Patent Publication Number: US-2010130107-A1

Title: Method and apparatus for linear pad conditioning

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 61/117,536, filed Nov. 24, 2008, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to polishing a substrate, such as a semiconductor wafer. 
     2. Description of the Related Art 
     In the fabrication of integrated circuits and other electronic devices on substrates, multiple layers of conductive, semiconductive, and dielectric materials are deposited on or removed from a feature side, i.e., a deposit receiving surface, of a substrate. As layers of materials are sequentially deposited and removed, the feature side of the substrate may become non-planar and require planarization and/or polishing. Planarization and polishing are procedures where previously deposited material is removed from the feature side of the substrate to form a generally even, planar or level surface. 
     Chemical mechanical polishing is one process commonly used in the manufacture of high-density integrated circuits to planarize or polish a layer of material deposited on a semiconductor wafer by moving the feature side of the substrate in contact with a polishing pad while in the presence of a polishing fluid. Material is removed from the feature side of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity. 
     Periodic conditioning of the polishing surface is required to maintain a consistent roughness across the polishing surface to facilitate enhanced material removal. The conditioning is typically performed using a rotating conditioning disk that is urged against the polishing surface. The conditioning disk is coupled to a support member that moves the conditioning disk in a sweeping pattern relative to the polishing surface. Providing a specific and/or consistent sweep pattern across the polishing surfaces creates challenges during conditioning that may result non-uniform roughness of the polishing surface. The non-uniform roughness may decrease material removal, which results in decreased throughput. 
     Therefore, there is a need for a method and apparatus that facilitates selective and/or consistent conditioning of the polishing surface. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides an apparatus and method for conditioning a polishing pad using linear motion. In one embodiment, an apparatus for conditioning a polishing pad is described. The apparatus includes a base coupled to a platform, a first arm member having a first end coupled to the base and an opposing second end, a second arm member having a first end pivotably coupled to a second end of the first arm member, and a conditioning disk coupled to a second end of the second arm member opposite the first end of the first arm member. 
     In another embodiment, a method of conditioning a polishing pad is described. The method includes rotating a polishing pad, urging a rotating conditioning disk against a polishing surface of the polishing pad, and moving the conditioning disk in a linear direction relative to the rotating polishing pad to perform a conditioning process. 
     In another embodiment, an apparatus for conditioning a polishing pad is described. The apparatus includes a base coupled to a platform, a first arm member coupled to the base, a second arm member coupled to the first arm member, a conditioning disk coupled to the second arm member opposite the base, and a joint member coupled between the first arm member and the second arm member, the joint member adapted to provide rotation of the first arm member relative to the second arm member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated 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 a plan view of a polishing module. 
         FIG. 2  is a partial cross-sectional view of polishing module of  FIG. 1 . 
         FIG. 3A  shows one embodiment of a conditioning module. 
         FIG. 3B  is a cross-sectional view of one embodiment of a conditioning arm assembly. 
         FIG. 4A  is a side view of a platen assembly showing one embodiment of a conditioning arm assembly in a partially extended position. 
         FIG. 4B  is top view of the platen assembly shown in  FIG. 4A . 
         FIG. 4C  is a side view of the platen assembly of  FIG. 4A  showing the conditioning arm assembly in a partially retracted position. 
         FIG. 4D  is a top view of the platen assembly shown in  FIG. 4C . 
         FIG. 5A  is a side view of a platen assembly showing another embodiment of a conditioning arm assembly in a partially extended position. 
         FIG. 5B  is top view of the platen assembly shown in  FIG. 5A . 
         FIG. 5C  is a side view of the platen assembly of  FIG. 5A  showing the conditioning arm assembly in a partially retracted position. 
         FIG. 5D  is a top view of the platen assembly shown in  FIG. 5C . 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
     DETAILED DESCRIPTION 
     Embodiments of the present invention generally provide a method and apparatus for conditioning a polishing surface of a polishing pad. A conditioning device having a linearly extendable arm configuration is described for use on a polishing pad having a circular configuration. Although not shown, embodiments of the conditioning device may be used on polishing pads having other shapes, such as rectangular polishing pads or belt-type polishing pads. 
       FIG. 1  is a plan view of a polishing module  100  for processing one or more substrates, such as semiconductor wafers. The polishing module  100  includes a platform  106  that at least partially supports and houses a plurality of polishing stations  124 . Each of the plurality of polishing stations  124  are adapted to polish substrates that are retained in the one or more polishing heads  126 . The polishing stations  124  may be sized to interface with the one or more polishing heads  126  simultaneously so that polishing of one or a plurality of substrates may occur at a single polishing station  124  at the same time. The polishing heads  126  are coupled to a carriage  108  that is mounted to an overhead track  128 . The platform  106  also includes one or more load cups  122  adapted to facilitate transfer of a substrate between the polishing heads  126  and a factory interface (not shown) or other device (not shown) by a transfer robot. The load cups  122  generally facilitate transfer between a robot  108  and each of the polishing heads  126 . 
     The overhead track  128  allows each carriage  108  to be selectively positioned around the polishing module  106 . The configuration of the overhead track  128  and carriages  108  facilitates positioning of the polishing heads  126  selectively over the polishing stations  124  and the load cups  122 . In the embodiment depicted in  FIGS. 1-2 , the overhead track  128  has a circular configuration (shown in phantom in  FIG. 1 ) which allows the carriages  108  retaining the polishing heads  126  to be selectively rotated over and/or clear of the load cups  122  and the polishing stations  124 . It is contemplated that the overhead track  128  may have other configurations including elliptical, oval, linear or other suitable orientation. 
     Referring now primarily to  FIG. 1 , two polishing stations  124  are shown, located in opposite corners of the polishing module  106 . Optionally, a third polishing station  124  (shown in phantom) may be positioned in the corner of the polishing module  126  opposite the load cups  122 . Alternatively or additionally, a second pair of load cups  122  (also shown in phantom) may be located in the corner of the polishing module  106  opposite the load cups  122  that are positioned proximate the robot  108 . Additional polishing stations  124  may be integrated in the polishing module  106  in systems having a larger footprint. In one embodiment, each polishing station  124  may be a stand-alone unit adapted to couple to the platform  106 , other polishing stations  124 , and/or a facility floor. In this embodiment, the polishing module  100  includes a modular capability wherein polishing stations, load cups, transfer devices or other equipment may be added or replaced within the platform  106 . 
     Each polishing station  124  generally includes a polishing surface  130 , a conditioning module  132  and a polishing fluid delivery module  134 . The polishing surface  130  is supported on a platen assembly (not shown in  FIG. 1 ) which rotates the polishing surface  130  during processing. In one embodiment, the polishing surface  130  is suitable for at least one of a chemical mechanical polishing and/or an electrochemical mechanical polishing process. 
     The polishing surface  130  is configured, in one embodiment, to accommodate polishing of at least two substrates simultaneously thereon. In such an embodiment, the polishing station  124  includes two conditioning modules  132  and two polishing fluid delivery modules  134  which condition and provide polishing fluid to the region of the polishing surface  130  just prior to interfacing with a respective substrate  170 . Additionally, each of the polishing fluid delivery modules  134  are positioned to provide independently a predetermined distribution of polishing fluid on the polishing surface  130  so that a specific distribution of polishing fluid is respectively interfaced with each substrate during processing. 
       FIG. 2  shows a partial cross-sectional view of polishing module  100  of  FIG. 1 . Specifically, the interface between the overhead track  128  and the carriage  108  is shown. The overhead track  128  is coupled to a support member  212  that is supported by a frame member  204 . The carriage  108  is utilized to position the polishing head  126  over the load cups  122  ( FIG. 1 ) or polishing surface  130 , to sweep the polishing head  126  across polishing surface  130  during processing, or to position the polishing head  126  clear of the load cups  122  and polishing surface  130  for maintenance of the polishing head  126 , the load cups  122  or polishing surface  130 . The carriage  108  is controllably positioned along the overhead track  128  by an actuator  205 . The actuator  205  may be in the form of a gear motor, servo motor, linear motor, sawyer motor or other motion control device suitable for accurately positioning the carriage  108  on the track  128 . In one embodiment, each carriage  108  includes a linear motor that interfaces with a magnetic track coupled to the track  128 . The magnetic track comprises magnets arranged in alternating polarity so that each carriage  108  may be moved independently of the other carriages coupled to the overhead track  128 . 
     In one embodiment, the overhead track  128  is coupled to the frame member  204  while the polishing stations  124  are coupled to a polishing station platform  202 . In this embodiment, each polishing station  124  can be provided as a stand-alone unit or a plurality of polishing stations  124  may be coupled together with the platform  202 . In one embodiment, the polishing station platform  202  and frame member  204  are coupled to a floor  200  of the facility without being connected to each other. The decoupled polishing station platform  202  and frame member  204  allows vibrations associated with the movement of the carriages  108  to be substantially isolated from the polishing surface  130 , thereby minimizing potential impact to polishing results. Moreover, utilization of the polishing station platform  202  without a machine platform provides significant cost savings over conventional designs. 
     The polishing head  126  is coupled to the carriage  108  by a shaft  232 . A motor  234  is coupled to the carriage  108  and is arranged to controllably rotate the shaft  232 , thereby rotating the polishing head  126  and a substrate  201  disposed therein during processing. At least one of the polishing head  126  or carriage  108  includes an actuator (not shown) for controlling the elevation of the polishing head  126  relative to the polishing surface  130 . In one embodiment, the actuator allows the polishing head  126  to be pressed against the polishing surface  130  at about 6 psi or less, such as less than about 1.5 psi. 
     A platen assembly  200  supports a polishing pad  218  that may be made entirely of a dielectric material or include conductive material disposed in a dielectric material. The upper surface of the pad  218  forms the polishing surface  130 . The platen assembly  200  is supported on the polishing station platform  202  by one or more bearings  214 . The platen  216  is coupled by a shaft  206  to a motor  208  that is utilized to rotate the platen assembly  200 . The motor  208  may be coupled by a bracket  210  to the polishing station platform  202 . In one embodiment, the motor  208  is a direct drive motor. It is contemplated that other motors may be utilized to rotate the shaft  206 . In the embodiment depicted in  FIG. 2 , the motor  208  is utilized to rotate the platen assembly  200  such that the pad  218  retained thereon is rotated during processing while the substrate  170  is retained against the polishing surface  130  by the polishing head  126 . It is contemplated, as shown in  FIG. 1 , that the platen assembly  300  may be large enough to support a polishing pad  218  which will accommodate polishing of at least two substrates retained by different polishing heads  126 . In one embodiment, the dielectric polishing pad  218  is greater than 30 inches in diameter, for example, between about 30 and about 52 inches, such as 42 inches. Even though the dielectric polishing pad  218  may be utilized to polish two substrates simultaneously, the pad unit area per number of substrate simultaneously polished thereon is much greater than conventional single substrate pads, thereby allowing the pad service life to be significantly extended, for example, approaching about 2000 substrates per pad. 
     During processing or when otherwise desired, the conditioning module  132  is activated to contact and condition the polishing surface  130 . Additionally, polishing fluid is delivered through the polishing fluid delivery module  134  to the polishing surface  130  during processing and/or conditioning. The distribution of fluid provided by the polishing fluid delivery arm  132  may be selected to control the distribution of polishing fluid across the lateral surface of the polishing surface  130 . It should be noted that only one polishing head  126 , conditioning module  132  and polishing fluid delivery module  134  are depicted in  FIG. 2  for the sake of clarity. 
       FIG. 3A  shows one embodiment of a conditioning module  132 . In this embodiment, the conditioning module  132  is coupled to the polishing station platform  202 . The conditioning module  132  includes a base  302  having a conditioning arm assembly  304  extended therefrom in a cantilevered fashion. The distal end of the arm assembly  304  supports a conditioning head  306 . A conditioning disk  308  is removably attached to the conditioning head  306 . In one embodiment, a first motor or actuator  312  is provided to rotate the arm assembly  304  over the polishing surface  130  during conditioning, and to position the arm assembly  304  clear of the polishing surface  130  when desired. 
     The conditioning arm assembly  304  includes at least two articulatable arms or links, such as a first arm member  330 A and a second arm member  330 B. The conditioning arm assembly  304  also includes at least one pivot point or joint  332  coupling the first and second arm member  330 A,  330 B providing relative movement between the arm members  330 A,  330 B. A second motor  320  is utilized to move the first arm member  330 A relative to the second arm member  330 B. The second motor  320  is coupled to a transmission system  325  that, in one embodiment, includes a shaft  322  (shown in phantom) which is coupled to a drive member  309 , which in turn are coupled to one or more transmission members  326 , which may be belts, wires, or cables. In one embodiment, the transmission members  326 , such as belts are coupled to drive members  309  and the shaft  322  to facilitate movement of the first arm member  330 A relative to the second arm member  330 B such that angular changes are provided between the first arm member  330 A and the second arm member  330 B. 
     Each of the drive members  309  may be a pulley or gear adapted to transfer rotational or translation motion from one element to another. The term “gear” as used herein is intended to generally describe a component that is rotationally coupled to a transmission member  326 , such as a belt, teeth, wires, cables, and is adapted to transmit motion from one element to another. In general, a gear, as used herein, may be a conventional gear type device or pulley type device, which may include but is not limited to components such as, a spur gear, bevel gear, rack and/or pinion, worm gear, a sheave, a timing pulley, and a v-belt pulley. The joint  332  may be a revolute joint, a screw joint, or other joint having one or more degrees of freedom. 
     In one embodiment, the elevation of the conditioning arm assembly  304  may be controlled by a vertical actuator  318 . In one embodiment, the actuator  318  is coupled to a guide  314  that is coupled to the base  302 . The guide  314  may be positioned along a rail  316  which is coupled to the polishing station platform  202  so that the actuator  318  may control the elevation of the conditioning arm assembly  304  and the conditioning head  306 . A collar  324  is provided to prevent liquid from passing between the base  302  and an upper surface  310  of the polishing station platform  220 . 
       FIG. 3B  shows a cross-sectional view of one embodiment of a conditioning arm assembly  304 . In this embodiment, the conditioning arm assembly  304  includes two transmission systems that may be used together or separately. A first transmission system  325  includes a first drive system  351 A coupled to a second drive system  351 B. The first drive system  351 A includes a first gear  352 A coupled to a shaft  353  extending from a first motor  356 A. The first gear  352 A is coupled to a second gear  352 B by a transmission member  354 A, such as a belt. The second gear  352 B is coupled to a shaft  322  that is coupled to a second drive system  351 B. The second drive system includes the third gear  352 C and a fourth gear  352 D which are coupled by a second transmission member  354 B, such as a belt. The fourth gear  352 D is fixedly coupled to a shaft  358  that extends from the first arm member  330 A and is fixedly coupled to the second arm member  330 B. Rotational movement from the first motor  356 A is transmitted to the shaft  358  to provide movement of the second arm member  330 B relative to the first arm member  330 A. 
     In one aspect, the first transmission system  325  includes a transmission ratio (e.g., ratio of diameters, ratio of the number of gear teeth) of the first drive system  351 A and second drive system  351 B that is designed to achieve a desired shape and resolution of an actuation or extension path (e.g., element  450 A and/or  450 B in  FIG. 4A ). The transmission ratio will be hereafter defined as the driving element size to the driven element size, or in this case, for example, the ratio of number of teeth of on third gear  352 C to the number of teeth on the fourth gear  352 D. Therefore, for example, where the first arm member  330 A is rotated 270 degrees which causes the second arm member  330 B to rotate 180 degrees equates to a 0.667 transmission ratio or alternately a 3:2 gear ratio. The term gear ratio is meant to denote that n 1  number of turns of the first gear causes n 2  number of turns of the second gear, or an n 1 :n 2  ratio. Therefore, a 3:2 ratio means that three turns of the first gear will cause two turns of the second gear and thus the first gear must be about two thirds the size of the second gear. In one aspect, the gear ratio of the third gear  352 C to the fourth gear  352 D is between about 3:1 to about 4:3, such as between about 2:1 and about 3:2. 
     In one embodiment, a second transmission system  360  is provided on the conditioning arm assembly  304  that may be utilized along with the first transmission system  325 . In this embodiment, the second transmission system  360  is configured to rotate the conditioning head  306  about a center axis. The second transmission system  360  includes a first gear  362 A coupled to a second motor  356 B by a shaft  361 . The first gear  362 A is coupled to a second gear  362 B and third gear  362 C by a transmission member  363 A. Rotational movement from the second motor  356 B is transmitted to the second gear  362 B and third gear  362 C by the transmission member  363 A. A second transmission member  363 B is coupled between the third gear  362 C and a fourth gear  362 D and fifth gear  362 E to transmit rotational movement from the second motor  356 B to the fifth gear  362 E. A sixth gear  362 F is rotationally coupled to the fifth gear  362 E by a third transmission member  363 C. The sixth gear  362 F is coupled to a shaft  364  that is coupled to the conditioning head  306 . Thus, rotational movement of the second motor  356 B is transmitted to the conditioning head  306  through the conditioning arm assembly  304 . While not shown, bearings and/or seals for each of the gears and shafts may be provided. In one aspect, one or both of the first motor  356 A and second motor  356 B is a stepper motor or DC servomotor. A flexible sleeve or cover  350  may be coupled to the conditioning arm assembly  304  at the joint  332  to contain any particles that may be generated at the joint  332 . 
       FIGS. 4A-4D  are side and plan views of one embodiment of conditioning arm assembly  404 .  FIGS. 4A and 4B  show the conditioning arm assembly  404  in a partially extended position and  FIGS. 4C and 4D  show the conditioning arm assembly  404  in a partially retracted position. In the embodiment shown in  FIGS. 4A-4D , the conditioning arm assembly  404  may be configured similarly to the embodiment of the conditioning arm assembly  304  of  FIGS. 3A and 3B , or include additional or alternative transmission systems. In one embodiment, the conditioning arm assembly  404  may include a first transmission system  325  as described in  FIGS. 3A and 3B  and a second transmission system comprising a motor  415  coupled to the conditioning head  306  to rotate the conditioning head  306 . 
     In  FIGS. 4A-4D , the conditioning arm assembly  404  includes arm members  330 A,  330 B, a first joint  432 A and a second joint  432 B. Each arm member  330 A,  330 B moves relative to the other in a horizontal plane (X direction). The first joint  432 A is proximate the base  302  and may be either fixed to the base  302  to move the first member with the base  302  or movably coupled to the base  302  such that the first arm member  330 A moves at least rotationally relative to the base  302 . The second joint  432 B is configured to pivotally couple the first arm member  330 A to the second arm member  330 B. In one embodiment, the first joint  432 A may be coupled to the first transmission system  325  of  FIG. 3B  to move the first arm member  330 A and second arm member  330 B. In another embodiment, the first joint  432 A may be coupled to an actuator  410 , such as a stepper motor or DC servomotor adapted to rotate the first arm member  330 A relative to the base  302  about axis A. Alternatively or additionally, a joint actuator  420  may be coupled at the second joint  432 B to move the first arm member  330 A relative to the second arm member  330 B about axis B. As another alternative, the conditioning head  306  may be coupled to the motor  415  coupled to the second arm member  330 B. The motor  415  may be a direct drive motor is adapted to provide rotational motion to the conditioning head  306  along axis C. 
       FIG. 4B  is a top view of the conditioning arm assembly  404  of  FIG. 4A . In one embodiment, the conditioning arm assembly  404  provides a first sweep path  450 A to condition the polishing surface  130 . In this embodiment, the conditioning arm assembly  404  moves in a radial direction across the polishing surface  130 . The first sweep path  450 A may also include a linear directional component such as substantial back and forth movement in the Y direction. The conditioning head  306  moves across the polishing surface  130  from a position near the center of the polishing surface  130  to a position near an edge of the polishing surface  130  as shown in  FIGS. 4C and 4D . Alternatively or additionally, the conditioning head  306  may be actuated to move in a second sweep path  450 B, such as an arcuate path. For example, the conditioning head  306  may be moved in an arcuate orientation by actuating the conditioning arm assembly  404  to move about at least one or both of axes A and B. During conditioning, a downward pressure in a range between about 0.1 pound-force (lb-f) to about 10 lb-f, for example about 0.5 lb-f to about 8 lb-f, such as between about 1.0 lb-f to about 3 lb-f may be applied to conditioning head  306  having the conditioning disk coupled thereto. 
       FIGS. 5A-5D  are side and plan views of one embodiment of conditioning arm assembly  504 .  FIGS. 5A and 5B  show the conditioning arm assembly  504  in a partially extended position and  FIGS. 5C and 5D  show the conditioning arm assembly  504  in a partially retracted position. In the embodiment shown in  FIGS. 5A-5D , the conditioning arm assembly  504  may be configured similarly to the embodiment of the conditioning arm assembly  304  of  FIGS. 3A and 3B , or include additional or alternative transmission systems. 
     In  FIGS. 5A-5D , the conditioning arm assembly  504  includes arm members  330 A,  330 B, a first joint  532 A and a second joint  532 B. Each arm member  330 A,  330 B moves relative to the other in a vertical plane (Z direction). 
     The first arm member  330 A is movably coupled by first joint  532 A to the base  302  to rotate the first arm member  330 A relative to the base  302 . The second joint  532 B is configured to pivotally couple the first arm member  330 A to the second arm member  330 B. In one embodiment, the first joint  532 A may be coupled to the first transmission system  325  of  FIG. 3B  to move the first arm member  330 A and second arm member  330 B. In another embodiment, the first joint  532 A may be coupled to an actuator  410 , such as a stepper motor or DC servomotor adapted to rotate the first arm member  330 A relative to the base  302  about axis A′. Alternatively or additionally, a joint actuator  520  may be coupled to the second joint  532 B to move the first arm member  330 A relative to the second arm member  330 B about axis B′. A third joint  532 C may be utilized to couple the conditioning head  306  to the second arm member  330 B. The third joint  532 C may be adapted to float or be configured as a gimbal to allow rotational movement along axis C′. In one embodiment, the conditioning head  306  may be coupled to a motor  415  to rotate the conditioning head  306 . The motor  415  may be a direct drive motor is adapted to provide rotational motion to the conditioning head  306 . The motor  415  may be coupled to a gear box or transmission device (not shown) adapted to translate rotational actuation from the motor  415  to the conditioning head  306 , such as a right angle gear box. 
     The embodiments of the conditioning arm assemblies  304 ,  404  and  504  as described above provide a more accurate and controllable sweep pattern as compared to other conditioning apparatus. The configuration of the conditioning arm assemblies  304 ,  404  and  504  use less space on a polishing module  100  which allows additional space for polishing heads, fluid delivery modules and other hardware used in or on the polishing module  100 . For example, the movement configurations of the first arm member  330 A and the second arm member  330 B may be varied based on allocated space on the polishing module  100 . Factors such as height allowances, width allowances, and other dimensional constraints between other hardware disposed on the polishing module  100  may be considered and the conditioning arm assemblies  304 ,  404  and  504  may be configured accordingly. 
     Additionally, the configuration of the conditioning arm assemblies  304 ,  404  and  504  provides alternative sweep patterns to perform a conditioning process. 
     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, and the scope thereof is determined by the claims that follow.