Dynamic magnetic information storage or retrieval – Head – Head surface structure
Reexamination Certificate
2000-06-22
2001-08-21
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head surface structure
C360S125330
Reexamination Certificate
active
06278578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magnetic head for use in magnetic recording and to a fabrication method thereof. An embodiment of the present invention relates particularly to a read/write magnetic head which is suitable for high density read/write operations.
2. Description of the Prior Art
An example of conventional magnetic head technology is disclosed in JP-A-59-178609.
A magnetic head of the type in which only a head gap portion projects to a medium direction has been proposed in order to accomplish high density magnetic recording. For example, “IEEE TRANSACTIONS ON MAGNETICS”, Vol. 24, No. 6, November, 1984, pp. 2841-2843, describes a method of deciding a track width of a magnetic head by applying machining from an air bearing surface side.
As to a magnetoresistive head (hereinafter referred to as an “MR head”) used as a read-only magnetic head, too, JP-A-59-71124 and JP-A-1-277313 disclose structure in which only a track width portion (magnetic sensing region) is projected to a medium opposing surface.
On the other hand, a read/write magnetic head produced by integrating the MR head and an induction-type write head is known from JP-A-51-44917, for example.
SUMMARY OF THE INVENTION
However, the magnetic head having the structure of the IEEE reference described above involves the problem that off-track performance is low because flux leaks from regions other than the track width, which is defined by etching. Since a relatively wide region of a slider rail is removed by etching, floating characteristics of a slider vary greatly before and after machining. An etching technique used for an ordinary semiconductor process is utilized, it becomes extremely difficult to uniformly coat a resist onto the slider rail, and the problem of mass-producibility is left unsolved.
The technology disclosed in JP-A-59-71124 and JP-A-1-277313 is not free from the following problem. When the MR head, only the magnetic sensing region of which is allowed to project, is produced, magnetic shield layers that interpose the MR sensor from both sides are greater than the width of projection, so that flux from adjacent tracks which cross one another through these shield layers results in noise. This exacerbates the problem that the signal-to-noise ratio drops because signals also become weaker with a smaller track width.
Furthermore, when a composite magnetic head is produced by combining the MR sensor, only the magneto sensitive region of which projects, and the induction type write head, the width of the write magnetic pole and that of the projecting portion of the MR sensor deviate from each other due to a positioning error, and the ratio of this deviation to the track width becomes greater with a smaller track width. Therefore, another problem occurs that read efficiency drops.
In other words, the conventional MR head described above employs the structure wherein only the track width portion is projected to the medium opposing surface so as not to detect signals at portions other than at the read track width for the purpose of accomplishing a smaller track width. In the conventional head of this kind an MR sensor pattern, only the track width portion which projects, is formed on a substrate, and a read head and the like are formed in such a manner as to align with this projecting portion. Thereafter the substrate is cut and the cut surface is polished in order to obtain a head whose projecting portion only is exposed to a medium opposing surface. Accordingly, the projecting width of the MR sensor, the width of the shield layers, the width of the recording magnetic pole and the projecting width of the MR sensor do not inevitably coincide with one another.
It is a first object of the present invention to provide a narrow track magnetic head having excellent off-track performance and a fabrication method thereof.
It is a second object of the present invention to provide a magnetic head having a high signal-to-noise ratio.
It is a third object of the present invention to provide a read/write magnetic head free from a positioning error between a write head and a read head but having a high signal-to-noise ratio.
It is a fourth object of the present invention to provide a fabrication method of a magnetic head which reduces the track width of a magnetic head without changing floating characteristics of a slider.
It is a fifth object of the present invention to provide a fabrication method of a magnetic head for high density recording having a narrow track width at a high fabrication yield.
The first object of the present invention described above can be accomplished by disposing at least one trench or groove at part of an air bearing surface between a magnetic head and a medium. More definitely, local recesses are defined near a magnetic gap of the magnetic head or its magnetic sensing region so as to define the width of these members. In one preferred embodiment of the invention, these trenches or recesses are formed by focused ion beam (hereinafter referred to as “FIB”) machining. In another preferred embodiment of the invention, a material is packed into these trenches or recesses.
The second object of the invention described above can be accomplished by carrying out track width machining in bulk from an air bearing surface side after an MR sensor and shield layers are formed on a substrate.
The third object of the invention described above can be accomplished by forming a write head and a read head on a substrate and then carrying out track width machining by etching from a polished and cut surface in order to prevent the track position error between the write head and the read head. In other words, while only the track width portion of a soft magnetic film of each of the write and read heads constituting the magnetic head is left on a floating surface, the other portions are removed in such a manner as to increase the distance from the medium. At the same time, track width machining is applied also to the shield layer of the read head so that only the projecting portion is exposed on the floating surface. In still another preferred embodiment of the present invention, a stopper material for etching is disposed in advance on a machining portion in a head lamination process in order to prevent the exposure of a planarization layer that covers the coil of the write head, and a coil when machining is made from the floating surface.
The fourth object of the invention described above can be accomplished by machining part of a rail of an air bearing surface of a head slider by use of a focused ion beam.
The fifth object of the invention described above can be accomplished by machining the shape of the magnetic head by use of a beam having focused energy without coating a resist onto the slider rail.
When at least one trench is disposed at part of the air bearing surface of the magnetic head with the medium, magnetic flux does not leak from regions other than from the track width region defined by the trench. Accordingly, a narrow track magnetic head having high off-track performance can be provided.
Yield and accuracy of machining can be improved by using a focused ion beam when the trench is formed only at part of the air bearing surface.
The leak of the flux can be reduced further by packing a material into the trench described above.
After the MR sensor and the shield layer are formed on the substrate, track width machining is carried out as a whole from the air bearing surface side with respect to the medium and in this manner, the width of the shield layer can be made substantially equal to the projecting width of the MR sensor. Accordingly, the flux from adjacent tracks does not mix through the shield layer, resulting in no noise, so that a magnetic head having a high signal-to-noise ratio can be obtained.
In the present invention, the distance between the members inclusive of the magnetic shield layer and the medium and between the magnetoresistive sensor and the medium, that is, the spacing, is great at the portions other than the projecting portio
Ishikawa Chiaki
Ishitani Tohru
Kobayashi Toshio
Koyama Naoki
Moriwaki Eijin
Evans Jefferson
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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