Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to magnetic recording heads used, for example, in disk drives; and more particularly the invention relates to a removable lapping guide used during lapping of a magnetic recording head. 
     2. Description of the Background Art 
     Disk drives using magnetic recording of digital information store most of the information in contemporary computer systems. A disk drive has at least one rotating disk with discrete concentric tracks of data. Each disk drive also has at least one recording head typically having a separate write element and read element for writing and reading the data on the tracks. The recording head is constructed on a slider and the slider is attached to a suspension. The combination of the recording head, slider, and suspension is called a head gimbal assembly. In addition, there is an actuator which positions the recording head over the specific track of interest. The actuator first rotates to seek the track of interest and after positioning the recording head over the track maintains the recording head in close registration to that track. The disk in a disk drive has a substrate and a magnetic layer on the substrate for magnetic recording. The slider carrying the recording head has a disk facing surface upon which an air bearing is constructed. The air bearing allows the slider to float on a cushion of air and to be positioned close to the disk surface. Alternatively, the slider surface facing the disk can be adapted for partial or continuous contact with the disk. 
     Recording heads are constructed on a wafer using thin film methods. After the construction of the recording heads, the wafer is typically sliced into rows. Each row will typically have 20 to 80 recording heads. The row is first lapped in order to give the final dimensions to the read and write elements. After lapping, the air bearings are then simultaneously constructed on one surface of the row. Individual sliders are then separated from the row. For very high recording density, row lapping does not deliver the required dimensional control of stripe height of the read element and throat height of the write element. 
     Improved read element stripe height control is achieved by separating individual sliders from the row prior to lapping and construction of the airbearing. This better control of stripe height is important because each new disk drive product generally has read elements which are smaller than those of previous products. This ever decreasing size of each new read element exacerbates the difficulty of controlling the stripe height during lapping. 
     Electrical lapping guides have been used to monitor the progress of lapping. Electrical lapping guides are thin films of resistive metal. These stripes of metal are partially removed during the lapping of the slider. Thus by measuring the resistance of the electrical lapping guide during lapping the progress of lapping the read element may be monitored. For example, U.S. Pat. No. 5,588,199 discloses a lapping guide for use with a single slider wherein the lapping guide is connected in parallel with the read element. 
     What is needed is a lapping guide which is suitable for use with individual sliders, offers an unambiguous indication of lapping progression, does not interfere with the read or write elements, and is capable of being removed or inactivated after the lapping has been completed. 
     SUMMARY OF THE INVENTION 
     The present invention provides an electrical lapping guide for use with individual sliders. The electrical lapping guide thus provided allows lapping to be monitored without the need for additional connection pads and without causing interference with the read or write elements. 
     In a preferred embodiment, the electrical lapping guide is a resistive thin film member having a relatively high resistance. One of the electrical leads forming a connection to the electrical lapping guide is connected to one of the read element connection pads. The other electrical lead forming a connection to the electrical lapping guide is connected to one of the write element connection pads. By these electrical connections, the resistance monitored during lapping unambiguously indicates the state of the electrical lapping guide. 
     One of the electrical connections to the electrical lapping guide can be shallow with respect to a surface of the slider and therefore removable by ion milling or reactive ion etching after lapping is complete. Removing the electrical circuit of the electrical lapping guide can eliminate interference with subsequent use of the read or write elements in the recording head. 
     Other aspects and advantages of the invention will become apparent from the following detailed description, which when taken in conjunction with the drawings, illustrate by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a recording head and disk used in magnetic recording; 
     FIG. 2 a  illustrates a perspective view of a slider; 
     FIG. 2 b  illustrates a side view of a slider; 
     FIG. 2 c  illustrates a bottom view of a slider; 
     FIG. 3 illustrates the trailing surface of a slider having an electrical lapping guide; 
     FIG. 4 a  illustrates an embodiment of an electrical lapping guide before lapping; 
     FIG. 4 b  illustrates an embodiment of the electrical lapping guide after lapping; 
     FIG. 4 c  illustrates an embodiment of the electrical lapping guide prepared for removal of an electrical lead; 
     FIG. 4 d  illustrates an embodiment of the electrical lapping guide after removal of a portion of the electrical lead; 
     FIG. 5 a  illustrates an example of the location of the window in the air bearing mask; 
     FIG. 5 b  illustrates an alternate example of the location of the window in the air bearing mask; 
     FIG. 6 illustrates the measurement of resistance of an electrical lapping guide; and, 
     FIG. 7 illustrates a low diagram of the method of using an electrical lapping guide. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in the drawings and described in detail below, the invention is embodied in an electrical lapping guide for individual sliders. The resistance of the electrical lapping guide may be monitored during lapping, providing an unambiguous indication of lapping progression. After lapping is complete, a connection to the electrical lapping guide may be removed thus causing the electrical lapping guide to become electrically inactive. 
     FIG. 1 shows a slider  102  as attached to a suspension  104  and flying above the surface  106  of the disk  108 . When operating, the disk  108  spins in a direction indicated by arrow  110 . The slider  102  typically has a disk facing side (not shown) upon which the air bearing is constructed. This side of the slider is sometimes referred to as the air bearing surface although the air bearing surface itself usually includes a plurality of recesses formed disk facing side of the slider  102  to control aerodynamic pressure forces between the slider  102  and the disk surface  106 . The recording head  112  is normally constructed on the trailing surface  114  of the slider  102 . The leading edge of the air  105  bearing surface has an optional tapered portion  116 , which helps in forming a uniform air bearing. 
     FIG. 2 a  shows a perspective drawing of a typical slider  202 . FIG. 2 a  shows the front surface  204  of the slider  202 , the optional tapered region  206 , and the air bearing  208 . The optional tapered region  206  in FIG. 2 a  is illustrated as reference  116  in FIG.  1 . There are many air bearing designs differing somewhat in geometrical features. The common aspect of air bearing designs is that most are comprised of two or more surfaces which are recessed or offset from one another. In the example shown in FIG. 2 a  there are three such surfaces. The first surface is shown as segments  210 ,  212 , and  214 . These segments are not contiguous but lie in approximately the same plane and therefore are referred to as a single surface. The next surface is indicated by segments  216 ,  218 , and  220 . These segments are also not contiguous but lie in approximately the same plane. The plane defined by segments  216 ,  218 , and  220  is recessed compared with the plane defined by segments  210 ,  212 , and  214 . The recessed or offset distance varies according to the design requirements of the air bearing and is typically from about 0.1 to 0.5 μm. The third surface  222  in FIG. 2 a  is typically less than 4.0 μm recessed or offset from the plane defined by segments  210 ,  212 , and  214 . The location of the recording head  224  is near the trailing edge  226  of the air bearing  208 . Recessed surfaces are typically formed by ion milling or reactive ion etching through openings in appropriate masks. 
     FIG. 2 b  illustrates a side view of the slider  202 . The front surface  204  and the optional tapered region  206  are viewed in profile. The recessed distance  226  of the plane defined by segments  210 ,  212 ,  214  and the plane defined by segments  216 ,  218 , and  220  is illustrated. Also the recessed distance  228  of the plane defined by segments  216 ,  218 ,  220  and the plane shown by reference number  222  is illustrated. 
     FIG. 2 c  illustrates a view of the air bearing  208  side of the slider  202 . The optional tapered region  206  is illustrated. The surface defined by segments  210 ,  212 , and  214  is illustrated. The surface defined by segments  216 ,  218  and  220  is illustrated. And finally, the surface  222  is illustrated. 
     FIG. 3 illustrates one embodiment of the invention. FIG. 3 shows the trailing surface  302  of a typical slider  300 . Constructed on the trailing surface  302  is a read element  304 , two connection pads  306 ,  308  connected by metallic conductors  310  to the read element  304 , a write element (not shown), two connection pads  312 ,  314  connected by metallic conductors  316  to the write element (not shown), and an electrical lapping guide  318 . The electrical lapping guide  318  is a resistive thin film member with two conductive leads  320 ,  322 . One lead  320  connects the electrical lapping guide  318  to one of the read element connection pads  308 . The other conductive lead  322  connects the electrical lapping guide  318  to one of the write element connection pads  314 . For visual clarity in FIG. 3, the conductors  310 ,  316  for the read element  304  and write element (not shown) are not shown in complete detail. Although one specific example of an electrical lapping guide is illustrated in FIG. 3, the invention is not limited by that specific example. Other specific arrangements are possible without departing from the scope of the invention. For example the electrical lapping guide can be on the left side of the trailing surface of the slider and the connection pads may have a different order. Alternately, additional dedicated connection pads may used, however there is limited space on the trailing surface of the slider for additional pads. 
     Referring again to FIG. 3 the resistance of the electrical lapping guide  318  is measured between the connection pads  308 ,  314  during lapping. Since neither the read element  304  nor the write element (not shown) is in parallel connection with these two pads  308 ,  314  during lapping, the measured resistance is an unambiguous indication of the state of the electrical lapping guide  318 . 
     FIGS. 4 a, b, c , and  d  illustrate the electrical lapping guide  400  in more detail. FIG. 4 a  illustrates a resistive thin film member  402  having two ends and electrical leads  404 ,  406  attached to the ends of the resistive thin film member  402 . The resistive thin film member  402  is conveniently formed along with the read element ( 304  in FIG. 3) and of the same materials as the read element. Forming the resistive thin film member  402  along with the read element greatly simplifies the task of aligning the resistive thin film member  402  with the read element. Proper alignment is necessary for the resistance of the electrical lapping guide to indicate the lapped state of the read element. If alignment is not adequate the resistance of the resistive thin film member  402  during lapping may not be an adequate indication of the stripe height of the read element. Alternatively the resistive thin film member  402  may be formed of other resistive materials using different process steps. If different process steps are used to make the read element and the electrical lapping guide, the task of achieving good alignment may be more difficult. The electrical leads to the resistive thin film member  402  are conveniently formed of tantalum, tungsten, titanium, alloys of nickel-iron, or other suitable materials. Preferably, the resistivity and thickness of the electrical leads  404 ,  406  are chosen such that the resistance of the electrical leads  404 ,  406  is substantially less than the resistance of the resistive thin film member  402 . During lapping, a portion of at least one of the leads  404  and the resistive thin film member  402  will be removed. The dashed line  408  in FIG. 4 a  indicates an example of the extent of final lapping. FIG. 4 b  illustrates the electrical lapping guide  400  after lapping to the location indicated by the dashed line  408 . 
     At least one of the electrical leads  404  to the resistive thin film element  402  has a shallow portion  410  to facilitate removal. It is desirable to remove the electrical connection to the resistive thin film member  402  in order to avoid electrical interference during the subsequent use of the read or write element. The preferred method of removing the shallow portion  410  of the electrical lead  404  is to form a window  412  in the mask  414  which is used to construct the air bearing. FIG. 4 c  illustrates an example of utilizing a window in the air bearing mask to expose the shallow portion  410  of the electrical lead  404  during ion milling or reactive ion etching. Ion milling may be used to mill away the shallow portion  410  of the electrical lead  404  and can be achieved with the ion milling used to create the air bearing thus conserving the number of process steps. Alternatively reactive ion etching using an effective gas mixture may be used to etch away the shallow portion  410  of the electrical lead  404 . Electrical leads formed from tantalum, tungsten, and titanium are readily removed with many reactive ion etching gas mixtures. If an alloy of nickel and iron is used as the material in the electrical leads then a reactive ion etching using a gas mixture of CO/NH 3  is effective. Very selective differential etch rates are possible with reactive ion etching methods because the etch rate of the usual alumina-titanium carbide material used for sliders is very low. One alternate removal method is using a laser to ablate the shallow portion of the electrical lead. Another alternate removal method is to use high current to melt the shallow portion of the electrical lead. The magnitude of current necessary to melt the shallow portion of the electrical lead depends on the material and the thickness of the material. The magnitude of current may be as low as 10 mA and as high as a few tens of milliamps. The duration of the current need be only a few milliseconds. These latter two methods are effective but require additonal apparatus. 
     Again referring to FIGS. 4 a, b, c , and  d , when using ion etching to remove the shallow portion  410  of the electrical lead  404  the height  416  of the shallow portion  410  should generally be less than 4 μm and preferably less than 1 μm. When using reactive ion etching to remove the shallow portion  410  of the electrical lead  404 , the height  416  of the shallow portion  410  should generally be less than 1 μm. Therefore in general, it is preferable that the height  416  of the shallow portion  410  of the electrical lead  404  (after lapping and before removal) is limited to approximately 1 μm or less. Electrical leads with a height significantly greater than one micrometer may not be completely removed during milling or etching. 
     FIG. 4 d  illustrates the absence of the shallow portion of the electrical lead  404  after removal thereof. 
     FIG. 5 a  shows a detailed view of an example of a window in the air bearing mask used to expose the electrical lapping guide for removal. The trailing pad  502  (also illustrated with reference  214  in FIGS. 2 a, c ) of the air bearing is illustrated in FIG. 5 a . The shielded read element  504  is usually sandwiched in a insulating material  506  on the trailing surface  520  of the slider. The electrical lapping guide  508  is preferable coplanar with the read element  504 . When the mask for the air bearing is applied to the disk facing surface of the slider a small window  510 , indicated by the area enclosed by the dashed line  512 , is used to expose the electrical lapping guide  508 . Preferably the area exposed by the window  510  in the mask is only a few micrometers in extent so that the pocket or void created when the shallow portion of the electrical lead is milled or etched has little or no effect on the performance of the air bearing. The expanded perspective view  514  in FIG. 5 a  illustrates the enclosed pocket  516  remaining in the trailing pad  502  after removal of the shallow portion of the electrical lead. 
     FIG. 5 b  illustrates an alternate placement of the window  510 . In this embodiment, the window  510  in the mask extends beyond the trailing edge  518  of the trailing pad  502 . The pocket  516  remaining in the trailing pad  502  after removal of the shallow portion of the electrical lead extends to the trailing surface  520  of the slider. The pocket  516  is not enclosed toward the trailing surface  520  and accordingly may have a slight effect on the performance of the air bearing. 
     FIG. 6 illustrates a typical apparatus used to collect resistance information from the electrical lapping guide. 
     Typically a constant current  602  is passed through the resistive thin film member  604 . The voltage  606  across the resistive thin film member is then measured. The relationship between the measured voltage  606  and the height  608  and width  610  of the resistive thin film member  604  is given by: 
     
       
           V= ( IρW )/ h,    
       
     
     Where I is the current, ρ is the sheet resistance of the resistive thin film member, W is the width of the resistive thin film member, and h is the height of the thin film member. Those skilled in the art will recognize that there is a small correction which can be made for the finite resistance of the electrical leads. 
     The method of using the present invention is summarized in FIG.  7 . First a resistive thin film member ( 418  in FIG. 4 a ) is formed  702  on the trailing surface ( 302  in FIG. 3) of a slider ( 300  in FIG.  3 ). One electrical lead ( 320  in FIG. 3) is formed connecting the resistive thin film member ( 418  in FIG. 4 a ) with a read element connection pad ( 308  in FIG.  3 ). One electrical lead ( 322  in FIG. 3) is formed connecting the resistive thin film member ( 418  in FIG. 4 a ) with a write element connection pad ( 314  in FIG.  3 ). One of the electrical leads ( 404  in FIG. 4 a ) is formed  704  having a shallow portion ( 410  in FIG. 4 b ) to facilitate removal. During lapping the resistance of the electrical lapping guide ( 318  in FIG. 3) is measured  706 . After lapping is complete, the shallow portion ( 410  in FIG. 4 b ) of the portion of the electrical lead ( 404  in FIG. 4 a ) is removed  708 . 
     From the foregoing it will be apparent that the electrical lapping guide provided by the invention offers several advantages. For example, the electrical lapping guide is readily suitable for use on an individual slider; no additional connection pads are required; and, the connection to the electrical lapping guide may be removed after lapping to avoid interference with subsequent use of the read or write element. Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific embodiments thus explicitly described. The invention is limited only by the claims.

Technology Category: g