Thin-Film Magnetic Head Pole Width Uniformity

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Solution Overview

Problem

Conventional thin-film magnetic heads for perpendicular recording suffer from side fringe issues due to uneven magnetic pole widths, leading to decreased overwrite characteristics and susceptibility to pole erasure, primarily because of the inadequate formation of magnetic pole forming depressions in the base insulating layer during the manufacturing process.

Innovation Solution

The method involves using two resist layers with specific slit patterns to etch the base insulating layer, creating a magnetic pole forming depression with acute angles of inclination, which increases the magnetic volume and reduces pole erasure by ensuring uniform magnetic pole widths and precise filling of the depression with magnetic material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a bevel form is used for the magnetic pole end part to reduce skew angle, then side fringe is reduced, but magnetic pole width uniformity deteriorates

Engineering Contradiction:

Improveside fringeVSAvoidmagnetic pole width uniformity

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The magnetic pole forming depression is segmented into three distinct regions: a very narrow groove part (0.1-0.3 μm width) for precise magnetic pole end definition, a variable width depression for gradual transition, and a fixed width depression for uniform pole body. This segmentation allows each region to fulfill its specific function while maintaining overall pole width uniformity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The base insulating layer is pre-formed with a magnetic pole forming depression having a very narrow groove part at its end before the main magnetic pole layer is deposited. This preliminary structuring ensures that when the magnetic pole layer is formed and subsequently cut, the magnetic pole width is uniformly defined by the groove width, preventing both side fringe and width variation.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If magnetic pole width is reduced for higher recording density, then recording density improves, but overwrite characteristic deteriorates

Engineering Contradiction:

Improverecording densityVSAvoidoverwrite characteristic

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The magnetic pole forming depression exhibits local quality variations: the very narrow groove part (0.1-0.3 μm) provides high precision for narrow pole width and high recording density, while the fixed width depression provides sufficient magnetic volume for good overwrite characteristic. This local differentiation allows simultaneous achievement of high density and reliability.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If single resist layer is used for manufacturing, then manufacturing process is simple, but magnetic pole forming precision deteriorates

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidmagnetic pole forming precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The manufacturing process is segmented into two resist layer steps: first resist layer forms the very narrow groove part with high precision, second resist layer forms the fixed width depression. This segmentation enables precise control of magnetic pole dimensions that cannot be achieved with a single resist layer, while maintaining reasonable manufacturing complexity.

Inventive Principle:

Principle #1Segmentation

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 enhances the overwrite characteristic and reduces pole erasure by increasing the magnetic volume and ensuring uniform magnetic pole widths, thereby improving recording density and data integrity.

Implementation Method 1

etching the base insulating layer while using the first resist layer as a mask

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

etching the base insulating layer while using the second resist layer as a mask

Methodology Applied

Scientific EffectEtching:

Implementation Method 3

filled with the main magnetic pole layer

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS8169740B2Thin-film magnetic head structure and thin-film magnetic head

Publication Date: 2012.05.01 HEADWAY TECHNOLOGIES INC

AI summary

A thin-film magnetic head including a main magnetic pole layer having a magnetic pole end part on a side of a medium-opposing surface opposing a recording medium; a write shield layer opposing the magnetic pole end part to form a recording gap layer on the medium-opposing surface side; a thin-film coil wound about the write shield layer or the main magnetic pole layer; and a base insulating layer formed with a magnetic pole forming depression, including a very narrow groove defining a form of the magnetic pole end part and a main depression integrally extending from an end part of the very narrow groove remote from the medium-opposing surface. A stepped part is formed at a boundary between a bottom face of the main depression and a bottom face of the very narrow groove. The main magnetic pole layer is the only magnetically functional layer in the depression.