Abstract:
A method of fabrication of the write head of a perpendicular recording head allows for production of P 3  pole tips of width less than 200 nm (200×10 −9  meters). The method includes fabricating the P 2  flux shaping layer, depositing the P 3  layer, depositing a layer of ion-milling resistant material, depositing at least one sacrificial layer, shaping the P 3  layer into P 3  pole tip, removing the at least one sacrificial layer to leave the P 3  pole tip, and encapsulating the P 3  pole tip.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to heads for high track density perpendicular magnetic recording, and more particularly relates to fabrication of poles of such heads.  
         [0003]     2. Description of the Prior Art  
         [0004]     Data has been conventionally stored in a thin media layer adjacent to the surface of a hard drive disk in a longitudinal mode, i.e., with the magnetic field of bits of stored information oriented generally along the direction of a circular data track, either in the same or opposite direction as that with which the disk moves relative to the transducer.  
         [0005]     More recently, perpendicular magnetic recording systems have been developed for use in computer hard disk drives. A typical perpendicular recording head includes a trailing write pole, a leading return or opposing pole magnetically coupled to the write pole, and an electrically conductive magnetizing coil surrounding the write pole. In this type of disk drive, the magnetic field of bits of stored information are oriented normally to the plane of the thin film of media, and thus perpendicular to the direction of a circular data track, hence the name.  
         [0006]     Media used for perpendicular recording typically include a hard magnetic recording layer and a soft magnetic underlayer which provide a flux path from the trailing write pole to the leading opposing pole of the writer. Current is passed through the coil to create magnetic flux within the write pole. The magnetic flux passes from the write pole tip, through the hard magnetic recording track, into the soft underlayer, and across to the opposing pole, completing a loop of flux.  
         [0007]     Perpendicular recording designs have the potential to support much higher linear densities than conventional longitudinal designs. Magnetization transitions on the bilayer recording disk are recorded by a trailing edge of the trailing pole and reproduce the shape of the trailing pole projection on the media plane, thus the size and shape of the pole tip is of crucial importance in determining the density of data that can be stored.  
         [0008]     Perpendicular magnetic recording is expected to supersede longitudinal magnetic recording due to the ultra-high density magnetic recording that it enables. Increases in areal density have correspondingly required devising fabrication methods to substantially reduces the width of the P 3  write pole tip  52  while maintaining track-width control (TWC) and preserving trailing edge structural definition (TED). As mentioned above, the writing process reproduces the shape of the P 3  write pole projection on the media plane, so the size of the P 3  limits the size of the data fields and thus the areal density. The current drive is to make P 3  poles of less than 200 nm (200×10 −9  meters). Making reliable components of such microscopic size has been a challenge to the fabricating process arts. This problem is made even more challenging because the P 3  pole shape at the ABS is preferably not a simple rectangle, but is trapezoidal, with parallel top and bottom edges, but a bevel angle preferably of approximately 8 to 15 degrees on the side edges. This is primarily done so that the P 3  pole tip fits into the curved concentric tracks without the corners extending into an adjacent track by mistake.  
         [0009]     Various approaches have been tried in an effort to shape such tiny components. Ion milling (IM) is a process that has been long used in the manufacture and shaping of such micro-components, but here there is the difficulty of maintaining the top edge dimension while trying to cut the side bevels. Initially, alumina was used as an IM hard mask for reliable beveled (8-15 degree) track-width definition (TWD) in the 330-300 nm range but was later changed to carbon to further extend the IM process to smaller dimensions. The complication in developing an IM scheme is the inability to consistently achieve a TWC process and preserve TED due to inefficient resistance of the hard mask to passivate TED. Carbon such as diamond-like-carbon (DLC) does offer a higher milling resistance over alumina to preserve TED for the 300-250 m range of TWD. But there are inherent difficulties in depositing sufficient carbon film thickness to provide adequate TED protection because as the film&#39;s thickness increases, stress may result in delamination or wafer bowing. Thus the ability to extend the P 3  carbon process to track-width dimension below 200 nm will be increasingly problematic. Moreover, at TWD below 200 nm, the pole piece will be fragile and removal of redeposited materials (milling nonvolatile by-products) on top and sides of the pole tip will be increasingly more difficult.  
         [0010]     Thus, there is a need for a method for fabricating P 3  pole tips for track widths less than 200 nm for perpendicular recording.  
       SUMMARY OF THE INVENTION  
       [0011]     A method of fabrication of the write head of a perpendicular recording head allows for production of P 3  pole tips of width less than 200 nm (200×10 −9  meters). The method is practiced by fabricating the P 2  flux shaping layer, depositing the P 3  layer, depositing a layer of ion-milling resistant material, depositing at least one sacrificial layer (PS), shaping the P 3  layer into P 3  pole tip, removing the at least one sacrificial layer to leave the P 3  pole tip, and encapsulating the P 3  pole tip.  
         [0012]     It is an advantage of the present invention that the PS layer can be fabricated with a high aspect ratio which offers higher milling resistance and allows for better passivation.  
         [0013]     It is another advantage of the present invention that better Trailing Edge structural Definition (TED) than before can be produced.  
         [0014]     It is a further advantage of the present invention that improved Track Width Control (TWC) can be achieved. It is an advantage of the present invention sub-micron track widths can be obtained.  
         [0015]     It is yet another advantage of the present invention that this process minimizes redepostion of materials.  
         [0016]     It is a further advantage of the present invention that this process allows for adaptive track width control.  
         [0017]     Yet another advantage of the present invention is that the write pole is preferably encapsulated and that its chances of corrosion or damage are minimized.  
         [0018]     These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawing. 
     
    
     IN THE DRAWINGS  
       [0019]     The following drawings are not made to scale as an actual device, and are provided for illustration of the invention described herein.  
         [0020]      FIG. 1  is a side cross-sectional view depicting various components of the write head of a prior art perpendicular head;  
         [0021]      FIG. 2  is a front plan view of the Air Bearing Surface of a write head in a stage of fabrication;  
         [0022]      FIG. 3  is a front plan view of the Air Bearing Surface of a write head in another stage of fabrication;  
         [0023]      FIG. 4  is a front plan view of the Air Bearing Surface of a write head in yet another stage of fabrication;  
         [0024]      FIG. 5  is a front plan view of the Air Bearing Surface of a write head in another stage of fabrication;  
         [0025]      FIG. 6  is a front plan view of the Air Bearing Surface of a write head in yet another stage of fabrication; and  
         [0026]      FIG. 7  is a front plan view of the Air Bearing Surface of a write head in a final stage of fabrication.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     To aid in the understanding of the structures involved in the present invention, the following discussion is included with reference to the prior art illustrated in  FIG. 1 .  
         [0028]      FIG. 1  (prior art) is a side cross-sectional diagram of the write head portion of a typical prior art perpendicular magnetic head. A slider  20  has an air bearing surface (ABS)  22  which flies above the surface of a hard disk  24 . The disk  24  includes a high coercivity magnetic layer, also referred to the hard layer  26  that is fabricated on top of a magnetically soft layer  28 .  
         [0029]     The perpendicular head  30  typically includes a read head, which is not shown here. The write head portion includes a first magnetic pole P 1   34  is fabricated upon an insulation layer  36 . An induction coil structure  38 , which includes coils  40 , is fabricated upon the P 1  pole  34 . The coil turns 40 are typically formed within electrical insulation layers  42 . A second magnetic pole layer, typically termed a P 2  shaping layer  44 , is fabricated on top of the induction coil structure  38 . A magnetic back gap piece  46  joins the back portions of the P 1  pole  34  and the P 2  shaping layer  44 , such that magnetic flux can flow between them. The P 2  shaping layer  44  is fabricated so that a gap  48  is left between it and the rest of the ABS  22 , and an alumina fill is deposited across the surface of the wafer which results in filling the gap  48  in front of the P 2  shaping layer  44 . A P 3  layer  50 , also called a probe layer, includes a P 3  pole tip  52 , and is in magnetic flux communication with the P 2  shaping layer  44 . The P 2  shaping layer channels and directs the magnetic flux into the P 3  pole tip  52 .  
         [0030]     The magnetic head  30  is subsequently encapsulated, such as with the deposition of an alumina layer  54 . Thereafter, the wafer is sliced into rows of magnetic heads, and the ABS surface of the heads is carefully polished and lapped and the discrete magnetic heads are formed.  
         [0031]     Electrical current flowing through the induction coil structure  38  will cause magnetic flux  2  to flow through the magnetic poles  34 ,  52  of the head, where the direction of magnetic flux flow depends upon the direction of the electrical current through the induction coil. In one direction, current will cause magnetic flux  2  to flow through the P 2  shaping layer  44  through the P 3  layer  50  to the narrow pole tip  54  into the hard layer  24  and soft layer  28  of the hard disk  24 . This magnetic flux  2  causes magnetized data bits to be recorded in the high coercivity layer hard layer  24  where the magnetic field of the data bits is perpendicular to the surface of the disk  24 . The magnetic flux then flows into the magnetically soft underlayer  28  and disperse as they loop back towards the P 1  pole  34 . The magnetic flux then flows through the back gap piece  46  to the P 2  shaping layer  44 , thus completing a magnetic flux circuit. In such perpendicular write heads, it is significant that at the ABS  22 , the P 1  pole  34  is much larger than the P 3  pole tip  52  so that the density of the magnetic flux passing out from the high coercivity magnetic hard layer  26  is greatly reduced as it returns to the P 1  pole layer  34  and will not magnetically affect, or flip, the magnetic field of data bits on the hard disk, such as bits on data tracks adjacent to the track being written upon.  
         [0032]     Stages in the process of fabrication of a P 3  pole tip for a write head for perpendicular recording are shown in  FIGS. 2-7 . In these figures, it will be assumed that the lower layers such as the first pole P 1   34 , the induction coil structure  38 , and insulation layer  42  (see  FIG. 1 ) have been already formed in a conventional manner.  
         [0033]      FIGS. 2-7  show the structure as seen from the ABS. In  FIG. 2 , the P 2  shaping layer has been deposited, but is not visible behind the alumina fill layer  48 , as the P 2  layer does not extend to the ABS, as discussed above. The P 3  pole tip  52  layer consists of multi-layers of high magnetic moment (B s ) and non-magnetic laminated pole material such as CoFe or CoFeN or NiFe or their alloys and Cr, Al 2 O 3 , Ru, etc., respectively which have been deposited, and then a layer of material which is resistant to ion milling, such as Al 2 O 3  or Ta 2 O 5  or SiO x N y  or their alloys are deposited. Generally, insulation materials may be used also. This thin nonmagnetic layer will function as a CMP stop layer  60  and the “clean-up” layer. This is followed by a non-magnetic film seed layer  62  (Rh preferred). A layer of photo-resist  64  of given thickness is put down, and a cavity  66  is produced which will be filled in the next step.  
         [0034]     In  FIG. 3 , the cavity has been filled with material to form a sacrificial layer, also referred to as PS  68 . The material of this sacrificial layer is preferably NiP, although other plated materials, (both non-magnetic, and magnetic, as will be discussed later) with high ion milling resistance may also be used. The photo-resist layer is then removed, resulting in the structure seen in  FIG. 3 . This PS  68  layer is used as an ion mill mask  70  to pattern the P 3  layer  52 , (to be discussed below). In a preferred process design, the PS  68  and CMP stop layer  60  materials are resistant to ion milling and also have similar ion milling rates, but the CMP stop layer  60  is preferred to have a slightly lower ion mill rate. In this case, when the PS  68  is trimmed to target track-width, the CMP stop layer  60  is also trimmed. The CMP stop layer  60  is used both to bevel the P 3  pole tip  52  and as a CMP stop. The role of PS  68  is for patterning the write pole and transferring it to the CMP stop layer  60  and pole tip materials. The material for PS  68  is preferably non-magnetic (also the seed-layer such as Rh) so that traces of it can potentially be left in the head without interfering with the heads&#39; performance. Moreover, it is desirable to plate PS  68  as thick as lithographically possible to achieve higher passivation and ion milling resistance.  
         [0035]     In  FIG. 4 , ion milling is used to cut through the layers  52 ,  60 ,  62 . The seed-layer  62  is first removed, and then the trackwidth of PS  68  is preferably reduced before ion milling of CMP stop layer  60  and P 3  pole tip  52  is started. By reducing the width of the PS layer  68 , the width of the P 3  pole tip layer  52 , CMP stop layer  60  and seed layer  62  beneath are also reduced.  
         [0036]     Next ion milling is used again to bevel the sides of the P 3  pole tip  52 , as shown in  FIG. 5 . The sacrificial layer PS  68  and the seed layer  62  both erode slightly faster during this process, but the CMP stop layer  60 , which is preferred slightly higher in ion milling resistance than PS  68  acts as a secondary mask  72  so that the top edge of the P 3  pole tip  52  is protected, as shown in  FIG. 5 . CMP stop layer  60  is also used as a mask to bevel the pole piece.  
         [0037]     As the trackwidth of the write pole shrinks, re-deposition and fencing on the side wall of the write pole  52  become a problem for removal since the pole tip  52  is so small (200 nm) and has a higher risk of being damage. In the present invention, after the P 3  write pole  52  is defined, it is encapsulated with Al 2 O 3  or an insulator material. The encapsulation material provides mechanical strength to the pole and minimizes it from corrosion (CoFe in the pole). As CMP is used to remove PS  68 , re-deposition and fencing are removed.  
         [0038]     Therefore, after defining the P 3  write pole  52  with ion milling, the write pole  52 , CMP stop layer  60 , remaining seed layer  62  and remaining PS  68  are encapsulated with an insulator such as alumina, which is preferably also of the same material used in the CMP stop layer  60 .  
         [0039]     CMP is then used to remove the remaining PS  68 , and seed layer  62 . As discussed above, the encapsulating material is preferred to be similar to CMP stop layer  60 , so that as CMP is used to remove PS  68  the removal rate is selective toward PS  68  material. After a while, as CMP encounters the same material, used as the CMP stop layer  60  and encapsulating material  74 , the rate slows.  
         [0040]     When the remaining PS layer  68  have been removed, the result is a planarized top surface of CMP stop layer  60  and encapsulating material  74  around the finished P 3  pole tip  52 , whose width preferably is on the order of 200 nm or less. This structure is shown in  FIG. 7 .  
         [0041]     In the discussion above, it has been preferred that non-magnetic material is used, so that if the CMP does not completely remove the seed layer  62  and PS  68 , the performance of the head will not be compromised. However, if in fact the seed layer  62  and PS  68  are completely removed, magnetic material may alternately be used for these layers  62 ,  68 .  
         [0042]     Thus, the present invention fabricates a sacrificial plated NiFe layer (PS) above a full-film magnetic layer where P 3  will be defined. The higher aspect ratio of the PS layer offers higher milling resistance and allows for better passivation, TED, and TWD than previously disclosed methods.  
         [0043]     While the present invention has been shown and described with regard to certain preferred embodiments, it is to be understood that modifications in form and detail will no doubt be developed by those skilled in the art upon reviewing this disclosure. It is therefore intended that the following claims cover all such alterations and modifications that nevertheless include the true spirit and scope of the inventive features of the present invention.  
         [0044]     THIS CORRESPONDENCE CHART IS FOR EASE OF UNDERSTANDING AND INFORMATIONAL PURPOSES ONLY, AND DOES NOT FORM A PART OF THE FORMAL PATENT APPLICATION. 
     20  slider      22  ABS      24  disk      26  hard layer      28  soft layer      30  perpendicular head      32  write head      34  first pole P 1       36  insulation layer      38  induction coil structure      40  coils      42  insulation layer      44  P 2  shaping layer      46  magnetic back gap      48  alumina fill      50  P 3  probe layer      52  P 3  pole tip      54  alumina layer      60  CMP stop layer      62  seed layer      64  photo-resist      66  cavity      68  PS sacrifical layer      70  IM mask      72  secondary mask      74  encapsulating material layer