Abstract:
Temperature regulation systems and methods for controlling the temperature of polishing pads used in planarizing micro-device workpieces are disclosed herein. In one embodiment, an apparatus for polishing a workpiece includes a platen defining a planarizing zone and a primary duct system. The platen can have a first duct, and the primary duct system can have a second duct operatively coupled to the first duct of the platen. The second duct is configured to direct a gas flow laterally relative to the planarizing zone. The apparatus also includes a pad support carried by the primary duct system, and a polishing pad carried by the pad support. The pad support can have a plurality of apertures that are in fluid communication with the gas flow in the second duct.

Description:
TECHNICAL FIELD 
     The present invention relates to planarizing and polishing micro-device workpieces including mechanical and chemical-mechanical planarization. In particular, the present invention relates to controlling the temperature of the polishing pad during the planarizing cycle. 
     BACKGROUND 
     Mechanical and chemical-mechanical planarization processes (collectively “CMP”) remove material from the surface of micro-device workpieces in the production of microelectronic devices and other products.  FIG. 1  schematically illustrates a rotary CMP machine  10  with a platen  20 , a carrier head  30 , and a planarizing pad  40 . The CMP machine  10  may also have an under-pad  25  between an upper surface  22  of the platen  20  and a lower surface of the planarizing pad  40 . A drive assembly  26  rotates the platen  20  (indicated by arrow F) and/or 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 head  30  has a lower surface  32  to which a micro-device workpiece  12  may be attached, or the micro-device workpiece  12  may be attached to a resilient pad  34  under the lower surface  32 . The carrier head  30  may be a weighted, free-floating carrier head, or an actuator assembly  36  may be attached to the carrier head  30  to impart rotational motion to the micro-device workpiece  12  (indicated by arrow J) and/or to reciprocate the micro-device workpiece  12  back and forth (indicated by arrow I). 
     The planarizing pad  40  and a planarizing solution  44  define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the micro-device workpiece  12 . The planarizing solution  44  may be a conventional CMP slurry with abrasive particles and chemicals that etch and/or oxidize the surface of the micro-device workpiece  12 , or the planarizing solution  44  may be a “clean” non-abrasive planarizing solution without abrasive particles. In most CMP applications, abrasive slurries with abrasive particles are used on non-abrasive polishing pads, and clean non-abrasive solutions without abrasive particles are used on fixed-abrasive polishing pads. 
     To planarize the micro-device workpiece  12  with the CMP machine  10 , the carrier head  30  presses the micro-device workpiece  12  face-downward against the planarizing pad  40 . More specifically, the carrier head  30  generally presses the micro-device workpiece  12  against the planarizing solution  44  on a planarizing surface  42  of the planarizing pad  40 , and the platen  20  and/or the carrier head  30  moves to rub the micro-device workpiece  12  against the planarizing surface  42 . As the micro-device workpiece  12  rubs against the planarizing surface  42 , the planarizing medium removes material from the face of the micro-device workpiece  12 . 
     The planarity of the finished micro-device workpiece surface is a function of the distribution of planarizing solution under the micro-device workpiece during planarization, the chemical reaction rate, the relative velocity between the polishing pad and the micro-device workpiece surface, and several other factors. Some of these factors are temperature-dependent, such as the chemical reaction rate. Accordingly, it can be difficult to achieve a planar micro-device workpiece surface because often the temperature varies across the workpiece surface during planarization. For example, often the relative velocity between the micro-device workpiece surface and the rotating polishing pad is different across the micro-device workpiece surface, consequently creating a temperature gradient. The temperature gradient can generate different chemical reaction rates in the planarizing solution and, accordingly, different polishing rates across the micro-device workpiece that result in a non-planar micro-device workpiece surface. 
     It is, accordingly, desirable to control the temperature of the planarizing pad to stabilize the temperature-dependent factors that affect the planarity of the micro-device workpiece surface. Previously, attempts have been made to control the temperature by circulating a cooling liquid in the platen. This approach, however, has several disadvantages. It is difficult and expensive to manufacture a liquid system for rotary platens. Liquid systems, for example, require rotary fluid couplings to connect the platen to an external heat exchanger. Liquid systems also require extensive maintenance to prevent leaking and failure of the moving parts. In addition to maintenance expenses, significant downtime may be required to replace or repair rotary couplings or other components. Such significant downtime disrupts production and reduces the throughput of CMP processing. 
     SUMMARY 
     The present invention relates to controlling the temperature of a polishing pad during planarizing and/or polishing of micro-device workpieces. In one embodiment, an apparatus for polishing a workpiece includes a platen defining a planarizing zone and a primary duct system. The platen can have a first duct, and the primary duct system can have a second duct operatively coupled to the first duct of the platen. The second duct is configured to direct a gas flow laterally relative to the planarizing zone. The apparatus also includes a pad support carried by the primary duct system, and a polishing pad carried by the pad support. The pad support can have a plurality of apertures that are in fluid communication with the gas flow in the second duct. As a result, the temperature of the gas flow affects the temperature of the polishing pad to control the temperature at the pad/workpiece interface. 
     In another embodiment, an apparatus for planarizing a micro-device workpiece includes a polishing pad having a planarizing surface for planarizing the micro-device workpiece, a pad support carrying the polishing pad, and a duct system carrying the pad support. The duct system has a duct with at least one inlet and at least one outlet. The duct is configured to direct a gas flow proximate to the pad support in a direction generally parallel to the planarizing surface. 
     In another embodiment, an apparatus for gas-cooling and/or gas-heating a polishing pad includes a platen having a duct system defined by a plurality of channels configured to receive a gas flow, a pad support carried by the platen, and a polishing pad carried by the pad. The pad support is positioned proximate to the plurality of channels so that the gas flow can cool or heat the pad. The polishing pad has a polishing surface for polishing a micro-device workpiece. 
     An embodiment of a temperature control system for use with a platen includes a duct system configured for attachment to the platen, and a pad support carried by the duct system. The duct system has at least one inlet, at least one outlet, and at least one duct coupled to the inlet and the outlet. The duct is configured to direct a gas flow under the pad support to control the temperature of the pad. 
     An embodiment of a method for controlling the temperature of a polishing pad includes causing a gas to flow through a duct system under a polishing pad, and maintaining a desired temperature of the polishing pad with the gas flow. Another embodiment includes flowing gas into a duct system between a polishing pad and a platen, and exhausting the gas from the duct system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view illustrating a portion of a rotary planarizing machine in accordance with the prior art. 
         FIG. 2  is a side cross-sectional view of a planarizing pad and a temperature control system in accordance with one embodiment of the invention. 
         FIG. 3  is a top plan view of the pad support of  FIG. 2 . 
         FIG. 4  is a top plan view of a pad support in accordance with another embodiment of the invention. 
         FIG. 5  is a top plan view of the duct system of  FIG. 2 . 
         FIG. 6  is a top plan view of a duct system in accordance with another embodiment of the invention. 
         FIG. 7  is a side cross-sectional view of the planarizing pad and a temperature control system in accordance with another embodiment of the invention. 
         FIG. 8  is a top cross-sectional view of the platen taken substantially along line A—A of  FIG. 7 . 
         FIG. 9  is a side cross-sectional view of a planarizing pad and a temperature control system in accordance with another embodiment of the invention. 
         FIG. 10  is a side cross-sectional view of the planarizing pad and a temperature control system in accordance with another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure is directed to polishing or planarizing machines and methods for controlling the temperature of polishing pads related to mechanical and/or chemical-mechanical planarization of micro-device workpieces. The term “micro-device workpiece” is used throughout to include substrates upon which and/or in which microelectronic devices, micromechanical devices, data storage elements, and other features are fabricated. For example, micro-device workpieces can be semiconductor wafers, glass substrates, insulative substrates, or many other types of substrates. Furthermore, the terms “planarization” and “planarizing” mean either forming a planar surface and/or forming a smooth surface (e.g., “polishing”). Several specific details of the invention are set forth in the following description and in  FIGS. 2–10  to provide a thorough understanding of certain embodiments of the invention. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that other embodiments of the invention may be practiced without several of the specific features explained in the following description. For example, even though many of the embodiments are described with reference to cooling a planarizing pad, they can also be used to heat or maintain the temperature of the planarizing pad. 
       FIG. 2  is a side cross-sectional view of a planarizing machine  100  having a temperature control system  200  in accordance with one embodiment of the invention. The temperature control system  200  of the illustrated embodiment includes a platen  220 , a pad support  250 , and a duct system  260 . The temperature control system  200  assists in regulating the temperature of a planarizing pad  240  to accurately control the polishing rate and other parameters of the planarization process. Temperature control can be advantageous, for example, when a temperature gradient exists across the planarizing pad  240 , such as when the temperature of the planarizing pad  240  is greater toward the edge  241 . The temperature gradient causes different polishing rates across the workpiece, which, accordingly, result in a non-planar workpiece surface. Moreover, temperature control can be advantageous with some workpieces because the stability of the polishing rate is enhanced when the temperature of the planarizing pad  240  is at or below approximately 70° F. 
     In the illustrated embodiment, the pad support  250  has an upper surface  252  attached to a backside  244  of the planarizing pad  240 , and a lower surface  254  carried by the duct system  260 . The pad support  250  can be stiff to provide support to the planarizing pad  240  during the planarizing process. The pad support  250 , for example, can be a relatively thin sheet of polymeric material or organic material. In one embodiment, the pad support  250  is composed of FR-4, commonly used as a sub-pad in CMP applications. 
     The pad support  250  can also include a plurality of apertures  251  to facilitate heat transfer between the planarizing pad  240  and the gas flowing through the duct system  260 . Each aperture  251  extends from the lower surface  254  of the pad support  250  to the upper surface  252 . In other embodiments, the apertures  251  might not extend completely through the pad support  250 , or the pad support  250  might not have apertures. The apertures  251  in the pad support  250  can be arranged in patterns that provide the desired heat transfer rates across the backside  244  of the planarizing pad  240 . 
       FIGS. 3 and 4  are top plan views of embodiments of aperture patterns suitable for the pad support  250 .  FIG. 3 , for example, shows a pad support  250   a  with a uniform distribution of apertures  251  to provide a uniform heat transfer distribution across the backside  244  ( FIG. 2 ) of the planarizing pad  240  ( FIG. 2 ).  FIG. 4  shows a pad support  450  with a non-uniform arrangement of apertures  251 . The pad support  450  has a greater number of apertures  251  in a perimeter region proximate to an edge  452  of the pad support  450  than in a center region. One advantage of the pad support  450  is that the greater concentration of apertures  251  in the perimeter region provides for greater heat transfer between a perimeter region of the planarizing pad  240  ( FIG. 2 ) and the gas in the duct system  260  ( FIG. 2 ). This can be used to provide more heating or cooling at the perimeter of the planarizing pad  240 . In other embodiments, other pad supports with different arrangements of apertures can be used to provide different temperature distributions. 
     Referring to  FIG. 2 , the platen  220  defines a planarizing zone “P” in which a workpiece is rubbed against the planarizing pad  240 . The platen  220  includes a platen duct  280  that extends from an upper surface  222  to a lower surface  224  of the platen  220 . In the illustrated embodiment, a vacuum and/or blower  290  is coupled to the platen duct  280  to facilitate the movement of gas through the platen duct  280  and the duct system  260 . For example, a vacuum forces gas to flow from the duct system  260 , through the platen duct  280 , and out through a port  276 . Conversely, a blower forces gas in through the port  276 , through the platen duct  280 , and into the duct system  260 . Furthermore, a heat exchanger  292  can be coupled to the platen duct  280  to cool or heat the gas before it enters the platen  220 . Other embodiments may not have a heat exchanger, vacuum and/or blower coupled to the duct system  260 . 
     The duct system  260  includes a plurality of ducts  273  that channel the gas to the apertures  251  under the planarizing pad  240 . The duct system  260  can also provide a continuous flow of gas under the planarizing pad  240  to maintain a desired heat transfer rate. For example, a gas flow “A” can enter the ducts  273  through openings  268 , flow through the ducts  273 , and then be exhausted through a central port  266 . 
       FIG. 5  is a top plan view of one embodiment of a duct system  560 . The duct system  560  includes a plurality of raised sections  510  and a plurality of ducts  573  defined by the plurality of raised sections  510 . The raised sections  510  carry the pad support  250  ( FIG. 2 ) and can be attached to or an integral part of the platen  220  ( FIG. 2 ). In the illustrated embodiment, each duct  573  is defined by a wall  512  of a first raised section  510   a  and a wall  514  of a second raised section  510   b . Each duct  573  has an opening  568  at the perimeter, and the duct system  560  has a central port  566 . In the operation of one embodiment, gas flows in through the openings  568 , along the ducts  573  to pass laterally relative to a planarizing zone, and out through the central port  566  (see arrow A 1 ). Conversely, in another embodiment, gas can flow in through the central port  566  and out through the openings  568  (see arrow A 2 ). 
       FIG. 6  is a top plan view of a duct system  660  in accordance with another embodiment of the invention. The duct system  660  of the illustrated embodiment includes a plurality of arcuate raised sections  610  and a plurality of arcuate ducts  673  defined by the raised sections  610 . Each duct  673  has an opening  668 , and the duct system  660  has a central port  666  similar to the duct system  560  shown in  FIG. 5 . When the platen  220  ( FIG. 2 ) rotates in a direction D 1 , the arcuate shape of the ducts  673  drives gas through the openings  668 , along the ducts  673  laterally relative to a planarizing zone, and out through the central port  666 . 
       FIGS. 5 and 6  show a number of different duct systems that can be used in the planarizing machine  200  of  FIG. 2 . It will be appreciated that duct systems for moving or otherwise providing a flow of gas under the planarizing pad can have other configurations in accordance with other embodiments of the invention. For example, the duct system may not have a plurality of ducts, but rather one duct or chamber with a plurality of small supports or posts to support the pad support  250  ( FIG. 2 ). The ducts, therefore, do not need to be defined by walls that extend along a substantial portion of the radius of the platen. 
       FIG. 7  is a side cross-sectional view of a planarizing machine  700  having a temperature control system in accordance with another embodiment of the invention. The temperature control system of the illustrated embodiment includes a platen  720  having a plurality of channels or ducts  773  between partitions  732 , and a pad support  750  carried by the partitions  732 . In the illustrated embodiment, the pad support  750  does not have apertures; in additional embodiments, the pad support  750  may have apertures and may be similar to the pad support  250  discussed above. 
       FIG. 8  is a top cross-sectional view of one embodiment of the platen  720  taken substantially along line A—A of  FIG. 7 . The ducts  773  are defined by the plurality of partitions  732  and an outer wall  760 . The platen  720  also has at least one opening  770  in each of the ducts  773 , and a central duct  777 . The central duct  777  defines a first duct, and the radial ducts  773  define second ducts. The ducts  773  are spaced apart by a gap  772  between the partitions  732  at the central duct  777 . Referring to  FIG. 7 , in one embodiment, gas can flow in through the openings  770 , along the ducts  773 , and out through the gaps  772  ( FIG. 8 ). The gas flow can then be exhausted through the central duct  777  in the platen  720 . Conversely, in another embodiment, the gas can flow in the opposite direction and be exhausted through the openings  770 . Moreover, the platen  720  can be coupled to a blower, vacuum and/or heat exchanger to facilitate the gas flow, as discussed above with reference to  FIG. 2 . In other embodiments, the plurality of partitions  732  and/or the plurality of ducts  773  can have different shapes or configurations. Furthermore, each duct  773  can have more than one opening  770 . 
       FIG. 9  is a side cross-sectional view of a planarizing machine  900  having a temperature control system in accordance with another embodiment of the invention. The temperature control system of the illustrated embodiment includes a platen  920  having a plurality of ducts  973 , and a pad support  950  carried by the platen  920 . The plurality of ducts  973  are defined by walls or other types of raised sections similar to those illustrated in  FIG. 5  or  6 . The ducts  973  also have a base with an inclined upper surface  922 . The temperature control system also includes an upper duct  980  coupled to the plurality of ducts  973  to connect the ducts  973  to the ambient air or gas. The upper duct  980  has a lip  978  that extends radially outward to prevent the planarizing solution  44  ( FIG. 2 ) from spilling into the upper duct  980 . The pad support  950  has a first aperture  966  that receives the upper duct  980  and a plurality of second apertures  951  arranged in a pattern to provide a desired heat transfer distribution, as explained above. The planarizing machine  900  can also include a planarizing pad  940  having a planarizing surface  942  and a hole  944  through which the upper duct  980  passes. In the illustrated embodiment, if planarizing solution  44  ( FIG. 2 ) spills into the upper duct  980  from the planarizing surface  942 , the spilled planarizing solution  44  ( FIG. 2 ) will flow down the inclined upper surface  922  and run off the platen  920 . In operation, gas can flow in through a port  976  in the upper duct  980 , through the upper duct  980 , through the plurality of ducts  973 , and out through openings  968  (see arrow A 3 ). Conversely, gas can flow in through the openings  968  and out through the port  976  (see arrow A 4 ). 
       FIG. 10  is a side cross-sectional view of a planarizing machine  1000  having a temperature control system in accordance with another embodiment of the invention. The planarizing pad  240  and the temperature control system of the illustrated embodiment are similar to those shown in  FIG. 2 . In the illustrated embodiment, however, the planarizing pad  240  is secured to a pad support  1050  by a vacuum  1090 . The vacuum  1090  is coupled to four vacuum ducts  1010  (two are shown). The vacuum ducts  1010  extend from the backside  244  of the planarizing pad  240 , through the pad support  1050  and a duct system  1060 , to a backside  1044  of a platen  1020 . The vacuum  1090  creates a subatmospheric pressure to hold the planarizing pad  240  onto the pad support  1050 . In other embodiments, the machine may include a different number of vacuum ducts. 
     An advantage of several of the embodiments discussed above is the ability to control or regulate the temperature of the polishing pad during planarization. Controlling the temperature throughout the polishing pad provides better control of the chemical reaction rate throughout the pad and, consequently, results in control of the planarized surface on the micro-device workpiece. Furthermore, the gas flow temperature control systems are less expensive and easier to maintain than liquid control loops. For example, several embodiments of gas duct systems are less susceptible to downtime for leaks compared to liquid cooling systems because they do not need rotary liquid couplings. Furthermore, air can leak through portions of the platen without creating contamination concerns. Another advantage of many of the embodiments discussed above is that they can be used by retrofitting existing planarizing machines. For example, duct systems can be inserted between polishing pads and platens on existing planarizing machines. 
     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.