Abstract:
A method is disclosed for independently controlling track width and bevel angle of a write pole tip of a magnetic recording head. The method includes establishing the track width in the pole tip layer material utilizing E-beam lithography. A portion of this pole tip material having the established track width is protected by providing a temporary masking material to make a protected portion. At least one unprotected portion is left exposed to be shaped. This unprotected portion is then beveled to produce at least one beveled portion. The protected portion produces an upper pole tip portion which together with the beveled portion produce an improved pole tip. Also disclosed is a magnetic head having the improved pole tip, and a disk drive having a magnetic head having the improved pole tip.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to the manufacture of magnetic heads for data storage devices and more specifically to the fabrication of a narrow track width write pole tip for a magnetic head for a hard disk drive. 
         [0003]    2. Description of the Prior Art 
         [0004]    Data is conventionally written by a magnetic head and stored in a thin magnetic media layer of a hard drive disk. A typical magnetic recording head includes a trailing magnetic write pole, a leading return or opposing magnetic pole that is magnetically coupled to the write pole, and an electrically conductive induction coil disposed proximate the write pole and opposing pole. Current is passed through the induction coil to create magnetic flux within the write pole. The magnetic flux passes from the write pole tip, through the magnetic recording layer, and across to the opposing pole. Magnetization transitions on the magnetic layer of the recording disk are recorded by a trailing edge of the write pole tip and reproduce the shape of the pole tip projection on the media plane. Thus the size and shape of the pole tip is of significant importance in determining the density of data that can be stored on the disk. 
         [0005]    Increases in areal density have correspondingly required devising fabrication methods to substantially reduce the width of the write pole tip while maintaining track-width control (TWC) and preserving trailing edge structural definition (TED). As mentioned above, the writing process reproduces the shape of the write pole tip projection on the media, so the size of the pole tip limits the size of the data bits and thus the areal data storage density, and pole tips having widths of less than 200 nm are currently being manufactured. 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 pole tip shape at the air bearing surface (ABS) of the magnetic head is preferably not a simple rectangle, but is trapezoidal, with parallel top and bottom edges, and with a bevel angle preferably of approximately 5 to 15 degrees on the side edges. This is primarily done so that the pole tip fits into the curved concentric data tracks on the media without unwanted extension of the pole tip corners extending into an adjacent track, as is understood by those skilled in the art. 
         [0006]    Currently, photolithographic techniques are utilized to establish the track width of the write pole tip. Such photolithographic techniques are quite complicated, involving two or three layers of photoresist materials and masks to achieve acceptable results. Additionally, as the desired track width of the write pole tip is decreased in order to achieve higher areal data storage densities, the accuracy of such photolithographic techniques is reaching the limits of optical systems. 
         [0007]    Thus there is a need for a method of magnetic pole fabrication in which a narrow pole tip track width is accurately fabricated, and where the bevel angle and track width produced are controlled as independent variables. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is a method for accurately fabricating the pole tip track width while independently controlling track width and bevel angle of the pole tip. The method includes accurately establishing the track width in a portion of the pole tip material using an epoxy resist such as KMPR with E-beam exposure fabrication techniques. This pole tip portion having the established track width is then protected with a temporary masking material, while an unprotected pole tip portion is left exposed to be shaped. The unprotected portion is then milled to produce beveled side walls, while the protected portion includes the narrow track width trailing edge. Also disclosed is a magnetic head having a pole tip of the present invention, and a disk drive having the magnetic head. 
         [0009]    It is an advantage of the method for fabricating a magnetic head of the present invention that the track width of the write head pole tip can be accurately fabricated. 
         [0010]    It is another advantage of the method for fabricating a magnetic head of the present invention that track width of the write pole tip can be made smaller while retaining pole tip fabrication accuracy. 
         [0011]    It is a further advantage of the method for fabricating a magnetic head of the present invention that fabrication is made easier, since it is not necessary to attempt to control bevel angle and track width at the same time. 
         [0012]    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 
         [0013]    The following drawings are not made to scale as an actual device, and are provided for illustration of the invention described herein. 
           [0014]      FIG. 1  is a top plan view of an exemplary disk drive having a magnetic head of the present invention; 
           [0015]      FIG. 2  is a perspective view of view of an exemplary slider and suspension; 
           [0016]      FIG. 3  shows a top plan view of an exemplary read/write head; 
           [0017]      FIG. 4  is a cross-sectional view of an exemplary write head taken along lines  4 - 4  of  FIG. 3 ; and 
           [0018]      FIGS. 5-14  are views of various stages in the fabrication of the magnetic head pole tip of the magnetic head of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]      FIG. 1  is a top plan view that depicts significant components of a hard disk drive which includes the magnetic head of the present invention. The hard disk drive  10  includes a magnetic media hard disk  12  having a plurality of data tracks  13  that is rotatably mounted upon a motorized spindle  14 . An actuator arm  16  is pivotally mounted within the hard disk drive  10 , and a magnetic head  20  of the present invention is fabricated upon a slider  22  that is disposed upon a distal end  24  of the actuator arm  16 . A typical hard disk drive  10  may include a plurality of disks  12  that are rotatably mounted upon the spindle  14  and a plurality of actuator arms  16 , each having one or more magnetic heads  20  mounted upon the distal end  24  of the actuator arm. As is well known to those skilled in the art, when the hard disk drive  10  is operated, the hard disk  12  rotates upon the spindle  14  and the slider  22  acts as an air bearing that is adapted for flying above the surface of the rotating disk. The slider  22  includes a substrate base upon which the various layers and structures that form the magnetic head are fabricated. Such heads are fabricated in large quantities upon a wafer substrate and subsequently sliced into discrete sliders  22  each having a magnetic head  20 .  FIG. 2  shows a slider  22  in greater detail being supported by an actuator arm  16 . The magnetic head  20  is shown in dashed lines at the trailing edge of the slider  22 , and in greater detail in  FIGS. 3 and 4 . 
         [0020]    A magnetic head of the present invention may be either a perpendicular head or a longitudinal head, as those structures are known in the art; however, this detailed description will be focused on a perpendicular head configuration, where its application to a longitudinal head structure will be well understood by those skilled in the art. 
         [0021]    A typical perpendicular magnetic head  20  is depicted in  FIGS. 3 and 4 , wherein  FIG. 3  is a top plan view with cutaway portions and  FIG. 4  is a side cross-sectional view of the write head portion of a representative perpendicular magnetic head  20 . As is best seen in  FIG. 4 , the slider  22  has an air bearing surface (ABS)  26  which flies above the surface of a hard disk  12 . The disk  12  includes a high coercivity magnetic layer, also referred to as the hard layer  27 , that is fabricated on top of a magnetically soft layer  28 . 
         [0022]    The perpendicular head  20  typically includes a read head portion, which may have many differing structures as are known to those skilled in the art, and which is not shown here for simplicity. The write head portion of the head  20  includes a first magnetic pole  34  which is fabricated upon an insulation layer  36 . An induction coil structure  38 , which includes induction coil turns  40 , is fabricated upon the first magnetic pole  34 , where the coil turns  40  are typically formed within electrical insulation layers  42 . A second magnetic pole layer, typically termed a shaping layer  44 , is fabricated on top of the induction coil structure  38 , and a magnetic back gap piece  46  joins the back portions of the first magnetic pole  34  and the shaping layer  44 , such that magnetic flux can flow between them. The shaping layer  44  is fabricated so that a gap  48  is left between it and the air bearing surface (ABS)  26 , and an alumina fill is deposited across the surface of the wafer which results in filling the gap  48  in front of the shaping layer  44 . A second magnetic pole layer, also called a probe layer, which includes a second magnetic pole  50  with a second magnetic pole tip  52 , is fabricated upon the shaping layer  44  in magnetic flux communication with the shaping layer  44 . The shaping layer  44  channels and directs the magnetic flux into the second magnetic pole  50  and into the second magnetic pole tip  52 . 
         [0023]    The magnetic head  20  is subsequently encapsulated, such as with the deposition of an alumina layer  54 . Thereafter, the wafer is sliced into rows of sliders with magnetic heads, and the ABS surface of the heads is carefully polished and lapped and the discrete magnetic heads are formed. 
         [0024]    When the write head is operated, electrical current flowing through the induction coil structure  38  will cause magnetic flux  60  to flow through the magnetic poles  34 ,  50  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  60  to flow through the shaping layer  44 , through the second magnetic pole  50  to the narrow second magnetic pole tip  52 , and into the hard layer  27  and soft layer  28  of the hard disk  12 . This magnetic flux  60  causes magnetized data bits to be recorded in the high coercivity layer hard layer  27  where the magnetic field of the data bits is perpendicular to the surface of the disk  12 . The magnetic flux then flows into the magnetically soft underlayer  28  and disperses as it loops back towards the first magnetic pole  34 . The magnetic flux then flows through the back gap piece  46  to the shaping layer  44 , thus completing a magnetic flux circuit. In such perpendicular write heads, it is significant that at the ABS  26 , the first magnetic pole  34  is much larger than the second magnetic pole tip  52 , so that the density of the magnetic flux passing out from the high coercivity magnetic hard layer  27  is greatly reduced as it returns to the first magnetic 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. 
         [0025]      FIGS. 5-14  show various stages of the fabrication of the second magnetic pole tip  52  structure of the present invention as seen from the ABS, and the following discussion refers to all of these drawings generally. As depicted in  FIG. 5 , following the fabrication of the shaping layer  44  (see  FIG. 4 ), the alumina insulation layer  48  in front of the shaping layer is fabricated. A second magnetic pole layer  76 , which may consist of laminated layers of high magnetic moment and non-magnetic laminated pole materials such as CoFe or CoFeN or NiFe and Cr, Al 2 O 3 , Ru, Rh, etc., respectively, is fabricated on top of the alumina insulation layer  48  and shaping layer  44  (disposed behind the insulation layer  48  in  FIG. 5 ). On top of this, a thin non-magnetic film layer  78  of Ta/Rh, or C (such as diamond-like-carbon (DLC)) is deposited which acts as a cap layer. 
         [0026]    Thereafter, as depicted in  FIG. 6 , an E-beam resist layer  80  suitable for E-beam lithography is fabricated upon the cap layer  78 .  FIG. 6  depicts the width of the E-beam resist mask gap at the write pole tip location of the device. A typical E-beam resist is an epoxy based resist such as KMPR, which is an epoxy based alkaline developable negative resist, which is preferably deposited utilizing thin film spin deposition techniques. KMPR is an E-beam lithography resist marketed by MicroChem Corp., 1254 Chestnut Street, Newton, Mass.; KMPR is a registered trademark of MicroChem Corp. A desirable thickness of the E-beam  80  resist is from approximately 0.8 μm to approximately 2.0 μm, with a preferred thickness of approximately 1.5 μm. Thereafter, a negative resist E-beam mask  82  is fabricated upon the resist layer  80  to cover undesired resist portions and permit E-beam exposure to the unmasked desired portions of the E-beam resist in the desired shape of the second magnetic pole and particularly the second magnetic pole tip. 
         [0027]    Thereafter, as depicted in  FIG. 7 , E-beam lithography is conducted, as is known to those skilled in the art, and following E-beam exposure, the E-beam mask and the masked portions of the KMPR layer are removed, such as with the use of an alkaline stripper, as is known for use in lithography utilizing the KMPR resist. As can be seen in  FIG. 7 , the remaining exposed KMPR resist is fabricated to cover the shape of the desired second magnetic pole and its write pole tip  52 . 
         [0028]    As depicted in  FIG. 8 , ion milling is used to establish the final track width  90  of the write pole tip  52 , as indicted by the ion milling beam direction arrow  94 . Ion milling is a very directional milling process and this milling operation is done at a range of angles  98 , preferably in the range of 0-15 degrees from normal incidence to the wafer surface as indicated by the arrow  96 . The KMPR milling mask layer  84  protects a central portion  99  of the second magnetic pole material  76  and cap layer  78 , while the ion milling removes material from the unmasked portion of the pole material  76 , forming a write pole tip protrusion  100  of second magnetic pole material which will become the upper portion of the final second magnetic pole tip, as is discussed below. The write pole tip protrusion  100  includes sidewalls  102  that are generally perpendicular to the wafer surface. 
         [0029]    Thereafter, as depicted in  FIG. 9 , a thin layer of alumina  104  is deposited over the entire structure as it exists at this stage, including the second magnetic pole material  76 , cap layer  78  and mask  84 . The alumina  104  is preferably deposited utilizing atomic layer deposition (ALD) techniques, although other deposition techniques such as sputter deposition may be used. It is important that the side walls  102  of the write pole tip protrusion  100  are covered by initial wall portions  106  of the thin alumina layer. The initial wall portions  106  are formed with a thickness of from approximately 50 μm to approximately 200 μm. 
         [0030]    Next, as seen in  FIG. 10 , reactive ion milling (RIM) is next conducted as indicated by the arrow  110  to remove the alumina layer from the top of the mask  84  and second magnetic pole material  76 . RIM with fluorine reactive species is preferably used because the alumina has a selectively fast fluorine reactive ion milling rate, compared to the mask material and second magnetic pole material. The RIM process is also very directional, leaving remaining alumina wall portions  114  that act as temporary wall masks, while the alumina on more horizontal surfaces is milled away. This reactive ion milling operation is conducted at an angle  120 , preferably in the range of 0-15 degrees from normal incidence to the wafer surface as indicated by the arrow  96 . 
         [0031]      FIG. 11  shows the next stage in which standard ion milling using a gas such as argon is conducted at an angle  128  preferably in the range of 40-80 degrees from normal incidence  96  to the wafer surface. This is done to mill the sides of the second magnetic pole  76  away, down to and slightly into the alumina insulation layer  48 . As alumina has a slower milling rate under standard ion milling compared to the second magnetic pole material, the temporary wall masks act to preserve the second magnetic pole tip material  100  located directly behind them. Thus the remaining alumina wall portions  114  act as temporary wall masks to shield protected second magnetic pole tip portions  99  including the cap layer  78 , leaving the unprotected second magnetic pole material wall portions  132  to be shaped and beveled by the ion milling beam. As depicted in  FIG. 12 , following this ion milling step the protected second magnetic pole tip portions  99  will thus produce the upper portion  136  of the second magnetic pole tip  52 , while the wall sides are beveled to the appropriate angle of approximately 5-15 degrees to make beveled walls  140  of a beveled portion  144  of the second magnetic pole tip  52 . Thus the second magnetic pole tip  52  is produced with the track width  90  preserved in the upper portion  136 . 
         [0032]    As depicted in  FIG. 13 , a layer of alumina  144  is next deposited to fill and cover the second magnetic pole material and mask  84 . Chemical Mechanical Polishing (CMP) is then performed to remove the excess surface alumina and mask  84 . The cap layer  78  acts as a stop layer for the CMP. Further alumina fill  150  is thereafter deposited to encapsulate the second magnetic pole tip  52  and complete the fabrication of the second magnetic pole  50 . 
         [0033]      FIG. 14  shows a detail view of the completed second magnetic pole tip  52  of a second magnetic pole  50  of the present invention. A dashed line is used to identify the protected upper portion  100 , which becomes the upper portion  136  of the pole tip  52 , from the unprotected portion which becomes the beveled portion  144  having beveled walls  140 . The remaining cap layer  78  is also shown. No attempt has been made to make the relative proportions of the portions exactly to scale, and it is to be understood that there is much variation possible in the relative sizes of areas, as well as in the bevel angle and the track width. 
         [0034]    As discussed above, the method of the present invention using KMPR resist and E-beam resist track width formation techniques allows for the accurate fabrication of a very narrow second magnetic pole tip track width  90  at the trailing edge  160  of the upper portion  136 , and provides independent control of these crucial variables of bevel angle and the track width. The use of E-beam lithography in forming the write pole tip simplifies the magnetic head fabrication process as compared to the pre-existing process in which a plurality of layers of photoresist materials and mask materials must be deposited and fabricated prior to the milling of the write pole tip. Additionally, E-beam lithography facilitates the creation of a narrower write pole tip mask, which facilitates the fabrication of a narrower write pole tip, as is desired for increasing the areal data storage density of magnetic media and hard disk drives in which the write pole tips of the magnetic heads of the present invention are utilized. 
         [0035]    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.