Parallel Selector Devices for Resistive Memory Reliability
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Solution Overview
Problem
Existing resistive memory technologies face challenges in achieving high scalability, density, and reliability, particularly in 3D integration, due to limitations in selector devices which suffer from reduced lifetime and reliability under repeated read and write operations.
Innovation Solution
A selector device comprising two selector devices connected in parallel, where the first selector device is optimized for reading with a lower threshold voltage and the second selector device is optimized for writing with a higher threshold voltage, allowing for distributed read/write cycles and reduced deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single selector device is used for both reading and writing operations, then the device structure is simple, but the selector device suffers from reduced lifetime and reliability under repeated read and write operations
Solution Approach 1:
The patent divides the selector device into two separate selector devices (first selector device and second selector device) that operate in parallel. The first selector device is dedicated to reading operations while the second selector device handles writing operations. This segmentation allows each selector device to be optimized for its specific function, thereby improving overall reliability and lifetime by preventing the degradation that occurs when a single device performs both read and write cycles.
2Device complexity
If a single selector device is used for both reading and writing operations, then the device structure is simple, but the energy consumption is high due to repeated high-current writing operations
Solution Approach 1:
The patent segments the selector functionality into two dedicated devices where the first selector device handles low-current reading operations and the second selector device handles high-current writing operations. This segmentation ensures that high-current writing operations do not repeatedly stress the reading pathway, thereby reducing overall energy consumption and preventing the mixing of high and low current operations in a single device.
3Adaptability or versatility
If diode type selectors are used for 3D integration, then the structure is suitable for 3D integration, but the current in the ON state is too low to efficiently program the resistive memory
Solution Approach 1:
The patent merges two different types of selector devices in parallel: a first selector device optimized for low current reading and a second selector device optimized for high current writing operations. This combination allows the system to achieve both 3D integration compatibility and sufficient programming current by utilizing the second selector device's high-current capability specifically for writing operations, while the first selector device maintains the low-current reading function.
4Adaptability or versatility
If backend type diodes are used as selectors, then the structure is suitable for 3D integration, but the series resistance is very high and variable
Solution Approach 1:
The patent combines two selector devices in parallel where the first selector device provides a stable, low series resistance path for reading operations, while the second selector device provides the high-current capability for writing operations. This merging allows the system to overcome the high and variable series resistance problem of backend diodes by using the first selector device's stable resistance characteristics for reading, thereby achieving both 3D integration compatibility and controlled series resistance.
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 solution enhances the lifetime and reliability of resistive memory devices by isolating the high-current writing operation to the second selector device, while using the first selector device for low-current reading operations, thus reducing energy consumption and extending device lifespan.
Implementation Method 1
a first selector device configured to provide an electric current suitable for reading a state of the resistive memory cell
Implementation Method 2
a second selector device configured to provide an electric current suitable for writing a state of the resistive memory cell
Implementation Method 3
a resistive memory cell having a first highly resistive state or OFF state or RESET state and a second low resistive state or ON state or SET state
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A selector device (S) for selecting a resistive memory cell (RC) comprises a first selector device (S1) including a first active material (105) and a second selector device (S2) including a second active material (108), the first selector device (S1) and the second selector device (S2) being connected in parallel. In particular, the first selector device (S1), for example of the diode type, is configured to supply an electrical current suitable for reading a state of the resistive memory cell, and the second selector device (S2), for example of the oval threshold switch type, is configured to supply an electrical current suitable for writing a state of the resistive memory cell.