Abstract:
A method of making a tetrahedral amorphous carbon (ta-C) film comprises depositing carbon atoms over the surface of an object. The surface of the object is kept exposed to fluorine atoms during the deposition of the carbon atoms. The method allows the fluorine atoms to scatter within the deposited carbon atoms in the tetrahedral amorphous carbon film. The hardness of the tetrahedral amorphous carbon film can be improved in response to an increased content of sp 3  carbon bonds included within the tetrahedral amorphous carbon film. In addition, the tetrahedral amorphous carbon film still provides a sufficient repellent performance to water due to the fluorine atoms existing near the exposed surface of the tetrahedral amorphous carbon film.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a hard carbon film overlaid on an object. In particular, the invention relates to a hard carbon protection film overlaid on the bottom surface of a slider body in a head slider. The head slider may be incorporated within a magnetic recording medium drive such as a hard disk drive, for example.  
           [0003]    2. Description of the Prior Art  
           [0004]    In general, ahead slider includes a hard carbon film formed to extend over the bottom surface of a slider body. Electronic cyclotron resonance chemical vapor deposition (ECR-CVD) or ion beam deposition (IBD) is usually utilized to form the hard carbon film. The hard carbon film covers over a head or transducer element exposed from the slider body. The hard carbon film serves to protect the head element from damages even when the head slider collides against a hard disk, representative of a magnetic recording medium, and/or contaminations scattered over the head disk.  
           [0005]    Fluorine is applied to the surface of the hard carbon film. The surface of the hard carbon film is exposed to CF 4  plasma for the application of the fluorine. The fluorine serves to prevent adherence or attachment of water or a lubricant agent to the surface of the hard carbon film. Corrosion of the head element can thus be prevented. In addition, if adherence or attachment of water or a lubricant agent is reliably prevented in this manner, the head slider is allowed to keep flying above the surface of the magnetic recording medium or hard disk by a stable flying height.  
           [0006]    As conventionally known, an increased quantity of sp 3  carbon bonds leads to establishment of the compact structure in the hard carbon film. An increased hardness of the hard carbon film gets improved. However, the hardness of the hard carbon film tends to hinder attachment or adherence of the fluorine to the surface of the hard carbon film. Insufficient application of the fluorine may lead to an inevitable attachment or adherence of water or lubricant agent to the head slider.  
         SUMMARY OF THE INVENTION  
         [0007]    It is accordingly an object of the present invention to provide a hard carbon film capable of reliably prevent attachment or adherence of water or lubricant agents irrespective of improvement in the hardness.  
           [0008]    According to the present invention, there is provided a method of making a tetrahedral amorphous carbon (ta-C) film, comprising: depositing carbon atoms over the surface of an object, keeping the surface of the object exposed to fluorine atoms.  
           [0009]    The method allows the fluorine atoms to scatter within the deposited carbon atoms in the tetrahedral amorphous carbon film. The hardness of the tetrahedral amorphous carbon film can be improved in response to an increased content of sp 3  carbon bonds included within the tetrahedral amorphous carbon film. In addition, the tetrahedral amorphous carbon film still provides a sufficient repellent performance to water due to the fluorine atoms existing near the exposed surface of the tetrahedral amorphous carbon film. In particular, since the fluorine atoms are applied during the deposition of the carbon atoms, the fluorine atoms of a sufficient quantity can be introduced into the tetrahedral amorphous carbon film having a compact or closely-packed structure based on an increased amount of sp 3  carbon bonds.  
           [0010]    When the object is to be exposed to the fluorine atoms in the aforementioned manner, the object may be located within the atmosphere of a compound gas including fluorine. Alternatively, the object may be subjected to irradiation of a fluoric ion beam. In either case, the fluorine atoms can sufficiently be introduced into the tetrahedral amorphous carbon film during the deposition of the carbon atoms.  
           [0011]    When the carbon atoms are to be deposited over the surface of the object, the object may be subjected to irradiation of a carbonic ion beam. In particular, it is preferable to utilize a filtered cathodic arc (FCA) to generate the carbonic ion beam. The FCA serves to increase the sp 3  carbon bonds within the tetrahedral amorphous carbon film in a relatively facilitated manner. The tetrahedral amorphous carbon film can efficiently be obtained over the surface of the object.  
           [0012]    The above-described method provides a tetrahedral amorphous carbon film overlaid on a substrate and including fluorine atoms inside the film. The obtained tetrahedral amorphous carbon film is allowed to enjoy a sufficient hardness and repellent performance to water at the exposed surface.  
           [0013]    In this case, the fluorine atoms preferably disperse within tetrahedral amorphous carbon. The content of sp 3  carbon bonds is preferably set equal to or larger than 80%. This content of the sp 3  carbon bonds leads to a sufficient hardness of the tetrahedral amorphous carbon film. The content of the fluorine atoms is preferably set smaller than 20 at %. If the content of fluorine atoms is set at 20 at % or larger, a sufficient hardness cannot be obtained in the tetrahedral amorphous carbon film.  
           [0014]    The tetrahedral amorphous carbon film of the invention may be utilized in a head slider incorporated within a magnetic recording disk drive such as a hard disk drive (HDD), for example. The head slider may comprise a slider body opposing the bottom surface to the recording medium; and a tetrahedral amorphous carbon film overlaid on the bottom surface, said film including fluorine atoms inside. The bottom surface of the head slider can be covered with a protection film having an increased hardness. The bottom surface of the slider body can be protected from damages or collisions irrespective of a reduction in the thickness of the tetrahedral amorphous carbon film. Moreover, since the fluorine atoms exist near the exposed surface of the tetrahedral amorphous carbon film over the bottom surface, a sufficient repellent performance to water can be established over the bottom surface. The bottom surface is reliably prevented from attachment or adherence of water and lubricant agents. The head slider can thus be prevented from variation in the weight. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The above and other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiment in conjunction with the accompanying drawings, wherein:  
         [0016]    [0016]FIG. 1 is a plan view schematically illustrating the interior structure of a hard disk drive (HDD);  
         [0017]    [0017]FIG. 2 is an enlarged perspective view schematically illustrating the structure of a flying head slider according to a specific example;  
         [0018]    [0018]FIG. 3 is a plan view schematically illustrating a medium-opposed or bottom surface of the flying head slider;  
         [0019]    [0019]FIG. 4 is an enlarged partial sectional view schematically illustrating the structure of a hard carbon film;  
         [0020]    [0020]FIG. 5 is a perspective view of a wafer for schematically illustrating the process of making the flying head slider;  
         [0021]    [0021]FIG. 6 is a plan view illustrating wafer bars arranged on a jig;  
         [0022]    [0022]FIG. 7 is a schematic view illustrating the structure of a filtered cathodic arc (FCA) apparatus;  
         [0023]    [0023]FIG. 8 is a graph illustrating the relationship between the content of the fluorine and the hardness for the hard carbon film; and  
         [0024]    [0024]FIG. 9 is graph illustrating the relationship between the content of the fluorine and the angle of contact to water for the hard carbon film. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    [0025]FIG. 1 schematically illustrates the interior structure of a hard disk drive (HDD)  11  as an example of a magnetic recording medium drive or storage device. The HDD  11  includes a box-shaped primary enclosure  12  defining an inner space of a flat parallelepiped, for example. At least one recording medium or magnetic recording disk  13  is accommodated in the inner space within the primary enclosure  12 . The magnetic recording disk  13  is mounted on a driving shaft of a spindle motor  14 . The spindle motor  14  is allowed to drive the magnetic recording disk  13  for rotation at a higher revolution rate such as 7,200 rpm or 10,000 rpm, for example. A cover, not shown, is coupled to the primary enclosure  12  so as to define the closed inner space between the primary enclosure  12  and itself.  
         [0026]    A carriage  16  is also accommodated in the inner space of the primary enclosure  12  for swinging movement about a vertical support shaft  15 . The carriage  16  includes a rigid swinging arm  17  extending in the horizontal direction from the vertical support shaft  15 , and an elastic head suspension  18  fixed to the tip end of the swinging arm  17  so as to extend forward from the swinging arm  17 . As conventionally known, a flying head slider  19  is cantilevered at the tip end of the head suspension  18  through a gimbal spring, not shown. The head suspension  18  serves to urge the flying head slider  19  toward the surface of the magnetic recording disk  13 . When the magnetic recording disk  13  rotates, the flying head slider  19  is allowed to receive an airflow generated along the rotating magnetic recording disk  13 . The airflow serves to generate a lift on the flying head slider  19 . The flying head slider  19  is thus allowed to keep flying above the surface of the magnetic recording disk  13  during rotation of the magnetic recording disk  13  at a higher stability established by the balance between the lift and the urging force of the head suspension  18 .  
         [0027]    When the carriage  16  is driven to swing about the support shaft  15  during flight of the flying head slider  19 , the flying head slider  19  is allowed to cross the recording tracks defined on the magnetic recording disk  13  in the radial direction of the magnetic recording disk  13 . This radial movement serves to position the flying head slider  19  right above a target recording track on the magnetic recording disk  13 . In this case, an electromagnetic actuator  21  such as a voice coil motor (VCM) can be employed to realize the swinging movement of the carriage  16 , for example. As conventionally known, in the case where two or more magnetic recording disks  13  are incorporated within the inner space of the primary enclosure  12 , a pair of the elastic head suspensions  18  are disposed between the adjacent magnetic recording disks  13 .  
         [0028]    [0028]FIG. 2 illustrates a specific example of the flying head slider  19 . The flying head slider  19  of this type includes a slider body  22  made of Al 2 O 3 —TiC in the form of a flat parallelepiped, and a head protection layer  24  formed to spread over the trailing or outflow end of the slider body  22 . The head protection layer  24  may be made of Al 2 O 3 . A read/write electromagnetic transducer  23  is embedded in the head protection layer  24 . The read/write electromagnetic transducer  23  may comprise a read element and a write element. The read element may be represented by a giant magnetoresistive (GMR) element, a tunnel-junction magnetoresistive (TMR) element, or the like. The write head may be represented by a thin film magnetic head utilizing a thin film coil pattern. A medium-opposed surface or bottom surface  25  is defined continuously over the slider body  22  and the head protection layer  24  so as to face the surface of the magnetic recording disk  13  at a distance. The bottom surface  25  is designed to receive an airflow  26  generated along the surface of the rotating magnetic recording disk  13 .  
         [0029]    A pair of rails  27  are formed to extend over the bottom surface  25  from the leading or inflow end toward the trailing or outflow end. The individual rail  27  is designed to define an air bearing surface (ABS)  28  at its top surface. The airflow  26  generates the aforementioned lift at the respective air bearing surfaces  28 . The read/write electromagnetic transducer  23  embedded in the head protection layer  24  is allowed to expose the front end at the air bearing surface  28 . The flying head slider  19  may take any shape or form other than the above-described one.  
         [0030]    As shown in FIG. 3, hard carbon films  29  are overlaid on the overall areas of the air bearing surfaces  28 . The exposed front end of the read/write electromagnetic transducer  23  is covered with the hard carbon films  29 . The thickness of the hard carbon films  29  may be set equal to or smaller than 5.0 nm, for example.  
         [0031]    The hard carbon films  29  are made of so-called tetrahedral amorphous carbon (ta-C). Specifically, the content of the sp 3  carbon bonds is set equal to or larger than 80% in the hard carbon films  29 . In addition, the hard carbon films  29  contain fluorine. As shown in FIG. 4, fluorine atoms  31  are allowed to disperse within the tetrahedral amorphous carbon. The fluorine atoms  31  are completely mixed with carbon atoms  32  of the tetrahedral amorphous carbon. The content of the fluorine may be set smaller than 20 at %.  
         [0032]    Since the sp 3  carbon bonds of a sufficient quantity are contained in the hard carbon films  29 , a compact or closely-packed structure can be established in the hard carbon films  29 . The hardness of the hard carbon films  29  can thus be improved. A sufficient hardness can be maintained in the hard carbon films  29  irrespective of a reduction in the thickness of the hard carbon film  29 . A reduced thickness of the hard carbon films  29  leads to reduction in the space or distance between the exposed front end of the read/write electromagnetic transducer  23  and the magnetic recording disk  13 .  
         [0033]    The hard carbon films  29  still provide a sufficient repellent performance due to the fluorine atoms  31  existing near the exposed surfaces of the hard carbon films  29 . The air bearing surfaces  28  are reliably prevented from attachment or adherence of water. Corrosion of the read/write electromagnetic transducer  23  is reliably prevented. Likewise, the hard carbon films  29  serve to prevent attachment or adherence of lubricant agents to the air bearing surfaces  28 . The flying head slider  19  is allowed to keep flying above the surface of the magnetic recording disk  13  by a stable flying height. The lubricant agents adhering to the flying head slider  19  may bring a change in the weight of the flying head slider  19 , so that the flying head slider  19  tends to suffer from variation in the flying height.  
         [0034]    Next, a brief description will be made on a method of making the flying head slider  19 . As shown in FIG. 5, a wafer  41  made of Al 2 O 3 —TiC is first prepared. The read/write electromagnetic transducers  23  are formed in rows on the surface of the wafer  41 . Each of blocks  42  corresponding to the individual flying head sliders  19  receives each of the read/write electromagnetic transducers  23 . 100 columns by 100 rows of the flying head sliders  19  may be designed in the sole wafer  41  of 5 inches diameter, for example. The read/write electromagnetic transducers  23  may be established on an Al 2 O 3  (alumina) film or underlayer overlaid on the surface of the wafer  41 . The established read/write electromagnetic transducer is then covered with an alumina film or overlayer. The read/write electromagnetic transducers  23  embedded within the head protection layer  24  can be obtained in this manner on the wafer  41 .  
         [0035]    Wafer bars  43  are then cut out from the wafer  41 . The individual wafer bar  43  includes a row of the blocks  42 . The hard carbon film  29  is formed all over the surface of a section  44  of the wafer bar  43 . The method of making the hard carbon film  29  will be described later in detail.  
         [0036]    After the hard carbon film  29  has been formed, the bottom surfaces  25  are individually scraped on the section  44  of the wafer bar  43  for the corresponding blocks  42 . Photolithography may be employed to from the rails  27 , for example. The top surfaces of the rails  27 , namely, the individual air bearing surfaces  28  are kept covered with photoresist films, so that the hard carbon films  29  remain on the individual air bearing surfaces  28 . The individual flying head sliders  19  are finally cut out from the wafer bar  43  for the corresponding blocks  42 .  
         [0037]    A filtered cathodic arc (FCA) is utilized to form the hard carbon film  29 . As shown in FIG. 6, the wafer bars  43  are fixed on a predetermined jig or support  45 , for example. An adhesive may be employed to fix the wafer bars  43 . The jig  45  is then set in a FCA apparatus  46 , as shown in FIG. 7.  
         [0038]    Here, a brief description will be made on the structure of the FCA apparatus  46 . The FCA apparatus  46  includes a chamber  47 . A support plate  48  is located within the chamber  47  for receiving the jig  45 . The support plate  48  is allowed to take any attitude based on the rotation around triaxial directions.  
         [0039]    A cathode  49  is located within the chamber  47  for holding a target. The target may comprise a block of carbon, for example. A striker  51  serves to generate an arc discharge between the cathode  49  or the target and an anode  52 . The arc discharge serves to discharge carbon ions from the target. A material flow of the carbon ions or a carbonic ion beam  55  is guided to the support plate  48  with the assistance of a cathode coil  53  and a raster coil  54 . Non-ionized particles and masses of the carbon are trapped at a filter coil  56 . The carbon ions are thus allowed to reach the wafer bars  43  on the support plate  48  at a remarkably higher density. Carbonic structure including sp 3  carbon bonds at a rate equal to or higher than 80%, namely, tetrahedral amorphous carbon is generated on the sections  44  of the wafer bars  43 .  
         [0040]    CF 4  gas is introduced in the chamber  47  of the FCA apparatus  46 . An atmosphere of the CF 4  gas is established in the chamber  47  when tetrahedral amorphous carbon is formed. Accordingly, fluorine atoms are scattered into the tetrahedral amorphous carbon. Alternatively, an ion beam  57  of CF 4  gas may be utilized to scatter fluorine atoms into the tetrahedral amorphous carbon. An ion gun  58  may be connected to the chamber  47  to realize the ion beam  57 . If the ion beam  57  is irradiated in the direction perpendicular to the carbonic ion beam  55 , the homogeneity of the fluorine atoms can be established within the hard carbon film  29 . In the case where the output power of the ion gun  58  is set larger, the ion beam  57  of the CF 4  gas is preferably oriented in parallel with the sections  44  of the wafer bar  43 , as shown in FIG. 7. The density of the fluorine can be controlled based on the flow rate of the CF 4  gas, the level of the electric power applied to the ion gun  58 , and the like.  
         [0041]    The present inventor has observed the quality of the hard carbon film  29 . In this observation, the inventor have made some kinds of the hard carbon film  29  over silicon wafers. The thickness of the hard carbon films  29  was set at 50.0 nm. The content of the fluorine was set differently for the individual hard carbon films  29 . X-ray photoelectron spectroscopy was utilized to measure the content of the fluorine in the hard carbon films  29 .  
         [0042]    The present inventor has measured the hardness and the angle of contact to water for the individual hard carbon films  29 . Nano indenter II of Nano Instruments was used to measure the hardness of the hard carbon films  29 . As is apparent from FIG. 8, approximately the hardness of 20 GPa can be obtained even when the content of the fluorine atoms is set at 20 at % within the hard carbon film  29 . The inventor has confirmed that the maximum hardness of a carbon film made by electronic cyclotron resonance chemical vapor deposition or ion beam deposition reached approximately 18 GPa. The content of the fluorine atoms below 20 at % within the hard carbon film  29  still provides a sufficient hardness for the hard carbon film  29 . In addition, even if the content of the fluorine atoms are set below 20 at % within the hard carbon film  29 , a sufficient repellent performance to water can be obtained on the surface of the hard carbon film  29 , as is apparent from FIG. 9.