Abstract:
Aggressive (i.e. tight tolerance) stitching offers several advantages for magnetic write heads but at the cost of some losses during pole trimming. This problem has been overcome by replacing the alumina filler layer, that is used to protect the stitched pole during trimming, with a layer of electro-plated material. Because of the superior step coverage associated with the plating method of deposition, pole trimming can then proceed without the introduction of stresses to the stitched pole while it is being trimmed.

Description:
FIELD OF THE INVENTION 
   The invention relates to the general field of magnetic write heads with particular reference to pole trimming. 
   BACKGROUND OF THE INVENTION 
   The stitched writer has been the major workhorse of the data recording industry for the past several years due to its capability to provide narrow track width as well as for its tolerance control. On the other hand, the planar writer has proven to have better mechanical behavior due to its planar and non-recessed structure. Both writer designs can, however, be further improved by adopting aggressive stitching techniques to overcome the following problems. 
   A.  FIG. 1  illustrates a LDCR (low DC resistance) write head which is an example of a stitched writer design. Seen there are shielding layers  11  and  12  ( 11  being part of the reader head which is not shown), lower pole  13  (P 1 ) and stitched pole  16  (P 2 ). Also shown are coils  14 , insulation  17 , and upper pole  15  (P 3 ). Not shown, but necessarily present, is a write gap between  15  and  16 . The recession of P 3 ,  15 , relative to P 2 ,  16 , can impact over-writing, write saturation, and adjacent track erasure. With smaller track width, one can further enhance the writing capability and write saturation by reducing the recession and by ensuring balanced adjacent track erasure. However, the integrity of the alumina that is used to fill in the P 3  recession area (element  18 ) turns out to be a problem due to poor step coverage by the alumina. 
   B.  FIG. 2  illustrates an example of a planar writer. Seen there are shielding layers  11 ,  12 , and  13  ( 11  being part of the reader head which is not shown). Lower pole P 1  is made up of three parts,  24 ,  25 , and  26  while P 2  is upper pole  15 . Also shown are coils  14  and insulation  17 . As noted above, not shown, but necessarily present, is a write gap between  15  and  26 . For this type of design, ATE (adjacent track erasure) is a serious problem. Either the P 2  flank field or the P 1  field induces the ATE problem. A reduction of the P 2  flank field can be achieved by using a P 2  step design, as show, but to further reduce the P 1  field induced by the PPT (perpendicular pole trim) process, one needs to either recess a portion of P 1  or further extend P 1  to enhance the P 1 /P 2  coupling. However, having a recessed P 1  portion gives rise to the same alumina integrity problem discussed above, i.e. the poor alumina step coverage associated with element  28 . 
   The present invention discloses how to overcome the alumina integrity problem at the ABS (air bearing surface). The invention makes possible both aggressive P 3  stitching as well as aggressive P 1  recession without any of the problems associated with the alumina integrity. 
   A routine search of the prior art was performed with the following references of interest being found: 
   In U.S. Pat. No. 6,608,737, a Headway patent, Han et al. show a plated P 2  where Ps is stitched to P 2 . In U.S. Pat. No. 6,591,480, Chen et al. disclose forming both poles by plating where an upper pole yoke is plated over the upper pole piece. 
   SUMMARY OF THE INVENTION 
   It has been an object of at least one embodiment of the present invention to provide a process for pole trimming a stitched writer without causing any accessory damage thereto. 
   Another object of at least one embodiment of the present invention has been that said writer be a LDCR write head. 
   Still another object of at least one embodiment of the present invention has been that said writer be a planar writer. 
   A further object of at least one embodiment of the present invention has been to provide the structures that derive from said trimming processes. 
   These objects have been achieved by replacing the alumina filler layer, that is used to protect the stitched pole during trimming, with a layer of electro-plated material. Because of the superior edge coverage associated with the plating method of deposition, pole trimming can then proceed without the introduction of stresses to the stitched pole while it is being trimmed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a LDCR write head of the prior art. 
       FIG. 2  shows a planar write head of the prior art. 
       FIG. 3  illustrates the formation of the first of two photoresist molds for use in depositing the upper magnetic pole of a LDCR writer. 
       FIG. 4  shows the upper pole in place. 
       FIG. 5  shows how the mold shown in  FIG. 3  may be enlarged through a second exposure through a new mask. 
       FIG. 6  shows how a layer of non-magnetic material is electro-deposited within the mold of  FIG. 5 . 
       FIG. 7  shows the lower pole and coil well of a planar writer. 
       FIG. 8  shows how a layer of non-magnetic material is electro-deposited over the step that is part of the lower pole&#39;s upper surface. 
       FIG. 9  shows the structure of  FIG. 8  after planarization and formation of the upper pole. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   We will disclose the present invention through a description of improved processes for the manufacture of both LDCR and planar writers. These descriptions will also make clear the structures that are claimed. 
   1 st  Embodiment (LDCR Writer) 
   Referring now to  FIG. 3 , the process begins with the provision of lower magnetic pole  31  (for purposes of simplification, elements  12 ,  13  and  16  are shown as single element  31 ) in which we form a cavity which contains write coils  14 . The latter are coated with layer of insulation  17   a  and extend above the cavity by between about 3 and 5 microns. A seed layer (not shown but needed to initiate the plating) coats  17   a . As seen, the cavity that contains the coils is fully filled. 
   The structure is then coated with a layer of a positive photoresist which, by exposing through a first mask and then performing a first development, gets patterned into mold  32  which surrounds coils  14  but leaves areas  33  at the top surface of lower pole  31  exposed. These area are typically between about 2 and 4 microns wide. 
   In the next step, illustrated in  FIG. 4 , upper magnetic pole  41  is laid down inside mold  32  by means of electroplating. Then, in a key step illustrated in  FIG. 5 , mask  32  is exposed through a second mask and a second development is performed. The result is the transformation of mold  32  into mold  52 . The latter has a larger internal width than mold  32  so additional amount  53  of the top surface of  31  gets uncovered, typically by between about 1 and 2 microns. 
   As a key feature of the invention, this is followed by the deposition, through electroplating, of layer of non-magnetic material  61  on upper magnetic pole  41  as well as the exposed areas  53 . Our preferred materials for electroplated layer  61  have been any of NiPd, NiP, or NiCu, but any non-magnetic electro-platable material could have been used. 
   The process concludes with the removal of mold  52  followed by simultaneously polishing both magnetic poles until the ABS level is reached, making sure that some thickness of non-magnetic material  61  remains. Except for the presence of layer  61 , The final structure is as seen in  FIG. 1  except that element  18  is now (non-magnetic) metal rather than alumina. Because it was deposited through electroplating, the replacement for element  18  has good step coverage and polishing may be terminated arbitrarily close to upper pole  15  without stressing it. Typically the thickness (in a direction normal to the ABS) of the non-magnetic material that is left after pole trimming is between about 0.3 and 0.9 microns. 
   2 nd  Embodiment (Planar Writer) 
   Referring now to  FIG. 7 , the process begins with the provision of lower magnetic pole  71  (for purposes of simplification, elements  13 ,  24 ,  25 , and  26  are shown as single element  71 ) in which we form a cavity (extending downwards from the top surface for between about 2.5 and 35 microns) which contains write coils  14 . The latter are coated with layer of insulation  17   b  so that the cavity that contains the coils is just filled. Also shown in  FIG. 7  is a step just to the left of cavity edge  81 . The distance between the top and bottom surfaces of this step is typically between about 1.5 and 2.5 microns. 
   A photoresist mold (not shown) is then formed which covers all surfaces except an area that extends from edge  81  of the cavity to a distance that is sufficient to leave fully exposed the step described immediately above (which can be seen to be covered by element  28  in  FIG. 2 ). 
   Then, through electroplating, layer of non-magnetic material  88  is deposited to a thickness sufficient to cover all of the above-described step (just behind where the ABS, marked by broken line  82 , will eventually be), generally to a thickness between about 1.5 and 2.5 microns. Our preferred materials for electroplated layer  88  have been any of NiPd, NiP, or NiCu, but any non-magnetic electro-platable material could have been used. The mold used to contain the electroplate is then removed and the surface is planarized (using CMP) until layers  88 ,  71 , and  17   b  all have coplanar top surfaces. 
   Finally, as seen in  FIG. 9 , upper magnetic pole  91  is formed on the planarized surface and the upper and lower magnetic poles,  91  and  71 , as well as layer of non-magnetic material  88 , are simultaneously polished the plane marked by arrow  82  is reached so that a small thickness of layer  88  remains, thereby forming the air bearing surface without stressing either of the magnetic poles. 
   The final structure is as seen in  FIG. 2  except that element  28  is now (non-magnetic) metal rather than alumina. Because it was deposited through electroplating, the replacement for element  28  has good step coverage and polishing may be terminated arbitrarily close to pole  26  without stressing it. Typically the thickness (in a direction normal to the ABS) of the non-magnetic material that is left after pole trimming is between about 0.3 and 0.5 microns.