Abstract:
An improved slider design with stiction reduction pads is presented along with a method of making the same. In one embodiment, the bases for the stiction reduction pads are made first during an etching process for the air bearing surfaces, then the stiction reduction pads are made higher so as to prevent unwanted contacted between the air bearing surface and the disc as well as reducing meniscal forces that can be caused by a lubricant on the disc.

Description:
RELATED APPLICATIONS 
   This application claims priority to the extent available (including under 35 U.S.C. §119(e)(1)) to provisional application No. 60/132,978 filed May 7, 1999. 

   FIELD OF THE INVENTION 
   The present invention is directed to slider designs in disk drives. More particularly, the present invention pertains to a slider design including stiction reduction pads. 
   BACKGROUND OF 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. 
   Once the disk stops rotating, the slider comes to rest on the surface of the disk When the rotation of the disk begins again, the air-bearing is formed once again and the slider separates from the disk. This process is typically called contact-start-stop (CSS). In order to reduce friction between the slider and the disk, a very thin layer of lubricant on the order of a few nanometers, is applied onto the surface of the disk. One of the problems with CSS operations, is the effect of starting friction (“stiction”). Stiction is caused by a meniscus of lubricant formed between the slider and the disk that clamps the slider down to the media. In some cases, especially in a humid environment, the slider is held down strong enough that the disk fails to rotate. To correct this problem, pads are introduced onto the surface of the slider to reduce the area of contact between the slider and the disk. The pads are extremely tall to minimize the meniscal problem described above. 
   SUMMARY OF THE INVENTION 
   The present invention provides an air bearing slider with an improved pad structure and a method of manufacturing such a structure. According to an embodiment of the present invention, the air-bearing surface and a base portion of the stiction reduction pad are formed during a first etching step. Then the structure can be made higher by adding additional material (e.g., a second DLC layer and a second adhesion layer) to the structure. The stiction reduction pad preferably prevents contact between the air-bearing surface and the disk or media as well as the lubricant on the disk or media. The stiction reduction pad also preferably reduces stiction forces between the slider and the disk or media. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a - c  are cross sectional views of a slider at intermediate points of a method according to an embodiment of the preset invention. 
       FIG. 2  is a cross-section of a slider showing an alternative embodiment of the stiction reduction pad of the present invention. 
       FIG. 3  is a bottom plan view of a first slider including stiction reduction pads constructed according to an embodiment of the present invention. 
       FIG. 4  is a bottom plan view of a second slider including stiction reduction pads constructed according to an embodiment of the present invention. 
       FIG. 5  is a bottom plan view of a third slider including stiction reduction pads constructed according to an embodiment of the present invention. 
       FIG. 6  is a cross-section of a fourth slider including stiction reduction pads constructed according to an embodiment of the present invention. 
       FIG. 7  is a bottom plan view of a fifth slider including stiction reduction pads constructed according to an embodiment of the present invention. 
       FIG. 8  is a bottom plan view of a sixth slider including stiction reduction pads constructed according to an embodiment of the present invention. 
       FIG. 9  is a diagram of a disk drive incorporating a slider designed according to an embodiment of the present invention. 
       FIG. 10  is a diagram of an actuator arm adapted to hold a slider designed according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a series of cross-sections are shown of an air-bearing slider after various intermediate steps of a method according to an embodiment of the present invention. In  FIG. 1   a , the initial configuration is shown including a slider body  10 , for example made of Al 2 O 3 TiC, an adhesion layer  12  (e.g., Si or SiO x ), and a DLC (diamond-like carbon) layer  14 . This structure is then masked in a known manner so that portions of the structure are exposed during an etching operation. The resulting structure is shown in  FIG. 1   b . According to an embodiment of the present invention, the stiction reduction pads are etched at the same time as the air-bearing surfaces using an ion milling or reactive ion etching process. In other words, the stiction reduction (SR) pads and the air bearing surfaces are masked out together during the etching process. After the etching process, the SR pads have a height on the order of 25 microinches or less in this example. 
   According to a first embodiment of the present invention, the stiction reduction pad is increased in height by first adding a second adhesion layer  16  (e.g., using a mask and sputtering method), which may or may not be necessary. Then a second DLC layer  18  is added. The second DLC layer  18  can be sputtered onto the stiction reduction pad structure by using a metal mask technology such as disclosed in U.S. Pat. No. 5,768,055 (the disclosure of which is hereby incorporated by reference in its entirety) or with traditional photolithographic techniques (such as the so-called “etched-back” or “lift-off” process). The completed structure according to this embodiment of the invention is shown in  FIG. 1   c . After building up the structure, the SR pads may have a height as short as 50 A but preferably on the order of 250 A to 400 A (Angstroms) over and above the height of the SR pad shown in  FIG. 1   b . By building the SR pads higher, there is a reduction in meniscus forces caused by the lubricant, which usually has a thickness on the order of 15-50 A. In this embodiment, the width dimensions of the pad are uniform between the first and second DLC layers, but the present invention is not limited in this manner. In this example, the pads have a diameter of between 25 and 60 micrometers. 
   According to a second embodiment of the present invention, as shown in  FIG. 2 , the second DLC layer may have dimensions that are different from the first DLC layer. In this embodiment, the first DLC layer  14  is only partially etched. A second adhesion layer  17 , which may or may not be necessary, and a second DLC layer  19  are deposited on top of the first DLC layer as described above. 
   Building the SR pads in the above-described manner, can help to insure that none of the air-bearing surface comes into contact with the disk or media (or the lubricant layer on the disk or media). By providing a small surface area of contact for the SR pads, stiction forces between the slider and the disk or media are reduced. In addition to reducing stiction forces, the SR pads also reduce dynamic or running friction when the slider is moving relative to a rotating disk. 
   In an alternative embodiment of the present invention, the first DLC layer and the first adhesion layer may be dispensed with and the SR pad can be built directly onto the slider body. Use of the SR pad of the present invention with various different slider configurations will be described in further detail below. 
   Referring to  FIG. 3 , a first slider design is shown that includes first and second ABS surfaces  21   a ,  21   b . A shallow step area  23  is present which surrounds the ABS structures. Four SR pads  27   a - d  are provided, constructed according to the methods described above. In this embodiment, each SR pad is built upon the shallow step area  23  and has a semi-circle cross-sectional shape. The flat, side portion of the SR pad is co-planar with a side edge of the shallow step area. 
   Referring to  FIG. 4 , a second slider design is shown that includes first and second air-bearing surface (ABS) rails  31   a ,  31   b . The slider also includes a shallow leading edge step  37  as well as two intermediate “wings”  34 ,  35  at the inside edges of the rails  31   a ,  31   b . In this embodiment, the leading edge  37  and the wings  34 ,  35  are etched to a substantially similar depth. Using the methods described above, the SR pads  36   a - d  are formed with a cylindrical shape. 
   Referring to  FIG. 5 , a third slider design is shown that includes first and second ABS rails  41 ,  42  as well as a leading edge step  43 . A rear pad  44  is also provided which is etched to the same depth as the leading edge step  43 . Three SR pads  45   a - c  are provided—two on the leading edge step  43  and one at the rear pad  44  using the methods described above. In this embodiment, the SR pads have a cylindrical shape with the exception of  45   c  which has a semi-circular shape. 
   Referring to  FIG. 6 , a cross section of a slider design is shown. As seen in  FIG. 6 , the SR pads  51  and  52  extend above the level of the ABS surfaces  53  and  54 , respectively. In this embodiment, the SR pads are placed on top of a shallow step  55  (e.g., of 250 nm). 
   The stiction reduction pads may be placed on the ABS surface, itself, and/or in the cavity (e.g., a subambient pressure cavity adjacent to the ABS surface. Referring to  FIG. 7 , a bottom view of a slider is shown where stiction reduction pads (e.g., pad  71 ) are placed in a leading edge step  72  of the slider. Stiction reduction pads (e.g., pad  73 ) may also be placed in the sub-ambient pressure cavity between the ABS surfaces. Referring to  FIG. 8 , another slider is shown where the stiction pads  81 ,  82  are placed in a leading edge step  83  of the slider as well as on the ABS surfaces  84 ,  85 . 
   In general, the placement of stiction reduction pads constructed according to the present invention are optimally placed when taking into account several rules. First, the height of the stiction reduction pad should be high enough from its base so as to avoid stiction due to miniscal forces. Generally, the height of each stiction reduction pad should be between 50 and 400 A. Second, the stiction reduction pad should not interfere with the flight of the slider. Accordingly, the width or area dimension of the pad should be small enough (e.g., a circle having a diameter between 25 and 60 micrometers) to prevent it from providing an air bearing surface for the slider, and to prevent it from having a large contact area. Also, the height of the pads should be controlled so that they do not contact the disk during slider flight. Third, the magnetic head must be the lowest point of the slider during flight. This requires that stiction reduction pads be placed towards the leading edge of the slider to take advantage of the pitch angle of the slider. In doing so, however, the slider may tip backward causing stiction instability. To avoid this stiction instability while keeping the magnetic transducer the lowes point during flying, the pad location and the pitch and the roll angles of the slider must be optimized. Otherwise, the slider could tip over during a stop operation leading to contact between the air bearing surface and the disk and increased stiction forces. With this criteria, the stiction reduction pads of the present invention should be able to keep starting friction at a minimum; avoid large stiction problems caused by contact between the air bearing surface and the disk; and maintain flying height stability for the slider. 
   Referring to  FIG. 9 , there is illustrated an example of a disk drive designated generally by the reference numeral  20  that may include the slider design of the present invention. The disk drive  20  includes a stack of storage disks  22   a - d  and a stack of read/write heads  24   a - h . Each of the storage disks  22   a - d  is provided with a plurality of data tracks to store user data. As illustrated in  FIG. 9 , one head is provided for each surface of each of the disks  22   a - d  such that data can be read from or written to the data tracks of all of the storage disks. The heads are coupled to a pre-amplifier. It should be understood that the disk drive  20  is merely representative of a disk drive system utilizing the present invention and that the present invention can be implemented in a disk drive system including more or less storage disks. 
   The storage disks  22   a - d  are mounted for rotation by a spindle motor arrangement  29 , as is known in the art. Moreover, the read/write heads  24   a - h  are supported by respective actuator arms  28   a - h  for controlled positioning over preselected radii of the storage disks  22   a - d  to enable the reading and writing of data from and to the data tracks. To that end, the actuator arms  28   a - h  are rotatably mounted on a pin  30  by a voice coil motor  32  operable to controllably rotate the actuator arms  28   a - h  radially across the disk surfaces. 
   Referring to  FIG. 10 , each of the read/write heads  24   a - h  is mounted to a head suspension assembly of the respective actuator arm  28   a - h  by a flexure element and comprises a magnetic transducer  25  mounted to a slider  26  having an air bearing surface (not shown in this figure), all in a known manner. As discussed in further detail below, the sliders  26  cause the magnetic transducers  25  of the read/write heads  24   a - h  to “fly” above the surfaces of the respective storage disks  22   a - d  for non-contact operation of the disk drive system, as discussed above. When not in use, the voice coil motor  32  rotates the actuator arms  28   a - h  to a ramp  33 , and a load beam of the actuator arms  28   a - h  moves up the load beam to a resting position away from the storage disk surfaces. 
   Although embodiments are specifically illustrated and described herein, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention. For example, though circular and semi-circular configurations are shown, other shapes for the SR pads can be used. Furthermore, though particular locations on the slider examples are shown, the location of the SR pads can be modified so as to optimize CSS performance.