Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-11-16
2002-11-26
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06487042
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inductive-type thin-film magnetic head and a magnetic storage apparatus using the magnetic head.
2. Description of the Prior Art
The recording density of a hard disk drive has been remarkably improved. The recording density from 1990 downward tends to rise at an annual rate of approx. 60%. To improve the recording density of a hard disk drive, it is necessary to improve the recording track density by decreasing the track width of a magnetic head. Moreover, to improve the recording density, it is also important to improve the recording bit density. To improve the recording bit density, it is necessary to increase the coercive force (Hc) of a magnetic storage medium. Moreover, to write data in a high-Hc magnetic storage medium, an inductive recording head having a high recording capacity is necessary. Furthermore, to efficiently detect a signal output from a micro-scaled recording bit, an MR reproducing head is necessary. Therefore, an MR-inductive composite-type thin-film magnetic head constituted by combining an MR reproducing head with an inductive recording head is prospective for high-density recording.
FIG. 11
is a sectional view showing a conventional thin-film magnetic head. The thin-film magnetic head will be described below by referring to FIG.
11
.
The conventional thin-film magnetic head
70
is produced by forming a lower shielding layer
74
, a read gap layer
80
holding an MR magnetosensitive element
78
facing to an ABS plane
76
, a shared pole layer
82
serving as an upper shielding layer and a lower pole layer, and a write gap layer
84
laminated in order on an insulating substrate
72
; by forming a first flattening layer
86
, a coil pattern layer
88
, and a second flattening layer
90
laminated in order on the write gap layer
84
excluding the vicinity of the ABS plane
76
; and by forming an upper pole layer
92
on the write gap layer
84
, first flattening layer
86
, and second flattening layer
90
nearby the ABS plane
76
.
The shared pole layer
82
serves as an upper shielding layer for improving the reproducing resolution of an MR reproducing head and a lower pole layer of an inductive recording head. The MR magnetosensitive element
78
detects a signal magnetic field outputted from a not-illustrated magnetic storage medium facing to the ABS plane
76
. The thickness of the write gap layer
84
serves as the gap of the inductive recording head. The first flattening layer
86
serves as the insulating base of the coil pattern layer
88
and the second flattening layer
90
smoothens the irregularity in height of the coil pattern layer
88
. A portion on the write gap layer
84
nearby the ABS plane
76
where there is no first flattening layer
86
determines the gap depth D of an inductive recording head. A recording track width is determined by the front end portion width W (not illustrated) of the upper pole layer
92
. The front end portion width W represents the width of the upper pole layer
92
along the ABS plane
76
(front end) in the direction vertical to the drawing plane, which is shown in
FIG. 2
or the like.
To improve the recording capacity for high-density recording, it is preferable to set the gap depth D to a small value of approx. 1 [micron meter] or less. Moreover, to correspond to high-density recording, it is preferable to realize an upper pole layer
92
having a minimum front end portion width W. Furthermore, because a recording/reproducing data transfer rate is raised as a recording density (particularly, linear recording density) rises, a high speed recording capacity is required for a magnetic head for high-density recording.
Moreover, Japanese Patent Application Laid-Open No. 4-285711 discloses an invention for accurately forming a very-small-width magnetic-pole front end portion of a magnetic recording/reproducing thin-film magnetic head. Specifically, the front end portion of a lower magnetic pole and that of an upper magnetic pole are simultaneously formed on a lower magnetic-pole layer, gap layer, and upper magnetic-pole layer formed on a substrate through simultaneous ion etching by using a mask corresponding to the shape of a magnetic-pole front end portion. Then, a thin-film coil and an insulating film are formed to form the rear of an upper magnetic pole.
Furthermore, Japanese Patent Application Laid-Open No. 7-192222 discloses a thin-film magnetic head capable of effectuating a high-density recording/reproducing characteristic and an overwriting characteristic for data write. In this case, among gaps formed on a pole portion, a pole front end portion is formed into a narrow gap and the innermost side of the pole portion is formed into a wide gap g
2
.
Furthermore, Japanese Patent Application Laid-Open No. 9-237407 discloses a thin-film magnetic head capable of realizing higher density recording by reducing the number of magnetic fields generated at the lateral side of a magnetic pole and controlling the write spread and moreover, controlling the eddy-current loss when raising a recording frequency. In this case, the cross section of an upper magnetic pole is formed into a trapezoid and the major side is set so as to face a lower magnetic pole (upper shielding layer). Moreover, an upper magnetic pole is formed into a two-layer structure, the first layer of a lower magnetic pole is formed of a magnetic material having a large residual flux density, magnetic permeability, and resistivity (e.g. FeN, FeNZr, or FeNNb) and the second layer of it is formed of permalloy.
BRIEF SUMMARY OF THE INVENTION
OBJECT OF THE INVENTION
The first problem is that a pattern accuracy enough to decrease a gap depth D and a front end portion width W is not obtained. The first problem will be described below in detail using FIG.
1
.
To form a necessary gap depth D, the first flattening layer
86
, which defines the gap depth D, must be considerably nearing the ABS plane
76
. Therefore, the conventional thin-film magnetic head
70
had the following problem in order to form a resist frame pattern (not illustrated) for forming the upper pole layer
92
through the frame plating method.
The first flattening layer
86
, coil pattern layer
88
, and second flattening layer
90
are laminated in order and then, a resist frame pattern is formed. In this case, a large height difference is formed between the write gap layer
84
and the second flattening layer
90
at the front end portion. Therefore, the film thickness of the resist frame pattern at the front end portion becomes 10 (micron meter) or more and thereby, the accuracy for forming a thin pattern through photo lithography process is deteriorated. Moreover, front end sides of the first flattening layer
86
and second flattening layer
90
are respectively formed like a curved surface. Therefore, light for exposure in photo lithography process reflects on the curved surface and thereby, the vicinity of the ABS plane
76
of the resist frame pattern is easily overexposed.
As a result, the resist frame pattern for forming the front end portion of the upper pole layer
92
has a large film thickness and it is partially overexposed. Thereby, a narrow track pattern cannot be obtained. Thus, to obtain a preferable gap depth D, it is difficult to obtain a preferable front end portion width W.
The second problem is that the high-frequency characteristic is deteriorated to decrease the front end portion width W, that is, the track width. The second problem is described below in detail.
FIGS.
12
(
a
) and
12
(
b
) are illustrations showing magnetic domains of magnetic thin films.
FIG. 13
is a graph showing the frequency dependency of the magnetic permeability of a magnetic thin film. The second problem will be described below by referring to
FIG. 11
to FIG.
13
.
The frequency response of the recording/reproducing characteristic of the thin-film magnetic head
70
greatly depends on the shape of the recording-pole magnetic domain of the head
70
. As shown in FIGS.
12
(
a
) and
Saitho Shinsaku
Toba Tamaki
Urai Haruo
Hayes & Soloway PC
NEC Corporation
Tupper Robert S.
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