TMR Sensor Radiation Reflective Layer Temperature Stability

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Solution Overview

Problem

In magnetic recording, maintaining substrate temperature during transport between processing chambers is challenging, especially when using cryogenic cooling, which affects the deposition of amorphous free layers and requires short transport times to prevent heating, thus necessitating a method to stabilize the substrate temperature.

Innovation Solution

Incorporating a high radiation reflective layer between the bottom shield and the magnetic seed layer in the TMR device, which can be made of materials like copper, silver, or gold, helps maintain temperature stability and reduces resistance area (RA) while increasing magnetoresistance (MR).

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cryogenic cooling is used to cool the free layer of the TMR sensor, then the TMR increases, but the substrate temperature heats up during transport between chambers

Engineering Contradiction:

ImproveTMRVSAvoidsubstrate temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

A radiation reflective layer is introduced as an intermediary component between the substrate and the environment. This layer reflects thermal radiation back toward the substrate, preventing heat loss during transport and maintaining the cryogenic temperature required for high TMR performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful effect of heat transfer during transport into a beneficial effect by using the reflective layer to trap and recycle thermal radiation, turning potential heat loss into heat retention that maintains the desired low temperature for high TMR.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Temperature

If the transport time between chambers is extended, then the substrate temperature stabilizes, but the TMR decreases due to heating

Engineering Contradiction:

Improvesubstrate temperature stabilityVSAvoidTMR

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The radiation reflective layer enables continuous thermal insulation during transport, maintaining the cryogenic temperature throughout the entire transport duration without requiring rapid transfer, thus preserving TMR performance while allowing extended transport times.

Inventive Principle:

Principle #20Continuity of useful action

3Temperature

If a radiation reflective layer is added to maintain temperature, then the substrate temperature is stabilized, but the device complexity increases

Engineering Contradiction:

Improvesubstrate temperature stabilityVSAvoidlayer structure

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The radiation reflective layer is implemented as a thin film deposited on the substrate, providing effective thermal insulation with minimal addition to device complexity. This thin-film approach maintains temperature stability while avoiding the need for bulky insulation structures.

Inventive Principle:

Principle #30Flexible shells and thin films

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 high radiation reflective layer effectively stabilizes the substrate temperature during transport, decreases RA, and increases MR, leading to improved signal-to-noise ratio (SNR) and reduced signal distortion in TMR devices.

Implementation Method 1

Methodology Applied

Scientific EffectThermal radiation reflection: Reflection

Implementation Method 2

There is a trend in magnetic recording to achieve higher areal densities. A lower track width (TW) is desired for higher areal density medias. Keeping the head signal-to-noise (SNR) higher is necessary for a smaller TW. In order to have a high SNR, a larger magnetoresistance (MR) and lower resistance area (RA) is necessary.

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS11125840B2Ultra-low RA and high TMR magnetic sensor with radiation reflective lead

Publication Date: 2021.09.21 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

The present disclosure generally relates to a tunnel magnetoresistive (TMR) device. The TMR device includes a high radiation reflective layer between the bottom shield of the TMR device and the magnetic seed layer. The high radiation reflective layer helps to maintain the TMR device temperature during transportation between processing chambers. Additionally, the high radiation reflective layer decreases the resistance area (RA) of the TMR device while also increasing the magnetoresistance (MR) of the TMR device.