Abstract:
A process for fabricating a magnetic recording transducer for use in a data storage system comprises providing a substrate, an underlayer and a first nonmagnetic intermediate layer deposited to a first thickness on and in contact with the underlayer, performing a first scanning polishing on a first section of the first intermediate layer to planarize the first section of the first intermediate layer to a second thickness, providing a main pole in the planarized first section of the first intermediate layer, providing a first pattern of photoresist on and in contact with the first section of the first intermediate layer, the pattern comprising an aperture to define a side shield trench, performing a wet etch to remove at least a portion of the first intermediate layer thereby exposing at least one of the plurality of main pole sides, and depositing side shield material in the side shield trench.

Description:
BACKGROUND 
       [0001]      FIG. 1  illustrates a conventional disk drive  10  used for data storage. Figures are not drawn to scale and only certain structures are depicted for clarity. Disk media  50  is attached to spindle motor and hub  20 . The spindle motor and hub  20  rotate the media  50  in a direction shown by arrow  55 . Head Stack Assembly (HSA)  60  includes a magnetic recording head  30  on actuator arm  70  and positions actuator arm  70  by positioning the voice coil motor (VCM)  25  over a desired data track, shown as recording track  40  in this example, to write data onto the media  50 . 
         [0002]      FIG. 1   a  illustrates an enlarged view of magnetic recording head  30  of  FIG. 1 . A magnetic recording transducer  90  may be fabricated on slider  80 . Slider  80  may be attached to suspension  75  and suspension  75  may be attached to actuator arm  70  as shown in  FIG. 2 . 
         [0003]    Referring again to  FIG. 1   a , Slider  80  is illustrated above recording track  40 . Media  50  and track  40  are moving under slider  80  in an in-track direction shown by arrow  42 . The cross-track direction is shown by arrow  41 . 
         [0004]    The magnetic recording transducer  90  has a leading edge  91  and a trailing edge  92 . In this embodiment, the trailing edge  92  of recording transducer  90  is the final portion of magnetic transducer  90  that writes onto the recording track  40  as the media moves under the slider  80  in direction  42 . 
         [0005]      FIG. 2  illustrates a side view of disk drive  10  shown in  FIG. 1 . At least one disk media  50  is mounted onto spindle motor and hub  20 . HSA  60  comprises at least one actuator arm  70  that carries suspension  75  and slider  80 . Slider  80  has an Air Bearing Surface (ABS) facing media  50 . When the media is rotating and actuator arm  70  is positioned over the media  50 , slider  80  floats above media  50  by aerodynamic pressure created between the slider ABS and the surface of media  50  facing the ABS of slider  80 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  illustrates a conventional disk drive in a top view. 
           [0007]      FIG. 1   a  illustrates a more detailed view of an area shown in  FIG. 1 . 
           [0008]      FIG. 2  illustrates a side view of the disk drive shown in  FIG. 1 . 
           [0009]      FIG. 3  illustrates a scanning polishing process. 
           [0010]      FIG. 4  illustrates a substrate before scanning polishing. 
           [0011]      FIG. 5  illustrates a substrate after scanning polishing. 
           [0012]      FIG. 6  illustrates an intermediate layer over a substrate before scanning polishing. 
           [0013]      FIG. 7  illustrates an intermediate layer with surface referenced scanning polishing. 
           [0014]      FIG. 8  illustrates an intermediate layer with thickness referenced scanning polishing. 
           [0015]      FIG. 9  illustrates trenches in an intermediate layer that has received thickness referenced scanning polishing. 
           [0016]      FIGS. 10-26  illustrate a process to provide a magnetic pole and shields using scanning polishing in one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0017]      FIG. 3  illustrates a scanning polishing process. A scanning ion source  300  may be operable to move a narrow ion beam  301  over substrate  310 . Scanning ion source  300  may move in an X or Y direction shown in axis  305  to move the narrow ion beam  301  over the substrate  310 . In one embodiment, narrow ion beam  301  may move across substrate  310  in first direction  320 , then down substrate  310  in second direction  330 ; and then alternating directions until the entire substrate  310  has been milled. Substrate  310  may have surface irregularity  340  that results from imperfect manufacture; for example, chemical mechanical polishing (CMP) dishing or crowning errors. The scanning polishing apparatus operates by scanning a target or receiving topographical information about the target from another means; and making a determination how much material is to be removed to provide improved planarization. In one embodiment the scanning operation may be performed simultaneously with polishing. The amount of material removed from substrate  310  may be controlled by varying the dwell time over the substrate  310  as the scanning ion source  300  is moved in the X or Y directions. A longer dwell time, or slower motion rate, will result in more material being removed by narrow ion beam  301 . 
         [0018]      FIG. 4  illustrates substrate  400  before scanning polishing. Substrates in the foregoing descriptions may comprise multiple layers and materials. Substrate  400  has surface irregularity  410 . Surface irregularity  410  is shown highly exaggerated and simplified for illustrative purposes. Actual surface irregularity, for example, that caused by CMP, may be complex and inconsistent, or may have regular patterns such as rings or swirls. In one embodiment, substrate  400  may have surface irregularity from approximately 15-200 nanometers (nm). 
         [0019]      FIG. 5  illustrates substrate  500  after scanning polishing. Substrate  500  has surface irregularity  510  after scanning polishing. Surface irregularity  510  has been reduced by scanning polishing to from approximately 0.1 nm-5 nm. 
         [0020]    In one embodiment, surface irregularity  510  may be measured by scanning the variation of top surface  520  from an ideal plane; this method hereinafter called surface referenced scanning. In another embodiment, surface irregularity  510  may be measured by scanning the thickness from top surface  520  to bottom  530  of substrate  500 ; this method hereinafter called thickness referenced scanning. Thickness referenced scanning may be performed by optical scanning, or by measurement of physical markers such as lapping guides. In some applications it may be desired to use surface referenced scanning polishing for subsequent operations; and in other applications, it may be desired to use thickness referenced scanning to provide a uniform thickness of the substrate, or of another layer on the substrate. 
         [0021]      FIG. 6  illustrates intermediate layer  610  over substrate  600  prior to scanning polishing. The substrate material  600  may be for example, AlTiC; and the intermediate material may be alumina (Al 2 O x ), although other materials may be used. Top surface irregularity  620  may conform to substrate surface irregularity  630 , or may be non-conformal. Non-conformal thickness in intermediate layer  610  thickness may result from uneven deposition of intermediate layer  610  over substrate  600 ; for example, due to spin coating, or application of a fluid layer that fills in depressions differently than high areas. 
         [0022]      FIG. 7  illustrates an intermediate layer  710  after surface referenced scanning polishing. Intermediate layer  710  may be provided on substrate  700 . Substrate  700  and/or intermediate layer  710  have undesirable surface irregularity that may affect subsequent operations. Portions of intermediate layer  710  are illustrated as fields leveled by surface referenced scanning polishing. Field  720  in intermediate layer  710  may be substantially flatter than either the original intermediate layer  610  illustrated in  FIG. 6  or the underlying substrate  700 . Field  720  may be one of multiple such fields, and a substrate may comprise numerous fields. Fields in some embodiments may be directly adjacent to one another, as shown by field  740  adjacent to field  750 , or may be separated as shown by unmilled section  724  between field  720  and field  730 . Field  720  has been flattened by scanning polishing first height  722  and second height  723  and the area therebetween in amounts needed to produce flat surface  721 . The thickness  725  of intermediate layer  720  under field  721  varies; however, surface  721  may be a substantially flat surface. The thickness  735  under surface  731  may also be a different thickness across field  730 , and different from the thickness  725  for field  720 . 
         [0023]    Scanning polishing fields for surface referenced scanning polishing or thickness referenced scanning polishing may be any suitable size. In one embodiment, the field size may be selected to correspond to a photolithographic flash field. In step-and-repeat photolithography, masks may not be a full wafer in size, and a single mask may be used many times to pattern an entire wafer. It is not necessary for the entire substrate to be flattened to a single plane, and may be advantageous to only flatten locally the area needed for a flash field. This may also reduce scanning polishing time. In one embodiment, a field size may be selected according to how much variation exists in an area. In one embodiment, one scanning polishing field may be flattened to accommodate multiple flash fields. 
         [0024]      FIG. 8  illustrates an intermediate layer  810  with thickness referenced scanning polishing. Intermediate layer  810  may be provided on substrate  800 . Substrate  800  and intermediate layer have undesirable surface irregularity that may affect subsequent operations. In some applications, it may be desirable to have a layer with highly uniform thickness. Portions of intermediate layer  810  are illustrated as leveled by thickness referenced scanning polishing. Field  820  in intermediate layer  810  has been thinned to thickness  825  by removing an amount  822  from the surface of intermediate layer  810 . Surface  821  may not be flat but may follow the contour of substrate  800  such that thickness  825  is uniform. Field  820  may be one of multiple such fields, and a substrate may comprise a large number of fields. Field  830  is illustrated with thickness  832  following the contour of underlying intermediate layer  800 , and surface  831  in a slightly different plane from surface  821 . Surface  840  has been milled by an amount  842  that may be less than amount  822 . This may occur if intermediate layer  810  is thicker in field  820 , for example due to uneven spin coating. 
         [0025]    In one embodiment thickness referenced scanning polishing may be combined with surface referenced scanning polishing to provide improvements in both layer thickness and surface flatness. In one embodiment, surface referenced scanning polishing may be performed first and thickness referenced scanning polishing may be performed second. This embodiment may be advantageous when the intermediate layer thickness variation is large compared to the substrate irregularity. In another embodiment, thickness referenced scanning polishing may be performed first and surface referenced scanning polishing may be performed second. This embodiment may be advantageous when the substrate irregularity is large compared to the intermediate layer irregularity. 
         [0026]      FIG. 9  illustrates trenches in an intermediate layer that has received thickness referenced scanning polishing. Intermediate layer  910  is on substrate  900  and has large field  930  and small field  940 . Large field  930  may comprise a single photolithographic flash field or multiple flash fields. Trenches  931 - 34  are formed in intermediate layer  910  and may extend to substrate  900 . In one embodiment, a stop layer may be between substrate  900  and intermediate layer  910 . Field  930  has received thickness referenced scanning polishing, so trenches  931 - 34  have uniform height, even though substrate  900  and intermediate layer  910  are uneven. 
         [0027]      FIGS. 10-26  illustrate process  100  to provide a magnetic pole and shields using scanning polishing in one embodiment of the invention. Figures are not to scale and some features are exaggerated for clarity. Steps that are well known in the art may be highly simplified or omitted from the figures. 
         [0028]      FIG. 10  illustrates substrate  101 , underlayer  102 , and an intermediate layer  103  on and in contact with underlayer  102 . Substrate  101  may comprise a magnetic or nonmagnetic material. Intermediate layer  103  may comprise alumina, and underlayer  103  may comprise an etch stop layer, dielectric layer, a metal layer, or nonmagnetic layer. A bottom anti-reflective layer (BARC) may also be used in place of or on top of underlayer  102  and may be removed in a later process. Intermediate layer  103  has surface irregularity  105 . Surface irregularity  105  may be a result of CMP error, uneven deposition of intermediate layer  103 , uneven underlayer  102 , or uneven substrate  101 . In one embodiment irregularity  105  may be greater than 15 nm. 
         [0029]      FIG. 11  illustrates intermediate layer  103  after scanning polishing. In one embodiment, intermediate layer  103  thickness has been milled to thickness  104  with a tolerance from approximately 0.1 nm to 1.5 nm using thickness referenced scanning polishing. In one embodiment, surface  106  of intermediate layer  103  has been milled to flat within 0.1 nm to 1.5 nm variations using surface referenced scanning polishing. 
         [0030]      FIG. 12  illustrates underlayer  102 , intermediate layer  103 ; and pole  120  deposited in liner  110  in intermediate layer  103 . In one embodiment, liner  110  may comprise ruthenium (Ru) and pole  120  may comprise alloys of cobalt, nickel, and iron, for example, CoNiFe or CoFe. Methods of forming a pole in a trench are known, and any suitable method may be used without departing from the scope of the invention. Since the thickness of intermediate layer  103  was closely controlled as described in  FIG. 11 , pole  120  height may also be very closely controlled. 
         [0031]    Pole  120  may be fabricated in intermediate layer  103  by forming a hard mask on intermediate layer  103 . The hard mask may comprise tantalum or ruthenium. A pole trench is etched into intermediate layer  103  and etching the pole trench may be by using reactive ion etching. Magnetic material may be plated in the main pole trench, and CMP performed to remove magnetic material above the hard mask, and removing the hard mask may be by reactive ion etching. 
         [0032]      FIG. 13  illustrates photo mask  130  and photo mask  131  provided on and in contact with intermediate layer  103  to pattern an aperture for etching a trench. Photo mask  131  covers pole  120  and liner  110  to prevent damage to pole  120  during etching, and photo mask  130  defines the location of the outer extent of the trench. Photo mask material may comprise any suitable photoresist. 
         [0033]      FIG. 14  illustrates trench  145  after wet etching. Intermediate material  103  has been removed from side  146  of liner  110 . Wet etching also forms side wall  141  on intermediate material  140  and exposes underlayer  102 . Photo mask  130  and photo mask  131  may be removed after trench  146  has been etched. 
         [0034]      FIG. 15  illustrates seed layer  150  deposited over the entire field comprising intermediate layer  140 , underlayer  102 , liner  110 , and pole  120 . In one embodiment, seed layer  150  may comprise NiFe. 
         [0035]      FIG. 16  illustrates photo mask  160  applied over seed layer  150  to provide a side shield trench  165  between pole  120  and intermediate layer  140 . Photo mask  140  defines an outer dimension of the side shield trench  165 . Although illustrated as a vertical outer wall in photo mask  140 , trench walls may be beveled, curved, canted, tilted or have other geometric shapes. 
         [0036]      FIG. 17  illustrates plating side shield  170  on seed layer  150  where not covered by photo mask  160 . Side shield  170  may also cover the top of pole  120 , removed in a later operation. In one embodiment, side shield  170  may comprise NiFe. In other embodiments, side shield  170  may comprise layers of material, and may incorporate magnetic coupling layers. In one embodiment, side shield  170  may be physically or magnetically coupled to an underlayer, for example, a bottom shield. 
         [0037]      FIG. 18  illustrates side shield  170 , intermediate layer  140 , and trench  180 . Seed layer  150  has been removed from trench bottom  185 , thereby exposing underlayer  102 . In one embodiment, seed layer  150  may be removed by ion milling. 
         [0038]      FIG. 19  illustrates side shield  170 , interlayer  102 , intermediate material  140  and trench  180 . Trench  180  is filled with intermediate material  190 . Intermediate material  190  may overfill intermediate material  140 , and Intermediate material  190  and intermediate material  140  may be the same material. 
         [0039]      FIG. 20  illustrates first CMP to expose side shield material  170  and provide rough planarization on the top of side shield  170 . CMP may be stopped a first distance  202  above the top of pole  120 . Due to the uneven CMP rates of different materials, intermediate material  195  may be over polished a distance  201  more than first distance  202 . In one embodiment first distance  202  may be from approximately 0.1 um to 0.2 um. 
         [0040]      FIG. 21  illustrates refilling intermediate material  210  over side shield  170  and over intermediate material  195  to correct CMP over polishing  201  illustrated in  FIG. 20 . Intermediate material  210  and intermediate material  195  may be the same material. In one embodiment intermediate material thickness  210  may be from approximately 0.1 um to 0.5 um. 
         [0041]      FIG. 22  illustrates a second CMP process to planarize intermediate material  210  surface  220  to a first thickness  221  above side shield  170 . First thickness  221  may be chosen to provide margin for subsequent operations and without risk of exposing side shield  170 . In one embodiment first thickness  221  may be at least 0.2 um. 
         [0042]      FIG. 23  illustrates a second scanning polishing operation to reduce the variation resulting from the second CMP operation described in  FIG. 22 . To prevent CMP damage to pole  120  due to over polishing in an attempt to remove side shield material  202  on top of pole  120 , side shield material  202  CMP was intentionally stopped prior to exposing the pole  120  to ensure the pole is not exposed or have excessively thin material over the pole; possibly due to polishing error and variation across the wafer. A second scanning polishing operation may be performed to mill surface  203  of side shield material  202  and intermediate material  220  to thickness  230  above pole  120 . 
         [0043]    In one embodiment, surface referenced scanning polishing may be used, and the surface referenced scanning polishing may be within a field as described in  FIG. 7  and accompanying descriptions. In one embodiment the surface referenced scanning polishing may remove material to thickness  230  above pole  120  to less than 0.25 um. In another embodiment, the surface referenced scanning polishing remove material thickness  230  above pole  120  to less than 0.1 um. 
         [0044]    In one embodiment, thickness referenced scanning polishing may be used, and the thickness referenced scanning polishing may be within a field as described in  FIG. 8  and accompanying descriptions. In one embodiment the thickness referenced scanning polishing may remove material to thickness  230  above pole  120  to less than 0.25 um. In another embodiment, the thickness referenced scanning polishing remove material to thickness  230  above pole  120  to less than 0.1 um. 
         [0045]      FIG. 24  illustrates removal of remaining side shield material  202  from the top of pole  120  using ion beam milling. The ion beam milling may employ stop milling by use of lapping guides, optical inspection, or time-based milling. Since the material to be removed may be very thin, very precise control of milling stop can be achieved. The methods described in the preceding operations are highly advantageous because they expose the pole top without the use of hard masks; as removal of hard masks can be difficult and may result in damage to the pole. 
         [0046]      FIG. 25  illustrates the deposition of write gap  250  on the top of pole  120  and liner  110 ; and may also extend over seed  150  and side shield  202 . In one embodiment, write gap  250  may comprise Ru; and in one embodiment, write gap  250  may comprise an atomic layer deposition of nonmagnetic material. 
         [0047]      FIG. 26  illustrates deposition of shield  265  over write gap  250  and intermediate material  260 . Shield material  265  may be the same material as side shield material  202  in previous figures, or may comprise a different shield material. The process used to deposit shield  265  and refill intermediate material  260  may follow the same processes as previously described. 
         [0048]    Although the foregoing has been described in terms of certain embodiments, other embodiments will be apparent to those of ordinary skill in the art from the disclosure herein. Figures are illustrative and not drawn to scale. For example, shields and poles shown as solids may employ gradients, or have ferromagnetic or antiferromagnetic coupling layers. Seed layers, BARC layers, photolithographic masking, residue removal, and plating details are well known in the art, and would be apparent to those of skill in the art. Common features that are known to those of ordinary skill in the art have been omitted or simplified in figures for clarity. The described embodiments have been presented by way of example only and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms without departing from the spirit thereof. Thus, the invention is not limited by any preferred embodiments, but is defined by reference to the appended claims.