Self-Referenced MRAM Read Using Spin Orbit Active Line
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Solution Overview
Problem
Conventional MRAM read operations require a separate reference cell, leading to increased memory complexity and reduced chip density due to variations in fabrication processes and lead resistances causing overlap of high and low resistance states, resulting in read errors.
Innovation Solution
A self-referenced read operation is performed using a spin orbit active (SO) line to alter the magnetization direction of a reference layer, allowing for the comparison of electrical characteristics without a separate reference cell by passing first and second SO currents through the SO line to reverse the magnetic moment of the reference layer and comparing the magnitudes of read currents or voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate reference cell is added near each memory MTJ to compensate for process variations and lead resistance differences, then read accuracy is improved, but memory complexity increases and chip density decreases
Solution Approach 1:
The patent extracts the reference function from a separate physical reference cell and integrates it into the existing memory cell structure. By using the same MTJ cell for both data storage and reference purposes through sequential read operations, the need for additional reference cells is eliminated, thereby reducing memory complexity and improving chip density while maintaining read accuracy
Solution Approach 2:
The patent makes the memory cell multi-functional by using it for both data storage and reference comparison. The same MTJ cell serves dual purposes: storing information and providing a reference state for comparison during read operations. This eliminates the need for separate reference cells and reduces overall memory structure complexity
2Measurement precision
If a separate reference cell is added near each memory MTJ to compensate for process variations and lead resistance differences, then read accuracy is improved, but chip density decreases
Solution Approach 1:
The patent removes the requirement for separate reference cells by extracting the reference function and integrating it into the existing memory cell. This eliminates additional area requirements for reference cells, thereby improving chip density while maintaining read accuracy through sequential self-referenced read operations
Solution Approach 2:
The patent merges the reference cell function with the existing memory cell structure. By combining data storage and reference comparison functions into a single cell, the overall area required is reduced, improving chip density while maintaining the ability to compensate for process variations and lead resistance differences
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 approach enables accurate determination of stored information without the need for a reference cell, improving read accuracy and memory density by utilizing the SO line to alter the magnetization direction of the reference layer, thereby distinguishing between logic states based on resistance differences.
Implementation Method 1
a spin polarized current is passed through the SO line 30 so as to generate a magnetic moment in the bottom reference layer 28
Implementation Method 2
a spin polarized current is passed through the SO line 30 so as to generate a magnetic moment in the bottom reference layer 28
Implementation Method 3
The differences in magnetic configurations correspond to different magnetoresistances and thus different logical states
Data Source
AI summary
A method of reading information stored in a magnetic memory. In a magnetic memory comprising a magnetic tunnel junction including a first reference layer and a free layer, and a spin orbit active (SO) line adjacent to the first reference layer of the magnetic tunnel junction, first and second currents are passed through the SO line so as to achieve two different directions of a magnetic moment of the first reference layer. Two electrical characteristics of the magnetic tunnel junction are determined, the two electrical characteristics corresponding to the two different directions of the magnetic moment of the first reference layer. These two electrical characteristics are then compared to determine the value of the stored information.