U.S. patent application number 10/062160 was filed with the patent office on 2002-09-05 for patterned and directional selective roughening of a slider air-bearing surface.
This patent application is currently assigned to Seagate Technology, Inc.. Invention is credited to Alodan, Maher Abdullah, Boutaghou, Zine Eddine, Burbank, Daniel Paul, Egbert, Dale Eugene, Stover, Lance Eugene.
Application Number | 20020122275 10/062160 |
Document ID | / |
Family ID | 26761010 |
Filed Date | 2002-09-05 |
United States Patent
Application |
20020122275 |
Kind Code |
A1 |
Stover, Lance Eugene ; et
al. |
September 5, 2002 |
Patterned and directional selective roughening of a slider
air-bearing surface
Abstract
An information handling system, such as a disk drive, including
a base, a disk stack rotatably attached to the base, and an
actuator assembly movably attached to the base. The actuator
assembly also includes a load spring and a slider attached to said
load spring. The slider and load spring are attached to form a
gimballing connection between the slider and the load spring. The
slider includes an air-bearing surface which has a contact area.
The slider also includes a transducer. The transducer is typically
located near said contact area. The contact area includes a
roughened surface portion and a smooth surface portion. The smooth
surface portion is adjacent the transducer. The roughened surface
portion is rougher than the smooth surface portion. The roughened
surface portion is also rougher than the other surfaces associated
with the air-bearing surface of the slider. The roughened surface
portion of the contact area is formed by one of several techniques.
One of the techniques uses a wet etch to remove at least one of the
phases of a multi-phase material. Another technique defines the
area to be roughened using photolithography. After exposing the
photoresist using either a mask or a laser, a portion of
photoresist is removed and the areas unprotected by photoresist are
dry etched to form the roughened contact area.
Inventors: |
Stover, Lance Eugene; (Eden
Prairie, MN) ; Alodan, Maher Abdullah; (Bloomington,
MN) ; Burbank, Daniel Paul; (Minneapolis, MN)
; Egbert, Dale Eugene; (Deephaven, MN) ;
Boutaghou, Zine Eddine; (Vadnais Heights, MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Seagate Technology, Inc.
|
Family ID: |
26761010 |
Appl. No.: |
10/062160 |
Filed: |
January 31, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10062160 |
Jan 31, 2002 |
|
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|
09246920 |
Feb 9, 1999 |
|
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6366429 |
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60078844 |
Mar 20, 1998 |
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Current U.S.
Class: |
360/234.3 ;
369/300; G9B/5.23 |
Current CPC
Class: |
G11B 5/6005
20130101 |
Class at
Publication: |
360/234.3 ;
369/300 |
International
Class: |
G11B 007/00; G11B
021/20; G11B 017/32; G11B 015/64; G11B 005/60 |
Claims
What is claimed is:
1. A method for treating a contact portion of the air-bearing
surface of a slider, said air-bearing surface including a
transducer, said method comprising: forming a slider having a
contact area made of a multi-phase material; and etching the
multi-phase material in the contact area to form a roughened
surface.
2. The method of claim 1 wherein forming a slider having a contact
area made of a multi-phase material further comprises: removing a
portion of the contact area of the air-bearing surface; depositing
the multi-phase material on the portion of the contact area.
3. The method of claim 2 wherein depositing the multi-phase
material on the portion of the contact area includes depositing the
multi-phase material until the thickness of the multi-phase
material is equal to or greater than the thickness of the portion
of the contact area removed from the air-bearing surface.
4. The method of claim 1 wherein the transducer is masked.
5. The method of claim wherein forming a slider having a contact
area made of a multi-phase material includes selecting a grain size
of at least one phase of the multi-phase material.
6. The method of claim 1 wherein etching the multi-phase material
in the contact area to form a roughened surface further comprises
applying a phase-sensitive etchant to the multi-phase material to
remove a portion of at least one of the phases of the multi-phase
material.
7. The method of claim 6 wherein applying a phase-sensitive etchant
to the multi-phase material to remove a portion of at least one of
the phases of the multi-phase material includes applying the
phase-sensitive etchant at a selected concentration for a selected
time.
8. A method for treating a contact portion of the air-bearing
surface of a slider, said slider including a transducer, said
method comprising: adding a layer of photoresist to the contact
surface of the air-bearing surface; exposing a portion of the
photoresist; removing a portion of the photoresist; and etching the
portion of the contact surface uncovered by photoresist to form a
roughened contact surface.
9. The method of claim 8 wherein exposing a portion of the
photoresist further comprises exposing the photoresist to a light
pattern in a first direction; and exposing the photoresist to a
light pattern in a second direction.
10. The method of claim 9 further comprising rotating the contact
area of the slider between a first position and a second position,
said photoresist exposed to a light pattern in a first direction at
the first position and said photoresist exposed to a light pattern
in a second direction at the second position.
11. The method of claim 10 wherein the first position is 90 degrees
from the second position.
12. The method of claim 9 wherein exposing the photoresist to a
light pattern in a first direction further comprises: emitting
light from a laser; splitting the emitted light from the laser to
form a first laser beam and a second laser beam; directing the
first laser beam to the contact area; and directing the second
laser beam to the contact area so that the first laser beam and the
second laser beam interfere.
13. The method of claim 9 further comprising: removing a portion of
the photoresist; and etching the contact area, said portions of the
contact area having the photoresist removed being etched to form a
pattern.
14. The method of claim 8 wherein etching the contact area
comprises plasma etching the exposed portions of the contact
area.
15. The method of claim 9 further comprising varying the duration
of time the contact area is exposed to the plasma etching.
16. A slider for a disk drive information handling system
comprising: a transducer associated with the slider; an air-bearing
surface further comprised of: a contact surface; and a non-contact
surface, at least a portion of the contact surface positioned near
the transducer associated with the slider; and means for reducing
stiction associated with said contact surface.
17. The slider of claim 16 wherein means for reducing stiction
includes a roughened contact surface.
18. The slider of claim 17 wherein the roughened contact surface is
formed using photolithography and dry plasma etching.
19. The slider of claim 17 wherein the roughened contact surface is
formed using a phase-selective etchant.
20. The slider of claim 17 wherein the roughened contact surface
has a surface roughness, R.sub.a, defined by the center line
average of asperity heights in the range of 0.25 nm to 1000 nm.
21. The slider of claim 17 wherein the roughened contact surface
has a surface roughness, R.sub.a, defined by the center line
average of asperity heights in the range of 1 nm to 12 nm.
22. The method of claim 2 wherein depositing the multi-phase
material on the portion of the contact area includes depositing
material on an area corresponding to at least one of the rails of
the slider.
23. The method of claim 2 wherein depositing the multi-phase
material on the portion of the contact area includes depositing
material on an area near the trailing edge of the slider.
24. The method of claim 2 wherein depositing the multi-phase
material on the portion of the contact area includes depositing
material on an area near the trailing edge of the slider and
associated with the center pad of the slider.
25. The method of claim 8 wherein depositing the multi-phase
material on the portion of the contact area includes depositing
material on an area corresponding to at least one of the rails of
the slider.
26. The method of claim 8 wherein depositing the multi-phase
material on the portion of the contact area includes depositing
material on an area near the trailing edge of the slider.
27. A method of forming a slider comprising etching a portion of
the air bearing surface corresponding to the portion of the air
bearing surface which contacts a substantially smooth surface to
form a roughened surface which has lesser stiction forces than a
non roughened contact surface.
Description
RELATED APPLICATION
[0001] This application is a division of U.S. application Ser. No.
09/246,920, filed Feb. 9, 1999, which claims the benefit of U.S.
Provisional Application Serial No. 60/078,844, filed Mar. 20, 1998
under 35 USC119(e).
FIELD OF THE INVENTION
[0002] The present invention relates to the field of mass storage
devices. More particularly, this invention relates to a disk drive
which includes a slider having a roughened air-bearing surface.
BACKGROUND OF THE INVENTION
[0003] One of the key components of any computer system is a place
to store data. One common place for storing data in a computer
system is on a disk drive. The most basic parts of a disk drive are
a disk that is rotated, an actuator that moves a transducer to
various locations over the disk, and electrical circuitry that is
used to write and read data to and from the disk. The disk drive
also includes circuitry for encoding data so that it can be
successfully retrieved and written to the disk surface. A
microprocessor controls most of the operations of the disk drive as
well as passing the data back to the requesting computer and taking
data from a requesting computer for storing to the disk. The
magnetic transducer translates electrical signals into magnetic
field signals that actually record the data "bits."
[0004] The transducer is typically housed within a small ceramic
block called a slider. The slider is passed over the rotating disk
in close proximity to the disk. The transducer can be used to read
information representing data from the disk or write information
representing data to the disk. When the disk is operating, the disk
is usually spinning at relatively high revolutions per minute
("RPM"). A current common rotational speed is 7200 RPM. Rotational
speeds in high-performance disk drives are as high as 10,000 RPM.
Higher rotational speeds are contemplated for the future.
[0005] The slider is usually aerodynamically designed so that it
flies on the cushion of air that is dragged by the disk. The slider
has an air-bearing surface ("ABS") which includes rails and a
cavity between the rails. The air-bearing surface is that surface
of the slider nearest the disk as the disk drive is operating. Air
is dragged between the rails and the disk surface causing an
increase in pressure which tends to force the head away from the
disk. Simultaneously, air rushing past the depression in the
air-bearing surface produces a lower than ambient pressure area at
the depression. This vacuum effect counteracts the pressure
produced at the rails. The opposing forces equilibrate so the
slider flies over the surface of the disk at a particular fly
height. The fly height is the thickness of the air lubrication film
or the distance between the disk surface and the transducing head.
This film minimizes the friction and resulting wear that would
occur if the transducing head and disk were in mechanical contact
during disk rotation.
[0006] The best performance of the disk drive results when the
slider is flown as closely to the surface of the disk as possible.
In operation, the distance between the slider and the disk is very
small; currently "fly" heights are about 1-2 micro inches.
[0007] Information representative of data is stored on the surface
of the memory disk. Disk drive systems read and write information
stored on tracks on memory disks. Transducers, in the form of
read/write heads attached to the sliders, located on both sides of
the memory disk, read and write information on the memory disks
when the transducers are accurately positioned over one of the
designated tracks on the surface of the memory disk. The transducer
is also said to be moved to a target track. As the memory disk
spins and the read/write head is accurately positioned above a
target track, the read/write head can store data onto a track by
writing information representative of data onto the memory disk.
Similarly, reading data on a memory disk is accomplished by
positioning the read/write head above a target track and reading
the stored material on the memory disk. To write on or read from
different tracks, the read/write head is moved radially across the
tracks to a selected target track. The data is divided or grouped
together on the tracks. In some disk drives, the tracks are a
multiplicity of concentric circular tracks. In other disk drives, a
continuous spiral is one track on one side of a disk drive. Servo
feedback information is used to accurately locate the transducer.
The actuator assembly is moved to the required position and held
accurately during a read or write operation using the servo
information.
[0008] One of the most critical times during the operation of a
disk drive occurs just before the disk drive shuts down or during
the initial moment when the disk drive starts. When shutdown
occurs, the slider is typically flying over the disk at a very low
height. Just before shutdown, the slider is moved to a non-data
containing area of the disk where it is landed. During landing, the
slider skids to a stop. When the disk drive starts, the slider
skids across the non-data containing portion of the disk until the
velocity of the slider is sufficient to produce lift between the
slider and the disk.
[0009] In the past, the surface of the disk was textured to keep
contact points between the disk and the slider to a minimum.
Currently, it has been found that disks with smooth surfaces have
better magnetic characteristics. The recording density of the disk
is highest when the spacing between the transducing head and the
magnetic layer is minimized. By reducing the roughness or texturing
on the disk, the spacing between the transducing head and the
magnetic layer on the disk can also be reduced. When smooth sliders
are landed on disks formed with a smooth surface, problems occur.
One of the larger problems is that a stiction force occurs between
the slider and the disk surface. Stiction is static friction and is
proportional to the size of a meniscus formed by the lubricant on
the disk. When a smooth slider lands on a smooth disk, the stiction
forces are high. In some instances, the stiction forces may cause
the slider to separate from the suspension. In other words, the
stiction forces are so high that the slider rips from the
suspension to which it is mounted.
[0010] One solution includes reducing the contact area of the
air-bearing surface. However, even when this is done, frictional
forces due to stiction remain and affect the performance of the
air-bearing surface and slider. Evidence of air-bearing instability
has been observed.
[0011] Thus, there is a need for a method and apparatus for
reducing the stiction forces produced between the surface of the
disk and the slider. There is also a need for a method and
apparatus that allows for use of a smooth disk so that the spacing
between the transducing head associated with the slider and the
disk can be controlled and kept to a minimum to provide for an
enhanced recording density of the information stored on the disk.
There is also a need for a method and apparatus that provides for
reduced stiction forces and yet still provides a stable air-bearing
surface and slider. The method must also produce an air-bearing
that is rugged and durable enough to last for the life of the disk
drive. The method and apparatus must also be made of materials with
minimal outgassing so that contaminants will not be added to the
disk drive enclosure which could contaminant the lubricant on the
disk.
SUMMARY OF THE INVENTION
[0012] An information handling system, such as a disk drive,
includes a base, a disk stack rotatably attached to the base, and
an actuator assembly movably attached to the base. The actuator
assembly also includes a load spring and a slider attached to said
load spring. The slider and load spring are attached to form a
gimballing connection between the slider and the load spring. The
slider includes an air-bearing surface which has a contact area.
The slider also includes a transducer. The transducer is typically
located near said contact area. The contact area includes a
roughened surface portion and a smooth surface portion. The smooth
surface portion is adjacent the transducer. The roughened surface
portion is rougher than the smooth surface portion. The roughened
surface portion is also rougher than the other surfaces associated
with the air-bearing surface of the slider.
[0013] The roughened surface portion of the contact area is formed
in one of several ways. If the slider is comprised of a multi-phase
material, a selective etchant can be applied to the contact area
for a selected amount of time. The selective etchant will act to
remove a portion of at least one of the phases of the material and
will be less active or inactive in removing at least another of the
phases of the material. The amount of material removed using the
selective etchant will be determined by the concentration of the
etchant as well as the amount of time the etchant is left on the
surface of the multi-phase material. The grain size of the
materials used in the multi-phase material can also be used to
determine the surface roughness of the contact portion. If the body
of the slider is made of a single-phase material, this technique
requires removal of a portion of the contact area of the
air-bearing surface. The next step includes depositing an etchable
multi-phase material on the portion of the contact area. The
selective etchant is then applied to the multi-phase material at
the contact area. At least one of the phases is removed by the
selective etchant to form a roughened surface. The selective
etchant is typically a wet or chemical etchant that reacts with one
of the phases of the multi-phase material.
[0014] The other process is a dry process that can be used on any
material. Photoresist is applied to the contact area. The
photoresist is exposed and developed in certain areas to form a
defined pattern across the contact area. Dry etch removal
techniques are then used to remove material of the slider such that
the defined pattern is transferred onto the slider. The
photolithography technique using a dry etch works on both
single-phase and multi-phase materials.
[0015] Advantageously, a roughened portion of the contact surface
reduces the stiction forces produced between the surface of the
disk and the slider and allows landing of a slider onto a smooth
disk. Furthermore, since a smooth disk can be used the spacing
between the transducing head associated with the slider and the
disk can be controlled and minimized to provide for an enhanced
recording density of the information stored on the disk. The
roughened contact area of the air-bearing surface not only reduces
stiction forces between the disk and the slider, but also provides
a stable air-bearing surface for the slider. The resulting
air-bearing is rugged and durable. The materials used to form the
roughened surface are removed so the only materials remaining are
those already in the drive. Thus, outgassing problems are
minimal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an exploded view of a disk drive with a multiple
disk stack and a ramp assembly for loading and unloading
transducers to and from the surfaces of the disks.
[0017] FIG. 2 is a perspective view of a load spring and an
attached slider which form a head gimbal assembly.
[0018] FIG. 3A is a bottom view of a slider showing the air-bearing
surface with a center island.
[0019] FIG. 3B is a bottom view of a slider showing the air-bearing
surface having extended side rails and without a center island.
[0020] FIG. 4 is a flow chart showing the steps in applying the wet
etch surface treatment to contact areas of the air-bearing surface
of the slider.
[0021] FIG. 5A is a cutaway side view along line 5A-5A of the
center island portion of the slider air-bearing surface shown in
FIG. 5B.
[0022] FIG. 5B is a top view of the center island portion of the
slider air-bearing surface after roughening.
[0023] FIG. 6A is a cutaway side view along line 6A-6A of the
center island portion of the slider air-bearing surface shown in
FIG. 6B.
[0024] FIG. 6B is a top view of the center island portion of the
slider air-bearing surface after having a portion of the center
island removed.
[0025] FIG. 7 is a cutaway side view of the center island portion
of the slider air-bearing surface after a two-phase material has
been deposited therein.
[0026] FIG. 8 is a cutaway side view of the center island portion
of the slider air-bearing surface after applying a phase-selective
etchant to remove a portion of the two-phase material.
[0027] FIG. 9 is a set of graphs comparing the surface roughness
before etching and after applying a phase-selective etchant to
remove a portion of the two-phase material.
[0028] FIGs. 10A-10D show cross-sectional views of successive
process steps for applying a surface treatment using
photolithography and a dry or plasma etch to portions of the
contact areas of the air-bearing surface of the slider in
accordance with an embodiment of the invention.
[0029] FIG. 11 is a schematic of an apparatus used to expose the
photoresist to apply a fine-pitched surface treatment to the
slider.
[0030] FIG. 12 is a schematic view of a computer system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] In the following detailed description of the preferred
embodiments, reference is made to the accompanying drawings which
form a part hereof, and in which are shown by way of illustration
specific embodiments in which the invention may be practiced. It is
to be understood that other embodiments may be utilized and
structural changes may be made without departing from the scope of
the present invention.
[0032] The invention described in this application is useful with
all mechanical configurations of disk drives having either rotary
or linear actuation. In addition, the invention is also useful in
all types of disk drives including hard disk drives, zip drives,
floppy disk drives and any other type of drives where unloading the
transducer from a surface and parking the transducer may be
desirable. FIG. 1 is an exploded view of one type of a disk drive
100 having a rotary actuator. The disk drive 100 includes a housing
or base 112, and a cover 114. The base 112 and cover 114 form a
disk enclosure. Rotatably attached to the base 112 on an actuator
shaft 118 is an actuator assembly 120. The actuator assembly 120
includes a comb-like structure 122 having a plurality of arms 123.
Attached to the separate arms 123 on the comb 122, are load beams
or load springs 124. Load beams or load springs are also referred
to as suspensions. Attached at the end of each load spring 124 is a
slider 126 which carries a magnetic transducer 150. The slider 126
with the transducer 150 form what is many times called the head. It
should be noted that many sliders have one transducer 150 and that
is what is shown in the figures. It should also be noted that this
invention is equally applicable to sliders having more than one
transducer. Also attached to the load spring is a load tang 152.
The load tang 152 is used for loading sliders 126 to the disk 134
and unloading the sliders 126 from the disk. On the end of the
actuator arm assembly 120 opposite the load springs 124 and the
sliders 126 is a voice coil 128.
[0033] Attached within the base 112 is a pair of magnets 130 and
130'. The pair of magnets 130 and 130', and the voice coil 128 are
the key components of a voice coil motor which applies a force to
the actuator assembly 120 to rotate it about the actuator shaft
118. Also mounted to the base 112 is a spindle motor. The spindle
motor includes a rotating portion called the spindle hub 133. In
this particular disk drive, the spindle motor is within the hub. In
FIG. 1, a number of disks 134 are attached to the spindle hub 133.
In other disk drives a single disk or a different number of disks
may be attached to the hub. The invention described herein is
equally applicable to such other disk drives.
[0034] FIG. 2 is a perspective view of a load spring 124 and
attached slider 126 which form a head gimbal assembly 200. The load
spring 124 is a triangular structure which acts as a cantilevered
spring to place a small load onto the slider 126 when the slider
126 is in transducing relation with the disk 134. Load springs 124
are also commonly called load beams or suspensions by many in the
disk drive industry. The load spring 124 is attached at its wider
end to an actuator arm 123. The load spring 124 shown in FIG. 2 has
a swage opening 210 and a swage plate 212 in the wider end. The
swage opening 210 and swage plate 212 are used to attach the load
spring 124 by a process referred to as swaging. Other attachment
methods may also be used without departing from the spirit of this
invention. Also attached to the load spring 124 is the slider 126.
The transducer 150 is carried by or within the slider 126.
[0035] Moving the actuator assembly 120 moves all the load springs
124. In operation, the actuator assembly 120 is moved to a park
position when the disk drive is powered down. Moving the actuator
to the park position causes the sliders to move to a non-data area
of the disk. The non-data area is typically at the inner diameter
("ID") of the disk 134. Once the actuator assembly 120 has moved
the sliders 126 to the park position, the disk drive is powered
down and the sliders land on the non-data area and skid to a halt.
When the disk drive is powered on, the disks 134 are quickly
accelerated until a relative velocity between the sliders 126 and
the disk 134 is produced which causes the slider to lift off the
surface of the disk 134. Once lift off of the slider 126 has
occurred, the actuator assembly can be used to move the sliders 126
into an operating or transducing position over the area of the disk
used to store information representative of data. The actuator
assembly 120 can also be used to perform seeks to various data
locations on the surface of the disk.
[0036] FIG. 3A is a bottom view of a slider 126 showing an
air-bearing surface 300. The air-bearing surface includes a center
island 310, a first side rail 320 and a second side rail 322. The
air-bearing surface 300 includes contact portions which contact the
disk 134 during take-off and landing of the slider 126 and
noncontact portions which do not normally contact the disk 134. The
center island 310 is a contact portion 330. Other portions of the
air-bearing surface such as the side rails 320 and 322 may also be
contact portions. A cavity is typically formed between the side
rails 320 and 322 as well as the center island 310. The cavity 340
is a noncontact portion of the air-bearing surface 300. The slider
also has a leading edge 360 and a trailing edge 370. Positioned at
or near the trailing edge 370 is the transducer 150. As shown in
FIG. 3A, the transducer fits within a slot 152 within the center
island 310.
[0037] FIG. 3B is a bottom view of a slider 126' which has an
air-bearing surface 300 with a slightly different design. In FIG.
3B, the side rails 320 and 322 are extended when compared to the
air-bearing surface 300 shown in FIG. 3A. The air-bearing surface
300 shown in FIG. 3B does not include a center island portion. A
cavity or depression 340 is formed between the first rail 320 and
the second rail 322. The first rail 320 and the second rail 322
form the contact portion of the air-bearing surface 300'. The
air-bearing surface 300' also includes a leading edge 360' and a
trailing edge 370'. A transducer 150 is positioned near the
trailing edge 370' of the slider 126' and at or near the surface of
the first rail 320'. In some designs a transducer 150' may also be
added to the second side rail 322'. The second transducer 150' is
similarly positioned in the second side rail 322'. The leading edge
360' may include a leading edge taper 362 on the first side rail
320' and a leading edge taper 364 on the second side rail 322'. In
each of FIGS. 3A and 3B, a portion of the contact surface of the
air-bearing surface 300 or 300' is roughened, as depicted by
reference numerals 380 in FIG. 3A and as depicted by reference
numerals 382 and 384 in FIG. 3B. By roughening a portion of the
contact surface of the air-bearing 300 or 300', the stiction forces
between the slider 126 or 126' and the disk 134 are reduced when
compared to a slider without a roughened contact surface.
[0038] It should be noted that only a portion of the contact
surface 380, 382 or 384 needs to be roughened. The reason only a
portion of the contact surface needs to be roughened is because the
side rails 320 and 322 may include pads or patterns of diamond-like
carbon, which are used to minimize stiction between the side rails
320 and 322 of the air-bearing surface 300 and the disk 134. These
diamond-like carbon pads are generally placed so that they will not
interfere with the spacing between the transducer 150 and the disk.
As a result, the diamond-like pads will not interfere with the
contact surface, such as 380, which is near the transducer 150. If
the contact pads were placed too close to the transducer, the
flying height of the transducer with respect to the disk 134 would
be changed. Adding a roughened surface, such as 380, 382 or 384,
reduces the stiction at the contact surface where there are no pads
near the contact surface. The placement of the pads, as well as the
pads themselves, are discussed in U.S. patent application Ser. No.
09/188,400, entitled, "CAPPED POLYMERIC LOAD/UNLOAD PADS" which is
assigned to Seagate Technologies, Inc., and also filed on a date
even herewith.
[0039] There are several methods used to form a roughened contact
surface, such as 380, 382, or 384. A random pattern of roughening
can be formed by using a phase-selective etchant on a multi-phase
material. A dry plasma etch can be used on any material and forms a
more regular roughened pattern. These various techniques will now
be discussed in the below paragraphs.
[0040] Sliders 126 and 126' have typically been made out of a
multi-phase material. Sliders are made from a ceramic aluminum
titanium carbide (AlTiC). A multi-phase material means that there
is more than one component or phase of the material. For example,
in a slider made of AlTiC, one of the components is the titanium
carbide (TiC). Although sliders 126 have been made of multi-phase
material in the past, sliders made of a single-phase material are
being contemplated. Formation of Roughened Surface on a Slider Made
of Multi-Phase Material In one preferred embodiment, the entire
slider 126 is made of a multi-phase material, such as AlTiC and a
phase-selective etchant is applied to a portion of the contact
surface 380, 382 or 384 to produce a roughened surface. FIG. 4 is a
flow diagram showing the steps in roughening an air-bearing surface
300 or 300' using this method. The initial step in using this
method is to select the grain size of the components of a
multi-phase material, as depicted by 410. AlTiC is a multi-phase
material. The grain size of one of the phases is selected to
determine the coarseness or roughness of the contact area 380, 382,
or 384. In other words, the coarser the grain size, the rougher the
contact area 380, 382 or 384 will be. Next, the slider contact
surface 380, 382 or 384 is formed with the multi-phase material as
shown by 412. The slider contact surface 380, 382 or 384 can be
formed either by forming the entire slider out of a multi-phase
material or, in the alternative, a portion of the contact surface
can be removed and replaced with a multi-phase material. Next, a
phase-selective etchant is applied to at least a portion of the
slider contact surface 380, 382, or 384. The phase-selective
etchant removes at least one component of the multi-phase material
over time. For example, the phase-selective etchant such as nitric
acid (HNO.sub.3) is used to preferably etch the titanium carbide
(TiC) from the AlTiC slider to cause the contact surface to develop
a roughness greater than the original surface. The roughness can be
controlled by controlling the concentration of the phase-selective
etchant, as well as the amount of time the phase-selective etchant
is applied to the multi-phase material, as shown by 414 in FIG. 4.
In other words, if deeper grooves are to be made, a phase-selective
etchant can be left on the contact area to be roughened, 380, 382
or 384 for a long time. Alternatively, the concentration of the
phase-selective etchant can be increased so that the
phase-selective etchant removes one of the components of the
phase-selective material more quickly over the same amount of time.
Once the phase-selective etchant has been applied to the contact
surface 380, 382, or 384 for the selected amount of time, the
phase-selective etchant is removed as shown by 416.
[0041] FIGs. 5A and 5B show the result of applying a
phase-selective etchant to a multi-phase material. A center island
310 having a roughened contact surface 380 is shown in FIGS. 5A and
5B. It should be noted that other types and shapes of roughened
surfaces could also be shown, such as the extended rail slider
air-bearing surface 300' shown in FIG. 3B. It should also be
understood that the surface treatment is equally applicable to all
types of contact surfaces, 380, 382 and 384. The contact surface
330 that results is comprised of a roughened surface 380 and a
smooth surface 500 which is positioned around the transducer 150.
The transducer 150 is positioned within a slot 152 within the
contact surface 330. The smooth portion 500 of the contact surface
330 is around the transducer 150 and the slot 152 in the contact
surface 330. The transducer 150 is typically a magneto-resistive
element used to read information from the disk. The slider 126 or
126' typically will have a write element, such as a thin film
transducer, which is attached to the trailing edge 370 of the
slider 126.
[0042] The roughened surface 380 of the contact surface 330 that
results is a plurality of pebble-shaped elements 510. The
pebble-shaped elements 510 are random in their orientation as well
as in their spacing. The height of the pebble-shaped elements 510
is determined by the grain size of the phase of the multi-phase
material which is unaffected or not as affected by the
phase-selective etchant, the concentration of the phase-selective
etchant, as well as the amount of time the phase-selective etchant
is applied to the contact surface 330. By varying these factors,
the size of the pebble-shaped elements 510 can be varied.
[0043] Formation of Roughened Surface Using Slider Made of a
Single-Phase Material
[0044] As mentioned previously, it is contemplated that sliders 126
or 126' may be made with a single-phase material, such as a
single-phase ceramic. Initially, a portion of the center island 310
is removed, as shown by FIGS. 6A and 6B. FIG. 6A is a cut-away side
view along 6A of the center island portion 310 of the slider
air-bearing surface 300 shown in 6B. FIG. 6B is a top view of the
center island portion 310 of the slider 126 air-bearing surface 300
after a portion of the center island 310 has been removed. The
portion 600 that has been removed is also shown by dotted lines in
FIG. 6A. The portion 600 that is removed forms a depression 601 on
the center island 310. The material removed from the center island
310 to form the depression 601 is typically removed by ion
milling.
[0045] As shown in FIG. 7, a two-phase material 700 is deposited
onto or into the depression 601. Again, the grain size of the
multi-phase material can be selected to control the resulting
roughness of the contact surface. As can be seen, the multi-phase
material 700 is deposited to a height which is greater than the
height of the original material which was removed. In other words,
the multi-phase material 700 is added until the height of the
material is higher than the transducer 150.
[0046] A phase-selective etchant is then applied to the multi-phase
material 700 for a selected amount of time and at a selected amount
of concentration. FIG. 8 is a cutaway side view of the center
island portion 310 of the air-bearing surface 300 after applying a
phase-selective etchant to remove a portion of the two-phase
material. The resultant structure is a series of pebble-shaped
elements 510. The height of the pebble-shaped elements 510 is
higher than the height of the portion of the contact surface in
which the transducer 150 is positioned. Of course the height
difference in FIG. 8 between the needle-like elements 510 and the
surface in which the transducer 150 is positioned is exaggerated.
However, an additional amount of protrusion of the texture with
respect to the smooth surface 500 may be desirable to prevent the
transducer 150 from contacting the disk surface 134.
[0047] The result is a contact surface 380 which is rougher than
the original surface. FIG. 9 shows a graph of the "Z" distance
shown on the "Y" axis versus the "X" distance in two instances. The
original line modulates around 0 and is graphed as shown. The other
line shown is the "Z" distance versus the "X" distance for the
contact surface 380 after it has been etched using a
phase-selective etchant. Average values of some of the surface
roughness parameters are provided in the following table.
1 Ra Rq- R .eta. Surface Roughness Parameter- (nm) (nm) (.mu.m)
(.mu.m.sup.-2) Original 2.0 2.3 2.5 10.0 0.058 Etched 9.0 11.0 0.8
5.0 0.044 Where Ra = center line average of asperity heights Rq =
root mean square value (standard deviation of asperity heights) R =
average radius of curvature of asperity summits .eta. = areal
density of asperities .beta. = roughness parameter
[0048] Formation of Roughened Surface using Photolithography
[0049] The roughened surface 380, 382, 384 can also be formed using
photolithography to define a pattern. A first photolithographic
process uses a mask to expose certain portions of a photoresist
layer. A second photolithographic process uses a split laser beam
to expose certain portions of a photoresist layer.
[0050] Formation of Roughened Surface using Image Pattern
[0051] FIGS. 10A-10D show cross-sectional views of successive
process steps for applying a roughening surface treatment using
photolithography and a dry or plasma etch to portions of the
contact surface 330 of the air-bearing surface 310 of the slider
126 in accordance with another embodiment of the invention. As
shown in FIG. 10A, a photoresist 1000 is deposited as a continuous
layer on contact surface 330. The photoresist is deposited as a
continuous layer over the entire contact surface 330, including the
transducer 150. The Photoresist can also be deposited as a
continuous layer on the entire air-bearing surface 310 of the
slider 126 which includes the contact surface 330. The photoresist
is selectively irradiated, as depicted by the arrows 1010 shown in
FIG. 10B, using a photo lithographic system, such as a step and
repeat optical projection system, in which I-line ultraviolet light
from a mercury-vapor lamp having a wavelength of 365 nm or DUV at
248 nm is projected through a first reticle and a focusing lens to
obtain an image pattern. The image pattern used may be a grid or
any other pattern. Thereafter, the photoresist is developed and the
irradiated portions of the photoresist are removed to provide
openings in photoresist, as is also shown in FIG. 10B. The
resulting openings in the photoresist expose portions of contact
surface 330 and define the pattern for the roughening of the
contact surface 330 of the air-bearing surface 310.
[0052] As shown by arrows 1020 in FIG. 10C, an etch is applied that
removes some of the exposed portions of contact surface 330 to form
the roughened surface 380. Various removal methods, as depicted by
arrows in 1020, can be used to selectively remove the contact
surface 330. Preferably, ion milling removes a portion of the
contact surface 330 of the air-bearing surface 300 on the center
island 310. A typical process for ion milling is to place the
substrate onto an ion mill rotating table, where the angle of
rotation can be varied so that the ion beam impinges on the surface
at a controlled angle, ranging from 0 degrees (incidence normal to
the ABS surface) to 90 degrees (incident ion beam traveling in the
plane of the substrate ABS surface). Typical incident beam energy
is 700 electron volts. A typical removal rate of unprotected ABS
surface material is 100 nm/minute. Typical milling times are 1 to 3
minutes. Milling time is typically split between milling angles of
45 and 60 degrees according to a recipe selected to obtain the
desired microtexture surface rounding. Various etchants, depicted
by arrows 1020, can be used to selectively remove the contact
surface 330. Preferably, a dry or plasma etch is applied that
removes a portion of the contact surface 330 of the air-bearing
surface 300 on the center island 310. The portion of the contact
surface 330 covered by the remaining photoresist 1000 is subjected
to the dry or plasma etch 1020 for a selected amount of time.
Different plasmas may be used to dry or plasma etch the exposed
portions of the contact surface 330. A different plasma may require
a different amount of exposure time for removing a selected
thickness of material at the contact surface 330. A different
concentration of ions used in the same type of plasma may also
require a different amount of exposure time to remove the exposed
contact surface 330. The exposure time, the makeup of the plasma
and the concentration of the ions used in the plasma may all be
altered to vary the rate at which the material forming the contact
surface 330 of the center island 310 of the slider 126 is removed.
One example of an etchant is standard ion milling, applied for 3
minutes, in an ion mill chamber.
[0053] As shown in FIG. 10D, after a selected amount of the
material is removed from the slider 126 at and near the contact
surface 330 with the dry or plasma etch, the remaining photoresist
1000 is stripped (not shown in FIG. 10D). This results in a
roughened contact surface 380 portion 330 on the air-bearing
surface 300. The pattern is typically a grid of columns which have
a square or diamond cross section. The dry or plasma etch is used
in this process since vertical edges 1012 can be made or defined
without the undercutting problems associated with wet etch
processes. Using this method, the pitch of the pattern generated is
limited since the pattern which can be projected by the
photolithographic system, such as a step and repeat optical
projection system, in which 248 nm ultraviolet light from a
mercury-vapor lamp projected through a first reticle and a focusing
lens is limited to an image pattern having a pitch of 0.4 .mu.m.
The image pattern used may be a grid or any other pattern. The
result is a set of columns 1011 having edges 1012. The roughened
contact surface 380 includes these columns. Using this method,
surface roughnesses in the range of approximately 1 to 12 nm are
achievable.
[0054] Formation of Roughened Surface using Split Laser
[0055] According to another embodiment of this invention, the grid
pattern on the photoresist is defined by a split laser, rather than
by the photolithographic system which uses a step-and-repeat
optical projector system in which an I-line ultra-violet light from
a mercury vapor lamp or DUV from an excimer laser source is
projected through a first reticle and a focusing lens. Use of a
laser provides for a much finer pitch pattern, which is formed in
the photoresist. The process associated with forming the roughened
surface 380, namely the exposure of the photoresist to light as
depicted by arrows 1010 in FIG. 10B, is conducted by the
split-laser apparatus 1100 shown in FIG. 11. The remaining portions
of the photo lithographic process depicted by FIGS. 10A to 10D are
the same. Rather than repeat the entire process or description of
FIGS. 10A to 10D, the below discussion will focus on the
differences between the process for using a split laser and the
process which uses the other photolithographic system to expose the
photoresist 1000.
[0056] FIG. 11 is a schematic of an apparatus 1100 used to expose
the photoresist 1000 and to apply a fine-pitched surface treatment
to the contact surface 330 of the center island 310 of the
air-bearing surface 300. The apparatus 1100 includes an
ultra-violet (UV) laser 1110, a beam splitter 1112, a first
split-beam director 1114 and a second split-beam director 1116. The
UV laser 1110 produces lazed light directed at the beam splitter
1112. At the beam splitter 1112, the lazed light is divided into a
first laser beam 1120 and a second laser beam 1122. The first beam
of lazed light 1120 is directed to the first split-beam director
1114 and the second beam of lazed light 1122 is directed to the
second split-beam director 1116. The first split-beam director 1114
directs the first beam 1120 to the contact surface 330 of the
island 310 of the substrate 126. Similarly, the second split-beam
director 116 directs the second bean of lazed light 1122 toward the
contact surface 330 of the center island 310 of the slider 126. The
contact surface 330 of the air-bearing surface 300 is coated with a
negative-acting or positive-acting photoresist sensitive to deep
ultraviolet irradiation. The resist thickness is approximately
twice the pitch of the fine pattern which will be formed. The first
beam of lazed light 1120 and the second beam of lazed light 1122
interfere at the surface 330 of the center island 310. Portions of
the lazed light interfere and cancel and other portions of the
lazed light constructively add together to form an array of light
at the contact surface 330. The pitch of the pattern along a line
in the plane of the intersecting laser beams 1120 and 1122, and the
substrate surface or contact surface 330 is 1 Pitch =
LaserWavelength 2 * sin ( )
[0057] where .theta. is the laser irradiation angle of incidence
with respect to the vector, normal to the substrate or contact
surface 330 of the center island 310 of the air-bearing surface 300
of the slider 126. The vector is shown as a dotted line carrying
the reference numeral 1140. Using the conventional UV-sensitive
resists, a pattern pitch of 200 nanometers (nm) is readily
achieved. Using DUV resists and an excimer laser, a pattern pitch
as small as 100 nm is achievable.
[0058] The contact surface 330 is exposed two times. The second
exposure is done after the slider and center island 310 have been
rotated through a number of degrees. Preferably, the substrate or
contact surface of the center island 310 is rotated through 90
degrees so that columns having a square shape are formed. The
substrate or center island 310 could be rotated through an angle
more or less than 90 degrees to form a series of columns having
diamond-like cross sections. The resist is developed and a
conventional etch process, such as ion milling or a dry or plasma
etch is used to remove some of the material at or near the contact
surface. The roughened surface 380 is formed after the resist is
then removed.
[0059] Advantageously, a roughened portion of the contact surface
reduces the stiction forces produced between the surface of the
disk and the slider and allows landing of a slider onto a smooth
disk. Advantageously, since a smooth disk can be used the spacing
between the transducing head associated with the slider and the
disk can be controlled and kept to a minimum to provide for an
enhanced recording density of the information stored on the disk.
The roughened contact area of the air-bearing surface not only
reduces stiction forces between the disk and the slider, but it
also provides a stable air-bearing surface for the slider. The
resulting air-bearing is rugged and durable. The materials used to
form the roughened surface are removed so the only materials
remaining are those already in the drive. Thus, outgassing problems
are minimal.
[0060] FIG. 12 is a schematic view of a computer system.
Advantageously, the invention is well-suited for use in a computer
system 1200. The computer system 1200 may also be called an
electronic system or an information handling system and includes a
central processing unit, a memory and a system bus. The information
handling system includes a central processing unit 1204, a random
access memory 1232, and a system bus 1230 for communicatively
coupling the central processing unit 1204 and the random access
memory 1232. The information handling system 1202 includes a disk
drive device which includes the ramp described above. The
information handling system 1202 may also include an input/output
bus 1210 and several devices peripheral devices, such as 1212,
1214, 1216, 1218, 1220, and 1222 may be attached to the input
output bus 1210. Peripheral devices may include hard disk drives,
magneto optical drives, floppy disk drives, monitors, keyboards and
other such peripherals. Any type of disk drive may use the slider
having the surface treatment discussed above.
[0061] It is to be understood that the above description is
intended to be illustrative, and not restrictive. Many other
embodiments will be apparent to those of skill in the art upon
reviewing the above description. The scope of the invention should,
therefore, be determined with reference to the appended claims,
along with the full scope of equivalents to which such claims are
entitled.
* * * * *