Air bearing slider

Details Air bearing slider Air bearing slider

2000-03-06

2002-09-03

Renner, Craig A. (Department: 2652)

Dynamic magnetic information storage or retrieval

Fluid bearing head support

Disk record

C360S235400, C360S235700, C360S236300

Reexamination Certificate

active

06445542

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to methods for fabricating air bearing surfaces of sliders for magnetic disk drives and the sliders so produced.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatus such as computers. In
FIGS. 1A and 1B
, a magnetic disk drive
1
of the prior art includes a sealed enclosure
2
, a disk drive motor
3
, a magnetic disk
4
, supported for rotation by a spindle
5
of motor
3
, an actuator
6
and an arm
7
attached to a spindle
8
of actuator
6
. A suspension
9
is coupled at one end to the arm
7
, and at its other end to a read/write head or slider
10
. The slider
10
typically includes an inductive write element with a sensor read element As the motor
3
rotates the disk
4
, as indicated by the arrow R, a layer of air proximate to the surface of the disk
4
is swept along with the disk
4
. This layer of air, commonly known as windage, pushes against the slider
10
and allows the slider
10
to lift off the surface of the disk
4
and “fly” on an air bearing formed beneath it. Various magnetic “tracks” of information can be read from the magnetic disk
4
as the actuator
6
is caused to pivot in a short arc as indicated by the arrows P. The design and manufacture of magnetic disk drives
1
is well known to those skilled in the art.
FIG. 2
shows a slider
10
of the prior art. The side of the slider
10
facing up in the drawing is the side that faces the disk
4
. Thus, the highest features in the drawing are those that are closest to the disk
4
when the disk drive
1
is in operation. The slider
10
has a generally rectangular shape with a leading edge
20
, a trailing edge
22
, a first side
24
and a second side
26
. Slider
10
further includes an air bearing surface (ABS) comprising a trailing edge pad
28
, a first leading pad
30
and a second leading pad
32
, and in some prior art designs also includes a first side pad
34
and a second side pad
36
. The slider
10
additionally includes a leading edge step
38
, a trailing edge step
40
, and a cavity
42
. In some prior art embodiments the slider
10
also includes a first side step
44
and a second side step
46
.
During manufacture, the slider
10
is etched from a single body, typically made of a two phase mixture of aluminum oxide and titanium carbide. The steps of the manufacturing process are generally illustrated in
FIGS. 3A-3H
and employ photolithography methods that are well known in the art.
FIGS. 3A-3H
show a crosssection of the slider
10
along the line
3
—
3
in FIG.
2
through successive steps. In
FIG. 3A
a body
48
that may have a nominally curved surface is covered with a photoresist layer
50
. The photoresist layer
50
is patterned and developed, and then any undeveloped material is washed away to leave a photoresist mask
52
as shown in FIG.
3
B. Next, the body
48
is etched to remove material that is not protected by the photoresist mask
52
. As shown in
FIG. 3C
, the etching creates a first surface that is recessed below the level of the initial surface by a depth H
1
.
FIG. 3D
shows the formed trailing edge pad
28
after the first photoresist mask
52
is stripped away. The steps of
FIGS. 3A-3D
are then repeated in
FIGS. 3E-3H
. A second photoresist layer
56
is formed over the body
48
as shown in FIG.
3
E. The photoresist layer is formed into a second photoresist mask
58
in
FIG. 3F
, and the body
48
is again etched in
FIG. 3G
to create a second surface recessed below the initial surface by a depth H
2
.
FIG. 3H
shows the slider
10
after the second photoresist mask
58
has been stripped away to reveal the leading edge step
38
and the cavity
42
.
Accordingly, as can be seen in
FIG. 2
, the prior art provides for two etching steps to create features at three different heights. The pads
28
,
30
,
32
,
34
, and
36
that form the ABS represent the only portions of the initial surface that remain after the two etching operations. The steps
38
,
40
,
44
, and
46
all are recessed beneath the ABS by a depth of H
1
, while the cavity
42
is recessed beneath the ABS by a depth of H
2
.
During operation of the disk drive
1
air that is swept along with the spinning disk
4
, commonly known as windage, first encounters the leading edge
20
, and leading edge pads
30
,
32
and leading edge step
38
. As the air flow passes between the leading edge pads
30
,
32
and the disk
4
a lifting force is developed that tends to drive the slider
10
away from the disk
4
. Another portion of the air flow, however, passes through a gap
60
between the leading edge pads
30
,
32
, over the leading edge step
38
, and over the cavity
42
. As the air expands over cavity
42
the pressure drops and a partial vacuum is developed that tends to draw the slider
10
towards the disk
4
. In stabile flight, the downward force and the upward force are in equilibrium and the slider
10
maintains a generally constant height above the disk
4
, commonly known as the fly height (FH).
FIG. 4
illustrates an attitude of a slider
10
in stabile flight over a disk
4
. The drawing shows how the slider
10
flies with the leading edge
20
elevated relative to the trailing edge
22
such that the plane defined by the ABS forms an angle &agr; to the disk
4
. The fly height, FH, of the slider
10
is typically defined as the distance between the trailing edge
22
and the disk
4
since the transducer is commonly located along the trailing edge
22
adjacent to the trailing pad
28
. Pads
28
,
34
,
36
of the ABS are designed to cooperate with the leading edge pads
30
,
32
to regulate, for example, the pressure drop experienced over the cavity
42
. The combination of the pads
28
,
30
,
32
,
34
,
36
and the steps
38
,
40
,
44
,
46
also influences the angle &agr;, also known as the pitch, the degree of rotation around the longitudinal line
33
known as roll, and the resistance slider
10
exhibits to changes in its flight characteristics, commonly referred to as stiffness. Stiffness with respect to fly height is especially desirable, but additionally stiffness is also desirable with respect to pitch and roll.
In prior art designs, in order to increase the pitch angle of a slider, the combined surface area of the leading edge pads
30
,
32
is increased at the expense of the surface area of the cavity
42
. Increasing the surface area of the leading edge pads
30
,
32
creates greater lift under the leading edge
20
causing the pitch to rise. Reducing the cavity surface area, however, reduces the volume enclosed by the cavity surface and the surrounding pads and steps. It has been found that reducing this volume also reduces the stiffness of the slider in flight. Therefore, in the prior art raising the pitch angle has been found to result in a tradeoff in stiffness.
Another well known configuration for a slider
10
, commonly referred to as side rail design, positions the trailing pad
28
and the transducer (not shown) close to either first side
24
or second side
26
of the slider
10
. A slider
10
with a side rail design preferably will have a controlled degree of roll so that the side
24
or
26
nearest to the transducer will be closest to the disk
4
.
As will be appreciated by those skilled in the art, the dimensions of the various features of slider
10
are carefully designed to control flight characteristics such as fly height, pitch, roll, and their respective stiffnesses. It will also be appreciated that the design process must also take into account factors such as the rotation rate of the disk
4
and the need to avoid the accumulation of debris on the slider
10
. Modifications to the dimensions of the various features in the design process necessarily creates tradeoffs in the flight characteristics of slider
10
. For example, increasing the size of the cavity
42
at the expense of the size of the leading edge pads
30
,
32
will tend to cause the slider
10
to fly closer to the disk
4
.
Further, during the ma

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