Segmented Charge-Trapping Material for NAND Memory Data Retention
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Solution Overview
Problem
Conventional NAND memory architectures face data retention issues due to charge migration between memory cells caused by charge-trapping material extending across multiple cells, leading to inefficiencies in charge storage and retrieval.
Innovation Solution
The implementation of NAND architectures with breaks in the charge-trapping material, configured as vertically-spaced segments, and the use of nitrogen-containing tunneling material like silicon nitride or silicon oxynitride to prevent charge migration between cells, with the tunneling material wrapping partially around the segments to enhance charge storage and retrieval processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If charge-trapping material extends across multiple memory cells, then charge storage capacity is increased, but charge migration between cells occurs causing data retention issues
Solution Approach 1:
The charge-trapping material is divided into vertically-spaced segments rather than forming a continuous layer. This segmentation is achieved by selectively removing portions of the charge-trapping material between memory cell tiers, creating isolated regions that prevent charge migration while maintaining storage capacity across multiple tiers.
Solution Approach 2:
Portions of the charge-trapping material are selectively removed (taken out) from between adjacent memory cell tiers. This extraction creates breaks in the charge-trapping material that prevent charge migration pathways between cells while preserving the charge-trapping functionality within each tier.
2Reliability
If charge-trapping material is segmented vertically, then charge migration is prevented, but manufacturing complexity increases
Solution Approach 1:
A sacrificial material is deposited over the charge-trapping material before the charge-trapping material is removed. This preliminary action of placing the sacrificial material simplifies the subsequent selective removal process by providing a protective layer that enables precise patterning and removal of charge-trapping material segments.
Solution Approach 2:
A sacrificial material is used as an intermediary layer during the manufacturing process. This sacrificial material facilitates the selective removal of charge-trapping material by serving as a temporary protective and guiding layer that is later removed, leaving the desired segmented charge-trapping structure.
3Reliability
If nitrogen-containing tunneling material is used, then charge transfer control is improved, but material deposition complexity increases
Solution Approach 1:
The tunneling material is formed as a composite structure containing nitrogen (such as silicon nitride or silicon oxynitride) combined with other materials. This composite material approach provides the desired charge transfer control properties while utilizing established deposition techniques for multiple material layers.
Solution Approach 2:
The composition and properties of the tunneling material are adjusted by incorporating nitrogen at specific concentrations and configurations. This parameter change in material composition enables controlled charge transfer while utilizing standard deposition processes that can accommodate compositional variations.
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 effectively impedes charge migration between memory cells, improving data retention and storage efficiency by isolating charge-trapping segments and utilizing nitrogen-containing tunneling materials to facilitate controlled charge transfer.
Implementation Method 1
nitrogen-containing tunneling material like silicon nitride or silicon oxynitride to prevent charge migration between cells
Implementation Method 2
tunneling material is formed to extend vertically along the first and second levels
Data Source
AI summary
Some embodiments include a memory array having a vertical stack of alternating insulative levels and wordline levels. The wordline levels include conductive wordline material having terminal ends. Charge blocking material is along the terminal ends of the conductive wordline material and has first vertical faces. The insulative levels have terminal ends with second vertical faces. The second vertical faces are laterally offset relative to the first vertical faces. Charge-trapping material is along the first vertical faces, and extends partially along the second vertical faces. The charge-trapping material is configured as segments which are vertically spaced from one another by gaps. Charge-tunneling material extends along the segments of the charge-trapping material. Channel material extends vertically along the stack, and is spaced from the charge-trapping material by the charge-tunneling material. The channel material extends into the gaps. Some embodiments include methods of forming integrated assemblies.