U.S. patent application number 10/683927 was filed with the patent office on 2004-04-22 for method and apparatus to provide a gmr lapping plate texturization using a photo-chemical process.
Invention is credited to Chiang, Katherine, Jose, Winston, Mahadev, Niraj, Truong, Nelson.
Application Number | 20040077294 10/683927 |
Document ID | / |
Family ID | 35925186 |
Filed Date | 2004-04-22 |
United States Patent
Application |
20040077294 |
Kind Code |
A1 |
Mahadev, Niraj ; et
al. |
April 22, 2004 |
Method and apparatus to provide a GMR lapping plate texturization
using a photo-chemical process
Abstract
A system and method are described for manufacturing a lapping
plate. In one example, the lapping plate is made by covering a
Tin-Antimony plate with photoresist and exposing the resulting
photoresist layer with UV light through a wire mesh mask. After
development, the non-etch areas can serve as land areas for diamond
charging. Such a method may lead to fewer artifacts on the lapping
plate and smaller diamond particle dimensions resulting in better
processing of read/write heads, especially GMR heads.
Inventors: |
Mahadev, Niraj; (Fremont,
CA) ; Truong, Nelson; (Milpitas, CA) ; Jose,
Winston; (San Jose, CA) ; Chiang, Katherine;
(Mountain View, CA) |
Correspondence
Address: |
KENYON & KENYON
Suite 700
1500 K. Street, N.W.
Washington
DC
20005
US
|
Family ID: |
35925186 |
Appl. No.: |
10/683927 |
Filed: |
October 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60417665 |
Oct 11, 2002 |
|
|
|
Current U.S.
Class: |
451/36 ; 451/527;
451/54; G9B/5.082 |
Current CPC
Class: |
B24D 18/00 20130101;
G11B 5/3116 20130101; B24B 37/00 20130101 |
Class at
Publication: |
451/036 ;
451/054; 451/527 |
International
Class: |
B24B 001/00; B24C
001/00; B24D 011/00 |
Claims
What is claimed is:
1. A method of manufacturing a lapping plate comprising:
selectively etching a metal plate; and imbedding diamond particles
into said metal plate.
2. The method of claim 1 wherein said etching step includes:
applying a photoresist layer to said metal plate; and selectively
removing photoresist from a surface of said metal plate.
3. A method of manufacturing a lapping plate comprising: applying a
photoresist layer to a metal plate; selectively exposing areas of
said photoresist layer to electromagnetic radiation; developing
said photoresist layer; etching areas of said metal disk; and
imbedding diamond particles into non-etched areas of said metal
disk.
4. The method of claim 3 wherein said selectively exposing
operating includes: providing a mask between an electromagnetic
radiation source and said photoresist layer;
5. The method of claim 4 wherein said mask is a wire mesh.
6. The method of claim 4 wherein said electromagnetic radiation is
ultra-violet radiation.
7. The method of claim 4 wherein said photoresist is a positive
photoresist.
8. The method of claim 4 wherein said photoresist is a negative
photoresist.
9. The method of claim 4 wherein said etching operation is a
wet-etch operation.
10. The method of claim 4 wherein said diamond particles have a
diameter less than 50 nanometers.
11. A method of fabricating a read/write head for a disk drive,
comprising: applying a photoresist layer to a metal plate;
selectively exposing areas of said photoresist layer to
electromagnetic radiation; developing said photoresist layer;
etching areas of said metal disk; imbedding diamond particles into
non-etched areas of said metal disk to create a lapping plate; and
lapping a read/write head with said lapping plate.
12. The method of claim 11 wherein said selectively exposing
operating includes: providing a mask between an electromagnetic
radiation source and said photoresist layer;
13. The method of claim 12 wherein said mask is a wire mesh.
14. The method of claim 12 wherein said electromagnetic radiation
is ultra-violet radiation.
15. The method of claim 12 wherein said photoresist is a positive
photoresist.
16. The method of claim 12 wherein said photoresist is a negative
photoresist.
17. The method of claim 12 wherein said etching operation is a
wet-etch operation.
18. The method of claim 12 wherein said diamond particles have a
diameter less than 50 nanometers.
19. The method of claim 18 wherein said read/write head is a GMR
read/write head.
20. The method of claim 18 wherein a pole tip recession for said
GMR read/write head is between 2 and 3 nanometers.
21. A lapping plate comprising: a metal plate including a plurality
of etched areas, said etched areas formed from an etching operation
through a developed photoresist mask; and diamond particles
imbedded into non-etched areas of the metal plate.
22. The lapping plate of claim 21 wherein said photoresist is a
positive photoresist.
23. The lapping plate of claim 21 wherein said photoresist is a
negative photoresist.
24. The lapping plate of claim 21 wherein said metal plate is
wet-etched.
25. The lapping plate of claim 21 wherein said diamond particles
have a diameter less than 50 nanometers.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains to a method and apparatus for
processing slider devices for hard disk drives and the like. More
particularly, the present invention pertains to lapping slider air
bearing surfaces, especially for GMR type heads.
BACKGROUND TO THE INVENTION
[0002] Hard disk drives are common information storage devices
essentially consisting of a series of rotatable disks that are
accessed by magnetic reading and writing elements. These data
transferring elements, commonly known as transducers, are typically
carried by and embedded in a slider body that is held in a close
relative position over discrete data tracks formed on a disk to
permit a read or write operation to be carried out. In order to
properly position the transducer with respect to the disk surface,
an air bearing surface (ABS) formed on the slider body experiences
a fluid air flow that provides sufficient lift force to "fly" the
slider and transducer above the disk data tracks. The high speed
rotation of a magnetic disk generates a stream of air flow or wind
along its surface in a direction substantially parallel to the
tangential velocity of the disk. The air flow cooperates with the
ABS of the slider body which enables the slider to fly above the
spinning disk. In effect, the suspended slider is physically
separated from the disk surface through this self-actuating air
bearing. The ABS of a slider is generally configured on the slider
surface facing the rotating disk, and greatly influences its
ability to fly over the disk under various conditions.
[0003] As shown in FIG. 1 an ABS design known for a common
catamaran slider 5 may be formed with a pair of parallel rails 2
and 4 that extend along the outer edges of the slider surface
facing the disk. Other ABS configurations including three or more
additional rails, with various surface areas and geometries, have
also been developed. The two rails 2 and 4 typically run along at
least a portion of the slider body length from the leading edge 6
to the trailing edge 8. The leading edge 6 is defined as the edge
of the slider that the rotating disk passes before running the
length of the slider 5 towards a trailing edge 8. As shown, the
leading edge 6 may be tapered despite the large undesirable
tolerance typically associated with this machining process. The
transducer or magnetic element 7 is typically mounted at some
location along the trailing edge 8 of the slider as shown in FIG.
1. The rails 2 and 4 form an air bearing surface on which the
slider flies, and provide the necessary lift upon contact with the
air flow created by the spinning disk. As the disk rotates, the
generated wind or air flow runs along underneath, and in between,
the catamaran slider rails 2 and 4. As the air flow passes beneath
the rails 2 and 4, the air pressure between the rails and the disk
increases thereby providing positive pressurization and lift.
Catamaran sliders generally create a sufficient amount of lift, or
positive load force, to cause the slider to fly at appropriate
heights above the rotating disk. In the absence of the rails 2 and
4, the large surface area of the slider body 5 would produce an
excessively large air bearing surface area. In general, as the air
bearing surface area increases, the amount of lift created is also
increased.
[0004] As-illustrated in FIG. 2, a head gimbal assembly 40 often
provides the slider with multiple degrees of freedom such as
vertical spacing, or pitch angle and roll angle which describe the
flying height of the slider. As shown in FIG. 2, a suspension 74
holds the HGA 40 over the moving disk 76 (having edge 70) and
moving in the direction indicated by arrow 80. In operation of the
disk drive shown in FIG. 2, an actuator 72 moves the HGA over
various diameters of the disk 76 (e.g., inner diameter (ID), middle
diameter (MD) and outer diameter (OD)) over arc 78.
[0005] Giant Magnetoresistive (GMR) heads are being used more and
more for advanced hard disk drive (e.g., capable of storing more
than 80 gigabytes of data). GMR heads, which are well-known in the
art, include components generally located in the middle of the
trailing portion of the slider (not the air bearing surface of the
slider). These components are quite susceptible to damage induced
by head manufacturing processes, particularly during lapping
processes. An example of a lapping operation and a plate used for
the operation are shown in U.S. Pat. No. 4,866,886 to Holmstrand.
The plate includes an embedded abrasive (e.g., diamond particles)
and is spun so as to abrade a surface of the GMR head held in place
over the moving plate. An abrasive slurry can be added to the plate
to facilitate the abrading process. As known in the art, the
lapping plates include "lands" and "grooves." The lands are at a
greater height than the grooves on the lapping plate and come into
contact with the slider surface. The grooves become a repository
for the abrasive particles (e.g., the particles in the slurry, the
particles originally embedded in the lapping plate, etc.). The
grooves also become a repository for the material removed from the
slider.
[0006] Using lapping plates as described above can cause problems
in the manufacture of GMR heads. The relatively large abrasive
particles can damage the GMR head portion of the slider. One
approach to improving head manufacture is to use smaller particles
in the lapping plate. As the abrasive particles become smaller,
however, it becomes harder to control lapping plate flatness,
texture, roughness and cleanliness to successfully embed diamond
abrasive, for example (sometimes referred to as the charging
process).
[0007] The texturing process for the lapping plate could have a
profound impact on GMR head performance of the slider. The texture
of the lapping plate will have an effect on slider properties such
as surface finish, pole tip recession (or PTR), smearing (i.e.,
potentially causing device shorting), and bulk removal rates.
[0008] The Holmstrand reference refers to one such texturing
process. In Holmstrand, small cavities in the surface of the
lapping plate are created using a glass bead blasting apparatus.
Using the texturing process of Holmstrand, the PTR can be
controlled to an order of 28 microns. With current sliders,
however, the PTR is controlled to less than 0.01 microns. One
possible reason for such a high value may be that the cavities
serve as reservoirs for abrasive sludge instead of allowing the
sludge to leave the surface of the disk (e.g., through centrifugal
force of, the spinning lapping plate). Accordingly, this texturing
process is not acceptable for current slider manufacturing.
[0009] Another process is where spiral grooves are provided in the
surface of the lapping plate. The spiral grooves are formed using a
facing machine. The width and spacing of the lands and grooves is
referred to as the "pitch" of the lapping plate. After the spiral
grooves are formed, the lapping plate is further processed by
"deburring" (or shaving), which knocks off high peaks and leaves
the lands for diamond charging. One problem with the deburring
process is that it typically induces machine related burrs, uneven
land to groove ratios, broken edges of the plateau and varying
depths of the groove4. These, in turn, could directly or indirectly
affect the properties of the finished slider. One solution is to
finely control the operation and function of the facing machine,
though doing so can be an expensive and time-consuming process.
[0010] Yet another process for fabricating a lapping plate includes
the use of a diamond-textured ring process. As described in U.S.
Pat. No. 4,037,367 to Kruse, the natural flow of grooves
facilitates a relative easy removal of sludge unlike that shown in
the Holmstrand patent. Though the process in Kruse may improve bulk
removal rates and pole tip recession, the roughness of the land
area is uneven and excessive plate material debris may be caught in
the grooves and be difficult to remove. In such a case it may
become harder to charge the land areas with smaller size diamond
particles (i.e., ones have a mean diameter of, 1.0 microns).
Another disadvantage of this process is that the amount of plate
debris increases with increased softness of the plate material,
thus limiting this process to hard plate materials.
[0011] In view of the above, there is a need for an improved
lapping plate and method of manufacturing such plates the reduces
plate debris.
SUMMARY OF THE INVENTION
[0012] According to an embodiment of the present invention, a
method and apparatus for manufacturing a lapping plate are
provided. In one embodiment, the metal plate is first chemically
etched using mask-etch procedure that are known in the silicon chip
manufacturing field. The areas of the metal plate that are not
etched during this procedure form lands in which diamond charging
can be accomplished. The resulting lapping plate may be used with
sensitive GMR heads because of the relatively small diamond
particles that can be charged into the metal plate and their
relatively even distribution across the plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a perspective view of a flying slider with a read
and write element assembly having a tapered conventional catamaran
air bearing slider configuration.
[0014] FIG. 2 is a plan view of a mounted air bearing slider over a
moving magnetic storage medium.
[0015] FIG. 3 is a flow diagram of a method of fabricating a
lapping plate according to an embodiment of the present
invention.
[0016] FIGS. 4a-l are views of a lapping plate and an apparatus for
implementing the method of FIG. 3 for fabricating lapping plate
according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0017] Referring to FIG. 3, a flow diagram is shown of a method
according to an embodiment of the present invention. In this
embodiment, the lapping plate is made of an alloy of Tin and
Antimony. In block 301, the lapping plate is machined to make it
flat.(e.g., less than 2 microns of roughness). In block 303, the
lapping plate may then be polished or textured (depending on the
quality of the machining process). For example a burr-free
polishing cloth may be used with a very-fine abrasive to remove any
artifacts remaining from the machining operation of block 301. In
block 305, the lapping plate is then heated in an oven (for
example, at 60.degree. C. for approximately 15 minutes). The heated
plate is then laminated with a photoresist (e.g., the FL13
photoresist manufactured by Shipley Company, LLC, Marlborough,
Mass.) at a thickness of 30 .mu.m. The remnant heat in the lapping
plate assists in facilitating an even flow of the photoresist over
the surface of the plate. In addition, the laminator device that is
used to put the photoresist onto the lapping plate can heat the
photoresist while pressing it onto the plate to prevent air bubbles
between the plate and photoresist.
[0018] In block 309, the photoresist layer is selectively exposed
(e.g., to electromagnetic radiation such as ultra violet light) for
a predetermined amount of time (e.g., 8-10 seconds). In this
embodiment, a stainless steel mesh fabric, such as a MicroMesh
product by Micro Metallic, Ltd. (Mersyside, UK), is used have a
selected hole dimension and spacing. Other types of masks may be
used including those used in standard photolithographic processes.
Using a the stainless steel mesh fabric may make the expose
operation quicker and/or more inexpensive compared to standard
photolithographic masking. In block 311, the lapping plate and
exposed photoresist are developed. In one embodiment, the
photoresist is developed by rotating the plate at a predetermined
speed and spraying developer solution onto the photoresist layer
via nozzles for a predetermined amount of time (e.g., enough time
to allow sufficient dissolving of selected areas of the photoresist
layer). In block 313, the lapping plate is washed with deionized
(DI) water to remove the developer solution and the dissolved
photoresist. The lapping plate is then dried (e.g., clean air
supplied via a nozzle over the surface of the plate).
[0019] In block 315, the lapping plate is etched. In this
embodiment of a Tin-Antimony alloy plate, a 1:3 ratio of
hydrochloric acid to nitric acid may be used as the etchant. Such
acids may be diluted with deionized water depending on the depth of
etching into the plate that is desired. Thus, in block 315, the
plate is wet-etched for a predetermined amount of time (e.g., five
minutes). In this embodiment, the lapping plate is submerged in an
etchant bath and the etchant is continuously agitated so that the
etching depth is kept uniform over the area of the plate. After the
etching operations, the plate can then be rinsed in deionized water
and air dried in a manner similar to that above. In block 317, the
remaining photoresist is removed from the lapping plate (e.g.,
using an acetone solution to dissolve the undeveloped photoresist).
In block 319, the lapping plate is cleaned by rinsing it in
deionized water and air drying it in a manner similar to that
above. Alternatively, the rinsed lapping plate may be dried with an
appropriate cloth.
[0020] In block 321, the lapping plate is charged with diamond
particles. As stated above, it is advantageous for the lapping of
GMR heads if the diamond particles are relatively small in
diameter. Though diamonds having a mean diameter of 100 nm to 125
nm may be used, in this example, the charging apparatus deposits
diamonds having a mean diameter of less than 50 nanometers. The
diamonds are deposited into the land areas of the lapping plate
(i.e., the areas of the lapping plate that have not been etched in
the processes above). The resulting plate may have a very uniform
placement of small diameter diamond particles. Using a lapping
plate constructed according to an embodiment of the present
invention, a pole tip recession for the read/write head may be very
low (e.g., between 2 and 3 nanometers) resulting in improved
performance for the head in the disk drive environment.
[0021] Referring to FIGS. 4a-1 a lapping plate and apparatus for
fabricating one are shown according to an embodiment of the present
invention. In FIG. 4a, a metal disk 410 made of an alloy of Tin and
Antimony is provided. In this example, the disk has a thickness of
2.5 inches and a diameter of 16 inches. In FIG. 4b, the disk 410 is
placed on a spindle motor 412 and made flat by machining apparatus
414. In FIG. 4c, the disk 410 is polished with a burr-free
polishing cloth (e.g., with machine 416). The disk can then be
laminated with. photoresist. In FIG. 4d, the metal disk 410 is spun
by spindle motor 412 after photoresist is deposited by deposition
apparatus 418.
[0022] Once the photoresist layer 426 is set to the metal disk, a
mask, such as a wire mesh 424, can be placed over the photoresist
layer (See FIG. 4e). In this example, a UV radiation source 422
exposes portions of the photoresist layer 426 through the wire mesh
424. The metal disk 410 may be placed on a support 420 during this
exposure operation. In FIG. 4f, developer is disposed onto the
metal disk via apparatus 428. As known in the art, developer reacts
with the exposed or unexposed areas of the photoresist depending on
the type of photoresist being used. In FIG. 4g, the undesired
photoresist is removed, for example, by spraying the metal disk
with deionized water.
[0023] The metal disk 410 with developed photoresist layer 426 is
etched. As seen in FIG. 4h, the metal disk 410 can be lowered into
etchant 436 in tub 438 while resting on holder 434. An agitator may
be provided to vibrate the tub 438 so as to improve the etching
process. In FIG. 4i, the photoresist layer 426 is removed with
apparatus 440. In FIG. 4j, the metal disk 410 is cleaned with an
appropriate cloth 442. In FIG. 4k, the metal disk 410 is diamond
charged with apparatus 444 to dispose diamond particles of a
selected size into the unetched land areas of the metal disk to
finish the lapping plate. Once completed, the lapping plate may be
used to lap sliders including GMR sliders held by apparatus 446
(e.g., see FIG. 4l).
[0024] While the present invention has been described with
reference to the aforementioned applications, this description of
the preferred embodiments is not meant to be construed in a
limiting sense. It shall be understood that all aspects of the
present invention are not limited to the specific depictions,
configurations or dimensions set forth herein which depend upon a
variety of principles and variables. Various modifications in form
and detail of the disclosed apparatus, as well as other variations
of the present invention, will be apparent to a person skilled in
the art upon reference to the present disclosure. It is therefore
contemplated that the appended claims shall cover any such
modifications or variations of the described embodiments as falling
within the true spirit and scope of the present invention.
[0025] For example, though in FIGS. 3 and 4, a wire mesh is used as
a mask, the location and dimensions of the land areas for diamond
charging may be more accurately controlled by using a more
conventional mask as known in the art.
* * * * *