Corrosion-Resistant Cap for Waveguide Core in HAMR Read/Write Head

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Solution Overview

Problem

In heat-assisted magnetic recording (HAMR) technology, the waveguide core in magnetic data storage devices is prone to corrosion due to interaction with reactive ions and moisture, leading to damage and performance issues.

Innovation Solution

A high-index, high-corrosion-resistant cap made of materials like Ta, Hf, Zr, Si, and Y compounds is introduced at the terminating end of the waveguide core, with a right trapezoidal cross-section and an oblique interface, providing additional protection against HF acid and water vapor, and covered by a head overcoat.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the waveguide core is made of NbO material, then it provides necessary optical functionality, but it is highly susceptible to corrosion from HF acid and water vapor

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidcorrosion from HF acid and water vapor

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A cap structure made of TaO or HfO2 is introduced as an intermediary layer between the NbO waveguide core and the corrosive environment (HF acid and water vapor). This cap acts as a protective mediator that prevents direct contact between the corrosive agents and the NbO core, thereby resolving the contradiction between maintaining optical functionality and resisting corrosion.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The waveguide core is constructed as a composite structure combining NbO (for optical functionality) with TaO or HfO2 caps (for corrosion resistance). This composite approach allows each material to contribute its advantageous properties: NbO provides the necessary optical performance while TaO/HfO2 caps provide superior corrosion resistance, eliminating the vulnerability of pure NbO to HF acid and water vapor.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a protective cap is added to the waveguide core, then corrosion resistance is improved, but the device complexity increases

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidwaveguide structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protective cap is implemented as a thin film or shell structure made of TaO or HfO2 that conforms to the waveguide core geometry. This thin-film approach provides effective corrosion protection without adding significant structural complexity or bulk to the device, as the cap simply follows the contour of the existing waveguide core.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The cap structure is applied locally only at the portions of the waveguide core most vulnerable to corrosion (such as exposed surfaces and edges), rather than requiring complete encapsulation. This localized protection approach maintains corrosion resistance where needed while minimizing the addition of structural complexity and material usage.

Inventive Principle:

Principle #3Local quality

3Illumination intensity

If the cap material has high index of refraction, then optical performance is maintained, but material selection becomes more limited

Engineering Contradiction:

Improveoptical performanceVSAvoidmaterial selection flexibility

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The cap material is selected with specific optical parameters (high index of refraction) to match or exceed the optical performance of the NbO core, while the material composition is adjusted to prioritize corrosion resistance. By carefully selecting TaO or HfO2, the solution achieves both high optical performance and superior corrosion resistance, resolving the contradiction between optical requirements and material versatility.

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

The cap significantly enhances the corrosion resistance of the waveguide core, reducing damage and maintaining thermal gradient and media temperature performance, as validated by modeling and etching rate tests, with TaO coatings showing at least 67 times lower etching rate compared to NbO.

Implementation Method 1

The cap is formed of a high index of refraction, high-corrosion resistant cap material that is different than a material used to form the waveguide core. The cap material includes a compound with one of Ta, Hf, Zr, Si, and Y. TaO coatings showing at least 67 times lower etching rate compared to NbO.

Methodology Applied

Scientific EffectCorrosion resistance:

Implementation Method 2

maintaining thermal gradient and media temperature performance

Methodology Applied

Scientific EffectThermal gradient: Temperature Gradient

Data Source

PatentUS10002626B1Corrosion resistance cap located on end of waveguide core

Publication Date: 2018.06.19 SEAGATE TECH LLC

AI summary

A waveguide core extends from an input coupler towards a media-facing surface of a read/write head. A cap is located between a terminating end of the waveguide core and the media-facing surface. The cap is formed of a high index of refraction, high-corrosion resistant material that is different than a material used to form the waveguide core. A near-field transducer is proximate the cap in a down-track direction. A head overcoat on the media-facing surface covers the cap.