Abstract:
A magnetic pole suitable for perpendicular magnetic recording is described. This write pole is symmetrically located relative to its side shields and has at least three additional surfaces that are disposed to lie in planes that are normal to the substrate&#39;s top surface.

Description:
[0001]    This is a divisional application of U.S. patent application Ser. No. 11/728,910 filed on Mar. 27, 2007, 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 writing data into magnetic memory devices with particular reference to perpendicular write poles and their spatial relationship to their surrounding shields. 
       BACKGROUND OF THE INVENTION 
       [0003]    In order to be able to achieve the highest possible track density when using PMR (perpendicular magnetic recording), it is necessary to include side shields that reduce fringe effects and minimize side erasure.  FIG. 1  is a plan view of the structure in question. Seen there are main body (yoke)  11  in which the write field will be induced by the activation of the field coils (not shown), side shields  12 , and perpendicular write pole  13 . Line  14  shows where the ABS (air bearing surface) will eventually be located, following the removal (by grinding and polishing) of the material below it. 
         [0004]    It is important that the write pole be symmetrically located within the space between the side shields. If it is too close to one side or the other, one or more of the following problems may arise: 
         [0005]    1) a reduction in overall process yield due to occasional shorting between the shield and the write pole 
         [0006]    2) fringe effects at the pole edge farthest from shield 
         [0007]    3) uneven side erasure. 
         [0008]    A number of proposals have been put forward that use subtractive methods (such as RIE, IBE etc.) to etch an opening in a magnetic shield layer followed by standard ALD (atomic layer deposition), electroplating, and CMP methods to form the write pole inside said opening. However, in none of these approaches is the positioning of the write pole structure, between the side and trailing shields, accomplished through self-alignment, making the possibility of the occurrence of one or more of the problems listed above that much more likely. 
         [0009]    These problems have been overcome through the development of the self-aligning method that we disclose below. 
         [0010]    A routine search of the prior art was performed with the following references of interest being found: 
         [0011]    U.S. Patent Applications 2006/0174474 (Le) and 2006/0044682 (Le et al) teach forming self-aligned wrap-around side and trailing edge shields. In U.S. Patent Application 2006/0002019, Guthrie et al. show Rh as a CMP stop layer in forming a self-aligned trailing shield. U.S. Patent Application 2005/0259355 (Gao et al) teaches self-aligned formation of trailing shields using Rh as a stop layer. 
         [0012]    In U.S. Pat. No. 7,002,775, Hsu et al. disclose side shields and trailing shields, preferably made of the same material. The method of formation is not disclosed. U.S. Pat. No. 7,070,698 (Le) shows side shields and a trailing shield formed in separate steps. 
         [0013]    U.S. Pat. No. 7,068,453 (Terris et al.) describes side shields and trailing shield around the write pole while, in U.S. Pat. No. 7,031,121, Khera et al. show read element shields and a trailing shield. U.S. Patent Application 2005/0237665 (Guan et al.) shows a leading shield, trailing shield, and two side shields to overcome side fringing. No fabrication details are given. 
       SUMMARY OF THE INVENTION 
       [0014]    It has been an object of at least one embodiment of the present invention to provide a perpendicular magnetic recording device that includes a write pole that is always symmetrically positioned with respect to its surrounding magnetic side shield. 
         [0015]    Another object of at least one embodiment of the present invention has been to provide a process for forming said device. 
         [0016]    Still another object of at least one embodiment of the present invention has been that said process not require an optical alignment step for achieving said symmetrical positioning attribute of the structure. 
         [0017]    A further object of at least one embodiment of the present invention has been to eliminate said optical alignment step by enabling the write pole to be self-aligned relative to the side shield. 
         [0018]    These objects have been achieved by employing a trench (etched into a dielectric layer) as a mold for the formation of the write pole, after first lining the trench with a layer of ruthenium (or other suitable non-magnetic material) whose thickness is uniform and carefully controlled. Once the write pole has been formed, the dielectric layer is removed from its immediate vicinity and the top surface of the write pole is also coated with a layer of non-magnetic material whose thickness is precisely controlled, following which a second layer of soft magnetic material is deposited over the write pole. 
         [0019]    The location of the write pole relative to the shield is thus determined through control of the thicknesses of the two layers of non-magnetic material, no optical alignment step being involved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  illustrates the end product of the process of the present invention, including perpendicular write pole  13  that is guaranteed to be symmetrically disposed between side shields  12 . 
           [0021]      FIG. 2  shows the starting point for the process of the invention—a trench etched into a layer of insulation on a substrate. 
           [0022]      FIGS. 3-4  illustrate how the trench is just filled with material for the pole after the trench has been lined with a layer of non-magnetic material. 
           [0023]      FIGS. 5-7  are, respectively, an ABS view, a side view, and a plan view of the structure of the invention after the non-magnetic Ru has been removed by ion beam etch in the vicinity of the write pole and the step main pole is formed. 
           [0024]      FIGS. 8-9  are an ABS view and a plan view of the invention after the non-magnetic Ru was removed by ion beam etch and alumina was removed by wet etch. The trench was formed in the vicinity of the write pole, thereby exposing the substrate. 
           [0025]      FIGS. 10-11  are, respectively, an ABS view and a side view after deposition of a second layer of non-magnetic writer gap material, such as Ru. 
           [0026]      FIG. 12  is an ABS view following the deposition of a second soft magnetic layer. 
           [0027]      FIGS. 13-14  are, respectively, an ABS view and a side view after CMP has been used to planarize the second soft magnetic layer until its top surface is coplanar with the top surface portion of the non-magnetic write gap that is exposed first. 
           [0028]      FIGS. 15   a - 15   e  illustrate the sequence of steps used for the completion of the process. 
           [0029]      FIG. 16-18  are, respectively, an ABS view, a side view, and a plan view after deposition of a second layer of soft magnetic material that will serve as a trailing shield for the structure. 
           [0030]      FIG. 19  is a 3-D (isometric) view of the completed invention, including a cut away corner to further clarify the relationship between the various layers. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    Referring now to  FIG. 2 , and viewing the structure shown in  FIG. 1  as it would appear at the future ABS, the process of the present invention begins with the deposition, onto substrate  21 , of insulating layer  22  (typically alumina or silica) into which is etched trench  23 , using RIE, IBE, or similar process. 
         [0032]    Next, as shown in  FIG. 3 , layer  31  of ruthenium is deposited (to a precision level of ±5%) to fully cover the inside of trench  23  as well as the top surface of layer  22 . The preferred method for depositing layer  31  is ALD but other methods such as CVD and PVD could also have been used. Continuing our reference to  FIG. 3 , layer  32 , of soft magnetic material suitable for use as a magnetic pole for writing data (e.g. FeNi or CoFeNi), is then deposited onto layer  31 , to a thickness of between about 0.5 and 1 microns. This is accomplished by first depositing a conductive seed layer and then electro-plating thereon the required thickness of soft magnetic material. 
         [0033]    Moving on to  FIG. 4 , illustrated there is the end result of using CMP to remove all of layer  32  except portion  432  that just fills trench  23  (which at this point also includes layer  31  acting as a trench wall liner). During this step, ruthenium layer  31  acts as an etch stop layer so that very little of layer  31  has been removed at the point where CMP is terminated. 
         [0034]    Referring next to  FIG. 5 , all of layer  31 , other than trench liner layer  531 , is removed. This is accomplished in two steps, the first being removing at least 10%, by thickness, through CMP, followed by ion beam etching for about 2 minutes, at a temperature of about 25° C., to remove the equivalent of about 700 Angstroms of NiFe. Turning next to  FIGS. 6 and 7 , main pole layer  61  has been patterned over all surfaces to a thickness between about 500 and 900 Angstroms and then patterned and etched using ion beam etching. 
         [0035]      FIG. 8  shows an ABS view of the structure following the removal of alumina layer  22 . This is accomplished in two steps, first by RIE (reactive ion etching) using a Cl 2 /BCl 3  chemistry for about 2 minutes followed by etching in an alkaline solution such as NaOH or KOH with EDTA (ethylenediamine tetra-acetic acid) being preferred, having a pH greater than about 10.5 at a temperature of about 80° C. for about 9 seconds. 
         [0036]      FIG. 9  is a plan view of the structure which shows substrate  21  extending out beyond area  11  for the purpose of providing mechanical support for the write pole. 
         [0037]    Referring now to  FIGS. 10 and 11 , second ruthenium layer  101  is deposited over the full structure to a thickness between about 300 and 600 Angstroms and a precision level of ±5%. This serves primarily to cover the top surface of the write pole with non-magnetic write gap material, as seen in the ABS view of  FIG. 10 , but, as seen in  FIG. 11 , it also provides a conductive seed layer on which to grow the next layer through electrodeposition. This can be seen in  FIG. 12  (also an ABS view) where soft ferromagnetic layer  121  has been electrodeposited onto layer  101 . 
         [0038]    We refer next to  FIGS. 13 and 14 . These show the structure after layer  121  has been subjected to CMP until the portion of layer  101  that had been in contact with layer  121  is just exposed, leaving the slightly lower section of layer  101 , that is closest to the ABS, still covered with what was left of layer  121  at the conclusion of CMP. This is best seen in  FIG. 14  while  FIG. 13  presents the ABS view. 
         [0039]    Most of layer  101  (the portion that extends away from the ABS and overcoats main body  11 ) is now selectively removed using ion beam etching, as illustrated in  FIG. 15   a . Photoresist frame  151  is then formed on the tail end of layer  101 , as seen in  FIG. 15   b , followed by simultaneous electro-deposition of layers  181  (trailing shield) and  161  (top yoke), as seen in  FIG. 15   c.    
         [0040]    Referring now to  FIG. 15   d , photoresist frame  151  is stripped away, leaving behind empty trench  155 . This is followed by the deposition of alumina (or silica) refill layer  171  ( FIG. 15   e ), to a thickness between about 3,000 and 4,000 Angstroms, which is planarized using CMP, so that trench  155  is just filled. 
         [0041]    The next step is the formation of trailing shield  161  by deposition of a suitable seed layer which is then patterned so that a layer of soft magnetic material may be grown thereon. This is followed by a final CMP step that concludes the process. 
         [0042]      FIG. 16  is an ABS view of the finished structure with  FIG. 17  being a side view and  FIG. 18  a plan view. A 3-D (isometric) view is presented in  FIG. 19 . 
         [0043]    In conclusion, the main advantage of the process is a better track profile for a full side shielded PMR. Therefore, extendibility to high TPI (tracks per inch) applications for PMR can be more readily achieved with this new process and structure in comparison with conventional top shielded PMR heads