Patent Publication Number: US-6336850-B1

Title: Slurry dispenser and polishing apparatus

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a polisher for polishing an article such as a semiconductor wafer, and in particular, it relates to a slurry dispensing apparatus for dispensing slurry to a polishing surface of the polisher which is brought into contact with and moved relative to an article to thereby polish the article. 
     A typical prior art polisher includes a turntable with a polishing cloth provided on the top surface thereof constituting a polishing surface, an article carrier for holding an article in such a manner that the article is brought into contact with the polishing surface to polish the article, and a slurry dispenser. In operation, a polishing slurry is dispensed to the polishing surface through a nozzle of the slurry dispenser which is provided above the center portion of the turntable. The slurry dispensed to the center portion of the polishing surface is spread over the polishing surface under the action of a centrifugal force generated by rotation of the turntable. 
     However, it is difficult to enable the slurry to be spread uniformly over the polishing, surface, and accordingly, it is difficult for an article to be polished uniformly as desired. Further, since it is necessary for the slurry to be spread across the entire polishing surface in an outward direction from the center thereof, a substantial amount of slurry is required to be supplied. 
     SUMMARY OF THE INVENTION 
     An object of this invention is therefore to provide a polisher which enables slurry to be spread uniformly and appropriately over an area of the polishing surface to be used in polishing an article, whereby a substantial reduction in an amount of slurry and uniform polishing of an article can be realized. 
     According to this invention, a polisher includes a turntable with a polishing surface provided on the top surface thereof, an article carrier for holding an article to be polished in such a manner that the article is brought into contact with the polishing surface to polish the article, and a slurry dispenser for receiving and dispensing slurry to the polishing surface. The dispenser includes a slurry dispensing member for dispensing slurry to the polishing surface which includes a contact surface facing and substantially contacting the polishing surface, and a slurry dispensing opening including at least one hole provided in the contact surface for dispensing the slurry to the polishing surface therethrough. 
     The opening may be sized in such a manner that it substantially covers substantially an area of the polishing surface which is to be brought into engagement with the article by relative movement between the article and the polishing surface. The dispenser may include a positioning device for positioning the slurry dispensing member in such a manner that the contact surface thereof is pressed against the polishing surface. Further, the slurry dispensing member may include a slurry container portion for containing slurry therein and which is in fluid communication with the above noted opening. The container portion may be divided into a plurality of container sections which are in fluid communication with the opening. The dispenser may comprise a slurry supply device connected to a slurry supply for supplying slurry to the container sections. The slurry supply device may include a plurality of slurry supply paths for connecting the slurry supply to the respective container sections, and an adjusting device for adjusting amounts of slurry to be supplied to the respective container sections through the slurry supply paths. The adjusting device may include valves provided in the respective slurry supply paths which individually adjust the amount of slurry to be supplied to the corresponding container sections. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a polisher in accordance with a first embodiment of the present invention; 
     FIG. 2 is a plan view of a slurry dispensing member of a slurry dispenser of the polisher shown in FIG. 1; 
     FIG. 3 is a cross sectional side elevational view of the slurry dispensing member; 
     FIG. 4 is a plan view of a polisher in accordance with a second embodiment of the present invention; 
     FIG. 5 is a view taken along a line V—V in FIG. 4; 
     FIG. 6 is a plan view of a slurry dispensing member of a slurry dispenser in the polisher shown in FIG. 4; 
     FIG. 7 is a view taken along a line VII—VII in FIG. 4; 
     FIG. 8 a  is a graph showing an example of polishing rates along a diameter of a surface of an article being polished; 
     FIG. 8 b  is a graph showing the polishing rates along the diameter of the surface which has been rectified by adjusting amounts of slurry supplied to a polishing surface contacting the surface of the article; 
     FIG. 9 a  is a graph showing another example of polishing rates along a diameter of a surface of an article being polished; 
     FIG. 9 b  is a graph showing the polishing rates along the diameter of the surface which has been rectified by adjusting amounts of slurry supplied to a polishing surface contacting the surface of the article; 
     FIG. 10 is a graph showing relationships between polishing rates and amounts of supplied slurry in a polisher of the present invention and a prior art polisher; 
     FIG. 11 is a plan view of a polisher in accordance with third embodiment of the present invention; 
     FIG. 12 is a plan view of a slurry dispensing member of a slurry dispenser of the polisher shown in FIG. 11; 
     FIG. 13 is a cross-sectional side elevational view of the slurry dispensing member of FIG. 12; 
     FIG. 14 is a plan view of a slurry dispensing member in accordance with the fourth embodiment of the present invention; and, 
     FIG. 15 is a cross-sectional side elevational view of the slurry dispensing member shown in FIG.  14 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention will be explained with reference to the attached drawings. 
     FIGS. 1 through 3 show a polisher  10  in accordance with a first embodiment of this invention. The polisher  10  includes a turntable  14  with a polishing cloth  16  provided over the top surface of the turntable  14 , a rotatable carrier  18  provided above the polishing cloth  16  for holding an article a to be polished such as a semiconductor wafer, and a slurry dispenser  20  provided above the polishing cloth, only a part of which is shown for clarification. In operation, the turntable is rotated about its axis in a direction designated by an arrow “A”, and the rotatable carrier  18  is rotated about its axis in a direction designated by an arrow “B” keeping the article a held by the carrier  18  in contact with the polishing surface  22  as defined by an upper surface of the polishing cloth  16 . The slurry dispenser  20  is positioned upstream of the rotatable carrier  18  in the direction “A” of rotation of the turntable  14 . 
     The slurry dispenser  20  includes a slurry dispensing member  30  which is rectangular as viewed in FIGS. 1 and 2, has a vertical surrounding wall  32 , and is elongated substantially in a radial direction of the turntable  14 . The slurry dispensing member  30  includes a container portion  34  having a slurry containing cavity defined by the vertical surrounding wall  32  for containing polishing slurry s supplied through a supply nozzle  36 , and an elongated hole  40  at the bottom surface  48  of the slurry dispensing member  30  which is fluidly connected to the slurry containing cavity of the container portion  34 . In this embodiment, the hole  40  is formed as an extension of the slurry containing cavity of the container portion  34 . The slurry dispensing member  30  further includes a plurality of blades  44  provided on an inner surface of a portion of the surrounding wall  32  which is positioned at the downstream side of the slurry containing cavity in the direction “A” of rotation of the turntable  14 . 
     The blades  44  slant relative to the inner surface, and are connected to the inner surface at their radially outer ends. The blades  44  also vertically extend from a lower portion of the inner surface, with the lower ends of the blades  44  being flush with the lower portion of the hole  40 , i.e., the bottom surface  48  of the slurry dispensing member  30 . The blades  44  prevent the slurry contained in the slurry dispensing member  30  from being influenced by forces imposed on the slurry as a result of rotation of the turntable  14 , to thereby enable the slurry to be appropriately dispensed to the polishing surface  22 . 
     The slurry dispenser  20  further includes a positioning device (not shown) adapted to position the slurry dispensing member  30  in such a manner that the bottom surface  48  of the dispensing member  30  defining the lower portion of the hole  40  is pressed against the polishing cloth  16  so that the slurry contained in the slurry dispensing member  30  rarely flows out from the hole  40  when the turntable  14  is not being rotated, but rather flows out to adhere to the polishing surface  22  when the turntable  14  is being rotated. As a result, the slurry dispensed onto the polishing surface  22  forms a uniform thin layer of slurry on the polishing surface  22 . However, it is not necessarily required for the bottom surface  48  to be pressed against the polishing cloth  16 . It is necessary for the bottom surface  48  to substantially contact the polishing surface  22  of the polishing cloth  16  to make it possible to control a flow of the slurry exiting from the hole  40 . 
     A shown in FIG. 1, the slurry dispensing member  20  extends in a radial direction of the turntable  14  over an area of the polishing surface  22  which is to be brought into contact with the article a held by the carrier  18 . 
     FIGS. 4 through 7 show a polisher  110  in accordance with a second embodiment of the present invention. As shown, the polisher  110  is generally similar to that of the first embodiment and includes a turntable  114  with a polishing cloth  116 , an article carrier  118  and a slurry dispenser  120  including a slurry dispensing member  130 . In this embodiment, the slurry dispensing member  130  includes a plurality of partitions  162  to divide a slurry container portion  134  of the slurry dispensing member  130  into a pluarlity of container sections  160  which are arranged in a radial direction of the turntable  114  as viewed in FIG. 4. A cover plate  166  is provided at the top of the slurry dispensing member  130 . Each of the container sections  160  is fluidly connected to a vertically aligned corresponding hole  140  which in defined in the bottom portion of the slurry dispensing member  130  as an extension of the container section  160 . 
     In FIGS. 4,  5  and  7 , there is shown a positioning device  170  for positioning the slurry dispensing member  130  relative to a polishing surface  122  of the turntable  114 , which positioning device is, as stated above, omitted from FIGS. 1 through 3 for the sake of clarity. The positioning device  170  includes a pivot column  172  vertically provided adjacent to the turntable  114 , a horizontal arm  174  provided at the top and of the column  172  and rotatable about an axis of the pivot column  172  and an extendible vertical rod  176  having the construction of a piston/cylinder as shown in FIG. 7 connected between the arm  174  and the slurry dispensing member  130 . The slurry dispensing member  130  is, therefore, rotatable about the axis of the pivot column  172  and movable up and down, whereby the slurry dispensing member  130  can be positioned in such a manner that the slurry dispensing member  130  extends generally in a radial direction of the turntable  114  and the bottom surface  148  thereof is pressed against the polishing cloth  116  of the turntable  114  as stated in connection with the first embodiment. 
     The slurry dispenser  120  further includes a slurry supply device  180  for supplying slurry into the container portion  134  of the slurry dispensing member  130 . The slurry supply device  180  includes a slurry reservoir  182  provided on a side wall of the arm  174 , and is fluidly connected to a slurry supply (not shown) through a pipe  184 . Slurry distributing paths or pipes  188  are fluidly connected to the reservoir  182  at the upper end thereof and to corresponding ones of the container sections  160  at the lower end thereof, so as to supply slurry from the reservoir  182  to the respective container sections  160 . 
     Each of the slurry distributing paths  188  includes a solenoid operated open/close valve  190  to thereby individually control an amount of slurry to be supplied to the corresponding container section  160  by adjusting a time during which the valve  190  is opened. When it is determined that a polishing rate of the central area of a circular surface of an article or a cylindrical semiconductor wafer to be polished is, as shown in FIG. 8 a , smaller than that of the peripheral area of the same, the central container section  160   a  and the container sections adjacent to the central container section  160   a  are, as shown in FIG.  5 . supplied with relatively large amounts of slurry, and the opposite end container sections  160   b  and the container sections adjacent to the opposite end container sections  160   b  are supplied with relatively small amounts of slurry, so that the central container section  160   a  and the container sections adjacent thereto will dispense a relatively large slurry to the polishing surface  122  while the opposite end container sections  160   b  and the container sections adjacent thereto will provide a relatively small amount of slurry, whereby the polishing rate becomes substantially uniform as shown in FIG. 8 b  over the circular surface of the semiconductor wafer a. 
     To the contrary, when it is determined that a polishing rate of the central area of the circular surface of the cylindrical semiconductor wafer a to be polished is, as shown in FIG. 9 a , larger than that of the peripheral area of the same, the central container section  160   a  and the container sections adjacent thereto are supplied with relatively small amounts of slurry, and the opposite end container sections  160   b  and the container sections adjacent thereto are supplied with relatively large amounts of slurry, so that the central container section  160   a  and the container sections adjacent thereto will dispense a relatively small amount of slurry to the polishing surface  122  while the opposite end container sections  160   b  and the container sections adjacent thereto will provide relatively large amounts of slurry, whereby the polishing rate becomes substantially uniform as shown in FIG. 9 b  over the circular surface of the semiconductor wafer a. In the above-noted second embodiment, the open/close valve  190  may be replaced by a flow rate control valve. 
     According to the present invention, slurry is dispensed in an effective manner as stated above and consequently it is possible to conduct polishing of an article with a small amount of slurry as compared with a prior art polisher as stated above. FIG. 10 shows such relationships between amounts of distributed slurries and polishing rates in the present invention and the prior art. The curves “A” and “B” designating the relationships in the present invention and in the prior art, respectively. As can be seen from these curves, in accordance with the present invention, higher polishing rates are achieved with smaller amounts of slurry as compared with the prior art. 
     FIGS. 11 through 13 show another embodiment of the present invention in which a dispensing member  230  is in the shape of a circle and rotatable about an axis thereof in the direction designated by an arrow “C”. The dispensing member  230  includes a circular container portion  234  which in divided by a plurality of partitions  262  into a plurality of container sections  260  arranged in a circle. In this embodiment, the center portion is solid, however, it is possible to make it hollow. At least one slurry nozzle  280  is provided at a particular angular position relative to the circular slurry dispensing member  230  under which the container sections  260  pass successively when the circular slurry dispensing member  230  is rotated, whereby the container sections  260  are uniformly supplied with slurry by the slurry nozzle  280 . The circular dispensing member  230  is positioned upstream of an article carrier  218  for holding an article a to be polished. The dispensing member  230  has a circular slurry dispensing opening at the bottom surface thereof which consists of holes which are formed under the container sections  260  as their extensions. The diameter of the circular opening is substantially the same as that of the article so that the circular opening covers an area of a polishing cloth which is to be brought into contact with the article by rotation of a turntable about its axis. 
     FIGS. 14 and 15 show a slurry dispensing member  330  in accordance with the fourth embodiment of the present invention. The slurry dispensing member  330  is in the shape of a ring and integrally formed around a circular rotatable article carrier  318  which is adapted to hold an article a to be polished in a recess  334  formed in the bottom of the article carrier  318 . The dispensing member  330  is generally the same as that of FIGS. 12 and 13 in construction except that partitions  362  defining container sections  360  are slanted. The slurry dispensing member  330  may be rotatably provided around the article carrier  318  so that the dispensing member  330  can be rotated independently of the article carrier. 
     It is preferable for the slurry dispensing members  30 ,  130 .  230  and  330  as stated above to be rigid to an extent that the dispensing members are not easily deformed under a pressure applied thereto to press them against a polishing cloth. Further, it is preferable for the dispensing members to be corrosion resistant and to be able to sealingly engage with the polishing cloth. It is therefore preferable to use as a material of the slurry dispensing members, for instance, a plastic material selected from polycarbonate, polyvinyle chrolide, polypropylene, polytetrafluoroethylene and so on, or a steel coated with such a plastic material. The polishing cloth may be covered with a rubber sheets Although in the first, third and fourth embodiments, a slurry is supplied to the slurry dispensing member in a batch manner, the slurry may be supplied in a continuous manner as in the second embodiment. In such a case, it is preferable to provide a level sensor in a container potion of a slurry dispensing member to automatically control the level of the slurry. 
     Although this invention has been explained with reference with the drawings, the entire disclosure of Japanese Patent Application H9-297891 filed on Oct. 15, 1997 including specification, claims, drawings and summary is incorporated herein by reference to its entirety.