Abstract:
For high track density recording, tighter reader and writer track width control are essential. This has been achieved by using the write gap layer as the plating seed on which the upper pole was electro-formed so that the width of the GMR pedestal serves to define the device&#39;s write track width.

Description:
[0001]     This is a divisional application of U.S. patent application Ser. No. 10/886,888, filed on Jul. 8, 2004, which is herein incorporated by reference in its entirety, and assigned to a common assignee. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to the general field of magnetic write heads with particular reference to an improved top pole piece.  
       BACKGROUND OF THE INVENTION  
       [0003]     For high track density recording, tighter reader and writer track width control is the key ingredient for obtaining high yield. How to continue improving the writer track width by using a pole trim process together with a narrow pole width is a challenging task. The basic principle to having tighter pole width control is to have a thinner pole resist process so that photo CD (critical dimension) control can be further improved. Reducing the amount of material consumed during the pole trim process, without impacting performance, is the key factor associated with using a thinner pole resist.  
         [0004]     The magnetic track width delta between reader and writer must be significantly reduced in high track density recording. Therefore, it becomes necessary to have better within-wafer reader and writer uniformity in order to meet performance requirements and provide a better yield. However, a pole trim process is required if one is to have a well defined track profile that facilitates the writing operation.  
         [0005]     On the other hand, said pole trim process introduces new problems such as track width uniformity control which needs to be improved. To achieve this, one must either remove less material during trimming or an improved trimming method must be substituted. The present invention discloses a novel process that allows less material to be removed during trimming while continuing to maintain the same performance level as the standard pole trim process  
         [0006]     There have been several proposals to utilize a plated S 2  (writer lower shield), a plated write gap, and a plated P 2  (top pole) in a single photo process thereby minimizing the extent of pole trim consumption. However, with this scheme the throat height definition is rather poor so this type of design creates magnetic flux leakage between pole and shield. So poor overwrite is a consequence of this type of design.  
         [0007]     Referring now to  FIG. 1 , the structure associated with our earlier process is illustrated. Seen there are upper and lower magnetic shields  13  and  15  respectively. Sandwiched between these shields is reader assembly  14 . High magnetic moment seed layer  21  lies atop layer  13  with non-magnetic write gap layer  51  being on it. Covering layer  51  is P 2  seed layer  31  on which P 2  pole  52  is formed through electroplating inside a mold (not shown).  
         [0008]     In  FIG. 2  we illustrate the end product of the pole trimming process during which part of P 2  is etched away together with the exposed portions of layers  21 ,  51 , and  31 . During this trim process, portions of the wafer surface away from the immediate vicinity of P 2 , such as test sites, will need to protected. Since the resist gets consumed at least as rapidly as the pole material, its thickness must exceed the amount of P 2  removed during trimming. Resist thicknesses of 2-3 microns must therefore be used.  
         [0009]     A routine search of the prior art was performed with the following references of interest being found:  
         [0010]     U.S. Pat. No. 6,469,868 (Yanamoto et al) teaches that a seed layer may be made of a nonmagnetic and a conductive material. U.S. Pat. No. 6,636,460 (Akiyama et al) discloses a Ni or NiFe sputtering film as a plating seed layer. U.S. Pat. No. 5,559,654 (Das) teaches plating on a previously sputtered seed layer.  
       SUMMARY OF THE INVENTION  
       [0011]     It has been an object of at least one embodiment of the present invention to reduce the amount of pole material consumed during pole trimming.  
         [0012]     Another object of at least one embodiment of the present invention has been to facilitate use of thinner photoresist during formation of the top pole.  
         [0013]     A further object of at least one embodiment of the present invention has been to achieve more precise control of the write gap thickness.  
         [0014]     A still further object of at least one embodiment of the present invention has been to eliminate re-deposition of pole material during the pole trim process.  
         [0015]     These objects have been achieved by using the write gap layer as the plating seed on which the upper pole is electro-formed. This allows the write gap layer to be deposited through a precisely controllable process such as sputtering. Since less material needs to be removed during pole trimming, a thinner layer of photoresist may be used. This, in turn, makes possible a lower CD for the structure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  shows, for our earlier process, the series of layers on which the upper magnetic pole is laid down.  
         [0017]      FIG. 2  shows the structure of  FIG. 1  at the conclusion of pole trimming.  
         [0018]      FIG. 3  illustrates how, in the present invention, a relatively small amount of material is laid down prior to pole trimming.  
         [0019]      FIG. 4  shows the structure of  FIG. 3  at the conclusion of pole trimming. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     We will disclose the present invention through a description of the process used for its manufacture. This description will also serve to make clear the structure of the present invention.  
         [0021]     Referring now to  FIG. 3 , the process begins with the provision of lower magnetic shield layer  15  and forming magnetic read head  14  above it. This is followed by the deposition of upper magnetic shield layer  13 , as shown, onto which is deposited high magnetic moment seed layer  21 . The lower magnetic shield has a thickness between about 1 and 3 microns, the upper magnetic shield has a thickness between about 4 and 7 microns, and they are separated by between about 400 and 1,000 Angstroms.  
         [0022]     High magnetic moment seed layer  21  is selected from the group consisting of CoFe and CoFeN and has a magnetic moment of at least 24 kilogauss. It is deposited to a thickness between about 1,000 and 4,000 Angstroms.  
         [0023]     Now follows a key feature of the invention namely the deposition, through sputtering, of non-magnetic write gap layer  51  onto high magnetic moment seed layer  21 . Once sputtering is chosen as the deposition means for the write gap layer it becomes possible to control its thickness very precisely (typically to within 50 Angstroms). The write gap layer material is any one of Ru, Rh, or NiCr and it is deposited to a thickness between about 700 and 1,200 Angstroms.  
         [0024]     With layer  51  in place, pedestal shaped upper write pole  52  is formed, most commonly through electroplating inside a suitable photoresist mold (not shown). It is important to note that layer  51  acts as an effective seed for this electroplating process. The upper write pole is any one of CoFe or CoNiFe. Its initial height is between about 2.5 and 3.5 microns.  
         [0025]     Referring now to  FIG. 4 , upper write pole  52  is used as a self aligning mask during an etching process wherein a portion of the write pole, as well as all areas of the structure that are not protected by photoresist (or by pole  52 ), are removed down to the level of layer  13 . As a consequence, the width of write gap layer  51  becomes equal to that of upper write pole  52 , said width now defining the write track width of the final writer (typically between about 0.1 and 0.2 microns). Additionally, the height of the upper write pole will have been reduced to between about 1 and 1.5 microns. For the etching process we have preferred using ion beam etching (IBE), low angle IBE to control trim depth followed by high angle IBE for etching to the final track width, but the invention is not limited to any particular etch process.  
         [0026]     Because the process of the invention limits the material that needs to be removed during the etching process to layers  21  and  51 , a lesser amount of pedestal  52  will be removed relative to earlier methods. Also, since a significant amount of photoresist is consumed during this etch process, the reduced etching time associated with the present invention allows a thinner layer of photoresist to be used. Typically, the photoresist layer will be between about 3.5 and 4 microns thick when etching starts and will be fully consumes when it is terminated. Use of this thinner-than-usual photoresist layer enables the associated photolithographic processes to be more precise so that the CD (critical dimension) of the structure is reduced to about 0.25 microns.  
         [0027]     Another important advantage of the reduced pole trim etch time is that the amount of redeposition during etching is reduced so that better control of pedestal width variations is achieved. Said redeposition occurs because material sputtered from vertical surfaces during the high angle IBE may land on nearby horizontal surfaces and vice versa.  
         [0028]     We conclude by noting that the present invention, as disclosed above, offers the following advantages: 
    1. Less P 2  consumption required during pole trimming due to less material between P 2  and the lower shield.     2. Thinner P 2  resist can be used and tighter control, both within a single wafer and from wafer to wafer can be expected. A thinner resist allows greater photo-processing latitude (depth of focus, for example) which in turn leads to better P 2  CD (critical dimension) control.     3. Heat dissipation by the writer is improved by replacing alumina with nonmagnetic metal materials, leading to less pole tip protrusion.     4. Better writer track width control.     5. A simplified writer process.