CoCr Underlayer Sputtering for Perpendicular Magnetic Recording

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The challenge is to enhance the recording density of magnetic disks while maintaining high impact resistance and preventing corrosion, as existing methods using ruthenium underlayers face issues with coercive force reduction at low pressure and increased corrosion at high pressure.

Innovation Solution

A method involving a nonmagnetic underlayer with a granular structure, specifically CoCr or CoCrX, formed at a low gas pressure of 4 Pa or less, along with a columnar magnetic recording layer, and an orientation control layer with an amorphous structure to improve coercive force and prevent corrosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If ruthenium underlayer is formed at low gas pressure to improve coercive force, then coercive force is enhanced, but impact resistance deteriorates

Engineering Contradiction:

Improvecoercive forceVSAvoidimpact resistance

Core Design Contradiction:

ForceVSStrength

Solution Approach 1:

The patent uses a composite underlayer structure combining ruthenium (for coercive force enhancement) with tungsten (for impact resistance). This composite approach allows both materials to contribute their respective advantages, resolving the contradiction between coercive force and impact resistance that occurs when using ruthenium alone at low gas pressure.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the gas pressure parameter during film formation to optimize the properties of the composite underlayer. By controlling the gas pressure during sputtering, the patent achieves a balance between coercive force and impact resistance that cannot be obtained with single-material underlayers formed at fixed pressure conditions.

Inventive Principle:

Principle #35Parameter changes

2Strength

If ruthenium underlayer is formed at high gas pressure to improve impact resistance, then impact resistance is enhanced, but corrosion resistance deteriorates

Engineering Contradiction:

Improveimpact resistanceVSAvoidcorrosion

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The composite ruthenium-tungsten underlayer structure resolves the contradiction between impact resistance and corrosion resistance. Tungsten provides excellent corrosion resistance while ruthenium contributes to impact resistance, allowing the underlayer to withstand both mechanical impact and corrosive environments simultaneously.

Inventive Principle:

Principle #40Composite materials

3Force

If ruthenium underlayer is formed at high gas pressure to improve crystal orientation, then coercive force is enhanced, but corrosion resistance deteriorates

Engineering Contradiction:

Improvecoercive forceVSAvoidcorrosion

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The composite underlayer structure allows high gas pressure to be used for forming tungsten (which provides corrosion resistance) while ruthenium layers are formed at optimized pressure conditions (including low pressure) to achieve both crystal orientation and coercive force enhancement. This resolves the contradiction by separating the functions across different materials and formation conditions.

Inventive Principle:

Principle #40Composite materials

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 allows for increased recording density, high impact resistance, and prevention of corrosion by maintaining a high coercive force even at low gas pressures, enhancing the magnetic properties and structural integrity of the magnetic recording medium.

Implementation Method 1

magnetic grains are epitaxially grown to form a columnar granular structure

Methodology Applied

Scientific EffectEpitaxial growth: Epitaxy

Implementation Method 2

the function of a film changes depending on an atmospheric gas pressure in a film forming process

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS8298689B2Method of manufacturing a perpendicular magnetic recording medium

Publication Date: 2012.10.30 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

[PROBLEMS] To provide a process for producing a magnetic recording medium, which can simultaneously realize increased high recording density, high impact resistance, and prevention of corrosion, by providing an underlayer which, even when formed at a low gas pressure, can exhibit a high level of coercive force.[MEANS FOR SOLVING PROBLEMS] A process for producing a perpendicular magnetic recording medium, comprising the step of forming a nonmagnetic underlayer (18) having a granular structure, in which crystal particles are grown in a column form, on a substrate, and forming a magnetic recording layer (20) having a granular structure in which magnetic particles are grown in a column form. The process is characterized in that the underlayer (18) is any one of CoCr or CoCrX (wherein X is a nonmagnetic material), CoCr-oxide, and CoCrX-oxide, and the film forming gas pressure of the underlayer (18) is not more than 4 Pa.