Abstract:
A method and apparatus for sputter deposition in which both a pulsed DC power supply and an RF power supply apply power to the target in the sputter deposition equipment. The pulsed DC power supply provides an on cycle where power is applied to the target, and an off cycle, in which a reverse polarity is applied to the target. The application of the reverse polarity has the effect of removing any charge that may have built up on the surface of the target. This reduces the likelihood of arcing occurring on the surface of the target, which can degrade the quality of the film being deposited on the substrate. By applying RF power simultaneously with the pulsed DC power to the target, the ionization efficiency on the target surface is increased. This results in a greater amount of material being removed from the target surface more quickly.

Description:
CLAIM OF PRIORITY  
       [0001]    This application claims priority from U.S. Provisional Patent Application No. 60/381,482 entitled “Pulsed Electrical Sputtering Deposition System and Apparatus” filed on behalf of Michael W. Stowell, Jr. on May 17, 2002. 
     
    
     
       BACKGROUND  
         [0002]    Thin film conductive and non-conductive coatings on a substrate have many uses in industry, including coatings on flat panel displays, semiconductors, touch screen displays, energy control coatings on glass, and optical interference filters, among other uses.  
           [0003]    These films are applied to surfaces in a variety of methods. One commonly used method is referred to as sputter deposition. Typically, in a sputter deposition process, the article to be coated, the substrate, is placed in a chamber. A plate of the material to be used in the coating, called the target, is also placed inside the chamber. The target is electrically connected to a voltage source, and serves as an electrical cathode/target. Typically, the sputtering chamber is evacuated, and a gas under pressure is pumped into the chamber. The gas selected for use in the chamber is dependent upon whether the sputtering process is to be a reactive or non-reactive process. If it is a reactive process, the gas is selected such that it reacts with the material of the target to form the desired material to be sputtered onto the substrate. For non-reactive sputtering, an inert, non-reactive gas is selected.  
           [0004]    The target is electrically energized. The electrical field between the anode of the electrical source and the cathode/target will ionize the gas in the chamber. The gas ions are then driven into the target by the electrical field. When this is done with sufficient energy, some of the material is dislodged from the target. The dislodged material typically becomes electrically neutral a short distance from the target, and travels through the chamber from the target to the surface of the substrate. If the process is a reactive sputtering process, the dislodged material reacts with the gas as it is traveling through the chamber and may also be reacted at the surface of the substrate. At the substrate, the target material or reacted target material forms a thin film coating on the surface of the substrate. This method produces a high quality film, but the speed of sputtering must sometimes be very slow to overcome certain problems associated with the sputter deposition process and still maintain a consistent film coating.  
           [0005]    There are several problems associated with sputter deposition processes, and in particular with reactive sputter deposition processes. For example, as the material is being sputtered, reactions can occur between the gas in the chamber and the target surface, forming a dielectric layer on the target that can act like a capacitor and cause electrical arcing. The arcing can cause uneven application of material to the substrate and defects in the coating. Varying the voltage applied or the speed at which sputtering is performed have helped reduce the problems and improve the quality of the film coating, but have not been completely successful in achieving all of these goals.  
           [0006]    Non-reactive sputter deposition processes are relatively fast. Arcing typically occurs more frequently in reactive sputter deposition processes because reactions between the target material and the gas in the chamber occur more frequently. For this and other reasons, reactive sputter deposition is generally performed more slowly than non-reactive sputtering.  
           [0007]    A variety of types of electrical sources have been used in an attempt to reduce or compensate for the electrical arcing that occurs. Electrical voltage sources used have included direct current (DC), alternating current (AC), and radio frequency (RF). While the different electrical sources have been found to reduce the incidence of arcing in certain configurations, there have continued to be problems with the systems. Additionally, with reactive sputtering, the speed at which deposition could be performed is still very slow, which increases the time necessary to produce an acceptable product, and therefore kept costs fairly high.  
           [0008]    Therefore, what is needed is a system and method for performing sputter deposition that reduces or eliminates electrical arcing from the target, that does not impact the quality of the film being deposited and minimizes the reduction in speed of coating, especially when reactive sputtering is used.  
         SUMMARY  
         [0009]    Non-conductive and conductive sputtered film property requirements have continually become more stringent with advances in technology. The existing magnetron sputtering processes are limited in some respects in their ability to effectively control film properties that meet these new requirements. Existing apparatus and processes can and do exhibit power limitations as well as the inability to finely control the sputtering process energies.  
           [0010]    The use of pulsed power supplies, both alternating current (AC) and direct current (DC), has benefited many film deposition processes and film properties, especially in transparent films, by better controlling the sputtering energies. This control is achieved due to the fact that these pulsed power supplies inherently extinguish and re-ignite the plasma at user-defined frequencies and intensities. At the beginning of each power pulse or plasma ignition from either of these systems, there is a broader distribution of electron energies producing ions and therefore, a greater percentage of the sputtered material is generated.  
           [0011]    With pulsed DC power there are many beginnings and plasma ignitions to increase the average electron energies to a much higher value, thus benefiting the process. By controlling the pulse duration, duty cycle, the electron/ion energies, and the number of pulses generated, specific sputtered material can be controlled. Using pulsed DC power can give the operator effective control over more of the sputtered thin film properties.  
           [0012]    Pulsed DC power supplies, during each “off” cycle, typically provide a reversed polarity to the target to remove charge build up on the surface of the target/cathode and thus reduce the chances of an arc. This method is very effective in reducing the total number of arcs the target/cathode may eventually incur. Further, depending on the frequency of the pulsed DC power supply, removing current from the target surface can act as an arc suppressant to limit the amount of energy which each arc that might occur would contain.  
           [0013]    While using pulsed DC power can be more effective than using other current sources and provide a more consistent sputtered film, it was felt that there might be other improvements that could be made to the system to further reduce problems with dielectric build up on the target surface and increase efficiency. In experiments, it was found that by applying radio frequency (RF) power simultaneously with pulsed DC power to the cathode/target, the ionization efficiency on the target surface was increased. This increase in ionization efficiency allowed more of the oxidized material to be removed from the surface faster than it would be removed without it. With less oxidized material, the arcing frequency was reduced and therefore the film properties enhanced. Another benefit of this ionization efficiency enhancement is that it resulted in a more even etching of the entire target surface, rather than just a track in the center area of the target, as commonly occurs.  
           [0014]    The use of pulsed DC power in conjunction with RF power can be an effective method to improve film quality by accurately controlling the maximum electron/ion energies at which a sputtered material is generated, enhancing the average electron/ion energy, and by the removing oxidized particles, thereby reducing the arcing of materials into the substrate.  
           [0015]    In summary this discovery allows the user to achieve higher yields and higher quality thin films than the prior art. The yield increases are a result of less arcing which means there is less particulate contamination, no “banding” of the substrate, and a reduced likelihood for damage to the target surface at higher deposition powers and/or speeds. The higher quality thin films are achieved from the ability to actively control the electron/ionization energies by adjustment of pulsing frequency and dwell times.  
           [0016]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:  
         [0018]    [0018]FIG. 1 is a conceptual diagram illustrating a portion of one arrangement of the sputtering apparatus of the present invention;  
         [0019]    [0019]FIG. 2 is a conceptual diagram illustrating a portion of another arrangement of the sputtering apparatus of the present invention;  
         [0020]    [0020]FIG. 2A is a conceptual diagram illustrating a portion of an alternative arrangement of the sputtering apparatus of the present invention as shown in FIG. 2;  
         [0021]    [0021]FIG. 3 is a representative circuit diagram showing the cathode DC bias shutdown circuitry;  
         [0022]    [0022]FIG. 4 is an oscilloscope tracing of the electrical activity over time when an arc is detected in a system of the present invention; and  
         [0023]    [0023]FIG. 5 is an oscilloscope tracing of the electrical activity over time when an arc is detected in a system of the present invention showing the pulsed DC voltage at the cathode and showing the pulsed DC power with RF interference filtered out. 
     
    
     DETAILED DESCRIPTION  
       [0024]    In the discussion of the FIGURES, the same reference numerals will be used throughout to refer to the same or similar components. In the interest of conciseness, various other components known to the art, such as vacuum sputter deposition chambers, and the like necessary for performing sputter deposition coating, have not been shown or discussed.  
         [0025]    In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known elements have been illustrated in schematic or block diagram form in order not to obscure the present invention in unnecessary detail.  
         [0026]    Refer now to the drawings wherein depicted elements are, for the sake of clarity, not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.  
         [0027]    [0027]FIG. 1 depicts an arrangement of an arc suppression mechanism  10  of the present invention. A target mounting plate  20  can be used to hold the target, or cathode  30 ; or in some arrangements, a mounting plate  20  does not need to be used. The target/cathode  30 , or if a target mounting plate is used, the target mounting plate  20 , is electrically connected to two power sources, a pulsed DC power system  100  and an RF power system  200 . The pulsed DC power supply  120  of the pulsed DC power system  100  is connected to a feed  40  located near the bottom of the cathode/target  30  or target mounting plate  20 , by means of a high current RF Filter  110 . The RF power supply  220  of the RF power system  200  is connected to a feed  50 , typically located near the center of the cathode/target  30  or target mounting plate  20 , by means of a tuner  210 . In certain configurations of the present invention, the RF power supply  220  and the tuner  210  have been modified to incorporate equipment that can sense arcing occurring on the target and quickly shut down the RF power supply  220 .  
         [0028]    The arc suppression mechanism  10  of the present invention is intended for use inside a vacuum deposition chamber (not shown). While certain portions of the mechanism  10  can be located outside the vacuum chamber (not shown), such as the RF power supply  220 , the pulsed DC power supply  120 , the tuner  210 , the filter box  110 , and the target mounting plate  20 , if used, the cathode/target  30  is typically located inside the vacuum deposition chamber (not shown). However, the specific arrangement and location of equipment varies from installation to installation. Permanent non-moving magnets, movable magnets, or rotary magnets (not shown) can be used to create confining magnetic fields of the cathodes in the vacuum chamber. The gas(es) used in the vacuum chamber (not shown) are dependent on the desired characteristics of the sputtered coating, as in the prior art.  
         [0029]    The RF power supply  220  is connected to the cathode/target  30  through an RF tuner  210 , the tuner  210  being mounted directly to the back of the cathode/target  30  or mounting plate  20 . A commercially available RF power supply  220  and tuner  210 , such as the model RFG3001 3KW RF Power Supply and the AZX90 Tuner, by Advanced Energy can be used in the present invention. The RF power supply  220  typically provides power to the cathode/target  30  at a frequency between about 1 MHz and 94 MHz.  
         [0030]    It is sometimes necessary to modify the commercially available RF tuners  210  to include DC bias arc detection circuitry as well as RF arc detection circuitry, integrated with shutdown circuitry to electrically disconnect the RF power supply  220  from the cathode/target  30  when an arc is detected. By adding DC bias detection circuitry, such as that shown in FIG. 3 to the RF tuner along with standard RF detection circuitry, time delays in sensing arcing and responding by shutting down the RF power supply  220  are reduced, resulting in more responsive system reactions to an arc. The RF power supply  220  may also be modified to allow for fast shutdown and ramp up of the power supply, if necessary.  
         [0031]    Standard RF arc detection circuitry has been used with the tuner  210  to calculate the dv/dt of the cathode/target  30  voltage. The calculated dv/dt is compared to a threshold voltage. When the value of dv/dt is greater than the threshold voltage, the output of the RF power supply  220  will be inhibited by the tuner  210 . The response time from when the dv/dt measurement is determined to exceed the threshold value until the RF power supply  220  output is reduced and then returned to normal levels is approximately 150-200 microseconds, owing in part to the inherent delays in RF power supply  220  operation.  
         [0032]    A continuous sampling of the voltage at the central cathode/target connection  50  for the RF power supply  220  is taken by means of a resistor network and compared to a threshold voltage value, which can be set to a value in the range of approximately 20 to 350 volts, and more preferably 70 to 120 volts, depending on the specific system and desired characteristics of the sputtered film, but the range can be from 20 to 350 volts. When the pulsed DC voltage to the cathode/target  30  is shut off in response to an arc, the voltage measured at the cathode/target  30  will drop, which serves as a signal to the RF power system  200  that an arc has occurred on the target  30 , and the pulsed DC power supply  120  has been shut off in response to that arc. When the voltage measured at the cathode/target  30  is less than the threshold voltage value, the RF power supply  220  output will be shut down by clamping the set point/regulation circuit or performing an external shutdown of the RF power supply  220 , depending on the specific arrangement of the present invention used. The response time from when the voltage measurement is determined to fall below the threshold value until the RF power supply  220  is shut down will vary depending on the system configuration, with an average being approximately 40 microseconds.  
         [0033]    The pulsed DC power supply  120  is connected to the cathode/target  30  through a high current RF filter  110 , the filter  110  being mounted directly to the back of the cathode/target  30  or mounting plate  20 . The high current RF filter  110 , which can be a standard Pi, Tee or LC filter, depending on the configuration of the arc suppression mechanism  10 , isolates and separates the power provided by the pulsed DC power supply  120  from that provided by the RF power supply  220 . A commercially available power supply, such as the Pinnacle Plus pulsed DC power supply, by Advanced Energy can be used in the present invention. It is preferred that the pulsed DC power supply  120  utilized incorporate an internal arc suppression mechanism.  
         [0034]    The pulsed DC power system  100  typically monitors the cathode/target  30 , and when an arc is detected, the pulsed DC power supply  120  is shut down for a period of time. The internal arc suppression mechanism of the pulsed DC power supply  120  is typically adjustable so that the detection time and shutdown time can be adjusted, with the adjustment method dependant upon the manufacturer of the pulsed DC power supply  120 . The response time from when the voltage measurement at the cathode/target  30  is determined to fall below the threshold value until the pulsed DC power supply  120  is shut down is typically only a few microseconds. When the voltage at the cathode/target  30  drops because the pulsed DC power supply  120  has been shut down, the detection circuitry of the RF tuner  210  that is attached to the cathode/target  30  will detect the voltage drop, and act to shut down the RF power supply  220  as well, as described above.  
         [0035]    Once the specified shut down time of the pulsed DC power supply  120  has been met, the pulsed DC power supply  120  will be turned on again.  
         [0036]    In one arrangement of the present invention, the system can be configured such that if the pulsed DC power supply  120  is turned on again and another arc event is occurring simultaneously, the pulsed DC power supply  120  will shut down again, and the specified shutdown time for the pulsed DC power supply  120  will increase to some multiple of the shutdown time set in the pulsed DC power supply  120 . After the pulsed DC power supply  120  has been shutdown for a time equal to the multiple of the shutdown time, it will come back on again. If it is turned back on a second time and yet another arc event is occurring simultaneously, the pulsed DC power supply  120  will shut down again, and the specified shutdown time for the pulsed DC power supply  120  will increase to some greater multiple of the shutdown time set in the pulsed DC power supply  120 , set on the pulsed DC power supply. After the pulsed DC power supply  120  has been shutdown for a time equal to the greater multiple of the shutdown time, it will come back on again. This cycle of increasingly greater shutdown times will continue as long as the pulsed DC power supply  120  comes back on into a simultaneous arc event. After the pulsed DC power supply  120  successfully comes back on when there is no simultaneous arc event, the shutdown time will be reset to the time set in the pulsed DC power supply  120 . This method is sometimes referred to as a “progressive arc shutdown.” 
         [0037]    When the DC voltage to the cathode/target  30  rises above the threshold specified in the RF tuner  210  sensor circuit, the RF power supply  220  will be turned back on, as well. Because there is an inherent delay in the RF power supply  220  being reactivated, the total time for the RF power supply  220  to come back on line is approximately 100-150 microseconds, although this time can be improved with circuit modifications. The total average time from the start of an arc on the cathode/target  30  until both the pulsed DC and RF power supplies,  120 ,  220  are shut off and back on again is less than 2500 microseconds, and preferably approximately 400 microseconds.  
         [0038]    In addition to the severity of the arcing being reduced, due to increased responsiveness of the power systems  100 ,  200  when an arc is detected, because less oxidized material is produced with less severe arcs, the buildup on the surface of the target  30  occurs more slowly, and the number of incidents of arcing is reduced as well. Typically, in operation, once the system had warmed up, approximately 1-2 arcs/minute occurred, compared to hundreds or thousands of arcs/minute that can often be seen in typical systems, with the severity of the arcs typically being reduced as well.  
         [0039]    The pulsed DC power supply  120  provides power to the target/cathode  30  according to an adjustable duty cycle between 0.1% to 99.9%, used at frequencies from about 0.1 MHz to about 20 MHz. Typically, the higher the frequency, the greater the duty cycle. For example, at 0.4 MHz, the duty cycle is typically 12-15%; at 1 MHz, the duty cycle is 25-40% and at 3 MHz the duty cycle is 50-70%. Duty cycle refers to the percentage of time that the pulsed DC power supply  120  is on. Therefore, a duty cycle of 15% refers to the situation where the pulsed DC power supply  120  is delivering power to the target 15% of each cycle. Thus, a frequency of 100 KHz with a duty cycle of 25% refers to a situation when the pulsed DC power supply  120 , operating at a 100 KHz frequency is turned on for 2.5×10 −6  seconds and then is turned off for 7.5×10 −6  seconds and then the process is repeated. The preferred output from the pulsed DC power supply  120  during the power on phase is a constant power delivered at a constant voltage.  
         [0040]    In the arrangement of the system  10  of the present invention depicted in FIG. 1, because RF and DC arc detection circuitry was incorporated into the RF Tuner  210 , no physical connection between the pulsed DC power system  100  and the RF power system  200  was necessary to achieve the desired arc detection and protection.  
         [0041]    [0041]FIG. 2 depicts another arrangement of an arc suppression mechanism  12  of the present invention. In this arrangement, the pulsed DC power system  150  is connected to the RF power system  250  by means of a feedback control mechanism  180  that turns off the RF power supply  220  when the pulsed DC power supply  120  is shut down. In this arrangement, a target mounting plate  20  can be used to hold the target, or cathode  30 , but is not needed in all configurations. The target/cathode  30 , or if a target mounting plate is used, the target mounting plate  20 , is electrically connected to the pulsed DC power system  150  and the RF power system  250 . The pulsed DC power supply  120  of the pulsed DC power system  150  is connected to a feed  40  located near the bottom of the cathode/target  30  or target mounting plate  20 , by means of an RF Filter  160 . Without the RF filter  160  installed, it was found the RF power fed back into the pulsed DC power supply  120 , which could damage the voltage sensing circuitry in the pulsed DC power supply  120 . The RF power supply  220  is connected to the input of the matching network  260  and the RF power output is connected to a feed  50  located near the center of the cathode/target  30  or target mounting plate  20 .  
         [0042]    An alternative arrangement of this system configuration is shown in FIG. 2A. In this arrangement, the RF power output from the matching network  260  is connected to the RF filter  160 , and the RF power is processed into the feed  40  located near the bottom of the cathode/target  30  or the target mounting plate  20 .  
         [0043]    The matching network  260  blocks DC feedback from the RF power supply  220 , to prevent the RF power supply  220  from being damaged by the DC feedback. In the arrangement of the present invention shown in FIGS. 2 and 2A, feedback between the pulsed DC power supply  120  and the RF control mechanism  270  for arc suppression is provided by means of the feedback control mechanism  180 . When an arc occurs, the pulsed DC power system  150  senses the rapid drop in the cathode/target  30  voltage and shuts down the output of the pulsed DC power supply  120 . This shut down in turn causes a signal to be sent from the pulsed DC power supply  120  to the RF power supply  220  via the feedback control mechanism  180  that shuts down the RF power supply  220  until the arc has stopped. The feedback control mechanism  180  feeds a high, or off signal to the RF control mechanism  270 , which sends a signal to the RF power supply  220  by means of the RF inverter in the match network  260  to shut off the RF output. When the arc event has cleared and the pulsed DC power supply  120  is turned back on, the feedback control mechanism  180  sends a low/on signal to the RF control mechanism  270 , which sends a signal to the match network  260  that will tell the RF power supply  220  to turn back on. The response time to shutdown the RF power supply  220  is very rapid in this arrangement of the present invention, typically less than 250 microseconds.  
         [0044]    During testing of the various arrangements of the mechanism of the present invention, it was found that multiple arc suppression mechanisms  10 ,  12  operating independently of each other could be placed in close proximity, and there was no apparent effect on the ability of the units to suppress arcing, nor affect on the speed of the mechanisms caused by the proximity of other mechanisms.  
         [0045]    The application of RF power with pulsed DC power also allows the operator to adjust the approximate maximum electron/ion energy level cap on the surface of the target if the sputtered film produced does not meet the desired specifications.  
         [0046]    Generally, in prior art inventions, the gas pressure inside the vacuum chamber is maintained at about 2×10−3 Torr (0.3 pascal) when sputtering is being performed. Prior art processes also required that the magnetic field be a minimum 600 oersted (Oe) on the surface of the target. One unexpected benefit of using RF power in addition to the DC power in the present system is that the magnetic field, operating pressure and operating temperatures could be varied from those required in the prior art. The operating pressure in the vacuum chamber when sputtering is being performed in the present invention can typically maintained at about 1×10−3 to about 10×10−3 Torr, depending on the particular application, with a preferred range of about 1.5×10−3 to about 5.5×10−3 Torr. Operation of the system of the present invention has been shown to be effective at field strengths less than (and also greater than) 600 oersted, with the cathode/target being almost completely arc free.  
         [0047]    [0047]FIG. 3 depicts a Cathode DC Bias Shutdown Circuit modification for the RF Tuner  210 . The cathode DC bias shutdown circuit  300  continuously samples the voltage at the cathode feed  50 . The voltage signal  302  enters the circuit through resistor R1 310. The voltage signal  302  is fed through resistor R2 312, which divides the voltage by a factor of 100 to yield a signal level of 10 volts for every 1000 volts read at the cathode  50 . The RF voltage signal  302  is filtered out from the pulsed DC waveform by processing the signal through a filter  320 , comprised of an inductor  322 , and two capacitors,  324 ,  326 . The filtered voltage signal  303  is fed into the positive side of a comparator  330 , which compares the voltage signal  303  to a threshold voltage that is fed into the negative side of the comparator  330 . The threshold voltage fed into the negative side of the comparator  330  is obtained by means of a threshold circuit  330 , that provides an inverted input from resistors R3, 334; R5, 336; and R6, 338 that is 1 volt for every 100 volts on the cathode. When the filtered voltage signal  303  drops below the threshold voltage, the output of the comparator  330  is a high signal  304 , approximately 15 volts in this case. This high signal  304  is clamped and limited by resistor R4, 340 and the 15 VDC Zener Diode,  342 . The limited high signal  304  is fed into a MOSFET  350 , turning the MOSFET  30  on, which clamps the RF shutdown signal  360 , which drops the RF output voltage to zero. Depending on the arrangement and configuration of the arc suppression mechanism  10  used, the shutdown circuit  300  can be either internal or external to the RF power supply  220 .  
         [0048]    One arrangement of the present invention that was developed during testing is described here as an example of a specific system configuration, although many other configurations can be used. The system incorporates two arc suppression mechanisms  10  inside the vacuum chamber (not shown). The cathode/target  30  on each arc suppression mechanism  10  was 78 inches (1980 mm) in length. The adjacent cathode/targets  30  were positioned on a 14 inch center line, such that there was a 4 inch gap between the cathode bodies. The system was operated with a separate RF power supply  220  and pulsed DC power supply  120  connected to each cathode/target  30 , with a discrete tuner  210  and high current RF filter  110  connected to each cathode/target  30 . The frequency of the RF power supply  220  was approximately 13.56 MHz. Although the cathode/targets  30  can have discrete anodes, the configuration in this system had no discrete anodes, relying on grounded surfaces in close proximity to serve as anodes. The cathode/targets  30  each incorporated side dark space shields (not shown) that extended only to the target plane; they did not extend beyond the target plane to form a containment box or anode.  
         [0049]    Permanent non-moving magnets (not shown) were used to create confining magnetic fields in this arrangement of the invention. The horizontal fields of the magnets were in a range from 400 to 1200 Gauss. The target material was a 90/10 ratio of In 2 O 3 :SnO. A mix of oxygen, hydrogen and nitrogen was the gas used in the vacuum chamber in this arrangement of the present invention. The target to substrate distance was approximately 3.5″ to 4″ (89-102 mm). The operating pressure in the vacuum chamber when sputtering was being performed was maintained at about 3.5×10−3 Torr to 4.5×10−3 Torr.  
         [0050]    Tests were performed using a system as above. Based on calculations and measurements of the produced coating, the arc detection threshold in the system  10  was set to approximately 75 VDC. The test results at various power levels were as follows:  
                                                                                                                                                                           RF       Pulsed VDC                                    At 1 KW in the pulsed DC power supply:                0   KW   241               0.5   KW   124           &gt;0.5   KW   &lt;75   (not recorded)            At 2 KW in the pulsed DC power supply:                0   KW   252               1.5   KW   105           &gt;1.5   KW   &lt;75   (not recorded)            At 3 KW in the pulsed DC power supply:                0   KW   259               3.0   KW   104           &gt;3.0   KW   &lt;75   (not recorded)            At 4 KW in the pulsed DC power supply:                0   KW   265               3.0   KW   119           &gt;3.0   KW   &lt;75   (not recorded)                      
 
         [0051]    [0051]FIG. 4 is an oscilloscope tracing of the electrical activity over time when an arc is detected in a system of the present invention. Channel  1  shows the activity of the filtered DC cathode voltage being monitored, and channel  3  shows the RF On/Off signal. When the arc suppression mechanism of the pulsed DC power supply detects an arc event,  410 , the pulsed DC power supply is shut down for a period of time. When the voltage at the cathode/target drops because the pulsed DC power supply has been shut down, the detection circuitry of the RF power system that is attached to the cathode/target will detect the voltage drop, and act to shut down the RF power supply as well,  420 . As can be seen in the tracing, the time from when voltage measurement is determined to fall below the threshold value until the RF power supply is shut down is only a few microseconds.  
         [0052]    Once the predefined shut down time of the pulsed DC power supply has been met, the pulsed DC power supply will be turned on again,  430 . When the DC voltage to the cathode/target rises above the threshold specified in the RF power system, the RF power supply will be turned back on, as well,  440 .  
         [0053]    [0053]FIG. 5 is an oscilloscope tracing of the electrical activity over time when an arc is detected in a system of the present invention. Channel  1  shows the activity of the filtered DC cathode voltage being monitored, and channel  2  shows the unfiltered DC cathode voltage, while channel  3  shows the RF On/Off signal. When the arc suppression mechanism of the pulsed DC power supply detects an arc,  510 , the pulsed DC power supply is shut down for a specified period of time. When the voltage at the cathode/target drops because the pulsed DC power supply has been shut down, the detection circuitry in the RF power system that is attached to the cathode/target will detect the voltage drop, and act to shut down the RF power supply as well,  520 . As can be seen in the tracing, the time from when voltage measurement is determined to fall below the threshold value until the RF power supply is shut down is only a few microseconds.  
         [0054]    Once the predefined shut down time of the pulsed DC power supply has been met, the pulsed DC power supply will be turned on again  530 . When the DC voltage to the cathode/target rises above the threshold specified in the RF power system, the RF power supply will be sent a signal to turn back on as well,  540 . Note that there is an inherent delay in the RF power supply being reactivated  550 , and the time for the RF power supply to come back on line.  
         [0055]    Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.