Magnetic Tunnel Junction Device Lateral Trench Segmentation
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Solution Overview
Problem
The manufacturing process of magnetic tunnel junction (MTJ) devices is challenging due to electrical shortcuts between the pinned and free layers, degrading the performance of memory devices, and existing methods require complex etching processes that are difficult to control, especially for thin and sensitive layers.
Innovation Solution
A memory device structure where selector devices are arranged above the second layer, allowing for partial etching and avoiding electrical shortcuts, with the first and second memory elements interconnected via a barrier layer, enabling easier and more robust processing, and allowing for individual access and common node connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex etching processes are used to create MTJ pillars, then memory device performance can be maintained, but manufacturing complexity and difficulty increase significantly
Solution Approach 1:
The patent segments the MTJ structure into distinct layers (pinned layer, tunnel barrier, free layer) that are laterally separated by trenches. This segmentation allows each layer to be processed independently and eliminates the need for complex through-etching processes, as the layers are already physically separated by the trench structures.
Solution Approach 2:
The patent transitions from a vertical stack architecture to a lateral separation architecture by introducing trenches that divide the MTJ layers horizontally. This dimensional change allows the selector device to be positioned above the second layer without requiring complex through-etching, thereby simplifying the manufacturing process while maintaining device functionality.
2Reliability
If through-etching is performed to create separate MTJ pillars, then electrical isolation is achieved, but electrical shortcuts between pinned and free layers occur
Solution Approach 1:
The patent uses trenches to laterally segment and isolate the pinned layer and free layer, achieving electrical isolation without requiring precise through-etching. The trenches act as physical barriers that prevent electrical shortcuts while being easier to manufacture than precise through-etches through thin sensitive layers.
Solution Approach 2:
The trench structure serves as an intermediary element that provides electrical isolation between the pinned and free layers. Instead of relying on precise etching to create isolation, the trench acts as a mediator that physically separates the conductive layers, eliminating the risk of electrical shortcuts.
3Area of stationary object
If selector devices are arranged in the substrate, then area efficiency is improved, but manufacturing robustness decreases due to sensitive layer exposure
Solution Approach 1:
The patent positions the selector device in a different vertical dimension (above the second layer) rather than in the substrate plane. This dimensional relocation allows the selector device to contact the MTJ stack without requiring complex through-etching processes, thereby improving manufacturing robustness while maintaining area efficiency through the lateral trench separation.
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 improves the manufacturing process by reducing electrical shortcuts, enhancing etch uniformity, and enabling efficient, area-efficient memory device architecture with improved selector device placement, allowing for better control and reduced complexity in the etching process.
Implementation Method 1
If the insulating layer is thin enough, typically a few nanometers, electrons can tunnel from one ferromagnetic layer into the other. The resistance of the MTJ is dependent on the relative orientation of the magnetization of the two ferromagnetic layers. This mechanism is known as tunnel magnetoresistance (TMR).
Implementation Method 2
The writing operation can be achieved by the spin-torque transfer (STT), representing a transfer of spin angular momentum from a reference FM layer to a free FM layer of the MTJ.
Data Source
AI summary
A magnetic tunnel junction memory device is disclosed. In one aspect, the memory device comprises a substrate, a first memory element, and a second memory element, wherein the first memory element and the second memory element are formed of a stack comprising at least a first layer and a second layer, the first layer being arranged between the substrate and the second layer. The memory device further comprises a first selector device arranged to contact the first memory element, and a second selector device arranged to contact the second memory element, wherein the first selector device and the second selector device are arranged in or above the second layer. The first memory element and the second memory element are interconnected via the first layer, and are separated from each other by a trench formed in the second layer.