Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-01-11
2004-10-12
Letscher, George J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06804088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head of inductive type, a production method thereof, and magnetic recording apparatus.
2. Description of the Related Art
Recently, the recording density of a hard disc apparatus has been remarkably increased. Since the 1990 year, the recording density has been increased by about 60% every year. In order to increase the recording density of a hard disc apparatus, it is necessary to reduce the magnetic head track width so as to increase the recording track density. Furthermore, in order to increase the recording density, it is also important to increase the recording bit density. For increasing the recording bit density, it is necessary to increase the recording medium having a high coercive force Hc requires an inductive magnetic recording head having a high recording efficiency. Moreover, in order to effectively detect a signal from a small recording bit, it is necessary to use an MR reproduction head. Accordingly, there is a great expectation on a high density recording realized by using an MR head in combination with an inductive recording head, i.e., a thin film magnetic head of the MR-inductive composite type.
FIG.
15
and
FIG. 16
show a conventional thin film magnetic head of the MR-inductive composite type.
FIG. 16
is plan view of the entire configuration and
FIG. 15
is a cross sectional view about the XV—XV line in FIG.
16
.
The conventional thin film magnetic head
70
includes a lower shield layer
74
, a read gap layer
80
, a lower pole layer
82
serving also as an upper shield layer; and a write gap layer
84
formed in this order on an insulation substrate (not depicted). The thin film magnetic head
70
also includes a magneto-sensitive element inserted into the read gap layer and facing the ABS (air bearing surface)
76
. The thin film magnetic head
70
further includes: the a first filling material layer
86
formed on the write gap layer
84
excluding the vicinity of the ABS
76
; a coil pattern layer
88
; and a second filling material layer
90
formed in this order. The thin film magnetic head
70
further includes a recording pole layer
92
formed on the write gap layer
84
and the first filling material layer
86
as well as on the second filling material layer
90
.
The lower pole layer
82
serves as a lower pole layer of the inductive recording head as well as an upper shield layer for increasing the reproduction resolution. The MR magneto-sensitive element
78
detects a signal magnetic field from a magnetic storage medium (not depicted) facing the ABS
76
. The write gap layer
84
has a thickness as a gap of the inductive recording head. The first filling material layer
86
serves as an insulation fundament of the coil pattern layer
86
. The second filling material layer
90
dissolves the convex and concave configuration of the coil pattern layer
88
.
Explanation will now be given on the recording operation of the thin film magnetic head
70
. A magnetic flux generated when electric current is applied to the coil pattern layer
88
flows from a pole window
94
at the center of the coil pattern layer
88
through the recording pole
92
having a small magnetic reluctance (by 10 to 100 times compared to the air) to return to the pole window
94
. On the other hand, the recording pole and the lower pole layer
82
are connected to each other via a space provided by the write gap layer. Accordingly, a portion of the magnetic field in the write gap layer
84
leaks to the ABS
76
, generating a recording magnetic field.
FIG.
17
and
FIG. 18
shows a part of the thin film magnetic head
70
enlarged partially.
FIG. 18
is a partial plan view, and
FIG. 17
is a cross sectional view about the line XVII—XVII in
FIG. 18
Explanation will now given, referring to these figures.
Firstly, in this Specification the terms “width” and “length” are defined as follows. The width is in a direction vertical to the thickness direction of the write gap layer
84
and parallel to the ABS
76
. The length is in a direction vertical to the ABS
76
.
The recording pole
92
can be divided into a tip portion
921
, a flare portion
92
, and a yoke portion
923
in this order from the side of the ABS
76
. The flare portion
922
reduces its width continuously from the yoke portion
923
toward the tip portion
921
. The tip portion
921
extends with a constant width W from the ABS
76
to reach the flare portion
922
.
Referring to
FIG. 17 and 18
, it is assumed that the tip portion
921
has tip length L. The tip length L is determined by a mask pattern used when performing frame plating of the recording pole layer
92
. Moreover, a gap depth D is assumed to be a distance between the ABS
76
and the tip of the first of the first filling material layer. That is, the depth D is a portion of the write gap layer sandwiched only by the recording pole layer and the lower pole layer. The recording track width is determined by the tip width W of the recording pole layer
92
and is almost equal to the tip width W. In order to obtain a high recording density, it is necessary to realize the recording pole layer
92
having a tip width W as small as possible.
As shown in
FIG. 18
, the relationship between the tip length L and the gap depth D is conventionally L>D. Accordingly, the tip portion
921
is partially located on a stepped portion of the first filling material layer
86
. On the other hand, the photo-resist pattern used for forming the tip portion
921
deteriorates the dimension accuracy because the light is reflected by the stepped portion during exposure. Accordingly, in order to form the tip width W at the ABS
76
with a high dimensional accuracy, the flare portion
922
reflecting a large amount of light should be located at a large distance from the ABS
76
.
The magnetic flux which has passed through the yoke portion
923
is converged at the flare portion
922
and further converted at the narrow tip portion
921
. When the tip length L is large, a considerable leak is caused at a narrow portion of a high magnetic reluctance such as the tip portion
921
. This decreases the magnetic flux supply to the tip portion
921
. This, in turn, decreases the magnetic field at the write gap layer
84
at the ABS
76
. Accordingly, in order to reduce the magnetic reluctance at the tip portion
921
so as to obtain a sufficient recording magnetic field, it is necessary to make the tip length L as much as possible.
However, if the tip length L is decreased, the flare portion
922
is formed at a position nearer to the ABS
76
. Accordingly, if the tip length L is reduced, as has been described above, the light reflection from the stepped portion deteriorates the pattern formation accuracy at the tip portion
921
.
Thus, the accurate formation of the tip reduction of the magnetic reluctance of the tip portion
921
so as to obtain a sufficient recording magnetic field.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a thin film magnetic head, a production method thereof, and a magnetic recording apparatus, wherein the tip width can be formed with a high accuracy without increasing the magnetic reluctance at the tip portion. The present invention provides a thin film magnetic head comprising a write gap layer formed on a lower pole layer; a first filling material layer, a coil pattern layer, a second filling material layer which are successively formed in this order on the write gap layer excluding the vicinity of the ABS; and a recording pole layer formed on the write gap layer at least in the vicinity of the ABS. The recording pole layer is divided into a tip portion, a wide rear portion, a flare portion, and a yoke portion in this order viewed from the ABS. The tip portion and the wide rear portion are provided on the write gap layer. The wide rear portion has a greater width than the tip portion when the width is determined as vertical to the film thickness direction of the write gap layer and parallel to
Ishiwata Nobuyuki
Nonaka Yoshihiro
Saitho Shinsaku
Shimabayashi Kiyotaka
Suzuki Tetsuhiro
Beacham Christopher R.
Letscher George J.
McGinn & Gibb PLLC
NEC Corporation
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