Patent Publication Number: US-7210989-B2

Title: Planarizing machines and methods for dispensing planarizing solutions in the processing of microelectronic workpieces

Description:
This application is a divisional application of U.S. patent application Ser. No. 09/939,430, entitled “PLANARIZING MACHINES AND METHODS FOR DISPENSING PLANARIZING SOLUTIONS IN THE PROCESSING OF MICROELECTRONIC WORKPIECES,” filed Aug. 24, 2001, now U.S. Pat. No. 6,722,943, issued Apr. 20, 2004; and is related to U.S. patent application Ser. No. 10/828,427, filed Apr. 20, 2004; and U.S. patent application Ser. No. 10/828,017, filed Apr. 20, 2004; all of which are herein incorporated by reference in their entireties. 

   TECHNICAL FIELD 
   The present invention relates to planarizing machines and methods for dispensing planarizing solutions onto a plurality of locations of a processing pad in the fabrication of microelectronic devices. 
   BACKGROUND 
   Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) remove material from the surface of semiconductor wafers, field emission displays, read/write heads or other microelectronic workpieces in the production of microelectronic devices and other products.  FIG. 1  schematically illustrates a CMP machine  10  with a platen  20 , a carrier assembly  30 , and a planarizing pad  40 . The CMP machine  10  may also have an under-pad  25  attached to an upper surface  22  of the platen  20  and the lower surface of the planarizing pad  40 . A drive assembly  26  rotates the platen  20  (indicated by arrow F), or it reciprocates the platen  20  back and forth (indicated by arrow G). Since the planarizing pad  40  is attached to the under-pad  25 , the planarizing pad  40  moves with the platen  20  during planarization. 
   The carrier assembly  30  has a head  32  to which a workpiece  12  may be attached, or the workpiece  12  may be attached to a resilient pad  34  in the head  32 . The head  32  may be a free-floating wafer carrier, or an actuator assembly  36  may be coupled to the head  32  to impart axial and/or rotational motion to the workpiece  12  (indicated by arrows H and I, respectively). 
   The planarizing pad  40  and a planarizing solution  44  on the pad  40  collectively define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the workpiece  12 . The planarizing pad  40  can be a soft pad or a hard pad. The planarizing pad  40  can also be a fixed-abrasive planarizing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution  44  is typically a non-abrasive “clean solution” without abrasive particles. In other applications, the planarizing pad  40  can be a non-abrasive pad composed of a polymeric material (e.g., polyurethane), resin, felt or other suitable materials. The planarizing solutions  44  used with the non-abrasive planarizing pads are typically abrasive slurries with abrasive particles suspended in a liquid. 
   To planarize the workpiece  12  with the CMP machine  10 , the carrier assembly  30  presses the workpiece  12  face-downward against the polishing medium. More specifically, the carrier assembly  30  generally presses the workpiece  12  against the planarizing liquid  44  on a planarizing surface  42  of the planarizing pad  40 , and the platen  20  and/or the carrier assembly  30  move to rub the workpiece  12  against the planarizing surface  42 . As the workpiece  12  rubs against the planarizing surface  42 , material is removed from the face of the workpiece  12 . 
   CMP processes should consistently and accurately produce a uniformly planar surface on the workpiece to enable precise fabrication of circuits and photo-patterns. During the construction of transistors, contacts, interconnects and other features, many workpieces develop large “step heights” that create highly topographic surfaces. Such highly topographical surfaces can impair the accuracy of subsequent photolithographic procedures and other processes that are necessary for forming sub-micron features. For example, it is difficult to accurately focus photo patterns to within tolerances approaching 0.1 micron on topographic surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical surface into a highly uniform, planar surface at various stages of manufacturing microelectronic devices on a workpiece. 
   In the highly competitive semiconductor industry, it is also desirable to maximize the throughput of CMP processing by producing a planar surface on a workpiece as quickly as possible. The throughput of CMP processing is a function, at least in part, of the polishing rate of the planarizing cycle and the ability to accurately stop CMP processing at a desired endpoint. Therefore, it is generally desirable for CMP processes to provide (a) a desired polishing rate gradient across the face of a substrate to enhance the planarity of the finished surface, and (b) a reasonably consistent polishing rate during a planarizing cycle to enhance the accuracy of determining the endpoint of a planarizing cycle. 
   Conventional planarizing machines may not provide consistent polishing rates because of nonuniformities in (a) the distribution of the slurry across the processing pad, (b) the wear of the processing pad, and/or (c) the temperature of the processing pad. The distribution of the planarizing solution across the surface of the processing pad may not be uniform because conventional planarizing machines typically discharge the planarizing solution onto a single point at the center of the pad. This causes a thicker layer of planarizing solution to be at the center of the pad than at the perimeter, which may result in different polishing rates across the pad. Additionally, the nonuniform distribution of the planarizing solution may cause the center region of the pad to behave differently than the perimeter region because many low PH solutions used during planarizing cycles are similar to cleaning solutions for removing stains and waste matter from the pads when polishing metallic surfaces. Such low PH planarizing solutions dispersed locally accordingly may change the physical characteristics differently at the center of the pad than at the perimeter. The nonuniform distribution of planarizing solution also causes a nonuniform temperature distribution across the pad because the planarizing solution is typically at a different temperature than the processing pads. For example, when the planarizing solution is at a lower temperature than the pad, the temperature near the single dispensing point of the planarizing solution is typically lower than other areas of the processing pad. 
   One concern of manufacturing microelectronic workpieces is that the distribution of the planarizing solution can cause variances in the planarized surface of the workpieces. For example, an inconsistent distribution of planarizing solution between the workpiece and the pad can cause certain areas of the workpiece to planarize faster than other areas. Nonuniform pad wear and nonuniform temperature distributions across the processing pad can also cause inconsistent planarizing results that (a) reduce the planarity and uniformity of the planarized surface on the workpieces, and (b) reduce the accuracy of endpointing the planarizing cycles. Therefore, it would be desirable to develop more consistent planarizing procedures and machines to provide more accurate planarization of microelectronic workpieces. 
   SUMMARY OF THE INVENTION 
   The present invention describes machines with solution dispensers for use in chemical-mechanical planarization and/or electrochemical-mechanical planarization/deposition of microelectronic workpieces. One embodiment of such a machine includes a table having a support surface, a processing pad on the support surface, and a carrier assembly having a head configured to hold a microelectronic workpiece. The carrier assembly can further include a drive assembly that carries the head. The machine can also include a solution dispenser separate from the head. The solution dispenser can include a support extending over the pad and a fluid discharge unit or distributor carried by the support. The fluid discharge unit is configured to simultaneously discharge a planarizing solution onto a plurality of separate locations across the pad. 
   In one particular embodiment, the solution dispenser comprises an elongated support extending over the pad at a location spaced apart from a travel path of the head, a fluid passageway carried by the support through which the planarizing solution can flow, and a plurality of nozzles carried by the support. The nozzles are in fluid communication with the fluid passageway to create a plurality of flows of planarizing solution that are discharged onto separate locations across the processing pad. An alternate embodiment of a machine in accordance with the invention includes a solution dispenser comprising an elongated support extending over the pad at a location spaced apart from the travel path of the head, a fluid passageway carried by the support through which a planarizing solution can flow, and an elongated slot extending along at least a portion of the support. The elongated slot is in fluid communication with the fluid passageway to create an elongated flow of planarizing solution. Another alternative embodiment includes an elongated support having a channel extending along at least a portion of the support through which the planarizing solution can flow and a lip along at least a portion of the channel over which the planarizing solution can flow. The lip accordingly defines a weir for depositing an elongated flow of planarizing solution across a portion of the pad. 
   Other embodiments of solution dispensers for the planarizing machine comprise an elongated support extending over the pad at a location spaced apart from the travel path of the head, a fluid passageway carried by the support, a first fluid discharge unit, and a second fluid discharge unit. The elongated support of these embodiments can include a first section and a second section. The first fluid discharge unit can be carried at the first section of the support to discharge a first flow of the planarizing solution onto a first location of the pad. The second fluid discharge unit can be carried by the second section of the support to discharge a second flow of the planarizing solution onto a second location of the pad. The first and second fluid discharge units can be independently controllable from one another so that the first flow of planarizing solution discharged onto the first location of the pad is different than the second flow of planarizing solution discharged onto the second location of the pad. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of a planarizing machine in accordance with the prior art in which selected components are shown schematically. 
       FIG. 2  is a side elevation view of a planarizing system including a planarizing solution dispenser in accordance with an embodiment of the invention with selected components shown in cross-section or schematically. 
       FIGS. 3A–3C  are cross-sectional views showing an embodiment of a planarizing solution dispenser in accordance with the invention. 
       FIG. 4  is a side elevation view of a planarizing system including a planarizing solution dispenser in accordance with another embodiment of the invention with selected components shown in cross-section or schematically. 
       FIG. 5  is a top plan view of the planarizing system of  FIG. 4 . 
       FIG. 6  is a side elevation view of a planarizing system including a planarizing solution dispenser in accordance with an embodiment of the invention with selected components shown in cross-section or schematically. 
       FIG. 7  is a front cross-sectional view of a portion of the planarizing solution dispenser of  FIG. 6 . 
       FIG. 8  is a side elevation view of a planarizing system including a planarizing solution dispenser in accordance with an embodiment of the invention with selected components shown in cross-section or schematically. 
       FIG. 9  is a side elevation view of an embodiment of a planarizing solution dispenser in accordance with the embodiment of  FIG. 8 . 
       FIG. 10  is a side elevation view of a planarizing system including a planarizing solution dispenser in accordance with an embodiment of the invention with selected components shown in cross-section or schematically. 
       FIG. 11  is a side elevation view of a planarizing system including a planarizing solution dispenser in accordance with an embodiment of the invention with selected components shown in cross-section or schematically. 
   

   DETAILED DESCRIPTION 
   The following disclosure describes planarizing machines with planarizing solution dispensers and methods for planarizing microelectronic workpieces. The microelectronic workpieces can be semiconductor wafers, field emission displays, read/write media, and many other workpieces that have microelectronic devices with miniature components (e.g., integrated circuits). Many of the details of the invention are described below with reference to rotary planarizing applications to provide a thorough understanding of such embodiments. The present invention, however, can also be practiced using web-format planarizing machines and electrochemical-mechanical planarizing/deposition machines. Suitable web-format planarizing machines that can be adapted for use with the present invention include U.S. patent application Ser. Nos. 09/595,727 and 09/565,639, which are herein incorporated by reference. A suitable electrochemical-mechanical planarizing/deposition machine that can be adapted for use is shown in U.S. Pat. No. 6,176,992, which is also herein incorporated by reference. A person skilled in the art will thus understand that the invention may have additional embodiments, or that the invention may be practiced without several of the details described below. 
     FIG. 2  is a cross-sectional view of a planarizing system  100  having a planarizing solution dispenser  160  that discharges a planarizing solution  150  in accordance with an embodiment of the invention. The planarizing machine  100  has a table  114  with a top panel  116 . The top panel  116  is generally a rigid plate to provide a flat, solid surface for supporting a processing pad. In this embodiment, the table  114  is a rotating platen that is driven by a drive assembly  118 . 
   The planarizing machine  100  also includes a workpiece carrier assembly  130  that controls and protects a microelectronic workpiece  131  during planarization or electrochemical-mechanical planarization/deposition processes. The carrier assembly  130  can include a workpiece holder  132  to pick up, hold and release the workpiece  131  at appropriate stages of a planarizing cycle and/or a conditioning cycle. The workpiece carrier assembly  130  also generally has a backing member  134  contacting the backside of the workpiece  131  and an actuator assembly  136  coupled to the workpiece holder  132 . The actuator assembly  136  can move the workpiece holder  132  vertically (arrow H), rotate the workpiece holder  132  (arrow I), and/or translate the workpiece holder  132  laterally. In a typical operation, the actuator assembly  136  moves the workpiece holder  132  to press the workpiece  131  against a processing pad  140 . 
   The processing pad  140  shown in  FIG. 2  has a planarizing medium  142  and a contact surface  144  for selectively removing material from the surface of the workpiece  131 . The planarizing medium  142  can have a binder  145  and a plurality of abrasive particles  146  distributed throughout at least a portion of the binder  145 . The binder  145  is generally a resin or another suitable material, and the abrasive particles  146  are generally alumina, ceria, titania, silica or other suitable abrasive particles. At least some of the abrasive particles  146  are partially exposed at the contact surface  144  of the processing pad  140 . Suitable fixed-abrasive planarizing pads are disclosed in U.S. Pat. Nos. 5,645,471; 5,879,222; 5,624,303; and U.S. patent application Ser. Nos. 09/164,916 and 09/001,333; all of which are herein incorporated by reference. In other embodiments the processing pad  140  can be a non-abrasive pad without abrasive particles, such as a Rodel OXB 3000 “Sycamore” polishing pad manufactured by Rodel Corporation. The Sycamore pad is a hard pad with trenches for macro-scale slurry transportation underneath the workpiece  131 . The contact surface  144  can be a flat surface, or it can have a pattern of micro-features, trenches, and/or other features. 
   Referring still to  FIG. 2 , the dispenser  160  is configured to discharge the planarizing solution  150  onto a plurality of separate locations of the pad  140 . In this embodiment, the dispenser  160  includes a support  162  extending over a portion of the pad  140  and a fluid discharge unit or distributor  164  (shown schematically) carried by the support  162 . The support  162  can be an elongated arm that is attached to an actuator  166  that moves the support  162  relative to the pad  140 . The distributor  164  can discharge a flow of the planarizing solution  150  onto the contact surface  144  of the pad  140 . The distributor  164 , for example, can be an elongated slot or a plurality of other openings extending along a bottom portion of the support  162 . In this embodiment, the distributor  164  creates an elongated flow of planarizing solution  150  that simultaneously contacts an elongated portion of the contact surface  144  of the pad  140 . The dispenser  160  accordingly discharges the planarizing solution onto a plurality of separate points or areas of the contact surface  144 . 
     FIG. 3A  is a top cross-sectional view showing the embodiment of the dispenser  160  of  FIG. 2  along line  3 A— 3 A. In this embodiment, the support  162  has a fluid passageway  168  for receiving the planarizing solution from a reservoir (not shown in  FIG. 3A ). The fluid passageway  168  can have a proximal section  167   a  through which the planarizing solution flows into the support and a distal section  167   b  defining a cavity over the processing pad  140 . The distributor  164  in this embodiment can have an elongated slot  169  along the bottom of the support  162  and a valve  170  within the distal section  167   b  of the fluid passageway  168 . The valve  170  has a cavity  172 , and the planarizing fluid can flow through the proximal section  167   a  and into the cavity  172  of the valve  170 . The valve  170  operates to open and close the elongated slot  169  for controlling the flow of planarizing solution onto the contact surface  144 . 
     FIGS. 3B and 3C  are cross-sectional views of the dispenser  160  taken along line  3 B— 3 B shown in  FIG. 3A . Referring to  FIG. 3B , the valve  170  can fit within the distal section  167   b  so that an outer wall of the valve  170  engages or otherwise faces an inner wall of the distal section  167   b . The valve  170  can have an elongated slot  174  or a plurality of holes extending along a portion of the valve.  FIG. 3B  illustrates the valve  170  in an open position in which the slot  174  in the valve  170  is at least partially aligned with the elongated slot  169  in the support  162  so that a fluid F can flow through the slot  169 .  FIG. 3C  illustrates the valve  170  in a closed position in which the slot  174  is not aligned with the elongated slot  169  so that the valve  170  prevents the planarizing solution from flowing through the distributor  164 . In operation, a motor or other actuator (not shown) can rotate the valve  170  within the arm  162  to open and close the slot  169 . 
   Several embodiments of the planarizing machine  100  shown in  FIG. 2  are expected to provide better planarizing results because the dispenser  160  is expected to provide a uniform coating of planarizing solution  150  across the contact surface  144  of the pad  140 . By discharging the planarizing solution  150  along an elongated line across the pad  140 , the planarizing solution  150  is deposited onto a plurality of separate areas of the contact surface  144 . As the pad  140  rotates, the centrifugal force drives planarizing solution  150  off the perimeter of the pad. The wide coverage of the discharge area for the planarizing solution  150  and the spinning motion of the pad  140  act together to provide a distribution of planarizing solution across the pad  140  that is expected to have a uniform thickness. As a result, several embodiments of the planarizing machine  100  are expected to provide more uniform pad wear and temperature distribution across the contact surface  144  of the pad  140 . Therefore, several embodiments of the planarizing machine  100  are expected to provide consistent planarizing results by reducing variances in planarizing parameters caused by a nonuniform distribution of planarizing solution. 
     FIGS. 4 and 5  illustrate the planarizing machine  200  having a solution dispenser  260  in accordance with another embodiment of the invention. The table  114 , the drive assembly  118  and the carrier assembly  130  can be similar to those described above with reference to  FIG. 2 , and thus like reference numbers refer to like components in  FIGS. 2–5 . In this embodiment, the dispenser  260  includes a support  262  and a plurality of nozzles  264  carried by the support  262 . The nozzles  264  are in fluid communication with a fluid passageway  268  that is also carried by the support  262 . The nozzles  264  can be configured to produce gentle, low-velocity flows of planarizing solution  250 . In operation, the planarizing solution  250  is pumped through the fluid passageway  268  and through the nozzles  264 . The nozzles  264  accordingly define a distributor that discharges the planarizing solution  250  onto a plurality of locations of the pad  140 . The planarizing machine  200  is expected to have several of the same advantages as the planarizing machine  100  described above. 
     FIGS. 6 and 7  show a dispenser  360  in accordance with another embodiment of the invention for use with a planarizing machine  300 . Referring to  FIG. 6 , the dispenser  360  has a support  362  with a fluid passageway  368  that extends into a weir  370 .  FIG. 7  is a cross-sectional view of the support  362  taken along line  7 — 7  of  FIG. 6 . Referring to  FIG. 7 , the weir  370  includes a channel or trough  372  that is in fluid communication with the fluid passageway  368  and a lip  374  at the top of the trough  372 . In operation, a planarizing fluid  350  flows through the fluid passageway  368  and fills the trough  372  until the planarizing solution  350  flows over the lip  374 . As shown in  FIG. 6 , the dispenser  360  discharges the planarizing solution  350  onto a plurality of separate locations of the contact surface  144 . Several embodiments of the dispenser  360  are expected to operate in a manner similar to the dispensers  160  and  260  explained above. 
     FIG. 8  shows a planarizing machine  400  having a distributor  460  in accordance with another embodiment of the invention. In this embodiment, the distributor  460  includes a support  462 , a first fluid discharge unit  464   a  carried by a first section of the support  462 , and a second fluid discharge unit  464   b  carried by a second section of the support  462 . The dispenser  460  can further include a fluid passageway  468  coupled to each of the first and second discharge units  464   a  and  464   b . The dispenser  460  also includes a controller  480  coupled to the fluid passageway  468  and/or each of the first and second fluid discharge units  464   a  and  464   b.    
   In operation, the controller  480  independently controls the flow of the planarizing solution to the first and second fluid discharge units  464   a  and  464   b . The first fluid discharge unit  464   a  can accordingly discharge a first flow of planarizing fluid  450   a , and the second fluid discharge unit  464   b  can discharge a second flow of planarizing fluid  450   b . The controller  480  can vary the first and second flows  450   a  and  450   b  of planarizing solution so that the planarizing solution is discharged onto the contact surface  144  in a manner that provides a desired distribution of the planarizing solution across the pad  140 . For example, if the temperature at the perimeter portion of the processing pad  140  is greater than the central portion, then the first fluid flow  450   a  can be increased and/or the second fluid flow  450   b  can be decreased so that more planarizing solution is deposited onto the perimeter portion of the processing pad  140  relative to the central portion to dissipate more heat from perimeter portion of the pad  140 . The controller  480  can be a computer, and each of the fluid discharge units  464   a  and  464   b  can be separate nozzles, slots, weirs, or other structures that can independently discharge separate fluid flows onto the pad  140 . 
   Several embodiments of the planarizing machine  400  are expected to provide good control of planarizing parameters. By independently discharging separate fluid flows onto the pad  140 , the distributor  460  and the controller  480  can be manipulated to change the distribution of the planarizing solution across the surface of the pad according to the actual planarizing results or parameters that are measured during a planarizing cycle. As such, the planarizing machine can create a desired nonuniform distribution of planarizing solution across the pad  140  to compensate for variances in other planarizing parameters. Therefore, several embodiments of the planarizing machine  400  are expected to provide additional control of the planarizing parameters to consistently produce high-quality planarized surfaces. 
     FIG. 9  illustrates a dispenser  560  in accordance with another embodiment of the invention that can be used with the controller  480  of  FIG. 8 . In this embodiment, the dispenser  560  includes a support  562  extending over the pad  140  and a plurality of nozzles  564  (identified individually be reference numbers  564   a–c ) carried by the support  562 . The support  562  can be an arm that is attached to an actuator or a fixed support relative to the pad  140 . The nozzles  564  can include at least a first nozzle  564   a  defining a first fluid discharge unit and a second nozzle  564   b  defining a second fluid discharge unit. The nozzles  564  can also include a third nozzle  564   c  defining a third fluid discharge unit or any other suitable number of nozzles. The dispenser  560  also includes a fluid passageway  568  and a plurality of control valves  570  (identified individually by reference numbers  570   a–c ) coupled between the fluid passageway  568  and the nozzles  564 . In this embodiment, the control valves include a first control valve  570   a  coupled to the first nozzle  564   a , a second control valve  570   b  coupled to the second nozzle  564   b , and a third control valve  570   c  coupled to the third nozzle  564   c . The control valves  570  can be solenoid valves that are operatively coupled to the controller (not shown in  FIG. 9 ) by signal lines  572   a–c.    
   In operation, a planarizing solution flows through the fluid passageway  568  to the control valves  570 , and the controller adjusts the control valves  570  to provide a plurality of separate planarizing solution flows  574   a–c  from the nozzles  564   a–c . The controller can adjust the control valves according to real-time input from sensors during the planarizing cycles of the workpieces and/or from data based upon previous planarizing cycles. This allows the nozzles  564   a–c  to independently discharge the planarizing solution flows  574   a–c  onto separate regions R 1 –R 3  across the pad  140  to compensate for nonuniformities in planarizing parameters across the pad  140 . For example, if region R 1  requires less planarizing solution than region R 2 , then the controller can send a signal to the first control valve  570   a  to reduce the first planarizing solution flow  574   a  from the first nozzle  564   a . This is only an example, and it will be appreciated that many different combinations of flows can be configured by selecting the desired flow rates through the control valves  570 . 
     FIG. 10  shows a planarizing machine  600  in accordance with another embodiment of the invention. The planarizing machine  600  can have several components that are similar to the planarizing machine  400  shown in  FIG. 8 , and thus like reference numbers refer to like components in  FIGS. 8 and 10 . Additionally, the dispenser  460  in  FIG. 10  can be similar to the dispenser  560  of  FIG. 9 . The planarizing machine  600  also includes a sensor assembly  610  that senses a planarizing parameter relative to areas or regions on the contact surface  144  of the pad  140 . The sensor assembly  610  can be embedded in the pad  140 , between the pad  140  and the support surface  116 , and/or embedded in the support surface  116  of the table  114 . The sensor assembly  610  can include temperature sensors that sense the temperature at the contact surface  144 , pressure sensors that sense localized forces exerted against the contact surface  144 , and/or drag force sensors between the workpiece  131  and the contact surface  144 . Suitable sensor assemblies are disclosed in U.S. patent application Ser. Nos. 6,207,764; 6,046,111; 5,036,015; and 5,069,602; and U.S. patent application Ser. Nos. 09/386,648 and 09/387,309, all of which are herein incorporated by reference. In an alternate embodiment, the sensor assembly can be a sensor  612  positioned above the pad  140 . The sensor  612  can be an infrared sensor to measure the temperature gradient across the contact surface, or the sensor  612  can be an optical sensor for sensing another type of parameter. The sensor assembly  610  and the sensor  612  can be coupled to the controller  480  to provide feedback signals of the sensed planarizing parameter. 
   In the operation of the planarizing machine  600 , the sensor assembly  610  senses the planarizing parameter (i.e., temperature, pressure and/or drag force) and sends a corresponding signal to the controller  480 . The sensor assembly  610 , for example, can sense the differences in the planarizing parameter across the contact surface  144  and send signals to the controller  480  corresponding to a distribution of the planarizing parameter across the contact surface  144 . The controller  480  then sends command signals to the fluid discharge units  464   a  and  464   b  according to the sensed planarizing parameters to independently adjust the flow rates of the planarizing solution flows  450   a  and  450   b  in a manner that brings or maintains the planarizing parameter within a desired range. 
     FIG. 11  shows a planarizing machine  700  having a distributor  760  and a controller  780  coupled to the distributor  760  in accordance with another embodiment of the present invention. In this embodiment, the distributor  760  includes a support  762  and a fluid discharge unit  764  moveably coupled to the support  762 . The fluid discharge unit  764  can be slidably coupled to the support  762  to translate along the length of the support  762  (indicated by arrow T). In an alternate embodiment, the fluid discharge unit  764  can be rotatably carried by the support  762  (arrow R). The dispenser  760  can further include an actuator  767  coupled to the fluid discharge unit  764 , and the support  762  can be a track along which the fluid discharge unit  764  can translate. The actuator  767  can be a servomotor or a linear actuator that drives the fluid discharge unit  764  along the support  762 . The actuator  767  can also rotate the fluid discharge unit  764  relative to the support  762  in lieu of, or in addition to, translating the fluid discharge unit  764  along the support  762 . The dispenser  760  can also include a fluid passageway  768  coupled to the fluid discharge unit  764 . The fluid passageway  768  can be a flexible hose that coils up or elongates according to the movement of the fluid discharge unit  764  along the support  762 . 
   The controller  780  is coupled to the actuator  767  to control the motion of the fluid discharge unit  764  relative to the support  762 . The controller  780  can send command signals to the actuator  767  to increase or decrease the velocity of the relative motion between the fluid discharge unit  764  and the arm  762  to adjust the volume of planarizing solution deposited onto different areas of the contact surface  144  of the pad  140 . This embodiment allows a single flow of planarizing solution  750  to have different flow characteristics according to the desired distribution of planarizing solution across the contact surface  144 . 
   From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.