Magnetic Memory Device Current Confinement Layer Design

Solution Overview

Problem

Magnetic memory devices require a further reduction in switching current to increase integration levels, but increasing the thickness of the tunnel insulating layer in TMR elements decreases magneto-resistance, while decreasing its thickness increases write current and reduces reliability and endurance.

Innovation Solution

A magnetic memory device is fabricated with a current confinement layer narrower than the free layer to locally increase current density, combining a TMR element for reading and a GMR element for writing, using conductive materials like copper and tantalum nitride to enhance spin-diffusion length and etch selectivity, and forming a recessed or cup-shaped current confinement layer to define voids and increase current density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the thickness of the tunnel insulating layer is increased to reduce switching current, then switching current is reduced, but magneto-resistance decreases

Engineering Contradiction:

Improveswitching currentVSAvoidmagneto-resistance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies local quality by creating a current confinement layer with different width characteristics in different regions. The current confinement layer has a first width at the first end and a second width at the second end, with the second width being smaller than the first width. This gradual narrowing locally concentrates the current density at specific regions (where the free layer is thinnest) without uniformly increasing current density throughout the entire structure, thereby reducing switching current while preserving magneto-resistance in the read element.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs dynamics by making the current confinement layer's width variable along its length rather than uniform. The width transitions from a first width at the first end to a second width at the second end, creating a dynamic current distribution that adapts to the varying thickness of the free layer. This dynamic width variation allows optimal current confinement at critical regions while maintaining overall device performance.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the thickness of the tunnel insulating layer is decreased to maintain magneto-resistance, then magneto-resistance is maintained, but write current increases and reliability and endurance decrease

Engineering Contradiction:

Improvemagneto-resistanceVSAvoidwrite current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies local quality by creating a current confinement layer with different width characteristics in different regions. The current confinement layer has a first width at the first end and a second width at the second end, with the second width being smaller than the first width. This gradual narrowing locally concentrates the current density at specific regions (where the free layer is thinnest) without uniformly increasing current density throughout the entire structure, thereby reducing switching current while preserving magneto-resistance in the read element.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs dynamics by making the current confinement layer's width variable along its length rather than uniform. The width transitions from a first width at the first end to a second width at the second end, creating a dynamic current distribution that adapts to the varying thickness of the free layer. This dynamic width variation allows optimal current confinement at critical regions while maintaining overall device performance.

Inventive Principle:

Principle #15Dynamics

3Ease of manufacture

If a uniform width current confinement layer is used, then manufacturing is simpler, but current density is not optimized for reducing switching current

Engineering Contradiction:

Improvecurrent confinement layer fabricationVSAvoidswitching current

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The patent applies local quality by creating a current confinement layer with different width characteristics in different regions. The current confinement layer has a first width at the first end and a second width at the second end, with the second width being smaller than the first width. This gradual narrowing locally concentrates the current density at specific regions (where the free layer is thinnest) without uniformly increasing current density throughout the entire structure, thereby reducing switching current while preserving magneto-resistance in the read element.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs dynamics by making the current confinement layer's width variable along its length rather than uniform. The width transitions from a first width at the first end to a second width at the second end, creating a dynamic current distribution that adapts to the varying thickness of the free layer. This dynamic width variation allows optimal current confinement at critical regions while maintaining overall device performance.

Inventive Principle:

Principle #15Dynamics

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 solution achieves a magnetic memory device with large magneto-resistance and small switching current, enabling higher integration levels without compromising reliability or endurance.

Implementation Method 1

The TMR effect is a magneto-resistance effect that occurs when a pair of ferromagnetic layers have a thin tunnel insulating layer interposed therebetween.

Methodology Applied

Scientific EffectTunneling magneto-resistance (TMR) effect: Magnetoresistance

Implementation Method 2

The GMR effect, which was first discovered in an Fe/Cr artificial lattice by M. N Baibich et al. in 1998, is generally a magneto-resistance effect that occurs when a ferromagnetic layer and a nonmagnetic layer form an artificial lattice.

Methodology Applied

Scientific EffectGiant magneto-resistance (GMR) effect: Magnetoresistance

Implementation Method 3

a write element changing the magnetization direction of the free layer, wherein the write element includes a current confinement layer having a width smaller than the minimum width of the free layer to locally increase the density of a current flowing through the write element

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS8247880B2Magnetic memory device and method of fabricating the same

Publication Date: 2012.08.21 SAMSUNG ELECTRONICS CO LTD

AI summary

A magnetic memory device and a method of fabricating the same. The magnetic memory device includes a free layer, a write element, and a read element. The write element changes the magnetization direction of the free layer, and the read element senses the magnetization direction of the free layer. Herein, the write element includes a current confinement layer having a width smaller than the minimum width of the free layer to locally increase the density of a current flowing through the write element.