Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2002-08-16
2004-09-14
Heinz, A. J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06791795
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a thin film magnetic head for use in a magnetic disk apparatus and to a production method of the thin film magnetic head. More particularly, the invention relates to a thin film magnetic head having a small track width suitable for high-density recording and to a production method thereof.
Development of a thin film magnetic head excellent in recording/reading characteristics has strongly been required in recent years with improvement in a recording density of magnetic disk apparatuses and with improvement in performance of recording media. Heads using an MR (magnetoresistive effect) element or a GMR (giant magnetoresistive effect) element capable of acquiring a high reading output have been used at present as reading heads. A TMR (tunnel magnetoresistive) element capable of acquiring a higher reading sensitive has also been developed. On the other hand, an inductive thin film recording head of the prior art that utilizes electromagnetic induction has been used, and a read/write type thin film magnetic head having these reading head and recording head formed integrally with each other has been used.
To improve the recording characteristics of the thin film magnetic head, a strong and sharp recording magnetic field must be generated for sufficiently recording data to a recording medium having high coercive force. However, because a track width decreases with the improvement in a track density, magnetic saturation develops at a magnetic pole front end part of the thin film magnetic head and a recording magnetic field drops. Improvement in processing accuracy of a smaller track width has also been required to cope with the improvement of the track density.
JP-A-2000-276707 proposes a method for improving processing accuracy of a small track width that separates an upper magnetic pole to an upper magnetic pole front end layer and an upper magnetic pole top layer. As shown in
FIG. 3
, according to this method, a lower magnetic shield
2
made of a soft magnetic material is arranged on a substrate
1
made of a non-magnetic material to improve reading resolution and to eliminate influences of an external magnetic field, a reading gap
3
made of a non-magnetic insulating material is arranged on the lower magnetic shield
2
, and a reading element comprising an MR or GMR element is arranged in the reading gap
3
. A lower magnetic pole
5
made of a soft magnetic material and serving also as an upper magnetic shield is disposed on the reading element
4
. A depth-defining non-magnetic layer
7
for defining a gap depth is arranged on the recording gap layer
6
, and an upper magnetic pole front end layer
8
and an upper magnetic pole rear end layer
9
are further disposed on the recording gap layer
6
. Gaps among these layers are filled with a non-magnetic insulating layer
10
and are planarized. A coil insulating layer
11
is disposed on the surface so planarized and a lower coil
12
and an upper coil
12
′ are arranged inside the coil insulating layer. The coil is a single-layered coil in some cases. After an upper magnetic pole top layer
13
is disposed, the head is protected as a whole by a protective layer
14
. The coils
12
and
12
′ are so constituted as to encompass a rear end portion
16
of the upper magnetic pole top layer. When a reading current is applied to the coils
12
and
12
′, a magnetic flux is induced in the upper magnetic pole top layer
13
, the upper magnetic pole rear end layer
9
and the lower magnetic pole
5
, and a signal is recorded to a recording medium
17
running in a spaced-apart relation by a very small distance from an air bearing surface
15
through a recording magnetic field generated from a front end of the recording gap. The magnetic flux concentrates on positions in the proximity of the recording gap from the lower magnetic pole and the upper magnetic pole front end layer. Consequently, a high recording magnetic field develops. A contact length of the upper magnetic pole front end layer
8
with the recording gap layer
6
is called a “gap depth Gd”. The magnetic flux concentrates much more on the magnetic pole front end when the gap depth Gd is smaller, so that the recording magnetic field increases.
When the upper magnetic pole front end layer
8
is formed, a photo resist is applied to the depth defining non-magnetic layer
7
and to the recording gap layer
6
. The photo resist is exposed and developed through a mask having a predetermined shape of the upper magnetic pole front end layer. A portion of the photo resist that is to serve as the shape of the upper magnetic pole front end layer is then removed, and a high saturation flux density material to serve as the upper magnetic pole front end layer is formed at the removed portion in accordance with a plating method. In the thin film magnetic head according to the prior art, the photo resist for forming the upper magnetic pole front end layer
8
is formed on the slope of the depth defining non-magnetic layer
7
. Therefore, when the photo resist is exposed, the shape of the upper magnetic pole front end layer cannot be formed with high accuracy due to reflection of light from the slope of the depth defining non-magnetic layer and due to insufficiency of the depth of focus. This problem becomes particularly serious when a narrow track width of the upper magnetic pole front end layer is formed.
To solve this problem, a method shown in
FIG. 4
has been proposed. In this method, a lower magnetic pole front end layer
19
and a lower magnetic pole rear end layer
20
are arranged on the lower magnetic pole main layer
18
, and the gaps between them is filled with a lower non-magnetic insulating layer
21
and is planarized. A recording gap layer
6
is formed. A resist frame is formed on this planarized surface and the upper magnetic pole front end layer
8
is then formed. In this way, the small track width can be formed with a high level of accuracy. However, according to this method, too, the lower magnetic pole front end layer
19
is processed by means such as ion milling with the front end portion of the upper magnetic pole front end layer
8
as a mask, and a projection portion of the lower magnetic pole front end layer
19
called a “trimming part” is formed. At this time, the width of the upper magnetic pole front end layer
8
to serve as the track width decreases as a result of ion milling. Therefore, a problem yet remains unsolved in that accuracy of the track width cannot be sufficiently improved due to the limit of processing accuracy of ion milling even when accuracy of the track width formed by the frame plating method becomes high because the final track width is formed by processing such as ion milling.
Therefore, JP-A-11-7609 describes a method that forms the projection part of the lower magnetic pole without executing the trimming process by ion milling. This method forms the projection part of the lower magnetic pole, the recording gap layer and the upper magnetic pole front end layer inside a resist frame having the same shape in accordance with a plating method. In this case, only frame plating is used without conducting ion milling to form the track width, and the frame is formed on the planar surface of the lower magnetic pole
5
as shown in FIG.
5
. Therefore, this method can acquire high track width accuracy. However, since the length of the lower magnetic pole projection layer
24
is equal to that of the upper magnetic pole front end layer
8
, the contact length Lc cannot be sufficiently secured between the upper magnetic pole top layer
13
and the upper magnetic pole front end layer
8
when the gap depth is reduced. In this case, the recording magnetic field does not become high. When the contact length is increased, the gap depth becomes great, too. Consequently, the recording magnetic field does not become high, either. On the other hand, the recording magnetic field intensity required for the recording head has becomes higher and higher with the increase of the record
Fukui Hiroshi
Fuyama Moriaki
Ohtomo Shigekazu
Yoshida Nobuo
Heinz A. J.
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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