Abstract:
A method of fabricating a magnetoresistive (MR) proximity head slider having substantial immunity to thermal asperities includes providing the head slider having an inductive write transducer and an MR read transducer each extending to a first region of an air bearing surface (ABS) of the head slider. The method further includes removing a portion of the first region of the ABS corresponding to the MR read transducer to form a cavity in the ABS. The cavity in the ABS provides a second region of the ABS such that after removal of the portion of the first region the MR read transducer extends only to the second region of the ABS.

Description:
This is a division of application No. 08/962,759, filed on Nov. 3, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to data storage system head sliders. More particularly, the present invention relates to a magnetoresistive (MR) proximity head slider having a recessed MR element (MRE) to minimize thermal asperities in the read back signal. 
     In magnetic disc drive data storage devices, digital data are written to and read from a thin layer of magnetizable material on a surface of one or more rotating discs. Write and read operations are performed through write and read transducers which are carried in a slider body. The slider and transducers are sometimes collectively referred to as a head, and typically a single head is associated with each disc surface. When the read transducer is a magnetoresistive (MR) type sensor, the combination of the slider and the transducer are frequently referred to as an MR head. The heads are selectively moved under the control of electronic circuitry to any one of a plurality of circular, concentric data tracks on the disc surface by an actuator device. Each slider body includes an air bearing surface (ABS). As the disc rotates, the disc drags air beneath the ABS, which develops a lifting force that causes the head to lift and fly above the disc surface. 
     In operation, the MRE of the head can come into contact with asperities on the surface of the disc. This is particularly true in proximity type heads where the inductive write transducer comes into frequent contact with the glide avalanche of the media. Potentially, this contact between the MRE and asperities can cause data written to a particular location on the disc to be lost. Immediately after contact with an asperity, the heat generated by the contact changes the resistive properties of the MR sensor. As a result, the corresponding signal read by the MR head is distorted by a voltage spike and subsequent decay, sometimes causing the data stored near the asperity to be unrecoverable. The voltage spike in the read back signal is frequently referred to as a “thermal asperity,” while the defect on the disc is referred to as an “asperity”. However, since one is indicative of the other, the two terms are frequently used interchangeably. Since a large number of thermal asperities appear in the read back signal from contact with the glide avalanche of the media, the concept of MR proximity which involves direct contact of the MRE with the media is not feasible with the existing MRE sensitivity to thermal asperities. 
     SUMMARY OF THE INVENTION 
     A proximity magnetoresistive head slider and method of making the same are disclosed. The head slider includes a slider body having an air bearing surface (ABS). An inductive write transducer is formed at a first portion of the ABS. A cavity is formed in the slider body such that a first surface of the cavity forms a second portion of the ABS which is out of plane with the first portion of the ABS. A magnetoresistive (MR) read transducer is positioned in the cavity at the first surface such that the MR read transducer is recessed relative to the inductive write transducer, thereby preventing contact between the MR read transducer and a surface of a disc. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic side view of a portion of a head slider in accordance with preferred embodiments of the present invention. 
     FIG. 2 is a diagrammatic upside-down side view of the portion of the head slider illustrated in FIG. 1 which shows features of the present invention in greater detail. 
     FIG. 3 is a diagrammatic upside-down side view illustrating a first read and write transducer configuration of a head slider which can be provided as a first step in a method of fabricating the head sliders of the present invention. 
     FIG. 4 is a diagrammatic upside-down side view illustrating a second read and write transducer configuration of a head slider which can be provided as a first step in a method of fabricating the head sliders of the present invention. 
     FIG. 5 is a diagrammatic upside-down side view illustrating a second step in the method of fabricating the head sliders of the present invention. 
     FIG. 6 is a diagrammatic upside-down side view illustrating a third step in the method of fabricating the head sliders of the present invention. 
     FIG. 7 is a diagrammatic upside-down side view illustrating a fourth step in the method of fabricating the head sliders of the present invention. 
     FIG. 8 is a diagrammatic upside-down side view illustrating an optional step in the method of fabricating the head sliders of the present invention. 
     FIG. 9 is a diagrammatic upside-down side view illustrating an optional step in the method of fabricating the head sliders of the present invention which follows the step illustrated in FIG.  8 . 
     FIGS. 10 and 11 are diagrammatic ABS and side views illustrating one feature of some embodiments of the present invention. 
     FIG. 12 is a diagrammatic upside-down side view of an alternate embodiment of the head sliders of the present invention in which the cavity formed in the ABS is limited in width to the MRE and portions of the electrical conductors. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is based in part upon the recognition that with MR head advancements, the MRE can be designed to remain clear of the disc without substantial impact on electrical performance and on the flying regime. At the same time, the inductive write element can be designed to be in contact with the glide avalanche of the disc to overcome future low inductance and high disc coercivities required for high areal density and data rate applications. According to the present invention, the MRE region is recessed to avoid contact of the MRE with the media glide avalanche throughout the life of the head slider and to allow the inductive element to be in contact with the media. Advances in MRE design and materials (i.e., such as soft sendust SAL, hot MRE deposition, and spin valve designs) and/or the net reduction in head-media spacing from using a proximity advanced air bearing (AAB) provide a sufficient boost in amplitude to overcome spacing loss from the MRE recession. In the head sliders of the present invention, the inductive transducer will be in contact with the media and will ultimately be burnished, thereby reducing the initial MRE separation. 
     FIG. 1 is a diagrammatic illustration of a portion of head slider  100 , flying over glass disc  104  at pitch angle θ and in contact with the media glide avalanche  102 , in accordance with preferred embodiments of the present invention. Head slider  100  includes ABS  110  and trailing edge face  120 . In some preferred embodiments, ABS  110  lies in at least three planes arranged to form a cavity or recessed area  180  in which MRE  160  (i.e., the MR sensor or transducer) is positioned to prevent contact between the MRE and glide avalanche  102  of the media. However, in other embodiments the ABS lies in at least two planes arranged to form the cavity. As illustrated in FIG. 1, ABS  110  includes first portion  130 , second portion  140  and third portion  150 . In addition to ABS portion  140 , recess or cavity  180  also includes sides or walls  190  and  200 , which in preferred embodiments, can be oriented substantially perpendicular to one or more of surfaces  130 ,  140  and  150 . Cavity wall  190  and portion  130  of ABS  110  form corner  210 . The distance between corner  210  and glass disc  104  is designated H SPOT . With inductive write transducer  170  formed on portion  150  of ABS  110 , write transducer  170  can be in contact with glide avalanche  102  without causing contact between glide avalanche  102  and MRE  160 . 
     FIG. 2 is a diagrammatic upside-down side view of portions of head slider  100  illustrated in FIG.  1 . FIG. 2 illustrates various dimensions of head slider  100 , some of which are used below in Equation 1. To insure that the MRE  160  will not be in contact with the media glide avalanche  102 , the MRE  160  conditional separation (first order model) shown below in Equation 1 can be used during the design of head slider  100 . 
      (H SPOT −3σ)+(H ALR +H MRE )−d MRE *pitch&gt;GHA  Equation 1 
     where: 
     H SPOT  is the height of corner  210  above disc  104 ; 
     H ALR  is the vertical distance or amount of recession of portion  150  of ABS  110  relative to portion  130  of ABS  110 ; 
     H ARE  is the vertical distance or amount of recession of portion  140  of ABS  110  relative to portion  150  of ABS  110 ; 
     d MRE  is the distance between MRE  160  and wall  190  of cavity  180 ; 
     Pitch is the sine of the angle θ at which head slider  100  flies above disc  104 , and since angle θ is small can be approximated as angle θ; and 
     GHA is the media glide height avalanche. 
     A primary benefit of head slider  100  of the present invention is that MRE contact with the media is avoided in proximity applications. A simplified analysis can be used to demonstrate that the concept of the present invention, of avoiding MRE contact with the media throughout the life of the product, is feasible for existing ABS designs. For one specific advanced air bearing (AAB) design with a media having a GHA of 0.7 microinch, the condition of Equation 1 to be satisfied in order to insure that no contact of the MRE with the alumina will occur is H MRE +H ALR &gt;0.3 microinch. This condition can be satisfied for a standard ALR process of 0.2 microinch and for an MRE recession H MRE . (relative to inductive writer  170 ) of greater than 0.1 microinch Holding this concept to be true, even at 10,000 feet where an MRE recession H MRE +H ALR  of greater than 0.45 microinch (0.1+0.35) is needed to compensate for fly height loss due to altitude, the desired MRE recession of between 0.4 and 0.5 microinch is reasonable and acceptable. 
     The electrical performance of MRE  160  is expected to improve over time due to the inductive poles of write transducer  170  wearing and the distance between MRE  160  and the media being reduced. Thus, the final recession of MRE  160  relative to portion  130  of ABS  110  may be considerably less than 0.4 or 0.5 microinches, depending on the AAB design and choice of media. In preferred embodiments, H MRE  is at least about 0.05 microinch. In preferred embodiments in which the portions of the ABS forming the cavity lie within at least three planes (i.e., embodiments in which H ALR  does not equal zero), H ALRE +H MRE  is preferably at least about 0.1 microinch. 
     FIGS. 3 and 4 depict two typical MR head slider configurations, in which the MR read element and inductive write element either share a common pole (called a shared pole) or have separate poles separated by an insulating layer, which can be used to create head slider  100  of the present invention. Thus, providing one of head sliders  300  or  400  illustrated in FIGS. 3 or  4  can be the first step in a method of fabricating head slider  100  of the present invention. However, it should be noted that head sliders having configurations other than those of head sliders  300  and  400  can be provided as the first step in producing head slider  100  of the present invention as well. 
     In head slider  300  illustrated in FIG. 3, the MRE read transducer includes MRE  160  surrounded by shield  161 , soft adjacent layer (SAL)  162 , insulating gap layer  163 , insulating gap layer  165  and shield  166  Write transducer  170  includes inductive coils  171 , bottom pole  172  and top pole  173 . Shield  166  and bottom pole  172  are separated by insulating layer  167 . Prior to alteration of head slider  300  to produce head slider  100 , MRE  160  and write transducer  170  each terminate at or extend to portion or surface  150  of the ABS. Head slider  400  illustrated in FIG. 4 differs from head slider  300  only in that shield  166  and insulating layer  167  have been eliminated. In this case, pole  172  is a common or shared pole of both the MR read transducer and the inductive write transducer. For ease of illustration, the remaining steps in the method of fabricating head slider  100  of the present invention are illustrated with reference to head slider  300  shown in FIG.  3 . 
     FIG. 5 illustrates the next step in the preferred method of fabricating head slider  100  of the present invention. As shown in FIG. 5, MRE region  260  is masked such that adjacent regions of the ABS other than MRE region  260  are covered with photoresist  250 . MRE region  260 , which will correspond to cavity  180  illustrated in FIGS. 1 and 2, may include the shared pole or insulating layer. 
     Next, as illustrated in FIG. 6, MRE region  260  is exposed to ion milling or other dry etch processes, such as sputter etching or focused ion beam etching, to create recession or cavity  180 . The bottom of cavity  180  can be portion  140  of ABS  110 . The depth of cavity  180  can be controlled such that the requirements of Equation 1 are satisfied. Cavity  180  includes sides or walls  190  and  200 . 
     As illustrated in FIG. 7, the next step in the preferred method of fabricating head slider  100  of the present invention is to remove photoresist  250  from the ABS surfaces of the slider body. This leaves head slider  100  with MRE  160  recessed within cavity  180  and write transducer  170  extending to portion  150  of the ABS. Optionally, as illustrated in FIG. 8, prior to removal of photoresist  250 , diamond like carbon (DLC) or other corrosion resistant material  280  can be deposited in cavity  180  and on other portions of the ABS. Subsequently, as illustrated in FIG. 9, photoresist  250  can then be removed to remove portions of material  280  which had been deposited outside of cavity  180 . This leaves cavity  180  partially filled with material  280  in order to protect the MRE and/or to minimize the effect of cavity  180  on the flying performance of head slider  100 . In the alternative, photoresist  250  can be removed prior to deposition of material  280  on the ABS of head slider  100 . In this instance, the corrosion resistant material will remain on the entire ABS, including portions outside of cavity  180 . 
     As illustrated in FIGS. 10 and 11, etching can be performed along the width of MRE  160  in a manner which will reduce or minimize the amount of debris which will collected in the cavity. As illustrated in FIGS. 10 and 11, if desired etching area  510  can be etched to produce cut angle  520  designed to reduce the debris in the cavity. 
     FIG. 12 illustrates an embodiment of head slider  100  in which cavity  180  is narrower, only encompassing MRE  160  and all or portions of insulating gap layers  163  and  165 . While the embodiments of the present invention illustrated in the previous FIGS. can be created using a photo process, the narrow cavity illustrated in FIG. 12 is preferably created using a laser beam or focused ion beam process. FIG. 12 also illustrates another feature of the present invention which can be optionally utilized in any embodiment. Since MRE  160  is protected within cavity  180 , the conventional recess distance H ALR  between ABS portions  130  and  150  can be eliminated. Thus, the distance H ALR  can be set to zero and portions  130  and  150  on either side of cavity  180  created coplanar with one another. By eliminating the recess distance H ALR , MRE  160  can be recessed within cavity  180  by distance H MRE  and still be closer to the media than in conventional sliders  300  and  400 . 
     Using the method of the present invention of fabricating head slider  100 , if etching of the shared pole between the read and write transducers is not desired due to an impact on magnetic domain configurations or stability, the exposure of the shared pole during dry etching can be corrected by designing two independent shields, one for the writer  170  and one for the reader  160 . Also, the etching rates of different MR materials can be different and will vary with the incident angle of the ion beam. Thus, optimization of the proper combination of etch type, angle and exposure times will likely be MR material dependent. Also, creating an MRE recession or cavity may have some negative impact on the tribological performance of the ABS due to potential smear/debris sites. However, since the contact point is designed to be far away from the MRE, this is not likely to be a problem. Further, dry etching of the MRE may induce unwanted stability issues with the MRE electrical response. However, since some existing products are exposed to extended DLC sputter etching with no signs of increased MRE instability, it is not believed that the etching of the MRE will have a significant negative impact. Further still, it is believed that milling removes residual stresses from the lapping process. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.