Abstract:
An overcoating for electronic devices, such as magnetic recording devices, includes an intermediate layer formed adjacent to or on the device and a protective layer formed adjacent to or on the intermediate layer. The intermediate layer and protective layer may have a combined thickness in the range of about 6 angstroms to about 35 angstroms. The intermediate layer may be formed of a material such as silicon, aluminum or boron containing borides, carbides, nitrides, oxides or oxynitrides. The protective layer may be formed of a metal oxide material.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of United States Provisional Application No. 60/386,602 filed Jun. 5, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention relates to protective overcoat materials, and more particularly, to a dual layer protective overcoat that may be used on magnetic recording devices.  
         BACKGROUND OF THE INVENTION  
         [0003]    It is generally known to employ a layer of protective overcoat material on various electronic devices or components to, for example, prevent corrosion and increase wear protection. For example, such protective overcoats are used on magnetic recording devices, and particularly on the magnetic recording heads and/or magnetic recording media thereof.  
           [0004]    Most magnetic recording devices operate using a contact start/stop (CSS) method where the recording head begins to slide against the surface of the recording medium as the recording medium begins to rotate. Upon reaching a predetermined rotational speed, the recording head floats in air at a predetermined distance from the surface of the recording medium, i.e. the flying height, where it is maintained during reading and recording operations. Upon terminating operation, the recording head again begins to slide against the surface of the recording medium and eventually stops in contact therewith and presses against the recording medium.  
           [0005]    There is a demand in the computer hard drive industry to develop disc drives with an increased areal storage density. To achieve the increased areal storage density, the flying height and/or the head to media spacing between the recording head and the recording medium need to be minimized. This in turn means that the thickness of the protective overcoat material used on the recording head and/or on the recording medium needs to be minimized while still being capable of protecting the head and/or medium during the repeated CSS sequence and from corrosion.  
           [0006]    The most common overcoat material currently used on recording heads and recording media to prevent corrosion and provide increased wear protection is a diamond like carbon (DLC) overcoat material. The thickness of DLC layers currently used is about 40-50 angstroms. However, it has been determined that a layer of the DLC overcoat having a thickness of about 20 angstroms may be the limit as to how thin the DLC overcoat can be made. Specifically, a thickness of about 20 angstroms results in the DLC layer becoming either discontinuous or porous and the DLC layer developing a high pin hole density. These results are detrimental for the material to function properly as a wear and corrosion protection overcoat. Thus, it is necessary to develop thinner overcoat materials that provide sufficient corrosion and wear protection. This development is important for ultimately achieving the desired higher areal storage density in recording devices.  
           [0007]    Accordingly, there is identified a need for improved protective overcoats that overcome limitations, disadvantages and/or shortcomings of known protective overcoats.  
           [0008]    In addition, there is identified a need for an improved protective overcoat for use on magnetic recording devices that overcomes limitations, disadvantages, and/or shortcomings of known overcoat materials used on magnetic recording devices.  
         SUMMARY OF THE INVENTION  
         [0009]    Embodiments of the invention meet the identified needs, as well as other needs, as will be more fully understood following a review of the specification and drawings.  
           [0010]    In accordance with an aspect of the invention, an overcoating for electronic devices includes an intermediate layer adjacent to the electronic device and a protective layer adjacent to the intermediate layer. The intermediate layer and the protective layer together have a combined thickness in the range of about 6 angstroms to about 35 angstroms. More specifically, the intermediate layer may have a thickness in the range of about 2 angstroms to about 15 angstroms and the protective layer may have a thickness in the range of about 4 angstroms to about 20 angstroms. The intermediate layer may include at least one of Si, Al or B containing borides, carbides, nitrides, oxides or oxynitrides. The protective layer may be formed of a metal oxide material, such as, for example, ZrO 2 , HfO 2 , BeO 2 , MgO 2 , Ta 2 O 5  Al 2 O 3 , Al 2 TiO 5 , TiO 2  SiO 2 , Y 2 O 3 , RuO 2 , or a composite or laminated structure of any combination of metal oxide materials such as, for example, Al 2 O 3 /ZrO 2 .  
           [0011]    In accordance with an additional aspect of the invention, a structure comprises a magnetic recording device, an intermediate layer formed on the magnetic recording device and a protective layer formed on the intermediate layer. The magnetic recording device may be, for example, a recording head or a recording medium.  
           [0012]    In accordance with yet another aspect of the invention, a method for overcoating a device comprises depositing on the device an intermediate layer of material having a thickness in the range of about 2 angstroms to about 15 angstroms, and depositing on the intermediate layer a protective layer of material having a thickness in the range of about 4 angstroms to about 20 angstroms. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a pictorial representation of a disc drive system that may utilize the invention.  
         [0014]    [0014]FIG. 2 is a partially schematic side view of an embodiment of a recording head and recording medium in accordance with the invention.  
         [0015]    [0015]FIG. 3 is a partially schematic side view of an additional embodiment of a recording head and recording medium constructed in accordance with the invention.  
         [0016]    [0016]FIG. 4 is a schematic illustration of a thin film structure constructed to illustrate an aspect of the invention.  
         [0017]    [0017]FIG. 5 is a graphical illustration of oxidation percentage versus thickness for the thin film structure shown in FIG. 4.  
         [0018]    [0018]FIG. 6 is a schematic illustration of a thin film structure constructed in accordance with the invention.  
         [0019]    [0019]FIG. 7 is a graphical illustration of the high resolution Co2p3 spectra for the thin film structure shown in FIG. 6. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    The invention relates to protective overcoat materials, and more particularly, to a dual layer protective overcoat that may be used, for example, on magnetic recording devices. While the invention is particularly suitable for use with magnetic recording devices, such as the magnetic recording head, slider and magnetic recording medium thereof, it will be appreciated that the invention may also be used with other type storage systems such as, for example, magneto-optical or optical storage systems. In addition, it will be appreciated that the protective overcoat of the invention may be utilized on various other electronic devices or components such as, for example, micro-electromechanical systems (MEMS), optical devices, cutting tools, automobile components or aerospace components.  
         [0021]    [0021]FIG. 1 is a pictorial representation of a disc drive  10  that can utilize a magnetic recording head, which may be a longitudinal, perpendicular or other type recording head, constructed in accordance with this invention. The disc drive  10  includes a housing  12  (with the upper portion removed and the lower portion visible in this view) sized and configured to contain the various components of the disc drive. The disc drive  10  includes a spindle motor  14  for rotating at least one storage medium  16 . At least one arm  18  is contained within the housing  12 , with each arm  18  having a first end  20  with a slider  23 , and a second end  24  pivotally mounted on a shaft by a bearing  26 . An actuator motor  28  is located at the arm&#39;s second end  24  for pivoting the arm  18  to position the slider  23  over a desired sector or track  27  of the disc  16 . The actuator motor  28  is regulated by a controller, which is not shown in this view and is well known in the art.  
         [0022]    Referring to FIG. 2, there is illustrated an embodiment of a recording head  22  mounted on the slider  23 . There is also illustrated a recording medium  16  positioned adjacent to or under the recording head  22  and the slider  23 , as is generally known in the art. It will be appreciated that the recording medium  16  may be constructed as either a longitudinal recording medium or a perpendicular recording medium or other type recording medium as may be desired. It will be further appreciated that the recording head  22  may be constructed as either a longitudinal recording head or a perpendicular recording head or other type recording head as may be desired.  
         [0023]    Still referring to FIG. 2, the recording medium  16  may include a substrate  30 , which may be made of any suitable material such as aluminum, ceramic glass or amorphous glass. A recording layer  32  is deposited on the substrate  30 . Suitable magnetic materials for the recording layer  32  may include at least one material selected from, for example, FePt or CoCrPt alloys having a relatively high anisotropy at ambient temperature.  
         [0024]    In accordance with this embodiment of the invention, the recording medium  16  includes an intermediate layer  34  deposited on the recording layer  32 . In addition, a protective layer  36  is deposited on the intermediate layer  34 . The intermediate layer  34  and the protective layer  36  combine to effectively provide a protective overcoating for the recording medium  16 , and particularly for the recording layer  32  thereof. For example, layers  34  and  36  combine to provide wear protection for the recording medium  16  from contact with the recording head  22  and/or the slider  23 .  
         [0025]    The protective layer  36  is separated from the air bearing surface (ABS) of the recording head  22  and the slider  23  by a distance generally referred to as the flying height (FH). The recording layer  32  is positioned from the ABS of the recording head  22  and the slider  23  by a distance generally referred to as the head-to-media spacing (HMS). The intermediate layer  34  and the protective layer  36  are deposited in very thin layers so as to allow for the flying height FH and/or the head-to-media spacing HMS dimensions to be as small as possible which is advantageous when developing recording heads and media with an increased areal storage density.  
         [0026]    The intermediate layer  34  may have a thickness in the range of about 2 angstroms to about 15 angstroms. The protective layer  36  may have a thickness in the range of about 4 angstroms to about 20 angstroms. Thus, the combined thickness of the intermediate layer  34  and the protective layer  36  may be in the range of about 6 angstroms to about 35 angstroms.  
         [0027]    The intermediate layer  34  may include at least one material selected from the group consisting of Si, Al and B. The intermediate layer  34  may also include at least one of a boride, a nitride, a carbide, an oxynitride or an oxide. Thus, the intermediate layer  34  may be formed of covalent hard materials, which can be used as thin intermediate adhesion layers between the material used to form the recording layer  32  and the material used to form the protective layer  36 . Suitable covalent hard materials possess higher bulk modulus and mechanical hardness than most metal films, and have good wetting properties with the metal films. Therefore, these materials can enhance the mechanical properties and adhesion when used in combination with the protective layer  36  to form the protective overcoating for the recording layer  32 .  
         [0028]    The protective layer  36  may be formed of a metal oxide material. For example, the protective layer  36  may be formed of a material selected from the group consisting of ZrO 2 , Hfo 2 , BeO 2 , MgO 2 , Ta 2 O 5 , A 1 2O3, Al 2 TiO 5 , TiO 2  SiO 2 , Y 2 O 3 , RuO 2 , or a composite or laminated structure of any combination of metal oxide materials such as, for example, Al 2 O 3 /ZrO 2 . The metal oxide materials used to form the protective layer  36  should possess high electrical resistivity and high bulk modulus and high hardness properties.  
         [0029]    Referring to FIG. 3, there is illustrated an additional embodiment of the invention including a recording medium  116  positioned adjacent to or under a recording head  122  and slider  123 . The recording medium  116  includes a substrate  130  and a recording layer  132  formed on the substrate  130 . In this embodiment, the overcoating, which includes an intermediate layer  134  and a protective layer  136 , is formed on the recording head  122  and/or the slider  123 . The thicknesses and the materials for forming the intermediate layer  134  and the protective layer  136  is essentially the same as described herein for the embodiment illustrated in FIG. 2 where the overcoating is formed on the recording medium  16 . The intermediate layer  134  and protective layer  136  also serve a similar function in regards to the recording head  122  and/or slider  123  as does the intermediate layer  34  and protective layer  36  in regards to the recording medium  16 .  
         [0030]    It will be appreciated that while the embodiments illustrated in FIG. 2 and FIG. 3 illustrate an overcoating applied to a recording medium and a recording head/slider, respectively, the overcoating may be applied to both the recording medium and the recording head/slider if desired. A limiting factor in applying the overcoating to both the recording medium and the recording head and/or the slider would be the thicknesses of the intermediate layers and the protective layers and the impact that such thicknesses would have on the flying height FH and/or the head-to-media spacing HMS.  
         [0031]    Referring to FIG. 4, there is illustrated a layer  232 , formed of Co and corresponding to the recording layers  32  and  132  described herein, having an intermediate layer  234 , corresponding to the intermediate layers  34  and  134  described herein, formed thereon. This thin film structure was constructed to illustrate the effectiveness of the intermediate layer in forming the overcoating of the invention. Specifically, the intermediate layer  234  was formed of a layer of SiB x , wherein 3≦×≦6, with thicknesses ranging from about 4 angstroms to about 15 angstroms and was deposited on the layer  232  of Co having a thickness of about 200 angstroms. The deposition was performed using DC magnetron sputtering at an Ar total pressure of 1-2 mTorr. Electron spectroscopy for chemical analysis (ESCA) was used to obtain high resolution Co2p3 peaks to evaluate the continuity of the thin films of the intermediate layer  234 . The reactive DC sputtering of the metal oxide materials can be modified to RF sputtering from oxide targets to prevent in-situ oxygen plasma oxidation of the recording layer  32  and to simplify the deposition control process.  
         [0032]    [0032]FIG. 5 illustrates the percentage of oxidized Co for the layer  232  as a function of the thickness of the intermediate layer  234 . The results suggest that an intermediate layer  234  of SiB x  as thin as 15 angstroms is sufficient to prevent the Co layer  232  from reacting with oxygen at ambient temperature. These results further suggest a good wetting property between the Co layer  232  and the intermediate layer  234 . Therefore, a thin layer of SiB x  can be used as an effective intermediate layer  234  between media materials and oxide overcoat materials, such as used to form the protective layer.  
         [0033]    To further illustrate the invention, reference is made to FIG. 6. Specifically, an intermediate layer  334  is formed on a layer  332  of Co and a protective layer  336  is formed on the intermediate layer  334 . The layer  332  had a thickness of about 200 angstroms, the intermediate layer  334  was formed of SiB x , wherein 3≦×≦6, with a thickness of about 8 angstroms and the protective layer  336  was formed of ZrO 2  with a thickness of about 4 angstroms. These layers were deposited using DC magnetron sputtering at a total pressure of 1-2 m Torr (comprising Ar of 70% and O 2  of 30% in total flow rate) on Si/SiO 2  substrates (not shown). An advantage of the invention is that use of the intermediate layer, such as layer  34 ,  134  or  234 , can prevent or minimize in-situ oxidation due to the use of an oxygen plasma. Specifically, reactive sputtering of metal oxides, such as used to form the protective layer  36 ,  136  or  236 , may involve oxygen plasma and due to the high reactivity of oxygen plasma in the system, the control of oxygen partial pressure becomes difficult.  
         [0034]    ESCA was used to obtain high resolution Co2p3 peaks to evaluate the continuity of the dual layer overcoating, i.e., the intermediate layer  334  and the protective layer  336 , before and after high temperature/high humidity (80° C./80% for four days) exposures. The high resolution Co2p3 spectra results are illustrated in FIG. 7. Specifically, it was determined that Co remains in metallic form before and after the temperature and humidity tests, therefore demonstrating that the intermediate layer  334  and protective layer  336  with a combined thickness of about 12 angstroms effectively prevents the layer of Co from being oxidized at approximately ambient temperature and aggressive environments. Sputtered carbon overcoats would normally require much thicker layers to provide such oxidation protection for a pure Co underlayer. Accordingly, these results clearly show that the present invention can provide superior corrosion and wear protection for media and head materials.  
         [0035]    Whereas particular embodiments have been described herein for the purpose of illustrating the invention and not for the purpose of limiting the same, it will be appreciated by those of ordinary skill in the art that numerous variations of the details, materials, and arrangement of parts may be made within the principle and scope of the invention without departing from the invention as described in the appended claims.