Patent Publication Number: US-2012024229-A1

Title: Control of plasma profile using magnetic null arrangement by auxiliary magnets

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 61/370,081, filed Aug. 2, 2010, which is herein incorporated by reference. 
    
    
     FIELD 
     Embodiments of the present invention generally relate to substrate processing, and more specifically to substrate processing in physical vapor deposition chambers. 
     BACKGROUND 
     In semiconductor processing, physical vapor deposition (PVD) is a conventionally used process for deposition of materials atop a substrate. A conventional PVD process includes bombarding a target comprising a source material with ions from a plasma, causing the source material to be sputtered from the target. The ejected source material is then accelerated towards the substrate via a negative voltage or bias formed on the substrate, resulting in a deposition of the source material atop the substrate. Following the deposition of the source material, the deposited material may then be resputtered by bombarding the substrate with ions from the plasma, thereby facilitating a redistribution of the material about the substrate. 
     During the PVD process a magnetron may be rotated near a backside of the target to promote uniformity of the plasma. However, during some PVD processes using certain materials, the inventors have observed the target may become magnetized. This magnetization of the target may undesirably affect the plasma uniformity, thereby creating a non-uniform deposition or resputtering of the source material. For example, the plasma may comprise a profile having a bimodal ion distribution profile, resulting in a non-uniform material deposition due to a low resputtering ratio at the center of the substrate. 
     Therefore, the inventors have provided an improved magnetron for use in a PVD chamber. 
     SUMMARY 
     Magnetrons for use in physical vapor deposition (PVD) chambers and methods of use thereof are provided herein. In some embodiments, an apparatus may include a support member having an axis of rotation; a plurality of first magnets coupled to the support member on a first side of the axis of rotation and having a first polarity oriented in a first direction perpendicular to the support member; and a second magnet coupled to the support member on a second side of the axis of rotation opposite the first side and having a second polarity oriented in a second direction opposite the first direction. In some embodiments, the apparatus is capable of forming a magnetic field including one or more magnetic nulls that modulate local plasma uniformity in a physical vapor deposition (PVD) chamber. 
     In some embodiments, a physical vapor deposition processing system may include a chamber having a substrate support for supporting a substrate disposed therein; a target disposed within the chamber, opposite the substrate support; and a magnetron disposed proximate a backside of the target, opposite the substrate support. The magnetron may include a support member having an axis of rotation; a plurality of first magnets coupled to the support member on a first side of the axis of rotation and having a first polarity oriented in a first direction perpendicular to the support member; and a second magnet coupled to the support member on a second side of the axis of rotation opposite the first side and having a second polarity oriented in a second direction opposite the first direction. In some embodiments, the magnetron is capable of forming a magnetic field including one or more magnetic nulls that modulate local plasma uniformity in the chamber. 
     Other and further embodiments of the present invention are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the invention depicted in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is schematic side view of a physical vapor deposition chamber having a magnetron in accordance with some embodiments of the present invention. 
         FIG. 1A  depicts a graph of plasma uniformity profile as a function of varying distance between a substrate and a target in a process chamber. 
         FIG. 2  is a schematic bottom view of a magnetron for use in a physical vapor deposition (PVD) chamber in accordance with some embodiments of the present invention. 
         FIGS. 3-6  depict plasma uniformity profiles for magnetrons in accordance with some embodiments of the present invention. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Embodiments of the present invention generally relate to magnetrons for use with physical vapor deposition (PVD) chambers and PVD chambers using such magnetrons. In some embodiments, the inventive magnetron may advantageously increase the uniformity of a plasma formed within a process chamber by offsetting the effects of a magnetized target during PVD processing. Embodiments of the present invention may further advantageously improve substrate processing by providing uniform plasma sputtering of a target and uniform resputtering of target material deposited atop a substrate. 
       FIG. 1  is a process chamber suitable for use with a magnetron in accordance with some embodiments of the present invention. Examples of suitable PVD chambers include the ALPS® Plus and SIP ENCORE® PVD processing chambers, both commercially available from Applied Materials, Inc., of Santa Clara, Calif. It is contemplated that other processing chambers from other manufactures may also be utilized to perform the present invention. 
     In some embodiments, the process chamber  100  contains a substrate support pedestal  152  for receiving the substrate  101  thereon, and a sputtering source, such as a target  142 . The substrate support pedestal  152  may be located within a grounded enclosure, which may be a chamber wall  150  (as shown) or a grounded shield (not shown). 
     The target  142  may be supported on a grounded conductive aluminum adapter  144  through a dielectric isolator  146 . The target  142  may comprise any material to be deposited on the substrate  101  during sputtering. In some embodiments, for example, where the material is deposited to form a layer (e.g., gate layer, source region, drain region, or the like) of a metal oxide semiconductor (MOS) integrated circuit, the target  142  may comprise a metal. For example, in some embodiments, such as where a cobalt silicide (CoSi 2 ) layer is to be formed atop the substrate  101 , the target  142  may comprise cobalt (Co). 
     The substrate support pedestal  152  has a material-receiving surface facing the principal surface of the target  142  and supports the substrate  101  to be sputter coated in planar position opposite to the principal surface of the target  142 . The substrate support pedestal  152  may support the substrate  101  in a central region  140  of the process chamber  100 . The central region  140  is defined as the region above the substrate support pedestal  152  during processing (for example, between the target  142  and the substrate support pedestal  152  when in a processing position). 
     The substrate support pedestal  152  is vertically movable through a bellows  158  connected to a bottom chamber wall  160  to allow the substrate  101  to be transferred onto the substrate support pedestal  152  through a load lock valve (not shown) in the lower portion of the process chamber  100  and thereafter raised to a deposition, or processing position as depicted in  FIG. 1 . One or more process gases may be supplied from a gas source  162  through a mass flow controller  164  into the lower part of the process chamber  100 . The process gases may be any gases suitable for use with the particular process being performed, for example any reactive or non reactive gases. For example, in some embodiments a non-reactive gas may be supplied in the deposition gas mixture to facilitate maintaining a plasma and/or providing additional ions to the plasma that may be accelerated towards the target  142  to assist sputtering the material from the target  142 . Examples of non-reactive gases include, but are not limited to, argon (Ar), helium (He), xenon (Xe), krypton (Kr), and the like. An exhaust port  168  may be provided and coupled to a pump (not shown) via a valve  166  for exhausting the interior of the process chamber  100  and facilitating maintaining a desired pressure inside the process chamber  100 . 
     A controllable DC power source  148  may be coupled to the process chamber  100  to apply a negative voltage, or bias, to the target  142 . In some embodiments, the controllable DC power source  148  may provide about 1000 to about 38 kW, or in some embodiments, about 40 kW of power, to the target  142 . An RF power supply  156  may be coupled to the substrate support pedestal  152  in order to induce a negative DC bias on the substrate  101 . In some embodiments, the RF power supply  156  may provide about 0 to about 1250 W, or in some embodiments, about 1250 W of power, to the substrate support pedestal  152 . In addition, in some embodiments, a negative DC self-bias may form on the substrate  101  during processing. In other applications, the substrate support pedestal  152  may be grounded or left electrically floating. 
     In operation, power supplied from the controllable DC power source  148  may be applied to a process gas (e.g., the process gases described above) supplied by the gas source  162  to the process chamber  100  causing the process gas to ignite, thereby forming a plasma. Ions from the plasma are accelerated towards the target  142 , sputtering material from the target  142 . The ejected target material is then accelerated towards the substrate  101  via a negative voltage or bias formed on the substrate  101  (e.g., via power supplied to substrate support pedestal  152  from the RF power supply  156  or a negative DC self-bias, described above) facilitating deposition of the target material atop the substrate  101 . 
     The process chamber  100  further includes a grounded bottom shield  180  connected to a ledge  184  of the adapter  144 . A dark space shield  186  is supported on the bottom shield  180  and is fastened to the shield  180  by screws or other suitable manner. The metallic threaded connection between the bottom shield  180  and the dark space shield  186  allows the two shields  180 ,  186  to be grounded to the adapter  244 . The adapter  244  in turn is sealed and grounded to the aluminum chamber wall  150 . Both shields  180 ,  186  are typically formed from hard, non-magnetic stainless steel. 
     The bottom shield  180  extends downwardly in an upper tubular portion  194  of a first diameter and a lower tubular portion  196  of a second diameter. The bottom shield  180  extends along the walls of the adapter  144  and the chamber wall  150  downwardly to below a top surface of the substrate support pedestal  152  and returns upwardly until reaching a top surface of the substrate support pedestal  152  (e.g., forming a u-shaped portion  198  at the bottom). A cover ring  102  rests on the top of the upwardly extending inner portion  103  of the bottom shield  180  when the substrate support pedestal  152  is in its lower, loading position but rests on the outer periphery of the substrate support pedestal  152  when it is in its upper, deposition position to protect the substrate support pedestal  152  from sputter deposition. An additional deposition ring (not shown) may be used to shield the periphery of the substrate  101  from deposition. 
     In some embodiments, a magnet  154  may be disposed about the process chamber  100  for selectively providing a magnetic field between the substrate support pedestal  152  and the target  142 . In some embodiments, the magnet  154  may be disposed about the outside of the chamber wall  150  in a region just above the substrate support pedestal  152  when in processing position. The magnet  154  may be a permanent magnet or an electromagnet and may be coupled to a power source (not shown) for controlling the magnitude of the magnetic field generated by the electromagnet. 
     A magnetron  170  is disposed proximate the top  197  of the process chamber  100 . The magnetron  170  may be positioned in any manner suitable to provide an adequate magnetic field capable of manipulating a plasma within the process chamber  100 . For example, in some embodiments, the magnetron  170  is positioned proximate a back surface  193  of the target  142 . Generally, the magnetron  170  produces a magnetic field within the process chamber  100  proximate a front surface  195  of the target  142  to trap electrons and increase a local plasma density, thereby facilitating an increased sputtering rate of material ejected from the target. 
     Referring to  FIG. 1A , in some embodiments, the inventors have observed that by varying the distance H between the target  142  and substrate  101  a uniformity profile of the plasma formed (i.e., plasma profile  104 ,  108 ) may be affected. For example, in some embodiments, such as where the magnetron  170  produces a magnetic field having a single magnetic null  199 , as the distance H between the target  142  and substrate is increased from a first distance H 1  to a second distance H 2 , the plasma profile may change from having a peak  112  proximate the edge  105  (e.g., plasma profile  104 ) to a center peak plasma profile, having a peak  114  proximate the center  110  (e.g., plasma profile  108 ). Although  FIG. 1A  is described as having only one magnetic null  199  present, the amount of magnetic nulls may vary, for example, as described below with respect to  FIGS. 3-6 . 
     Referring back to  FIG. 1 , in some embodiments, the magnetron  170  generally comprises a support member  179  having an axis of rotation  189 , a plurality of first magnets  181  and a second magnet  183 . The support member  179  may be coupled to a shaft  176  to facilitate rotation about the axis of rotation  189  positioned coincident with the central axis of the chamber  100  and the substrate  101 . In some embodiments, for example such as depicted in  FIG. 1 , the plurality of first magnets  181  may be coupled to the support member  179  on a first side  187  of the axis of rotation  189 . In such embodiments, the second magnet  183  may be coupled to the support member  179  on a second side  185  of the axis of rotation  189 , opposite the first side. 
     The support member  179  may be constructed from any material suitable to provide adequate mechanical strength to secure the plurality of first magnets  181  and second magnet  183  in a static position. For example, in some embodiments, the support member  179  may be constructed from a non-magnetic metal, such as non-magnetic stainless steel. The support member  179  may have any shape suitable to allow the plurality of first magnets  181  and the second magnet  183  to be coupled thereto in a desired position. For example, in some embodiments, the support member  179  may comprise a plate, a disk, a cross member, or the like. In addition, the support member  179  may have any dimensions suitable to allow the plurality of first magnets  181  and the second magnet  183  to be positioned at a desired location with respect to the process chamber  100  and/or target  142 . For example, in embodiments where the support member  179  is a cross member having a rectangular shape, the support member  179  may have a width of about 1.5 to about 3 inches and a length of about 5 to about 7 inches. 
     The axis of rotation  189  may be located at any position across the support member  179 . For example, in some embodiments, the axis of rotation  189  may be disposed proximate a midpoint of the support member  179 . Alternatively, in some embodiments, for example as depicted in  FIG. 1 , the axis of rotation  189  may be offset from the midpoint of the support member  179 . 
     In some embodiments, a counterweight  191  may be coupled to the support member on the second side of the axis of rotation to provide a substantially equal total mass on both sides of the axis of rotation  189 , thereby preventing or limiting eccentric rotation of the magnetron  170 . In some embodiments, the counterweight  191  may be disposed radially outward from the second magnet  183 . The counterweight  191  may have any size or shape suitable to provide the aforementioned weight distribution. In addition, the counterweight  191  may be constructed of any suitable material, for example a non-ferromagnetic metal such as copper. 
     In some embodiments, the plurality of first magnets  181  and the second magnet  183  may each be enclosed in a first housing  177  and second housing  175 , respectively. When present, the first housing  177  and second housing  175  may prevent physical damage to the plurality of first magnets  181  and the second magnet  183  and facilitate coupling of the plurality of first magnets  181  and the second magnet  183  to the support member  179 . The first housing  177  and second housing  175  may be constructed of any material suitable to provide adequate protection and support while not interfering or altering the magnetic field produced by the plurality of first magnets  181  and the second magnet  183 . In some embodiments, the first housing  177  and second housing  175  may each respectively comprise a bottom plate  109 ,  117 , sides  111 ,  113  and a top plate. The top plates may be coupled to the support member  179 . In some embodiments, the support member may comprise a mechanism (not shown), for example a slot or plurality of through holes, to facilitate movement of the plurality of first magnets  181  and the second magnets to different positions along the support member  179 . 
     Referring to  FIG. 2 , the plurality of first magnets  181  may comprise any amount of magnets suitable to provide a desired magnetic field within a process chamber (e.g., process chamber  100  described above). For example in some embodiments, the plurality of first magnets  181  may comprise about 30 to about 50 magnets, or in some embodiments about 60 magnets. In some embodiments, the plurality of first magnets  181  may cumulatively generate a magnetic field having a strength of about 200 to about 500 Gauss. In addition, the plurality of first magnets  181  may be configured in any manner to provide the desired magnetic field. For example, in some embodiments, the plurality of first magnets  181  may be configured in a circular pattern, such as depicted in  FIG. 2 . Alternatively, in some embodiments, the plurality of first magnets  181  may be configured in a cardioid pattern. 
     The plurality of first magnets  181  may be any type of magnets suitable to provide the desired magnetic field. For example, the plurality of first magnets  181  may be electromagnets, or in some embodiments, permanent magnets. In embodiments where the plurality of first magnets  181  are permanent magnets, the permanent magnets may comprise any ferromagnetic material, such as iron (Fe), nickel (Ni), cobalt (Co), alloys thereof, combinations thereof, or the like. 
     The plurality of first magnets  181  may be configured such that the polarity of the plurality of first magnets  181  are oriented perpendicular to the support member  179 . For example, in some embodiments the plurality of first magnets  181  may be configured such that the north (i.e., negative) pole is oriented away from the support member  179 , or in some embodiments, towards the support member  179 . 
     In some embodiments, the plurality of first magnets  181  may comprise a first set of first magnets  208  and a second set of first magnets  212  disposed radially inward from the first set of first magnets  208 . Each of the first set of first magnets  208  and a second set of first magnets  212  may comprise any amount of magnets suitable to provide a desired magnetic field within the process chamber (e.g., process chamber  100  described above). For example in some embodiments, the first set of first magnets  208  may comprise about 20 to about 40 magnets, or in some embodiments about 60 magnets. In such embodiments, the second set of first magnets  212  may comprise about 1 to about 10, or in some embodiments about 20 magnets. The first set of first magnets  208  and a second set of first magnets  212  may be configured in any manner to provide the desired magnetic field. For example, in some embodiments the first set of first magnets  208  and a second set of first magnets  212  may be configured in concentric circles centered on a center point  202 , as depicted  FIG. 2 . Alternatively, the first set of first magnets  208  and a second set of first magnets  212  or cardioid patterns concentrically disposed about the center point  202 . 
     The second magnets  183  may comprise any amount of magnets suitable to provide a desired magnetic field within a process chamber (e.g., process chamber  100  described above). For example in some embodiments, the second magnets  183  may comprise about 1 to about 4 magnets, or in some embodiments about 8 magnets. In addition, the second magnets  183  may be configured in any manner to provide the desired magnetic field. For example, in some embodiments, the second magnets  183  may be arranged in sequential rows, such as depicted in  FIG. 2 . Alternatively, in some embodiments, the plurality of second magnets  183  may be configured in a circular or cardioid pattern, such as described above with respect to the plurality of first magnets  181 . 
     The second magnets  183  may be any type of magnets suitable to provide the desired magnetic field. For example, the second magnets  183  may be electromagnets, or in some embodiments, permanent magnets. In embodiments where the second magnets  183  are permanent magnets, the permanent magnets may comprise any ferromagnetic material, such as iron (Fe), nickel (Ni), cobalt (Co), alloys thereof, combinations thereof, or the like. In some embodiments, the second magnets  183  may comprise the same, or in some embodiments, a different material than that of the plurality of first magnets  181 . 
     The second magnets  183  may be configured such that the polarity of the second magnets  183  are oriented perpendicular to the support member  179 . For example, in some embodiments the second magnets  183  may be configured such that the north (i.e., negative) pole is oriented away from the support member  179 , or in some embodiments, towards the support member  179 . In some embodiments, the orientation of the poles of the second magnets  183  may depend on the orientation of the plurality of first magnets  181 . For example, in embodiments where the plurality of first magnets  181  is configured such that the north (i.e., negative) pole is oriented away from the support member  179 , they second magnets  183  may be oriented such that the north (i.e., negative) pole is oriented towards the support member  179 . 
     The second magnets  183  may generate a magnetic field having any suitable strength to provide a desired interaction with the plurality of first magnets  181 . For example, in some embodiments, the second magnets  183  may generate a magnetic field having a sufficient strength to offset a magnetization on a target disposed beneath the magnetron  170  that may occur during processing (e.g., target  142  of process chamber  100  described above). For example, in some embodiments, the second magnets  183  may cumulatively generate a magnetic field having a strength of about 10 to about 150 Gauss. 
     The plurality of first magnets  181  and the second magnets  183  may be positioned at any point of the support member  179  such that a magnetic field produced by the plurality of first magnets  181  interacts with a magnetic field produced by the second magnets  183  at a desired point beneath the magnetron  170 . For example, in some embodiments, the plurality of first magnets  181  may be positioned such that a distance  204  between a center point  202  of the plurality of first magnets  181  and the axis of rotation  189  is about 60 to about 200 mm. In some embodiments the second magnet  183  may be positioned such that a distance  206  between a center point  284  of the second magnet  183  and the axis of rotation  189  is about 0 to about 150 mm, or in some embodiments, about 65 mm. In addition, the plurality of first magnets  181  and the second magnet  183  may be positioned at any point with respect to one another to achieve a desired interaction between the respective magnetic fields. For example, a distance  214  between the plurality of first magnets  181  and the second magnet  183  may be about 150 to about 300 mm. Of course, other dimensions may be used in PVD chambers having varying dimensions or configured for processing larger or smaller substrates. 
     In some embodiments, within the magnetic field formed within the process chamber  100 , one or more magnetic nulls (one shown)  199  may be formed, as depicted in  FIG. 3 . The location and size of the magnetic nulls  199  may influence a shape of the plasma profile (e.g., plasma profiles  302 ,  304 ). For example, in embodiments where the target  142  comprises a non-ferromagnetic material (e.g., tantalum (Ta), copper (Cu), titanium (Ti), or the like) and the magnetron  170  produces a first magnetic null  199 , the plasma profile  304  may comprise a center peak  306  profile. Alternatively, in embodiments where the target  142  comprises a ferromagnetic material (e.g., cobalt (Co), nickel (Ni), or the like) and the magnetron produces a first magnetic null  199 , the plasma profile  302  may comprise one or more peaks  308  proximate the edge  310  of the plasma profile  302 . 
     In some embodiments, the presence of additional magnetic nulls may further affect the plasma profile. For example, in embodiments where the target  142  comprises a ferromagnetic material and the magnetron  170  produces a second magnetic null  404  disposed radially inward from the first magnetic null  199  and proximate a center line  406  of the process chamber  100 , the plasma profile may be inverted from a plasma profile  304  comprising a center peak  306  profile to a plasma profile  402  comprising one or more peaks  408  proximate the edge  410  of the plasma profile  402 , as depicted in  FIG. 4 . Alternatively, in embodiments where the target  142  comprises a non-ferromagnetic material and the magnetron  170  produces a second magnetic null  404  disposed radially inward from the first magnetic null  199  and proximate a center line  406  of the process chamber  100 , the plasma profile may be inverted from a plasma profile  302  comprising one or more peaks  308  proximate the edge  310  of the plasma profile  302  to a center peak  502  profile, as depicted in  FIG. 5 . 
     Although the above is described with respect to one or two magnetic nulls being formed within the process chamber it is to be noted that any amount of magnetic nulls (i.e., three or more) in any configuration, size and position with respect to the process chamber and one another may be formed to achieve the desired plasma profile. For example, in some embodiments, a third magnetic null  602  may be formed between the first magnetic null  199  and second magnetic null  404 . The third magnetic null  602  may be bigger or smaller than first magnetic null  199  and second magnetic null  404  and may be positioned linearly or above or below the plane of the first magnetic null  199  and second magnetic null  404 . In addition, any amount of magnets positioned in any manner about the magnetron may be utilized to produce the desired amount and location of the magnetic nulls. 
     Although the above is described with respect to a PVD process utilizing a target comprising magnetic materials, it is to be noted that the inventive magnetron may be utilized with any process, for example, including any PVD process depositing non-magnetic target material. 
     Thus, magnetrons for use in physical vapor deposition (PVD) chambers have been provided herein. In some embodiments, a magnetron having plurality of first magnets and a second magnet is provided to advantageously offset the effects of a magnetized target during PVD processing. The present invention may advantageously improve substrate processing by providing uniform plasma sputtering of a target, and therefore, provide uniform deposition of target material atop a substrate. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.