U.S. patent application number 11/354186 was filed with the patent office on 2006-06-22 for oblique burnish/wipe mechanism for hard drive disk like media.
This patent application is currently assigned to SEAGATE TECHNOLOGY LLC. Invention is credited to Jing Gui, David S. Kuo, Wei-Ming Lee.
Application Number | 20060130874 11/354186 |
Document ID | / |
Family ID | 34274103 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060130874 |
Kind Code |
A1 |
Lee; Wei-Ming ; et
al. |
June 22, 2006 |
Oblique burnish/wipe mechanism for hard drive disk like media
Abstract
An oblique burnish mechanism that provides both translation and
rotation degrees of freedom to effectively remove the particles on
an article is disclosed. The oblique angle of the mechanism can be
adjusted so that the kinematical condition can be selected relative
to the motion of the area of the article, preferably a rotating
disk, being burnished.
Inventors: |
Lee; Wei-Ming; (Pleasanton,
CA) ; Kuo; David S.; (Palo Alto, CA) ; Gui;
Jing; (San Jose, CA) |
Correspondence
Address: |
SEAGATE TECHNOLOGY c/o MOFO NOVA
1650 TYSONS BOULEVARD
SUITE 300
MCLEAN
VA
22102
US
|
Assignee: |
SEAGATE TECHNOLOGY LLC
Scotts Valley
CA
|
Family ID: |
34274103 |
Appl. No.: |
11/354186 |
Filed: |
February 15, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10662426 |
Sep 16, 2003 |
|
|
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11354186 |
Feb 15, 2006 |
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Current U.S.
Class: |
134/6 ; 15/77;
G9B/5.299 |
Current CPC
Class: |
B08B 1/00 20130101; F16C
17/045 20130101; F16C 17/10 20130101; F16C 17/04 20130101; G11B
5/8404 20130101; F16C 33/74 20130101; F16C 33/107 20130101 |
Class at
Publication: |
134/006 ;
015/077 |
International
Class: |
B08B 7/00 20060101
B08B007/00 |
Claims
1-20. (canceled)
21. A method of operating a disk cleaning apparatus, the method
comprising: positioning a burnishing object of the apparatus over
or under a disk to extend adjacent a surface of the disk at an
angle that is offset from a line passing through the center of the
disk; rotating the burnishing object to change the offset angle of
the burnishing object; and translating the burnishing object
relative to the disk to advance a position of a contact of the
burnishing object across the surface of the disk, wherein changing
the offset angle of the burnishing object and translating the
burnishing object occur while cleaning the disk.
22. The method of claim 21, wherein the burnishing object is not
contacted to the disk by air directed to the burnishing object.
23. The method of claim 21, wherein the offset angle changes as the
position of the contact advances from an inner diameter to an outer
diameter of the disk.
24. The method of claim 21, wherein the cleaning apparatus removes
particles from the surface of the disk.
25. The method of claim 21, wherein the rotating and translating of
the burnishing object is done simultaneously.
26. The method of claim 21, wherein the burnishing object makes and
breaks contact with the disk across the surface of the disk.
27. The method of claim 21, wherein the burnishing object is a
tape.
28. The method of claim 21, wherein the burnishing object is a
pad.
29. A method of operating a disk cleaning apparatus comprising a
burnishing object positioned over or under a disk and extending
adjacent a surface of the disk at an angle that is offset from a
line passing through the center of the disk, the method comprising:
rotating the burnishing object to change the offset angle of the
burnishing object; and translating the burnishing object relative
to the disk to advance a position of a contact of the burnishing
object across the surface of the disk, wherein rotating and
translating the burnishing object occur while cleaning the
disk.
30. The method of claim 29, wherein the burnishing object is not
contacted to the disk by air directed to the burnishing object.
31. The method of claim 29, wherein the offset angle changes as the
position of the contact advances from an inner diameter to an outer
diameter of the disk.
32. The method of claim 29, wherein the cleaning apparatus removes
particles from the surface of the disk.
33. The method of claim 29, wherein the rotating and translating of
the burnishing object is done simultaneously.
34. The method of claim 29, wherein the burnishing object makes and
breaks contact with the disk across the surface of the disk.
35. The method of claim 29, wherein the burnishing object is a
tape.
36. The method of claim 29, wherein the burnishing object is a
pad.
37. A method of operating a disk cleaning apparatus, the method
comprising: positioning a burnishing object of the apparatus over
or under a disk; and simultaneously translating and rotating the
burnishing object on the disk while cleaning the disk.
38. The method of claim 37, wherein the offset angle changes as the
position of the contact advances from an inner diameter to an outer
diameter of the disk.
39. The method of claim 37, wherein the cleaning apparatus removes
particles from the surface of the disk.
40. The method of claim 37, wherein the burnishing object makes and
breaks contact with the disk across the surface of the disk.
Description
FIELD OF INVENTION
[0001] The present invention relates to the recording, storage and
reading of magnetic data, particularly burnishing or wiping
rotatable magnetic recording media, such as thin film magnetic
disks having smooth surfaces for data zone and apparatus for
burnishing or wiping a media surface.
BACKGROUND
[0002] Magnetic disks and disk drives are conventionally employed
for storing data in magnetizable form. Preferably, one or more
disks are rotated on a central axis in combination with data
transducing heads positioned in close proximity to the recording
surfaces of the disks and moved generally radially with respect
thereto. Magnetic disks are usually housed in a magnetic disk unit
in a stationary state with a magnetic head having a specific load
elastically in contact with and pressed against the surface of the
disk. Data are written onto and read from a rapidly rotating
recording disk by means of a magnetic head transducer assembly that
flies closely over the surface of the disk. Preferably, each face
of each disk will have its own independent head.
[0003] A disk recording medium is shown in FIG. 1. Even though FIG.
1 shows sequential layers on one side of the non-magnetic substrate
10, it is to sputter deposit sequential layers on both sides of the
non-magnetic substrate.
[0004] Adverting to FIG. 1, a sub-seed layer 11 is deposited on
substrate 10, e.g., a glass or glass-ceramic, Al or AlMg substrate.
Subsequently, a seed layer 12 is deposited on the sub-seed layer
11. Then, an underlayer 13, is sputter deposited on the seed layer
12. An intermediate or flash layer 14 is then sputter deposited on
underlayer 13. Magnetic layer 15 is then sputter deposited on the
intermediate layer, e.g., CoCrPtTa. A protective covering overcoat
16 is then sputter deposited on the magnetic layer 15. A lubricant
topcoat (not shown in FIG. 1 for illustrative convenience) is
deposited on the protective covering overcoat 16.
[0005] The disk is finely balanced and finished to microscopic
tolerances. Take the smoothness of its surface, for example. The
drive head rides a cushion of air at microscopic distances above
the surface of the disk. So, the surface cannot be too smooth, or
the drive lead will end up sticking to the disk, and it cannot be
too rough either, or the head will end up getting caught in the
microscopic bumps on the surface.
[0006] It is considered desirable during reading and recording
operations to maintain each transducer head as close to its
associated recording surface as possible, i.e., to minimize the
flying height of the head. This objective becomes particularly
significant as the areal recording density increases. The areal
density (Mbits/in.sup.2) is the recording density per unit area and
is equal to the track density (TPI) in terms of tracks per inch
times the linear density (BPI) in terms of bits per inch.
[0007] In recent years, considerable effort has been expended to
achieve high areal recording density. In particular, the
requirement to further reduce the flying height of the head imposed
by increasingly higher recording density and capacity renders the
disk drive particularly vulnerable to head crash due to accidental
glide hits of the head and media. To avoid glide hits, a smooth
defect-free surface of data zone is desired. The direct result of
these demands is tending towards low yield due to less defect
tolerance at the surface of the media. Thus, it is desired to
arrive at an improved mechanism for burnishing/polishing the
surface of the discs to produce defect-free surface.
SUMMARY OF THE INVENTION
[0008] This invention relates to a cleaning apparatus comprising an
article, a burnishing object positioned over or under the article,
and a device that (a) rotates the burnishing object at an offset
angle that is variable over an area of the article and (b)
translates the burnishing object relative to the article to advance
a position of a contact of the burnishing object with the article
across a surface of the article. Preferably, the burnishing object
is not contacted to the article by air directed to the burnishing
object and the article is a rotating disk. Also, preferably the
offset angle changes as the position of the contact advances from
an inner diameter to an outer diameter of the disk. Preferably, the
cleaning apparatus removes particles from the surface of the
article. Preferably, the device simultaneously rotates and
translates the burnishing object and the device creates a wiper
blade motion of the burnishing object on the surface of the
article. Preferably, the device allows the burnishing object to
make and break the contact of the burnishing object with the
article across the surface of the article. In one embodiment, the
burnishing object is a tape or a pad.
[0009] Another embodiment is a method of operating a cleaning
apparatus comprising an article and a burnishing object positioned
over or under the article, the method comprising (a) rotating the
burnishing object at an offset angle that is variable over an area
of the article and (b) translating the burnishing object relative
to the article to advance a position of a contact of the burnishing
object with the article across a surface of the article.
[0010] Another embodiment is a cleaning apparatus comprising an
article, a burnishing object positioned over or under the article,
and means for simultaneously translating and rotating the
burnishing object on the article.
[0011] Additional advantages of this invention will become readily
apparent to those skilled in this art from the following detailed
description, wherein only the preferred embodiments of this
invention is shown and described, simply by way of illustration of
the best mode contemplated for carrying out this invention. As will
be realized, this invention is capable of other and different
embodiments, and its details are capable of modifications in
various obvious respects, all without departing from this
invention. Accordingly, the drawings and description are to be
regarded as illustrative in nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 schematically shows a film structure of a magnetic
recording medium.
[0013] FIG. 2 schematically illustrates an exemplary burnishing
mechanism.
[0014] FIG. 3 shows an exemplary device of the burnishing
apparatus, the device having both translational and rotational
movements.
DETAILED DESCRIPTION
[0015] Almost all the manufacturing of the disks takes place in
clean rooms, where the amount of dust in the atmosphere is kept
very low, and is strictly controlled and monitored. The disk
substrates come to the disk fabrication site packed in shipping
cassettes. For certain types of media, the disk substrate has a
polished nickel-coated surface. The substrates are preferably
transferred to process cassettes to be moved from one process to
another. Preferably, the cassettes are moved from one room to
another on automatic guided vehicles to prevent contamination due
to human contact.
[0016] The first step in preparing a disk for recording data is
mechanical texturing by applying roughness and grooves to the
polished surface of the substrate. This helps in depositing a
magnetic material on the substrate. During the texturing process,
small amounts of nickel get removed from surface of the disk and
remain there. To remove this, the substrate is usually washed.
Also, techniques for polishing the surface of the non-magnetic
substrate of a recording medium use slurry polishing, which
requires wash treatment. Thus, disk substrates are washed after
texturing and polishing. However, wash defects could be one of the
top yield detractors.
[0017] The next step is the formation of the landing area
(preferably, a 2-4 mm band near the center) where the read head
comes to rest. Preferably, the landing area is formed by laser
texturing, which is done by creating microscopic bumps, using a
laser. This prevents the head from clinging to me disk surface when
the disk is spinning.
[0018] A final cleaning of the substrate is then done using a
series of ultrasonic, megasonic and quick dump rinse (QDR) steps.
At the end of the final clean, the substrate has an ultra-clean
surface and is ready for the deposition of layers of magnetic media
on the substrate. Preferably, the deposition is done by
sputtering.
[0019] Sputtering is perhaps the most important step in the whole
process of creating recording media. There are two types of
sputtering: pass-by sputtering and static sputtering. In pass-by
sputtering, disks are passed inside a vacuum chamber, where they
are bombarded with the magnetic and non-magnetic materials that are
deposited as one or more layers on the substrate. Static sputtering
uses smaller machines, and each disk is picked up and sputtered
individually.
[0020] The sputtering layers are deposited in what are called
bombs, which are loaded onto the sputtering machine. The bombs are
vacuum chambers with targets on either side. The substrate is
lifted into the bomb and is bombarded with the sputtered
material.
[0021] Sputtering leads to some spike formation on the substrate.
These spikes need to be removed to ensure that they do not lead to
the scratching between the head and substrate. Thus, a lube is
preferably applied to the substrate surface as one of the top
layers on the substrate.
[0022] Once a lube is applied, the substrates move to the tape
burnishing and tape wiping stage, where the substrate is polished
while it preferentially spins around a spindle. After
buffing/burnishing, the substrate is wiped and a clean lube is
evenly applied on the surface.
[0023] Subsequently, the disk is prepared and tested for quality
thorough a three-stage process. First, a burnishing head passes
over the surface, removing any bumps (asperities as the technical
term goes). The glide head then goes over the disk, checking for
remaining bumps, if any. Finally the certifying head checks the
surface for manufacturing defects and also measures the magnetic
recording ability of the substrate.
[0024] A technique for buffing/burnishing is tape burnishing
(buffing). However, the technique is attendant with numerous
disadvantages. For example, it is extremely difficult to provide a
clean and smooth surface due to debris formed by mechanical
abrasions.
[0025] Tape burnish and tape wipe processes in which the tape moves
orthogonal to the burnishing object without any rotational degree
of freedom of the burnishing tape cannot generally effectively
remove the particles on the surface of the disk. These particles
cause failure and/or decreased performance of the magnetic disc
drives. This problem can be especially critical in magnetic discs
made by the servo pattern printing process. This is because the
particles on the surface can damage the stamper, which sequentially
affects the quality of the printed discs. This invention allows the
tape burnishing and tape wiping processes to be improved to meet
the demands of high storage density and low fly height
criteria.
[0026] The cleaning apparatus for burnishing asperities or defects
from the surfaces of an article, e.g., a rigid magnetic disk, could
use an abrasive burnishing tape, a pad, a cloth, a scrubber or any
burnishing object that contacts and cleans the surface of the
object. If the object is a disk, then the disk preferably rotates
on a spindle while the burnishing object contacts the surface of
the disk. The burnishing object could be held stationary at one
location on the surface of the disk or moved during the burnishing
process.
[0027] In one embodiment, the burnishing object is contacted to the
article by air directed to the burnishing object. On the other
hand, in another embodiment, the burnishing object is not contacted
to the article by air directed to the burnishing object.
[0028] The trajectory of the burnishing object relative to the
burnished disc can be controlled to optimize the particle removal
effectiveness. A preferred embodiment is an oblique tape burnish
mechanism that would allow extra rotation degree of freedom besides
the translational degree of freedom to effectively remove the
particles from the surface of a rotating disk. The oblique angle of
the mechanism can be adjusted so that the kinematical condition can
be optimized relative to the motion of the area of the disk being
burnished. The oblique angle provide a condition to load and unload
the burnishing object on the disc which could maximize the burnish
area at the inner and outer diameters of the discs which are other
difficult to burnish with a burnishing device with just
translational degree of freedom. The combined translation and
rotation motion of the burnish pad simulates particle "wiping down"
motion.
[0029] FIG. 2 shows one embodiment of the burnishing apparatus on
the surface of a disk with outer and inner diameters of 22 and 30,
respectively. The burnishing apparatus includes a burnishing object
19, shown as a shaded object, which could be a burnishing tape,
extending along the arm 20 of the burnishing apparatus. The angle
between the arm 20 and a line passing through the center of disk is
called the offset angle and is designated as ".alpha." for the
particular angle shown in FIG. 2.
[0030] In one embodiment, the process sequence for burnishing are
the following: (1). Position the center of the burnishing object at
location 1 on the disk and set the offset angle at .alpha.. (2)
Translate the center of burnishing object linearly to location 2 on
the disk while maintaining the offset angle at .alpha.. (3) Rotate
the arm and change the offset angle to .beta. while maintaining the
center of the burnishing object at location 2.
[0031] In one embodiment, the process sequence for burnishing are
the following: (1). Position the center of the burnishing object at
location 1 on the disk and set the offset angle at .alpha.. (2)
Translate the center of burnishing object linearly to location 2 on
the disk while rotating the arm and changing the offset angle to
.beta..
[0032] In yet another embodiment, the process sequence for
burnishing are the following: (1) Position the center of the
burnishing object at location 1 on the disk and set the offset
angle at .alpha.. (2) Translate the center of burnishing object
linearly to location 2 on the disk while rotating the arm and
changing the offset angle to .beta.. (3) Translate the center of
burnishing object linearly to location 3 near the outer diameter 22
of the disk while rotating the arm and changing the offset angle to
.gamma..
[0033] Other embodiments could by any combinations of the above
embodiments. In addition, other kinematical conditions that allow
both translational and rotational movements of the burnishing
object are possible.
[0034] FIG. 3 shows another embodiment of a device burnishing
apparatus that allows both translational and rotational movements
of the burnishing object. This device has two arms. The first arm
has translational movement. The second arm is pivotally attached to
the first arm and has rotational movement. The burnishing object is
attached to the second arm. The combined movements of the first and
second arms allow the burnishing object to have both translational
and rotational movements, sequentially or simultaneously, over the
surface of a burnished article.
[0035] The asperities on the surface of the burnished article are
less than 5 nm, preferably less than 4 nm, most preferably less
than 3 nm. The surface parameters can be measured by atomic force
microscope (AFM) such as NanoScope..RTM. The statistics used by the
AFM are mostly derived from ASME B46.1 ("Surface Texture: Surface
Roughness, Waviness and Law") available from the American Society
of Mechanical Engineers, which is incorporated herein by
reference.
[0036] The parameters for measuring surface roughness due to
asperities are the following:
[0037] (1) Average surface roughness (R.sub.a): Arithmetic average
of the absolute values of the surface height deviations measured
from a mean plane. The value of the mean plane is measured as the
average of all the Z values within an enclosed area. The mean can
have a negative value because the Z values are measured relative to
the Z value when the microscope is engaged. This value is not
corrected for tilt in the plane of the data; therefore, plane
fitting or flattening the data will change this value.
R.sub.a=[|Z.sub.1|+|Z.sub.2|+ . . . +|Z.sub.n|]/N
[0038] (2) RMS: This is the standard deviation of the Z values
within the enclosed area and is calculated as
RMS=[{.SIGMA.(Z.sub.i-Z.sub.avg).sup.2}/N].sup.1/2
[0039] where Z.sub.avg is the average of the Z values within the
enclosed area, Z.sub.i is the current Z value, and N is the number
of points within the enclosed area. The RMS value is not corrected
for tilt in the plane of the data; therefore, plane fitting or
flattening the data will change this value.
[0040] (3) Maximum height (R.sub.max): This the difference in
height between the highest and lowest points on the surface
relative to the mean plane.
[0041] (4) R.sub.z: This is the average difference in height
between five highest peaks and five lowest valleys relative to the
mean plane.
[0042] All of surface parameters would be improved remarkably after
the burnish process of this invention. For example, the surface
roughness average R.sub.a can be reduced from about 3 nm to about
0.3 nm. The surface parameter RMS can be decreased from about 4 nm
to about 0.4 nm. The surface parameter R.sub.max can be reduced
from about 15 nm to about 2 nm. The surface parameter R.sub.z can
be reduced from about 9 nm to about 2 nm.
[0043] In other embodiments, the moving tape is applied to the
surface with a pad or a roller forcing the tape to contact the
surface or there is an additional wiping process. For a tape
burnishing process, the tape could have 0.3 micron alumina on a
tape of a polyester material. The contact force on the disk could
be adjusted to gram accuracy. The spindle rotation speed of disk
could be about 600 rpm. The tape moving speed could be about 8 inch
per minute. The contact time could be about three seconds or more.
After burnishing, a wiping process could be carried out with a
woven fabric polyester or cotton material. The wiping time could be
about three second with a disk rotation speed of about 400 rpm and
tape speed of about 4 inch per minute. The wiping process would
prepare a clean surface for AFM measurement.
[0044] In other embodiments, the burnishing process is combined
with a wash process, which could precede or follow the burnishing
process, and these processes could be used before or after the thin
film sputter deposition on the surface of a non-magnetic substrate.
The method of this invention can be used on a non-magnetic
substrate comprising glass, NiP/aluminum, metal alloys,
plastic/polymer material, ceramic, glass-ceramic, glass-polymer and
other composite materials.
[0045] The wash process, if implemented, could use acidic cleaners
that have pH range 1 to 5, preferably, 1.5 to 4 used to treat a
fresh surface of the rigid disk just following the mechanical
texture. The acidic cleaner could be sprayed on the disk surface
for a short time then followed by DI water spraying. Optionally,
after the acidic cleaner treatment the disk could soaked in the
alkaline soap solution.
[0046] In other embodiments of this invention the variations in
buffing, i.e., polishing, the surface that can be employed are any
one or more of the methods shown below.
Mechanical Polishing
[0047] Persons skilled in this art would recognize that the
variables that control mechanical polishing are: (a) substrate
surface initial condition: roughness, waviness, substrate size,
substrate shape and grain size; (b) polishing slurry size
(Al.sub.2O.sub.3, CeO.sub.2, SiO.sub.2, etc) and coolant (inorganic
and organic solutions with lubricant); (c) polishing time and
surface finishing; and (d) washing and cleaning substrate
surface
Chemical Polishing
[0048] Persons skilled in this art would recognize that the
variables that control hemical polishing are: (a) substrate surface
initial condition: roughness, waviness, substrate size, substrate
shape and grain size; (b) polishing solutions compositions and
their ability to dissolve the substrate materials; (c) the
composition consists of a combination of different acids (e.g.
nitric, sulfuric, hydrochloric, phosphoric, chromic, acetic) or
organic solutions (e.g. methanol, glycerin, ethyldiglicol), also
containing some added electropositive ions. E.g., polishing of Al:
small amounts of Cu will create additional local cathodes by
deposition on Al, stimulating the polishing process. Adding some
oxidants has a function as depolarization agents.
Electrochemical Polishing
[0049] Persons skilled in this art would recognize that the
variables that control electrochemical polishing are: (a) the
external source of electricity to produce the anodic current
density and voltage; (b) the electrolyte temperature; (c) the time
duration of electropolishing; (d) the cathodic materials; in
general, the cathode surface should be many times larger than that
of electropolished substrate and different materials are used as
cathodes depending on the applied electrolyte; and (e) agitation,
which can eliminates the undesired concentration of the dissolved
material at the substrate. Agitation can improve the supply of
fresh electropolishing electrolyte to substrate surface. Agitation
can prevent local heating and release gas bubbles from the polished
surface to avoid pitting on the substrate surface.
[0050] CMP (Chemical Mechanical Polishing) used in semiconductor
wafer polishing. Persons skilled in this art would recognize that
the variables that control the CMP process.
[0051] The above description is presented to enable a person
skilled in the art to make and use the invention, and is provided
in the context of a particular application and its requirements.
Various modifications to the preferred embodiments will be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other embodiments and applications
without departing from the spirit and scope of the invention. Thus,
this invention is not intended to be limited to the embodiments
shown, but is to be accorded the widest scope consistent with the
principles and features disclosed herein. Finally, the entire
disclosure of the patents and publications referred in this
application are hereby incorporated herein by reference.
* * * * *