Abstract:
A method of manufacturing magnetic recording media, comprising sequential steps of: (a) providing an apparatus for manufacturing the media; (b) supplying the apparatus with at least one substrate for the media; (c) forming a magnetic recording layer on the at least one substrate in a first portion of the apparatus, the magnetic recording layer including an exposed surface; (d) thermally oxidizing the exposed surface of the magnetic recording layer in a second portion of the apparatus; and (e) forming a protective overcoat layer on the thermally oxidized exposed surface of the magnetic recording layer in a third portion of the apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application contains subject matter related to subject matter disclosed in co-pending, commonly assigned U.S. patent application Ser. No. ______, filed on ______ (Attorney Docket No. 50103-527); Ser. No. ______, filed on ______ (Attorney Docket No. 50103-551); and Ser. No. ______, filed on ______ (Attorney Docket No. 50103-556). 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a method for improving the performance characteristics of high areal recording density magnetic recording media, and to media obtained thereby. The invention has particular utility in the manufacture of high areal recording density perpendicular media, e.g., hard disks, utilizing granular-type magnetic recording layers.  
       BACKGROUND OF THE INVENTION  
       [0003]     Magnetic media are widely used in various applications, particularly in the computer industry, and efforts are continually made with the aim of increasing the areal recording density, i.e., bit density of the magnetic media. In this regard, so-called “perpendicular” recording media have been found to be superior to the more conventional “longitudinal” media in achieving very high bit densities. In perpendicular magnetic recording media, residual magnetization is formed in a direction perpendicular to the surface of the magnetic medium, typically a layer of a magnetic material on a suitable substrate. Very high linear recording densities are obtainable by utilizing a “single-pole” magnetic transducer or “head” with such perpendicular magnetic media.  
         [0004]     Efficient, high bit density recording utilizing a perpendicular magnetic medium requires interposition of a relatively thick (as compared with the magnetic recording layer), magnetically “soft” underlayer (“SUL”) layer, i.e., a magnetic layer having a relatively low coercivity of about 1 kOe or below, such as of a NiFe alloy (Permalloy), between the non-magnetic substrate, e.g., of glass, aluminum (Al) or an Al-based alloy, and the magnetically “hard” recording layer having relatively high coercivity of several kOe, typically about 3-6 kOe, e.g., of a cobalt-based alloy (e.g., a Co—Cr alloy such as CoCrPtB) having perpendicular anisotropy. The magnetically soft underlayer serves to guide magnetic flux emanating from the head through the hard, perpendicular magnetic recording layer.  
         [0005]     A typical conventional perpendicular recording system  10  utilizing a vertically oriented magnetic medium  1  with a relatively thick soft magnetic underlayer, a relatively thin hard magnetic recording layer, and a single-pole head, is illustrated in  FIG. 1 , wherein reference numerals  2 ,  2 A,  3 ,  4 , and  5 , respectively, indicate a non-magnetic substrate, an adhesion layer (optional), a soft magnetic underlayer, at least one non-magnetic interlayer, and at least one perpendicular hard magnetic recording layer. Reference numerals  7  and  8 , respectively, indicate the single and auxiliary poles of a single-pole magnetic transducer head  6 . The relatively thin interlayer  4  (also referred to as an “intermediate” layer), comprised of one or more layers of non-magnetic materials, serves to (1) prevent magnetic interaction between the soft underlayer  3  and the at least one hard recording layer  5  and (2) promote desired microstructural and magnetic properties of the at least one hard recording layer.  
         [0006]     As shown by the arrows in the figure indicating the path of the magnetic flux φ, flux φ is seen as emanating from single pole  7  of single-pole magnetic transducer head  6 , entering and passing through the at least one vertically oriented, hard magnetic recording layer  5  in the region above single pole  7 , entering and travelling along soft magnetic underlayer  3  for a distance, and then exiting therefrom and passing through the at least one perpendicular hard magnetic recording layer  5  in the region above auxiliary pole  8  of single-pole magnetic transducer head  6 . The direction of movement of perpendicular magnetic medium  1  past transducer head  6  is indicated in the figure by the arrow above medium  1 .  
         [0007]     With continued reference to  FIG. 1 , vertical lines  9  indicate grain boundaries of polycrystalline layers  4  and  5  of the layer stack constituting medium  1 . Magnetically hard main recording layer  5  is epitaxially formed on interlayer  4 , and while the grains of each polycrystalline layer are of differeing widths (as measured in a horizontal direction) represented by a grain size distribution, they are generally in vertical registry (i.e., vertically “correlated” or aligned). Completing the layer stack is a protective overcoat layer  11 , such as of a diamond-like carbon (DLC), formed over hard magnetic layer  5 , and a lubricant topcoat layer  12 , such as of a perfluoropolyethylene material, formed over the protective overcoat layer.  
         [0008]     Substrate  2  is typically disk-shaped and comprised of a non-magnetic metal or alloy, e.g., Al or an Al-based alloy, such as Al—Mg having an Ni—P plating layer on the deposition surface thereof, or substrate  2  is comprised of a suitable glass, ceramic, glass-ceramic, polymeric material, or a composite or laminate of these materials; optional adhesion layer  2 A, if present, may comprise an up to about 30 Å thick layer of a material such as Ti or a Ti alloy; soft magnetic underlayer  3  is typically comprised of an about 500 to about 4,000 Å thick layer of a soft magnetic material selected from the group consisting of Ni, NiFe (Permalloy), Co, CoZr, CoZrCr, CoZrNb, CoFeZrNb, CoFe, Fe, FeN, FeSiAl, FeSiAlN, FeCoB, FeCoC, etc.; interlayer  4  typically comprises an up to about 300 Å thick layer or layers of non-magnetic material(s), such as Ru, TiCr, Ru/CoCr 37 Pt 6 , RuCr/CoCrPt, etc.; and the at least one hard magnetic layer  5  is typically comprised of an about 100 to about 250 Å thick layer(s) of Co-based alloy(s) including one or more elements selected from the group consisting of Cr, Fe, Ta, Ni, Mo, Pt, V, Nb, Ge, B, and Pd, iron nitrides or oxides, or a (CoX/Pd or Pt) n  multilayer magnetic superlattice structure, where n is an integer from about 10 to about 25, each of the alternating, thin layers of Co-based magnetic alloy is from about 2 to about 3.5 Å thick, X is an element selected from the group consisting of Cr, Ta, B, Mo, Pt, W, and Fe, and each of the alternating thin, non-magnetic layers of Pd or Pt is up to about 10 Å thick. Each type of hard magnetic recording layer material has perpendicular anisotropy arising from magneto-crystalline anisotropy (1 st  type) and/or interfacial anisotropy (2 nd  type).  
         [0009]     Another currently employed way of classifying perpendicular magnetic recording media is on the basis by which the magnetic grains are mutually separated, i.e., segregated, in order to physically de-couple the grains and provide improved media performance characteristics. Thus, magnetic media with Co-based alloy perpendicular magnetic recording layers (e.g., CoCr alloys) are typically classified into two distinct types: (1) a first type, wherein segregation of the grains occurs by diffusion of Cr atoms of the magnetic layer to the grain boundaries of the layer to form Cr-rich grain boundaries, which diffusion process requires heating of the media substrate during formation (deposition) of the magnetic layer; and (2) a second type, wherein segregation of the grains occurs by formation of oxides and/or nitrides at the boundaries between adjacent magnetic grains to form so-called “granular” media, which oxides and/or nitrides may be formed by introducing a minor amount of at least one reactive gas, i.e., oxygen (O 2 ) and/or nitrogen (N 2 ) to the inert gas (e.g., Ar) atmosphere during sputter deposition of the Co alloy-based perpendicular magnetic layer. Generally, substrate heating is not required during such reactive sputtering deposition of the magnetic layer.  
         [0010]     According to conventional methodology for formation of perpendicular magnetic recording media, it is required that the media precursor, i.e., a media substrate with a stack of layers formed thereon, including a topmost perpendicular magnetic recording layer, be removed from the manufacturing apparatus, e.g., a sputtering apparatus, for exposure to the ambient atmosphere in order to form a surface oxide layer on the magnetic recording layer prior to deposition of a protective overcoat layer thereon, e.g., a carbon (C)-based layer, such as diamond-like carbon (DLC). Typically, the sputtering apparatus constitutes one chamber of an in-line- or circularly-configured multi-chamber or similar type apparatus, for use in performing large-scale, automated, continuous manufacture of magnetic recording media. However, removal of the media precursor from the multi-chamber sputtering apparatus for performing the surface oxidation treatment by exposure of the media precursor to the ambient atmosphere prior to the carbon deposition step severely impacts the efficiency and manufacturing throughput of the apparatus. Specifically, according to the conventional methodology, additional air locks, loading and unloading means, etc., are required for removing media precursors from a continuous manufacturing apparatus in order to perform the ambient oxidation treatment and then supplying the surface-oxidized media precursors to another manufacturing apparatus (or returning them to the previously utilized multi-chamber apparatus) for subsequent processing, e.g., protective overcoat formation. In addition, the removal of the media precursors from the manufacturing apparatus and the surface oxidation treatment via exposure to the ambient atmosphere disadvantageously incur an excessive increase in the overall media manufacturing interval, cost, and efficiency.  
         [0011]     In view of the foregoing, there exists a clear need for means and methodology for manufacturing improved, high areal recording density, high performance perpendicular magnetic recording media, which means and methodology avoid the disadvantages and drawbacks associated with the above-described conventional means and methodology, and which facilitate high throughput, cost-effective, automated manufacture of such high performance perpendicular magnetic recording media.  
         [0012]     The present invention, therefore, addresses and solves the above-described problems, drawbacks, and disadvantages relating to the poor efficiency and product throughput associated with conventional means and methodology for the manufacture of high performance perpendicular magnetic recording media, while maintaining full compatibility with all aspects of automated magnetic media manufacture.  
       DISCLOSURE OF THE INVENTION  
       [0013]     An advantage of the present invention is an improved method of manufacturing magnetic recording media.  
         [0014]     Another advantage of the present invention is an improved method of manufacturing perpendicular magnetic recording media.  
         [0015]     Still another advantage of the present invention is an improved method of manufacturing magnetic recording media according to a continuous fabrication process.  
         [0016]     Yet another advantage of the present invention is an improved method of manufacturing perpendicular magnetic recording media according to a continuous fabrication process.  
         [0017]     A further advantage of the present invention is improved perpendicular magnetic recording media fabricated according to the inventive methodology.  
         [0018]     Additional advantages and other features of the present invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.  
         [0019]     According to an aspect of the present invention, the foregoing and other advantages are obtained in part by a method of manufacturing magnetic recording media, comprising sequential steps of: 
        (a) providing an apparatus for manufacturing the media;     (b) supplying the apparatus with at least one substrate for the media;     (c) forming a magnetic recording layer on the at least one substrate in a first portion of the apparatus, the magnetic recording layer including an exposed surface;     (d) thermally oxidizing the exposed surface of the magnetic recording layer in a second portion of the apparatus; and     (e) forming a protective overcoat layer on the thermally oxidized exposed surface of the magnetic recording layer in a third portion of the apparatus.        
 
         [0025]     According to preferred embodiments of the present invention, step (a) comprises providing a linearly or circularly-configured apparatus including at least said first, second, and third spaced-apart portions; the apparatus is adapted for continuous manufacture of a plurality of the media, and includes means for transporting the at least one substrate serially through the first, second, and third spaced-apart portions, the first, second, and third spaced-apart portions comprising respective first, second, and third spaced-apart chambers; the second chamber comprising means for performing a thermal oxidation process therein, e.g., by flowing an oxygen (O 2 )-containing gas past the exposed upper surface of the magnetic recording layer formed on the at least one substrate in step (c), the second chamber further comprising means for heating the at least one substrate to a preselected temperature; and the first and third chambers each comprise means for performing therein a thin film deposition process on the at least one substrate, the first and third chambers comprising means for performing a respective sputter deposition process therein.  
         [0026]     In accordance with preferred embodiments of the present invention, step (b) comprises supplying the apparatus with at least one disk-shaped non-magnetic substrate for a hard disk magnetic recording medium; step (c) comprises forming a perpendicular magnetic recording layer, e.g., a Cr-segregated, Cr-rich grain boundary Co-based alloy perpendicular magnetic recording layer or a granular Co-based alloy perpendicular magnetic recording layer; step (d) comprises flowing an oxygen (O 2 )-containing gas past the exposed upper surface of the magnetic recording layer while supplying heat to the at least one substrate; and step (e) comprises forming a carbon (C)-based protective overcoat on the thermally oxidized exposed surface of the magnetic recording layer, e.g., by sputter deposition.  
         [0027]     Particular embodiments of the present invention include those wherein step (c) comprises forming a Cr-segregated, Cr-rich grain boundary Co-based alloy perpendicular magnetic recording layer comprised of a CoCrPtX alloy, where X=at least one element selected from the group consisting of Ta, B, Mo, V, Nb, W, Zr, Re, Cu, Ag, Hf, Ir, and Y, and wherein Co-containing magnetic grains with hcp lattice structure are segregated by Cr-rich grain boundaries; and those wherein step (c) comprises forming a granular Co-based alloy perpendicular magnetic recording layer comprised of a CoPtX alloy, where X=at least one element or material selected from the group consisting of Cr, Ta, B, Mo, V, Nb, W, Zr, Re, Ru, Cu, Ag, Hf, Ir, Y, SiO 2 , SiO, Si 3 N 4 , Al 2 O 3 , AlN, TiO, TiO 2 , TiO x , TiN, TiC, Ta 2 O 3 , NiO, and CoO, and wherein Co-containing magnetic grains with hcp lattice structure are segregated by grain boundaries comprising at least one of oxides, nitrides, and carbides.  
         [0028]     Another aspect of the present invention is a method of manufacturing magnetic recording media according to a continuous fabrication process, comprising sequential steps of: 
        (a) providing at least one substrate for the magnetic recording media;     (b) providing an apparatus adapted for continuous manufacturing of the magnetic recording media, comprising at least first, second, and third spaced-apart, serially arranged processing chambers and including means for transporting the at least one substrate serially through at least the first, second, and third spaced-apart processing chambers;     (c) transporting the at least one substrate through the first processing chamber while forming a magnetic recording layer thereon, the magnetic recording layer having an exposed upper surface;     (d) transporting the at least one substrate with the magnetic recording layer formed thereon to the second processing chamber;     (e) transporting the at least one substrate through the second processing chamber while thermally oxidizing the exposed upper surface of the magnetic recording layer by flowing an oxygen (O 2 )-containing gas past the exposed upper surface of the magnetic recording layer while supplying heat to the at least one substrate;     (f) transporting the at least one substrate with the thermally oxidized exposed upper surface of the magnetic recording layer to the third processing chamber; and     (g) transporting the at least one substrate with the thermally oxidized exposed upper surface of the magnetic recording layer through the third processing chamber while forming a protective overcoat layer thereon, wherein:     the at least one substrate is transported between and through each of the first, second, and third processing chambers at a substantially constant rate.        
 
         [0037]     According to preferred embodiments of the present invention, step (a) comprises providing at least one disk-shaped non-magnetic substrate for hard disk recording media; step (b) comprises providing an apparatus wherein the first and third chambers comprise means for performing a thin film deposition process therein and the second chamber comprises means for flowing an oxygen (O 2 )-containing gas past a surface of a moving substrate while supplying heat to the substrate; and step (c) comprises forming a Cr-segregated, Cr-rich grain boundary Co-based alloy perpendicular magnetic recording layer or a granular Co-based alloy perpendicular magnetic recording layer.  
         [0038]     A further aspect of the present invention is perpendicular magnetic recording media fabricated according to the inventive methodology.  
         [0039]     Additional advantages and aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein embodiments of the present invention are shown and described, simply by way of illustration of the best mode contemplated for practicing the present invention. As will be described, the present invention is capable of other and different embodiments, and its several details are susceptible of modification in various obvious respects, all without departing from the spirit of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as limitative. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]     The following detailed description of the embodiments of the present invention can best be understood when read in conjunction with the following drawings, in which the various features are not necessarily drawn to scale but rather are drawn as to best illustrate the pertinent features, wherein:  
         [0041]      FIG. 1  schematically illustrates, in simplified cross-sectional view, a portion of a magnetic recording storage, and retrieval system comprised of a perpendicular magnetic recording medium and a single pole transducer head; and  
         [0042]      FIG. 2  schematically illustrates, in simplified plan view, a portion of an in-line apparatus for continuous manufacture of magnetic recording media according to an embodiment of the present invention. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0043]     The present invention addresses and solves productivity throughput and cost-effectiveness problems and drawbacks associated with conventional manufacturing processing for the manufacture of high areal recording density, high performance perpendicular magnetic recording media, e.g., high product throughput, automated, continuous manufacture of hard disks, while maintaining full compatibility with all aspects and requirements of such automated manufacturing technology for magnetic media manufacture.  
         [0044]     Specifically, the present invention addresses and solves problems and drawbacks associated with the conventional requirement that the media precursor, i.e., a media substrate with a stack of layers formed thereon, including a topmost perpendicular magnetic recording layer, be removed from the manufacturing apparatus, e.g., a sputtering apparatus, for exposure to the ambient atmosphere in order to form a surface oxide layer on the magnetic recording layer prior to deposition of a protective overcoat layer thereon, e.g., a carbon (C)-based layer, such as diamond-like carbon (DLC). As previously indicated, the sputtering apparatus typically constitutes one chamber of an in-line- or circularly-configured multi-chamber or similar type apparatus utilized in the large-scale, automated, continuous manufacture of magnetic recording media. However, removal of the media precursor from the multi-chamber sputtering apparatus for performing the surface oxidation treatment by exposure of the media precursor to the ambient atmosphere prior to the carbon deposition step severely impacts the efficiency and manufacturing throughput of the apparatus. According to the conventional methodology, additional air locks, loading and unloading means, etc., are required for removing media precursors from a continuous manufacturing apparatus in order to perform the ambient oxidation treatment and for supplying the surface-oxidized media precursors to another manufacturing apparatus (or returning them to the previously utilized multi-chamber apparatus) for subsequent processing, e.g., protective overcoat formation. In addition, the removal of the media precursors from the manufacturing apparatus and the surface oxidation treatment via exposure to the ambient atmosphere disadvantageously incur an excessive increase in the overall media manufacturing interval, cost, and efficiency.  
         [0045]     The present invention, therefore, is based upon recognition by the inventors that the requisite oxidation treatment of the surfaces of perpendicular magnetic recording layers of media precursors can be satisfactorily performed in rapid, efficient, and cost-effective manner, by means of an in situ post-deposition thermal oxidation process utilizing a manufacturing apparatus comprising a dedicated thermal oxidation treatment portion or station intermediate a pair of spaced-apart thin film deposition portions for respectively forming the perpendicular magnetic recording and protective overcoat layers. As a consequence of the thermal oxidation process afforded by the invention, the previous requirement for removal of the media precursors from the magnetic layer deposition station (e.g., a sputter deposition chamber) for exposure of the just-formed perpendicular magnetic layer to the ambient atmosphere for surface oxidation, prior to formation thereon of the protective overcoat layer at another deposition station is eliminated. According to the invention, therefore, the disadvantages and drawbacks associated with the conventional technology, including, inter alia: removal of the media precursor substrates from the manufacturing apparatus, the relatively long interval (e.g., from about 10 sec. to about 4 hrs. for surface oxidation of the magnetic recording layer in the ambient (i.e., room temperature) atmosphere, and return of the surface-oxidized media precursors to the previously employed manufacturing apparatus or to another manufacturing apparatus for further processing/treatment (e.g., for protective overcoat formation) are effectively avoided while product throughput rates are increased.  
         [0046]     Referring now to  FIG. 2 , schematically illustrated therein, in simplified plan view, is a portion of an in-line apparatus  20  for continuous manufacture of magnetic recording media according to an embodiment of the present invention. As illustrated, apparatus  20  comprises a series of linearly arranged process chambers interconnected by respective buffer/isolation chambers  26 , etc., each equipped with gate means G. Specifically, apparatus  20  includes first and second spaced-apart thin film deposition chambers or stations  21  and  22 , illustratively sputter deposition chambers or stations, each including at least one, preferably a pair of spaced-apart, facing sputter sources  23  or  24 , for performing deposition of a thin film on at least one surface of workpieces/substrates  25 , preferably simultaneous thin film deposition on both sides of dual-sided workpieces/substrates  25 , and pairs of buffer/isolation chambers, such as  26 ,  26 ′ and  26 ″,  26 ′″, at opposite laterally spaced ends of respective deposition chambers or stations  21  and  22  for insertion and withdrawal, respectively, of a plurality of workpieces/substrates  25 , e.g., disk-shaped substrates for hard disk recording media carried and transported through each station and from station-to-station by a corresponding plurality of workpiece/substrate mounting/transport means (not shown in the figure for illustrative simplicity), whereby each of the opposing surfaces of the dual-surfaced workpieces/substrates  25  faces a respective sputter source  23  or  24  during “pass-by” transport and treatment/processing in apparatus  20 . Chambers  27 ,  27 ′ respectively connected to the distal ends of inlet and outlet buffer/isolation chambers  26  and  26 ′″, respectively, are provided for utilizing apparatus  20  as part of a larger, continuously operating, in-line apparatus wherein the workpieces/substrates  25  receive deposition or other treatment antecedent and/or subsequent to processing in the apparatus portion illustrated in  FIG. 2 .  
         [0047]     According to the invention, a third station or chamber  28 , i.e., a thermal oxidation chamber, is positioned intermediate the first and second spaced-apart sputter deposition chambers or stations  21  and  22  and operatively connected thereto by means of buffer/isolation chambers  26 ′ and  26 ″ (and associated gate means G) at the respective inlet and outlet ends thereof. As illustrated, chamber  28  is adapted for performing a thermal oxidation of opposing surfaces of dual-sided substrate/workpieces  25 , and includes opposing pairs of gas (i.e., oxygen, O 2 ) inlets  30 ,  30 ′ and outlets  31 ,  31 ′ for flowing gas past the opposing surfaces of substrate/workpieces  25 , as well as a pair of heating means  29 ,  29 ′ for heating each of the opposing surfaces of the substrates/workpieces  25 , e.g., electrical resistance heating means.  
         [0048]     In operation of apparatus  20 , substrates/workpieces  25 , typically dual-sided, annular disk-shaped precursor substrates (such as substrate  2  of  FIG. 1 , described in detail supra) for hard disk magnetic recording media, enter the illustrated portion of apparatus  20  at inlet chamber  27  after receiving antecedent processing in a plurality of downstream processing chambers or stations (not shown in the drawing for illustrative simplicity), e.g., for deposition of an adhesion layer, a soft magnetic underlayer, and a non-magnetic interlayer (corresponding to the layers respectively identified by reference numerals  2 A,  3 , and  4  in  FIG. 1  and described in detail supra) on both surfaces thereof, and are transported to the first sputter deposition chamber or station  21 , wherein a perpendicular hard magnetic recording layer (corresponding to layer  5  in  FIG. 1 ), e.g., a Co-based alloy Cr segregation-type magnetic layer or a Co-based alloy granular-type magnetic layer (as described in detail supra) is formed on the non-magnetic interlayer(s)  4  by an appropriate sputter deposition process (i.e., with substrate heating when forming a Cr segregation-type magnetic layer  5  and by reactive sputtering, without substrate heating, in an O 2  and/or N 2  containing atmosphere when forming a granular-type magnetic layer  5 ).  
         [0049]     Following deposition of a selected perpendicular hard magnetic recording layer  5  of appropriate thickness on the surface(s) of the precursor substrates  25  in the first sputter deposition chamber or station  21 , the substrates are transported, via buffer/isolation chamber  26 ′ and associated gates G, to chamber  28  for performing a thermal oxidation of the surface of the perpendicular hard magnetic recording layer(s)  5  on the substrates/workpieces  25 . According to the invention, oxygen (O 2 ) gas, or O 2  gas in admixture with one ore more inert gases, e.g., Ar, Kr, and/or Xe, is flowed past the surface(s) of the substrates/workpieces  25  via inlet conduits  30 ,  30 ′ and outlet conduits  31 ,  31 ′ located on opposite side walls of chamber  28 , while the substrates/workpieces are maintained at a desired elevated temperature in the range from about 50 to about 300° C., preferably about 150° C., by means of heating elements  29 ,  29 ′. Typical O 2  gas pressures, whether pure O 2  gas, or O 2  gas in admixture with at least one inert gas, is supplied to chamber  28 , range from about 1 to about 50 mTorr, preferably about 30 mTorr, at flow rates ranging from about 5 to about 100 sccm, preferably about 30 sccm. The combination of O 2  pressure, flow rate, and substrate temperature in chamber  28  is selected to provide formation of a surface oxide layer of desired thickness, e.g., from about 2 to about 100 Å, preferably about 10 Å, at a continuous transport rate of the substrates/workpieces  25  through chamber  28  (which determines the residence time, or treatment interval, of substrates/workpieces  25  transported through chamber  28 ) which is consistent (i.e., substantially equal to) with the typical continuous transport rates of substrates/workpieces  25  through the various chambers or stations of apparatus  20  in the absence of chamber  28 , e.g., in the range from about 1 to about 100 cm/sec., preferably about 5 cm/sec.  
         [0050]     Following formation of the surface oxide layer(s) in chamber  28 , the substrates/workpieces  25  are transported, via buffer/isolation chamber  26 ″ and associated gates G, to the second sputter deposition chamber or station  22 , where a protective overcoat layer (corresponding to the layer identified by reference numeral  11  in  FIG. 1  and described in detail supra) is formed over the surface-oxidized perpendicular hard magnetic recording layer(s)  5 , as by sputtering of a carbon (C)-based layer, e.g., diamond-like carbon (DLC). The thus-constituted substrates/workpieces  25  are then transported, via outlet buffer/isolation chamber  26 ′″ and associated gates G, to chamber  27 ′, for withdrawal from apparatus  20  or for further processing therein, e.g., for deposition thereon of a lubricant topcoat layer (corresponding to the layer identified by reference numeral  12  in  FIG. 1  and described in detail supra), e.g., deposition of a perfluoropolyether compound by means of dipping or vapor deposition.  
         [0051]     In summary, the present invention provides means and methodology for continuous, automated fabrication of high areal density, high performane perpendicular magnetic recording media requiring formation of a surface oxide layer on the perpendicular hard magnetic recording layer, at product throughputs compatible with the requirements for cost-effective manufacture of such media, while maintaining full compatibility with all aspects of such automated manufacture. The present invention advantageously eliminates the previous requirement for removal of the media precursors from the manufacturing apparatus for oxide layer formation in the ambient atmosphere and re-installation of the oxidized media in the same or a different manufacturing apparatus for subsequent processing/treatment. Moreover, the relatively shorter duration of the inventive thermal oxidation treatment materially shortens the manufacturing time of the media, vis-à-vis conventional ambient atmosphere processing for oxidation of the surface of the perpendicular magnetic recording layer.  
         [0052]     Finally, the inventive thermal oxidation treatment technique can be utilized with any type of magnetic recording media, regardless of the materials used for the substrate, adhesion layer, soft magnetic underlayer(s), interlayer(s), and recording layer(s). As indicated above, the thermal oxidation process parameters and duration are preferably optimized according to the media design and the particular continuous manufacturing apparatus utilized for the treatment to obtain the maximum benefit of the inventive methodology.  
         [0053]     In the previous description, numerous specific details are set forth, such as specific materials, structures, processes, etc., in order to provide a better understanding of the present invention. However, the present invention can be practiced without resorting to the details specifically set forth. In other instances, well-known processing materials and techniques have not been described in detail in order not to unnecessarily obscure the present invention.  
         [0054]     Only the preferred embodiments of the present invention and but a few examples of its versatility are shown and described in the present disclosure. It is to be understood that the present invention is capable of use in various other combinations and environments and is susceptible of changes and/or modifications within the scope of the inventive concept as expressed herein.