Resistive Memory Cell With NPN Junction And Two-Stage Read Voltage
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Solution Overview
Problem
Magnetic random access memories (MRAMs) with magnetoresistive elements face challenges due to a low resistance change ratio, requiring highly accurate sense amplifiers and increasing the periphery circuit area, making it difficult to dispose these amplifiers in memory circuits effectively.
Innovation Solution
A resistive change memory is developed, incorporating a spin transfer torque magnetic memory with a multilayer structure including a magnetoresistive element and an N-P-N junction element, allowing for a high resistance change rate by applying a two-stage pulsed voltage, which enhances the resistance ratio and simplifies the read/write operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetoresistive elements are used in MRAMs, then nonvolatile data storage and fast write/read time are achieved, but the magnetoresistance change rate is limited to about 600%, requiring highly accurate sense amplifiers that increase periphery circuit area
Solution Approach 1:
The patent combines a magnetoresistive element with a variable resistance element (such as a phase change material or resistive switching material) to create a composite memory structure. This composite structure achieves a resistance change ratio exceeding 10000:1, significantly higher than conventional magnetoresistive elements alone, thereby eliminating the need for complex high-precision sense amplifiers and reducing periphery circuit area.
Solution Approach 2:
The patent utilizes phase change materials that can transition between crystalline and amorphous states, causing dramatic changes in electrical resistance. By controlling the phase state through thermal or electrical stimulation, the memory achieves ultra-high resistance change ratios without requiring high-precision sensing circuits.
2Ease of operation
If magnetoresistive elements with 600% MR ratio are used, then data storage functionality is achieved, but the ratio of high resistance value to low resistance value is insufficient, requiring complex sense amplifiers
Solution Approach 1:
The patent employs a composite structure where a magnetoresistive element is integrated with a variable resistance element. This combination produces a memory cell with resistance change ratio greater than 10000:1, which simplifies the sense amplifier design and reduces overall device complexity while maintaining full data storage functionality.
Solution Approach 2:
The patent divides the memory cell into distinct functional components: a magnetoresistive element for magnetic state control and a variable resistance element for resistance modulation. This segmentation allows each component to perform its specialized function efficiently, resulting in simplified read circuitry and reduced device complexity.
3Productivity
If conventional magnetoresistive elements are used, then basic memory operation is achieved, but the resistance change ratio is limited, making it difficult to dispose sense amplifiers in memory circuits effectively
Solution Approach 1:
The patent creates a composite memory structure with resistance change ratio exceeding 10000:1, which enables highly accurate and rapid data reading. This enhanced performance allows sense amplifiers to be effectively integrated into the memory circuit architecture, improving productivity while reducing the difficulty of circuit disposal and integration.
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 resistive change memory achieves a significantly higher resistance change ratio, reducing the need for complex sense amplifiers and allowing for more efficient memory cell operations with a compact circuit design.
Implementation Method 1
magnetoresistive element having a multilayer structure including a first ferromagnetic layer, a nonmagnetic layer, and a second ferromagnetic layer, wherein a relative direction of magnetization between the first ferromagnetic layer and the second ferromagnetic layer is switchable
Implementation Method 2
spin transfer torque magnetic memory
Data Source
AI summary
A resistive change memory according to an embodiment includes: a memory cell including a resistive change element comprising a first and second terminals, and a semiconductor element, the semiconductor element including a first semiconductor layer of a first conductivity type, a second semiconductor layer of the first conductivity type, and a third semiconductor layer of a second conductivity type that is different from the first conductivity type, the third semiconductor layer being disposed between the first semiconductor layer and the second semiconductor layer, the first semiconductor layer being connected to the second terminal of the resistive change element; and a read unit configured to perform a read operation by applying a first read voltage between the first terminal and the second semiconductor layer, and then applying a second read voltage that is lower than the first read voltage between the first terminal and the second semiconductor layer.