Carbon Nanotube Nonvolatile Memory Cell Structure
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Solution Overview
Problem
NAND flash memories face limitations in characteristics uniformity, reliability, operating speed, and integration density due to their transistor-based operation, while phase change and resistance change memory elements, which do not require transistor operation, offer potential for further improvements in these areas.
Innovation Solution
A nonvolatile memory device with a memory cell structure that includes a carbon nanotube-containing layer in contact with a resistance change film, allowing for reversible resistance transitions between states for data storage, and a method for manufacturing this device by forming a carbon nanotube layer and a memory layer, enabling efficient data writing and erasure operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistor-based operation is used in NAND flash memory, then data storage function is achieved, but characteristics uniformity, reliability, and operating speed are limited
Solution Approach 1:
The patent extracts the transistor component from the memory cell structure, eliminating the need for transistor operation. The memory cell consists directly of a resistance change film sandwiched between two electrodes, removing the transistor gate conductor and associated control structures that limit reliability and increase complexity.
Solution Approach 2:
The patent replaces the transistor-based electrical control mechanism with a direct resistance change mechanism. Instead of using transistor threshold variation through gate voltage control, the invention uses reversible resistance transitions in the resistance change film between two electrodes for direct data storage and retrieval.
2Quantity of substance
If further downscaling of NAND flash memory is pursued, then integration density increases, but characteristics uniformity and reliability deteriorate
Solution Approach 1:
By removing the transistor structure and keeping only the essential resistance change film and electrodes, the patent achieves simpler downscaling. The reduced structure eliminates multiple interfaces and components that cause variability, allowing for better characteristics uniformity at higher integration densities.
3Productivity
If phase change or resistance change memory elements are used, then transistor operation is eliminated, but manufacturing process complexity increases
Solution Approach 1:
The resistance change film inherently provides both data storage and switching functions through its reversible resistance transitions. The material self-manages the memory operation without requiring external transistor control, simplifying the overall cell structure while maintaining fast operation.
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 use of carbon nanotubes in the memory cell structure enhances memory density, reduces power consumption, and improves process margins, leading to lower manufacturing costs and increased reliability compared to traditional NAND flash memory technologies.
Implementation Method 1
the other end of at least one carbon nanotube is in contact with the memory layer and the first interconnection
Implementation Method 2
allows for reversible resistance transitions between states for data storage
Data Source
AI summary
According to one embodiment, a nonvolatile memory device includes a memory cell. The memory cell is connected to a first interconnection and a second interconnection and includes a plurality of layers. The plurality of layers includes a memory layer and a carbon nanotube-containing layer which is in contact with the memory layer and contains a plurality of carbon nanotubes.