Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-03-04
2001-01-16
Scherbel, David A. (Department: 3723)
Metal working
Method of mechanical manufacture
Electrical device making
Reexamination Certificate
active
06173486
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to magnetic heads and in particular to methods of forming magnetic heads with narrow pole widths.
BACKGROUND OF THE INVENTION
A typical inductive thin film magnetic magnetic head comprises a first magnetic pole layer and a second magnetic pole layer with an electrical coil between the two pole layers. The two pole layers contact each other at one end at a back closure to form a continuous magnetic path, with a narrow transducing gap at the other end. The portions of the first and second poles separated by the transducing gap are designated respectively as the first and second pole tips. In order to write data with narrow track widths and high linear recording densities, it is necessary to provide a magnetic head with narrow pole tips. However, there are technical problems associated with fabricating a magnetic head with narrow pole tips. A key problem confronted during manufacture is the alignment of the two pole tips. Various methods have been suggested to solve this problem.
FIG. 1
shows a prior art approach in which a magnetic head
2
is fabricated with a first pole tip
4
wider in lateral dimension than a second pole tip
6
. The wider first pole tip
4
tolerates a certain degree of misalignment during the laying of the second pole tip
6
. The width of the second pole tip TW is intended to define the track width of the magnetic head
2
. However, the problem with this approach is that due to the larger width of the first pole tip
4
, magnetic flux fringing beyond the width of the second pole tip
6
is unavoidable. The fringing flux, such as flux lines F emanating from the second pole
6
to the first pole
4
as shown in
FIG. 1A
, would result in registering a data track
7
with a width W having ambiguous track boundaries. This seriously limits the track-to-track separations on the recording medium
8
.
U.S. Pat. No. 4,947,541, Toyoda et al., entitled “Method For Producing a Thin Film Head”, issued Aug. 14, 1990, describes a magnetic head with a sloped side wall for the second pole tip in an effort to reduce fringing flux lines. As shown in
FIG. 2
herein, the magnetic head
10
includes a first pole
12
and a second pole
14
separated by a gap layer
16
. The second pole
14
has sloped side wall surfaces
14
A and
14
B which diverge away from the first pole tip
12
. The sloped side walls
14
A and
14
B reduce fringing flux between the first and second pole tips
12
and
14
as illustrated by the lower number of flux lines F as shown in FIG.
1
B. Nevertheless, fringing flux still exists and the resultant track width W registered on the medium surface
8
remains ambiguous.
Magnetic heads with vertically aligned side wall pole tips have been described, as in U.S. Pat. No. 5,285,340, Ju et al., entitled “Thin Film Magnetic Head with Conformable Pole Tips”, issued Feb. 8, 1994.
FIG. 3
shows a magnetic head
18
having vertically aligned side walls for both the first and second pole tips
20
,
22
relative to first and second yoke layers
24
and
26
, respectively. With the aligned side walls for the first and second pole tips
20
and
22
, the magnetic head
18
can provide better defined data track width W in comparison with the magnetic heads
2
and
10
shown in
FIGS. 1 and 2
. The aligned first and second pole tips
20
and
22
are made available through a number of intermediate “stitching” steps to the respective first and second yoke layers
24
and
26
. Specifically, in between the pole tip layers
22
and
20
, buffering layers must be interposed in order to maintain magnetic continuity. The intermediate steps incur additional costs of manufacturing.
Storage products, such as disk drives, are now fabricated with relatively small physical sizes and with increased storage capacities. As a consequence, data tracks on the media are registered with much narrower widths and higher linear recording densities. Data tracks written with ambiguous track boundaries seriously affect track-to-track separation, which in turn adversely affects storage capacity. Accordingly, it is desirable to provide magnetic heads capable of writing data tracks with well defined track boundaries, and at reasonable manufacturing costs.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a magnetic head capable of writing narrow data tracks with high linear recording densities.
It is another object of the invention to provide a magnetic head that affords simplicity of fabrication and with reduced manufacturing cost.
In accordance with the invention, a magnetic head is formed with a stack of layers on a substrate. The stack of layers includes a nonmagnetic gap layer sandwiched between a first pole layer, which is disposed atop the substrate, and a sacrificial layer which is preferably made of a metal. A protective layer, such as alumina (Al
2
O
3
), is then deposited over and around the stack of layers. After planarization and ion milling, the sacrificial layer is exposed. The sacrificial layer is thereafter etched away leaving a volume of space in the protective layer and above the nonmagnetic gap layer. After the deposition of an inductive coil with the associated dielectric layers, a second pole layer is then laid with the pole tip deposited in the volume of space, resulting in the first and second pole tips having vertically aligned side walls. With the vertically aligned side walls, the side fringing flux of one pole tip to another is substantially reduced resulting in a magnetic head capable of writing data tracks with well defined boundaries during normal operations.
REFERENCES:
patent: 4550356 (1985-10-01), Hirai et al.
patent: 4947541 (1990-08-01), Toyoda et al.
patent: 5116719 (1992-05-01), Gau
patent: 5138750 (1992-08-01), Amin et al.
Hiner Hugh C.
Hsiao Yun-Lin
Jensen William D.
Ravipati Durga I.
Wang Lien-Chang
Halpern Benjamin M.
Kallman Nathan N.
Read-Rite Corporation
Scherbel David A.
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