Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-10-04
2001-06-12
Hall, Carl E. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603150, C216S022000, C216S066000
Reexamination Certificate
active
06243939
ABSTRACT:
BACKGROUND OF THE INVENTION
1). Field of the Invention
This invention relates to thin film magnetic heads, and in particular, to a method for fabricating narrow track width write heads comprising poles made of laminated pole-piece material and more particularly to a Ion beam Etch (IBE) process for trimming poles and to a specific material for the pole and write gate material that increases selectivity of the IBE.
2). Description of the Prior Art
Typical magnetic disk drives include a magnetic disk and a read-write head for recording data in and reading data from the disk. It has been a goal of industry to increase the recording density in magnetic disks. In order to achieve this goal, read-write heads have been developed comprising an inductive write element and a magnetoresistive read element. In addition, magnetic disks exhibiting high coercivity and low noise have been developed.
It is known in the art to use “pole-tip trimming” to reduce the write fringing field. (The fringing field is that portion of the magnetic field generated by the write element and extending toward tracks adjacent to the track being written to. It is important to minimize the write fringing field, especially when recording in disks having a high track density (i.e., disks recorded using a narrow pole width) because otherwise, the fringing field might partially erase or garble data in adjacent tracks.
At present, ion beam etching (“IBE”) is the only proven high-volume etching technique for trimming deposited pole-piece layers into poles.
The use of IBE for patterned etching requires a mask to protect the portions of the read-write head that are not to be etched. The most common mask for IBE is photoresist. However, due to relatively low etch selectivity, thick photoresist is required for pole trimming. (Photoresist Etch selectivity refers to the ratio of the rate at which the pole-piece material is etched to the rate at which the photoresist is etched during IBE.) This limits the efficacy of using photoresist as a mask for trimming very narrow poles (e.g. poles with an aspect ratio greater than 2.0). Further, due to thick photoresist mask requirements, “redeposition” and “shadowing” become a severe problem when trimming narrow, high aspect ratio poles. After the photoresist mask is removed, “fencings” or “rabbit ears” remain above the pole-pieces. To minimize the “fencing” problem, a complicated, long ion-milling process, e.g. using multi-angle ion milling and a tedious post-milling photoresist stripping step, is used.
With regard to the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that increased track spacings of magnetic data tracks within magnetic data storage media are required when employing inductive magnetic write heads which exhibit increased write fringe fields bridging their magnetic transducer pole layers. Increased write fringe field widths within inductive magnetic write heads typically result from non-symmetric magnetic pole layers within those inductive magnetic write heads. A schematic cross-sectional diagram of a typical inductive magnetic write head formed with non-symmetric magnetic pole layers is illustrated in FIG.
1
.
Shown in
FIG. 1
is a substrate
10
having formed thereupon a lower magnetic pole layer
12
separated from an upper magnetic pole tip
16
a
within a patterned upper magnetic pole layer
16
by a gap filling dielectric layer
14
. Also shown in
FIG. 1
bridging from the lower magnetic pole layer
12
to the patterned upper magnetic pole layer
16
is a pair of write fringe fields
15
a
and
15
b.
It is also known in the art of magnetic read-write head fabrication that write fringe fields, such as the write fringe fields
15
a
and
15
b
as illustrated in
FIG. 1
, formed incident to non-symmetric magnetic pole layer alignment within inductive magnetic write heads, may be significantly reduced by partially etching the wider of the two non-symmetric magnetic pole layers while employing the narrower of the two non-symmetric magnetic pole layers as a mask to form within the wider of the two non-symmetric magnetic pole layers a pole tip self-aligned with the pole tip within the narrower of the two non-symmetric magnetic pole layers. A schematic cross-sectional diagram illustrating the results of such partial etching practiced upon the lower magnetic pole layer
12
as illustrated in
FIG. 1
is shown in FIG.
2
.
Shown in
FIG. 2
is a partially etched lower magnetic pole layer
12
′ having formed therein a lower magnetic pole tip
12
a
separated from the upper magnetic pole tip
16
a
within a partially etched patterned upper magnetic pole layer
16
′ by a patterned gap filling dielectric layer
14
′. There is also shown in
FIG. 2
bridging from the partially etched patterned upper magnetic pole layer
16
′ to the partially etched lower magnetic pole layer
12
′ a pair of significantly reduced write fringe fields
15
a
′ and
15
b′.
While the inductive magnetic write transducer structure as illustrated in
FIG. 2
typically exhibits significantly reduced write fringe fields in comparison with the inductive magnetic write transducer structure as illustrated in
FIG. 1
, the inductive magnetic write transducer structure as illustrated in
FIG. 2
is typically not formed entirely without difficulties. One of the difficulties typically encountered when forming the inductive magnetic write transducer structure as illustrated in
FIG. 2
is that a substantial portion of the patterned upper magnetic pole layer
16
′ is eroded under circumstances where: (1) the lower magnetic pole layer
12
and the patterned upper magnetic pole layer
16
are both formed of a permalloy (ie: nickel-iron, 80:20 w/w) magnetic material, as is common in the art of magnetic read-write head fabrication, (2) the gap filling dielectric layer
14
is simultaneously formed of an aluminum oxide dielectric material, as is similarly common in the art of magnetic read-write head fabrication; and (3) the magnetic write transducer structure whose schematic cross-sectional diagram is illustrated in
FIG. 2
is etched from the magnetic write transducer structure whose schematic cross-sectional diagram is illustrated in FIG.
1
through an ion beam etch (IBE) method employing argon ions, as is similarly also common in the art of magnetic read-write head fabrication.
The substantial portion of the patterned upper magnetic pole layer
16
is typically eroded due to an ion beam etch (IBE) selectivity of the ion beam etch (IBE) method for the patterned upper magnetic pole layer
16
with respect to the gap filling dielectric layer
14
. Typically, using a N
2
or Ar IBE, the ion beam etch selectivity of the patterned upper magnetic pole layer
16
, when formed of a permalloy magnetic material, with respect to the gap filling dielectric layer
14
, when formed of an aluminum oxide dielectric material, is from about 1:0.3 to about 1:0.6. That is the upper pole (
16
)Permalloy IBE rate is higher than the etch rate of the gap fill dielectric layer
14
.
Problem 1: Erosion of the upper pole: Erosion of upper magnetic pole layers, such as the patterned upper magnetic pole layer
16
, has been noted in the art of inductive magnetic read-write head fabrication, and it is typical in the art of inductive magnetic read-write head fabrication to compensate for the erosion by forming an upper magnetic pole layer with a substantial additional thicknesses beyond the thickness ultimately desired for a partially etched upper magnetic pole layer formed from the upper magnetic pole layer. See, for example, Krounbi et al., U.S. Pat. No. 5,438,747 (col. 11, line 68 to col. 12, line 5). Unfortunately, patterned upper magnetic pole layers, such as the patterned upper magnetic pole layer
16
, formed with substantial additional thicknesses and thus significant aspect ratios, are often diffic
Chang Jei-Wei
Chen Mao-Min
Han Cherng-Chyi
Wu Cheng-Teh
Ackerman Stephen B.
Hall Carl E.
Headway Technologies Inc.
Saile George O.
Stoffel William J.
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