Abstract:
A magnetic head cluster is provided along with a method of making a magnetic head cluster. The magnetic head cluster comprises a substrate having a plurality of magnetoresistive (MR) read and inductive magnetic write transducers and a plurality of terminals formed thereon. A plurality of lapping guides are also provided on the substrate between adjacent transducers.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/276,693, filed on Mar. 16, 2001, the entire contents of which are hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a magnetic head cluster for a data storage device having read/write transducers, which are used for communicating with a magnetic recording medium, and lapping guides, which are used during lapping processes while fabricating the magnetic head cluster. Further, the present invention relates to a method for making a magnetic head cluster.  
         BACKGROUND OF THE INVENTION  
         [0003]    Thin film magnetoresistive (MR) read and inductive write transducers are widely used for magnetic heads in data storage devices, such as disk drives and linear tape drives. Various types of MR read heads are known in the art, including anisotropic magnetoresistive (AMR) read heads, giant magnetoresistive (GMR) read heads, and spin valve read heads. In typical magnetic tape read/write heads, multiple merged MR read/inductive write transducers are grouped into a single structure called a magnetic head cluster. Each of the transducers is typically aligned in the cluster along one edge, known as an air bearing surface (ABS) in disk drive technology and known as a tape bearing surface (TBS) for tape drives (for simplicity this surface will be referred to herein as a tape bearing surface), which faces a recording medium during normal read/write operation. In general, each transducer of a cluster provides an unique read/write channel.  
           [0004]    The demand for data storage has been increasing in recent years and this demand has put pressure on fabrication processes for more efficient and cost effective methods and devices. In order to keep up with this demand, attempts to improve various aspects of magnetic head technology include increasing the sensitivity of the magnetic heads, reducing manufacturing costs, and simplifying manufacturing processes.  
           [0005]    A conventional manufacturing process for fabricating a magnetic head cluster will be described next with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, a magnetic head cluster  115  is made by forming a plurality of inner merged MR read/inductive write transducers  100  and outermost merged MR read/inductive write transducers  105 , a plurality of electrical lapping guides  175 , and a plurality of terminals  107  on a single wafer  110 . The wafer  110  can be formed from any material which has high wear resistance, strength, fracture toughness, and good electrical conductivity, such as an alumina titanium-carbide (Al 2 O 3 /TiC) ceramic wafer. The processes used to form the transducers  100  and  105  on the wafer  110  typically include a combination of lithography, deposition (vacuum or plating), and etching steps, all of which are known in the art. The transducers  100  and  105  are grouped into the clusters  115 , which are separated from one another by separation kerfs  120 . As shown in FIG. 1, the clusters  115  are aligned in rows and columns defined by the separation kerfs  120 . Once the process of forming the clusters  115  is complete, the wafer  110  is cut along the separation kerfs  120 , dividing the wafer  110  into a plurality of clusters. This well-known process of cutting the wafer along the kerfs is commonly referred to as “dicing.”  
           [0006]    As mentioned above, the transducers  100  and  105  included in each cluster  115  are typically merged MR read/inductive write transducers. As shown in FIG. 3, a conventional MR read transducer  125  typically includes an MR stripe  130 , which exhibits variations in resistance when exposed to a magnetic field. The stripe height SH of the MR stripe  130  must be controlled within a tight tolerance, such as within a few micro-inches, so that a sensed magnetic signal can generate an optimum change in a resistance of the MR stripe  130 . The inductive write transducer  135  typically comprises various layers of poles  140  and insulating material  145 , and also includes an electrical coil  150 . The region of the inductive write transducer  135  closest to an upper edge  155  (shown on FIG. 2) of the cluster  115 , where the two poles are separated only by a thin insulating layer, is typically called a throat  160 . As will be explained later, the region closest to the upper edge  155  will eventually be lapped to form a tape bearing surface. As is known in the art, the throat height TH must also be controlled within a tight tolerance for the transducer to generate an optimum magnetic signal.  
           [0007]    When the separation kerfs  120  are formed on the wafer  110 , a slight amount of excess substrate is provided along the upper edge  155  of each cluster. The reason for providing this slight amount of excess substrate is that the dicing process is not precise enough to achieve the optimum stripe height SH and throat height TH for each transducer  100  and  105 . So, rather than inadvertently cutting the stripe  130  or throat  160  too short while dicing the wafer  110 , the stripe  130  and throat  160  are intentionally left too long and later are carefully shortened by a process known as lapping.  
           [0008]    [0008]FIG. 4 shows an exaggerated view of the conventional lapping process in order to provide a clear illustration. The broken line in FIG. 4 represents a portion of the cluster  115  which has already been removed by the lapping process. In FIG. 4, a controller  185  operates to activate and halt a lapping plate rotator  190 . The lapping plate rotator  190 , when activated, causes a lapping plate  165  to rotate relative to the cluster  115 , thereby grinding the upper edge  155 . Eventually, a sufficient amount of upper edge  155  is ground away to form a tape bearing surface  170 . The tape bearing surface  170  is a surface of the magnetic head cluster  115  which will face a recording medium (not shown) when the magnetic head cluster  115  is used for read/write operations. A lapping plate pressure applicator  195  also receives signals from the controller  185  for continuously adjusting the amount of pressure being applied to the cluster  115  during the lapping process. The lapping plate pressure applicator  195  may include, for example, one or more dual action air cylinders (not shown) for applying varying amounts of pressure to different points on the cluster  115  in order to provide for skew control. The controller  185  senses an electrical resistance of the electrical lapping guides  175 , which changes as portions of the electrical lapping guides  175  adjoining the upper edge  155  are ground away. The lapping process is complete once the portions of the cluster  115  are removed up to line A, which indicates the desired position of the tape bearing surface  170  of the cluster  115 .  
           [0009]    During the lapping process, the excess portion of the substrate  210  is carefully ground away by introducing an abrasive material, such as a diamond slurry (not shown), between the rotating lapping plate  165  and the upper edge  155  of the fixed cluster  115 . In order to provide for precise control during the lapping process, the electrical lapping guides  175  are typically provided between each outermost transducer  105  and a respective outer edge  180  of each cluster  115 . Once the electrical lapping guides  175  reach a predetermined resistance, the controller  185  halts the motion of the lapping plate  165 . Ideally, the predetermined resistance is selected so that the target stripe height SH and throat height TH are achieved.  
           [0010]    In general, lapping guides and separation kerfs, which are useful during the manufacturing of magnetic head clusters, have no functional purpose during normal operation of a magnetic head cluster. As mentioned above, electrical lapping guides are typically provided between an outermost transducer and an outer edge of each cluster. Thus, the size of each cluster is larger than its functional size, which need only include transducers. Therefore, from a functional standpoint, the wafer space occupied by lapping guides and separation kerfs is wasted. Moreover, in order to minimize the unit cost per cluster, efficient use of wafer space is important. For this reason, recent efforts have been made to increase the efficiency with which wafer space is utilized by reducing the amount of wafer space used for lapping guides and separation kerfs. Accordingly, separation kerfs have been reduced to a very small size so that more clusters can be put onto the same wafer.  
           [0011]    U.S. Pat. No. 6,027,397 discloses further efforts to efficiently utilize wafer space, wherein the cluster size is reduced by putting the lapping guides onto the separation kerfs. U.S. Pat. No. 5,588,199 discloses another attempt to efficiently utilize wafer space, wherein the number of transducers per wafer is increased by adding a resistor network, which is used as a lapping guide, inside the transducers. Therefore, there is no need for a separate electrical lapping guide. A similar approach can be found in U.S. Pat. No. 5,772,493 by using an external magnetic excitation field to the transducer and measuring the resistance of the MR element in response to variations in the applied magnetic excitation field.  
           [0012]    Despite these past attempts to increase the efficiency with which wafer space is utilized, there continues to be a need to improve wafer utilization and simplify manufacturing processes.  
         BRIEF SUMMARY OF THE INVENTION  
         [0013]    In view of the above shortcomings with the prior art, an object of the present invention is to provide a magnetic head cluster that includes lapping guides arranged in such a way so as to reduce cluster size allowing for more clusters per wafer.  
           [0014]    Another object of the present invention is to provide a method of making a magnetic head cluster which allows for a reduced cluster size so that more clusters per wafer may be formed.  
           [0015]    In order to achieve the above objects, a magnetic head cluster is provided that comprises a substrate having a surface with at least two transducer elements disposed thereon and at least one resistive element that is disposed between any two of the at least two transducer elements.  
           [0016]    In accordance with another aspect of the present invention, a method of fabricating a magnetic head cluster having an edge portion is provided that comprises the steps of providing a substrate having a surface, forming at least two transducer elements on the surface, forming at least one resistive element on the surface between any two of the at least two transducer elements, and lapping the edge portion of the magnetic head cluster.  
           [0017]    Depending on the design of the lapping processes, each cluster can contain one or more electrical lapping guides. Such lapping guides can be any combination of analog and/or digital “switch” types that are well-known in the field.  
           [0018]    In accordance with the present invention, the size of electrical lapping guides can be reduced and the electrical lapping guides can be positioned between the transducers so that the size of the magnetic head cluster can be reduced to its functional size. As a result, the total number of clusters that can be produced on a wafer is increased.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    The present invention is illustrated by way of example and not limited in the figures of the accompanying drawings, in which like reference numbers indicate similar parts:  
         [0020]    [0020]FIG. 1 is a plan view of a wafer containing a plurality of conventional magnetic head clusters formed in rows and columns;  
         [0021]    [0021]FIG. 2 is a plan view of a conventional magnetic head cluster;  
         [0022]    [0022]FIG. 3 is a cross sectional view of a magnetoresistive (MR) read and inductive write transducer  100  taken along line III-III of FIG. 2;  
         [0023]    [0023]FIG. 4 is a plan view of a lapping system for a conventional cluster;  
         [0024]    [0024]FIG. 5 is a plan view of a magnetic head cluster in accordance with the present invention; and  
         [0025]    [0025]FIG. 6 is a plan view of a lapping process in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    [0026]FIG. 5 shows a preferred embodiment of the present invention. A magnetic head cluster  315  of the present invention includes a plurality of inner merged MR read/inductive write transducers  300  and outermost merged MR read/inductive write transducers  305 , a plurality of electrical lapping guides  375 , and a plurality of terminals  307  formed on a substrate  410 . The substrate  410  can be a portion of a wafer (not shown) formed from any material which has high wear resistance, strength, fracture toughness, and good electrical conductivity, such as an alumina titanium-carbide (Al 2 O 3 /TiC) ceramic wafer. The transducers  300  and  305 , lapping guides  375 , and terminals  307  can be formed on the substrate  410  by any of the known transducer-forming processes.  
         [0027]    The transducers  300  and  305  are preferably MR read and inductive write transducers as discussed above, and can include any combination of AMR, GMR, and spin valve read heads. The electrical lapping guides  375  may be composed of any type of electrically resistive material, including any combination of analog and/or digital switch types that are well-known in the art. The terminals  307  can be composed of any type of electrically conductive material, such as plated gold, suitable for transferring electrical signals between the transducers  300  and  305  and an external interface (not shown).  
         [0028]    As shown in FIG. 5, the electrical lapping guides  375  are each provided between adjacent inner transducers  300  and/or between adjacent inner transducers  300  and outermost transducers  305 . In other words, in this preferred embodiment, there are no lapping guides  375  provided between an outermost transducer  305  and an adjacent outer edge  380  of the cluster  315 . Compared to the conventional magnetic head cluster  115  shown in FIG. 2, the magnetic head cluster  315  is reduced in size since an excess amount of the substrate  410  is not required to accommodate electrical lapping guides  375  beyond the outermost transducers  305 . Thus, the cluster  315  is reduced to its actual functional size, allowing for more clusters  315  to be formed on a wafer.  
         [0029]    The transducers  300  and  305  included in the cluster  315  are preferably merged inductive write and MR read transducers. The transducers  300  and  305  can have the same configuration as the conventional transducer  100 , which is shown in FIG. 3. As shown in FIG. 3, an MR read transducer  125  includes an MR stripe  130 , which experiences variations in resistance when exposed to a magnetic field. The stripe height SH of the MR stripe  130  must be controlled within a tight tolerance, such as within a few micro-inches, so that a sensed magnetic signal can generate an optimum change in a resistance of the MR stripe  130 . The inductive write transducer  135  comprises various layers of poles  140 , and insulating material  145 , and also includes an electrical coil  150 . The region of the inductive write transducer  135  closest to an upper edge  355  of the cluster  315 , where the two poles are separated only by a thin insulating layer, is typically called a throat  160 . As will be explained later, the region closest to the upper edge  355  will eventually be lapped to form a tape bearing surface. As is known in the art, the throat height TH must also be controlled within a similarly tight tolerance for the transducer to generate an optimum magnetic signal.  
         [0030]    [0030]FIG. 6 shows an exaggerated view of a lapping process in accordance with the present invention in order to provide a clear illustration. The broken line in FIG. 6 represents a portion of the cluster  315  which has already been removed by the lapping process. In FIG. 6, a controller  385  operates to activate and halt a lapping plate rotator  390 . The lapping plate rotator  390 , when activated, causes the lapping plate  365  to rotate relative to the cluster  315 , thereby grinding the upper edge  355 . Eventually, a sufficient amount of upper edge  355  is ground away to form a tape bearing surface  370 . The tape bearing surface  370  is a surface of the magnetic head cluster  315  which will face a recording medium (not shown) when the magnetic head cluster  315  is used for read/write operations. A lapping plate pressure applicator  395  also receives signals from the controller  385  for continuously adjusting the amount of pressure being applied to the cluster  315  during the lapping process. The lapping plate pressure applicator  395  may include, for example, one or more dual action air cylinders (not shown) for applying varying amounts of pressure to different points on the cluster  315  in order to provide for skew control. The controller  385  senses an electrical resistance of the electrical lapping guides  375 , which changes as portions of the electrical lapping guides  375  adjoining the upper edge  355  are lapped away. The lapping process is complete once the portions of the cluster  315  are removed up to line A, which indicates the desired position of a tape bearing surface  370  of the cluster  315 .  
         [0031]    During the lapping process, an excess portion of substrate  410  is carefully ground away from the magnetic head cluster  315  by introducing an abrasive material, such as a diamond slurry (not shown), between a lapping plate  365  and an upper edge  355  of the cluster  315 . In order to provide for precise control during the lapping process, a plurality of electrical lapping guides  375  are provided between selected ones of the plurality of transducers  300  and  305 . Once the electrical lapping guides  375  reach a predetermined resistance, the controller  385  halts the motion of the lapping plate  365 . Ideally, the predetermined resistance is selected so that the target stripe height SH and throat height TH are achieved.  
         [0032]    Although the present invention has been fully described by way of preferred embodiments and methods, one skilled in the art will appreciate that other embodiments and methods are possible without departing from the spirit and scope of the present invention.