US20040077294A1

US20040077294A1 - Method and apparatus to provide a GMR lapping plate texturization using a photo-chemical process

Info

Publication number: US20040077294A1
Application number: US10/683,927
Authority: US
Inventors: Niraj Mahadev; Nelson Truong; Winston Jose; Katherine Chiang
Original assignee: SAE Magnetics HK Ltd
Current assignee: SAE Magnetics HK Ltd
Priority date: 2002-10-11
Filing date: 2003-10-10
Publication date: 2004-04-22
Also published as: CN100481210C; CN1726534A

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.

Description

FIELD OF THE INVENTION

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

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.

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.

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.

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.

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).

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.

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.

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 groove 4. 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.

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.

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

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

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. [0013]
FIG. 2 is a plan view of a mounted air bearing slider over a moving magnetic storage medium. [0014]
FIG. 3 is a flow diagram of a method of fabricating a lapping plate according to an embodiment of the present invention. [0015]
FIGS. 4[0016] a-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

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 [0017] 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° 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 μm. 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.
In [0018] 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).
In [0019] 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.
In [0020] 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.
Referring to FIGS. 4[0021] a-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.
Once the [0022] 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.
The [0023] 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).
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. [0024]
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. [0025]

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;

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:

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.