Magnetoresistive Memory Cell Cap Layer for Overshoot Current Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current memory devices with magnetoresistive effect elements face challenges in preventing breakdown due to overshoot currents, which can lead to insulation failure and reduced storage density, especially as the size of memory cells decreases to improve storage density.
Innovation Solution
Incorporating a cap layer with a higher electric resistance than the tunnel barrier layer as an internal resistive element within the memory cell, which acts as a built-in resistor to prevent overcurrent flow, and optimizing its thickness to maintain operational stability and reduce the aspect ratio of memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the size of memory cells is decreased to improve storage density, then storage density is improved, but the risk of breakdown due to overshoot currents increases
Solution Approach 1:
A cap layer is introduced as an intermediary element between the upper electrode and the tunnel barrier layer. This cap layer acts as a mediator that limits the current flowing through the magnetoresistive effect element, preventing overshoot currents from causing breakdown while allowing the memory cell size to be reduced for higher storage density.
Solution Approach 2:
The cap layer is designed with specific thickness (1 nm to 3 nm) and material composition to preemptively limit current flow before overshoot currents can develop. By establishing this current-limiting structure in advance, the system prevents breakdown without requiring larger memory cell dimensions.
2Reliability
If a cap layer is added as an internal resistive element to prevent overshoot currents, then reliability is improved, but device complexity increases
Solution Approach 1:
The cap layer is merged with the existing tunnel barrier layer structure, forming an integrated cap layer and tunnel barrier layer composite. This merging approach allows the cap layer to function as both a current-limiting element and part of the magnetoresistive effect element structure, preventing overshoot currents without significantly increasing device complexity.
Solution Approach 2:
The cap layer serves multiple functions: it acts as a current-limiting resistive element to prevent overshoot currents, maintains the structural integrity of the magnetoresistive effect element, and contributes to the overall device performance. This multi-functionality reduces the need for separate protective structures.
3Reliability
If the thickness of the cap layer is increased to improve current limiting, then overshoot current suppression is improved, but the aspect ratio of memory cells increases
Solution Approach 1:
The thickness of the cap layer is optimized to a specific range (1 nm to 3 nm) that provides sufficient current limiting capability while maintaining an acceptable aspect ratio for high-density memory cells. This parameter optimization balances overshoot current suppression with geometric constraints.
Solution Approach 2:
The cap layer is positioned specifically at the interface between the upper electrode and the tunnel barrier layer, where it exerts its current-limiting effect most effectively. This localized placement ensures that the current-limiting function is achieved with minimal impact on the overall memory cell dimensions and aspect ratio.
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 a cap layer as an internal resistive element effectively suppresses overshoot currents, preventing memory cell breakdown and maintaining high storage density without increasing chip size, while also reducing the magnetization switching threshold current.
Implementation Method 1
Incorporating a cap layer with a higher electric resistance than the tunnel barrier layer as an internal resistive element within the memory cell, which acts as a built-in resistor to prevent overcurrent flow
Implementation Method 2
A memory device in which a variable resistive element (e.g., a magnetoresistive effect element) is used as a memory element
Data Source
AI summary
According to one embodiment, a memory device includes a memory cell including a magnetoresistive effect element. The magnetoresistive effect element includes a non-magnetic layer between first and second electrodes in the first direction, a first magnetic layer between the first electrode and the non-magnetic layer, a second magnetic layer between the second electrode and the non-magnetic layer, and a first layer between the second electrode and the second magnetic layer. The first layer includes oxygen and at least one selected from magnesium, transition metal, and lanthanoid, the first layer has a first size in the first direction, the non-magnetic layer has a second size in the first direction. The first size is 1.1 times or more and 2 times or less the second size.