Abstract:
A transducer carrying structure includes a first portion carrying the transducer, a second portion spaced from the transducer, and a spacing control actuation system operable to adjust a position of the first portion of the transducer carrying structure. An overcoat is provided on a surface of the transducer carrying structure. The overcoat has a first thickness in the first region of the transducer carrying structure and a second thickness in the second region of the transducer carrying structure, the second thickness being greater than the first thickness. This configuration provides increased wear robustness to the transducer carrying structure without causing the transducer to be excessively spaced from a medium during operation of the transducer.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/747,653 filed May 18, 2006 for “Dual Thickness Carbon Overcoat” by R. Martin. 
     
     INCORPORATION BY REFERENCE 
       [0002]    The aforementioned U.S. Provisional Application No. 60/747,653 is hereby incorporated by reference in its entirety. 
       BACKGROUND 
       [0003]    The present invention relates to a dual thickness carbon overcoat structure for protecting the medium-confronting surface of a transducer carrying structure, in which the overcoat has a first thickness in a region of the structure where the transducer is carried, and has a second thickness greater than the first thickness in other regions of the structure. 
         [0004]    In disc drives and other transducing systems, a transducer is carried by a structure adjacent to a storage medium. Over time, operation of the system can cause wear of the surface of the structure that confronts the storage medium, which is undesirable for a number of reasons. In order to protect the structure against wear, an overcoat (formed with a relatively thin layer of material such as carbon) is provided on the surface of the structure confronting the storage medium. 
         [0005]    Traditionally, increases in wear robustness have been achieved by increasing the overcoat thickness everywhere on the medium-confronting surface of the transducer carrying structure, including the region of the structure that carries the transducer. However, this improvement in wear robustness comes at the expense of increased spacing between the transducer and the medium due to the thicker protective layer, which is undesirable in many applications. 
         [0006]    It would be useful in the art to provide additional protection against wear without increasing the spacing between the transducer and the medium. 
       SUMMARY 
       [0007]    In accordance with the present invention, a transducer carrying structure includes a first portion carrying the transducer, a second portion spaced from the transducer, and a spacing control actuation system operable to adjust a position of the first portion of the transducer carrying structure. An overcoat is provided on a surface of the transducer carrying structure. The overcoat has a first thickness in the first region of the transducer carrying structure and a second thickness in the second region of the transducer carrying structure, the second thickness being greater than the first thickness. This configuration provides increased wear robustness to the transducer carrying structure without causing the transducer to be excessively spaced from a medium during operation of the transducer. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a diagram illustrating a transducer carrying structure having a transducer spaced from a medium by a height Hf. 
           [0009]      FIG. 2A  is a bottom view of a transducer carrying structure according to an embodiment of the present invention. 
           [0010]      FIG. 2B  is an enlarged bottom view of the transducer carrying portion of the transducer carrying structure shown in  FIG. 2A . 
           [0011]      FIG. 3A  is a further enlarged bottom view of the transducer carrying portion of the transducer carrying structure shown in  FIGS. 2A and 2B . 
           [0012]      FIG. 3B  is a graph illustrating the contours of the bottom of the transducer carrying structure and overcoat shown in  FIG. 3A . 
           [0013]      FIG. 4  is a graph showing the contours of the bottom of the transducer carrying structure and overcoat when the transducer carrying structure is supported adjacent to a medium in an operating state with a pitch of 120 microradians (μtrads) and with no spacing control adjustment. 
           [0014]      FIG. 5  is a graph showing the contours of the bottom of the transducer carrying structure and overcoat when the transducer carrying structure is supported adjacent to a medium in an operating state with a pitch of 120 μtrads and a thermally actuated protrusion to provide a peak spacing control adjustment. 
           [0015]      FIG. 6  is a graph showing the contour of the thermally actuated protrusion provided in the spacing control adjustment of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  is a diagram illustrating transducer carrying structure  10  having transducer  12  spaced from medium  14  by a height Hf. In systems employing transducer  12  for transducing data with medium  14 , it is often desirable for the transducer-to-medium spacing Hf to be as small as possible. In many of these same systems, it is also desirable for the bottom surface of transducer carrying structure  10  to be protected against wear and contamination. This protection is provided by overcoat  16 . In some systems, overcoat  16  is a carbon overcoat (COC) having a thickness of about 2 nanometers (nm). 
         [0017]    In order to configure the system shown in  FIG. 1  to have additional protection against wear, the thickness of overcoat  16  can be increased. However, this increase in thickness uses up the budget of available space between transducer  12  and medium  14 , and thus often requires the transducer-to-medium spacing Hf to be increased as well (which is often undesirable) to ensure that contact between overcoat  16  and medium  14  near transducer  12  does not occur. 
         [0018]      FIG. 2A  is a bottom view of transducer carrying structure  20  according to an embodiment of the present invention, and  FIG. 2B  is an enlarged bottom view of the transducer carrying portion of transducer carrying structure  20 . Transducer carrying structure  20  is shown as including a number of geometric features on its bottom surface, which may vary for different embodiments. Transducer carrying structure  20  carries transducer  22  at one end of the structure. The portions of transducer carrying structure  20  shown in sparse right-to-left downward sloping hash lines are located on a bottom surface of the structure, and are coated with an increased thickness of overcoat (such as a dual layer thickness). The portions of transducer carrying structure  20  shown in dense left-to-right downward sloping hash lines are also located on a bottom surface of the structure, and are coated with a regular thickness of overcoat (such as a single layer thickness). The portions of transducer carrying structure  20  shown in sparse left-to-right downward sloping hash lines are recessed and filled around transducer  22 , and also are coated with a regular thickness of overcoat (such as a single layer thickness). The result of the overcoat thicknesses applied to transducer carrying structure  20  is to provide a thicker overcoat thickness in the portion of transducer carrying structure that is spaced from transducer  22  than in the portion of the transducer carrying structure that carries transducer  22 . 
         [0019]    Any effect on the spacing between transducer  22  and a confronting medium due to the increased thickness of overcoat is mitigated by a spacing control actuation system provided for transducer carrying structure  20 . Many types of actuation systems are known in the art for providing this ability, such as thermal protrusion actuation systems in which a heater is provided to cause portions of the transducer carrying structure to expand and adjust the position of the transducer with respect to the medium, piezoelectric actuation systems in which deformation of a piezoelectric material is used to adjust the position of the transducer with respect to the medium, and others. The portion of transducer carrying structure  20  that is positionable by the spacing control actuation system (i.e., the transducer-carrying portion) has a smaller overcoat thickness than the portion of transducer carrying structure that is spaced from transducer  22  (i.e., the non-transducer-carrying portion), so that the transducer-to-medium spacing is not adversely affected by the increased overcoat thickness applied to transducer carrying structure  20 . 
         [0020]      FIG. 3A  is a further enlarged bottom view of the transducer carrying portion of transducer carrying structure  20 , and  FIG. 3B  is a graph illustrating the contours of the bottom of transducer carrying structure  20  and overcoat  24 . Transducer carrying structure  20  includes reader element  30 , writer element  32 , and feature  34 . The overcoat on the bottom surface of transducer carrying structure  20  transitions from a larger thickness to a smaller thickness at the location referred to by reference numeral  36 . The recessed area around reader element  30 , writer element  32  and feature  34  is shown by the increased surface height level shown in  FIG. 3B  and referred to by reference numeral  38 . 
         [0021]    The contours of the bottom of the transducer carrying structure are illustrated and explained in more detail below by Comparative Example A (utilizing regions of different overcoat thicknesses without spacing control actuation) and Example B (utilizing regions of different overcoat thicknesses with spacing control actuation). 
       EXAMPLES 
     Comparative Example A  
       [0022]      FIG. 4  is a graph showing the contours of the bottom of transducer carrying structure  40  and overcoat  44  when transducer carrying structure  40  is supported adjacent to medium  46  in an operating state with a pitch of 120 microradians (μrads). Transducer carrying structure  40  is shown without any spacing control actuation to bring write element  42  nearer to the surface of medium  46 . In this configuration, overcoat  44  has a thickness of about 4 nanometers (nm) in region  48  spaced from the transducer (i.e., write element  42 ), and has a thickness of about 2 nm in region  50  adjacent the transducer (i.e., write element  42 ), although these thickness values can vary between embodiments. The transition from the larger thickness of overcoat  44  to the smaller thickness of overcoat  44  is located at point  52 , which is about 18 μm from the point at which transducer carrying structure  40  transitions from alumina/titanium carbide composite (AlTiC) to alumina. The point of lowest separation from medium  46  in this example is 11.692 Angstroms (Å) (at feature  49 ), while the point at which the thickness of overcoat  44  transitions from the larger thickness to the smaller thickness is separated from medium  46  by 13.16 Å. In some applications, it is desirable for the difference in separations at these two points to be larger than this. 
       Example B 
       [0023]      FIG. 5  is a graph showing the contours of the bottom of transducer carrying structure  60  and overcoat  64  when transducer carrying structure  60  is supported adjacent to medium  66  in an operating state with a pitch of 120 μrads and a thermally actuated protrusion to provide a peak spacing control adjustment of about 8 nm (the complete shape of the thermal protrusion is shown in  FIG. 6 ). In this configuration, as with the configuration of Comparative Example A, overcoat  64  has a thickness of about 4 nm in region  68  spaced from the transducer (i.e., write element  62 ), and has a thickness of about 2 nm in region  70  adjacent the transducer (i.e., write element  62 ), although these thickness values can vary between embodiments. The transition from the larger thickness of overcoat  64  to the smaller thickness of overcoat  64  is located at point  72 , which is about 18 μm from the point at which transducer carrying structure  60  transitions from AlTiC to alumina. With actuation (via thermal protrusion) of the spacing control system, the point of lowest separation from medium  66  is 11.928 Å (at feature  69 ), while the point at which the thickness of overcoat  64  transitions from the larger thickness to the smaller thickness is separated from medium  66  by 18.357 Å. The thermally actuated protrusion therefore makes the difference in separations between these two points larger than for a non-actuated system, such as by at least about 4 Angstroms in some embodiments (although larger and smaller amounts of change are achievable as well). 
         [0024]    The dual thickness overcoat configuration described above is readily achievable by adding an additional photo step during overcoat deposition. For example, a thin layer of overcoat may be deposited over the entire surface of the transducer carrying structure, corresponding to the final thickness of the overcoat in the transducer carrying portion of the transducer carrying structure. In an exemplary embodiment, the thickness of this layer is about 2 nm. The transducer carrying portion of the transducer carrying structure is then masked, and an additional layer of overcoat is deposited on the unmasked area. In an exemplary embodiment, the thickness of this additional layer is about 2-4 nm, although even thicker layers could be used in some systems. The mask is then removed, leaving the transducer carrying portion of the transducer carrying structure with a thinner layer of overcoat and the remaining portion of the transducer carrying structure with a thicker layer of overcoat. This increased overcoat thickness provides improved wear robustness to the transducer carrying structure while not increasing the transducer-to-medium spacing of the system due to the thinner layer of overcoat in the transducer carrying portion of the transducer carrying structure and the spacing control actuation system that is employed. 
         [0025]    It should be understood that while the illustrations provided in the drawings that accompany this description depict the transducer carrying structure as a slider employable in a disc drive, the present invention is applicable to any transducer carrying structure and system for transducing data with a medium. 
         [0026]    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.