Abstract:
A wafer comprises a transducer having an air-bearing surface (ABS) and including a magnetic structure characterized by a desired thickness, and having a bevel and a flare point a first distance from the ABS. The wafer further comprises a first electronic lapping guide (ELG), a second ELG, and a third ELG. The first ELG has a first edge a first distance from the ABS and a second edge a second distance from the ABS. The second ELG has a third edge a third distance from the ABS and a fourth edge the second distance from the ABS. The third ELG has a fifth edge a fourth distance from the ABS and a sixth edge the second distance from the ABS. At least one of the first distance and the second distance, at least one of the third distance and the second distance, and at least one of the fourth distance and the second distance correspond to an intersection between the bevel and the desired thickness.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/473,159, filed on May 27, 2009, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Conventional magnetic heads typically employ lapping to fabricate structures within the head. For example, lapping is typically used in processing a write transducer. More specifically, after pole formation, lapping may be used to remove a portion of the device to expose the air-bearing surface (ABS). Lapping determines the windage, the length measured from the ABS to the flare point of the pole of the write transducer. The windage, or nose length, is the distance from the ABS at which the angle the sides of the pole make with a plane parallel to the ABS increases. Similarly, lapping may be used in fabricating other structures in a head, such as the read sensor of a conventional read transducer. 
     In order to control lapping an electronic lapping guide (ELG) is typically used.  FIG. 1  depicts a top view of a conventional ELG  10 . The conventional ELG  10  is essentially a resistive stripe. Thus, the conventional ELG  10  is coupled with leads  14  and  16  that are used to determine the resistance of the conventional ELG  10 . The conventional ELG has a length l from the surface  12  being lapped. As lapping continues, the surface  12  is worn away, and the length of the conventional ELG  10  decreases. As the length is reduced, the resistance of the conventional ELG  10  increases. Using the resistance of the conventional ELG  10 , it can be determined when lapping should be terminated. 
       FIG. 2  is a flow chart depicting a conventional method  30  for performing lapping using the conventional ELG. The conventional method  30  is described in the context of the conventional ELG  10 . The resistance of the conventional ELG  10  is measured during lapping of the transducer, via step  32 . The current length of the conventional ELG  10  is determined based upon the resistance measured in step  32  and the sheet resistance of the conventional ELG  10 , via step  34 . The sheet resistance may be determined in a conventional manner using a conventional Van der Pauw pattern (not shown) provided on the substrate on which the magnetic transducer is to be fabricated. The conventional Van der Pauw test pattern is a well known pattern that may be used to determine sheet resistance of a stripe, such as the conventional ELG  10 . Thus, after step  34 , the length corresponding to a particular measured resistance for the conventional ELG  10  is known. Alternatively, step  34  could simply convert a desired windage to an ELG length and the ELG length to a desired target resistance of the conventional ELG  10 . 
     The lapping is terminated when the resistance of the conventional ELG  10  indicates that the desired length or target resistance of the conventional ELG  10  has been reached, via step  36 . Because the conventional ELG  10  and structure, such as a read sensor or pole, both exist on the transducer being lapped, the lengths of the conventional ELG  10  and the structure change with lapping. Consequently, the lengths of the read sensor or pole may also be set in step  36 . 
     Although the conventional method  30  and conventional ELG  10  function, the desired windage or other desired length may not be easily determined for certain structures. For example,  FIG. 3  depicts ABS, side, and top views of a conventional perpendicular magnetic recording (PMR) pole  40  that has a trailing edge bevel  42 . For simplicity,  FIG. 3  is not to scale. The conventional PMR pole  40  also has sidewalls  44  having a reverse angle and flare point  46 . Stated differently, the conventional PMR pole  40  has a top wider than its bottom. Because of the combination of the bevel  42  and sidewalls  44 , the windage, the track width, and the pole height change as part of the PMR pole  40  is lapped away. Thus, the geometry of the conventional PMR pole  40  make lapping to the desired windage (nl), track width (tw), and pole height (H) challenging. In addition, there are processing variations that occur for the separate processes used in determining the flare point  46 , bevel  42 , and sidewalls  44 . Variations in these processes may cause variations in the shape or location of these features of the conventional PMR pole  40 . It would be desirable, therefore, to compensate for these processing variations. Use of the conventional ELG  10  is not sufficient to do so. 
     Accordingly, what is needed is an improved method for providing and using an ELG in a magnetic transducer. 
     SUMMARY 
     A method and system for calibrating an electronic lapping guide (ELG) for least one transducer having an air-bearing surface (ABS) and a magnetic structure is described. The magnetic structure has a desired thickness, a bevel, and a flare point a distance from the ABS. The method and system include providing at least three ELGs. The first ELG has first and second edges first and second distances from the ABS. The first distance and/or the second distance correspond to an intersection between the bevel and the desired thickness. The second ELG has a third edge a third distance from the ABS and a fourth edge the second distance from the ABS. The third distance and/or the second distance correspond to the intersection between the bevel and the desired thickness. The third ELG has a fifth edge a fourth distance from the ABS and a sixth edge the second distance from the ABS. The first distance, the third distance, and the fourth distance correspond to a stripe height and an offset. The fourth distance and/or the second distance correspond to the intersection between the bevel and the desired thickness. The method and system also include measuring resistances of the first ELG, the second ELG, and the third ELG and calibrating the at least one ELG utilizing the offset and the resistances. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  depicts a conventional ELG as used in a conventional magnetic transducer. 
         FIG. 2  is a flow chart depicting a conventional method for performing lapping utilizing a conventional ELG. 
         FIG. 3  depicts a conventional PMR pole in a conventional PMR transducer. 
         FIG. 4  is a flow chart depicting an exemplary embodiment of a method for calibrating ELGs. 
         FIG. 5  depicts an exemplary embodiment of a transducer including a magnetic structure to be lapped using the ELGs. 
         FIG. 6  depicts another exemplary embodiment of a transducer including the ELGs. 
         FIG. 7  depicts another exemplary embodiment of a transducer including the ELGs. 
         FIG. 8  depicts another exemplary embodiment of a transducer including the ELGs. 
         FIG. 9  is a flow chart depicting an exemplary embodiment of a method for calibrating ELGs. 
         FIG. 10-11  depict another exemplary embodiment of a transducer including the ELGs during fabrication of the ELGs. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 4  is a flow chart depicting an exemplary embodiment of a method  100  for calibrating ELGs. For simplicity, some steps of the method  100  may be omitted.  FIGS. 5-8  depict exemplary embodiments of a portion of transducers  200 ,  200 ′, and  200 ″ with which the method  100  may be used. For clarity  FIGS. 5-8  are not to scale. The transducers  200 ,  200 ′, and  200 ″ each includes at least one magnetic structure  210  on which lapping is to be performed. The magnetic structure being fabricated is shown in  FIG. 5 . Thus, the transducer in  FIG. 5  is labeled  200 / 200 ′/ 200 ″. In the embodiment shown, the magnetic structure  210  is a PMR pole having a desired thickness, h, a bevel  212 , and a flare point  216  a distance (NL) from the ABS. The PMR pole  210  also includes sidewalls  214  having a reverse angle and is characterized by track width TW. The transducers  200 ,  200 ′, and  200 ″ may be part of a merged head including a read transducer and the write transducer. The transducers  200 ,  200 ′, and  200 ″ may thus be fabricated on wafer(s) which hold numerous transducers (not shown). Once fabrication is complete, or at some other point in processing, the transducers  200 ,  200 ′, and  200 ″may be separated from the wafer(s) on which they were fabricated and incorporated into a hard disk drive. The transducers  200 ,  200 ′, and  200 ″ may each reside on a slider (not shown). Although depicted in  FIG. 5  as PMR pole  210 , a magnetic structure may include any structure formed in a magnetic transducer. In various embodiments, other numbers of ELGs per transducer and/or per magnetic structure, including greater or less than three per transducer/magnetic structure, may be used. Further, the method  100  and transducers  200 ,  200 ′, and  200 ″ are described in the context of a flare point  216  and bevel  212 . The flare point corresponds to a point of interest from which distance to the desired ABS/surface, such as a windage, is measured. Consequently, in some embodiments, the magnetic structure fabricated using the method  100  may include some other feature corresponding to the flare point. Similarly, the bevel corresponds to a surface, top or bottom, of the magnetic structure  210  which is not perpendicular to the ABS or which otherwise defines a location of interest on the magnetic structure. The method  100  is also described in the context of single transducers  200 ,  200 ′, and  200 ″. However, the method  100  may be used for fabricating multiple transducers and/or multiple structures and may employ multiple ELG(s) at substantially the same time. The magnetic structure  210  being fabricated has may be desired to adjoin the ABS. Thus, in the embodiment shown, the lapping to be performed based on calibration using the method  100  proceeds to the ABS location (the location at which the ABS is formed). However, in another embodiment, the lapping may be used to expose another surface. 
     At least three ELGs having the desired offsets and stripe heights are provided, via step  102 . Thus, at least a first ELG, a second ELG, and a third ELG are formed. Step  102  may include depositing a resistive sheet and fabricating the three or more ELGs from the resistive sheet. The ELGs are configured so that one of their edges correspond to a particular position, such as the intersection between the bevel  212  and the desired thickness h. Such a position may correspond to the desired location of the ABS. However, another location such as the flare point may also be selected. The ELGs are also configured in step  102  such that another edge corresponds to the desired stripe height and an offset. For three ELGs, the other edges may correspond to the stripe height, the stripe height plus an offset, and the stripe height minus an offset. Stated differently, the locations of the other edges of the three or more ELGs may be expressed in terms of two variables (e.g. the stripe height and an offset). The ELGs may be fabricated by using a single mask and shifting the reticle a known amount between the different ELGs. Shirting the reticle may provide the most reliable determination of the offsets. Portions of the ELGs may be removed to the same location, such as the intersection of bevel and the desired height. However, in another embodiment, another method for providing the offsets may be used. 
       FIG. 6  depicts one embodiment of a transducer  200  after step  102  is performed. Thus, three ELGs  220 ,  230 , and  240  are shown. The ELGs  220 ,  230 , and  240  have edges  222 ,  232 , and  242 , respectively, at a location defined by the intersection of the bevel and the desired height. The other edges  224 ,  234 , and  244  are located at the stripe height plus an offset (SH+δ), the stripe height (SH) and the stripe height minus an offset (SH−δ) from the bevel location. Thus, each of the ELGs  220 ,  230 , and  240  has a common location and lengths that differ in known ways. 
       FIG. 7  depicts another embodiment of a transducer  200 ′ after step  102  is performed. Thus, three ELGs  220 ′,  230 ′, and  240 ′ are shown. The ELGs  220 ′,  230 ′, and  240 ′ have edges  224 ′,  234 ′, and  244 ′, respectively, at a known location. In the embodiment shown, the edges  224 ′,  234 ′, and  244 ′ may be at the flare point. The other edges  224 ′,  234 ′, and  244 ′ are located at the stripe height plus an offset (SH+δ), the stripe height (SH) and the stripe height minus an offset (SH−δ) from the flare point. Thus, each of the ELGs  220 ′,  230 ′, and  240 ′ has a common location and lengths that differ in known ways. 
       FIG. 8  depicts another embodiment of a transducer  200 ″ after step  102  is performed. In this embodiment, four ELGs  220 ″,  230 ″,  240 ″, and  250  are shown. The ELGs  220 ″,  230 ″,  240 ″, and  250  have edges  222 ″,  232 ″,  242 ″, and  252  respectively, at a known location. In the embodiment shown, the edges  222 ″,  232 ″,  242 ″, and  252  may be at the intersection between the bevel  212  and the desired height h (i.e. at the desired ABS). The other edges  224 ″,  234 ″,  244 ″, and  254  are located at the stripe height plus an offset (SH+δ), the stripe height (SH) the stripe height minus an offset (SH−δ), and the stripe height plus twice the offset (SH+2δ) from the bevel  212 -height intersection. The offset, d, may vary. In some embodiments, δ may be at least fifty nanometers and not more than one hundred nanometers. However, the offset δ may vary based on the structure  210  being fabricated and is generally desired to be in the process window range. Thus, each of the ELGs  220 ″,  230 ″,  240 ″, and  250  has a common location and lengths that differ in known ways. 
     The resistances of the ELGs are measured, via step  104 . Thus, for the transducer  200 , the resistances of the ELGs  220 ,  230 , and  240  are determined. For the transducer  200 ′, the resistances of the ELGs  220 ′,  230 ′, and  240 ′ are determined. For the transducer  200 ″, the resistances of the ELGs  220 ″,  230 ″,  240 ″, and  250  are determined. 
     The ELGs are calibrated using the offset and the resistances, via step  106 . Step  106  may include determining the stripe height, a target resistance of each ELG, and a sheet resistance of the ELGs. The calibration may be determined using a linear model for the resistances. For example, for the transducer  200 , the resistances of the ELGs  220 ,  230 , and  240  are given by: R 220 =R L +R S *{W/(SH+δ)}; R 230 =R L +R S *{W/(SH)}; and R 240 =R L +R S *{W/(SH−δ)}. These equations may be solved for the desired stripe height (SH), R S *W, and R L . In particular, SH=δ*(R 240 −R 220 )/(R 240 +R 220 −2*R 230 ); R S *W=2*δ*(R 240 −R 220 )*(R 240 −R 230 )*(R 230 −R 220 )/[R 220 +R 240 −2*R 230 ] 2 ; and R L =[2*R 220 *R 240 −R 240 *R 230 −R 230 *R 220 ]/(R 240 +R 220 −2*R 230 ). Consequently, the stripe height and thus the windage can be determined. If more than three ELGs are used, then higher order terms or other variables might be taken into account. Thus, the stripe height and the resistance coefficient, or resistance per unit length, may be determined. 
     Using the method  100 , the ELGs  220 ,  230 , and  240 ; the ELGs  220 ′,  230 ′, and  240 ′, and the ELGs  220 ″,  230 ″,  240 ″, and  250  may be calibrated. For example, the resistance per unit length of the ELGs may be determined based on the resistances, stripe height, and offset. In one embodiment, the stripe heights, SH, correspond to the desired windage because the back edge  234  of the non-offset ELG  230  is desired to be aligned with the flare point  216  of the PMR pole  210 . In addition to the stripe height, the actual windage may be calculated using the resistance per unit length and measured resistance of the ELGs during lapping. Because the actual windage may be determined, variations in processing and other inconsistencies may be taken into account. In particular, the actual windage values may be used in lapping the PMR pole  210  or other analogous structure. Consequently, better control of lapping and thus better control over the final structure may be achieved. Improvements in manufacturing and performance of the transducers  200 / 200 ′/ 200 ″ may thus be accomplished. 
       FIG. 9  is a flow chart depicting another exemplary embodiment of a method  150  for calibrating ELGs. For simplicity, some steps of the method  150  may be omitted.  FIG. 10-11  depict another exemplary embodiment of a transducer  300  including the ELGs  320 ,  330 , and  340  during fabrication of the ELGs. For clarity,  FIGS. 10-11  are not to scale. The transducer  300  includes a magnetic structure such as the PMR pole  210  depicted in  FIG. 5  and for fabrication of which the ELGs are desired to be calibrated. In the embodiment shown, the magnetic structure  210  is a PMR pole having a desired thickness, h, a bevel  212 , and a flare point  216  a distance (NL) from the ABS. The PMR pole  210  also includes sidewalls  214  having a reverse angle and is characterized by a track width TW. Note that  FIG. 5  depicts the PMR pole  210  after lapping to the ABS. The transducer  300  is analogous to the transducer  200 . The transducer  300  may thus be fabricated on wafer(s) which hold numerous transducers (not shown). Once fabrication is complete, or at some other point in processing, the transducers may be separated from the wafer(s) on which they were fabricated and incorporated into a hard disk drive. The transducer  300  may reside on a slider (not shown). Although depicted in  FIG. 5  as a PMR pole  210 , a magnetic structure may include any structure formed in a magnetic transducer. In various embodiments, other numbers of ELGs per transducer and/or per magnetic structure, including greater or less than three per transducer/magnetic structure, may be used. Further, the method  100  and transducers  200 ,  200 ′, and  200 ″ are described in the context of a flare point  216  and bevel  212 . The flare point corresponds to a point of interest from which distance to the desired ABS, such as a windage, is measured. Consequently, in some embodiments, the magnetic structure fabricated using the method  150  may include some other feature corresponding to the flare point. Similarly, the bevel corresponds to a surface, top or bottom, of the magnetic structure  210  which is not perpendicular to the ABS or which otherwise defines a location of interest on the magnetic structure. The method  150  is also described in the context of single transducer  300 . However, the method  150  may be used for fabricating multiple transducers and/or multiple structures and may employ multiple ELG(s) at substantially the same time. The magnetic structure  210  being fabricated has may be desired to adjoin the ABS. Thus, in the embodiment shown, the lapping to be performed based on calibration using the method  150  proceeds to the ABS location (the location at which the ABS is formed). However, in another embodiment, the lapping may be used to expose another surface. 
     A resistive sheet substantially coplanar with the desired thickness, h, of the PMR pole is provided, via step  152 . The ELG&#39;s are defined from the resistive sheet such that at least one of their edges are offset by known amounts, via step  154 . In one embodiment, step  154  is performed by shifting the reticle for each of the ELGs during mask formation, then using the mask formed by the shifted reticle to remove portions of the resistive sheet.  FIG. 10  depicts the transducer  300  after step  154  has been performed. Thus, ELGs  320 ,  330 , and  340  are shown. However, in another embodiment, another number of ELGs may be fabricated. Each ELG has the same depth, d. However, the front edges  322 ,  332  and  342  as well as the back edges  324 ,  334 , and  344  are offset due to the shift in the reticle. For example, the reticle would be at one location when the mask for the ELG  320  is formed, shifted by an amount corresponding to δ when the mask for the ELG  330  is formed, and shifted again by an amount corresponding to δ when the mask for the ELG  340  is formed. 
     One set of the edges is then set along a line, via step  156 . In one embodiment, portions of the ELGs  320 ,  330 , and  340  near the front edges  322 ,  332 , and  342 , respectively, are removed. In another embodiment, portions of the ELGs  320 ,  330 , and  340  near the back edges  324 ,  334 , and  344 , respectively, are removed.  FIG. 11  depicts the transducer  300  after step  158  is performed. In the embodiment shown, the front edges  322 ′,  332 ′, and  342 ′ have been set along the same line. In one embodiment, this is accomplished by exposing the ELGs  320 ,  330 , and  340  in the same manner as the PMR pole  210  during formation of the bevel  212 . Thus, the same processing step, such as an ion mill, that forms the bevel also forms the front edges  322 ′,  332 ′, and  342 ′. Thus, the front edges  322 ′,  332 ′, and  342 ′ are at locations corresponding to the intersection of the bevel  212  and the desired height, h, of the PMR pole. Further, the depth of the ELG  320 ′ is now SH+δ, the depth of the ELG  330 ′ is SH, and the depth of the ELG  340 ′ is SH−δ. In other embodiments, the offsets between the ELGs  320 ′,  330 ′, and  340 ′ may differ as long the relationships between the offsets are known. Thus, using steps  154  and  156 , the ELGs  320 ′,  330 ′, and  340 ′ are formed. 
     The resistances of the ELGs  320 ′,  330 ′, and  340 ′ are measured, via step  158 . The ELGs  320 ′,  330 ′, and  340 ′ are then calibrated using the offset, δ, and the resistances measured, via step  160 . In one embodiment, the linear model described above may be used in calibrating the ELGs  320 ′,  330 ′, and  340 ′. Thus, the stripe height, SH and offset d, may be calculated. Consequently, the windage (distance between the ABS and flare point  216 ) of the PMR pole  210  may be determined. 
     Using the method  150 , the ELGs  320 ′,  330 ′, and  340 ′ may be calibrated. More specifically, quantities such as the stripe height and resistance per unit length may be calculated. The lengths of the ELGs  320 ′,  330 ′, and  340 ′ during lapping may be determined based on the resistances. The final lengths of the ELGs  320 ′,  330 ′, and  340 ′ after lapping and thus the actual windage of the PMR pole  210  may also be determined. Because the actual windage may be determined, variations in processing and other inconsistencies may be taken into account. In particular, the actual windage values may be used in lapping the PMR pole  210  or other analogous structure. Consequently, better control of lapping and thus better control over the final structure may be achieved. Improvements in manufacturing and performance of the transducers  200 / 200 ′/ 200 ″ may thus be accomplished.