Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-09-14
2002-01-15
Letscher, George J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06339524
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a merged MR (magnetoresistive) head having aligned magnetic pole tips, and a method of manufacturing the same.
In a magnetic disk drive, data is read and written by using a magnetic disk medium serving as a storage medium, and a magnetic head having a electromagnetic transducing element mounted on a floating slider floating and supported by the air bearing effect caused by high-speed rotation of the magnetic disk medium.
Recent demands for an internal storage unit or external storage unit of a personal computer and the like increase remarkably, and downsizing, a higher operation speed, and a higher recording density are strongly demanded in a magnetic disk drive.
For this reason, improvements for high performance have been made in the magnetic head serving as the major portion of the magnetic disk drive, the magnetic disk medium, positioning servo, signal processing, and the like. In particular, whereas the magnetic head conventionally performs write (recording) and read (play) with one electromagnetic transducing element, recently, use of a so-called write/read separation type merged MR head is becoming the main stream. The merged MR head uses a conventional inductive element for data write, and an MR element, the output of which does not depend on the speed relative to the magnetic disk medium and which utilizes the magnetoresistive effect, for data read. These two elements are integrated and mounted on one floating slider.
This merged MR head is manufactured by utilizing photolithography technique, and micropatterning technique similar to a semiconductor manufacturing process. For example, Japanese Patent Laid-Open No. 7-262519 (U.S. Pat. No. 5,438,747) discloses a merged MR head and a technique concerning a method of manufacturing the same.
FIGS. 5A
to
5
C show an example of a method of manufacturing a conventional merged MR head.
In order to decrease the side fringe magnetic field generated during recording, the conventional merged MR head has a recording gap layer having the same width as that of an upper magnetic pole and a sidewall aligned with the same plane where the side surface of the upper magnetic pole is present, and the pedestal of a lower magnetic pole/upper shield.
In the method of manufacturing a conventional merged MR head, the recording gap layer and the pedestal of the lower magnetic pole/upper shield are formed to have the same width as that of the upper magnetic pole. For this purpose, the recording gap layer is defined to have the same width as that of the upper magnetic pole by using ion milling and chemical etching. Subsequently, in accordance with ion milling, the pedestal of the lower magnetic pole/upper shield, having the same width as that of the upper magnetic pole and a side surface aligned with the same vertical plane where the side surface of the upper magnetic pole is present, is formed on the lower magnetic pole/upper shield by using the upper magnetic pole as the mask.
FIGS. 5A
to
5
C show the manufacturing method which uses ion milling when defining the recording gap layer to have the same width as that of the upper magnetic pole. A recording gap layer
23
is deposited on a lower magnetic pole/upper shield
22
, and thereafter an upper magnetic pole
24
is formed on the recording gap layer
23
by electroplating using photoresist frame. A portion of the resultant structure other than the vicinity of the upper magnetic pole
24
is covered with a photoresist
26
, and the recording gap layer
23
is defined by ion milling to have the same width as that of the upper magnetic pole
24
.
Since the ion beam etching rate of the recording gap layer
23
is lower than the ion beam etching rate of the upper magnetic pole
24
, when defining the recording gap layer
23
to have the same width as that of the upper magnetic pole
24
, the thickness (height) of the upper magnetic pole
24
decreases largely. More specifically,
FIG. 5A
shows a state before the recording gap layer
23
is etched by ion milling, and
FIG. 5B
shows a state after the recording gap layer
23
is defined by ion milling by using the upper magnetic pole
24
as the mask (the broken line in
FIG. 5B
shows a portion to be etched by ion milling). In
FIG. 5B
, the thickness of the upper magnetic pole
24
is apparently smaller than that in FIG.
5
A.
Subsequently, as shown in FIG
5
C, a pedestal
21
for the lower magnetic pole/upper shield
22
is formed on the lower magnetic pole/upper shield
22
in accordance with ion milling by using the upper magnetic pole
24
as the mask. The pedestal
21
has the same width as that of the upper magnetic pole
24
and is aligned with the same vertical plane where a sidewall or surface
24
s
of the upper magnetic pole
24
is present. In this case, the thickness of the upper magnetic pole
24
further decreases.
In other words,
FIG. 5B
shows a state before the pedestal
21
, aligned with the same vertical plane where the side surface of the upper magnetic pole
24
is present, is defined on the lower magnetic pole/upper shield
22
in accordance with ion milling by using the upper magnetic pole
24
as the mask.
FIG. 5C
shows a state after the pedestal
21
is defined on the lower magnetic pole/upper shield
22
by using the upper magnetic pole
24
as the mask.
In
FIG. 5C
, the sidewall
24
s
of the upper magnetic pole
24
, a sidewall
23
s of the recording gap layer
23
, and a sidewall
21
s
of the pedestal
21
are aligned within the same plane
25
. Similarly, the respective sidewalls on the opposite side (the left-hand side in
FIG. 5C
) are aligned within the same plane.
FIGS. 6A
to
6
C show another example of a conventional merged MR head and a method of manufacturing the same.
A recording gap layer
33
is formed on a lower magnetic pole/upper shield
32
, and thereafter an upper magnetic pole
34
is formed on the recording gap layer
33
by electroplating using photoresist frame. Subsequently, the recording gap layer
33
is defined to have the same width as that of the upper magnetic pole
34
by chemical etching.
In this case, since a chemical etching solution that etches not the upper magnetic pole
34
but the recording gap layer
33
can be selected, the thickness (height) of the upper magnetic pole
34
does not decrease. Subsequently, a pedestal
31
for the lower magnetic pole/upper shield
32
is formed on the lower magnetic pole/upper shield
32
in accordance with ion milling by using the upper magnetic pole
34
as the mask. The pedestal
31
has the same width as that of the upper magnetic pole
34
and is aligned with the same vertical plane as the side surface of the upper magnetic pole
34
. In this case, the thickness of the upper magnetic pole
34
decreases (the broken line in
FIG. 6B
shows a portion to be etched by ion milling).
In the conventional merged MR head manufacturing methods described above, the thickness of the upper magnetic pole becomes undesirably smaller than the thickness necessary to generate a sufficiently strong magnetic field when the merged MR head records a signal on the magnetic recording medium.
The reason for this is as follows. When forming the recording gap layer and the pedestal of the lower magnetic pole/upper shield by ion milling in order to decrease the side fringe magnetic field, the upper magnetic pole serving as the mask during ion milling must be formed thicker in advance by an amount corresponding to the thickness decreased by ion milling. For this purpose, the photoresist required for forming the upper magnetic pole by electroplating using photoresist frame must be formed to have a thickness larger than that of the necessary upper magnetic pole and to have a desired width of the upper magnetic pole. However, as the width of the upper magnetic pole decreases to meet a demand for a higher density, such a photoresist becomes difficult to form.
In the former case, since the ion beam etching rate of the recording gap layer
23
is lower than the ion beam etching rate of the upper magnetic pol
Furusawa Hiroshi
Yamasawa Mitsugu
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