Abstract:
The present invention provides a magnetron sputtering system using a gas distribution system which also serves as a source of anodic charge to generate plasma field. The sputtering system is comprised of a vacuum chamber, a cathode target of sputterable material, a power source which supplies positive and negative charge, and a gas distribution system. The gas distribution system may comprise a simple perforated gas delivery member, or it may comprise a perforated gas delivery member with an attached conductive anodic surface. The gas delivery member may also contain an inner conduit with further perforations which serves to baffle flow of the sputtering gas. Gas flow may be regulated within discrete portions of the gas distribution system. The anodic surfaces of the gas distribution system are cleaned through the action of plasma and gas flow, creating a more stable plasma and reducing the need for maintenance.

Description:
FIELD OF THE INVENTION 
   The present invention relates to apparatus, systems, and methods utilized for the controlled deposition of thin films of sputtering material on substrates. More specifically, the present invention provides for magnetron sputtering systems that comprise a gas distribution system including one or more conductive anodic surfaces. 
   BACKGROUND OF THE INVENTION 
   In the coated glass industry it is desirable to apply one or more thin layers of coating materials to one or both surfaces of the glass to provide desired characteristics to the finished coated glass product. For example, in the manufacturing of glass for a variety of applications, it is often desirable to apply infrared reflective coatings and/or other multilayer coating systems to provide desirable characteristics related to transmittance, emissivity, reflectivity, durability, color, photocatalysis and chemical resistance. 
   Presently, the controlled sputter deposition of coating materials is the most effective method of forming thin films on solid substrates. Compared with other thin-film formation methods such as vacuum evaporation, electroplating, electroless plating, and chemical vapor deposition, sputter deposition allows for a greater choice of film materials, higher purity and controlled composition of the film, greater adhesive strength and homogeneity of the film, and greater control of the film thickness. 
   Planar and cylindrical magnetrons are widely used for sputtering deposition of films on substrates. The substrate is positioned within a vacuum chamber containing at least one rotating cylindrical target or planar target that is comprised of or includes sputtering material on its outer surface. Sputtering occurs when energetic ionized particles impinge on the surface of a the target, causing the emission of particles, and typically erosion of the surface. Generally, the sputter coating process can continue until the cathode target is exhausted. 
   To achieve the sputtering process an electrical field is created between a cathode target and an anode in a vacuum chamber. Next, a gas, typically an inert gas such as argon, is introduced to the vacuum chamber. Electrons in the electrical field are accelerated and gain enough energy to ionize the gas atoms and create a glow discharge plasma. The resulting plasma is then attracted to the target, bombarding it and liberating target surface atoms. The charged plasma is maintained in a relatively narrowly defined area in front of the target by a magnetic field. As previously suggested, the target functions as the cathode in the sputtering system and a separate anode is provided in the chamber at a location spaced away from the target. Commonly, the chamber walls, a separate bar or another conductive member positioned away from the target functions as the anode. 
   To keep the plasma discharge active and local to the cathode target, it is necessary for the chamber to have a stable field enveloping the plasma and the cathode target. Typically, this is performed with permanent magnets, located behind or within the target, which confine electrons generated by a negative voltage close to the target surface thus keeping the plasma localized to the target surface. The magnets are usually of a permanent magnet type, arranged uniformly behind a planar target or arranged along a line within the rotating cylindrical target and held from rotation with the cylindrical target. The sputtering zone is created by the magnets extending along substantially the entire length and width of the planar sputtering target or extending along the length of the cylindrical sputtering target and only a small circumferential (radial) difference around it. Traditionally, the magnets are arranged so that the sputtering zone exists at the bottom of the planar or cylindrical target, facing a substrate being coated directly beneath. 
   Sputtering may be conducted in the presence of one or more gases. A first inert gas, such as argon, is commonly utilized for the production of the glow discharge plasma in a sputtering system. Additional gases may be supplied to the sputtering system if desired, such as one or more reactive gases. When conducted in the presence of a reactive gas such as oxygen or nitrogen, a reactive product of the coating material is deposited on the substrate, i.e., the coating layer is the product of the coating material and the reactive gas. For example, the introduction of a reactive gas such as oxygen or nitrogen to the chamber forms an oxide or nitride with the liberated target atoms. 
   A problem with many previous sputtering systems is that during the sputter coating process, liberated particles of coating material are deposited on non-substrate exposed surfaces within the vacuum chamber, such as the chamber walls and other mechanisms within the chamber including the one or more anodes. Over time, a layer of the target material or rejected target material will tend to accrete on the outer surface of the anode. The rate at which this accumulation occurs will vary depending on the power applied and the material of which the target is formed. While this accumulation is not desirable in the sputtering process for any targets, a coating of a conductive material generally does not unduly hamper performance of the sputtering system. However, if the material deposited on the anode is an insulator or dielectric material, this creates significant problems. For example, when a dielectric material such as zinc is sputtered in an oxidizing atmosphere to deposit zinc oxide, a coating of zinc oxide will be deposited on the anode, which reduces the effectiveness of the sputtering process. Since many coating materials or their reactive products are insulators, semiconductors, or are otherwise substantially electrically nonconductive materials (such as Al 2 O 3 , SiO 2 , Si 3 N 4 , TiO 2 ), accumulation of these nonconductive materials on the anode causes a progressive slowing of the coating process, which ultimately results in the process shutting down. A nonconductive or dielectric material coating on the anode inhibits and eventually prevents charge carriers from flowing from the anode to the cathode, thus first reducing and eventually, in effect, stopping the sputtering process. 
   Similarly, undesirable coating of the gas distribution system positioned within the vacuum chamber may also cause problems related to adequate sputtering of coating material. For example, undesirable coating of the gas delivery members positioned in the vacuum chamber can cause insufficient reaction between the coating materials and the reactive gases, if a reactive gas is delivered through such members, or can inhibit the creation of plasma by limiting the amount of gas delivered to the chamber. Therefore, the result of coating build up on the gas distribution system may create overly metallic films or cause a slowing of the system due to insufficient plasma generation. 
   The sputtering zone also becomes difficult to control and maintain when the immediate area surrounding the cathode becomes coated with sputtering material. As this happens the charged plasma on the surface of the cathode is repulsed from the built up sputtering coating on the internal surfaces of the chamber due to their like polarity. As the repulsion of the plasma increases, the charged plasma expands outward away from the cathode in “search” of a conductive outlet. As the conductive areas of the chamber become randomly distributed and located further and further away from the plasma and the cathode, the uniformity of the plasma discharge deteriorates over time, thereby slowing the sputtering process. Eventually, the sputtering process needs to be stopped for cleaning. Furthermore, the non-uniformity of the plasma discharge typically reduces the quality of the thin film on the substrate. 
   Manufacturers will often try to stretch the chamber&#39;s productive operating period. This can be risky since near the end of a productive operating period the plasma discharge may be searching for non-coated areas in the chamber. To keep the plasma discharge active, manufacturers sometimes inject extra gas through the gas distribution system and into the chamber to create a non-insulated area. This extra gas can create a nucleation curtain or a clustering of the sputtered material. As a result, electrical current may be directed to flow through the nucleation curtain into the gas distribution system, seeking a path back to the power supply. This improper flow of electric current can cause the gas pipe to meltdown. 
   In addition to process downtime, the accumulation of electrically nonconductive or dielectric coatings on the anode of a sputter coating device may have other adverse effects on the coating process and the coating formed on the substrate. Nonuniformities may occur in the coating due to changes in the size of the conductive area of the anode. Moreover, the accumulation of electrically nonconductive material on the anode may contribute to arcing, thereby causing large pieces of coating material to drop off the cathode target or other coated positions within the chamber and onto the substrate. Furthermore, thick accumulation of a substantially nonconductive coating on the anode results in poor adhesion of the coating to the anode. As a result, flakes or pieces of material may fall off the anode and onto the substrate, thereby contaminating the coated surface. All of these adverse effects result in a nonuniform coating on the substrate to be coated. 
   These coating nonuniformities, as well as the accumulation of nonconductive material on the anode necessitate interrupting the coating process in order to clean or change the anode. This involves venting the chamber, careful cleaning, and reevacuating the chamber. Such nonuniformities and accumulation often occur at levels sufficient to require the user to frequently stop the process in order to reconditioning the anode. One conventional technique requires that production be shut down for as much as 6–8 minutes every hour so that the relative polarity of the cathode and anode can be reversed to sputter the accreted material off the anode surface. Other manual cleaning techniques, such as sandblasting the interior of the chamber may be utilized to reduce the accumulation of stray coating material. Cleaning the chamber can reduce production time and be very expensive. 
   Therefore, it would be beneficial to provide a sputtering apparatus comprised of a gas distribution system which contains one or more conducting anodic surfaces positioned in sufficient proximity to the cathodically charged target to maintain stable plasma distribution. Furthermore it would be desirable for a sputtering apparatus to provide the following features and/or benefits: a more constant and uniform depletion of the target; a more uniform coating process; a reduction in product variance by avoiding the problems associated with the accumulation of nonconductive material on anodic surfaces within the sputtering chamber; an improved sputtering system when the material being sputtered is a dielectric material; a number of spaced apart gas distribution nozzles as a series of separate anodes, thus permitting the size, shape, and position of the plasma to be easily controlled; a significant reduction in the slowing of the anode coating process over time; a significant reduction of the chamber becoming coated with insulating material; and, to reduce the need to stop the sputtering process for cleaning. 
   SUMMARY OF THE INVENTION 
   The present invention provides a magnetron sputtering system including a gas distribution system which contains one or more anodic surfaces positioned in sufficient proximity to the cathodically charged target to create a plasma. Generally, the sputtering system is comprised of a vacuum chamber defining a controlled environment; a cathode assembly including a target having one or more sputterable target materials; one or more power sources supplying a cathodic charge and an anodic charge; and a gas distribution system. In various embodiments of the present invention, the gas distribution system is comprised of one or more gas delivery members through which one or more gases are introduced into the deposition chamber. The gas delivery members may be operatively connected to a positive charge, or adjoined or in sufficient proximity to a positively charged anodic member. The distribution system is generally placed in sufficient proximity to and at a uniform distance from the cathode assembly to create a stable plasma. Preferably, the gas distribution system is maintained at a relatively positive state compared to the cathode assembly, providing the electrical potential necessary to maintain sputtering. The sputtering apparatus maintains a stable plasma at the exterior surface of the cathode assembly. The flow of sputtering gas through the gas delivery member maintains the anode in an exposed, electrically conductive state during prolonged sputtering of the target. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic drawing depicting a magnetron sputtering system including an anodic gas distribution system in accordance with an embodiment of the present invention; 
       FIG. 2  is a side cross-section pictorial representation of a sputtering apparatus including an anodic gas distribution system having one or more gas delivery members operably connected to conductive members; 
       FIG. 3  is an elevational view of a cathode/target and an anodic gas distribution system; 
       FIG. 4  is a perspective view of one embodiment of an anodic gas distribution system of the present invention; 
       FIG. 5  is a perspective view of an anodic gas distribution system including a conductive wire and an insulator; and 
       FIG. 6  is a pictorial representation of an anodic gas distribution system with a plurality of flow control devices for locally controlling gas discharge. 
   

   DETAILED DESCRIPTION 
   To assist in an understanding of the invention the preferred embodiments will now be described in detail. Reference will frequently be made to the drawings, which are summarized above. Reference numerals will be used to indicate certain parts and locations in the drawings. The same reference numerals will be used to indicate the same parts or locations throughout the drawings unless otherwise indicated. 
     FIG. 1  depicts a magnetron sputtering system  10 . Generally, the sputtering system is comprised of a vacuum chamber  12  defining a controlled environment; a cathode assembly  11  including a target  14  having one or more sputterable target materials; one or more power sources  16  supplying a cathodic charge and an anodic charge; and a gas distribution system  18 . 
   Sputtering techniques and equipment utilized in magnetron sputtering systems are quite well known in the present art. For example, magnetron sputtering chambers and related equipment are available commercially from a variety of sources (e.g., Leybold and BOC Coating Technology). Examples of useful magnetron sputtering techniques and equipment are also disclosed in United States patents, such as U.S. Pat. No. 4,166,018, issued to Chapin, the entire teachings of which are incorporated herein by reference. 
   The magnetron sputtering process usually occurs within a controlled atmosphere vacuum chamber  12 , which is depicted by phantom lines in  FIG. 1 . The vacuum chamber  12  generally includes metallic walls, typically made of steel or stainless steel, operably assembled to form a chamber that can accommodate a vacuum in which the sputtering process may occur. 
   As previously suggested, within or partially within chamber  12  is a cathode assembly  11 . The cathode assembly  11  generally comprises one or more cylindrical targets  14 , one or more motor assemblies  17 , optional shield assemblies  19  and optional magnet assemblies (not shown). Cylindrical targets  14  are usually held in a manner suitable to allow rotation about its longitudinal axes. Although a cylindrical target is illustrated in  FIG. 1 , note that one or more planar targets with adjacent magnet assemblies may also be utilized in the present invention. 
   Generally, the cylindrical target  14  includes a tubular backing formed of electrically conductive material, such as stainless steel, aluminum or any other suitably conductive material. The outer surface of the cylindrical target  14  is normally coated with one or more target materials, which are intended to be sputtered onto a workpiece or substrate. This coating of sputterable target materials is also referred to herein as “target materials.” Although only one cylindrical cathode assembly  11  is illustrated in  FIGS. 1 and 2 , use of two or more cylindrical cathode assemblies  11  within a single vacuum chamber  12  is contemplated. Sputterable target materials include, but are not limited to, materials such as silicon, zinc, tin, silver, gold, aluminum, copper, titanium, niobium or combinations thereof. The target materials may also be reacted with a reactive gas such as oxygen or nitrogen to form dielectric coatings, such as zinc oxide, silicon nitride or the like. 
   The cylindrical cathode assembly  11  further includes one or more motor assemblies  17  operably connected to each cylindrical target  14  by any clamping or bracketing means (not shown) known in the art. Such a clamping or bracketing device would not inhibit and would allow for the rotation of the cylindrical target  14  by the motor assembly  17 .  FIG. 1  depicts a cylindrical target  14  operably adjoined to multiple motors  38 . The clamping or bracketing device may be any type of clamp, bracket, frame, fastener or support that keeps the cylindrical target assembly  11  in a stationary position and does not affect the rotation of the cylindrical target  14 . 
   Each motor assembly  17  broadly includes one or more motors  38 , a power source  16 , and a control system  54 . Commonly, one or more power sources  16  provide power to the motors  38  as well as a positive charge to the gas distribution system  18  and a negative charge to the cylindrical target  14 . The power source may provide either direct current or alternating current. When alternating current is used, the 5–200 kilohertz range is preferred. Embodiments of the motor  38  of the present invention include but are not limited to programmable stepper motors, electric motors, hydraulic motors and/or pneumatic motors. The motor is operably adjoined to power source  16  and control system  54 . The motor  38  is operably connected to the cylindrical target  14  so that when activated it rotates the cylindrical target  14 . Of course, other types of motors and electronic control systems may be used without departing from the spirit or scope of the invention. 
   The motor  38  may be configured and/or programmed to optimize the efficient use of the cylindrical target  14  by rotating the target through the plasma generated in the magnetron sputtering system  10 . For example, the motor assembly  17  may be programmed to produce changes in rotational speed to optimize the sputtering process and the life of the cylindrical target  14 . 
     FIG. 2  further illustrates an embodiment of the present invention that includes a system of entry and exit for the substrate or workpiece, thereby allowing for constant operation of the vacuum chamber  12  for extensive periods of time. See the entry and exit doors  30  shown in  FIG. 2 . The substrate support system  40  is comprised of rollers  28 , conveyor belt  42 , and support bars  44 . Substrate  34  rests upon conveyor belt  42  and is brought into deposition chamber  12  through door  30  by the rotation of rollers  28 . The rollers  28  are maintained at a speed which allows for optimum application of the sputtering material. Support bars  44  function to add support between the rollers  28  and to prevent substrate  34  from sagging when between rollers  28 . The substrate support system  40  allows for a continual deposition application. Once the substrate  34  has been coated, it exits the chamber  12  through an exit door  30 . 
   Referring now to the embodiments depicted in  FIGS. 1–3 , the magnetron sputtering system  10  also includes a gas distribution system  18 . The gas distribution system  18  generally includes one or more gas delivery members  22  through which one or more sputtering gases are introduced into the deposition chamber  12 , a high current electric conductor line  24  operably connecting the power source  16  to the cathode assembly  11  and one or more other components of the gas distribution system  18 , and a gas conduit  26  through which the sputtering gas is delivered from gas supply  20  to the gas delivery members  22 . Examples of the gas delivery members include, but are not limited to, tubes, hollow shafts, ducts, hollow bars and hollow beams, all generally comprising a conductive material. In accordance with the present invention, electric conductor line  24  delivers a positive charge to the gas distribution system thereby creating an anodic surface that is positioned in sufficient proximity to the target  14 . The positioning of the anodic surface in sufficient proximity to the cathode assembly  11  assists in maintaining stable plasma by stabilizing the zone of sputtering gas adjacent to the exterior surface of the target  14  (sputtering zone). Furthermore, the gas delivery members  22  and/or the anodic surface should remain substantially parallel to the cylindrical targets  14 . For example, the anodic surface depicted in  FIG. 1  is the surface of the gas delivery members  22 , which are positioned substantially parallel to the cathode assembly  11 . The precise symmetry between the gas delivery members  22  and/or anodic surfaces with the cylindrical targets  14  assists in providing uniform consumption of the cylindrical targets  14  and uniform coating thickness on the substrate  34  during the sputtering process. 
   In the sputtering process, after the initial preconditioning of the chamber  12 , the gas supply  20  provides a supply of gas, usually inert gas, and preferably argon, through the gas conduit  26 . The gas conduit  26  operatively connects the gas supply  20  to the gas delivery members  22  through which sputtering gas is introduced into deposition chamber  12 . The delivery of sputtering gas is added to chamber  12  by passing through the gas delivery members  22  and out of a plurality of nozzles  46  positioned on the gas delivery members  22 , as depicted in  FIGS. 1–5 . In one example, gas may be introduced to the deposition chamber  12  until a pressure of approximately 1–15 Pa is achieved. In order to maintain the chamber pressure of approximately 1–15 Pa in this example additional gas must be added over time. As depicted in  FIG. 5 , an insulator  31  may be added to the gas conduit  26  to prevent a discharge or surge of electrical energy through the gas conduit to the gas supply  20 . 
   Furthermore, in one embodiment of the present invention, as depicted in  FIG. 1 , the electric conductor line  24  is operatively adjoined to the gas delivery members  22  to apply a positive charge directly to the gas delivery members  22 . In this embodiment, the gas delivery members  22  themselves are conducting anodic surfaces. The gas delivery members  22  of this embodiment include nozzles  46  that are directed away from the target  14 , thereby providing a more uniform distribution of sputtering gas. The positioning of the nozzles  46  directed away from the target also localizes the plasma proximate to the surface of target  14  without unduly displacing the plasma by a flow of gas. This in turn helps ensure a relatively uniform film deposited on substrate  34 . 
   An alternative embodiment of the present invention, as depicted in  FIGS. 2 and 3 , illustrates gas delivery members  22  operably adjoined to a conductive member  27  by brackets  29 . The conductive member  27  may be comprised of stainless steel, aluminum or any other suitably conductive material. In this embodiment, the gas delivery members  22  are positioned so as to direct the gas distribution nozzles  46  at the conductive member  27 . Such positioning generally directs gas at the conductive member  27  thereby facilitating the production of a plasma flame or gas flow, which contacts the conductive member  27 . The plasma flame or gas flow provides a cleaning function, which maintains a conductive surface on the conductive member  27  and thereby prevents or diminishes the deposition of nonconductive target material on the conductive member  27 . The maintaining of such conductive surfaces assists in the maintenance of a stable plasma. The brackets  29  adjoining the gas delivery members  22  to the conductive members  27  may include conductive or nonconductive material depending upon whether it is desirable to deliver a positive charge to the gas delivery members  22 . In one embodiment, an anodic conducting surface is generated apart from the gas delivery member  22  and on the conductive members  27  by adjoining the conductive members  27  to the electric conductor line  24 . In this embodiment, the conductive members  27  are adjoined to the gas delivery members  22  by brackets  29  comprising a nonconductive material. The nonconductive material may include any type of ceramic or other suitable insulative material. 
   Referring to  FIGS. 1–3 , the electric conductor line  24  normally provides a positive electrical current to the periphery of the conductive members  27 , gas conduits  26  and/or the gas delivery members  22 . When the electric conductor line  24  is operably connected to the gas conduits  26  or gas delivery members  22 , the flow of sputtering gas is directed to flow over an exposed, electrically conductive surface of the gas delivery member  22  immediately adjacent to the apertures  46 . The flow of sputtering gas tends to clear the area surrounding the nozzle  46  from build-up of undesirable target material thereby maintaining a conductive anodic surface. Hence, as stated above, the gas delivery member  22  may be an anodic conducting surface, operably coupled to gas conduit  26  and electrically coupled to the electric conductor line  24  thereby delivering power from power supply  16 . 
   Alternatively, the electric conductor line  24  may electrically couple the power supply to the conductive member  27  which is separated from the gas delivery member  22  by conductive or nonconductive brackets  29 . Nonconductive brackets may be utilized if it is desired to isolate the gas delivery members  22  from an electric charge. As previously mentioned, in either embodiment the gas flow from the gas member  22  is generally directed toward the conductive member  27  thereby maintaining anodic conducting surfaces on the gas member  22  and/or the conductive member  27 . Finally, it is generally noted that in many embodiments of the present invention the power supply may provide a potential of approximately 0.1–5 kV with a current equal to at least 0.1–10 mA/cm 2  of the target surface area. However, this potential may vary depending upon the specifications of the magnetron sputtering system and other factors including, but not limited to sputtering material properties and sputtering rates. 
     FIG. 4  illustrates another embodiment of the gas distribution system  18  of the present invention wherein the gas distribution system  18  includes inner conduits  36  positioned within the gas delivery members  22 . In this embodiment, gas supply  20  is connected to the inner conduit  36 . Inner conduit  36  can be made of any suitable material used in distributing gas, such as steel, aluminum or stainless steel, and normally is dimensioned such that it can be placed inside a gas delivery member  22 . Inner conduit  36  includes a plurality of apertures  33  that are spaced and aligned apart from nozzles  46  of the gas delivery member  22 . For example, the apertures  33  may be positioned to face away from the nozzles  46  or staggered in between two or more nozzles  46  of the gas delivery member  22  as shown in  FIG. 4 . Either configuration, or variants of those configurations, prevents the direct flow of gas from the apertures  33  through the nozzles  46 . Thus, as gas is distributed from gas supply  20  through inner conduit  36 , the gas will flow through apertures  33  and into the gas delivery member  22 . As the gas enters gas delivery member  22 , it will diffuse, thereby evenly filling the gas delivery member  22 . The gas that is contained in the gas delivery member  22  will subsequently egress through the gas nozzles  46  and into the chamber  12 . By evenly filling the gas delivery member  22  and preventing the direct flow of gas along a jet, this embodiment more evenly distributes gas into chamber  12 , which provides a more stable plasma and enhances the sputtering process. 
   In another embodiment of the present invention, as depicted in  FIG. 5 , the conductive members  27  may include one or more conductive wires  52 , such as tungsten wires, that are suspended in front of the gas distribution nozzles  46 . In this embodiment of the present invention, the gas delivery members  22  and attached conductive wires  52  are operably adjoined to the electric conductor line  24 . The flow of sputtering gas through nozzles  46  of the gas delivery members  22  generally generates a plasma flame that passes over the conductive wire  52 . The flow of sputtering gas and/or the presence of a plasma flame assure that an exposed, conductive anodic surface is maintained on wire  52  during prolonged sputtering of the target. The maintenance of an exposed anodic surface is beneficial in sustaining a stable plasma and preventing the potential of plasma discharge through the gas delivery members  22  to the electrical connection  24 . It is important to note that an insulator  31  (depicted in  FIG. 5 ) is located between gas conduit  26  and gas supply  20 . The insulator  31  prevents current from flowing from a gas conduit  26  to the gas supply  20 , causing a meltdown at the joint where the two meet. 
   In an additional embodiment of the present invention shown in  FIG. 6 , the gas distribution system  18  comprises a plurality of independent gas lines  56  connected to the gas delivery member  22 . These independent gas lines  56  are each governed by a gas flow control device  58 , which is insulated to prevent current flowing back to the gas supply  20 , as described above. The gas flow control devices  58  independently control the rate of gas flow through each of the independent gas lines  56  in order to switchably control the plasma discharge by varying the gas flow at specific locations along the gas delivery member  22 . In one embodiment of the present invention the gas flow control device  58  comprises a valve that is adjusted by manually or by automated means thereby controlling the amount of gas that passes through each independent gas line  56 . In this embodiment, the gas flow can be adjusted to intermittently pulse in order to control the shape of the plasma and/or the consumption of various parts of the target. Finally, the gas delivery member  22  may include one or more partitions  37 , as depicted by the dashed lines in  FIG. 6 , to further control the flow of gas from each independent line  56  into the chamber  12 . 
   In operation, the magnetron sputtering system  10  can be used to deposit one or more coatings upon one or more substrates  34  by sputtering target material from the cylindrical cathode assembly  11 . The process is generally initiated by pumping down or evacuating deposition chamber  12 . Normally, the chamber  12  is pumped down to approximately 10 −5  Pa or less. This operation preconditions the chamber  12  by removing contaminants before the sputter deposition. Next, an inert gas, typically argon, is inserted into chamber  12  through the gas delivery system  18 , gradually increasing the pressure of the chamber to approximately 1–15 Pa (8–113 mTorr). Normally, in order to maintain a suitable gas pressure of a desired gas composition and to flush out contaminants in sputtering chamber  12 , a steady flow of clean argon gas is added over time. The gas may be added to chamber  12  by a plurality of gas distribution systems  18 , which are spaced at strategic locations within sputtering chamber  12 . This helps ensure a uniform gas composition and distribution across the surface of target  14 . This, in turn, helps ensure a relatively uniform film is deposited on substrate  34 , free from any visible variations in thickness or composition. 
   As previously suggested, vacuum chamber  12  of the present invention is adapted to maintain a controlled environment, e.g., temperature, pressure, and vacuum. That is to say chamber  12  is a plenum chamber; a compartment in which the interior air pressure is higher than the exterior air pressure. Gas is generally forced into chamber  12  and then slowly exhausted through an exhaust port  32 .  FIG. 3  depicts an embodiment of the present invention wherein the exhaust port  32  is present in the side wall of chamber  12 . A vacuum source  35  is connected to exhaust port  32  to evacuate chamber  12  and maintain the interior of chamber  12  at the appropriate vacuum level. Preferably, deposition chamber  12  includes external ducts (not shown) to circulate a coolant (e.g., liquid coolant) in order to maintain the internal temperature of the chamber and minimize outgassing of the walls during sputter deposition. 
   Once gas has been introduced to the chamber  12  the power source is initiated to administer a positive charge to the gas delivery system  18  and a negative charge to the cylindrical target  14 . As previously mentioned, the administration of charge to the cathode and anode generates a plasma, which facilitates the sputtering of target material from the target  14  to the substrate  34 . Generally, the substrate  34  is passed through the chamber  12  by the substrate support system  40  at a predetermined rate. The rate may be adjusted to provide the desired exposure to sputtered target material, thereby forming the preferred coating thickness. 
   During the sputtering process, gas passes through the gas delivery members  22  and through the nozzles  46 . The entry of gas through the nozzles and into the plasma usually generates a plasma flame due to the positioning of the plasma between the gas distribution system  18  and the cathode assembly  11 . As previously mentioned, the plasma flame or gas flow maintains clean anodic surfaces on portions of the gas distribution system  18 , such as the surface around the nozzles, the surface of the conductive member  27  and/or the surface of the conductive wire  52 . 
   It is important to note that the amount of material sputtered is inversely proportional to the gas pressure and distance between the anode and cathode. This is true for an increase in pressure because at high pressures (p≧7 Pa), the ions become compressed and thus frequently collide with neutral atoms; therefore, fewer ions arrive at target  14  with energy enough to liberate surface atoms on the target surface. Some of the atoms that are liberated will also collide with the large number of gas atoms and thus lose energy. Consequently, the sputtering yield and the deposition rates are reduced. The anode to cathode spacing is also a very important parameter because of the cathodes role as a source of electrons and sputtered atoms. Preferably, the substrate is placed as close to the target as possible to maximize the deposition rate. In practice, the general distance between target  14  and substrate  34  is about 1 to 10 cm, which provides for a high deposition rate. The distance can be modified depending upon the voltage maintained between the cathode and anode. 
   It will be appreciated that the present invention can take many forms and embodiments. The true essence and spirit of this invention are defined in the appended claims, and it is not intended that the embodiment of the invention presented herein should limit the scope thereof.