Silicon Nitride Charge Trapping Layer Heat Treatment
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Solution Overview
Problem
Conventional non-volatile memory devices face issues with data retention performance and reliability due to defect sites in silicon nitride charge trapping layers, which lead to lateral charge diffusion and a decreased threshold voltage window, especially when using multi-level cell configurations.
Innovation Solution
A method of manufacturing non-volatile memory devices involves forming a tunnel insulating layer and a charge trapping layer with silicon nitride, followed by a heat treatment using a gas mixture of nitrogen and oxygen to densify and remove defects, preventing the formation of unwanted material layers and enhancing the dielectric constant of the tunnel insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride layer is used as the charge trapping layer, then the non-volatile memory device can store data, but defect sites such as silicon dangling bonds and silicon hydrogen bonds cause lateral charge diffusion, deteriorating data retention performance and reliability
Solution Approach 1:
A heat treatment process is performed on the silicon nitride charge trapping layer before forming the blocking layer to remove defect sites such as silicon dangling bonds and silicon hydrogen bonds in advance. This preliminary action prevents lateral charge diffusion that would otherwise occur during subsequent manufacturing steps and device operation, thereby improving data retention performance and reliability.
2Reliability
If a metal oxide layer with higher dielectric constant than silicon nitride is used as the blocking layer, then the threshold voltage window can be increased, but an unwanted aluminum silicon oxynitride layer forms between the silicon nitride charge trapping layer and aluminum oxide blocking layer, decreasing the threshold voltage window
Solution Approach 1:
The heat treatment process is performed on the silicon nitride charge trapping layer before depositing the aluminum oxide blocking layer. This preliminary treatment removes defect sites and prevents the formation of unwanted aluminum silicon oxynitride layers during the subsequent aluminum oxide deposition process, thereby maintaining the intended threshold voltage window.
Solution Approach 2:
The heat treatment process applies counter-action in advance to prevent the harmful interaction between aluminum oxide and silicon nitride that would otherwise create unwanted aluminum silicon oxynitride layers. By treating the silicon nitride layer first, the patent prevents the formation of these unwanted material layers that would decrease the threshold voltage window.
3Ease of manufacture
If the charge trapping layer is not heat treated, then the manufacturing process is simpler, but defect sites remain causing lateral charge diffusion and decreased threshold voltage window
Solution Approach 1:
The heat treatment process changes the physical and chemical parameters of the silicon nitride charge trapping layer by heating it to a specific temperature range. This parameter change removes defect sites and densifies the layer, improving manufacturing precision regarding the threshold voltage window while adding a controlled step to the manufacturing process.
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 heat treatment process improves data retention performance and reliability by reducing hydrogen concentrations, increasing oxygen concentrations, and preventing the formation of unwanted layers, thereby enhancing the threshold voltage window and maintaining data integrity under thermal and electrical stress.
Implementation Method 1
A heat treatment may be performed using a first gas, including nitrogen, and a second gas, including oxygen, to remove defect sites in the charge trapping layer and/or to densify the charge trapping layer
Implementation Method 2
data may be electrically stored, e.g., programmed and/or erased through a Fowler-Nordheim (F-N) tunneling mechanism
Implementation Method 3
A heat treatment may be performed using a first gas, including nitrogen, and a second gas, including oxygen, to remove defect sites in the charge trapping layer
Data Source
AI summary
In a method of manufacturing a non-volatile memory device, a tunnel insulating layer may be formed on a channel region of a substrate. A charge trapping layer including silicon nitride may be formed on the tunnel insulating layer to trap electrons from the channel region. A heat treatment may be performed using a first gas including nitrogen and a second gas including oxygen to remove defect sites in the charge trapping layer and to densify the charge trapping layer. A blocking layer may be formed on the heat-treated charge trapping layer, and a conductive layer may then formed on the blocking layer. The blocking layer, the conductive layer, the heat-treated charge trapping layer and the tunnel insulating layer may be patterned to form a gate structure on the channel region. Accordingly, data retention performance and/or reliability of a non-volatile memory device including the gate structure may be improved.