Selective Wet Etching of Silicon Dioxide in Magnetic Head Poles

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Solution Overview

Problem

The existing methods for producing magnetic heads face challenges in removing the silicon dioxide matrix surrounding the magnetic pole without etching the main pole or side gap material, which affects the head's performance due to residual silicon dioxide left behind, especially when using dry etching with fluorine compounds.

Innovation Solution

A magnetic head design incorporating a side gap layer primarily made of silicon nitride with a tapering shape and a seed layer, where the silicon dioxide layer is removed using a high pH wet etching solution like NaOH, which selectively etches silicon dioxide without affecting the silicon nitride or the main pole, ensuring the integrity of the magnetic head components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If dry etching with fluorine compounds is used to remove silicon dioxide, then the silicon dioxide matrix can be removed, but residual silicon dioxide remains near the bottom of the main pole and manufacturing precision deteriorates

Engineering Contradiction:

Improvesilicon dioxide removalVSAvoidhead geometry precision

Core Design Contradiction:

Loss of substanceVSManufacturing precision

Solution Approach 1:

The patent changes the etching parameters by switching from dry etching with fluorine compounds to wet etching with hydroxide solutions (such as NaOH or KOH). This parameter change enables complete removal of silicon dioxide without leaving residuals, while the high pH solution selectively etches only the silicon dioxide and not the side gap layer or main pole materials, thereby maintaining manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

2Loss of substance

If HF-based wet etching solution is used to remove silicon dioxide, then the silicon dioxide matrix can be removed, but the main pole material such as CoNiFe alloy is etched away

Engineering Contradiction:

Improvesilicon dioxide removalVSAvoidmain pole corrosion

Core Design Contradiction:

Loss of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by using a hydroxide-based wet etching solution that has selective etching properties. The high pH solution locally affects only the silicon dioxide matrix while leaving the side gap layer (such as silicon nitride or alumina) and main pole materials (such as CoNiFe alloy) unaffected. This selective action removes the silicon dioxide without causing harmful corrosion to the main pole.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If alumina is used as the dielectric material, then wet etching can be performed easily and isotropically, but the etching process is not selective to the side gap layer

Engineering Contradiction:

Improvewet etching easeVSAvoidside gap layer integrity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the material parameter from alumina to silicon dioxide for the dielectric layer. This change enables the use of hydroxide-based wet etching solutions that provide both ease of manufacture through isotropic etching and manufacturing precision through high selectivity. The silicon dioxide etches readily in high pH solutions while the side gap layer materials remain intact, resolving the contradiction between ease of manufacture and side gap layer integrity.

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 effectively removes the silicon dioxide matrix while maintaining the main pole's integrity, preventing corrosion and ensuring precise geometry, thus enhancing the performance of the magnetic head by using a high pH solution that selectively etches silicon dioxide without affecting silicon nitride or CoNiFe alloys.

Implementation Method 1

removing the silicon oxide layer by wet etching

Methodology Applied

Scientific EffectSelective wet etching:

Implementation Method 2

a solution which can remove the silicon dioxide matrix without etching the main pole and side gap material

Methodology Applied

Scientific EffectChemical dissolution:

Data Source

PatentUS8432637B2Wet etching silicon oxide during the formation of a damascene pole and adjacent structure

Publication Date: 2013.04.30 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A magnetic head according to one embodiment includes a side gap layer comprising primarily silicon nitride, wherein outer sides of the side gap layer taper away from one another from a leading end of the side gap layer towards a trailing end of the side gap layer; a seed layer above the silicon nitride side gap layer; and a magnetic pole on the seed layer. A method for forming a magnetic head according to one embodiment includes etching a channel in a silicon oxide layer; forming a side gap layer comprising primarily silicon nitride in the channel; forming a seed layer above the side gap layer; plating a pole on the seed layer; and removing the silicon oxide layer by wet etching. Additional systems and methods are also presented.