Abstract:
The method and system for providing a perpendicular magnetic recording (PMR) head are described. The PMR head includes a base layer, a nonmagnetic metal underlayer on the base layer, and a PMR pole on the nonmagnetic metal underlayer. The PMR pole has a top that is wider than its bottom. The base layer has a first hardness with respect to a pole trim. The nonmagnetic metal underlayer has a second hardness with respect to the pole trim. The second hardness is less than the first hardness.

Description:
BACKGROUND 
       FIGS. 1-2  depict a portion of conventional head including a conventional perpendicular magnetic recording (PMR) head  10 .  FIG. 1  depicts the conventional PMR head  10  as viewed from the air-bearing surface (ABS), while  FIG. 2  depicts the conventional PMR head  10  as viewed from the side. For clarity, the conventional PMR head  10  is not drawn to scale. The conventional PMR head  10  includes a conventional first pole  12 , pole/flux guide  13 , alumina insulating layer  14 , alumina base layer  16  that may be considered part of the alumina insulating layer  14 , a magnetic underlayer layer  17 , a conventional PMR pole  18 , insulating layer  20 , shield gap  26 , top shield  28 , and insulating layer  30 . Note that in certain other embodiments, the top shield  28  may also act as pole during writing using the conventional PMR head  10 . The magnetic underlayer  17  is used as a seed layer for the magnetic material(s) in the conventional PMR pole  18 . The conventional PMR pole  18  and the top shield  28  are surrounded by insulating layers  20  and  30 . The conventional PMR pole  18  has sidewalls  22  and  24 . The conventional PMR pole  18  also has a negative angle such that the top of the conventional PMR pole  18  is wider than the bottom of the conventional PMR pole  18 . Stated differently, the angle θ of the sidewalls is less than ninety degrees in the conventional PMR pole  18 . 
       FIG. 3  is a flow chart depicting a conventional method  50  for fabricating the conventional PMR head  10  using a damascene process. For simplicity, some steps are omitted. The conventional method  50  is described in the context of the conventional PMR head  10 . The conventional method  50  starts after formation of the first pole  12  and the alumina layer  14 . The alumina base layer  16  is formed, via step  52 . Thus, the insulating layers  14  and  16  may be part of a single, larger insulating layer. The magnetic underlayer  17  that is used as a seed layer is deposited, via step  54 . A photoresist mask is formed, via step  56 . The mask is typically a photoresist mask having a trench that is substantially the same shape as the conventional PMR pole  18 . The trench is refilled using the material for the conventional PMR pole  18 , via step  58 . The mask formed in step  56  is removed, via step  60 . The PMR pole  18  is trimmed, via step  62 . Typically, step  62  is performed using an ion beam etch that is carried out at an angle. In addition to thinning the PMR pole  18 , the trim performed in step  62  removes any remaining magnetic underlayer  17  outside of the PMR pole  18 . Fabrication of the PMR head  1  is then completed, via step  64 . Step  64  may include formation of the insulating layer  20 , lapping of the conventional PMR pole  18  to define the pole thickness, formation of the shield gap  25 , and other processes. 
     Although the conventional method  50  may be used to fabricate the conventional PMR pole  18 , there are drawbacks. For example,  FIG. 4  depicts the conventional PMR head  10  during the trimming performed in step  60 . At the end of the trimming in step  60 , only the portion  17  of the magnetic underlayer  17 ′ should remain. Thus, the conventional PMR head  10  is typically over etched. At least some of the alumna base layer  16  is, therefore, etched during the pole trim in step  60 . As can be seen in  FIG. 4 , atoms  25  removed from the alumina base layer  16 , magnetic underlayer  17 , and/or the PMR pole  18  may redeposit on the PMR pole  18 . Some of these atoms  25  are redeposited on the sidewalls  22  and  24  of the conventional PMR pole  18 . This redeposition is typically not a controlled process. Because of the redeposition on the PMR pole  18 , the etch rate of the PMR pole  18  varies with time and location. As redeposition continues, the etch rate of the PMR pole  18  dynamically changes. Consequently, the width of the conventional PMR pole  18  may vary in an unpredictable manner. As a result, there may be variations in the track width of the conventional PMR head  10 . In addition, the angle, θ, of the sidewalls  22  and  24  may vary. Such variations between conventional PMR poles  18  are undesirable. Furthermore, the surface roughness or profile of the sidewalls  22  and  24  may also vary due to redeposition. Consequently, geometry of the conventional PMR pole  18  may be compromised. As a result, the performance of the conventional PMR head  10  may be degraded. 
     Accordingly, what is needed is an improved method for fabricating a PMR head. 
     SUMMARY 
     The method and system for providing a PMR head are described. The PMR head includes a base layer, a nonmagnetic metal underlayer on the base layer, and a PMR pole on the nonmagnetic metal underlayer. The PMR pole has a top that is wider than its bottom. The base layer has a first hardness with respect to a pole trim. The nonmagnetic metal underlayer has a second hardness with respect to the pole trim. The second hardness is less than the first hardness. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is an ABS-view of a conventional PMR head. 
         FIG. 2  is a side view of a conventional PMR head. 
         FIG. 3  is a flow chart depicting a conventional method for fabricating a conventional PMR head. 
         FIG. 4  is a diagram of a conventional PMR head during fabrication. 
         FIG. 5  is an exemplary embodiment of a PMR head, as viewed from the ABS 
         FIG. 6  is an exemplary embodiment of a PMR head, as viewed from the side. 
         FIG. 7  is another exemplary embodiment of a PMR head, as viewed from the ABS 
         FIG. 8  is a flow chart depicting an exemplary embodiment of a method for forming a PMR head. 
         FIGS. 9-12  are diagrams of an exemplary embodiment of a PMR head during fabrication. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 5-6  depict an exemplary embodiment of a PMR head  100 .  FIG. 5  is an ABS view of the PMR head  100 , while  FIG. 6  is a side view of the PMR head  100 . In addition, for clarity, the PMR head  100  is not drawn to scale. The PMR head  100  is preferably part of a merged head that also includes a read head (not shown) and resides on a slider (not shown). 
     The PMR head  100  includes a first pole  102 , pole/flux guide  103 , insulator  104 , base layer  106 , nonmagnetic underlayer  108 , PMR pole  110 , insulating layer  112 , shield gap  118 , top shield  120 , and insulator  122  behind the top shield  120 . The PMR pole  110  and the top shield  120  are surrounded by insulating layers  118  and  122 . Note that in certain other embodiments, the top shield  120  may also act as pole during writing using the PMR head  100 . In addition, although described in the context of single layers or structures, such as the PMR pole  110  or base layer  106 , these structures may include multilayers. 
     The PMR pole  110  has sidewalls  112  and  114  and is preferably trapezoidal in shape. Thus, the PMR pole  110  also has a negative angle such that the top of the PMR pole  110  is wider than the bottom of the PMR pole  110 . Stated differently, the angle θ of the sidewalls is less than ninety degrees in the PMR pole  110 . In a preferred embodiment, the angle θ is at least seventy-five degrees and less than ninety degrees. 
     The base layer  106  is insulating and preferably composed of aluminum oxide. The base layer  106  may, therefore, be considered part of the insulator  104 . In addition, the base layer  106  has a particular hardness with respect to a pole trim that may be used in forming the PMR pole  110 . Stated differently, a pole trim performed for the PMR pole  110  etches the base layer  106  at a particular rate related to the hardness of the base layer  106 . 
     The nonmagnetic underlayer  108  is preferably metallic and resides on the base layer  104 . In addition, the nonmagnetic underlayer  108  functions as a seed layer for the PMR pole  110 . For example, the nonmagnetic underlayer  108  may include materials such as one or more of Ru, Ta, NiNb, Ti, and NiCr. In one embodiment, the nonmagnetic underlayer  108  is composed of NiNb. The nonmagnetic underlayer  108  may be sputtered or plated. The nonmagnetic underlayer  108  also a hardness with respect to the pole trim of the PMR pole  110 . This hardness of the nonmagnetic underlayer  108  is less than the hardness of the base layer  106 . Consequently, the nonmagnetic underlayer  108  may be more rapidly removed by a pole trim than the base layer  106 . In one embodiment, the nonmagnetic underlayer  108  has a hardness with respect to the pole trim that is less than the hardness of the base layer  106  but greater than the hardness of the materials used for the PMR pole  110 . In another embodiment, the hardness of the nonmagnetic underlayer  108  is approximately the same as or even less than the hardness of the PMR pole  110 . Because the nonmagnetic underlayer  108  is, by definition, not magnetic, not all of the nonmagnetic underlayer  108  not covered by the PMR pole  110  must be removed. Thus, as shown in  FIG. 5 , the nonmagnetic underlayer  108  may have a footing that extends beyond the base of the PMR pole  110 . Stated differently, in the PMR head  100 , the width of the nonmagnetic underlayer  108  is greater than the width of the base of the PMR pole  110 . 
     Use of the nonmagnetic underlayer  108  may improve performance of the PMR head  100 . Because all exposed portions the nonmagnetic underlayer  108  need not be removed during the pole trim, less of the insulating underlayer  108  is exposed during the pole trim. Thus, redeposition of the base layer  106  may be reduced. In addition, because the hardness of the nonmagnetic underlayer  108  is less than base layer  106 , and preferably closer to the hardness of the PMR pole  110 , redeposition may be reduced. Furthermore, less of the material used for the PMR pole  110  may be consumed during the trim process. Consequently, better control of the geometry of the PMR pole  110 , the track width, and the roughness of the sidewalls  112  and  114  may be achieved. In addition, use of a nonmagnetic layer  108  between the pole/flux guide  103  and the PMR (write) pole  110  may reduce domain lockup. Domain lockup is due to a remanent field in a PMR head and may result in the PMR head inadvertently erasing data in the PMR media even though no current energizes the PMR head. Use of the nonmagnetic layer  108  between the pole/flux guide  103  and the PMR pole  110  may improve the ability of the PMR pole  110  to demagnetize and thus may reduce undesirable domain lockup. Thus, performance of the PMR head  100  may be enhanced. 
       FIG. 7  is another exemplary embodiment of a PMR head  100 ′, as viewed from the ABS. The PMR head  100 ′ is analogous to the PMR head  100  and thus includes a first pole  102 ′, insulator  104 ′, base layer  106 ′, nonmagnetic underlayer  108 ′, PMR pole  110 ′, insulating layer  112 ′, shield gap  118 ′, top shield  120 ′, and insulator  122 ′ behind the top shield  120 ′. 
     Because the nonmagnetic underlayer  108 ′ is analogous to the nonmagnetic underlayer  108 , the nonmagnetic underlayer  108  has similar properties. For example, the nonmagnetic underlayer  108 ′ is preferably metallic, resides on the base layer  106 ′, acts as a seed layer for the PMR pole  110 ′ and has a hardness with respect to a trim of the PMR pole  110  that is less than the hardness of the base layer  106 ′. Consequently, the nonmagnetic underlayer  108 ′ may be more rapidly removed by the pole trim than the base layer  106 ′. In one embodiment, the nonmagnetic underlayer  108 ′ has a hardness with respect to the pole trim that is less than the hardness of the base layer  106 ′ but greater than the hardness of the materials used for the PMR pole  110 ′. In another embodiment, the hardness of the nonmagnetic underlayer  108 ′ is approximately the same as or even less than the hardness of the PMR pole  110 . For example, the nonmagnetic underlayer  108 ′ may include materials such as one or more of Ru, Ta, NiNb, Ti, and NiCr and may be sputtered or plated. 
     A portion of the nonmagnetic underlayer  108 ′ may remain outside of the PMR pole  110 ′ substantially without adversely affecting performance of the PMR head  100 ′. However, in the PMR head  100 ′, this portion of the nonmagnetic underlayer  108 ′ has been removed, preferably during a pole trim step. Consequently, the only remaining nonmagnetic underlayer  108 ′ is under the base of the PMR pole  110 ′. In the PMR head  100 ′, therefore, the width of the nonmagnetic underlayer  108 ′ is approximately the same as the width of the base of the PMR pole  110 ′. 
     Use of the nonmagnetic underlayer  108 ′ may improve performance of the PMR head  100 ′. Because the hardness of the nonmagnetic underlayer  108 ′ is less than the hardness of the base layer  106 ′, and preferably closer to the hardness of the PMR pole  110 , redeposition may be reduced. This may occur even though the portion of the nonmagnetic underlayer  108 ′ exposed by the PMR pole  110 ′ is removed. Consequently, better control of the geometry of the PMR pole  110 ′, the track width, and the roughness of the sidewalls  112 ′ and  114 ′ may be achieved. In addition, use of a nonmagnetic layer  108 ′ between the pole/flux guide (not shown in  FIG. 7 ) and the PMR (write) pole  110 ′ may reduce domain lockup. Thus, performance of the PMR head  100 ′ may be enhanced. 
       FIG. 8  is a flow chart depicting an exemplary embodiment of a method  200  for forming a PMR head.  FIGS. 9-12  are diagrams of an exemplary embodiment of the PMR head  100  during fabrication, as viewed from the ABS. For simplicity, some steps are omitted or combined into a single step. The method  200  is described, therefore, in the context of the PMR head  100 . The method  200  starts after formation of the first pole  102  and the insulator  104 . The insulating base layer  106  is formed, via step  202 . Thus, the insulating layers  104  and  106  may be part of a single, larger insulating base layer. The nonmagnetic underlayer  108  is deposited, via step  204 . In some embodiments, one or more layers of the nonmagnetic underlayer may be plated or sputtered. Step  204  may thus include depositing one or more of Ru, Ta, NiNb, Ti, and NiCr.  FIG. 9  depicts the PMR head  100  after step  204  is performed. Thus, the first pole  102 , insulator  104 , base layer  106 , and nonmagnetic underlayer  108 ″ are shown. 
     A mask for the PMR pole  110  is formed, via step  206 . The mask is typically a photoresist mask having a trench that is substantially the same shape as the PMR pole  18 . In a preferred embodiment, the mask is a photoresist mask.  FIG. 10  depicts the PMR head  100  after step  206  is completed. Consequently, the resist mask  150  having a trench  152  therein is shown. 
     The trench  152  is refilled using the material for the PMR pole  110 , via step  208 . Generally, the material for the PMR pole  110  is plated in step  208 .  FIG. 11  depicts the PMR head  100  after the material  110 ″ for the PMR pole  110  is deposited. In some embodiments, the thickness of material  110 ″ deposited may be greater than the final height, h, of the PMR pole  110 . 
     The mask  150  formed in step  206  is removed, via step  210 . After removal of the mask  150 , the PMR pole  18  is trimmed, via step  212 .  FIG. 12  depicts the PMR head  100  during step  212 . Step  212  is preferably performed using an ion beam etch that is carried out at an angle. In one embodiment, the angle, φ, for the ion mill is at least forty degrees from normal to the surface. In a preferred embodiment, the angle, φ, for the ion mill is at least fifty degrees and not more than seventy degrees from normal to the surface. In addition to thinning the PMR pole  110 , the trim performed in step  212  removes at least a portion of the nonmagnetic underlayer  108 ″ outside of the PMR pole  110 . Because the underlayer  108  is nonmagnetic, not all of the exposed underlayer  108 ″ is removed. Consequently,  FIG. 12  depicts the underlayer  108 , which extends beyond the base of the PMR pole  110 . In another embodiment, more of the nonmagnetic underlayer  108  may be removed. In such an embodiment, the remaining portion nonmagnetic underlayer  108 ″ may only be at the base of the PMR pole  110 . Fabrication of the PMR head  100  is then completed, via step  214 . Step  214  may include formation of the insulating layer  116 , lapping of the conventional PMR pole  18  to define the pole thickness, formation of the shield gap  118 , formation of top shield  120 , formation of insulator  122 , and other processes. Thus, the PMR head  100  depicted in  FIGS. 5-6  or the PMR head  100 ′ depicted in  FIG. 7  may be provided. 
     Thus, the method  200  may provide the PMR heads  100  and  100 ′. Because of the use of the nonmagnetic underlayer  108 / 108 ′/ 108 ″, redeposition, particularly of the base layer  106 / 106 ′ may be reduced. Furthermore, less of the material used for the PMR pole  110  may be consumed during the trim process. Consequently, less pole material  110 ″ may be deposited and the thickness of the mask  150  reduced. Consequently, better control of the geometry of the PMR pole  110 / 110 ′, the track width, and the roughness of the sidewalls  112 / 112 ′ and  114 / 114 ′ may be achieved. Moreover, the materials used for the nonmagnetic underlayer  108 / 108 ′/ 108 ″ may be less subject to corrosion than a conventional magnetic underlayer  17 . In addition, use of a nonmagnetic layer  108 / 108 ′ between the pole/flux guide  103  and the PMR (write) pole  110 / 110 ′ may reduce domain lockup. Thus, performance of the PMR head  100 / 100 ′ may be enhanced. Because materials such as Ru, Ta, NiNb, Ti, and NiCr are used for the layer  108 / 108 ′/ 108 ″, these benefits may be achieved without substantially altering the PMR head  100 / 100 ′ structure or fabrication process  200 .