Abstract:
A head structure for writing data on a magnetic media including a first pole having an upper surface and a write gap covering a portion of the upper surface. An upper pole tip formed on the write gap having a first width. A second pole having a second width greater than the first width and coupling to an upper surface of the upper pole tip. A conductive coil magnetically coupled to the first pole and the second pole to induce magnetic flux within the first and second pole in response to a current flowing in the coil.

Description:
FIELD OF THE INVENTION 
     The present application is a divisional application of U.S. patent application Ser. No. 08/984,926, filed Dec. 4, 1997, and issued Aug. 22, 2000 as U.S. Pat. No. 6,105,238. 
    
    
     BACKGROUND OF THE INVENTION 
     Relevant Background 
     The desktop personal computer market continues to demand higher capacity and faster performance from hard disk and tape drives. With applications such as file downloading, increased file sizes, advanced operating systems, and multimedia applications, demand for hard disk drive capacity, for example, is doubling every year. Technologies for storing and retrieving data from magnetic media must also be cost effective. Because lower cost per megabyte (MB) is also desired, the prior practice of simply adding more disks and “heads” (i.e., structure in which read and write elements are provided) to a hard drive is less and less effective. Disk and tape drive suppliers continue to increase areal densities, or the number of data bits per square inch, to meet the increasing demand for storage at competitive pricing. Read and write head design are key technologies needed to achieve these capacity increases. 
     The write element that writes data on the disk is typically made up of two poles that are separated by a write gap, and which generate a magnetic field when they are excited by a coil magnetically coupled to the poles. When the write element is in proximity to the disk, a magnetic field generated by the poles sets the magnetic orientation in given locations on the disk. In this manner, data is written on the disk. 
     The read element that reads data from the disk is sandwiched between two shields. During a read operation the read element flies in proximity to the disk so that the read element senses the magnetic orientation of the given disk locations. To enable the read element to focus on a small disk location during reading at (i.e. the read element must not be affected by the magnetic orientation of adjoining disk locations), it is desirable to shield the read element. The two relatively large shields filter out the magnetic effects of adjoining disk locations, so that a specific disk location can be focused upon for reading. 
     Hard disk drives with lower areal densities typically use inductive read and write elements. Inductive heads offer low cost and mature processing technology suitable for high volume production. To increase the signal strength from an inductive head, designers have increased the number of turns in the read head as the read signal is directly proportional to the number of turns. Some inductive heads use fifty or more turns in the read/write head. However, increasing the number of turns increases the head&#39;s inductance. There is a limit to the amount of inductance a head can tolerate to effectively perform data write operations. Since thin-film inductive heads use the same inductive element for both reading and writing, the head cannot be optimized for either operation. Moreover, the increased inductance decreases the frequency at which data can be written to and read from the magnetic media. 
     Magnetoresistive (MR) head technology is used to provide higher areal density than possible with inductive heads in both disk and tape drives. MR head structures include an MR element as a magnetic field sensor. A coil is formed above the read head and magnetically coupled to the magnetic yoke that defines the poles of the write element. Although the coil and yoke are magnetically coupled, they are separated by an insulating material to prevent current flow between the coils and the yoke. To provide an area efficient structure, it is desirable to vertically stack the coils in two or more layers. 
     An MR head generally combines the read and write elements of the head into an integrated unit. It does so by eliminating one of the poles of the write element and substituting in its place one of the shields of the read element. In doing so an integrated pole/shield element is created. 
     Using an MR structure as a read element provides high signal output and low noise compared to inductive heads. This higher signal output allows the write element to write data in a much narrower track while still being reliably detected by the MR read element. Separate read and write heads allow each head to be optimized for one particular function (i.e., reading or writing data). With an MR head, the number of wire turns in the write element can be greatly reduced, resulting in a low inductance head enabling high frequency write operations. 
     The track width of an MR head is largely determined by the size of the area of the disk that is affected by the write head. Where the pole/shield structure is physically large, the pole/shield will tend to undesirably affect a larger part of the disk during a write operation, which is a phenomenon referred to as “fringing”. Fringing has an adverse effect on the efficient storage of data on the disk given that it is usually desirable to pack data on the disk as densely as possible, thereby increasing the storage capacity of the disk. 
     The track width can be decreased by making the poles physically small at the write tip (i.e., the portion of the yoke that forms the poles), thereby concentrating the magnetic field into a smaller area. However, in conventional MR head processes, the yoke, including the write tip, are formed as an integrated structure over the coil structure. The coil structure is very thick, especially when vertically stacked coils are used. Hence, the write tip is typically patterned using thick photoresist (on the order using thick photoresist (on the order of 10-15 microns thick) making it difficult to define the small structures that are required to decrease track width. Critical dimension control is poor when patterning thick layers of photoresist resulting in unacceptable variation in the size of the patterned feature. 
     What is needed therefore, is an MR head that combines the advantages of a small write tip structure, but that can be manufactured with a high degree of process control. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the present invention involves a head structure for writing data on a magnetic media including a first, bottom pole having an upper surface and a write gap covering a portion of the upper surface. A first upper pole tip formed on the write gap having a first width. A second upper pole having a second width greater than the first width and coupling to an upper surface of the upper pole tip. A conductive coil magnetically coupled to the first bottom pole, the first upper pole, and the second upper pole to induce magnetic flux within the first bottom, first upper, and second upper pole in response to a current flowing in the coil. 
     In another aspect, the present invention involves a method for making a magnetic head including the steps of forming a first pole piece comprising magnetic material and depositing a gap-forming layer comprising nonmagnetic material over the bottom pole piece. The gap-forming layer is covered with an upper pole tip forming layer comprising a magnetic material. The pole tip forming layer is patterned to define a pole tip having a first width and the gap-forming layer and the first, bottom pole is etched using the pole tip as a mask to form a write gap and to expose a portion of the first pole piece. A planarizing structure is formed on the exposed portion of the first pole piece, the planarizing structure having an upper surface substantially planar with the upper surface of the first pole tip. A conductive coil is formed on the planarizing structure and with a coil insulator. The coil insulator is patterned to define a contact with the upper pole tip. An upper pole comprising a magnetic material is formed covering the coil insulator and contacting the top surface of the pole tip though the contact. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a simplified perspective view of a MR read/write head in accordance with the present invention; 
     FIG. 2 shows an enlarged cross-section view of the read/write head shown in FIG. 1; 
     FIG.  3  and FIG. 4 show orthogonal views of the read/write head illustrated in FIG.  1  and FIG. 2 at a later stage in processing; 
     FIG.  5  and FIG. 6 show orthogonal views of the read/write head in accordance with the present invention at a later stage in processing; 
     FIG.  7  and FIG. 8 show orthogonal views of the read/write head illustrated in FIG.  5  and FIG. 6 at a later stage in processing; 
     FIG.  9  and FIG. 10 show orthogonal views of the read/write head in accordance with the present invention at a still later stage in processing; 
     FIG.  11  and FIG. 12 show orthogonal views of the read/write head in accordance with the present invention at a later stage in processing; and 
     FIG.  13  and FIG. 14 show orthogonal views of the read/write head in accordance with the present invention at near-final stage in processing; 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Magnetoresistive (MR), including giant magnetoresistive (GMR) read/write heads, such as read/write head  100  shown in FIG. 1, are typically mounted on a slider (not shown) that flies in proximity to a surface of a magnetic recording media (not shown) in a hard disk drive. The magnetic recording media is, for example, a metal, ceramic or plastic disk coated with a magnetic thin film. Read/write head  100  comprises a magnetic field sensor  106  to read data and a magnetic field generator to write data on the disk. The magnetic field generator typically includes two poles  107  and  109  that are separated by a “write gap”  110 . A magnetic field is generated when poles  107  and  109  are excited by a current flowing in a coil formed by coil elements  207  and  209  shown in FIG.  2 . When write gap  110  is in proximity to the magnetic media, a magnetic field generated by poles  107  and  109  creates selected magnetic orientations in selected locations on the magnetic media. 
     Magnetic field sensor  106  may comprise a MR element or GMR element positioned between two shield elements  101  and  103 . Shield element  103  serves as both a shield for magnetic field sensor  106  and a pole  107  for the magnetic field generator and is commonly referred to herein as a shared shield/pole element. To aid understanding the present invention is described in terms of specific materials and specific processes. However, unless expressly stated otherwise, equivalent processes may be substituted for the specific examples disclosed herein. In this manner the present invention may be adapted for use with available processing technology and designs without departing from the scope and spirit of the present invention. 
     FIG.  3  through FIG. 14 shows cross section illustrating fabrication steps to form read/write head  100  in accordance with the present invention. 
     The read/write head  100  shown in FIG.  1  and FIG. 2 is formed on a substrate (not shown) that comprises, for example a ceramic base having an upper surface comprising approximately  8  microns of sputter deposited silicon oxide or aluminum oxide (Al 2 O 3 ) or alumina to form the base layer. A specific example of suitable ceramic base material is alumina with titanium carbide. Suitable equivalents for the substrate include silicon, glass, and the like. The upper surface of the substrate is polished using mechanical and/or chemical-mechanical polishing to provide an ultrasmooth surface finish. 
     Shield  101  comprises, for example, a magnetic material such as nickel iron alloy (i.e., permalloy) that is plated to a thickness of two to three microns. The plating can be performed, for example, by electroplating using a conductive seed layer of approximately 1000 angstrom thickness formed by sputtering onto the substrate (not shown). The seed layer comprises nickel iron in the specific example and is patterned by conventional photolithography and etch techniques to define the shape of shield  101 . After the electrodeposition of shield  101 , the photoresist is stripped using available wet or dry photoresist removal techniques. 
     MR element  106  is separated from shield element  106  by a thin separation layer of non-magnetic material  105  such as sputter deposited alumina or other dielectric. Layer  105  is sometimes referred to as a “read gap” layer. Read gap layer  105  can be formed by blanket deposition of from twenty to two thousand angstroms of a non-magnetic high-resistivity metal or dielectric material. 
     MR element  106  comprises a magnetoresistive or giant magnetoresistive film and biasing layer of appropriate thickness. Suitable MR and GMR element designs are known and are described in, for example, U.S. Pat. No. 5,573,809 issued Nov. 12, 1996 and assigned to the assignee of the present application. MR element  106  is typically formed by blanket deposition by ion beam deposition, evaporation or sputtering of appropriate thin film layers of material and subsequent photolithography and patterning. Conductive electrodes (not shown) are provided over MR element  106  using available conductor deposition and patterning techniques. Upper shield layer  103  comprising two to three microns of electroplated permalloy is formed to complete the read head structure. 
     Lower pole  107  is formed on an upper surface of shield  103 . Desirably, lower pole  107  is formed integrally with shield  103  as described in greater detail hereinafter. In a particular example lower pole  107  comprises the same magnetic materials as shield  103 , although it is possible and desirable in some instances to form pole  107  of a material having a improved magnetic properties suited to a particular application. A write gap  110  comprising a high resistivity non-magnetic material separates lower pole tip  107  from upper pole tip  109 . Write gap  110  is formed by sputter deposition of approximately one to one to four thousand angstroms of non-magnetic material such as alumina. In accordance with the present invention, lower pole tip  107  and upper pole tip  109  define a write head of atypically small dimensions. In a particular example, upper pole tip  109  is in the order of 1.0 to 3.0 microns wide. 
     Referring to FIG. 2, a planarizing structure comprising an insulator such as alumina, silicon oxide, silicon nitride, or any available non-organic dielectric, or the like is formed to form first insulator  201  upon which coils  207  are formed. FIG. 2 shows a vertically stacked coil structure comprising a first layer of coils  207  covered by a coil insulator  203 . A second layer of coils  209  are formed on an upper surface of coil insulator  203 , and covered by a second coil insulator  205 . Any number of vertically stacked layers of coils can be formed in this manner. Coil insulator layers  203  and  205  comprise, for example, from 0.5 to 10 microns thick of a suitable crosslinkable polymer such as photoresist. In a specific example, three to four microns of AZ4000 positive photoresist (available from Hoechst Celanese, Inc.) is used to form coil insulating layer  203  and  205 . Other crosslinkable polymer materials, including negative photoresist materials, may be used. Coil insulators  203  and  205  are formed using a cure process that substantially completely crosslinks the crosslinkable polymer content and desirably drives out substantially all of the solvents. 
     One feature of the present invention is that the stacked coil structure shown in FIG. 2 can be formed after upper pole tip  109  and lower pole tip  107 . This enables upper pole tip  109  and lower pole tip  107  to be formed on a planar surface and patterned using comparatively thin photoresist. The thin photoresist process provides greater process control and enables definition of fine geometry features in the micron and submicron range. Upper pole tip  109  is contacted by upper pole  111  that comprises 2-3 microns of a magnetic material such as permalloy applied by, for example, electroplating. Upper pole tip  109  has a vertical height selected to space the lower surface of upper pole  111  away from write gap  110  such that upper pole  111  does not create fringing fields of sufficient magnitude to write or erase data on the magnetic media (not shown). 
     FIG. 3 illustrates a view of the present invention from the disk/media surface. FIG. 4 shows cross-sectional views illustrating a process to manufacture the write portion of the read/write head in accordance with the present invention. FIG.  3  and FIG. 4 show the structure in accordance with the present invention at a stage in which the read portion is substantially complete. In accordance with the present invention, upper shield/pole layer  103  is covered by write gap layer  110  using a blanket deposition process. Write gap layer  110  is subsequently covered by a blanket deposition of magnetic material to a thickness in the range of 1.0 to 4.0 microns and about 2.5 microns in a specific example to form upper write tip  109 . The thickness of upper write tip  109  is desirably at least three times the thickness of write gap  110  so provide adequate separation of upper pole  111  (shown in FIG. 1) from write gape  110 . This vertical separation separates pole  111  and particularly the high magnetic fields that form at the corner formed where upper tip  109  and upper pole  111  adjoin. Without proper vertical separation, these high magnetic fields may cause excessive fringing. 
     A significant advantage in accordance with the present invention is that upper write tip  109  can be formed using magnetic materials that can be applied using thin film deposition techniques. Prior processes deposited the material forming tip  109  simultaneously with upper pole  111  (shown in FIG.  1  and FIG. 2) after formation of coils  207  and  209 . Because of the difficult cross section, the write tip and yoke were formed by electroplating which greatly restricted the types of materials that could be used. In accordance with the present invention, write tip  109  may be formed before the formation of coils  207  and  209  and may use thin film techniques because a nearly planar cross section exists at this stage in processing. Materials with high magnetic moment such as selected nickel-iron alloys, CZT, iron-aluminum-nickel alloys, and the like may be used to form upper write tip  109 . CZT is a soft magnetic film of cobalt, zirconium, and tantalum. Upper pole  111  can be formed separately of a magnetic material of higher resistivity to enable the write element to develop a magnetic field faster. In this manner, pole  111  and upper tip  109  can each use materials specifically chosen to optimize performance of the write element. 
     In FIG.  5  and FIG. 6, upper write tip  109  is patterned and etched using conventional photoresist techniques to align upper tip  109  with respect to with read element  106  in a conventional manner. Using the same mask or using upper tip  109  as a mask, write gap  110  is etched through and a portion of the upper surface of pole/shield  103  is etched to define lower write tip  107 . As illustrated in FIG.  7  and FIG. 8, the etch of write gap  110  and lower write tip  107  is self-aligned to upper write tip  109  in the preferred implementation and does not require additional masking and alignment steps. Alternatively, pole/shield layer  103  may be formed as a multi-layer structure having an upper surface comprising a thin layer of high magnetic moment material. The etch shown in FIG.  7  and FIG. 8 is used to remove this material in all locations except lower write tip  107 . 
     Planarizing structure  201  is formed as shown in FIG.  9  and FIG. 10 by a blanket deposition of a conformal dielectric, non-magnetic material such as alumina, silicon oxide, silicon nitride, or other available non-organic dielectric. The initial deposition must be at least as thick as the height of the write element structure as defined by the difference between the upper surface of shield  103  and the upper surface of write tip  109 . Mechanical or chemical mechanical polishing is used to planarize structure  201  as shown in FIG.  11  and FIG.  12 . An advantage of planarizing structure  201  is that the base of coils  207  is lower with respect to write gap  110  than prior designs making the write coil structure easier to cover with subsequent material deposition processes. 
     Upper pole  111  shown in FIG. 13 is formed to magnetically contact upper write tip  109  after the formation of coils  207  and  209  shown in FIG.  2  and FIG.  14 . Upper pole  111  is formed by deposition of a seed layer and electroplating of a magnetic material such as permalloy to a thickness of three to four microns. Coils  207  and  209  comprise a conductive material such as copper, gold, alloys, or the like. In a specific example, coils  207  are formed by providing seed layer (not shown) of copper or chromium-copper having a thickness of about 1000 angstroms on top of planarizing structure  201 . Copper, copper alloy, or a suitable equivalent is electroplated to a thickness of about four microns using a patterned photoresist frame to define coils  207 . The photoresist frame is removed and excess conductive material is removed by available photolithography and etch techniques to remove any undesired conductive paths between adjacent portions of coil  207 . 
     Coils  207  are covered by a first coil insulator  203  (shown in FIG. 2) that comprises, for example, a cured photoresist. A layer of photoresist such as AZ4000 series positive photoresist is applied by spin, spray, or other available resist application techniques to a thickness of about five microns. The thickness chosen to completely fill between adjacent portions of coils  207  and to separate the tops of coils  207  from bottoms of coils  209  (shown in FIG. 2) by a selected amount. Any number of coils  207  and  209  can be accommodated by the process in accordance with the present invention. 
     Referring again to FIG. 13, one advantage in accordance with the present invention is that the lower portion of upper pole  111  need not have critical dimension control as it is sufficiently removed from write gap  110  such that pole  111  will not define the track width of read/write head  100 . 
     This allows upper pole  111  to be patterned and defined using conventional thick photoresist techniques used in the past while achieving the benefits of a small dimension write head. 
     Although the invention has been described and illustrated with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example. For example, the present invention is described in terms of a merged read/write head for a magnetic disk drive, however, the teachings of the present invention can be applied to a magnetic tape drive or other magnetic recording media with minor modification. Numerous changes in the combination and arrangement of parts can be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter claimed.