Abstract:
Methods and structures. A planarization method includes: providing a contact structure, where the contact structure includes an axle configured to rotate about an axis of rotation, a plurality of cantilever arms, each arm having a first end connected to the axle, where each arm extends radially outward from the axle; and a plurality of electrically conductive spheres, where at least one sphere is disposed on a second end of each arm; placing a substrate in contact with the spheres, applying an electric voltage to the axle, where the voltage transfers to the substrate, where responsive to the transfer an electrochemical reaction occurs on the substrate; rotating the axle, wherein the spheres revolve about the axis, wherein at least one sphere remains in electrical contact with the substrate; and electrochemical-mechanically planarizing the substrate. Also included is a contact structure, an electrical contact, and an electrical contact method.

Description:
FIELD OF THE INVENTION 
     The invention generally relates to electrical contact devices and electrochemical-mechanical planarization methods. 
     BACKGROUND OF THE INVENTION 
     Electrochemical mechanical planarization (eCMP) requires consistent and reliable anodic contact with the wafer during planarization. Present methods depend on the electrolytic flow rate to maintain anodic contact to the wafer, however, instabilities in the electrolyte flow rate may cause planarization rate instability and tool faults. In addition, present methods for anodic contact are plagued with voltage spikes which may cause post-CMP wafer defects such as hollow metals and/or unstable planarization rates. There exists a need for a method which provides consistent continuous and reliable electrical contact during planarization. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a planarization method, comprising:
         providing a contact structure, said contact structure comprising an axle, said axle having an axis of rotation, said axle configured to rotate about said axis of rotation; a plurality of cantilever arms, each cantilever arm of said plurality of cantilever arms having a first end and a second opposing end, said first end connected to said axle, said each cantilever arm extending radially outward from said axle about perpendicular to said axis of rotation; and a plurality of electrically conductive spheres, wherein at least one electrically conductive sphere of said plurality of electrically conductive spheres is disposed on said second end of each cantilever arm of said plurality of cantilever arms;   placing a substrate in contact with said plurality of electrically conductive spheres, wherein said substrate lies in a plane about perpendicular to said axis of rotation;   applying an electric voltage to said axle, said electric voltage transferring to said substrate, wherein responsive to said transferring an electrochemical reaction occurs on said substrate;   rotating said axle on said axis, wherein said plurality of electrically conductive spheres revolves about said axis, wherein at least one electrically conductive sphere of said plurality of electrically conductive spheres remains in electrical contact with said substrate during said rotating; and   electrochemical-mechanically planarizing said substrate during said rotating.       

     The present invention relates to an electrical contact method, comprising
         providing an axle having an axis of rotation, a plurality of cantilever arms, each cantilever arm of said plurality of cantilever arms having a first end and a second opposing end, said first end connected to said axle, said each cantilever arm extending radially outward from said axle about perpendicular to said axis of rotation, and a plurality of electrically conductive contacts, wherein at least one electrically conductive contact of said plurality of electrically conductive contacts is disposed on said second end of each cantilever arm of said plurality of cantilever arms;   supporting a sample on a support member;   pressing said plurality of electrically conductive contacts against a first surface of said sample; and   after said pressing, revolving said plurality of electrically conductive contacts about said axis of rotation, wherein said at least one electrically conductive contact of said plurality of electrically conductive contacts remains in electrical contact with said first surface.       

     The present invention relates to a contact structure comprising:
         an axle, said axle having an axis of rotation, said axle configured to rotate about said axis of rotation;   a plurality of cantilever arms, each cantilever arm of said plurality of cantilever arms having a first end connected to said axle, said each cantilever arm extending radially outward from said axle about perpendicular to said axis of rotation; and   a plurality of electrically conductive spheres, wherein at least one electrically conductive sphere of said plurality of electrically conductive spheres is disposed on a second end of each cantilever arm of said plurality of cantilever arms.       

     The present invention relates to an electrical contact, comprising:
         an axle having a first axis of rotation, said axle configured to rotate about said axis;   a support arm having a first end attached to said axle, wherein said support arm extends radially outward from said axle about perpendicular to said first axis of rotation;   a contacting unit disposed on a second end of said support arm, said second end configured to support said contacting unit, wherein said contacting unit may freely rotate while being supported by said second end; and   a retaining unit configured to secure said contacting unit to said second end, wherein said retaining unit is configured to allow said contacting unit to freely rotate while simultaneously being secured by said retaining unit and supported by said second end.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the invention are set forth in the appended claims. The invention itself, however, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings. 
         FIG. 1  is an illustration of an example of an embodiment of an electrical contact, in accordance with embodiments of the present invention. 
         FIG. 2  is an illustration of an example of an embodiment of a contact structure, in accordance with embodiments of the present invention. 
         FIG. 3  is an illustration of a top view of an example of a contact structure, in accordance with embodiments of the present invention. 
         FIG. 4  is an illustration of an example of an embodiment of a contact structure, where the contact structure may be part of an electrochemical-mechanical planarization (eCMP) or chemical-mechanical planarization (CMP) system, in accordance with embodiments of the present invention. 
         FIG. 5  is a flow chart illustrating an electrical contact method, in accordance with embodiments of the present invention. 
         FIG. 6  is a flow chart illustrating a chemical-mechanical planarization method, in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although certain embodiments of the present invention will be shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present invention will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as examples of embodiments. The features and advantages of the present invention are illustrated in detail in the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings. Although the drawings are intended to illustrate the present invention, the drawings are not necessarily drawn to scale. 
       FIG. 1  is an illustration of an example of an embodiment of an electrical contact  200  comprising an axle  101  having an axis of rotation  102 , where the axle  101  may be configured to rotate about the axis of rotation  102 . The contact  200  may include a support arm  105  extending radially outward from the axle  101 , the support arm  105  having two ends where a first end may be attached to the axle  101  such that the support arm  105  may be about perpendicular to both the axle  101  and the axis of rotation  102 . 
     The electrical contact  200  may comprise a contacting unit  110  disposed on a second end of the support arm, where the second end of the support arm  105  may be configured to support the contacting unit  110  and allow the contacting unit  110  to freely rotate. For example, the second end of the support arm  105  may be cupped to match the shape of spherical contacting unit  110 . The support arm  105  may comprise a cantilever arm as illustrated in the example of  FIG. 1 , but the support arm&#39;s configuration is not limited to a cantilever arm. For example, the support arm may have additional bracing which may provide support to the support arm  105  and support the contacting unit  110 . 
     The contacting unit  110  may comprise electrically conductive materials, such as metals or conductive polymers. For example, the contacting unit  110  may comprise copper, titanium, tungsten, stainless steel, or a combination of these. In one embodiment, the contacting unit  110  may comprise a conductive or non-conductive material coated with a metal, such as a corrosion resistant metal. The use of a corrosion resistant metal may increase the useful lifetime of the contacting unit  110  by reducing or preventing corrosion to the electrically conductive surface of the contacting unit  110 , as compared with a corrosion susceptible metal. The axle  101 , the support arm  105 , the retaining unit  130 , and the contacting unit  110  may each be electrically conductive and may comprise electrically conductive materials. 
     The electrical contact  200  may comprise a retaining unit  130  configured to prevent removal of the contacting unit  110  and retain the contacting unit  110 . For example, the contacting unit  110  may comprise a sphere where the retaining unit  130  may comprise a ring  135  having a diameter smaller than the diameter of the sphere. When the ring  135  is placed over and held against the sphere such that the sphere is simultaneously secured between the second end of the support arm  105  and the ring  135 , the ring  135  prevents the sphere from being removed while the ring  135  may still allow for the free rotation of the sphere. 
     In an embodiment where the at least one contacting unit  100  is a sphere, free rotation may be described as the rotation of the sphere about a plurality of axes passing through the center of the sphere. In an embodiment where the contact structure  110  is a cylinder, free rotation may be described as rotation of the cylinder about an axis passing through the centers of the bases of the cylinder. 
     The support arm  105  may act as a spring. Such a configuration allows the support arm  105  to apply sufficient force to the contacting unit  110  to press the contacting unit  110  against the retaining unit  135  and hold the contacting unit  110  in place. For example, the entire length of the support arm  105  may act as a spring and may be comprised of a metal (such as spring steel, for example) having sufficient flexible and elastic properties to allow it to automatically return to about its original shape after being bent or strained. In another embodiment, at least one section of the support arm  105  may comprise a spring  108 , such as a torsion spring or a coil spring, where the spring  108  may be configured to allow the support arm  105  to be reversibly and elastically bent or flexed as the spring  108  is strained. 
       FIG. 2  is an illustration of an example of an embodiment of a contact structure  100  having an axle  101 , where the axle  101  may have an axis of rotation  102 , such that the axle  101  may be configured to rotate about the axis of rotation  102 . The contact structure  100  may comprise a plurality of support arms  105 , extending radially outward from the axle  101  and about perpendicular to the axis of rotation  102 , where each support arm  105  has a first end connected to the axle  101 . The axle  101  and the plurality of support arms  105  may be electrically conductive. At least one section of each support arm  105  may act as a spring, such as is described above. 
     The contact structure  100  may comprise a plurality of contacting units  110  such as those described above, where the contacting units  110  may be electrically conductive. At least one contacting unit  110  of the plurality of contacting units  110  may be disposed on a second end of each support arm  106  of said plurality of support arms  106 . The plurality of contacting units  110  may comprise, for example, spheres, cylinders, the like, or a combination of these. 
     The contact structure  100  may comprise at least one retaining device  132  configured to retain or hold the contact structures  110  and to prevent removal or loss of the contact structures  110 . For example, the plurality of contacting units  110  may comprise spheres where the retaining device  132  may comprise a ring  135  or plurality of rings  135  each having a diameter smaller than the diameter of each of the spheres. When the ring  135  is placed over and held against the sphere such that the sphere is simultaneously secured between the second end of the cantilever arm  106  and the ring  135 , the ring  135  prevents the sphere from being removed while the ring  135  may still allow for the free rotation of the sphere. The retaining device  132  may be configured to retain a single contacting unit  110  or a plurality of contacting units  110 , such as 2, 3, 4, 5, or 6 contacting units, for example. 
     The contact structure  100  may comprise at least one polishing pad  125  and at least one support platen  115 . The support platen  115  may be configured to support a sample  120  pressed against the contacting units  110 . The polishing pad  125  may be disposed between the sample  120  and the support platen  115 . For example, the contact structure may comprise a polishing pad and platen such as are found in a system for electrochemical-mechanical planarization (eCMP) of semiconductor wafers. The sample may comprise any material or physical object to which electrical contact is desired. The sample may, for example, comprise a substrate (e.g., a layer or a laminate, a material, and the like) onto which materials may be deposited or adhered. For example, a sample or substrate may comprise materials of the IUPAC Group 11, 12, 13, and 14 elements; plastic material; silicon dioxide, glass, fused silica, mica, ceramic, metals, metals deposited on the aforementioned materials, combinations thereof, and the like. For example, a sample may comprise a dielectric coated silicon process wafer or a copper substrate such as those used in semiconductor manufacturing. 
       FIG. 3  is an illustration of a top view of an example of a contact structure  300  having a central axle  101 , and a plurality of support arms  106  connected to the axle  101  and extending radially outward from the axle  101 . The contact structure  300  may comprise a plurality of contact units  110  such as those described above, where the contact units  110  may be disposed on ends of each of the plurality of support arms  106 . Each support arm  106  may be configured to support more than one contacting unit  110  such as four contacting units  110 , as illustrated in the example of  FIG. 3 . The contact structure may comprise a retaining device  132  configured to retain or hold the contacting units  110  and prevent removal of the contacting units  110 , such as described above. Each retaining device  132  may be configured to hold a single contacting unit  110  or a plurality of contacting units, such as four contacting units  110  as illustrated in the example of  FIG. 2 . 
       FIG. 4  is an illustration of an example of an embodiment of a contact structure  100 , where the contact structure  100  may be part of an electrochemical-mechanical planarization (eCMP) or chemical-mechanical planarization (CMP) system and may comprise a support platen  115  and a polishing pad  125 . The axle  101  may be fixedly connected to the support platen  115 , such that the axle  101  rotates with the platen  115  and polishing pad  125  as the platen  115  and polishing pad  125  rotate about an axis  102 . The contacting units  110  may rotate as the axle  101  rotates and may provide continuous electrical contact to a sample  120  at the contacting units  110  are pressed against the sample  120  by the support arms  106 . An electrical potential may be applied to the platen which may be transmitted through axle  101 , plurality of support arms  106 , and contacting units  110  to the sample  120  facilitating electrochemical mechanical planarization and accompanying electrochemical reactions on the sample. For example, where the sample is a copper process wafer, a cathodic potential may be applied to the platen and transferred to the copper wafer which acts as the anode. Electrochemical reactions during planarization may thus occur on the copper wafer such as:
 
Cu→Cu n+ +ne − 
 
     where n is an integer, facilitating the planarization of copper from the wafer surface. 
       FIG. 5  is a flow chart illustrating an electrical contact method. Step  400  provides an axle having an axis of rotation, a plurality of cantilever arms, each cantilever arm of said plurality of cantilever arms having a first end and a second opposing end, said first end connected to said axle, said each cantilever arm extending radially outward from said axle about perpendicular to said axis of rotation, and a plurality of electrically conductive contacts, wherein at least one electrically conductive contact of said plurality of electrically conductive contacts is disposed on said second end of each cantilever arm of said plurality of cantilever arms. The plurality of electrically conductive contacts may comprise spheres, cylinders, or a combination of these, and may comprise materials such as those described above for the contacting units  110  of  FIG. 1 ,  FIG. 2 ,  FIG. 3 , and  FIG. 4 . 
     In step  405  a sample is supported on a support member. The support member may comprise the combination of the support platen  115  and the polishing pad  125  illustrated in  FIG. 2  and  FIG. 4 , for example. 
     In step  410 , the electrically conductive contacts provided in step  400  are pressed against a first surface of the sample supported in step  405 , such that the contacts are in direct electrical contact with the sample. The cantilever arms may apply an opposing force to sample pressed against the contacts, thus provided continuous electrical contact. For example, where at least one section of at least one cantilever arm comprises a spring, as discussed above, pressing the plurality of electrical contacts against the surface of the sample may exert a compressive force on the spring. In response, the spring may exert an opposing force, forcing the conductive contacts against the sample as the sample. The cantilever arms may be configured such that the force applied to the conductive contacts is sufficiently low enough that it does not damage the first surface of the sample, and sufficiently high enough to maintain contact with the first surface of the sample. 
     In step  415 , the electrically conductive contacts are revolved about the axis of rotation, wherein at least one electrically conductive contact of said plurality of electrically conductive contacts remains in electrical contact with the first surface of the sample. For example, the axle may be rotated about the axis of rotation thus revolving the cantilever arms about the axis, and likewise revolving the conductive contacts disposed on the end of the cantilever arms. Continuous force applied to the first surface by the conductive contacts provides constant electrical contact between the conductive contact and the surface of the sample. An electric voltage or potential may be applied to the electrically conductive contacts. For example, an electric voltage or potential applied to an electrically conductive axle may be transmitted through a connection to an electrically conductive cantilever arm to an electrically conductive contact. An electric current may thus flow from the conductive spheres to the sample. 
       FIG. 6  is a flow chart illustrating a planarization method. Step  500  provides a contact structure, such as is described above. The contact structure may comprise an axle having an axis of rotation, where the axle may be configured to rotate about the axis of rotation. The contact structure may comprise a plurality of cantilever arms, each having a first end and a second opposing end. The first end may be connected to the axle such that each cantilever arm extends radially outward from the axle about perpendicular to the axis of rotation and to the axle. The contact structure may comprise a plurality of electrically conductive units, such as spheres, where at least one electrically conductive unit is disposed on the second end of each cantilever arm of the plurality of cantilever arms. 
     In step  505  a substrate is placed in contact with the plurality of electrically conductive spheres. The substrate may lie in a plane about perpendicular to the axis of rotation. The substrate may comprise a material such as materials of the IUPAC Group 11, 12, 13, and 14 elements; plastic material; silicon dioxide, glass, fused silica, mica, ceramic, metals deposited on the aforementioned materials, combinations thereof, and the like. For example, a sample may comprise a dielectric coated silicon process wafer such as those used in semiconductor manufacturing. 
     In step  510  an electric voltage is applied to the axle, where responsive to applying the current, electric current flows from the axle, through at least one cantilever arms of the plurality of cantilever arms, through the electrically conductive spheres, and to the substrate. As a result of applying the electric voltage, electrochemical reactions may occur on the substrate. 
     In step  515  the axle is rotated on the axis, wherein the plurality of electrically conductive spheres revolves about the axis, wherein at least one electrically conductive sphere of the plurality of electrically conductive spheres remains in electrical contact with the substrate. As described above, each of the cantilever arms may act as a spring and may thus press the conductive sphere against the substrate and maintain electrical contact and allow current to continuously flow to the substrate. By revolving the plurality spheres about the axis, the contact between the conductive spheres and the substrate may constantly be adjusted such that if one contact point becomes resistive (such as due to corrosion or contamination), a second contact point may be made as each sphere freely rotates in contact with the substrate and thus maintains electrical contact with the substrate. 
     In step  520 , the substrate is electrochemical-mechanically planarized while electrical contact is being maintained with the contact structure by simultaneously planarizing while revolving the spheres as in step  515  and applying the voltage as in step  510 . 
     The foregoing description of the embodiments of this invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.