Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-08-09
2004-03-02
Heinz, A. J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06700740
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a thin-film magnetic head having at least an induction-type electromagnetic transducer and a method of manufacturing the same.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as areal recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a write head having an induction-type electromagnetic transducer for writing and a read head having a magnetoresistive element (hereinafter, also referred to as MR element) for reading.
The write head comprises: a bottom pole layer and a top pole layer including pole portions that are opposed to each other and placed in regions on a side of an air bearing surface; a write gap layer provided between the pole portion of the bottom pole layer and the pole portion of the top pole layer; and a thin-film coil arranged such that at least a part thereof is insulated from the bottom pole layer and the top pole layer.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a write head. To achieve this, it is required to implement a write head of a narrow track structure wherein the width of the pole portions of the bottom and top pole layers on a side of the air bearing surface, that is a write track width, is reduced down to microns or the order of submicron. Semiconductor process techniques are utilized to implement such a structure.
Additionally, in order to prevent an increase in effective write track width due to magnetic flux expansion in between the pole portion of the bottom pole layer and the pole portion of the top pole layer, there has conventionally been adopted a structure in which the pole portion of the top pole layer and at least a part of the pole portion of the bottom pole layer are given an equal width. This structure is referred to as a trim structure.
FIG. 21
is a perspective view showing an example of the structure in the vicinity of the pole portions of a write head. In this example, a write gap layer
109
is formed on a bottom pole layer
108
. A thin-film coil that is not shown and an insulating layer
112
for covering the thin-film coil are formed on the write gap layer
109
. An end of the insulating layer
112
closer to an air bearing surface
130
is located at a predetermined distance from the air bearing surface
130
, thereby defining a throat height. The throat height is the length (height) of portions of two pole layers facing each other with the write gap layer in between, as taken from the end closer to the air bearing surface
130
to the other end. A top pole layer
113
is formed on the write gap layer
109
and the insulating layer
112
.
The top pole layer
113
has: a first portion
113
A that includes the pole portion; and a second portion
113
B that includes a yoke portion. The width of the first portion
113
A is constant and equal to the write track width. The width of the second portion
113
B is equal to the width of the first portion
113
A at the interface with the first portion
113
A. It gradually grows wider as the distance from the air bearing surface
130
increases, and then becomes constant.
A part of the first portion
113
A is laid on the write gap layer
109
, the part extending from the end of the first portion
113
A located in the air bearing surface
130
to a position corresponding to the end of the insulating layer
112
closer to the air bearing surface
130
. The other part of the first portion
113
A is laid on the insulating layer
112
. The second portion
113
B is mostly laid on the insulating layer
112
. The second portion
113
B, at a part near its end farther from the air bearing surface
130
, is connected to the bottom pole layer
108
through a contact pole formed in the write gap layer
109
.
In a region where the first portion
113
A of the top pole layer
113
and the bottom pole layer
108
are opposed to each other with the write gap layer
109
in between, a trim structure is formed, that is a structure in which the first portion
113
A, the write gap layer
109
, and a part of the bottom pole layer
108
closer to the write gap layer
109
have an equal width.
The trim structure as shown in
FIG. 21
is formed, for example, by the following steps. That is, the second portion
113
B of the top pole layer
113
is initially covered partially with an etching mask made of a photoresist, from a position halfway through its spreading part to the side farther from the air bearing surface
130
. Next, the write gap layer
109
and a part of the bottom pole layer
108
closer to the write gap layer
109
are etched by dry etching. Here, the first portion
113
A of the top pole layer
113
not covered with the etching mask is used as a mask. For example, reactive ion etching is used for etching the write gap layer
109
; ion beam etching (ion milling) is used for etching the bottom pole layer
108
.
In the thin-film magnetic head shown in
FIG. 21
, the first portion
113
A of the top pole layer
113
has a constant thickness.
Now, if the width of the first portion
113
A of the top pole layer
113
, that is, the write track width, falls to 1 &mgr;m or below, for example, the magnetic flux may be saturated halfway through the first portion
113
A, possibly precluding the efficient use of magnetomotive force generated by the thin-film coil for writing.
To avoid this, the first portion
113
A of the top pole layer
113
can be increased in thickness. Hard disk drives, however, have some skew between the direction perpendicular to the surfaces of the bottom and top pole layers
108
,
113
and the track direction. This results in a problem that the increased thickness of the first portion
113
A of the top pole layer
113
can cause so-called side write, which means that data is written in regions of a recording medium where data is not supposed to be written, and so-called side erase, which means that data is erased from regions where data is not supposed to be written.
OBJECT AND SUMMARY OF THE INVENTION
An object of the present invention is to provide a thin-film magnetic head and a method of manufacturing the same, capable of preventing magnetic flux saturation in the middle of the magnetic path and preventing data from being written/erased in regions where data is not supposed to be written, even at smaller track widths.
A thin-film magnetic head according to the present invention comprises: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. Here, the second magnetic layer has a first portion and a second portion. The first portion has an end located in the medium facing surface, has a constant width equal to a write track width, and includes the pole portion. The second portion is coupled to the other end of the first portion and includes a yoke portion, The thickness of the first portion in a region extending from the end of the first portion located in the medium facing surface to a predetermined position is smaller than the thickness of the other part of the second magnetic layer adjacent to that region.
A method of manufacturing a thin-film magnetic head according to the present invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other a
Kuwashima Tetsuya
Matono Naoto
Heinz A. J.
Oliff & Berridg,e PLC
TDK Corporation
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