Non-volatile Memory Cell With Dual Access Transistors
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Solution Overview
Problem
Existing resistive memories face reliability issues due to high voltage levels required for programming, which can lead to transistor degradation and complexity in control circuits.
Innovation Solution
A non-volatile memory design featuring a matrix of elementary cells with dual access transistors and a programmable resistor storage element, where the control circuit applies voltages through separate nodes to minimize stress on transistors, allowing for lower voltage operations and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage levels are applied to program the elementary cells, then the resistive memory can be programmed, but transistor degradation occurs and reliability decreases
Solution Approach 1:
The patent divides the voltage application path into separate segments by introducing two independent access transistors (first and second access transistors) that connect to different nodes (first node and second node) of the storage element. This segmentation allows voltage to be applied through separate paths, preventing full voltage stress from concentrating on a single transistor and reducing degradation.
Solution Approach 2:
The patent introduces intermediate nodes (first node and second node) as mediators between the control circuit and the storage element terminals. These intermediate nodes allow voltage distribution and control, enabling the application of programming voltages without directly stressing the transistors with full voltage levels, thus reducing degradation while maintaining programming capability.
2Reliability
If high voltage levels are applied to program the elementary cells, then the resistive memory can be programmed, but control circuit complexity increases
Solution Approach 1:
The control circuit complexity is reduced by segmenting the cell structure into two access transistors with independent control, allowing simpler voltage application schemes. Each transistor can be controlled independently through separate word lines, simplifying the control logic compared to alternative designs that would require more complex voltage switching mechanisms.
Solution Approach 2:
The two access transistors serve multiple functions: they provide independent control paths for programming operations, enable simplified voltage application sequences, and maintain compatibility with standard memory array architectures. This multi-functionality reduces the need for specialized complex control circuits.
3Reliability
If dual access transistors with separate nodes are used, then voltage stress on transistors is minimized, but cell structure complexity increases
Solution Approach 1:
The cell structure uses segmentation of the storage element connections, with the storage element having distinct first and second nodes connected to different access transistors. This segmentation naturally reduces transistor stress while the modular nature of the segmented design makes it compatible with standard fabrication processes, limiting the increase in manufacturing complexity.
Solution Approach 2:
The patent arranges the cell components in a distributed spatial configuration rather than a compact centralized layout. The first and second access transistors are positioned to connect to different nodes of the storage element, creating a more spread-out structure that reduces electrical stress while the regular pattern repeats across the memory array, managing overall fabrication complexity.
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 design simplifies control circuits, reduces transistor degradation, and enhances the reliability and longevity of resistive memory cells by applying voltages within safe limits, thereby overcoming the limitations of traditional resistive memory technologies.
Implementation Method 1
Resistive memories take advantage of the ability of certain materials to change electrical resistivity reversibly and non-volatile under the effect of polarization
Data Source
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AI summary
The invention relates to a non-volatile memory comprising a plurality of elementary cells (300), each cell comprising: a first programmable resistance storage element (101) connected between the first (SL; DL) and second (n) nodes of the cell; a first access transistor (103) connecting the second node (n) to a third node (BL) of the cell; and a second access transistor (305) connecting the second node (n) to a fourth node (DL; SL) of the cell.