Abstract:
An inductive write element is disclosed for use in a magnetic data recording system. The write element provides increased data rate and data density capabilities through improved magnetic flux flow through the element. The write element includes a magnetic yoke constructed of first and second magnetic poles. The first pole includes a pedestal constructed of a high magnetic moment (high B sat ) material, which is preferably FeRhN nanocrystalline films with lamination layers of CoZrCr. The second pole includes a thin inner layer of high B sat  material (also preferably FeRhN nanocrystalline films with lamination layers of CoZrCr), the remainder being constructed of a magnetic material capable of being electroplated, such as a Ni—Fe alloy. An electrically conductive coil passes through the yoke between the first and second poles to induce a magnetic flux in the yoke when an electrical current is caused to flow through the coil. Magnetic flux in the yoke produces a fringing field at a write gap whereby a signal can be imparted onto a magnetic medium passing thereby.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a Divisional of U.S. application Ser. No. 09/617,791, filed Jul. 18, 2000, now U.S. Pat. No. 6,618,223, Sep. 9, 2003, which is hereby incorporated by reference in its entirety. 

   FIELD OF THE INVENTION 
   The present invention relates to magnetic data recording and more specifically to a method for making a high data rate, high data density inductive writer. 
   BACKGROUND OF TH INVENTION 
   Magnetic disk drives are used to store and retrieve data for digital electronic apparatus such as computers. In  FIGS. 1A and 1B , a magnetic disk data storage system  10  of the prior art includes a sealed enclosure  12 , a disk drive motor  14 , one or more magnetic disks  16 , supported for rotation by a drive spindle  18  of motor  14 , and an actuator  20  including at least one arm  22 , the actuator being attached to a pivot bearing  24 . Suspensions  26  are coupled to the ends of the arms  22 , and each suspension supports at its distal end a read/write head or transducer  28 . The head (which will be described in greater detail with reference to  FIGS. 2A and 2B ) typically includes an inductive write element with a sensor read element. As the motor  14  rotates the magnetic disk  16 , as indicated by the arrow R, an air bearing is formed under the transducer  28  causing it to lift slightly off of the surface of the magnetic disk  16 , or, as its is termed in the art, to “fly” above the magnetic disk  16 . Alternatively, some transducers, known as contact heads, ride on the disk surface. Various magnetic “tracks” of information can be written to and/or read from the magnetic disk  16  as the actuator  20  causes the transducer  28  to pivot in a short arc across a surface of the disk  16 . The pivotal position of the actuator  20  is controlled by a voice coil  30  which passes between a set of magnets (not shown) to be driven by magnetic forces caused by current flowing through the coil  30 . 
     FIG. 2A  shows the distal end of the head  28 , greatly enlarged so that a write element  32  incorporated into the head can be seen. The write element  32  includes a magnetic yoke  34  having an electrically conductive coil  36  passing therethrough. 
   The write element  32  can be better understood with reference to  FIG. 2B , which shows the write element  32  and an integral read element  38  in cross section. The head  28  includes a substrate  40  above which the read element  38  and the write element  32  are disposed. A common edge of the read and write elements  38 ,  32 , defines an air bearing surface ABS, in a plane  42 , which can be aligned to face the surface of the magnetic disk  16  (see  FIGS. 1A and 1B ). The read element  38  includes a first shield  44 , a second shield  46 , and a read sensor  48  that is located within a dielectric medium  50  between the first shield  44  and the second shield  46 . The most common type of read sensor  48  used in the read/write head  28  is the magnetoresistive (AMR or GMR) sensor, which is used to detect magnetic field signal changes in a magnetic medium by means of changes in the resistance of the read sensor imparted from the changing magnitude and direction of the magnetic field being sensed. 
   The write element  32  can be better understood with reference to  FIG. 2B , which shows the write element  32  and an integral read element  38  in cross section. The head  28  includes a substrate  40  above which the read element  38  and the write element  32  are disposed. A common edge of the read and write elements  38 ,  32 , defines an air bearing surface ABS, in a plane  42 , which can be aligned to face the surface of the magnetic disk  16  (see  FIGS. 1A and 1B ). The read element  38  includes a first shield  44 , a second shield  46 , and a read sensor  48  that is located within a dielectric medium  50  between the first shield  44  and the second shield  46 . The most common type of read sensor  48  used in the read/write head  28  is the magnetoresistive (AMR or GMR) sensor, which is used to detect magnetic field signal changes in a magnetic medium by means of changes in the resistance of the read sensor imparted from the changing magnitude and direction of the magnetic field being sensed. 
   The write element  32  is typically an inductive write element that includes the second shield  46  (which functions as a first pole for the write element) and a second pole  52  disposed above the first pole  46 . Since the present invention focuses on the write element  32 , the second shield/first pole  46  will hereafter be referred to as the “first pole”. The first pole  46  and the second pole  52  contact one another at a backgap portion  54 , with these three elements collectively forming the yoke  34 . The combination of a first pole tip portion and a second pole tip portion near the ABS are sometimes referred to as the ABS end  56  of the write element  32 . Some write elements have included a pedestal  55  which can be used to help define track width and throat height. A write gap  58  is formed between the first and second poles  46  and  52  in the area opposite the back gap portion  54 . The write gap  58  is filled with a non-magnetic, electrically insulating material that forms a write gap material layer  60 . This non-magnetic material can be either integral with or separate from a first insulation layer  62  that lies upon the first pole  46  and extends from the ABS end  56  to the backgap portion  54 . The conductive coil  36 , shown in cross section, passes through the yoke  34 , sitting upon the write gap material  60 . A second insulation layer  64  covers the coil and electrically insulates it from the second pole  52 . 
   An inductive write head such as that shown in  FIGS. 2A and 2B  operates by passing a writing current through the conductive coil  36 . Because of the magnetic properties of the yoke  28 , a magnetic flux is induced in the first and second poles  46  and  52  by write currents passed through the coil  36 . The write gap  58  allows the magnetic flux to fringe out from the yoke  34  (thus forming a fringing gap field) and to cross the magnetic recording medium that is placed near the ABS. 
   With reference to  FIG. 2C , a critical parameter of a magnetic write element is the trackwidth of the write element, which defines track density. For example, a narrower trackwidth can result in a higher magnetic recording density. The trackwidth is defined by the geometries in the ABS end  56  of the yoke. For example, the track width can be defined by the width W 3  of the pedestal  55  or by the width W 1  of the second pole  52 , depending upon which is smaller. The widths W 3  and W 1  can be the same, such as when the second pole  52  is used to trim the pedestal  55 . Alternatively, in designs that have no pedestal at all it would be possible to define the trackwidth by the width W 2  of the first pole. 
   With reference to  FIG. 2B , the fringing gap field of the write element can be further affected by the positioning of the zero throat level ZT. ZT is defined as the distance from the ABS to the first divergence between the first and second pole, and it can be defined by either the first or second pole  46 ,  52  depending upon which has the shorter pole tip portion. Pedestal defined zero throat is defined by the back edge of the pedestal and is accomplished by moving the second insulation layer  64  back away from the ABS. Alternatively, zero throat can be defined by the geometry of the second pole  52 , by allowing the second insulation layer  64  to extend over the top of the pedestal. In order to prevent flux leakage from the second pole  52  into the back portions of the first pole  46 , it is desirable to provide a zero throat level that is well defined with respect to the plane of the ABS. Furthermore, a pedestal defined zero throat is beneficially defined along a well defined plane that is parallel with the plane  42  of the ABS, whereas a zero throat defined by the second pole occurs along the sloped edge of the second insulation layer  64 . As will be appreciated upon a reading of the description of the invention, the present invention can be used with either pedestal defined zero throat or a second pole defined zero throat. Thus, accurate definition of the trackwidth, and zero throat is critical during the fabrication of the write element. 
   The performance of the write element is further dependent upon the properties of the magnetic materials used in fabricating the poles of the write element. In order to achieve greater overwrite performance, magnetic materials having a high saturation magnetic flux density (high B sat ) are preferred. A common material employed in forming the poles is high Fe content (55% Fe) NiFe alloy having a B sat  of about 16 kG. However, high Fe content NiFe alloy has a high magnetostriction constant λs (on the order of 10 −5 ) which causes undesirable domain formation in the poles. It is known that the domain wall motion in the writer is directly related to the increase in popcorn noise in the read element, especially when the motion occurs in the first pole, which also serves as a shield for the read element. A reduction in popcorn noise in the read element can be achieved through the use of soft magnetic materials, (i.e. materials having a low magnetostriction constant) in the fabrication of the first pole  46 . However, such materials generally have limited B sat . 
   Therefore, there remains a need for a write element having the ability to concentrate a high degree of magnetic flux in the ABS end of the write element, while minimizing or eliminating popcorn noise caused by magnetostrictive properties of the write element. Such a write element would preferably provide a narrow and accurately controlled trackwidth as well as providing high overwrite, low non-linear transition shift, a high areal density and high data rate. 
   SUMMARY OF THE INVENTION 
   The present invention provides an inductive write element having improved magnetic performance characteristics, including high overwrite, low non-linear transition shift, high areal density and high data rate. The write element includes first and second poles, each constructed of a magnetic material and joined to one another to form a magnetic yoke. The poles are joined to one another at one end to form a back gap region, the other end having a write gap defined between the poles. An electrically conductive coil passes through the yoke between the first and second pole, and insulating material electrically isolates the electrically conductive coil from the magnetic yoke. The second pole includes a layer of a laminated high magnetic moment material, sputter deposited as a sheet film across the inner surface of the pole adjacent to the insulation material and write gap. 
   The present invention provides an inductive write element having improved magnetic performance characteristics, including high overwrite, low non-linear transition shift, high areal density and high data rate. The write element includes first and second poles, each constructed of a magnetic material and joined to one another to form a magnetic yoke. The poles are joined to one another at one end to form a back gap region, the other end having a write gap defined between the poles. An electrically conductive coil passes through the yoke between the first and second poles, and insulating material electrically isolates the electrically conductive coil from the magnetic yoke. The second pole includes a layer of a laminated high magnetic moment material, sputter deposited as a sheet film across the inner surface of the pole adjacent to the insulation material and write gap. 
   Forming only the inner portion of the second pole of high magnetic moment material and the remainder of a material such as NiFe advantageously allows the write element to be formed using currently available manufacturing techniques. Currently available high magnetic moment materials cannot be deposited by electroplating and are generally sputter deposited. By first sputter depositing the high magnetic moment material and then plating the remainder of the second pole with the lower magnetic moment material, the plated portion of the pole can be used as a mask to etch the sputtered material to provide the desired second pole configuration. 
   In an embodiment of the invention, the first pole can include a pedestal formed of the laminated high magnetic moment material, sputter deposited as a sheet film. Such a pedestal would be formed in the region of the write gap and would beneficially concentrate magnetic flux in the desired portion of the write gap. As an aspect of the invention, the high magnetic moment material used in the first and second poles can be FeXN, where X is a material selected from the group consisting of Rh, Ta, Al, Ti and Zr. The high magnetic moment material can additionally be laminated with layers of a dielectric film which more preferably can be a cobalt based amorphous ferro-magnetic material, and most preferably is CO 90 Zr 9 Cr. CO 90 Zr 9 Cr has been found to improve anisotropic properties. Such laminated materials can preferably include layers of high magnetic moment materials on the order of 500 Angstroms thick, interspersed with lamination layers of cobalt based amorphous ferro-magnetic material or alternatively of a non-magnetic material in layers that are roughly 50 Angstroms thick. 
   These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following descriptions of the invention and a study of the several figures of the drawings. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, with like reference numerals designating like elements. 
       FIG. 1A  is a partial cross-sectional front elevation view of a magnetic data storage system of the background art; 
       FIG. 1B  is a top plan view taken along line  1 B— 1 B of  FIG. 1A ; 
       FIG. 2A  is a is a plan view of a portion of a read/write head, shown greatly enlarged; 
       FIG. 2B  is a view taken from line  2 B— 2 B of  FIG. 2A , shown enlarged; 
       FIG. 2C  is a view taken from line  2 C— 2 C of  FIG. 2B ; 
       FIG. 3  is a view similar to  FIG. 2B  showing a read/write head of the present invention in cross section; 
       FIG. 4  is a flowchart illustrating a process for constructing a write element embodying the present invention; and 
       FIG. 5  is a view taken from line  5 — 5  of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   With reference to  FIG. 3  the present invention is embodied in a merged read/write head  66  including a read element  68  and an integral write element  70 , both of which are built upon a substrate  72 . The read element  68  having been described with reference to the background of the invention, the present description will focus on the write element  70 , which embodies the subject matter of the present invention. 
   The write element  70  includes first and second poles  74 ,  76 , which together join to form a magnetic yoke  78 . The poles  74 ,  76  join at one end to form a back-gap  80 , and are separated from one another everywhere else. Opposite the back-gap, each pole  74 ,  76  terminates in a pole tip  82 ,  84 . Opposite the back gap  80 , the poles  74 ,  76  are separated by a write gap  88 . A layer of dielectric write gap material  89  fills the write gap and extends beyond the write gap into the interior of the yoke  78 . An electrically conductive coil  90  passes through the yoke  78  sitting atop the write gap material layer  89 . 
   With continued reference to  FIG. 3 , the first pole  74  is constructed of a magnetic material having soft magnetic properties (i.e. low magnetostriction), preferably permalloy. Such soft magnetic properties are necessary to avoid domain boundary movement and associated popcorn noise in the read element  68 . The first pole  74  includes a pedestal  92 , disposed opposite the back-gap  80 . The pedestal is constructed of a high magnetic moment material and functions to concentrate magnetic flux. While plated high magnetic moment materials do not generally exhibit soft magnetic properties, the pedestal is located far enough away from the read element  68  and is sufficiently small in size as compared with the rest of the first pole  74  so as to not generate undesirable popcorn noise. To further improve performance, the pedestal is preferably constructed of FeXN nanocrystalline films with lamination layers of CoZrCr, which has been found to exhibit excellent magnetic properties including high magnetic moment and relatively low magnetostriction. The FeXN and the lamination layers are preferably sputter deposited onto a flat wafer that has been planarized using by chemical mechanical polishing (CMP). 
   With continued reference to  FIG. 3 , a first insulation layer  94  covers the first pole, having a smooth flat upper surface that is flush with the smooth flat upper surface of the pedestal  92 . While this first insulation layer can be of many suitable materials having a high electrical resistance it is preferably constructed of Al 2 O 3 . 
   With reference still to  FIG. 3 , the write gap material layer  89  sits atop the smooth coplanar surfaces of the first insulation layer  94  and the pedestal  92 . The write gap material layer is preferably constructed of Al 2 O 3  or alternatively of SiO 2 . The coil  90  sits atop the write gap material layer  89  and is also covered by a second insulation layer  96 , which insulates the coil  90  from the second pole  76  as well as insulating the winds of the coil  90  from one another. The second insulation layer has smoothly rounded edges formed by a curing process that will be described in greater detail below. 
   With continued reference to  FIG. 3 , the second pole  76  includes a high magnetic moment layer  98 . The remainder of the second pole  76  consists of a secondary layer  100 , constructed of a magnetic material such as plated Ni—Fe alloy, which can be readily electroplated and which exhibits good corrosion resistance. The high magnetic moment material layer  98 , which is preferably constructed of laminated FeXN nanocrystalline films with lamination layers of CO 90 Zr 9 Cr, improves performance of the head by facilitating magnetic flux flow through the second pole  76 , thereby resulting in a stronger fringing field at the write gap. The secondary layer  100 , which preferably makes up the bulk of the second pole  76 , provides a mask for etching the high magnetic moment material layer  98  as will be described in greater detail below. In order to minimize apex reflection during the photolithograpy process used to define the top pole, it is desirable that the edge of the coil insulation layer  96  be placed further from the ABS than the pedestal edge, in which case the zero throat is defined by the pedestal. Apex reflection is a major source of trackwidth variation during the fabrication of the top pole. By moving the coil insulation layer  96  away from the ABS and plating the second pole  76  onto a flat surface in the area near the ABS, the trackwidth can be more easily controlled. The high magnetic moment layer  98  is preferably on the order of 1 to a few times the thickness of the write gap  88 . In one embodiment the high magnetic moment layer  98  is roughly 0.5 um thick while the remainder of the second pole  76  is roughly 2 um thick and the pedestal is roughly 1 um thick. The throat height is preferably 3–10 times the thickness of the write gap  88 . 
   In an alternate embodiment of the invention, not shown, the second pole includes a layer of laminated high magnetic moment material as discussed above, but the first pole includes no pedestal. In another embodiment, the first pole includes a pedestal constructed of laminated high magnetic moment material, but the second pole does not include a laminated high magnetic moment layer. Such a construction could be useful where magnetic flux saturation is a problem. For example, if saturation were experienced in the pedestal of the first pole, then removing the high magnetic moment material from the second pole would decrease flux flow through the second pole, thereby preventing saturation at the pedestal. Similarly, when saturation is experienced in the second pole, the design having a high magnetic moment layer in the second pole and no pedestal on the first pole would promote flux flow through the second pole while limiting flux flow through the first pole, thereby preventing saturation in the second pole. 
   In still another embodiment of the invention, the high magnetic moment layer  98  of the second pole  76  can be constructed of laminated FeXN nanocrystalline films with lamination layers of cobalt based amorphous ferro-magnetic alloy or alternatively of a non-magnetic dielectric material, while the pedestal is constructed of some other material such as a Ni—Fe alloy that can be electro-plated. Alternatively, the pedestal can be constructed of FeXN nanocrystalline films with lamination layers of a cobalt based amorphous ferromagnetic alloy or of a non-magnetic dielectric material, while the high magnetic moment layer of the second pole is some other plated high magnetic moment material such as NiFe55. 
   With reference now to  FIG. 4 , a process  400  is provided for constructing a write element of the present invention. The process begins with a step  402  of constructing the first pole  74 . The first pole is preferably constructed by patterning and electroplating permalloy according to lithographic techniques familiar to those skilled in the art, and then is planarized by a chemical mechanical polishing process. Then, in a step  404  a layer of high magnetic moment (high B sat ) material is sputter deposited onto the first pole. This sputtering process results in a layer of high B sat  material that completely covers the first pole as well as surrounding structure. Thereafter, in a step  406  the pedestal is patterned. A layer of photoresist is deposited so as to form a mask covering the area where the pedestal is to be formed. Then, in step  408 , ion milling is performed to the sputtered high B sat  material not covered by the photoresist mask, thus forming the pedestal  92 . The ion milling step leaves a tail of sputtered material tapering from the edge of the pedestal  92 . 
   With further reference to  FIG. 4 , in a step  410  a first insulation layer  94  is deposited onto the first pole. This first insulation layer  94  is preferably constructed of Al 2 O 3  and is deposited sufficiently thick to at least reach the thickness of the pedestal  92  and is preferably slightly thicker than the pedestal  92 . Thereafter, in a step  412  a chemical mechanical polishing step is performed to planarize the first insulation layer  94 , generating a flat planar surface across the first insulation layer  94  and the top of the pedestal  92 . In a step  414  the write gap material layer  89  is deposited onto the smooth planar surface of the first insulation layer  94  and the pedestal  92 . The write gap material layer can be constructed of many suitable dielectric substances, but is preferably constructed of Al 2 O 3  or alternatively of SiO 2 . 
   In a step  416 , the electrically conductive coil  90  is formed. The coil is preferably constructed of copper and is formed by methods that are familiar to those skilled in the art. These methods involve first depositing a seed layer of copper or some other suitable conductive material. The coil is then patterned and electroplated, and the seed layer removed by an etching process. With the coil thus formed, in a step  418  the second insulation layer  96  is formed. The second insulation layer is preferably constructed of a photoresist, which is spun onto the write gap material  89  and the coil  90 . The photoresist is patterned and exposed so that selective portions of the photoresist can be removed to provide vias for the back gap and the coil leads. Then the photorsist photoresist is cured by exposure to high temperatures, hardening the photoresist and providing it with smoothly rounded edges. In order to improve properties of the sputtered layer, a thin layer of dielectric material can be added to the top of the photoresist material. 
   With reference still to  FIG. 4 , the formation of the second pole will now be described. In a step  420 , a thin layer of high B sat  material is sputter deposited onto the structure. As will be appreciated by those skilled in the art, sputter deposition will cover the entire exposed structure, including the second insulation layer  96  and the write gap material layer  89 . The high B sat  material is preferably constructed of FeRhN nanocrystalline films with lamination layers of CoZrCr, however other high B sat  at materials can also be used. Then, in a step  422  the remainder of the second pole  76  is deposited. This step involves forming a mask and then electroplating the second pole. Using such standard electroplating and photolithographic processes, the electroplated portion of the second pole  76  can be formed with the desired shape. The electroplated portion of the first pole is preferably constructed of a NiFe alloy suitable for electroplating. With the electroplated portion of the second pole acting as a mask, in a step  424  an etching process is conducted to remove the high B sat  material that is not covered by the plated portion of the second pole  76 . This effectively results in a desired second pole  76  being primarily constructed of a magnetic material such as permalloy, and having a high B sat  inner layer. The resulting pole structure includes a tail (not shown) of high B sat  material that extends outward slightly from the edge of the pole  76 , beyond the edge of the plated portion. Also, as previously discussed the ion milling step leaves some of the sputtered material re-deposited on the sidewalls of the second pole  76 . 
   With continued reference to  FIG. 4 , in a step  426 , the pole tip of the second pole  76  is masked with photoresist. Then, in a step  428  the structure is again ion milled to remove material from the uncovered side portions of the tip of the second pole  76 . Thereafter, in a step  430  an etching process is performed to remove write gap material in the pole tip region at the sides of the second pole  76 . Then, with the write gap material locally removed, in a step  432 , yet another ion mill is performed to remove material from the corners of the pedestal  92  leaving notches  102  in the pedestal  92 , which can be more clearly seen with reference to  FIG. 5 , which shows an ABS view of the resulting pole trimmed pedestal. The notches  102  in the pedestal prevent magnetic flux from flowing through the sides of the yoke, thereby preventing side writing. 
   As will be appreciated by those skilled in the art, the above process can be slightly modified to construct one of the earlier described alternate embodiments of the invention. For example, the write element  70  could be constructed without the pedestal by patterning the first insulation layer to terminate short of the ABS plane  86  and eliminating the pedestal deposition process. In such a case the write gap material layer would simply slope down along the edge of the first insulation layer, and would sit atop the first pole  74  in the region of the write gap. Alternatively, the write element  70  could be constructed with a pedestal  92  as described above, but with a second pole formed without a laminated high B sat  layer. Furthermore, high B sat  layer of the second pole can be constructed of FeRhN nanocrystalline films with lamination layers of CoZrCr while the pedestal is constructed of some other magnetic material. Similarly, the pedestal can be constructed of FeRhN nanocrystalline films with lamination layers of CoZrCr while the high B sat  layer of the second pole is constructed of plated high B sat  material such as NiFe55. 
   With reference now to  FIG. 5 , in an alternate embodiment of the invention, the pedestal can be constructed very thin with a tapered edge. Making the pedestal thin advantageously simplifies the manufacturing process, and the tapered edge promotes flux flow into the pedestal, avoiding magnetic saturation in the pedestal. A method for constructing a write element having such pedestal is described in U.S. patent application Ser. No. 09/602,536, titled “INDUCTIVE WRITE HEAD INCORPORATING A THIN HIGH MOMENT PEDESTAL”, filed on 23 Jun. 2000, the entirety of which is incorporated herein by reference. 
   While the present invention has been particularly shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit, scope and teaching of the invention. Accordingly, the disclosed invention is to be considered merely as illustrative and limited in scope only as specified in the appended claims.