Abstract:
A disc head slider is provided for use in a disc drive data storage system. The disc head slider includes a slider body having a slider substrate material with a surface. A transducer is supported by the slider body, and a film is applied to the surface and graphically represents a character pattern.

Description:
CROSS REFERENCE TO A RELATED APPLICATION  
       [0001]    This application is a continuation of U.S. application Ser. No. 08/711,499, which was filed Sep. 10, 1996 and claims priority from U.S. Provisional Application Serial No. 60/023,536, filed Aug. 7, 1996 and entitled “LASER SCRIBING THROUGH A METAL FILM FOR REDUCED CONTAMINATION AND ENHANCED CONTRAST”. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to disc drive data storage systems and, more particularly, to a method of applying a serial number or other information pattern to a surface of a disc head slider.  
           [0003]    Disc drives of the “Winchester type” are well known in the industry. Such drives use rigid discs coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective head gimbal assemblies (HGAs). The HGAs carry transducers which write information to and read information from the disc surface. An actuator mechanism moves the HGAs from track to track across the surface of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a load beam for each HGA. The load beam provides a preload force which presses the HGA toward the disc surface.  
           [0004]    The HGA includes a hydrodynamic (e.g. air) bearing slider and a gimbal. The gimbal is positioned between the slider and the load beam to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc. The slider includes a slider body having a leading edge, a trailing edge and an air bearing surface which faces the disc surface. As the disc rotates, the disc drags air under the slider along the air bearing surface, which creates a hydrodynamic lifting force that causes the slider to lift and fly above the disc surface. The transducer is typically mounted at or near the trailing edge of the slider.  
           [0005]    Air bearing disc head sliders are formed from a substrate known as a wafer. A matrix of transducers is applied to a top surface of the wafer and then the wafer is sliced into a plurality of bars. Each bar includes a plurality of individual slider bodies, with each body having a corresponding transducer. Each bar is then diced into individual slider bodies.  
           [0006]    It is often desired to apply a serial number or some other useful information to each slider body. Serial numbers have been applied to the leading edges of slider bodies by a laser scribing process. During the laser scribing process, a beam of laser light is directed toward the slider substrate material. The beam removes material in a pattern corresponding to the serial number. A disadvantage of the laser scribing process is that the removed material often redeposits on the slider substrate, which creates contamination. Furthermore, the legibility of the applied serial number is occasionally questionable.  
         SUMMARY OF THE INVENTION  
         [0007]    One embodiment of the present invention is directed to a disc head slider for use in a disc drive data storage system. The disc head slider includes a slider body having a slider substrate material with a surface. A transducer is supported by the slider body, and a film is applied to the surface and graphically represents a character pattern.  
           [0008]    Another embodiment of the present invention is directed to a disc head slider, which includes a slider body having a slider substrate material with a surface, a transducer supported by the slider body, and a metal film applied to the surface. An information pattern is defined by the metal film and graphically represents a serial number for the disc head slider.  
           [0009]    Yet another embodiment of the present invention is directed to a disc head slider substrate wafer. The wafer includes an upper surface and a lower surface, which is opposite to the upper surface. A plurality of individual slider body locations are defined within the wafer. A plurality of transducers are fabricated on the upper surface, wherein each transducer is positioned at a corresponding one of the individual slider body locations. A film is applied to the lower surface. A plurality of graphical patterns are defined by the film, wherein each graphical pattern is positioned at a corresponding one of the individual slider body locations and represents a serial number for that slider body location. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of a wafer of slider substrate material from which a slider according the present invention is fabricated.  
         [0011]    [0011]FIG. 2 is a fragmentary perspective view of a bar of slider bodies sliced from the wafer shown in FIG. 1.  
         [0012]    [0012]FIGS. 3 a - 3   c  are end views of a slider body during a slider fabrication process according to the present invention.  
         [0013]    [0013]FIG. 4 is a greatly magnified illustration of a letter which was laser scribed on a metal film according to the present invention.  
         [0014]    [0014]FIG. 5 is a greatly magnified illustration of a letter laser scribed on an uncoated slider substrate according to the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    Hydrodynamic bearing disc head sliders are formed from a substrate known as a wafer. FIG. 1 is a perspective view of typical wafer  10 . Wafer  10  can include aluminum oxide titanium carbide, aluminum silicon magnesium or silicon, for example. Wafer  10  has a top surface  11  and a bottom surface  12 . In a typical fabrication process, a matrix of transducers (not shown) is applied to top surface  11 . Wafer  10  is then sliced along rows  13  into a plurality of bars  14 . Each bar  14  includes a plurality of individual slider bodies, with each body having a corresponding transducer. FIG. 2 is fragmentary, perspective view of a bar of slider bodies sliced from wafer  10 . Each bar  14  includes a plurality of individual slider bodies  16 , with each slider body having a corresponding transducer  18 . The sliced surfaces become bearing surface  20  and back surface  22 . The top surface  11  of wafer  10  becomes trailing surface  24  and the bottom surface  12  of wafer  10  becomes leading surface  26 .  
         [0016]    Once wafer  10  has been sliced into individual bars  14 , air bearing features are formed into the bearing surface  20  of each slider body  16 . Once the air bearing features have been formed, each bar  14  is diced along a plurality of dice lanes  28  into the plurality individual slider bodies  16 .  
         [0017]    In order to identify each slider body  16 , a serial number is formed on the leading surface  26  of each slider body  16 . The serial number can be applied at the wafer level shown in FIG. 1, the bar level shown in FIG. 2 or the slider level. In a preferred embodiment, the serial number for each slider body is applied at the wafer level by laser scribing the serial number to the bottom surface  12  of wafer  10  at an appropriate location. However, for simplicity, the process of applying the serial number to the slider substrate material will be discussed with reference to an individual slider body.  
         [0018]    [0018]FIGS. 3 a - 3   c  are perspective views illustrating an individual slider body during various steps of the fabrication process of the present invention. FIG. 3 a  illustrates slider body  16  after dicing. Slider body  16  includes air bearing surface  20 , back surface  22 , trailing surface  24  and leading surface  26 . The air bearing features have been formed in air bearing surface  20  and include raised side rails  30  and  32 .  
         [0019]    In FIG. 3 b , a thin, metal film  34  is applied to leading surface  26 . Metal film  34  can be applied by sputtering, plating, chemical vapor deposition or other means for applying a thin metal coating. Metal film  34  has a thickness  36  which can range from a monolayer to several microns, such as 5.0 microns. In a preferred embodiment, thickness  36  is 100-1000 angstroms. Metal film  34  can be applied to the entire leading surface  26  or only a portion of leading surface  26 . Metal film  34  preferably has good adhesion properties. Suitable materials for metal film  34  include chrome, tantalum, and molybdenum, for example. However, any suitable metal material can be used for metal film  34 .  
         [0020]    In FIG. 3 c , a serial number  38  is formed in metal film  34  by laser “scribing” or laser “etching”. A beam of laser light  40  is directed from light source  42  toward metal film  34 . The beam of laser light  40  applies radiation to metal film  34  in the form of a high peak, short duration photon energy pulse which is raster scanned over metal film  34  in a pattern  38  corresponding to the desired serial number or other useful information. The radiation ablates the metal film material within pattern  38 .  
         [0021]    In a preferred embodiment, the laser spot energy density and the pulse duration are adjusted such that the metal film material is completely removed within pattern  38  without removing any underlying slider substrate material. Laser scribing can be preformed by using a pulsed YAG laser, such as a 532 nm double YAG laser or a UV laser. CO 2  lasers and excimer lasers are other examples of lasers that can be used. Also, a continuous wave laser beam can be used instead of a pulsed beam. These lasers have different wavelength energies and different beam characteristics which may be advantageous in specific applications and on specific materials.  
         [0022]    Laser scribing the serial number into metal film  34 , as opposed to directly into the slider substrate material, results in greater contrast in the scribed pattern, which makes the serial number more legible. Also, metal film  34  can be formed very thin, which results in less material being redeposited on the slider substrate and thus less contamination. The decrease in redeposited material also results in less material accumulation at the edge of pattern  38 . This further increases legibility.  
         [0023]    In another embodiment, the laser spot energy density and the pulse duration are adjusted such that material is removed to a depth which is less than the thickness of metal film  34 . In yet another embodiment, material is removed to a depth which is greater than the depth of metal film  34 . In this embodiment, a portion of the slider substrate material which underlies metal film  34  is also removed. The desired pattern is formed through metal film  34  and into the slider substrate material. Metal film  34  can then be stripped from the slider substrate, leaving the desired pattern in the slider substrate. Alternatively, metal film  34  can be left on the slider substrate.  
         [0024]    [0024]FIG. 4 is a greatly magnified illustration of a letter X laser scribed within metal film  34 , as described with reference to FIG. 3 c . The letter X is clearly legible on metal film  34 .  
         [0025]    [0025]FIG. 5 is a greatly magnified illustration of a letter X laser scribed within an uncoated slider substrate according to the prior art. The letter X is much less legible than in FIG. 4. In addition, with an uncoated slider, the laser scribing often creates contamination through substrate redeposition.  
         [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. For example, the position of the serial number is not limited to the leading surface of the slider substrate. The serial number can be applied to any surface on the slider substrate in accordance with the present invention. Also, other useful information can be laser scribed into the slider substrate, such as a date of manufacture or a company logo.