Abstract:
A method for finishing a pole tip trimmed read/write heat that includes a substrate with a pole tip structure having a shield, a shield/pole, and an outer pole. A gap region separates the pole and the shield/pole. First, pole tip trimming is performed to the read/write head to remove matter from the shield/pole, the pole, and the gap region. This defines a bridge composed of inward-facing extensions of the pole and shield/pole interconnected by an intervening region. This bridge separates recessed “trenches,” each formed by removing a contiguous mass from the shield/pole, the gap region, and the pole. Next, an overlayer is applied over the pole tip structure, filling the recessed trenches. The coated structure is then trimmed to remove all coating material overlying the shield/pole and pole. Trimming is continued to additionally remove a top layer of the protrusions of the pole and shield/pole to remove any rounded edges created by pole tip patterning, resulting in a more distinct write head. The refilled trenches of the recessed areas impart improved resistance to corrosive attack, to head-crashes from the release of accumulated debris, and to mechanical damage of the trimmed pole-tip structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 09/122,267, filed on Jul. 24, 1998, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to magnetic read/write heads for exchanging data with magnetic storage media. More particularly, the invention concerns a process for manufacturing a pole tip trimmed read/write head with increased resistance to wear and debris collection, sharp pole tip corners, and reduced tip recession by backfilling slider pockets and lapping slider surfaces to create a level air bearing surface with a more distinct write component. Another aspect of the invention is an apparatus embodying such a read/write head. 
     2. Description of the Related Art 
     In this modern information age, there is a tremendous volume of electronic data for people and computers to manage. The management requirements not only involve transmission, receipt and processing of this information, but storage of the data as well. And, with more data to store, computer users are demanding extremely high capacity digital data storage devices. People store digital data using magnetic disk drives, removable diskettes, magnetic tape, CD-ROMs, and many other forms. 
     One approach to increasing storage capacity is to increase the size of the storage device. Another, more challenging approach is to increase the density of the stored data. In this way, more information can be stored in the same size of storage device. Thus, engineers developing especially small systems such as laptop computers are motivated by two opposing forces: the need to make smaller and lighter storage devices on one hand, but the need to store more data on the other. 
     In the disk drive field, read/write head structure is a critical factor in the ability to build smaller drives. There are many known varieties of read/write head, many of which have been developed by International Business Machines Corp. (“IBM”), and described in issued patents assigned to IBM. One recent development is the Focused Ion Beam Machining (“FIBM”) technique, which is used to manufacture read/write heads with greater write density. Basically, the FIBM technique uses ion milling to reduce the size of certain head subcomponents, thereby increasing the storage density. 
     FIG. 1 depicts an exemplary slider  100  to help explain the FIBM technique more specifically. The slider  100  includes an air bearing surface (“ABS”)  102  which normally glides over a storage disk (not shown) separated by a thin cushion of air called an “air bearing” (not shown). In the illustrated example, the slider  100  moves in a direction  105  relative to the storage medium. The ABS  102  is raised with respect to a neighboring surface  104  that is recessed due to etching, ion milling, etc. As one example, the slider  100  may be composed of a mixture of aluminum oxide (Al 2 O 3 ) and titanium carbide (TiC). 
     The slider  100  has a leading edge  106  and a trailing edge  108 . Near the trailing edge  108  lies a pole tip structure  110 , which lies flush with the ABS  102  and contains circuit components that actually perform the read and write operations. These circuit components are deposited onto the trailing edge  108  of the slider  100 , which may also be called the “deposit end.” 
     FIG. 2 shows the pole tip structure  110  in greater detail. The pole tip structure  110  performs reading and writing operations with various subcomponents, such as poles, shields, read elements, and the like. In this example, the pole tip structure  110  includes a shield  200 , a combined shield/pole  202 , and a pole  204 . Between the shield  200  and shield/pole  202  lies a read element (not shown), such as a magnetoresistive (“MR”) stripe in the case of a MR head. Read operations are performed cooperatively by the shield  200 , MR stripe, and shield/pole  202 . Write operations are performed by the shield/pole  202  and the pole  204  cooperatively. 
     The FIBM technique uses a focused ion beam to remove portions of the shield/pole  202 , portions of the pole  204 , and portions of the material intervening between the shield/pole  202  and pole  204 . This technique is also called “pole tip trimming.” This creates recessed areas  206 . Pole tip trimming effectively narrows the sections of the pole  204  and shield/pole  202  that face each other. The resultant protrusions  250 - 251  of the shield/pole  202  and the pole  204  enable the slider  100  to write to a smaller area, therefore boosting storage density. The opposing protrusions  250 - 251  are joined by the connecting region of the ABS  102  form a bridge  208 . To further illustrate the pole tip structure  110 , FIG. 3 illustrates the structure  110  in perspective view. 
     Although the FIBM technique constitutes a significant advance and may even enjoy significant commercial and/or scientific recognition, IBM continually seeks to improve the performance and efficiency of disk drive systems, including the read/write head subcomponents. 
     SUMMARY OF THE INVENTION 
     Broadly, the present invention concerns a process for manufacturing a pole tip trimmed read/write head with increased resistance to wear and debris collection by backfilling slider pockets and lapping slider surfaces to create a level air bearing surface with a more distinct write component. 
     Initially, the read/write head includes a substrate with an air bearing surface that includes a pole tip structure. The pole tip structure has a shield, a shield/pole substantially parallel to the shield, and an outer pole substantially parallel to the shield/pole. A gap region separates the pole and the shield/pole. First, pole tip trimming is performed to the read/write head to remove matter from the shield/pole, the pole, and the gap region. This defines a bridge composed of protrusions of the shield/pole and the pole joined by a connecting region of the intervening gap region. The bridge separates recessed areas, each formed by removing a contiguous mass from the shield/pole, the gap region, and the pole. 
     Next, thin film deposition is performed to apply a coating material over the pole tip structure, filling the recessed areas. The coated surface is then trimmed sufficiently to remove all coating material overlying the shield/pole and pole. Trimming may be performed by lapping or polishing, for example. Trimming is continued to additionally remove a top layer of the protrusions of the pole and shield/pole, and to remove any rounded edges created by pole tip trimming, resulting in a more distinct write head. 
     Accordingly, in one embodiment the invention may be implemented to provide a method to manufacture a pole tip trimmed read/write head. In another embodiment, the invention may be implemented to provide an apparatus, such as a pole tip trimmed read/write head, or a disk drive system utilizing such a head. 
     The invention affords its users with a number of distinct advantages. First, the invention reduces the possibility of collecting debris in recessed areas of a pole tip patterned slider. In turn, this helps reduce friction between the slider and disk, avoiding head/disk wear. Avoiding head/disk wear helps prevent data loss resulting from head/disk damage. Additionally, eliminating a collection site for debris imparts additional benefits to the head, such as resistance to corrosive attack of the pole-tips due to entrainment of corrosive debris, and resistance to head crashes caused by accumulated debris dropping onto the disk. 
     A further advantage of the invention is also provided by the encapsulation of the recessed trenches caused by pole tip trimming techniques such as FIBM. Namely, the encapsulation of the trenches helps avoid any corrosion hazards posed by corrosive materials such as gallium, which may be implanted in the pole tip structure during pole tip trimming. By encapsulating the trimmed trenches, these corrosive materials are sequestered under an overlayer that reduces the likelihood of their release in a reactive form, especially in proximity to the trimmed pole tips themselves. 
     The invention also helps reduce the recession of the pole and shield/pole regions from the ABS, which helps maintain the strength of both write and read signals. By maintaining the strength of these signals, the invention promotes a high storage density, enabling a smaller overall storage device. The invention also provides a number of other advantages and benefits, which should be apparent from the following description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view diagram of a known slider, as seen from the ABS side. 
     FIG. 2 is an enlarged plan view showing the pole tip area of a known slider, as seen from the ABS side. 
     FIG. 3 is a perspective view showing the pole tip area of a known magnetic disk drive read/write head, as seen from the ABS. 
     FIG. 4 is a flowchart showing a sequence of operational steps for creating a backfilled etched read/write head in accordance with the present invention. 
     FIGS. 5A-5D show cross-sectional views (taken along the line  5 — 5  of FIG. 2) of a slider during various stages of backfilling and lapping, in accordance with the invention. 
     FIG. 6A is a plan view depicting a slider with a backfilled and lapped pole tip in accordance with the invention, as seen from the ABS side of the slider. 
     FIG. 6B is a perspective view of a slider with a backfilled and lapped pole tip structure in accordance with the invention, as seen from the ABS side of the slider. 
     FIG. 7 is a block diagram of a disk drive system in accordance with the invention. 
    
    
     DETAILED DESCRIPTION 
     The nature, objectives, and advantages of the invention will become more apparent to those skilled in the art after considering the following detailed description in connection with the accompanying drawings. As mentioned above, the invention concerns a pole tip trimmed read/write head with increased resistance to wear and debris collection, sharp pole tip corners, and reduced pole tip recession, due to backfilled slider pockets and lapped slider surfaces creating a level air bearing surface. Another aspect of the invention is a disk drive system utilizing such a read/write head. A different aspect of the invention is a process for manufacturing such a pole tip trimmed read/write head. 
     Analysis of Pole Tip Trimmed Heads 
     Despite the greater storage density afforded by the pole tip trimmed structure  110 , the present inventors have nonetheless analyzed this configuration with an eye toward any possible improvements. In this endeavor, the inventors have considered the otherwise unrecognized possibility that the recessed areas  206  might collect debris, such as any contamination present in the disk drive environment, powder created by occasional contact between disk and slider, etc. As considered by the inventors, such debris might possibly create friction between the slider and disk surface, accelerating head and disk wear. Accelerated head wear may increase the likelihood of a head/disk collision, or in extreme cases generate friction that damages the disk surface and destroys stored data. 
     Another possible limitation of the structure  110  concerns recession of the bridge region  208  with respect to the ABS  102 , this bridge  208  being made up of the inward-facing extensions  250 - 251  of the shield/pole  202  and the pole  204  and the area in between. As recognized by the present inventors, the normal FIBM process removes a significant amount of material from the extensions  250 - 251 , causing an ultimate recession with respect to the rest of the ABS  102  and pole tip structure  110 , which are otherwise generally planar. This recession effectively increases the magnetic clearance between the pole tip structure  110  and the recording medium. Since the strength of stored signals is inversely proportional to flying height, the recessed bridge  208  writes weaker signals to the disk. And, weaker signals cannot be stored with the same density as stronger signals, since these weaker signals are less distinct. Therefore, with less storage density, the size of the storage device employing the slider  100  is increased. This is generally undesirable in most situations, and especially so in extremely compact storage devices such as laptop computer disk drives. 
     A related problem discovered by the inventors is that due to FIBM, the extensions  250 - 251  exhibit rounded edges, rather than sharply defined edges. As recognized by the inventors, this may degrade the track-to-track storage resolution, further contributing to poor storage density. 
     Manufacturing Process 
     Having made the analysis described above, the present inventors responded by developing an improved read/write head that avoids the foregoing limitations of known pole tip trimmed heads. One aspect of the invention is a method for manufacturing a pole tip trimmed read/write head exhibiting increased resistance to wear and debris collection due to backfilled slider pockets and lapped slider surfaces, creating a level air bearing surface. 
     FIG. 4 shows a process  400  illustrating one example of the method aspect of the present invention. This sequence describes steps for modifying a read/write head to create the backfilled, lapped, and pole tip trimmed head of the invention. The sequence  400  is explained in terms of the slider  100  shown in FIGS. 1-6B. First, step  402  obtains a read/write head with read/write subcomponents such as the pole tip structure  110 . The structure  110  includes a shield  200 , shield/pole  202 , and an “outer” pole  204 . As an example, the shield  200  may be manufactured from a material such as SENDUST, which is an alloy of iron, aluminum, and silicon. The shield/pole  202  and pole  204  may use a material such as PERMALLOY, for instance. Although not shown, the pole tip structure  110  may include other features such as a MR stripe. These and a variety of other techniques and materials may be used in constructing the slider  100 , as will be apparent to those of ordinary skill in the relevant art. 
     In accordance with the invention, the components of the slider  100 , and especially the pole tip structure  110 , may be slightly thicker than usual. This may be achieved, for example, by limiting the amount of lapping performed during finishing of the slider  100 . As one example, the shield  200 , shield/pole  202 , and pole  204  may be about 0.5 microns thicker than normal. This extra thickness anticipates the additional lapping performed to slider  100  later, as described below. 
     Step  404  performs pole tip trimming upon the pole tip structure  110  to create the  20  recessed areas  206  divided by the bridge  208 . The recessed areas  206  may also be referred to as “trenches.” As an example, step  404  may use the FIBM technique, ion milling, reactive ion etching (RIE), or another suitable chemical, mechanical, chem-mechanical, or other process. After step  404 , the pole tip structure  110  appears as shown by FIG. 5A, which shows a cross-section of the pole tip structure  110  along the line  5 — 5  of FIG.  2 . Specifically, FIG. 5A shows recessed areas  206  separated by the extension  251  of the pole  204 . Outside the recessed areas  206  lie the regions  506  and  508  of the gap or other material between the pole  204  and shield/pole  202 . The recessed areas  206  may exhibit a depth of about one micron with respect to the outlying regions  506 ,  508 . As a result of the step  404 , and particularly the FIBM technique, the extension  251  of the pole  204  exhibits rounded corners  505 . Although not shown in FIGS. 5A-5D, these rounded corners are also present on the extension  250  of the shield/pole  202  as well as the to intervening gap region joining the extensions  250 - 251 . 
     The inventors have also observed a material height difference  530  between the extension  251  and the regions  506  and  508 , which are level with the original ABS  102 . This additional recession also occurs for the complementary extension  250  of the shield/pole  202 . 
     After step  404 , step  406  applies an overlayer to the slider  100  coating the pole tip structure  110  and backfilling the recessed areas  206 . As an example, step  406  may employ thin film deposition such as alumina sputtering, applying about one micron of the same material that composes the slider  100 . After step  406 , the pole tip structure  110  appears as shown in FIG.  5 B. Namely, the overlayer  510  overlies the extension  251  and the outlying regions  506 ,  508 . The overlayer  510  also fills the recessed regions  206 . Although not shown in FIG. 5B, the overlayer  510  also overlies the extension  250  of the shield/pole  202 , and the material between the extensions  250 ,  251 . Although not shown, the overlayer  510  also overlies some or all of the remainder of the ABS  102 . 
     After step  406 , step  408  trims the ABS  102  by lapping, grinding, slicing, chemical-mechanical polishing, mechanical polishing, chemical-mechanical planarization, or another suitable thickness-reducing technique. This trimming removes a substantially uniform thickness from the pole tip structure, in planar fashion. During the process of trimming in step  408 , the overlayer material  510  overlying the pole tip structure  110  is first removed, as shown by FIG.  5 C. With continued trimming, however, the overlayer as well as the pole tip structure  110  is ultimately trimmed to a depth  512 . Trimming of the pole tip structure past the surfaces of the protrusion  251  and outlying regions  506 / 508  effectively sharpens the edges of the protrusion  251  by removing its rounded corners  505 . Rounded corners of the extension  250  (not shown) are similarly sharpened. Since the trimming of step  408  effectively creates a new pole tip structure surface (at the level  512 ), the height difference  530  (FIG. 5A) is eliminated from the extensions  250 - 251  of the shield/pole  202  and pole  204 , respectively. 
     When trimming is complete, the pole tip structure  110  appears as shown in FIG.  5 D. Namely, the structure exhibits a newly shaped pole extension  518  with distinct corners. Moreover, the recessed regions  206  are replaced by backfilled areas  514 - 515 . As one example, the trimming of step  408  may remove a total of about one micron of material, leaving extensions  250 - 251  of about one half micron in height. Although not shown, trimming may also reduce the coating material and the underlying structure of the shield  200  and ABS  102 . 
     After step  408 , the sequence  400  ends in step  410 . With the sequence  400  complete, the finished pole tip structure appears as shown in FIGS. 6A (plan view) and FIG. 6B (perspective view). Namely, the finished pole tip structure  600  includes a shield  602 , a shield/pole  604 , and a pole  606 , all with slightly reduced thickness. The shield/pole  604  and pole  606  include narrowed inward pointing extensions  618 / 620  with sharply defined corners. Moreover, the formerly recessed regions  206  are now backfilled areas  610 . Thus, the region between the extensions  618 / 620  is substantially flat. 
     Hardware Structure 
     Read/Write Head 
     In contrast to the manufacturing process described above, a different aspect of the invention is a pole tip trimmed read/write head with increased resistance to wear and debris collection due to certain features. This apparatus is shown in FIGS. 6A-6B, and includes the pole tip structure  600  that may be manufactured as shown above. The backfilled slider pockets  610  are resistant to debris collection, in contrast with the recessed areas present in prior pole tip trimmed sliders. The elimination of a collection site for the debris imports additional benefits to the head such as resistance to corrosive attack of the pole-tips due to entrainment of corrosive debris and resistance to head crashes caused by accumulated debris dropping onto the disk from the trimmed trench. Furthermore, the invention helps avoid any hazards posed by gallium or other corrosive materials implanted as a result of the FIBM trimming process. By encapsulating the trimmed trenches, this gallium is sequestered under an encapsulating layer, reducing the likelihood of its release in a reactive form, especially in proximity to the trimmed pole-tips themselves. Furthermore, the distinct regions extending from the pole  606  and shield/pole  604  provide a write head capable of writing signals with greater resolution. This characteristic is enhanced due to the distinct edges and the decreased pole tip recession of these extensions, as shown above. 
     Disk Drive System 
     Another hardware aspect of the invention concerns a disk drive system, utilizing the read/write head discussed above. FIG. 7 shows a disk drive system  700  embodying the present invention. The disk drive system  700  includes at least one rotatable magnetic disk  712  supported on a spindle  714  and rotated by a disk drive motor  718 . The magnetic recording media on each disk is in the form of an annual pattern of concentric data tracks (not shown) on the disk  712 . 
     At least one slider  713  is positioned near the disk  712 , each slider  713  supporting one or more magnetic read/write heads  721 , where the head  721  incorporates an MR sensor for reading information. As the disks rotate, the slider  713  is moved radially in and out over the disk surface  722  so that the heads  721  may access different portions of the disk where desired data is recorded. 
     Each slider  713  is attached to an actuator arm  719  by means of a suspension  715 . The suspension  715  provides a slight spring force that biases the slider  713  against the disk surface  722 . Each actuator arm  719  is attached to an actuator mechanism  727 . The actuator mechanism  719 , for example, may be a voice coil motor (“VCM”) comprising a coil movable within a fixed magnetic field, where the direction and speed of the coil movements are controlled by the motor current signals supplied by a controller  729 . 
     During operation of the disk drive system  700 , the rotation of the disk  712  generates an air bearing between the slider  713  and the disk surface  722 , which exerts an upward force or “lift” on the slider. The surface of the slider  713  that includes the head  721  and faces the surface  722  is referred to as an air bearing surface (“ABS”). The air bearing counter-balances the slight spring force of the suspension  715  and supports the slider  713  off and slightly above the disk surface by a small, substantially constant spacing during normal operation. 
     In operation, the various components of the disk storage system are controlled by control signals generated by the control unit  729 . These control signals include, for example, access control signals and internal clock signals. As an example, the control unit  729  may include various logic circuits, storage, and a microprocessor. The control unit  729  generates-control signals to control various system operations such as drive motor control signals on line  723  and head position and seek control signals on a line  728 . The control signals on the line  728  provide the desired current profiles to optimally move and position the slider  713  to the desired data track on the disk  712 . Read and write signals are communicated to and from read/write heads  721  by means of a recording channel  725 . 
     The above description of the magnetic disk storage system and accompanying illustration of FIG. 7 are for representation purposes only. Ordinarily skilled artisans (having the benefit of this disclosure) should recognize various additions or other changes that may be made to the system  700  without departing from the invention. Moreover, disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders. 
     OTHER EMBODIMENTS 
     While the foregoing disclosure shows a number of illustrative embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.