Dynamic magnetic information storage or retrieval – Head – Coil
Reexamination Certificate
1999-09-09
2002-12-17
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Coil
C029S603240
Reexamination Certificate
active
06496330
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to magnetic disk data storage systems, and more particularly to magnetic write transducers and methods of making same.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In
FIGS. 1A and 1B
, a magnetic disk data storage system
10
of the prior art includes a sealed enclosure
12
, a disk drive motor
14
, a magnetic disk
16
, supported for rotation by a drive spindle S
1
of motor
14
, an actuator
18
and an arm
20
attached to an actuator spindle S
2
of actuator
18
. A suspension
22
is coupled at one end to the arm
20
, and at its other end to a read/write head or transducer
24
. The transducer
24
(which will be described in greater detail with reference to
FIG. 2A
) typically includes an inductive write element with a sensor read element. As the motor
14
rotates the magnetic disk
16
, as indicated by the arrow R, an air bearing is formed under the transducer
24
causing it to lift slightly off of the surface of the magnetic disk
16
, or, as its is termed in the art, to “fly” above the magnetic disk
16
. Alternatively, some transducers, known as “contact heads,” ride on the disk surface. Various magnetic “tracks” of information can be written to and/or read from the magnetic disk
16
as the actuator
18
causes the transducer
24
to pivot in a short arc as indicated by the arrows P. The design and manufacture of magnetic disk data storage systems is well known to those skilled in the art.
FIG. 2A
depicts a magnetic read/write head
24
including a substrate
25
above which a read element
26
and a write element
28
are disposed. Edges of the read element
26
and write element
28
also define an air bearing surface ABS, in a plane
29
, which can be aligned to face the surface of the magnetic disk
16
(see FIGS.
1
A and
1
B). The read element
26
includes a first shield
30
, an intermediate layer
32
, which functions as a second shield, and a read sensor
34
that is located within a dielectric medium
35
between the first shield
30
and the second shield
32
. The most common type of read sensor
34
used in the read/write head
24
is the magnetoresistive (AMR or GMR) sensor, which is used to detect magnetic field signals from a magnetic medium through changing resistance in the read sensor.
The write element
28
is typically an inductive write element which includes the intermediate layer
32
, which functions as a first pole, and a second pole
38
disposed above the first pole
32
. The first pole
32
and the second pole
38
are attached to each other by a backgap portion
40
, with these three elements collectively forming a yoke
41
. The combination of a first pole tip portion
43
and a second pole tip portion
45
near the ABS are sometimes referred to as the yoke tip portion
46
. A write gap
36
is formed between the first and second poles
32
and
38
in the yoke tip portion
46
. The write gap
36
is filled with a non-magnetic, electrically insulating material that forms a write gap material layer
37
. This non-magnetic material can be either integral with (as is shown here) or separate from a first insulation layer
47
that lies below the second pole
38
and extends from the yoke tip portion
46
to the backgap portion
40
.
Also included in write element
28
is a conductive coil
48
, formed of multiple winds
49
which each have a wind height Hw. The coil
48
can be characterized by a dimension sometimes referred to as the wind pitch P, which is the distance from one coil wind front edge to the next coil wind front edge, as shown in FIG.
2
A. As is shown, the wind pitch P is defined by the sum of the wind thickness Tw and the separation between adjacent winds Sw. The conductive coil
48
is positioned within a coil insulation layer
50
that lies above the first insulation layer
47
. The first insulation layer
47
thereby electrically insulates the winds
49
from each other and from the second pole
38
.
The configuration of the conductive coil
48
can be better understood with reference to a plan view of the read/write head
24
shown in
FIG. 2B
taken along line
2
B—
2
B of FIG.
2
A. Because the conductive coil extends beyond the first and second poles, insulation may be needed beneath, as well as above, the conductive coil to electrically insulate the conductive coil from other structures. For example, as shown in
FIG. 2C
, a view taken along line
2
C—
2
C of
FIG. 2A
, a buildup insulation layer
52
can be formed adjacent the first pole, and under the conductive coil layer
48
. As will be appreciated by those skilled in the art, these elements operate to magnetically write data on a magnetic medium such as a magnetic disk
16
(see FIGS.
1
A and
1
B). With reference to
FIG. 3
, the coil defines an electrical circuit which can be modeled as a head resistance Rh in series with a head inductance Lh, both of which are in parallel with a head capacitance Ch.
More specifically, an inductive write head such as that shown in
FIGS. 2A-2C
operates by passing a writing current through the conductive coil layer
48
. Because of the magnetic properties of the yoke
41
, a magnetic flux is induced in the first and second poles
32
and
38
by write currents passed through the coil layer
48
. The write gap
36
allows the magnetic flux to fringe out from the yoke
41
(thus forming a fringing gap field) and to cross a magnetic recording medium that is placed near the ABS. A critical parameter of a magnetic write element is a trackwidth of the write element, which defines track density. For example, a narrower trackwidth can result in a higher magnetic recording density. The trackwidth is defined by the geometries in the yoke tip portion
46
(see
FIG. 2A
) at the ABS. These geometries can be better understood with reference to FIG.
2
C. As can be seen from this view, the first and second poles
32
and
38
can have different widths W
1
and W
2
respectively in the yoke tip portion
46
(see FIG.
2
A). In the shown configuration, the trackwidth of the write element
28
is defined by the width W
2
of the second pole
38
. Thus, accurate definition of the trackwidth is critical during the fabrication of the write element.
However, the control of trackwidth, and coil pitch can be limited by typical fabrication processes, an example of which is shown in the process diagram of FIG.
4
A. The method
54
includes an operation
56
of providing a first pole. This operation can include, for example, forming a plating dam, plating and then removing the dam. In an operation
58
, a write gap material layer is formed over the first pole. In particular, the write gap material layer is formed over an upper surface of the first pole. Also, in operation
58
, a via is formed through the write gap material layer to the first pole in the backgap portion
40
(see FIG.
2
A). In the instance herein described, the write gap material layer extends above the first pole in the area between the yoke tip portion and the backgap portion, although in other cases the write gap material layer may not be above this area. A buildup insulation layer is typically formed by depositing (e.g., spinning) and patterning photoresistive material and then hard baking the remaining photoresistive material. Such processes often result in the height of the buildup insulation layer being non-uniform.
In an operation
62
the first coil layer is formed above the write gap material layer and the buildup insulation layer. This can include first depositing a seed layer above the first pole. Typically, photoresistive material can then be deposited and patterned. With the patterned photoresistive material, conductive material can be plated. With removal of the photoresistive material, the remaining conductive material thereby forms the first coil layer.
Unfortunately, when there is a difference in height between the write gap material layer and the buildup insulation layer, the patterning of the photoresistive material for the f
Crue, Jr. Billy W.
Shi Zhupei
Thomas Mark David
Wang Lien-Chang
Carr & Ferrell LLP
Klimowicz William
Read-Rite Corporation
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