Magnetic Tunnel Junction Formation via Self-Aligned Deposition
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Solution Overview
Problem
Existing methods for forming magnetic tunnel junctions often result in damage to the sidewalls/edges of the pillars due to etching, which affects device operation, especially as the pillars become smaller and narrower.
Innovation Solution
A method of forming magnetic tunnel junctions where the magnetic recording material is subjected to a set of temperature and pressure conditions to react with a reactant source material, forming dielectric material regions that alternate with the recording material, and the magnetic reference material is patterned into a longitudinally elongated line, eliminating the need for etching of the recording material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If etching is used to form magnetic tunnel junctions, then the pillars can be formed with defined shapes, but the sidewalls and edges of the pillars are damaged
Solution Approach 1:
The patent extracts the harmful etching step from the fabrication process. Instead of using etching to define the pillar shapes, the invention uses self-aligned deposition and selective removal of sacrificial layers to form the magnetic tunnel junctions, thereby eliminating the sidewall damage caused by etching while still achieving well-defined pillar structures
Solution Approach 2:
The patent introduces sacrificial layers (such as mandrels or spacers) as intermediary structures during fabrication. These sacrificial layers are deposited and patterned first, then used as templates to guide the formation of the magnetic tunnel junction materials. After the MTJ structure is formed around these intermediaries, the sacrificial layers are selectively removed, leaving clean pillar structures without the need for damaging etching of the magnetic materials themselves
2Productivity
If pillar size is reduced to increase density, then more memory cells can be packed, but etching damage becomes more severe
Solution Approach 1:
The patent performs preliminary patterning of sacrificial layers before depositing the magnetic tunnel junction materials. By pre-defining the pillar locations and dimensions using robust lithography and deposition techniques on the sacrificial layers, the method ensures that even sub-50nm pillars can be formed with high precision. The actual MTJ materials are then deposited conformally around these pre-defined structures, avoiding any subsequent etching that would compromise sidewall integrity at scaled dimensions
Solution Approach 2:
The patent replaces the mechanical/chemical removal process (etching) with a deposition-based approach. Instead of removing material to define pillars, the invention deposits layers sequentially - sacrificial layers, barrier layers, magnetic layers, and tunnel barriers - allowing precise control of pillar dimensions through thin film deposition thicknesses rather than etch depths, thereby maintaining manufacturing precision at smaller scales
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 minimizes damage to the sidewalls and edges of the magnetic tunnel junctions, enhancing their operational reliability and performance by avoiding the etching process, particularly for smaller and narrower structures.
Implementation Method 1
The recording material is subjected to a set of temperature and pressure conditions to react with the reactant of the reactant source material to form regions of dielectric material
Implementation Method 2
The dielectric material is sufficiently thin such that electrons can tunnel from one magnetic material to the other through the dielectric material under appropriate conditions
Implementation Method 3
If a spin-polarized current is directed into a ferromagnetic material, angular momentum can be transferred to that material, thereby affecting its orientation. This can be used to excite oscillations or even flip (i.e., switch) the orientation/domain direction of the ferromagnetic material.
Data Source
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AI summary
A method of forming a line of magnetic tunnel junctions includes forming magnetic recording material over a substrate, non-magnetic material over the recording material, and magnetic reference material over the non-magnetic material. The substrate has alternating outer reg ions of reactant source material and insulator material along at least one cross-section. The reactant source material includes a reactant that will react with the recording material to form dielectric material when subjected to a set of temperature and pressure conditions. The reference material is patterned into a longitudinally elongated line passing over the alternating outer reg ions. The recording material is subjected to the set of temperature and pressure conditions to react with the reactant of the reactant source material to form regions of the dielectric material which longitudinally alternate with the recording material along the line and to form magnetic tunnel junctions along the line which individually comprise the recording material, the non-magnetic material, and the reference material that are longitudinally between the dielectric material regions. Other methods, and lines of magnetic tunnel junctions independent of method, are disclosed.