Abstract:
A sputtering system including a vacuum chamber, at least one cathode located in said vacuum chamber, a first gas introduction mechanism for supplying a gas along a surface of the cathode, which first gas introduction mechanism is located in the vacuum chamber and provided through the at least one cathode, a second gas introduction mechanism for supplying a gas along a surface of the at least one cathode, which second gas introduction mechanism is located in the vacuum chamber and provided around the at least one cathode, a third gas introduction mechanism for supplying a gas into the vacuum chamber, which third gas introduction mechanism has gas supply inlets positioned at a location radially outside of said second gas introduction mechanism and above said at least one cathode, and a vacuum evacuation unit for evacuating the inside of said vacuum chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 10/852,148, filed on May 25, 2004, and which claims the priority of Japanese Patent Application No. 2003-147529, filed in Japan on May 26, 2003. The contents of U.S. patent application Ser. No. 10/852,148 and Japanese Patent Application No. 2003-147529 are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a sputtering system, and more particularly to a sputtering system using a reactive gas to deposit a film on a substrate by reactive sputtering. 
         [0004]    2. Description of the Related Art 
         [0005]    In a sputtering system, the material of a target attached to a cathode is stripped off by ions to form target material particles (sputter particles) which in turn are supplied onto substrate facing the target so as to form a thin film of the target material on the substrate. Therefore, in the sputtering system, the gas for causing sputtering in a vacuum chamber, such as a sputter gas or plasma generating gas, is introduced into a vacuum chamber, and the target is supplied with a high frequency power or supplied with a DC voltage. Thereby, in the vacuum chamber, required energy is given to generate plasma and ions for producing the sputter particles are produced. The sputter particles strike the surface of the substrate and the target material is deposited on the surface of the substrate. 
         [0006]    In the above sputtering systems a reactive sputtering system has been known. In the reactive sputtering system, the vacuum chamber is filled with a reactive gas such as oxygen or nitrogen together with an inert gas (or sputter gas) such an argon (Ar) gas. In the reactive sputtering system, for example, the argon ions produced in the plasma strike the target material to strip off particles of the target material. The particles of the target material react with the reactive gas, and as a result the reaction product is deposited on the surface of the substrate to make a film thereon. If the concentration of the reactive gas is high, the reactive gas makes a compound layer on the surface of the target material. With the sputtering of the compound layer, a reaction product having a desired composition is deposited on the substrate. 
         [0007]    On the other hand, for example, in order to form a magnetic recording medium on a substrate, it is necessary to form a multi-layer film on the substrate, which is formed by successively stacking various metal films, or oxide films or nitride films of metal material. In this magnetic recording medium, uniformity of thickness, quality, and uniformity of the magnetic characteristics etc. of the film are requested. In particular, in a hard disk etc., uniformity of the magnetic characteristics in the circumferential direction and radial direction of the substrate (in the case of a longitudinal recording medium), or uniformity of the magnetic characteristics in the perpendicular direction of the substrate (in the case of a perpendicular recording medium) is strongly requested. 
         [0008]    When using the above-mentioned reactive sputtering system utilizing a reactive gas etc. to form a multilayer film on the substrate and create a magnetic recording medium, achievement of the desired uniformity of thickness and quality and uniformity of magnetic characteristics is difficult. Next, the basic configuration of the reactive sputtering system of the related art will be explained with reference to  FIG. 16  and  FIG. 17  so as to explain the problems. 
         [0009]      FIG. 16  shows a vertical type reactive sputtering system. The walls of a vacuum chamber  101  of the reactive sputtering system are provided with, for example, at least cathodes  104  and  105  respectively provided with one target  102  and  103  and arranged facing each other in a coaxial state. A substrate  106  is arranged in a vertical state at a position of equal distances from the surfaces of the targets  102  and  103 . The substrate  106  is held by a substrate support plate  107 . The substrate  106  may be in a stationary state or a rotating state or may be in a moving state. 
         [0010]    As the gas for generating the sputter plasma, in particular, in the case of reactive sputtering, a mixed gas  108  including an argon gas (Ar) and a reactive gas is introduced from a gas introduction part  109  at the ceiling of the vacuum chamber  101 . The introduced mixed gas moves as shown by the arrows  110  and is exhausted from an exhaust part  111  at the floor. In this gas introduction method, the reactive gas is consumed mainly at the gas upstream region, so the reactive gas does not sufficiently reach the entire surfaces of the targets  102  and  103 , the distributions of the concentration of the reactive gas on the target surfaces become uneven, and the characteristics of the reactive films deposited on the substrate  106  become uneven or are ruined. 
         [0011]      FIG. 17  shows a horizontal type reactive sputtering system. In this reactive sputtering system, a cathode  122  provided with a single target  121  is arranged in a horizontal state on the floor of a vacuum chamber  101 , while a substrate  123  is placed horizontally at a position a predetermined distance from the surface of the target  121 . As the gas for producing the sputter plasma, the above mixed gas is introduced from a gas introduction part  124  at the left wall of the vacuum chamber  101  in the figure. The introduced mixed gas travels as shown by the arrows  125  and is exhausted from an exhaust part  126  at the right wall. In this reactive sputtering system as well, the reactive gas is consumed at the gas upstream region, so the reactive gas does not sufficiently reach the entire surface of the target  121 , the distribution of the concentration of the reactive gas on the target surface becomes uneven, and the characteristics of the reactive film deposited on the substrate  123  become uneven or are ruined. 
         [0012]    As explained above, in a sputtering system forming a film by sputtering while introducing a reactive gas into a vacuum chamber to create a flow of reactive gas, the reactive gas is consumed at the upstream part of the flow of the reactive gas, the reactive gas does not sufficiently reach the entire surface of the target, the distribution of the concentration of the reactive gas on the target surface becomes uneven, and the characteristics of the reactive film deposited on the substrate become uneven. 
         [0013]    Therefore, to solve this problem in a reactive sputtering system, in the related art, several proposals have been made as outlined below. 
         [0014]    Japanese Patent Publication (A) No. 5-320891 discloses a sputtering system according to which, in a first aspect of the invention, the target material is formed with a plurality of small holes to which gas introduction pipes are connected and, in a second aspect of the invention, insertion members are provided to divide the target material and the insertion members are formed with a plurality of small holes to which gas introduction pipes are connected. Due to these structures, sputter gas including reactive gas is introduced toward the substrate facing the target. Japanese Patent Publication (A) No. 2001-337437 discloses a target structure in which the target material is formed with a plurality of small holes and sputter gas including the reactive gas is introduced toward the substrate facing the target. Japanese Patent Publication (A) No. 2002-269858 discloses a sputtering system in which an inner circumferential mask covering the inner circumference of a substrate is formed with gas introduction paths and gas blowing ports and the gas introduction paths etc. are utilized to introduce the reactive gas to the surface of a substrate. Japanese Patent Publication (A) No. 5-148634 discloses a sputtering system in which argon gas and a reactive gas are introduced to a target by a gas pipe positioned at the outer circumference and a gas pipe positioned at the inner circumference. Japanese Patent Publication (A) No. 10-280139 discloses a sputtering system in which gas for producing the plasma is introduced from a gas blowing passage arranged at the circumference of the target. 
         [0015]    In each of the systems of Japanese Patent Publication (A) No. 5-320891, Japanese Patent Publication (A) No. 2001-337437, Japanese Patent Publication (A) No. 5-148634, and Japanese Patent Publication (A) No. 10-280139, sometimes a sufficient uniformity of the reactive gas cannot be obtained depending on the exhaust state. The system of Japanese Patent Publication (A) No. 2002-269858 is provided with a gas introduction part at a structural part of the substrate holder facing the target, so movement of the substrate holder is difficult. Further, the inner circumference mask is moved each time a substrate is detached and attached, so generates dust. The problem therefore arises of a shorter maintenance cycle. 
         [0016]    While various means have been devised in the related art as explained above so as to enable the deposition of a film of a uniform quality on a substrate surface, the above problems have not been completely solved. These means are therefore insufficient. Obtaining uniform properties of the reactive film is extremely difficult. In particular, in a magnetic recording medium, deterioration of the longitudinal distribution of the film properties is caused due to the change in composition of the reaction film such as the nitride film of the multilayer film structure and has a major effect on the magnetic properties of the medium. 
       OBJECTS AND SUMMARY 
       [0017]    An object of the present invention is to provide a sputtering system which introduces a sputter gas and reactive gas into the vacuum chamber and forms a film by reactive sputtering wherein the concentration of the reactive gas flowing along the surface of the target is made substantially uniform to raise the uniformity of the reaction between the reactive gas and target and therefore enable greater uniformity of the thickness, quality, and properties of the film. 
         [0018]    The sputtering system according to a first aspect of the invention is a sputtering system arranging a cathode provided with a target so as to face a substrate and sputtering the target by reactive sputtering so as to deposit a film on the substrate and is provided with a gas introduction mechanism (center gas introduction mechanism) for making at least the reactive gas flow from the center of a cathode unit along the surface of the target to the outsides. More particularly, it is provided with a vacuum chamber into which a substrate is loaded, at least one cathode unit provided in the vacuum chamber so as to face the substrate and including a cathode with a target, a power source for supplying power to the cathode of the cathode unit, a vacuum evacuation system for evacuating the inside of the vacuum chamber to a vacuum, and a gas introduction mechanism for making reactive gas flow from a center of the cathode unit along the surface of the target to the outsides. 
         [0019]    In the above configuration, the flow of gas is kept from dispersing in the inside of the vacuum chamber as a whole and a path of flow is formed near the surface of the target. It therefore becomes possible to obtain a uniform concentration of at least the reactive gas at the surface of the target. 
         [0020]    Preferably, the cathode unit is structured with one target attached to one cathode in a coaxial relationship and the reactive gas flows from a center of the target toward the outer circumference of the target along the surface of the target. 
         [0021]    Alternatively, the cathode unit is structured with a plurality of cathode sets each comprised of a cathode and target and the plurality of cathode sets are arranged off-axis around the center of the cathode unit. 
         [0022]    The sputtering system according to a second aspect of the present invention is a sputtering system which arranges cathodes provided with targets to face a substrate and sputters the target by reactive sputtering to deposit a film on the substrate. It is provided with a cathode unit structured provided with a plurality of cathode sets each comprised of a cathode and target. The plurality of cathode sets are arranged off-axis around the center of the cathode unit. A gas introduction mechanism is provided for making at least reactive gas flow from a center of each cathode set toward its periphery along the surface of said target. More specifically, it is provided with a vacuum chamber into which a substrate is loaded, a cathode unit provided in the vacuum chamber so as to face the substrate and structured provided with a plurality of cathode sets each comprised of a cathode and a target, a power source for supplying power to the cathodes of the cathode unit, and a vacuum evacuation system for evacuating the inside of the vacuum chamber to a vacuum. 
         [0023]    Preferably, the gas introduction mechanism includes an introduction hole for introducing the reactive gas and a gas dispersion member for dispersing the introduced reactive gas. 
         [0024]    Preferably, the system is further provided with a covering member surrounding a target and having a part opening toward the substrate. 
         [0025]    Preferably, the system is further provided with a passage selecting unit (vane member) for selectively passing target material particles moving from a target to the substrate. 
         [0026]    More preferably, the passage selecting unit is provided between the target and the substrate to be able to rotate in a coaxial relationship with the substrate. 
         [0027]    Preferably, the system is further provided with, along with the gas introduction mechanism for making the reactive gas flow along the surface of a target toward the outside, another gas introduction mechanism for making reactive gas flow from the outer circumference of a cathode along the surface of the target toward the inside. Due to this configuration, it is possible to obtain a uniform concentration of the reactive gas at the surface of a target more effectively without regard as to the position of arrangement of the exhaust port. 
         [0028]    Note that the sputtering system according to the present invention can also be configured with a plurality of targets attached around the center of a cathode and with the centers of the targets rotating around a circle coaxial with the center of the cathode. 
         [0029]    The present invention preferably gives the following effects: It provides a system for sputtering for forming a film on a substrate, in particular for sputtering a target by reactive sputtering to deposit a film on a substrate, wherein a gas introduction mechanism is provided for making at least the reactive gas flow from the center of a cathode unit along the surface of a target toward the outsides and therefore the concentration of the reactive gas becomes substantially uniform over the entire surface of the target and the thickness, quality, and properties of the film deposited on the substrate can be made uniform. 
         [0030]    Further, since at least the reactive gas is introduced from a gas introduction mechanism provided at the position of the center of a cathode (the center of the target when the cathode and target are in a coaxial positional relationship) and a flow of gas along the surface of the target is formed, the concentration of the reactive gas becomes uniform over the entire surface of the target and as a result the thickness, quality, and properties of the film deposited on the substrate can be made uniform. 
         [0031]    Further, since a covering member is provided, the flow of reactive gas over the surface of a target can be made close to the surface of the target and follow along the surface of the target. 
         [0032]    Further, since a passage selecting unit is provided for selectively passing the target material particles traveling from a target to the substrate and the passage selecting unit is made to rotate, it is possible to make the flow of reactive gas be close to the surface of the target and follow along the surface of the target and therefore form a more uniform concentration of reactive gas at the target surface. 
         [0033]    Further, since an outer circumference gas introduction mechanism is provided to introduce reactive gas from the outer circumference of a target as well, the concentration of reactive gas at the target surface can be made more uniform. 
         [0034]    Due to the above, the properties of the reactive film formed on the substrate become more uniform, the variations in magnetic properties of a magnetic recording medium comprised of a multilayer film using this can be reduced, and the yield of the production process of the media can be improved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein: 
           [0036]      FIG. 1  is a horizontal sectional view of a vacuum chamber showing the general configuration of a sputtering system according to an embodiment of the present invention; 
           [0037]      FIG. 2  is a sectional view along the line A-A in  FIG. 1 ; 
           [0038]      FIG. 3  is a view similar to  FIG. 2  showing the principal configuration of a sputtering system according to a first embodiment of the present invention; 
           [0039]      FIG. 4  is a perspective view in the direction B in  FIG. 3 ; 
           [0040]      FIG. 5  is a view similar to  FIG. 2  showing the principal configuration of a sputtering system according to a second embodiment of the present invention; 
           [0041]      FIG. 6  is a perspective view in the direction B in  FIG. 5 ; 
           [0042]      FIG. 7  is a perspective view of a vane member; 
           [0043]      FIG. 8  is a view similar to  FIG. 2  showing the principal configuration of a sputtering system according to a third embodiment of the present invention; 
           [0044]      FIG. 9  is a front view of the relationship between a cathode, target, and vane member in the configuration of the third embodiment; 
           [0045]      FIG. 10A  shows the principal configuration of a first modification of the third embodiment and is a front view of a cathode unit; 
           [0046]      FIG. 10B  is a vertical sectional view of the characterizing configuration of the first modification of the third embodiment; 
           [0047]      FIG. 11A  shows the principal configuration of a second modification of the third embodiment and is a front view of a cathode unit; 
           [0048]      FIG. 11B  is a sectional view along the line D-D of  FIG. 11A ; 
           [0049]      FIG. 12A  shows the principal configuration of a third modification of the third embodiment and is a front view of a cathode unit; 
           [0050]      FIG. 12B  is a sectional view along the line E-E of  FIG. 12A ; 
           [0051]      FIG. 13  is a vertical sectional view of the principal configuration of a sputtering system according to a fourth embodiment of the present invention; 
           [0052]      FIG. 14  is a vertical sectional view of the principal configuration of a sputtering system according to a fifth embodiment of the present invention; 
           [0053]      FIG. 15A  is a vertical sectional view for explaining a first example of the method of flow of a gas in a reactive gas introduction mechanism; 
           [0054]      FIG. 15B  is a vertical sectional view for explaining a second example of the method of flow of a gas in a reactive gas introduction mechanism; 
           [0055]      FIG. 16  is a horizontal sectional view of a sputtering system of the related art; and 
           [0056]      FIG. 17  is a vertical sectional view of another sputtering system of the related art. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0057]    Preferred embodiments of the present invention will be described in detail below while referring to the attached figures. 
         [0058]    An exemplary structure of a vacuum chamber of a sputtering system according to the present invention will be explained in brief first based on  FIG. 1  and  FIG. 2 . The sputtering system is a vertical reactive sputtering system. Note that in  FIG. 1  and  FIG. 2 , the wall part etc. of the vacuum chamber are illustrated generally by simple lines. 
         [0059]    In the sputtering system  10 , substrates  12  on which films are to be formed are arranged in vertical states inside the vacuum chamber  11 . The substrates  12  are preferably arranged so that their two surfaces are vertical. The substrates  12  are for example ring shapes formed overall as thin disks with holes at their centers. Substrates  12  arranged in the vertical state, as shown in  FIG. 2 , are kept in their vertical postures by substrate support plates (substrate holders)  13  arranged vertically. The substrate support plates  13  or substrates  12  may be in a stationary state or a rotating state or a state able to move while being transported by a rail transport mechanism at their bottoms. 
         [0060]    As shown in  FIG. 2 , left and right side walls  11   a  and  11   b  positioned at the two sides of the substrates  12  are provided with cathode units  14  in vertical states. In  FIG. 1  and  FIG. 2 , the cathode units  14  are shown by hatched blocks. In  FIG. 2 , when forming films at the two surfaces of the substrates  12 , the inside space (vacuum chamber) of the vacuum chamber  11  is evacuated to a required vacuum by a vacuum exhaust system  15  for evacuation from for example the floor part. Further, the substrates  12  on which the films are to be formed are held at the positions shown in  FIG. 1  and  FIG. 2  by substrate support plates  13 . 
         [0061]    Here, the actual structure of a “cathode unit” will be explained. A “cathode unit” includes one or more cathodes and attaches a target to the vacuum chamber side surface of each cathode. In principle, one cathode has one target attached to it. The set of one cathode and one target will be referred to as a “cathode set” in this specification. In a cathode set, the target and cathode are in a coaxial positional relationship and therefore the center of the target and the center of the cathode are in register. 
         [0062]    When the cathode unit  14  includes a single cathode, that cathode is provided with a single target in a coaxial positional relationship and therefore one cathode set is included. In this example of the configuration, the center of the target, the center of the cathode, and the center of the cathode set are all in register. 
         [0063]    Further, when the cathode unit  14  includes for example three cathodes, each of the three cathodes is provided with a single target in a coaxial positional relationship and therefore three cathode sets are arranged offset in position by angles of 120 degrees on a for example disk shaped mounting member. In this example of the configuration, the centers of the targets and the centers of the cathodes of the cathode sets are in register, but are offset in position in positional relationship with the center of the cathode unit. 
         [0064]    Note that a cathode unit  14  is shaped overall as a disk shape or ring shape and has an axial center. 
         [0065]    The inside of the vacuum chamber  11  of the above reactive sputtering system  10  is filled with argon (Ar) or another inert gas for sputtering (sputter gas or plasma generating gas) and oxygen, nitrogen, or another reactive gas so as to form a plasma for sputtering the targets. The inert gas and reactive gas may be introduced together as a mixed gas or may be introduced independently separately. The configuration of the gas introduction mechanism is suitably selected in accordance with the method of introduction. In  FIG. 1  and  FIG. 2 , illustration of the gas introduction mechanism is omitted. Further, each cathode unit  14  is connected to a power source  16  for supplying predetermined voltage to the cathodes for sputtering of the target. Usually, a power source  16  is provided for each target, that is, for each cathode. 
         [0066]    According to  FIG. 1 , for example two substrates  12  are arranged in the vacuum chamber  11 . By providing cathode units  14  at positions to the left and right of the two substrates, a total of four cathode units  14  are provided in the chamber as a whole. The substrates  12  are arranged at substantially the same distances from the left and right cathode units  14 . The substrates  12  and the left and right cathode units  14  are provided between them with covering members  17  covering the targets of the cathode units  14  and having openings  17   a  at parts facing the surfaces of the substrates  12 . The covering members are illustrated by line drawings, but for example are ring-shaped members similar to shallow bottom pans or dishes. 
         [0067]    The inside of the vacuum chamber  11  of the sputtering system  10  is filled with Ar etc. and a reactive gas for sputtering as explained above. In the present invention, the method of introducing the reactive gas is important in relation to the targets in the vacuum chamber  11 , so in this embodiment, the gas introduction mechanism for the reactive gas and the method of introduction of the reactive gas (the method of flow or method of blowing the reactive gas in the vacuum chamber) will be explained in detail below. In this embodiment, a configuration where the reactive gas and the sputter gas are introduced mixed together is assumed. Therefore, the flow of the reactive gas and the flow of the sputter gas in the vacuum chamber  11  are the same. In the following explanation, the explanation will be given focusing on the introduction and flow of the reactive gas. Note that it is also possible to provide another gas introduction mechanism and introduce the reactive gas separately from the sputter gas. 
         [0068]    To evacuate the inside of the vacuum chamber  11  to a required vacuum or to exhaust the gas introduced into the vacuum chamber  11  outside of the vacuum chamber, as shown in  FIG. 2 , a vacuum evacuation system  15  is provided under the vacuum chamber  11 . The vacuum evacuation system  15  evacuates the inside of the vacuum chamber or exhausts the gas through a valve  18  provided at the floor of the vacuum chamber  11 . The vacuum chamber  11  of this sputtering system  10  is structured to draw out the gas from the bottom. Further, as shown in  FIG. 2 , each covering member  17  is provided above it with a horizontal inside wall  19 , whereby a space  20  for escape of gas introduced into the vacuum chamber is formed. In the illustrated example, each covering member  17  is fixed to an inside wall  19 . 
         [0069]    Next, a first embodiment of the present invention relating to the vacuum chamber  11  of a sputtering system  10  having the above structure will be explained with reference to  FIG. 3  and  FIG. 4 .  FIG. 3  is a sectional view along the line A-A in the same way as  FIG. 2  and shows the more detailed structure for a specific system.  FIG. 3  shows the detailed structure of the parts of the cathode units  14  and the method of introduction and flow of the reactive gas.  FIG. 4  is a perspective view in the direction B in  FIG. 3  and shows parts of a cathode unit  14 , that is, the front shapes of the cathode and target. In  FIG. 3 , elements substantially the same as elements explained in  FIG. 1  and  FIG. 2  are assigned the same notations. 
         [0070]    In  FIG. 3 , a target  22  is attached to the front surface of the vacuum chamber side of the cathode  21  of each cathode unit  14 . As shown in  FIG. 4 , the cathode  21  and the target  22  are substantially the same in shape, for example, have ring shapes, and are formed with holes at their centers. Each target  22  is fixed to a cathode  21  in a coaxial positional relationship. Each cathode  21  is supplied with a required voltage as explained in  FIG. 2  etc. Further, in this embodiment, each cathode  21  and target  22  are fixed to a side wall of the vacuum chamber  11 . 
         [0071]    The center hole of each cathode  21  and the center hole of each target  22  are connected to a reactive gas feed system  23  (for introducing a mixed gas with argon gas or another sputter gas, hereinafter referred to as a “reactive gas feed system”) through a not shown gas pipe. In  FIG. 3 , the arrows  24  show the flow of reactive gas fed from reactive gas feed system  23  to the inside of the vacuum chamber  11 . 
         [0072]    In the vacuum chamber  11 , a part for introduction of the reactive gas (blowing part) constituted by the reactive gas introduction mechanism is provided at the center of each target. This reaction gas introduction mechanism is comprised of the center holes (gas introduction holes) of the coaxial cathode  21  and target  22 , a gas dispersion member  25  arranged at a position coaxial with the target  22 , and a gas introduction port formed between the gas dispersion member  25  and the inner surface of the center hole of the target  22 . 
         [0073]    The gas dispersion member  25  is arranged at a distance from the target  22  of an extent not causing electrodischarge, for example, a gap of about 2 to 3 mm. In  FIG. 3 , the gas dispersion member  25  is arranged fixed by a not shown fixing member for example. However, the arrangement of the gas dispersion member  25  is not limited to a fixed arrangement. The gas dispersion member  25  is provided with a small diameter shaft and a large diameter dispersion part (enlarged diameter part). The dispersion part of the gas dispersion member  25  is provided in a positional relationship blocking the wide part of the inside opening of the center hole of the target  22 . The gap between the gas dispersion member  25  and the inside surface of the center hole of the target  22  forms a passage for flow of the reactive gas. Gas introduced from the gas introduction port around the gas dispersion member  25  strikes the dispersion part of the gas dispersion member  25  to be blown out to the sides changed in direction and flows evenly from the center to the outer circumference (peripheral edges) along the surface of the target  2  as shown by the arrows  26 . 
         [0074]    In the state with the reactive gas blown out evenly along the surface of the target  22  in this way, a not shown high frequency or DC voltage is applied to the cathode  21  to cause the generation of plasma. Due to this, sputter particles (target material particles) sputtered from the target  22  react with the reactive gas, whereby a desired reactive film is deposited on the substrate  12 . 
         [0075]    When separately introducing argon gas or another sputter gas and the reactive gas, the reactive gas is introduced from the reactive gas feed system  23  at the center of a cathode or target as explained above, but the sputter gas may also be introduced from any other part of the vacuum chamber. For example, it may be introduced from above the vacuum chamber or from the outer circumference of the cathode or target. Further, as explained later, the gas introduced from the outer circumference of the cathode or target may be made a mixed gas with a reactive gas. 
         [0076]    In the above, preferably a main flow of gas ( 26 ) is formed near the surface of the target  22  facing each substrate  12  and is kept from dispersing to the substrate  12  side by making the top (dispersion part) of the gas dispersion member  25  stick out to the inside of the vacuum chamber from the plane including the surface of the target  22 . Further, preferably the head is made large in diameter and is formed as an enlarged diameter part as explained above. 
         [0077]    Each target  22  is surrounded by a covering member  17 . The size of the covering member  17  and the distances between the covering member  17  and the target  22  and substrate  12  are suitably set so that mainly a flow of gas near the surface of the target  22  and a flow of gas from near the surface are effectively formed and exhausted. In  FIG. 3 , the reactive gas introduced from the introduction mechanism to the inside of the vacuum chamber through the reactive gas introduction mechanism, as shown by the arrows  26 , flows above to the space  20  and is exhausted below to the outside of the vacuum chamber as shown by the arrows  27  through the hole part corresponding to the valve  18 . 
         [0078]    In the above configuration using covering members  17 , it is possible to prevent sputter particles from traveling to other locations in the vacuum chamber, but synergistically it is possible to effectively form a flow of reactive gas near the surface of each target. 
         [0079]    Note that the top of the gas dispersion member  25  does not necessarily have to stick out from the plane including the surface of each target  22 . 
         [0080]    According to the first embodiment, a reactive gas introduction mechanism can be used to form an even flow of the reactive gas along the surface of a target  22  from its center to the outer circumference as shown by the arrows  26 , so the concentration of the reactive gas flowing along the surface of the target can be made uniform, the uniformity of the reaction between the reactive gas and target can be made uniform, the uniformity of the reaction between the reactive gas and the target is improved, and the thickness, quality, and characteristics of the film deposited on each substrate  12  can be made uniform. 
         [0081]    A sputtering system according to a second embodiment of the present invention is shown below in  FIG. 5  to  FIG. 7 . If a vane member  31  having a plurality of (for example, nine) vanes  31   a  extending in a radial manner at equal intervals as shown in  FIG. 7  is coaxially and rotatably attached to a cylindrical gas dispersion member  25  of the reactive gas introduction mechanism and that vane member  31  is made to rotate, the concentration of the reactive gas over the surface of the target can be made uniform more effectively and a uniform reactive film can be formed on the substrate.  FIG. 5  is a view similar to  FIG. 3  of a sputtering system with the vane member  31  attached, while  FIG. 6  is a view similar to  FIG. 4  of a sputtering system with the vane member  31  attached. In  FIG. 5  and  FIG. 6 , elements substantially the same as elements explained in the first embodiment are assigned the same notations and detailed explanations are omitted. 
         [0082]    In the above, the gas dispersion member  25  shown in  FIG. 3  was formed by for example a solid member and was provided fixed in place. As opposed to this, the gas dispersion member  25  shown in  FIG. 5  is formed by a hollow member having a cylindrical shaft and fixed in place so as to allow passage of the shaft of the vane member  31 . Further, the gas dispersion member  25  can be provided so as to be able to be rotated by a not shown rotation drive mechanism and the top of the gas dispersion member  25  may be provided with the vane member  31  fixed in place by welding etc. in a projecting state. With this configuration, the two members are together rotatable. Note that in this case, it is also possible to provide the vane member  31  at the top of the gas dispersion member  25  in a detachable manner. When detaching the vane member  31 , the gas dispersion member  25  is preferably used held in a state not allowing rotation. 
         [0083]    The vane member  31  is driven to rotate by being linked with a rotational gear mechanism provided outside of the vacuum chamber  11 . Further, the vane member  31  can be either independent of or integral with the reactive gas introduction mechanism and can freely rotate. The vane member  31  is a means for selectively passing target member particles traveling from a target to the substrate. A plurality of axially symmetric open regions are formed by the spaces formed between the vanes. The detailed configuration of the vane member  31  is disclosed in for example Japanese Patent Application No. 2001-262108 (Japanese Patent Publication (A) No. 2003-73825) of the same assignee as the present invention. 
         [0084]    If utilizing a sputtering system having the configuration of the first or second embodiment to deposit a nitride film of a CrNb alloy, a Cr alloy, a Co-based film, and a protective film on a glass substrate to prepare a longitudinal magnetic recording medium, the Hc, one of the magnetic properties, of the longitudinal magnetic recording medium becomes ±2.5%. As opposed to this, if utilizing the conventional system of  FIG. 12  to produce a magnetic recording medium of the same film configuration, the Hc becomes ±45.7%. Therefore, the present invention enables a great improvement. This is believed due to the fact that the concentration of nitrogen gas over the CrNb target surface becomes uniform and therefore the quality of the CrNb nitride film in the multilayer film configuration becomes uniform and the magnetic properties of the device are improved. 
         [0085]    The sputtering system according to the present embodiment can be used for both “longitudinal” and “perpendicular” magnetic recording media depending on the provision of the vane member  31 . Note that the invention is not however limited to a magnetic recording medium and can of course also be applied to production of an ordinary reactive sputter film. 
         [0086]    Next, a third embodiment of a sputtering system according to the present invention will be explained with reference to  FIG. 8  and  FIG. 9 .  FIG. 8  corresponds to the above  FIG. 3 , while  FIG. 9  corresponds to the above  FIG. 4  in relation to the part of the cathode unit. Note that a sectional view of the part of the cathode unit in  FIG. 8  is given by the sectional view along the line C-C in  FIG. 9 . Note that in  FIG. 8  and  FIG. 9 , elements substantially the same as elements explained in the first or second embodiment are assigned the same notations. 
         [0087]    In the third embodiment, a plurality of targets  41  are arranged in an off-axis relationship from the shaft (center part)  40 . For example, as shown in  FIG. 9 , three targets  41  having disk shapes are attached. At the back sides of the three targets  41 , cathodes  42  having substantially the same diameters as the targets  41  are provided. The cathode sets  43  comprised of the targets  41  and the cathodes  42  are preferably fixed to a disk shaped mounting member  44 . In the disk shaped mounting member  44 , as shown in  FIG. 9 , the three cathode sets  43  are arranged around the center part  40  of the mounting member  44  at angular intervals of for example 120 degrees. In  FIG. 9 , only the arrangement of the targets  41  at the disk shaped mounting member  44  is shown. Each of the three targets  41  is attached with its center part offset from the center part  40  of the mounting member  44 , that is, in an off-axis state. 
         [0088]    A cathode unit  14  of the third embodiment is comprised of three cathode sets  43  and the disk shaped mounting member  44  to which these are fixed based on the above positional relationship. 
         [0089]    In this embodiment, the reactive gas, as shown by the arrows  24 , is introduced through a hole formed at the center part of the cathode unit  14  and, as shown by the arrows  26 , flows from the center part of the cathode unit  14  toward the outer periphery of the cathode unit  14  in the radial direction. 
         [0090]    In this embodiment, by making the mounting member  44 , that is, the cathode unit as a whole, a rotatable structure, the three targets  41  are made to rotate around the center part  40 . In  FIG. 8 , illustration of the mechanism for rotating the disk shaped mounting member  44  is omitted, but one example of this mechanism is disclosed in Japanese Patent Application No. 2000-278962 of the same assignee as this application. 
         [0091]    Further, in this embodiment as well, the above-mentioned vane member  31  is provided. In the case of this embodiment, the vane member  31  is fixed projecting out at the top of the gas dispersion member  25 . The gas dispersion member  25  and the vane member  31  are made to rotate by a not shown rotation drive mechanism. 
         [0092]    The shaft  40  of the disk shaped mounting member  44 , that is, the cathode unit  14 , is provided with the above-mentioned gas introduction mechanism for the reactive gas. The gas introduction mechanism is configured by an introduction hole for introducing the reactive gas and a gas dispersion member  25 . The above covering member  17  may also be omitted and, instead, a top inner wall  45  forming a space  20  may be provided. Note that it is also possible to provide the covering member  17 . The rest of the configuration is the same as the above-explained embodiments. The third embodiment as well can give effects the same as the above embodiments. 
         [0093]    In the third embodiment, the number of the off-axis targets  41  is not limited to three. It is sufficient that there be at least one. Further, the targets  41  do not have to be disk shapes and may also be ring shapes with holes at their centers. 
         [0094]    The mechanical part comprised of the gas dispersion member  25  and the vane member  31  may also be provided in a fixed fashion. Even with this configuration, since a structure making the cathode unit side rotate is employed, the vane member  31  and the three targets  41  change in relative positions, so it is possible to selectively pass target material particles traveling from a target to the substrate. 
         [0095]    Modifications of the third embodiment will be explained next with reference to  FIGS. 10A and 10B  to  FIGS. 12A and 12B . In the figures,  FIGS. 10A ,  11 A, and  12 A are similar to  FIG. 9  showing the front view of a cathode unit  14 , while  FIGS. 10B ,  11 B, and  12 B are cross-sectional views setting cross-sections so that the characterizing parts in  FIGS. 10A ,  11 A, and  12 A are shown. 
         [0096]    In the modification of  FIGS. 10A and 10B , partition plates  46  are arranged between each two of the three targets  41  fixed to the mounting member  44 . For example, when there are three targets, three partition plates are preferably arranged at equal intervals separated by angles of 120 degrees so as to surround the targets. The rest of the configuration is the same as that of the third embodiment, so substantially identical elements are assigned the same notations and explanations are omitted. In  FIG. 10B , cross-sections of two adjoining cathode sets  43  and the side faces of two adjoining partition plates  46  are shown. According to this modification, the targets etc. are arranged off axis and the reactive gas is introduced from the center part of the cathode unit  14 , so the partition plates  46  can prevent sputter particles from other targets from entry. This effect is similar to the effect of the third embodiment explained above. The partition plates  46  may be directly fixed to the surface of the mounting member  44  or may be fixed in a floating state. 
         [0097]    In the modification shown in  FIGS. 11A and 11B , the three targets  47  fixed to the mounting member  44  are not disk shaped, but ring shaped. The mounting member  44  is not provided with a reactive gas introduction mechanism (hole and gas dispersion member) at its center like in the above embodiments. The three cathode sets  43  have ring shapes overall, have gas dispersion members  25  at their center parts, and are provided with reactive gas introduction mechanisms.  FIG. 11B  is a cross-sectional view along the line D-D in  FIG. 11A . In this modification, the three ring shaped cathode sets  43  arranged off axis at the cathode unit  14  are provided with reactive gas introduction mechanisms at the centers of the cathode sets  43 . Due to this, it is possible to introduce reactive gas from the center parts of the three targets  47  and achieve substantially the same effects as in the above embodiments. 
         [0098]    In the modification of  FIGS. 12A and 12B , provision is made the configuration shown in  FIGS. 11A and 11B  wherein circular partition plates  49  are provided around the targets  47  at the three cathode sets  43 .  FIG. 12B  is a cross-section along the line E-E in  FIG. 12A . The rest of the configuration is the same as that of the embodiment of  FIGS. 11A and 11B , so the same elements in  FIGS. 12A and 12B  are assigned the same notations and explanations are omitted. In this modification, the three ring shaped cathode sets  43  arranged off axis at the cathode unit  14  are provided with reactive gas introduction mechanisms at the centers of the cathode sets  43  and are provided with partition plates  49  around the targets  47 . Due to this, it is possible to introduce reactive gas from the center parts of the three targets  47  and obtain similar effects to those of the above embodiments. Further, it is possible to prevent entry of sputter particles from adjoining targets. The partition plates  49  may be directly fixed to the surface of the mounting member  44  or may be fixed in a floating state. 
         [0099]      FIG. 13  shows a fourth embodiment of the sputtering system according to the present invention. This sputtering system is a horizontal type sputtering system. A single ring-shaped target  22  is arranged at the floor  11   c  of the vacuum chamber  11 . Reference numeral  51  is for example a disk shaped substrate. Illustration of the support mechanism of the substrate  51  is omitted. Further, illustration of the cathode and its related parts and the vacuum evacuation system is omitted. In  FIG. 13 , elements substantially the same as elements explained in the above embodiments are assigned the same notations. In this sputtering system as well, a reactive gas introduction mechanism is provided at the center part of the target  22 . The reactive gas introduced at this reactive gas introduction mechanism, as shown by the arrows  52 , flows uniformly along the surface of the target  22  from the center part to the outer circumference and is made uniform in concentration. The reactive gas etc. are exhausted from an exhaust port  53  provided around the target  22  as shown by the arrows  54 . The sputtering system according to the fourth embodiment can also give similar effects as the above embodiments. 
         [0100]      FIG. 14  shows a fifth embodiment of the sputtering system according to the present invention. The fifth embodiment is a modification of the fourth embodiment. In the fifth embodiment, elements substantially the same as elements explained in the fourth embodiment are assigned the same notations. In this embodiment, the side wall of the vacuum chamber is provided with another gas introduction part  61  and gas exhaust port  63  as shown by the arrow  62 . Further, in addition to the reactive gas introduction mechanism at the center of the target  22 , a reactive gas introduction mechanism  64  is provided at the entire circumference around the target  22  at the floor  11   c  of the vacuum chamber  11  or at several locations thereof. Reference numerals  65  show other flows of reactive gas introduced by the reactive gas introduction mechanisms  64  into the vacuum chamber and heading from the outer circumference to the center. In this case, for the reactive gas feed system, preferably common use is made of the system  23  shown in  FIG. 3 . Note that the exhaust port  53  provided around the target  22  explained earlier is not provided and that the gas is exhausted through the gas exhaust port  63  connected to a not shown evacuation mechanism. The rest of the configuration is the same as those of the fourth embodiment. 
         [0101]    According to the fifth embodiment, a flow of reactive gas from the center part of the target  22  or the center part of the cathode and a flow of reactive gas from their outer circumferences are formed, so it is possible to make the concentration of reactive gas on the surface of the target uniform more effectively. Note that in the fifth embodiment, argon or another sputter gas is introduced from another gas introduction part  61  and reactive gas is introduced from the center of the target or cathode and their outer circumferences, so like in the other embodiments if introducing a gas containing the reactive gas (reactive gas or mixed gas) from at least the center of the target or cathode, it is also possible to introduce the sputter gas and auxiliary reactive gas (reactive gas other than introduced from the center) from either of the introduction parts. 
         [0102]    Note that in the case of the fifth embodiment, the cathode is preferably made to rotate by the structure disclosed in Japanese Patent Publication (A) No. 2002-088471 by the same assignee. 
         [0103]    In both the above fourth and fifth embodiments, in the same way as the above embodiment, it is possible to provide the covering member  17  as shown in  FIG. 3 , make the targets an off axis structure as shown in  FIG. 9  etc., or provide a vane member  31  as shown in  FIG. 7 . Further, conversely, it is possible to add the characterizing configurations shown in  FIG. 13A ,  FIG. 14A , etc. to the vertical type sputtering system of the first embodiment etc. 
         [0104]    An example of the structure relating to the method of flow of the reactive gas in the above reactive gas introduction mechanism will be explained next with reference to  FIGS. 15A and 15B . In the above embodiments, in principle, as shown in  FIGS. 15A and 15B , provision is made of a gas dispersion member  25  passing through a hole  14   a  formed in each cathode unit  14 . In this structure, the gap formed between the gas dispersion member  25  and the inner surface of the hole is utilized for introduction of the reactive gas  71 . As opposed to this, as shown in  FIG. 15B , the shaft part  25   a  of the gas dispersion member  25  may be formed in a pipe shape (serving as a gas pipe) and a plurality of gas outlets  72  may be formed at the base of the enlarged diameter part  25   a  so as to blow out the reactive gas. 
         [0105]    In the explanation of the above embodiments, the shapes, sizes, and positional relations were shown generally to an extent enabling understanding of the present invention. The present invention is not limited to the illustrated embodiments. It may be either a two-sided sputtering system or one-sided sputtering system in each case. Further, in the two-sided sputtering system configuration of the embodiments, two cathode units were arranged at the two sides of a substrate, but the number of cathode units can be changed in accordance with the number of substrates and the process. Further, a structure causing the cathode units to rotate is also possible. In this case, the axial centers of the cathode units are utilized for provision of water pipes or electrical cables. 
         [0106]    The present disclosure relates to subject matter contained in Japanese Patent Application No. 2003-147529, filed on May 26, 2003, the disclosure of which is expressly incorporated herein by reference in its entirety. 
         [0107]    Although only preferred embodiments are specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.