Magnetic Tunnel Junctions With Temperature-Controlled PVD
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Solution Overview
Problem
Magnetic tunnel junction (MTJ) stacks used in STT-MRAMs face challenges with synthetic anti-ferrimagnetic coupling being lost after high-temperature processing, necessitating an improved MTJ stack that can withstand processing temperatures above 400°C.
Innovation Solution
The method involves varying the substrate temperature during the deposition of MTJ stack layers using physical vapor deposition (PVD) to promote desired lattice structures and lattice matching, allowing the MTJ stack to maintain robust magnetic and electrical properties even after annealing at 400°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PVD deposition is used at standard temperatures, then the MTJ stack can be fabricated with basic structural integrity, but the synthetic anti-ferrimagnetic coupling is lost after high-temperature processing
Solution Approach 1:
The patent applies parameter changes by controlling substrate temperature during PVD deposition to form specific lattice structures. The substrate is heated to temperatures between 200-400°C during deposition of certain layers, which promotes formation of thermally stable lattice structures that maintain synthetic anti-ferrimagnetic coupling after high-temperature processing. This temperature parameter control during fabrication creates the thermal stability needed to resolve the contradiction.
Solution Approach 2:
The patent uses composite material structures with specific lattice configurations deposited at controlled temperatures. By creating composite layer structures with optimized lattice matching through temperature-controlled PVD, the synthetic anti-ferrimagnetic coupling becomes resistant to high-temperature processing. The composite nature of the multi-layer structure with specific lattice orientations provides the thermal stability required.
2Manufacturing precision
If high substrate temperature is used during PVD deposition, then desired lattice structures and lattice matching are promoted, but deposition process complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-heating the substrate to specific temperatures before and during PVD deposition. This preliminary temperature preparation ensures that the desired lattice structures form correctly during deposition, improving lattice matching quality. By preparing the substrate in advance with the appropriate thermal state, the process achieves high precision without requiring complex in-situ temperature modulation during deposition.
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 results in an MTJ stack with improved lattice matching and robust magnetic and electrical properties, enabling it to withstand high-temperature processing without loss of synthetic anti-ferrimagnetic coupling.
Implementation Method 1
depositing, via physical vapor deposition (PVD), a buffer layer on a substrate
Implementation Method 2
The moments of the first pinning layer and the second pinning layer is coupled through the SyF coupling layer by interlayer exchange coupling effect
Data Source
AI summary
Embodiments of the present disclosure are for systems and methods for fabrication of a magnetic tunnel junction stack. This fabrication can occur via methods including one or more of (1) heating the substrate after the deposition of a buffer layer on the substrate, prior to deposition of a seed layer; (2) cooling the substrate after the deposition of a second pinning layer, before deposition of a structure blocking layer; (3) heating the substrate during the deposition of a tunnel barrier layer and then cooling it after the deposition of the tunnel barrier layer is complete; (4) heating the substrate after the deposition of a magnetic storage layer on the tunnel barrier layer; and (5) cooling the substrate after the deposition of the magnetic storage layer before a first interlayer of the capping layer is deposited.