STT-MRAM Fixed Layer Using CoW/Pt Bilayers for PMA

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Solution Overview

Problem

Conventional techniques for enhancing perpendicular magnetic anisotropy (PMA) in spin transfer torque magnetic random access memory (STT-MRAM) structures compromise thermal endurance and thermal budget, and are not cost-effective or compatible with logic processing.

Innovation Solution

The use of anti-parallel layers including cobalt tungsten/platinum (CoW/Pt) or cobalt molybdenum/platinum (CoMo/Pt) bilayers, or combinations of cobalt, tungsten, molybdenum, platinum, palladium, and iridium in the fixed layer of STT-MRAM structures, along with a magnetic tunnel junction (MTJ) element with perpendicular orientation, to improve PMA and thermal endurance while being compatible with CMOS processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional techniques are used to enhance perpendicular magnetic anisotropy (PMA), then PMA is improved, but thermal endurance and thermal budget are reduced

Engineering Contradiction:

Improveperpendicular magnetic anisotropyVSAvoidthermal endurance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent employs composite material structures including CoFeB/MgO/CoFeB magnetic tunnel junctions combined with Ru/Ir/Ru superlattice layers and CoFeB capping layers. This multi-material composite approach achieves strong perpendicular magnetic anisotropy while maintaining thermal stability, resolving the contradiction between PMA enhancement and thermal endurance preservation

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes specific parameter values including MgO barrier thickness (0.8-1.2 nm), CoFeB layer thicknesses (3-5 nm), and Ru/Ir layer thicknesses (0.5-2 nm each). These precise parameter adjustments enable achievement of high PMA with improved thermal budget and endurance compared to conventional structures

Inventive Principle:

Principle #35Parameter changes

2Strength

If conventional techniques are used to enhance PMA, then PMA is improved, but manufacturing cost increases and compatibility with logic processing decreases

Engineering Contradiction:

Improveperpendicular magnetic anisotropyVSAvoidcompatibility with logic processing

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent designs a multi-functional stack structure where the Ru/Ir/Ru superlattice layers serve multiple purposes: providing perpendicular magnetic anisotropy, acting as diffusion barriers, and maintaining compatibility with standard CMOS fabrication processes. The CoFeB/MgO/CoFeB structure similarly provides both magnetic functionality and process compatibility, enabling integration with logic processing

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent employs parameter optimization within ranges compatible with existing CMOS manufacturing capabilities, such as using deposition temperatures and thicknesses that can be achieved with standard equipment, thereby improving ease of manufacture while maintaining high PMA

Inventive Principle:

Principle #35Parameter changes

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 enhances PMA and thermal endurance of STT-MRAM structures, maintaining compatibility with logic processing and reducing costs, thereby improving the thermal budget and stability of the memory cells.

Implementation Method 1

In order to obtain strong perpendicular magnetic anisotropy (PMA), a robust synthetic antiferromagnetic (SAF) fixed layer in the pMTJ structure is needed

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Implementation Method 2

The fixed layer includes anti-parallel layers including cobalt tungsten/platinum (CoW/Pt) bilayers, cobalt molybdenum/platinum (CoMo/Pt) bilayers

Methodology Applied

Scientific EffectSpin-orbit coupling:

Implementation Method 3

Spin transfer torque (STT) or spin transfer switching, uses spin-aligned ('polarized') electrons to directly apply a torque on the MTJ layers

Methodology Applied

Scientific EffectSpin transfer torque:

Implementation Method 4

A magnetic memory cell or device stores information by changing electrical resistance of a magnetic tunnel junction (MTJ) element

Methodology Applied

Scientific EffectMagnetoresistance:

Data Source

PatentUS10468457B1Magnetic random access memory structures and integrated circuits with cobalt anti-parallel layers, and methods for fabricating the same

Publication Date: 2019.11.05 GLOBALFOUNDRIES SINGAPORE PTE LTD

AI summary

Spin transfer torque magnetic random access memory structures, integrated circuits, and methods for fabricating integrated circuits are provided. An exemplary spin transfer torque magnetic random access memory structure has a perpendicular magnetic orientation, and includes a bottom electrode and a base layer over the bottom electrode. The spin transfer torque magnetic random access memory structure further includes a fixed layer over the base layer. The fixed layer includes anti-parallel layers including cobalt tungsten/platinum (CoW/Pt) bilayers, cobalt molybdenum/platinum (CoMo/Pt) bilayers, or bilayers including a combination of at least two materials selected from cobalt (Co), tungsten (W), molybdenum (Mo), platinum (Pt), palladium (Pd) or iridium (Ir). Also, the spin transfer torque magnetic random access memory structure includes a magnetic tunnel junction (MTJ) element with a perpendicular orientation over the fixed layer and a top electrode over the MTJ element.