Abstract:
A sputter deposition chamber may be fitted with measures to prevent or reduce electrical noise that might otherwise interfere with a controller for the sputter deposition chamber. A grounded shield plate may be coupled to an insulating member by which a sputtering target is mounted in the chamber. A ground line, separate from a power supply line, may be coupled to the chamber&#39;s enclosure wall and to a varying power supply. One or more filters may be coupled in series between chamber components and a controller associated with the chamber.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority from U.S. Provisional Patent Application Serial No. 60/214,817, filed Jun. 29, 2000, which is hereby incorporated by reference herein in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to the sputter deposition of material layers. More particularly, the present invention relates to methods and apparatus for depositing films that apply AC (e.g., radio frequency (RF)) power to a chamber coil and/or to a substrate support, or that apply power to a sputtering target.  
         BACKGROUND OF THE INVENTION  
         [0003]    Manufacture of certain semiconductor devices requires a sputtering process in which a target is mounted in a sputtering chamber and bombarded with ions. The ion bombardment causes the target to emit molecules that are deposited on a substrate that is the subject of the sputtering process.  
           [0004]    [0004]FIG. 1 is a schematic side elevational view of a conventional chamber  11  adapted to sputter deposit a layer of material such as aluminum nitride. The chamber  11  comprises a chamber enclosure having an enclosing wall  13 , and an insulating region  15  coupled to the enclosing wall  13  and adapted to support a sputtering target  19 . The chamber  11  is adapted to couple the sputtering target  19  to a source of varying power (e.g., a pulsed direct current power source that is pulsed by being repeatedly turned on and off). Specifically, a power supply line  21  couples the target  19  to a varying power source  23  as shown in FIG. 1. Conventionally the power supply line  21  may comprise a coaxial cable, a center portion of which supplies power to the target  19 , and an outer shield portion of which provides a ground line between the target  19  and the varying power supply  23 . The insulating region  15  prevents the varying power applied to the target  19  from being transmitted to the enclosing wall  13 .  
           [0005]    A controller C is coupled to various chamber components via a plurality of controller wires  26 , and functions to control the chamber components coupled thereto.  
           [0006]    The present inventors have discovered that power supplied from the varying power source  23  to the sputtering target  19  tends to couple to other chamber components, thereby causing undesirable effects (i.e., electrical noise). Among the possible effects of such noise are causing an erroneous high-voltage reading which may cause the controller C to terminate processing (i.e., triggering an emergency shutoff of controller C). Other undesirable effects or noise may include erroneous data readings on the monitor of the controller C, fluctuation or instability of the pointer on the monitor of controller C, etc.  
           [0007]    Accordingly, the present inventors have recognized a need to address noise problems associated with a power source for a sputtering chamber.  
         SUMMARY OF THE INVENTION  
         [0008]    To reduce the noise experienced by conventional chambers that apply AC (e.g., RF) power to a chamber coil and/or to a substrate support, or that apply pulsed DC power to a sputtering target, the inventive chamber comprises one or more of the following features:  
           [0009]    a grounded shield plate coupled to a sputtering target (e.g., via an insulating member);  
           [0010]    a ground line, separate from a power supply line (i.e., other than the shield portion of the power supply line) coupled to both the chamber&#39;s enclosure wall and to a varying power supply; and/or  
           [0011]    one or more filters coupled in series between one or more chamber components and a controller C.  
           [0012]    In one aspect the ground line is as short as possible, and the varying power supply is installed close to the inventive chamber so as to reduce the length of the power supply line, thereby minimizing detrimental capacitance and inductance that may occur therealong. The mechanism for grounding the shield plate may comprise a metal block which couples to both the shield plate and the chamber&#39;s enclosure wall via a plurality of springs. The one or more filters may be designed to reject the specific noise bandwidth (e.g., RF noise bandwidth) detected on the specific controller wire to which the filter is coupled. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic side elevational view of a conventional chamber  11  adapted to sputter deposit a layer of material;  
         [0014]    [0014]FIG. 2 is a schematic side elevational view of an inventive chamber  111 ;  
         [0015]    [0015]FIG. 3 is a schematic diagram of an exemplary filter  33  for filtering controller wires  401   a - d  in accordance with the present invention; and  
         [0016]    [0016]FIGS. 4A and 4B are diagrammatic side views of an exemplary inventive chamber  411  configured for aluminum nitride deposition, wherein a shutter disk is shown in a closed position (FIG. 4A) and in an open position (FIG. 4B). 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    [0017]FIG. 2 is a schematic side elevational view of an inventive chamber  111 . The inventive chamber  111  comprises the same components as those described with reference to the conventional chamber  11  of FIG. 1. Accordingly, the components which are the same will be briefly enumerated, and only the aspects of the inventive chamber  111  that differ from the conventional chamber  11  will be described in detail.  
         [0018]    Briefly, the chamber  11  includes a chamber enclosure having an enclosing wall  13  and an insulating region  15  adapted to support a sputtering target  19 . A power supply line  21  couples the target  19  to a varying power source  23 . A controller C is coupled to various chamber components via a plurality of controller wires  26 .  
         [0019]    To reduce the noise experienced by the conventional chamber  11 , the inventive chamber  111  comprises one or more of the following features:  
         [0020]    a shield plate  27  coupled to the insulating region  15 , and a grounding mechanism  29  coupled to the shield plate  27  and to the enclosing wall  13  so as to provide electrical grounding therebetween;  
         [0021]    a ground line  31 , separate from the power supply line  21  (i.e., other than the shield portion of the power supply line  21 ) coupled to both the enclosing wall  13  and to the varying power supply  23 ; and/or  
         [0022]    one or more filters  33  coupled to controller wires  26  in series between the one or more chamber components (see FIG. 4), and the controller C.  
         [0023]    In one aspect the ground line  31  is as short as possible, and the varying power supply  23  is installed close to the inventive chamber  111  so as to reduce the length of the power supply line  21 , thereby minimizing detrimental capacitance and inductance that may occur therealong. The grounding mechanism  29  may comprise a metal block which couples to both the shield plate  27  and the enclosure wall  13  via a plurality of springs  35 . The one or more filters  33  may be designed to reject the specific noise bandwidth detected on the specific controller wire  26  to which the filter  33  is coupled. The filters  33  may be designed using a simulation tool in order to obtain a desired frequency response, and may be designed for differential mode filtering or for single mode filtering, as is known in the art.  
         [0024]    [0024]FIG. 3 is a schematic diagram of an exemplary filter  33  for filtering controller wires  401   a - d  in accordance with the present invention. With reference to FIG. 3, the filter  33  comprises channel circuitry  33   a  and  33   b  for filtering controller wires  401   a - d  (e.g., a differential mode filter circuit comprising a plurality of capacitors and inductors configured as shown in FIG. 3). The specific capacitor and inductor values shown in FIG. 3 (e.g., 0.2 microFarad capacitors coupled between each controller wire  401   a - d  and ground, 0.1 microFarad capacitors coupled between the controller wires  401   a - c , and 100 microHenry inductors coupled in series with each controller wire  401   a - d ) are selected to provide low-pass filtering for each controller wire  401   a - d  with a cutoff frequency of about 50 kHz (e.g., so as to reject the 70 kHz or greater pulsed D.C. signal typically applied to a target during sputter deposition of dielectric layers such as aluminum nitride.)  
         [0025]    [0025]FIGS. 4A and 4B are diagrammatic side views of an exemplary inventive chamber  411  configured for aluminum nitride deposition, wherein a shutter disk is shown in a closed position (FIG. 4A) and in an open position (FIG. 4B). With reference to FIGS. 4A and 4B, the deposition chamber  411  generally includes a chamber enclosure wall  413  having an inlet  414  coupled to first and second gas lines  415   a - b . The first and second gas lines  415   a - b  are coupled to a processing gas source  417   a  (e.g., nitrogen) and to a carrier gas source  417   b  (e.g., argon), respectively, and an exhaust outlet  419  is coupled to an exhaust pump  421 . A substrate support  423  is disposed in the lower portion of the deposition chamber  411 , and a target  427  (e.g., an aluminum target for aluminum nitride deposition or a titanium target for titanium nitride deposition) is mounted to an upper surface of the deposition chamber  411 . An AC power supply  429  is operatively coupled to the substrate support  423  so that an AC power signal emitted from the AC power supply  429  will couple through the substrate support  423  to a substrate  431  (FIG. 4B) positioned thereon.  
         [0026]    A clamp ring  433  is operatively coupled to the substrate support  423  so as to press the substrate  431  (FIG. 4B) uniformly against the substrate support  423 . A shutter assembly (not shown) is rotatably mounted within the deposition chamber  411  which selectively positions a shutter disk  435  between the target  427  and the substrate support  423  (i.e., placing the shutter disk  435  in a closed position) as shown in FIG. 4A. Thus, when the shutter disk  435  is in the closed position, deposition material is prevented from depositing on surfaces below the shutter disk  435 . Preferably the shutter disk  435  is positioned between the clamp ring  433  and the substrate support  423  when the shutter disk  435  is in the closed position (as shown in FIG. 4A).  
         [0027]    The target  427  is electrically isolated from the chamber enclosure wall  413  by an insulation region  437 . Any sputtered particles, which accumulate on the insulation member  437  during deposition (described below), may cause an electrical short circuit between the chamber enclosure wall  413  and the target  427  (e.g., preventing the deposition chamber  411  from functioning). Therefore, a process kit part (e.g., a shield  439 ) may be positioned between the target  427  and the insulation region  437  to prevent sputtered particles from accumulating on the insulation region  437 .  
         [0028]    The chamber enclosure wall  413  is preferably grounded so that a negative voltage potential may be selectively generated (e.g., pulsed ON or OFF) between the target  427  and the grounded enclosure wall  413  via a DC power supply  441 . A controller  443  is operatively coupled to the DC power supply  441 , to the gas lines  415   a ,  415   b  via first and second flow controllers  445   a ,  445   b  (e.g., first and second mass flow controllers) to the exhaust outlet  419  via a throttle valve  447  and to the AC power supply  429 . The controller may be programmed to pulse the DC power applied to the target at a radio frequency.  
         [0029]    In operation, to deposit either aluminum nitride or titanium nitride within the deposition chamber  411 , nitrogen (e.g., a processing gas) and a carrier gas (typically a non-reactive species such as Argon) are supplied by the processing gas source  417   a  and by the carrier gas source  417   b , and are flowed into the deposition chamber  411  through the gas lines  415   a - b , respectively, and through the inlet  414  at flow rates regulated by the controller  443 . The nitrogen flow rate is selected so that the nitrogen reacts with the target material forming a nitride layer (e.g., an aluminum nitride layer for an aluminum target or a titanium nitride layer for a titanium target) thereon. The controller  443  also regulates the pressure of the deposition chamber by throttling the rate at which gas is pumped through the exhaust outlet  419  (e.g., via the throttle valve  447 ). Accordingly, although a constant chamber pressure is maintained during deposition, a continuous supply of fresh processing gas is supplied to the deposition chamber  411 .  
         [0030]    The D.C. power supply  441  (e.g., via a command from the controller  443 ) applies a negative voltage to the target  427  with respect to the chamber enclosure wall  413  so as to excite the processing gas/carrier gas within the chamber  411  into a plasma state (e.g., thereby generating a plasma within the chamber  411 ). Ions from the plasma (e.g., argon ions) bombard the target  427 , causing molecules of the nitrided target layer to sputter therefrom. The sputtered molecules travel along linear trajectories from the target  427  and deposit on the substrate  431  (FIG. 4B). The negative voltage applied to the target is turned ON and OFF at a radio frequency rate (e.g., about 70 kHZ), causing the target to be sputtered during power ON state, and allowing a fresh layer of aluminum nitride to form on the target during the power OFF state.  
         [0031]    The use of the grounded shield plate  27 , the ground line  31 , and/or the one or more filters  33 , significantly reduce or eliminate the occurrence of noise in the inventive deposition chamber  411 . Specifically, with use of the inventive chamber, less current couples to chamber components, a higher percentage of the current is returned to the power supply (e.g., via the ground line, and via the grounded shield), and any remaining current may be filtered from the controller lines.  
         [0032]    The foregoing description discloses only the preferred embodiments of the invention; modifications of the above disclosed apparatus and method which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, the invention is not limited to sputtering targets mounted on the top of a chamber; other mounting positions may be employed. Similarly, the AC power of frequencies other than radio frequency and the DC power pulsed at frequencies other than radio frequency may be applied to the target. Filters other than the exemplary circuits described herein may be employed, and any mechanism may be employed to ground the shield plate to the enclosure wall. The present invention also may be used within chambers that employ a coil (e.g., a high density plasma chamber) and/or an RF substrate support bias. For example, to deposit TiN or TaN, a chamber coil typically is employed within a sputtering chamber, the chamber coil is biased via a 2 MHz RF power signal and a substrate support within the chamber is biased with a 13.5 MHz RF signal. The present invention may be employed to reduce noise due to either RF power signal (e.g., by connecting the ground connection of any RF power supplies that are employed to the chamber enclosure wall of the chamber in a manner similar to the ground connection of the pulsed D.C. power supply  23  of FIG. 2).  
         [0033]    Accordingly, while the present invention has been disclosed in connection with the preferred embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.