Gettering Layer for STMRAM Tunnel Barrier Protection
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Solution Overview
Problem
In spin-transfer MRAM (STMRAM) devices, the tunnel barrier layer's active area is often reduced due to high-temperature processing, leading to increased switching voltage and reduced reliability, as oxygen or nitrogen from adjacent insulating layers diffuse into the tunnel barrier, altering its resistance and active area.
Innovation Solution
A gettering layer capable of getting oxygen is formed adjacent to the magnetic stack, including under-oxidized metal, to prevent further oxidation during subsequent processing, maintaining the tunnel barrier's active area and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high-temperature processing is performed to deposit insulating layers, then the insulating layer formation is achieved, but oxygen diffuses into the tunnel barrier layer reducing its active area and increasing resistance
Solution Approach 1:
A gettering layer is deposited adjacent to the magnetic tunnel junction before depositing the insulating layer. This gettering layer is capable of absorbing oxygen and other reactive species that would otherwise diffuse into the tunnel barrier layer during subsequent high-temperature processing steps, thereby preserving the tunnel barrier's active area and electrical properties
Solution Approach 2:
The gettering layer acts as an intermediary between the insulating layer and the magnetic tunnel junction. It absorbs oxygen and reactive species from the insulating layer deposition process, preventing these harmful elements from reaching and degrading the tunnel barrier layer while allowing the insulating layer to be successfully formed
2Reliability
If the tunnel barrier active area is reduced by oxygen diffusion, then the resistance area product increases, but the switching voltage increases and reliability decreases
Solution Approach 1:
The gettering layer is prepared in advance before the insulating layer deposition, creating a protective barrier that will absorb oxygen and reactive species during subsequent processing, thereby preventing degradation of the tunnel barrier's resistance properties and maintaining reliable STMRAM operation
Solution Approach 2:
The potentially harmful oxygen and reactive species that would normally diffuse into and degrade the tunnel barrier are instead captured and absorbed by the gettering layer. This converts a harmful effect (oxygen diffusion causing resistance increase) into a beneficial outcome (oxygen absorption by gettering layer protecting the tunnel barrier)
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 gettering layer effectively reduces process-induced variations in resistance, preserving the as-deposited electrical properties of the tunnel barrier layer, thereby maintaining the active area and ensuring reliable STMRAM operation.
Implementation Method 1
forming a gettering layer, capable of gettering oxygen, adjacent to a magnetic stack including a tunnel barrier layer
Implementation Method 2
Oxygen (or nitrogen) may diffuse from the insulating layer into the edges of the tunnel barrier layer, locally increasing its RA product
Data Source
AI summary
A process of forming an electronic device can include forming a stack including a tunnel barrier layer. The tunnel barrier layer can have a ratio of the metal atoms to oxygen atoms of greater than a stoichiometric ratio, wherein the ratio has a particular value. The process can also include forming a gettering layer having a composition capable of gettering oxygen, and depositing an insulating layer over the gettering layer. The process can further include exposing the insulating layer to a temperature of at least approximately 60° C. In one embodiment, after such exposure, a portion of the gettering layer is converted to an insulating material. In another embodiment, an electronic device can include a magnetic tunnel junction and an adjacent insulating layer lying within an opening in another insulating layer.