Abstract:
A polishing system includes a polishing pad having a polishing surface and a conditioner apparatus. The conditioner apparatus includes a conditioner head constructed to receive a conditioning disk for conditioning a surface of the polishing pad, an arm that supports the conditioner head, a base that supports the arm, the arm pivotally connected to the base such that the arm is pivotable about a pivot point to change an angle of inclination of the arm, wherein the pivot point is positioned below the polishing surface of the polishing pad.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to conditioning of polishing pads. 
       BACKGROUND 
       [0002]    An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive, or insulative layers on a silicon wafer. A variety of fabrication processes require planarization of a layer on the substrate. For example, for certain applications, e.g., polishing of a metal layer to form vias, plugs, and lines in the trenches of a patterned layer, an overlying layer is planarized until the top surface of a patterned layer is exposed. In other applications, e.g., planarization of a dielectric layer for photolithography, an overlying layer is polished until a desired thickness remains over the underlying layer. 
         [0003]    Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it against the polishing pad. Abrasive polishing slurry is typically supplied to the surface of the polishing pad. 
         [0004]    After the CMP process is performed for a certain period of time, the surface of the polishing pad becomes glazed due to accumulation of slurry by-products and/or material removed from the substrate and/or the polishing pad. Glazing reduces pad asperity, provides less localized pressure, thus reducing the polishing rate. In addition, glazing may cause the polishing pad to lose some of its capacity to hold the slurry, further reducing the polishing rate. 
         [0005]    Typically, the properties of the glazed polishing pad can be restored by a process of conditioning with a pad conditioner. The pad conditioner is used to remove the unwanted accumulations on the polishing pad and regenerate the surface of the polishing pad to a desirable asperity. Typical pad conditioners include an abrasive head generally embedded with diamond abrasives which can be rubbed against the pad surface of the glazed polishing pad to retexture the pad. 
       SUMMARY 
       [0006]    In some conditioning systems with some polishing recipes and consumable sets, the pad conditioner, particularly the pad conditioner arm, will exhibit significant vibration. The vibration, which is detrimental to the arm, can reduce the effectiveness of the conditioning process. In addition, this vibration is often audible, and in fact can be unacceptably loud. However, by appropriate selection of the pivot point between the conditioner arm and the conditioner base, vibrations can be significantly reduced or eliminated. 
         [0007]    In one aspect, a polishing system includes a platen having a top surface to support a polishing pad and a conditioner apparatus. The conditioner apparatus includes a conditioner head constructed to receive a conditioning disk for conditioning a surface of the polishing pad, an arm that supports the conditioner head, and a base that supports the arm. The arm is pivotally connected to the base such that the arm is pivotable about a pivot point to change an angle of inclination of the arm. The pivot point is positioned below a plane parallel to and positioned 130 mils above the top surface of the platen. 
         [0008]    Implementations may include one or more of the following features. The pivot point may be positioned between 0.05 and 2 inches below the plane. The pivot point may be positioned about 0.1 inch below the plane. The pivot point may be positioned below the top surface of the platen. An actuator may be configured to sweep the arm over the polishing pad. A linear actuator may connect the base to the arm to control an angle of inclination of the arm. 
         [0009]    In another aspect, a polishing system includes a polishing pad having a polishing surface and a conditioner apparatus. The conditioner apparatus includes a conditioner head constructed to receive a conditioning disk for conditioning a surface of the polishing pad, an arm that supports the conditioner head, a base that supports the arm, the arm pivotally connected to the base such that the arm is pivotable about a pivot point to change an angle of inclination of the arm, wherein the pivot point is positioned below the polishing surface of the polishing pad. 
         [0010]    Implementations may include one or more of the following features. The pivot point may be positioned between 0.05 and 2 inches below the polishing surface. The pivot point may be positioned about 0.1 inch below the polishing surface. The pivot point may be positioned below the top surface of the platen. An actuator may be configured to sweep the arm over the polishing pad. A linear actuator may connect the base to the arm to control an angle of inclination of the arm. 
         [0011]    In another aspect, a polishing system includes a platen having a top surface to support a polishing pad and a conditioner apparatus. The conditioner apparatus includes a conditioner head constructed to receive a conditioner disk for conditioning a surface of the polishing pad, an arm that supports the conditioner head, and a base that supports the arm. The arm is pivotally connected to the base such that the arm is pivotable about a pivot point to change an angle of inclination of the arm. The pivot point is positioned the top surface of the platen. 
         [0012]    Implementations may optionally include one or more of the following advantages. Vibration of the pad conditioner, particularly the pad conditioner arm, can be reduced. Effectiveness of the conditioning process can be improved. Noise generated by the pad conditioner can be reduced. 
         [0013]    The details of one or more implementations are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  illustrates a schematic cross-sectional side view of an example of a polishing apparatus. 
           [0015]      FIG. 2  is a top view of a polishing station of a polishing apparatus. 
           [0016]      FIG. 3  is a cross-sectional view of a conditioner apparatus. 
           [0017]      FIGS. 4A and 4B  are graphs of oscillation intensity as a function of frequency for a conditioner apparatus with a pivot point at the top of the platen and below the top of the platen, respectively. 
           [0018]      FIG. 5  is a cross-sectional view of a prior art conditioner apparatus. 
       
    
    
       [0019]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0020]      FIG. 1  illustrates an example of a polishing apparatus  100 . The polishing apparatus  100  includes a rotatable disk-shaped platen  120  on which a polishing pad  110  is situated. The polishing pad  120  can sit on, e.g., be adhesively attached to, a top surface  126  of the platen  120 . 
         [0021]    The platen  120  is operable to rotate about an axis  125 . For example, a motor  122  can turn a drive shaft  124  to rotate the platen  120 . The platen  120  can rotate at about 30-200 rpm. 
         [0022]    The polishing pad  110  can has a polishing surface  116 . The polishing pad  110  can be a two-layer polishing pad with an outer polishing layer  112  and a softer backing layer  114 . The layer that provides the polishing surface  116 , e.g., the outer polishing layer  112 , can be a porous polyurethane. For example, the polishing pad can be an IC-1000 or IC-1010 polishing pad. 
         [0023]    The polishing apparatus  100  can include a port  130  to dispense polishing liquid  132 , such as slurry, onto the polishing pad  110  to the pad. The slurry  132  can include silica abrasive particles, e.g., the slurry can be SS-12. 
         [0024]    The polishing apparatus  100  includes at least one carrier head  140 . While only one carrier head  140  is shown, more carrier heads can be provided to hold additional substrates so that the surface area of polishing pad  110  may be used efficiently. 
         [0025]    The carrier head  140  is operable to hold a substrate  10  against the polishing pad  110 . The carrier head  140  can have independent control of the polishing parameters, for example pressure, associated with each respective substrate. The carrier head  140  can include a retaining ring  142  to retain the substrate  10  below a flexible membrane  144 . Pressurization of one or more chambers behind the membrane  144  controls the pressure applied to the substrate  10 . Although only three chambers are illustrated in  FIG. 1  for ease of illustration, there could be one or two chambers, or four or more chambers, e.g., five chambers. 
         [0026]    The carrier head  140  is suspended from a support structure  150 , e.g., a carousel or a track, and is connected by a drive shaft  152  to a carrier head rotation motor  154  so that the carrier head can rotate about an axis  155 . The carrier head  140  can rotate at about 30-200 rpm. Optionally the carrier head  140  can oscillate laterally, e.g., on sliders on the carousel  150  or track; or by rotational oscillation of the carousel itself. In operation, the platen is rotated about its central axis  125 , and the carrier head is rotated about its central axis  155  and translated laterally across the top surface of the polishing pad. 
         [0027]    The polishing apparatus can also include a polishing pad conditioner  160  to abrade the polishing pad  110  to maintain the polishing pad  110  in a consistent abrasive state. A description of a similar conditioner can be found in U.S. Pat. No. 7,963,826, which is incorporated by reference. The polishing pad conditioner  160  includes a base  162 , an arm  164  that can sweep laterally over the polishing pad  110 , and a conditioner head  166  connected to the base  162  by the arm  164 . The base  162  is mounted on a frame  102  of the polishing apparatus  100  that can also support the other components, e.g., the platen  120  and the support structure  150 . The conditioner head  166  includes an abrasive surface configured to condition the surface  116  of the polishing pad  110 . The abrasive surface can be rotatable, and the pressure of the abrasive surface against the polishing pad can be controllable. 
         [0028]    Referring to  FIG. 2 , in one mode of operation, the polishing pad  110  is conditioned by the conditioner head  166  while the polishing pad  110  polishes a substrate  10  which is mounted on carrier head  140 . In some implementations, the base  162  is pivotally attached to the frame  102  and can rotate about a vertical axis so that arm  164  and sweeps back and forth to move the conditioner head  166  in an oscillatory sweeping motion (shown by arrows S) across polishing pad  110 . The motion of the conditioner head  166  can be synchronized with the motion of carrier head  140  to prevent collision. 
         [0029]    Optionally, the polishing apparatus  100  can include a rinsing cup  168  supported on the frame  102  and positioned in a location such that the arm  164  can position the conditioner head  166  in the cup  168 . The rinsing cup  168  can contain a fluid for rinsing the conditioner head  166 , or a set of nozzles can be mounted in the cup to spray cleaning fluid on the conditioner head  166 . Before and after the conditioning operation, the conditioner head  166  can be positioned in the rinsing cup  168  for cleaning. 
         [0030]    Referring to  FIG. 3 , the conditioner head  166  includes a rotatable end effector  170  that holds a conditioning disk  172 . The conditioning disk  172  has a bottom surface embedded with diamond abrasives which can be rubbed against the surface of the polishing pad to retexture the pad. The conditioning disk  172  can be held in the end effector by magnets, or by mechanical fasteners. A gimbal mechanism can be coupled between the end effector  170  and the conditioner head  166 , the gimbal mechanism allowing the end effector  170  to tilt at an angle relative to the arm  164 . Optionally the end effector  170  is also rotatable. 
         [0031]    Rotation of the end effector  170  can be provided by a motor in the base  162  that is connected by a belt drive that extends through the arm  164  to engage a drive shaft  174  connected to the end effector  170 . A description of a conditioner head can be found in U.S. Pat. No. 6,036,583, incorporated herein by reference. 
         [0032]    The base  162  includes a rotary actuator that includes a rotatable upper portion  180  and a lower portion  182  that is fixed relative to the frame  102 . The arm  164  is affixed to the rotatable upper portion  180 , and rotation of the upper portion  180  causes the lateral sweep of the arm  162  across the polishing pad. 
         [0033]    The rotary actuator includes a sweep motor  184 . The sweep motor  184  can be housed in the lower portion  182 . For example, the sweep motor  184  can drive a drive shaft that is fixed to the upper portion  180  and extends from the upper portion  180  into the lower portion  182 . Alternatively, the sweep motor can be housed in the upper portion  180 . For example, the sweep motor  184  can cause the upper portion  180  to be driven relative to a drive shaft that is fixed to the lower portion  182  and extends from the lower portion  182  into the upper portion  180 . 
         [0034]    Vertical motion of the end effector  170  and control of the pressure of conditioning disk  172  can be provided by a pivot connection  186  between the arm  164  and the upper portion  180  of the base  162 . The pivot connection  186  permits pivoting of the arm  164  about a substantially horizontal axis, so that the arm  164  can swing up and down as shown by arrows A. An actuator  188 , e.g., a pneumatic linear actuator positioned between the upper portion  180  and the arm  164 , permits a controllable angle of inclination of the arm  164 , and thus a controllable height of the conditioner head  166  above the polishing pad  110  and/or controllable pressure of the conditioner disk  172  against the polishing pad  110 . 
         [0035]    Various components, such as the pivot connection  186 , the portion of the arm  164  adjacent the pivot connection, the actuator  188 , the upper portion  180 , and the lower portion  182  can be enclosed in by a cover  189 . 
         [0036]    The pivot point  186   a  of the pivot connection  186  is located below the polishing surface  116  of the polishing pad  110 . The thickness of a typical polishing pad is 130 mils; consequently the pivot point  186   a  of the pivot connection  186  can be located below a reference plane that is parallel to and positioned 130 mils above the top surface  126  of the platen  120 . For example, there can be a distance D of about 0.05 to 2.0 inches between the pivot point  186   a  and the reference plane. In some implementations, the pivot point  186   a  of the pivot connection  186  is located below the top surface  126  of the platen  120 . In some implementations, the pivot point  186   a  of the pivot connection  186  is located above the top surface  126  of the platen  120  but below the polishing surface  116  of the polishing pad  110 . 
         [0037]    Referring to  FIGS. 4A and 4B , a conditioner system with the interface  188  located below the top surface  126  of the platen  120  can exhibit less vibration, e.g., in the 50-75 Hz range, as compared to a conditioner system with the interface  188  coplanar with the polishing surface  116  of the polishing pad  110  (see  FIG. 5 ). 
         [0038]    Without being limited to any particular theory, if the pivot point of the arm is level with the polishing surface of the polishing pad, the friction and force interaction of the conditioner disk and polishing pad can cause stick-slip vibration and chattering of the pad conditioner. By lowering the pivot point below the polishing surface, e.g., below the top surface of the platen, frictional force will tend to reduce the down-force applied by the pad conditioner arm, thus reducing or eliminating stick-slip vibration and chattering. 
         [0039]    A controller  190  (see  FIG. 1 ), e.g., a computer, can be connected to the conditioning apparatus  160  to control the lateral sweep of the arm  164 , the inclination or vertical position of the arm  164 , the rotation rate of the end effector  170 , and the downward force of the end effector  170  on the polishing pad. The computer can include an output device  192 , e.g., a display, and an input device  194 , e.g., a keyboard. 
         [0040]    Although the description above focuses on a conditioner head, the damper system could be applied to other cantilever parts in a polishing system that are susceptible to vibration. For example, the damper system could be applied to an arm that holds a polishing head. 
         [0041]    In some implementations, the vertical motion and pressure control can be provided by a vertical actuator in the base  162  that lifts the entire arm  164  and conditioner head  166 , or by a vertical actuator in the conditioner head  166 , e.g., a pressurizable chamber  174  positioned to apply downward pressure to the end effector  170 . 
         [0042]    The above described polishing apparatus and methods can be applied in a variety of polishing systems. Either the polishing pad, or the carrier heads, or both can move to provide relative motion between the polishing surface and the substrate. For example, the platen may orbit rather than rotate. The polishing pad can be a shape other than circular. Some aspects of the endpoint detection system may be applicable to linear polishing systems, e.g., where the polishing pad is a continuous or a reel-to-reel belt that moves linearly. The polishing layer can be a standard (for example, polyurethane with or without fillers) polishing material, a soft material, or a fixed-abrasive material. The arm could undergo a linearly extension motion rather than an angular sweep. 
         [0043]    As used in the instant specification, the term substrate can include, for example, a product substrate (e.g., which includes multiple memory or processor dies), a test substrate, a bare substrate, and a gating substrate. The substrate can be at various stages of integrated circuit fabrication, e.g., the substrate can be a bare wafer, or it can include one or more deposited and/or patterned layers. The term substrate can include circular disks and rectangular sheets. 
         [0044]    Particular embodiments of the invention have been described. Other embodiments are within the scope of the following claims.