Abstract:
A method and system provide a storage device. A plurality of read sensor stacks for each reader of the storage device are provided. The read sensor stacks are distributed along a down track direction and offset in a cross-track direction. A plurality of electronic lapping guides (ELGs) are provided for the read sensor stacks. The read sensor stacks are lapped. Lapping is terminated based on signal(s) from the ELG(s).

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application is a divisional of U.S. application Ser. No. 14/560,731, filed on Dec. 4, 2014, which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]      FIG. 1  depict an air-bearing surface (ABS) view of a conventional read transducer  10 . The conventional read transducer  10  includes shields  12  and  20 , sensor  14  and magnetic bias structures  16 . The read sensor  14  is typically a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor. The read sensor  14  includes an antiferromagnetic (AFM) layer, a pinned layer, a nonmagnetic spacer layer, and a free layer. Also shown is a capping layer. In addition, seed layer(s) may be used. The free layer has a magnetization sensitive to an external magnetic field. Thus, the free layer functions as a sensor layer for the magnetoresistive sensor  14 . The magnetic bias structures  16  may be hard bias structures or soft bias structures. These magnetic bias structures are used to magnetically bias the sensor layer of the sensor  14 . 
         [0003]    Although the conventional magnetic recording transducer  10  functions, there are drawbacks. In particular, the conventional magnetic recording transducer  10  may not function adequately at higher recording densities. Two-dimensional magnetic recording (TDMR) technology may enable significantly higher recording densities. In TDMR, multiple read sensors are used. These sensors are longitudinally distributed along the cross track direction but are aligned in the down track direction. The central sensor reads the data from a track of interest, while the outer sensors sense the data in adjacent tracks in order to account for noise. 
         [0004]    Although TDMR might be capable of higher recording densities, issues may be faced at skew. As a result, the transducer may not perform as desired for all skew angles. In addition, fabrication of the sensors may be challenging. Accordingly, what is needed is a system and method for improving the performance of a magnetic recording read transducer, particular for TDMR. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  depicts a conventional read transducer. 
           [0006]      FIG. 2  depicts an exemplary embodiment of a disk drive. 
           [0007]      FIGS. 3A and 3B  depict ABS-facing views of an exemplary embodiment of a portion of a magnetic recording read transducer including the device and the lapping guides. 
           [0008]      FIGS. 4A-4D  depict views of an exemplary embodiment of electrical connections made to the ELGs for a magnetic recording read transducer. 
           [0009]      FIG. 5  depicts a plan view of another exemplary embodiment of ELGs for a magnetic recording read transducer. 
           [0010]      FIG. 6  depicts a plan view of another exemplary embodiment of ELGs for a magnetic recording read transducer. 
           [0011]      FIG. 7  depicts an ABS-facing view of another exemplary embodiment of ELGs for a magnetic recording read transducer. 
           [0012]      FIGS. 8A-8B  depict ABS-facing and plan views of another exemplary embodiment of an ELG for a magnetic recording read transducer. 
           [0013]      FIG. 9  is a flow chart depicting an exemplary embodiment of a method for fabricating a magnetic recording read transducer. 
           [0014]      FIG. 10  is a flow chart depicting an exemplary embodiment of a method for fabricating a magnetic recording read transducer. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIGS. 2 and 3A-3B  depict side and ABS-facing views of a disk drive  100 . For clarity,  FIGS. 2, 3A and 3B  are not to scale. For simplicity not all portions of the disk drive  100  are shown. In addition, although the disk drive  100  is depicted in the context of particular components other and/or different components may be used. For example, circuitry used to drive and control various portions of the disk drive  100  is not shown. For simplicity, only single components are shown. However, multiples of one or more of the components and/or their sub-components might be used. Further, in some embodiments, the devices shown in  FIG. 3B  may be removed during fabrication and thus not present in the final disk drive  100 . However, in other embodiments, the devices shown in  FIG. 3B  may be present in the finished disk drive  100 . Thus,  FIG. 3B  may be considered to how the disk drive  100  during fabrication, while  FIG. 3A  may depict the disk drive during fabrication or after manufacturing is complete. 
         [0016]    The disk drive  100  includes media  101 , a slider  102 , a head  103  including a write transducer  104  and a read transducer  110 . The write transducer includes at least a write pole  106  and coil(s)  108  for energizing the pole  106 . Additional and/or different components may be included in the disk drive  100 . Although not shown, the slider  102 , and thus the transducers  104  and  110  are generally attached to a suspension (not shown). The transducers  104  and  110  are fabricated on the slider  102  and include an ABS proximate to the media  101  during use. Although both a write transducer  104  and a read transducer  110  are shown, in other embodiments, only a read transducer  110  may be present. 
         [0017]    The read transducer  110  includes multiple read sensors  112 ,  114  and  116 . The read sensors  112 ,  114  and  116  include sensor layers  113 ,  115  and  117 , respectively, that may be free layers in a magnetoresistive junction such as a giant magnetoresistive (GMR) sensor, a tunneling magnetoresistive (TMR) sensor. Thus, each sensor  112 ,  114  and  116  may include a pinning layer, a pinned layer, a nonmagnetic spacer layer and a free layer  113 ,  115 , and  117 , respectively. For simplicity, only the free layers  113 ,  115  and  117  are separately labeled in  FIG. 3A . The sensors  112 ,  114  and  116  may also include seed layer(s) (not shown) and capping layer(s) (not shown). The pinning layer is generally an AFM layer that is magnetically coupled to the pinned layer. In other embodiments, however, the pinning layer may be omitted or may use a different pinning mechanism. The free layers  113 ,  115  and  117  are each shown as a single layer, but may include multiple layers including but not limited to a synthetic antiferromagnetic (SAF) structure. The pinned layer may also be a simple layer or a multilayer. Although shown as extending the same distance from the ABS, the pinned layer may extend further than the corresponding free layer  113 ,  115 , and/or  117 , respectively. The nonmagnetic spacer layer may be a conductive layer, a tunneling barrier layer, or other analogous layer. Although depicted as a GMR or TMR sensor, in other embodiments, other structures and other sensing mechanisms may be used for the sensor. 
         [0018]    Although described as read sensors, if  FIG. 3A  is considered to depict the transducer  110  before completion, particularly before lapping, the sensors  112 ,  114  and  116  may be read sensor stacks. Read sensor stacks include the layers provided for the read sensors, but definition of the stacks may not be completed. For example, lapping of the transducer  110  may not have been performed. However, the track widths of the sensors would have been defined in the cross track direction. For simplicity, when referring to  FIG. 3A , items  112 ,  114  and  116  are generally termed sensors. 
         [0019]    The read sensors  112 ,  114  and  116  are separated by distances d 1  and d 2  in a down track direction. The down track direction is perpendicular to the cross track direction. The cross track direction and track width direction are the same. In the embodiment shown in  FIGS. 2-3B , the distance d 1  and d 2  between the sensors  112  and  114  and between the sensors  114  and  116 , respectively, are the same. However, in other embodiments, the distances between the sensors  112 ,  114  and  116  may not be the same. It is generally desirable to reduce the distance between the sensors  112 ,  114  and  116  in order to reduce the skew effect. The distances d 1  and d 2  may each be at least ten nanometers and not more than four hundred nanometers. The read sensors  112 ,  114  and  116  may have multiple widths, w 1 , w 2  and w 3 , respectively, in the track width, or cross-track, direction. However, in other embodiments, other widths are possible. The widths of the sensors  112 ,  114  and  116  may also be based on the track pitch. The track pitch is the distance from the center of one track to the center of the next track. Further, the widths may depend not only on the track pitch, but also on the distance between the sensors  112 ,  114  and  116 . 
         [0020]    The read sensors  112 ,  114  and  116  may also be displaced along the cross track direction. Therefore, the centers of each of the read sensors  112 ,  114  and  116  are not aligned along a vertical line that runs the down track direction. In the embodiment shown, none of the read sensors  112 ,  114  and  116  are aligned along a vertical line that runs in the down track direction. In other embodiments, some or all of the read sensors  112 ,  114  and  116  may be aligned. The read sensors  112 ,  114  and  116  may also partially overlap in the track width/cross track direction. However, in other embodiments, the read sensors  112 ,  114  and  116  may be aligned. 
         [0021]    Also shown are bias structures  122 ,  123  and  124  that magnetically bias the read sensors  112 ,  114  and  116 , respectively. The magnetic bias structure(s)  122 ,  123  and/or  124  may be soft bias structures fabricated with soft magnetic material(s). In other embodiments, the magnetic bias structure(s)  122 ,  123  and/or  124  may be hard magnetic bias structures. Other mechanisms for biasing the sensors  112 ,  114  and  116  might also be used. 
         [0022]    The read sensors are separated by shields  130  and  140 . The read sensors  112 ,  114  and  116  and shields  130  and  140  are surrounded by read shields  120  and  149 . Thus, as used herein, a shield may be considered to be an internal shield, which is interleaved with read sensors  112 ,  114  and  116  and between the outer, read shields. The outermost shields for the read transducer  110  are termed read shields. In the embodiment shown in  FIGS. 2-3B , three read sensors  112 ,  114  and  116  and two internal shields  130  and  140  are shown. However, in another embodiment, another number of read sensors  112 ,  114  and  116  and internal shields  130  and  140  may be present. The shields/read shields  120 ,  130 ,  140  and  149  generally include soft magnetic material. In some embodiments, one or more of the shields  120 ,  130 ,  140  and  149  may include ferromagnetic layers that are antiferromagnetically coupled. 
         [0023]    The shields  130  and  140  may be configured to not only magnetically shield the sensors  112 ,  114  and  116 , but also to provide electrical isolation. As a result, each shield  130  and  140  includes magnetic metallic layers separated by one or more insulating layers. Thus, the shield  130  includes conductive magnetic layers  132  and  136  that are separated by insulating layer  134 . Similarly, the shield  140  includes conductive magnetic layers  142  and  146  separated by insulating layer  144 . Thus, the shields  130  and  140  may magnetically shield and electrically isolate the sensors  112 ,  114  and  116 . 
         [0024]    Electronic lapping guides (ELGs)  150 ,  152  and  154  for the transducer  110  and disk drive  100  are shown in  FIG. 3B . The ELGs  150 ,  152  and  154  are used to control lapping of the transducer  110  and thus the stripe heights of the sensors  112 ,  114  and  116  (length in the stripe height direction). Signal(s) from the ELGs  150 ,  152  and  154  are used to determine when to terminate lapping of the sensors  112 ,  114  and  116 . 
         [0025]    The ELGs  150 ,  152  and  154  may be formed in the same layers as the sensors  112 ,  114  and  116 , respectively. For example, the ELGs  150 ,  152  and  154  may be at substantially the same layer as the free layers  113 ,  115  and  117 , respectively, and thus at substantially the same distance from the underlying substrate (not shown). In other words, the ELGs  150   152  and  154  may be coplanar with the sensors  112 ,  114  and  116 , respectively. In some such embodiments, the ELGs  150 ,  152  and  154  may be coplanar with the sensor layers  113 ,  115  and  117 , respectively. The distances between the ELGs  150  and  152  and the ELGs  152  and  154  may be substantially the same as the distances between the sensors/free layers  112 / 113  and  114 / 115  and the sensors/free layers  114 / 115  and  116 / 117 , respectively. In the embodiment shown in  FIGS. 2-3B , therefore, each ELG  150 ,  152  and  154  corresponds to a sensor  112 ,  114  and  116 , respectively. In other embodiments, the number of sensors and the number of ELGs may not be the same. For example, a single ELG, such as the ELG  152 , may be used for controlling lapping of all sensors  112 ,  114  and  116 . In other embodiments, two ELGs may be used for three sensors. Other configurations may also be possible. 
         [0026]    The ELGs  150 ,  152  and  154  may be configured in various manners. In some embodiments, each ELG  150 ,  152  and  154  may have its own contacts, allowing independent determinations of the resistances of the ELGs  150 ,  152  and  154 . In other embodiments, at least some of the ELGs  150 ,  152  and  154  may share contacts. For example, the ELGs  150 ,  152  and  154  may be coupled in series. In such an embodiment, various sub-configurations are possible. For example, only two leads, a first for one side of the ELG  150  and a second for the opposite side of the ELG  154  may be provided. In other embodiments, additional other contacts and leads may be used for separate determinations of the resistance(s) of one or more of the ELGs  150 ,  152  and  154 . In another embodiment, the ELGs  150 ,  152  and  154  may be connected in parallel. In such an embodiment one lead may connect to one side of the ELGs  150 ,  152  and  154 , while the other lead connects to the other side of the ELGs  150 ,  152  and  154 . Additional contacts and/or leads may be provided for the ELGs  150 ,  152  and/or  154  in order to isolate the ELG  150 ,  152  or  154  to independently determine its properties. 
         [0027]    Using the ELG(s)  150 ,  152  and/or  154 , lapping of the sensor stacks/sensors  112 ,  114  and  116  may be controlled. A signal from the ELG(s)  150 ,  152  and/or  154  may be used to determine when to terminate lapping of the transducer  110 . This signal may correspond to the resistance(s) of the ELG(s)  150 ,  152  and/or  154 . The resistances of the ELGs  150 ,  152  and  154  during lapping correspond to the stripe heights of the ELGs  150 ,  152  and/or  154  during lapping. As the resistances change, the stripe heights change. The ELG stripe heights correspond to stripe heights of the sensors  112 ,  114  and  116 . Thus, the desired sensor stripe heights may be determined, the corresponding ELG stripe heights determined, and the target resistances of the ELGs  150 ,  152  and  154  set based on these stripe heights. When the measured resistance(s) of the ELG(s)  150 ,  152  and/or  154  are the same as the target resistance(s), lapping may be terminated. 
         [0028]    Because one or more ELGs  150 ,  152  and/or  154  are used, fabrication of the transducer  110  may be improved. Use of a single ELG  150 ,  152  or  154  allows some control over lapping and, therefore, the stripe height of the sensors  112 ,  114  and  116 . If multiple ELGs  150 ,  152  and/or  154  are used, this control may be improved. For example, lapping may be terminated when a combination of the stripe heights of the sensors  112 ,  114  and  116  is, as determined by the ELG signals, optimized. For example, if a single ELG  152  were used, lapping may be optimized for only the sensor  114 . When some combination of the ELGs  150 ,  152  and  154  are used, a combination of the stripe heights of the sensors  112 ,  114  and  116  may be optimized. 
         [0029]    For example,  FIGS. 4A-4D  depict views of an exemplary embodiment of ELGs  150 ,  152  and  154  and their electrical connections for a magnetic recording read transducer  110 ′ and disk drive  100 ′. The read transducer  110 ′ and disk drive  100 ′ are analogous to the read transducer  110  and disk drive  100 , respectively. Consequently, similar components have analogous labels. Thus, the ELGs  150 ,  152  and  154  depicted in  FIG. 4A  are analogous to the ELGs  150 ,  152  and  154  depicted in  FIG. 3B  and used in connection with the sensors/sensor stacks  112 ,  114  and  116 . Referring to  FIGS. 3A and 4A-4D ,  FIG. 4A  depicts an ABS-facing view, while  FIGS. 4B, 4C and 4D  depict plan views of the ELGs  150 ,  152  and  154 , respectively. In the embodiment depicted in  FIGS. 4A-4D , the ELGs  150 ,  152  and  154  are connected in series. Three ELGs  150 ,  152  and  154  corresponding to the sensors/sensor stacks  112 ,  114  and  116 , respectively are shown. In other embodiments, another number of ELGs may be used. 
         [0030]    In addition to the ELGs  150 ,  152  and  154 , common ground connector  161 , common pad connector  167 , vias  160 ,  162 ,  164  and  166  and optional connectors  170  and  172  are shown. The ELG  152  is shown as having a mirror image configuration of pads, while the ELGs  150  and  154  have a partial mirror image. In other embodiments, other pad configurations may be used. The ELG  150  is thus connected to common ground connector  161  through via  160  and to ELG  152  through via  162 . The ELG  152  is connected to the ELG  154  and optional connector  172  through via  164 . The ELG  154  is connected to the common pad  167  through via  166 . The specific manner in which the optional connectors  170  and  172  are connected to the appropriate portions of the ELGs  150 ,  152  and  154 . 
         [0031]    Common pads  161  and  167  allow for a single resistance measurement of the series resistance of the ELGs  150 ,  152  and  154  to be made using two pads. Optional connectors  170  and  172  allow for the resistance of each of the ELGs  150 ,  152  and  154  to be independently measured. For example, the ELG  150  may have its resistance measured using connectors  161  and  167 . The ELG  152  may have its resistance independently measured using connectors  170  and  172 . The ELG  154  may have its resistance independently measured using connectors  172  and  167 . In other embodiments, one or both of the connectors  170  and  172  may be omitted. 
         [0032]    In some embodiments, a measure of the stripe height, target lapping resistance and, therefore, target signal from the ELGs  150 ,  152  and  154  may be determined as follows. The resistance of ELG  150 , R 150 , may be given by R 150 =[(W 150 /SH 150 )+K 150 ]Rs 150 , where W 150  is the track width (width in the cross track direction) of ELG  150 ; SH 150  is the stripe height of ELG  150  (length in the stripe height direction perpendicular to the ABS and perpendicular to the page in  FIG. 4A ), K 150  is the leads resistance constant for ELG  150  and Rs 150  is the sheet resistance of the ELG  150 . Similarly, the resistance of ELG  152 , R 152 , may be given by R 152 =[(W 152 /SH 152 )+K 152 ]R s152 , where W 152  is the track width of ELG  152 ; SH 152  is the stripe height of ELG  152 , K 152  is the leads resistance constant for ELG  152  and R s152  is the sheet resistance of the ELG  152 . The resistance of ELG  154 , R 154 , may be given by R 154 =[(W 154 /SH 154 )+K 154 ]R s154 , where W 154  is the track width of ELG  154 ; SH 154  is the stripe height of ELG  154 , K 154  is the leads resistance constant for ELG  154  and Rs 154  is the sheet resistance of the ELG  154 . The total, series resistance of the ELGs  150 ,  152  and  154  is R 150 +R 152 +R 154 . Thus, the total series resistance of the ELGs  150 ,  152  and  154  in  FIGS. 4A-4D  is: R total =[(W 150 /SH 150 )+K 150 ]R s150 +[(W 152 /SH 152 )+K 152 ]R s152 +[(W 154 /SH 154 )+K 154 ]R s154 . Desired stripe heights for the ELGs  150 ,  152  and  154  may be selected based on a balance of considerations for the corresponding stripe heights of the read sensors  112 ,  114  and  116 , respectively. Based on the desired stripe heights SH 150 , SH 152  and SH 154  for the ELGs  150 ,  152  and  154 , respectively, the target resistance of the combination shown in  FIGS. 4A-4D  may be determined using the equations above. In some embodiments, the parameters such as W x , SH x , K, and R sx , are measured. In other embodiments, the parameters may be set as discussed below. When the actual series resistance of the ELGs  150 ,  152  and  154  as connected reaches the target resistance, lapping may be terminated. 
         [0033]    The desired/target signal may be further calculated as follows. The windage is the offsets in the heights from the design target for the ELGs. The windage thus corresponds to the difference in stripe heights. If the ELG  150  is considered to have a base stripe height, then the stripe heights of ELGs  152  and  154  may be expressed as the stripe height of the ELG  150  and the windages for the ELGs  152  and  154 . For example,  FIGS. 5 and 6  depict exemplary embodiments of possible windages. In  FIG. 5 , the ELG  152 ′ and the ELG  154 ′ are both longer than the ELG  150 ′. Thus, the ELGs  152 ′ and  154 ′ have windages δ 1  and δ 2 , respectively, that are both positive. In  FIG. 6 , the ELG  152 ″ is shorter than the ELG  150 ″ while the ELG  154 ″ is longer. The ELGs  152 ″ and  154 ″ have windage δ 1 ′ that is negative and positive windage δ 2 ′, respectively. In other embodiments, other windages are possible. For example, mechanisms which may be used to account for windage are described in U.S. Pat. No. 8,151,441. 
         [0034]    Referring back to  FIGS. 4A-4D , the ELGs  152  and  154  are presumed to have windages δ 152  and δ 154 , respectively. Thus, the resistances become: R 150 =[(W 150 /SH 150 )+K 150 ]R s150 ; R 152 =[(W 152 /(SH 150 +δ 152 ))+K 152 ]R s152  and R 154 =[(W 154 /(SH 150 +δ 154 ))+K 154 ]R s154 . Further, the ELGs  150 ,  152  and  154  may be designed such that the leads resistance constants are substantially the same (K 150 =K 152 =K 154 =K). The track widths of the ELGs  150 ,  152  and  154  may also be set to be substantially the same in some embodiments, (W 150 =W 152 =W 154 =W). Although it may be unlikely that the sheet resistances of the ELGs  150 ,  152  and  154  are the same because they are deposited separately, this might be assumed (R s150 =R s152 =R s154 =R s ) for simplification. As a result, the total series resistance may be as approximated by R total =R s WK{(1/(KSH 150 )+1/W+1/(K(SH 150 +δ 152 ))+1/W+1/(K(SH 150 +δ 154 ))+1/W}. 
         [0035]    The sensitivity may be considered the change in resistance divided by the changes in stripe height (ΔR total /ΔSH). Given the above, the sensitivity for the configuration shown in  FIGS. 4A-4D  may be given by: R s WK{[1/(KSH 150 )] 2 +[1/(K(SH 150 +δ 152 ))] 2 +[1/(K(SH 150 +δ 154 ))] 2 }. In this embodiment, the sensitivity is known and R s , W and K are known or design constants. Thus, the desired stripe heights may be obtained. If a higher level of precision is desired, then the actual sheet resistances (R s150 , R s152  and R s154 ) and windages (δ 152  and δ 154 ) for the ELGs  150 ,  152  and  154  may be measured and used in determining the lapping rate and target resistance. For wafer level measurements prior to lapping, it may be assumed that δ 152  and δ 154  are much less than SH 150 . In such an embodiment, SH 150 =[R s W/(ΔR total /ΔSH)] 1/2  and SH 150 =3/[R total /(R s W)−3W]. These expressions for the stripe height of ELG  150  (or the other ELGs  152  and/or  154 ) may be used to estimate the upper bounds of the sensor stack stripe height and/or calibrate lapping. 
         [0036]    In some embodiments, the ELGs  150 ,  152  and  154  may have different track widths. In such embodiments, the differences in track widths is to be accounted for. For example, in some such embodiments, the track widths of one of the ELGs may be a multiple of the track width of the remaining ELGs (e.g. W 150 =W 152 =W 154 /2). In all embodiments, however, the relevant parameters may either be measured or designed such that the lapping can be controlled using the ELGs  150 ,  152  and  154  connected in series to give the desired stripe heights for the sensors  112 ,  114  and  116 , within acceptable limits. 
         [0037]    Using the ELGs  150 ,  152  and/or  154  and the signals discussed above, termination of lapping of the sensors  112 ,  114  and  116  may be controlled such that a balance between the sensor  112 ,  114  and  116  responses may be achieved. Stated differently, variations in the stripe heights of the sensors  112 ,  114  and  116  may be better compensated. Optimizing lapping of the sensors  112 ,  114  and  116  may improve yield and improve performance of the combination of sensors  112 ,  114  and  116 . If the series resistance, for example between connectors  161  and  167 , is used, this control may be achieved using only two contact pads. Thus, the configuration of pads used for a single read sensor need not be changed. In other embodiments, accuracy might be further improved by providing pads for each of the ELGs  150 ,  152  and  154 . Resistances, including sheet resistance, may also be measured for each of the ELGs  150 ,  152  and  154 . Windage may be determined based on the sheet resistances. Further, direct feedback for each of the sensors  112 ,  114  and  116  may be provided during processing using the corresponding ELG  150 ,  152  and  154 , respectively. Finally, subset(s) of the ELGs  150 ,  152  and  154  may also be used in fabrication of the disk drive. Thus, fabrication of the disk drive  100 ,  100 ′ and/or  100 ″ may be improved. 
         [0038]      FIG. 7  depicts an ABS-facing view of another exemplary embodiment of ELGs for a magnetic recording read transducer  110 ″ and disk drive  100 ″. The read transducer  110 ″ and disk drive  100 ″ are analogous to the read transducer  110  and disk drive  100 . Thus, analogous components have similar labels. Thus, the ELGs  150 ,  152  and  154  depicted in  FIG. 7  are analogous to the ELGs  150 ,  152  and  154  depicted in  FIG. 3B  and used in connection with the sensors/sensor stacks  112 ,  114  and  116 . Referring to  FIGS. 3A and 7 , an ABS-facing view is shown in  FIG. 7 . In the embodiment depicted in  FIG. 7 , the ELGs  150 ,  152  and  154  are connected in parallel. Three ELGs  150 ,  152  and  154  corresponding to the sensors/sensor stacks  112 ,  114  and  116 , respectively are shown. In other embodiments, another number of ELGs may be used. 
         [0039]    In addition to the ELGs  150 ,  152  and  154 , common ground connector  161 , common pad connector  167 , vias  160 ,  162 ,  163 ,  164 ,  165  and  166  are shown. The vias  160 ,  162 ,  164 ,  166  and connectors  161  and  167  are analogous to those shown in  FIG. 4A . The ELGs  150 ,  152  and  154  may each have a mirror image configuration of pads. In other embodiments, other pad configurations may be used. The ELG  150  is thus connected to common ground connector  161  through via  160  and to ELG  152  through vias  162  and  163 . The ELG  152  is connected to the ELG  154  and optional connector  172  through vias  164  and  165 . The ELG  154  is connected to the common pad  167  through via  166 . Although not shown, optional connectors for independently determining the resistances of the ELGs  150 ,  152  and/or  154  may be provided. Such connectors are analogous to the connectors  170  and  172  depicted in  FIG. 4A . Common pads  161  and  167  allow for a single resistance measurement of the parallel resistance of the ELGs  150 ,  152  and  154  to be made using two pads. 
         [0040]    In some embodiments, a measure of the stripe height, target lapping resistance and, therefore, target signal from the ELGs  150 ,  152  and  154  may be determined as follows. The resistances of ELGs  150 ,  152  and  154  (R 150 , R 152  and R 154 ) are described above. The total, parallel resistance of the ELGs  150 ,  152  and  154  is 1/(1/R 150 +1/R 152 +1/R 154 ). Thus, the total parallel resistance of the ELGs  150 ,  152  and  154  in  FIG. 7  is: R total,∥ =1/{[[(W 150 /SH 150 )+K 150 ]R s150 ] −1 +[[(W 152 /SH 152 )+K 152 ]R s152 ] −1 +[[(W 154 /SH 154 )+K 154 ]R s154 ] −1 } Desired stripe heights for the ELGs  150 ,  152  and  154  may be selected based on a balance of considerations for the corresponding stripe heights of the read sensors  112 ,  114  and  116 , respectively. Based on the desired stripe heights SH 150 , SH 152  and SH 154  for the ELGs  150 ,  152  and  154 , respectively, the target resistance of the combination shown in  FIG. 7  may be determined using the equations above. In some embodiments, the parameters such as W x , SH x , K x , and R sx , are measured. In other embodiments, the parameters may be set as discussed below. When the actual resistance of the ELGs  150 ,  152  and  154  as connected in parallel reaches the target resistance, lapping may be terminated. 
         [0041]    The desired/target signal may be further calculated using the windage described above. The ELGs  152  and  154  are presumed to have windages δ 152  and δ 154 , respectively, with respect to the ELG  150 . Thus, the total, parallel resistance becomes R total,∥ =1/{[[(W 150 /SH 150 )+K 150 ]Rs 150 ] −1 +[[(W 152 /(SH 150 +δ 152 ))+K 152 ]R s152 ] −1 +[[(W 154 /(SH 150 +δ 154 ))+K 154 ]Rs 154 ] −1 }. As discussed above with respect to the series embodiment, the ELGs  150 ,  152  and  154  may be designed such that the leads resistance constants are substantially the same and given by K. The track widths of the ELGs  150 ,  152  and  154  may also be set to be substantially the same in some embodiments, W. Although it is unlikely that the sheet resistances of the ELGs  150 ,  152  and  154  are the same, this might be assumed (R s150 =R s152 =R s154 =R s ) for simplification. As a result, the total parallel resistance may be approximately by R total,∥ =1/{[[(W/SH 150 )+K]R s ] −1 +[[(W/(SH 150 +δ 152 ))+K]R s ] −1 [[(W/(SH 150 +δ 154 ))+K]R s ] −1 }. The sensitivity, estimated upper bound for the stripe heights and other parameters may be calculated or measured in a manner analogous to that described above in the series case. Similarly, differences in track width may be accounted for. In all embodiments, however, the relevant parameters may either be measured or designed such that the lapping can be controlled using the ELGs  150 ,  152  and  154  connected in parallel to give the desired stripe heights for the sensors  112 ,  114  and  116 , within acceptable limits. 
         [0042]    Using the ELGs  150 ,  152  and/or  154  and the signals discussed above, termination of lapping of the sensors  112 ,  114  and  116  may be controlled such that a balance between the sensor  112 ,  114  and  116  responses may be achieved. Stated differently, variations in the stripe heights of the sensors  112 ,  114  and  116  may be better compensated. Optimizing lapping of the sensors  112 ,  114  and  116  may improve yield and improve performance of the combination of sensors  112 ,  114  and  116 . If the parallel resistance, for example between connectors  161  and  167 , is used, this control may be achieved using only two contact pads. Thus, the configuration of pads used for a single read sensor need not be changed. In other embodiments, accuracy might be further improved by providing pads for each of the ELGs  150 ,  152  and  154 . Resistances, including sheet resistance, may also be measured for each of the ELGs  150 ,  152  and  154 . Windage may be determined based on the sheet resistances. Further, direct feedback for each of the sensors  112 ,  114  and  116  may be provided during processing using the corresponding ELG  150 ,  152  and  154 , respectively. Subset(s) of the ELGs  150 ,  152  and  154  may also be used in fabrication of the disk drive. Thus, fabrication of the transducer  110  and/or  110 ′″ may be improved 
         [0043]      FIGS. 8A and 8B  depict an ABS-facing view and a plan view, respectively, of another exemplary embodiment of an ELG for a magnetic recording read transducer  110 ′ and disk drive  100 ′″. The read transducer  110 ′″ and disk drive  100 ′″ are analogous to the read transducer  110  and disk drive  100 . Thus, analogous components have similar labels. Thus, the ELG  152  depicted in  FIGS. 8A and 8B  is analogous to the ELG  152  depicted in  FIG. 3B  and used in connection with the sensors/sensor stacks  112 ,  114  and  116 . Although the ELG  152 , which corresponds to the center sensor/sensor stack  114  may be preferred if a single ELG is used, in other embodiments, the ELG  150  or  154  might be employed instead. 
         [0044]    In addition to the ELG  152 , ground connector  161 , pad connector  167  and vias  160  and  166  are shown. The vias  160  and  166  and connectors  161  and  167  are analogous to those shown in  FIG. 4A . Additional vias  162  and  164  may be coupled to optional connectors (not shown). The ELG  152  may each have a mirror image configuration of pads. In other embodiments, other pad configurations may be used. The ELG  150  is thus connected to common ground connector  161  through via  160  and to ELG  152  through vias  162  and  163 . The ELG  152  is connected to the ELG  154  and optional connector  172  through vias  164  and  165 . The ELG  154  is connected to the common pad  167  through via  166 . Pads  161  and  167  allow for a single resistance measurement of the ELG  152  to be made using two pads. 
         [0045]    In some embodiments, a measure of the stripe height, target lapping resistance and, therefore, target signal from the ELG  152  may be determined as follows. The resistance of ELG  152  is R 152 =[(W 152 /(SH 150 +δ 152 ))+K 152 ]+K s152 . The desired (or target) stripe height for the ELG  152  may be selected based on a balance of considerations for the corresponding stripe heights of the read sensors  112 ,  114  and  116 , respectively. For example, the desired stripe height of the ELG  152  may be based on the desired stripe height of the sensor  114 . The corresponding target resistance may be calculated using the equation above. In some embodiments, the parameters such as W 152 , SH 152 , K 152  and R s152  are measured. In other embodiments, the parameters may be set below. When the actual resistance of the ELG  152  reaches the target resistance, lapping may be terminated. 
         [0046]    Using the ELG  152  and the signals discussed above, termination of lapping of the sensors  112 ,  114  and  116  may be controlled. Because a single sensor is used, fabrication may be simplified and only two contact pads used. Electrical insulation of the ELG  152  may also be improved because no conductive ELGs, such as an ELG  150  or  154 , are close to the ELG  152 . 
         [0047]      FIG. 9  is an exemplary embodiment of a method  300  for providing a read transducer having multiple read sensors and using ELG(s) to control lapping. For simplicity, some steps may be omitted, interleaved, and/or combined. The method  300  is also described in the context of providing a single recording transducer  110 / 110 ′/ 110 ″ depicted in  FIGS. 2, 3A-3B, 4A-4D and 7 . However, the method  300  may be used to fabricate multiple devices on a wafer at substantially the same time. The method  300  may also be used to fabricate other transducers including but not limited to any combination of the transducers  110 ,  110 ′,  110 ″ and/or  110 ′″. The method  300  is also described in the context of particular layers. A particular layer may include multiple materials and/or multiple sub-layers. The method  300  also may start after formation of other portions of the magnetic recording transducer. 
         [0048]    The read sensor stacks are provided, via step  302 . Step  302  typically includes depositing the layers for each of the sensors, then defining the sensors in at least the track width direction. The stripe height away from the ABS may also be defined in step  302 . Portions of step  302  are generally interleaved with other steps. For example, the read sensor stack  112  may be formed, then a number of steps occur before formation of the read sensor stack  114 . Similarly, a number of steps occur between formation of the read sensor stack  114  and fabrication of the read sensor stack  116 . 
         [0049]    The ELG(s)  150 ,  152  and/or  154  are provided, via step  304 . In some embodiments, step  304  includes depositing and patterning the conductive material(s) for the ELG(s)  150 ,  152  and/or  154 . Portions of step  304  may be interleaved with portions of step  302  such that the ELG(s)  150 ,  152  and  154  are at level(s) corresponding to the sensor stacks  112 ,  114  and  116 , respectively. For example, the ELG  150  may be deposited and patterned at around the time that one or more of the layers of the sensor stack  112  is provided. Similarly, the ELG  152  may be deposited and patterned at around the time that one or more of the layers of the sensor stack  114  is provided. The ELG  154  may be deposited and patterned at around the time that one or more of the layers of the sensor stack  116  is provided. Thus, the ELG(s)  150 ,  152  and  154  are at substantially the same layer(s) in the device as the sensor stacks  112 ,  114  and  116 . Fabrication of the transducer  110 ,  110 ′ and/or  110 ″ continues until the slider is ready for lapping. 
         [0050]    Lapping is then performed until termination that is based upon the ELG signal(s), via step  306 . Step  306  may include determining a target resistance for one or more of the ELG(s)  150 ,  152  and  154  and/or a resistance of a combination of one or more of the ELG(s)  150 ,  152  and  154 . For example, a target for the series or parallel resistance described above may be determined. As is discussed above, this target resistance translates to stripe height(s) of the ELG(s)  150 ,  152  and/or  154  and to stripe heights of the sensors  112 ,  114  and  116 . When the signal from the ELG(s)  150 ,  152  and/or  154  reaches the target, lapping may be terminated. 
         [0051]    Using the method  300 , the transducer  110 ,  110 ′ and/or  110 ″ and disk drive  100 ,  100 ′ and/or  100 ″, respectively, may be accomplished. Because lapping is controlled using the signals from the ELG(s)  150 ,  152  and/or  154 , a better balancing of the stripe heights of the sensors  112 ,  114  and  116  may be achieved. Thus, yield for the method  300  may be improved and device performance enhanced. 
         [0052]      FIG. 10  is an exemplary embodiment of a method  310  for providing a read transducer having multiple read sensors and using an ELG to control lapping. For simplicity, some steps may be omitted, interleaved, and/or combined. The method  310  is also described in the context of providing a single recording transducer  110 ′″ depicted in  FIGS. 2, 3A-3B, and 8A-8B . However, the method  310  may be used to fabricate multiple transducers at substantially the same time. The method  310  may also be used to fabricate other transducers. The method  310  is also described in the context of particular layers. A particular layer may include multiple materials and/or multiple sub-layers. The method  310  also may start after formation of other portions of the magnetic recording transducer. 
         [0053]    The read sensor stacks are provided, via step  312 . Step  312  typically includes depositing the layers for each of the sensors, then defining the sensors in at least the track width direction. The stripe height away from the ABS may also be defined in step  312 . Portions of step  312  are generally interleaved with other steps. For example, the read sensor stack  112  may be formed, then a number of steps occur before formation of the read sensor stack  114 . Similarly, a number of steps occur between formation of the read sensor stack  114  and fabrication of the read sensor stack  116 . Step  312  is analogous to step  302  of the method  300 . 
         [0054]    The ELG  152  is provided, via step  314 . In some embodiments, step  314  includes depositing and patterning the conductive material(s) for the ELG  152 . Portions of step  314  may be interleaved with portions of step  312  such that the ELG  152  is at a location corresponding to the sensor stack  114 . For example, the ELG  152  may be deposited and patterned at around the time that one or more of the layers of the sensor stack  114  is provided. In other embodiments, the method  310  may form the ELG  150  or  154  depicted in  FIG. 3B  instead of the EGL  152 . Thus, the ELG  150  is at substantially the same layer(s) in the device as the sensor stacks  114   116 . Fabrication of the transducer  110 ′″ continues until the slider is ready for lapping. 
         [0055]    Lapping is then performed until termination that is based upon the ELG signal, via step  316 . Step  316  may include determining a target resistance for one or more of the ELG  152 . As is discussed above, this target resistance translates to stripe height of the ELG  152  and to stripe heights of the sensors  112 ,  114  and  116 . When the signal from the ELG(s)  150 ,  152  and/or  154  reaches the target, lapping may be terminated. 
         [0056]    Using the method  310 , the transducer  110 ′″ and disk drive  100 ′″, respectively, may be accomplished. Because of the signals from the ELG(s)  150 ,  152  and/or  154 , lapping may be controlled. Thus, yield for the method  310  may be improved and device performance enhanced. Thus, the benefits of the magnetic transducer(s)  110 ,  110 ′,  110 ″ and/or  110 ′″ may be achieved.