charge tunneling layer on a semiconductor substrate, forming a charge trapping layer on the charge tunneling layer, forming a first charge blocking layer on the charge trapping layer by supplying a metal source gas and a first oxidizing gas onto the charge trapping layer, forming a second charge blocking layer on the first charge blocking layer by supplying a metal source gas and a second oxidizing gas onto the first charge blocking layer, wherein the second oxidizing gas has a higher oxidizing power as compared to the first oxidizing gas, and forming a gate electrode layer on the second charge blocking layer.