Patent Publication Number: US-7223154-B2

Title: Method for forming and using planarizing pads for mechanical and chemical-mechanical planarization of microelectronic substrates

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 10/621,193, filed Jul. 15, 2003, which is a divisional of U.S. patent application Ser. No. 09/651,778, filed Aug. 30, 2000, now U.S. Pat. No. 6,592,443, issued Jul. 15, 2003, both of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     This invention relates to planarizing pads and to methods and apparatuses for forming and using planarizing pads, such as disposable and/or conditionless planarizing pads for mechanical and chemical-mechanical planarization of microelectronic substrates. 
     BACKGROUND 
     Mechanical and chemical-mechanical planarization processes (“CMP”) are used in the manufacturing of electronic devices for forming a flat surface on semiconductor wafers, field emission displays and many other microelectronic-device substrate assemblies. CMP processes generally remove material from a substrate assembly to create a highly planar surface at a precise elevation in the layers of material on the substrate assembly.  FIG. 1  schematically illustrates an existing web-format planarizing machine  10  for planarizing a substrate  12 . The planarizing machine  10  has a support table  14  with a top-panel  16  at a workstation where an operative portion (A) of a planarizing pad  40  is positioned. The top-panel  16  is generally a rigid plate to provide a flat, solid surface to which a particular section of the planarizing pad  40  may be secured during planarization. 
     The planarizing machine  10  also has a plurality of rollers to guide, position and hold the planarizing pad  40  over the top-panel  16 . The rollers include a supply roller  20 , first and second idler rollers  21   a  and  21   b , first and second guide or pre-operative portion of the planarizing pad  40 , and the take-up roller  23  carries a used or post-operative portion of the planarizing pad  40 . Additionally, the first idler roller  21   a  and the first guide roller  22   a  stretch the planarizing pad  40  over the top-panel  16  to hold the planarizing pad  40  stationary during operation. A motor (not shown) drives at least one of the supply roller  20  and the take-up roller  23  to sequentially advance the planarizing pad  40  across the top-panel  16 . Accordingly, clean pre-operative sections of the planarizing pad  40  may be quickly substituted for used sections to provide a consistent surface for planarizing and/or cleaning the substrate  12 . 
     The web-format planarizing machine  10  also has a carrier assembly  30  that controls and protects the substrate  12  during planarization. The carrier assembly  30  generally has a substrate holder  32  to pick up, hold and release the substrate  12  at appropriate stages of the planarizing process. Several nozzles  33  attached to the substrate holder  32  dispense a planarizing solution  44  onto a planarizing surface  42  of the planarizing pad  40 . The carrier assembly  30  also generally has a support gantry  34  carrying a drive assembly  35  that translates along the gantry  34 . The drive assembly  35  generally has an actuator  36 , a drive shaft  37  coupled to the actuator  36 , and an arm  38  projecting from the drive shaft  37 . The arm  38  carries the substrate holder  32  via a terminal shaft  39  such that the drive assembly  35  orbits the substrate holder  32  about an axis B—B (as indicated by arrow R 1 ). The terminal shaft  39  may also rotate the substrate holder  32  about its central axis C—C (as indicated by arrow R 2 ). 
     The planarizing pad  40  and the planarizing solution  44  define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the substrate  12 . The planarizing pad  40  used in the web-format planarizing machine  10  is typically a fixed-abrasive planarizing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution is a “clean solution” without abrasive particles because the abrasive particles are fixedly distributed across the planarizing surface  42  of the planarizing pad  40 . In other applications, the planarizing pad  40  may be a non-abrasive pad without abrasive particles, composed of a polymeric material (e.g., polyurethane) or other suitable materials. The planarizing solutions  44  used with the non-abrasive planarizing pads are typically CMP slurries with abrasive particles and chemicals to remove material from a substrate. 
     To planarize the substrate  12  with the planarizing machine  10 , the carrier assembly  30  presses the substrate  12  against the planarizing surface  42  of the planarizing pad  40  in the presence of the planarizing solution  44 . The drive assembly  35  then orbits the substrate holder  32  about the axis B—B and optionally rotates the substrate holder  32  about the axis C—C to translate the substrate  12  across the planarizing surface  42 . As a result, the abrasive particles and/or the chemicals in the planarizing medium remove material from the surface of the substrate  12 . 
     The CMP processes should consistently and accurately produce a uniformly planar surface on the substrate assembly to enable precise fabrication of circuits and photo-patterns. During the fabrication of transistors, contacts, interconnects and other features, many substrate assemblies develop large “step heights” that create a highly topographic surface across the substrate assembly. Yet, as the density of integrated circuits increases, it is necessary to have a planar substrate surface at several intermediate stages during substrate assembly processing because non-uniform substrate surfaces significantly increase the difficulty of forming sub-micron features. For example, it is difficult to accurately focus photo patterns to within tolerances approaching 0.1 micron on non-uniform substrate surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical substrate surface into a highly uniform, planar substrate surface. 
     One problem with conventional CMP methods is that the planarizing surface  42  of the planarizing pad  40  can become glazed with accumulations of slurry and/or material removed from the substrate  12  or the planarizing pad  40 . One conventional approach to addressing this problem is to remove the accumulations by conditioning the planarizing pad  40 , for example, by abrading the planarizing pad  40  with an abrasive disk (not shown). A drawback with this approach is that the equipment required for conditioning the planarizing pad  40  adds complexity to the planarizing machine  10  and, if the conditioning operation is performed separately from the planarizing operation, it reduces the time that the planarizing pad  40  is available for planarizing. Conventional conditioning processes can thus limit the overall efficiency of the apparatus. 
     One approach to address this drawback is to eliminate the need to condition the pad by making the planarizing surface or the entire planarizing pad disposable. For example, U.S. application Ser. No. 09/001,333 discloses a disposable planarizing pad film made from materials such as Mylar or polycarbonate. The pads disclosed in application Ser. No. 09/011,333 can have microfeatures of different heights that entrap small volumes of an abrasive slurry and maintain the slurry in contact with the substrate. The microfeatures can be formed using a variety of techniques, such as embossing or photo-patterning. 
     One conventional method for photo-patterning is shown schematically in  FIGS. 2A–2E . As shown in  FIG. 2A , a photopolymer composite  50  is formed by disposing a photopolymer resist material  53  on a substrate polymer  52  which is supported by support layer  51 . The photopolymer resist material  53  is then exposed to a radiation source  63 . A mask  60  having opaque portions  61  and transmissive portions  62  blocks the radiation emitted from the radiation source  63  from striking unexposed portions  55  of the photopolymer resist material  53 , while allowing the radiation to strike exposed portions  54 . 
     As shown schematically in  FIG. 2B , the exposed portions  54  change chemical characteristics as a result of being exposed to the radiation source  63 . For example, when the photopolymer resist material  53  is initially soluble in a selected solvent, exposure to the selected radiation can change the exposed portions  54  to become insoluble in the selected solvent. Alternatively, when the photopolymer resist material is initially insoluble in the selected solvent, exposure to the selected radiation can make the exposed portions  54  soluble. In either case, the solubility of the unexposed portions  55  remains unchanged. 
     When the exposed portions  54  are rendered insoluble by exposure to the selected radiation,  FIG. 2C  schematically illustrates the photopolymer composite  50  after being rinsed with the selected solvent. The exposed portions  54  of the photopolymer resist material  53  remain intact and the unexposed portions have been removed by the solvent to expose the substrate polymer  52  below. The substrate polymer  52  is then etched to remove the portions of the substrate polymer material from between the exposed portions  54  of the photopolymer resist material  53  and form recesses  70 , as is shown in  FIG. 2D . The exposed portions  54  of the photopolymer resist material  53  are then removed, leaving the finished article (shown in  FIG. 2E ) having protrusions  76  separated by the recesses  70 . 
     One drawback with the method discussed above with reference to  FIGS. 2A–2E  is that separate steps are required to place the photopolymer resist material  53  on the substrate polymer  52  and remove the photopolymer resist material  53  from the substrate polymer  52  after the recesses  70  are formed. Furthermore, the solvent that removes the photopolymer resist material  53  may be different than the solvent that removes the underlying substrate polymer  52 , requiring the manufacturer to keep multiple solvents on hand. 
     One method for reducing the number of manufacturing steps and solvents associated with photoresistive techniques used in the printing industry is to etch the recesses  70  directly in a photosensitive material. For example, Cyrel®, available from E.I. du Pont de Nemours and Co. of Wilmington, Del., is used to make printing plates by forming surface features directly in a photosensitive material without separately etching the material below. However, such printing plates are generally unsuitable for application to planarizing pads because the surfaces of the plates have deep recesses that separate inked regions from non-inked regions of the plates to prevent blurring of the resulting image. These deep recesses will not adequately support the planarizing liquid adjacent to the surface of a microelectronic substrate, reducing the effectiveness of the planarizing pad. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward planarizing pads for planarizing microelectronic substrates, methods for forming planarizing pads, and methods for planarizing the microelectronic substrates. In one aspect of the invention, the planarizing pad is formed by exposing a first portion of a surface of an energy-sensitive, non-sacrificial planarizing pad material to a selected energy source without exposing a second portion of the surface (adjacent to the first portion) to the selected radiation energy source. The method can further include exposing the planarizing pad material to a solvent to remove material from one of the first and second portions of the planarizing pad material at a greater rate than removing material from the other of the first and second portions. The process forms a plurality of recesses directly in the surface of the planarizing pad material, with the recesses configured to support a planarizing liquid proximate to the surface of the planarizing pad material during planarization of the microelectronic substrate. 
     The planarizing pad can have a variety of shapes and features. For example, the planarizing pad can be elongated and can extend between a supply roller and a take-up roller for use with a web-format planarizing machine. Alternatively, the planarizing pad can have a circular planform shape for use with a conventional rotary format planarizing machine. In either of these embodiments, the planarizing pad can have abrasive elements fixedly disbursed therein and/or can be used with a planarizing liquid having a suspension of abrasive particles. 
     In another aspect of the invention, the steps discussed above with respect to the radiation-sensitive planarizing pad material can be used to process a radiation-sensitive mold material into a mold. The mold can be wrapped around a roller which rotates to engage the planarizing pad material and emboss the planarizing pad material with recesses and texture elements, or the mold can have a flat shape which presses against the planarizing pad material to form recesses and texture elements in the planarizing pad material. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a partially schematic, side elevational view of a planarizing apparatus in accordance with the prior art. 
         FIGS. 2A–2E  are partially schematic side elevational views of a photopolymer composite undergoing a photo-etching process in accordance with the prior art. 
         FIGS. 3A–3D  are partially schematic side elevational views of a photopolymer composite undergoing a photo-etching process to produce a planarizing surface in accordance with an embodiment of the present invention. 
         FIG. 4  is a partially schematic, side elevational view of a planarizing pad having fixed abrasive elements in accordance with another embodiment of the invention. 
         FIG. 5  is a partially schematic, side elevational view of a rotary embossing drum for forming a planarizing surface in accordance with still another embodiment of the invention. 
         FIG. 6  is a partially schematic, side elevational view of an embossing plate for forming a planarizing surface in accordance with yet another embodiment of the invention. 
         FIG. 7  is a partially schematic, side elevational view of an apparatus having a planarizing pad in accordance with still another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure describes planarizing pads, methods for making planarizing pads, and methods for the mechanical and/or chemical-mechanical planarizing of substrate assemblies used in the fabrication of microelectronic substrates. Many specific details of certain embodiments of the invention are set forth in the following description, and in  FIGS. 3A–7 , to provide a thorough understanding of the embodiments described herein. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the invention may be practiced without several of the details described in the following description. 
       FIG. 3A  is a partially schematic, partial cross-sectional side elevational view of a portion of a photosensitive composite  150  for forming a planarizing pad in accordance with an embodiment of the invention. In one embodiment, the composite  150  includes a layer of photopolymer resist material  153  that can undergo a chemical change upon exposure to radiation at a selected wavelength. The photopolymer resist material  153  can have a forward surface  171  (facing downwardly in  FIG. 3A ) and a rear surface  172  facing opposite the forward surface  171 . A removable protective film  157  is positioned adjacent to the forward surface  171  to protect the forward surface  171  during handling. A backing layer or substrate  156  is positioned adjacent to the rear surface  172  to support the photopolymer resist material  153 . Photosensitive composites  150  of the type shown in  FIG. 3A  are commercially available from du Pont de Nemours and Co. of Wilmington, Del. under the name Cyrel®. 
     In one embodiment, a portion of the photopolymer resist material  153  adjacent to the backing layer  156  can be chemically altered or “set” to resist etching and provide an etch stop within the photopolymer resist material  153 . For example, an energy source  163  can emit selected radiation that passes through the backing layer  156  and penetrates through the rear surface  172  of the photopolymer resist material  153  to a selected pre-exposure depth indicated by etch-stop line  158 , setting the portion of the backing layer  156  between the rear surface  172  and the etch-stop line  158 . Accordingly, the backing layer  156  can include a polyester such as Mylar®, available from du Pont de Nemours and Co. or another material that is transparent to the selected radiation. In one embodiment, the pre-exposure depth can be from about 0.001 inch to about 0.008 inch and in other embodiments the pre-exposure depth can have other values. The pre-exposure depth generally depends on the overall thickness of the photopolymer resist material  153  and the dimensions of the features to be formed therein. In either embodiment, the pre-exposure step produces a pre-exposed portion  159  of the photopolymer resist material  153  that resists subsequent etching, as will be discussed in greater detail below with reference to  FIG. 3C . Alternatively, the pre-exposure process and the pre-exposed portion  159  can be eliminated and other methods can be used to halt subsequent etching within the photopolymer resist material  153 , or the subsequent etching can continue through the photopolymer resist material  153  to the backing layer  156 . 
     Once the pre-exposure operation has been completed, the composite  150  is inverted, as shown in  FIG. 3B , so that the rear surface  172  of the photopolymer resist material  153  faces downwardly and the forward surface  171  faces upwardly. The protective layer  157  ( FIG. 3A ) is removed from the forward surface  171  and a mask  160  is positioned on or adjacent to the forward surface  171 . The mask  160  includes opaque portions  161  that block the selected radiation from striking portions of the forward surface  171 , and transmissive portions  162  that allow the selected radiation to strike other portions of the forward surface  171 . In one embodiment, the transmissive portions  162  include apertures in the mask  160 . Alternatively, the transmissive portions  162  can be transparent or translucent to the selected radiation, so long as they allow at least some of the selected radiation to pass through the mask  160 . 
     In one embodiment, the opaque portions  161  and the transmissive portions  162  of the mask  160  can be evenly spaced to produce an even pattern of recesses in the planarizing surface of the resulting planarizing pad, as will be discussed in greater detail below. In one alternative embodiment the opaque portions and the transmissive portions can be concentrated in one or more regions of the composite  150 . In another alternative embodiment, the opaque portions  161  and the transmissive portions  162  can be randomly spaced to produce a corresponding random arrangement of recesses, as will be discussed in greater detail below with reference to  FIG. 4 . In any of the foregoing embodiments, the composite  150  and the mask  160  can be exposed to radiation emitted from the energy source  163  to illuminate exposed portions  154  of the photopolymer resist material  153  while unexposed portions  155  remain shielded from exposure to the radiation. Alternatively, the energy source  163  can selectively direct focused energy to the exposed portions  154  without the presence of the mask  160 . 
     In a “negative resist process” according to one embodiment, the photopolymer resist material is initially soluble in a selected solvent. The exposed portions  154  become generally insoluble (or less soluble) in the solvent after being exposed to the selected radiation, and the unexposed portions  155  remain soluble in the selected solvent. Alternatively, in a “positive resist process,” an initially insoluble photopolymer resist material  153  can be selected to undergo the opposite change upon exposure to a selected radiation, such that the exposed portions  154  become soluble (or more soluble) and the unexposed portions remain insoluble (or less soluble). In either embodiment, the energy source  163  can be selected to produce the desired change in the photopolymer resist material  153 . For example, in one embodiment, the energy source  163  can be selected to emit ultraviolet radiation, that renders the exposed portions  154  insoluble when exposed to solvents such as nonyl acetate and/or benzyl alcohol. Alternatively, the energy source  163  can emit other radiation (such as neutron beams or electron beams) to change the solubility of other radiation-sensitive materials. When the photopolymer resist material  153  has been pre-exposed (as discussed above with reference to  FIG. 3A ), the composite  150  is exposed to the selected radiation for long enough to cause the exposed portions  154  to change solubility down to the etch-stop line  158 . Where the photopolymer resist material  153  has not been pre-exposed, the composite  150  can be exposed to the selected radiation for a period of time sufficient to change the solubility of the photopolymer resist material  153  to a predetermined depth. 
     After the exposed portions  154  have changed solubility, the mask  160  is removed, as shown in  FIG. 3C . The composite  150  is then rinsed with a solvent that selectively dissolves or etches the unexposed portions  155  while leaving the exposed portions  154  at least substantially intact. As shown in  FIG. 3D , the resulting topography includes a plurality of recesses  170  separated by upwardly projecting contact elements  176  that contact a microelectronic substrate or substrate assembly  112  (hereinafter microelectronic substrate) during planarization. The composite  150  can be heat cured to strengthen and harden the contact elements  176 , or the curing process can be eliminated, depending on the strength of the photopolymer resister material. In one embodiment, the tops or engaging contact surfaces  177  of the contact elements  176  are each at approximately the same height so that the tops  177  define a generally flat plane. Alternatively, the tops  177  can be at different heights. In either embodiment, the composite  150  can form a planarizing pad  140  for use with an apparatus generally similar to that shown in  FIG. 1  to planarize the microelectronic substrate  112 . 
     In one embodiment, the recesses  170  of the planarizing pad  140  are configured to contain a planarizing liquid  144  and keep the planarizing liquid  144  in contact with the microelectronic substrate  112  as the substrate  112  is planarized in a manner generally in accordance with that discussed above with reference to  FIG. 1 . Accordingly, the depth D of the recesses  170  can range from about 0.001 inch to 0.004 inch. The thickness T 1  of the photopolymer resist material  153  can range from approximately 0.002 inch to approximately 0.010 inches. The thickness T 2  of the backing material  156  can range from about 0.001 inches to about 0.010 inch. Alternatively, the thicknesses T 1  and T 2  of the resist material  153  and the backing material  156 , and the depth D of the recesses  170 , can have other values so long as the planarizing pad  140  can effectively keep the planarizing liquid  144  in contact with the substrate  112 . In one aspect of this embodiment, the planarizing pad  140  can be relatively thin to allow the planarizing pad  140  to flex easily as it passes over the rollers shown in  FIG. 1 . Alternatively, the planarizing pad  140  can have a greater thickness, for example, when the planarizing pad  140  remains flat throughout its operation, as will be discussed in greater detail below with reference to  FIG. 7 . 
     An advantage of several embodiments of the planarizing pad  140  discussed above with reference to  FIGS. 3A–3D  is that they eliminate the need to periodically condition the pad  140  because it is more economical to discard used pads than to condition them. The planarizing pad  140  can be relatively inexpensive to fabricate compared to many conventional pads. This is unlike some conventional planarizing pads, which are expansive and must be reconditioned when they are worn, potentially increasing the time and effort required to keep the planarizing machine operating at peak efficiency. 
     An advantage of several embodiments of the planarizing pad  140 , when compared to conventional disposable planarizing pads, is that it can be manufactured using a photoresist process that forms the recesses  170  and contact elements  176  integrally in a single layer of photosensitive material, rather than requiring a sacrificial polymer layer, as was discussed above with reference to  FIGS. 2A–2E . Accordingly, embodiments of the planarizing pad  140  may be simpler and less expensive to manufacture than some conventional planarizing pads. 
     Still a further advantage of several embodiments of the planarizing pad  140 , when compared to printing plates formed with photoresist techniques, is that the recesses  170  are shallow enough to support the planarizing liquid  144  adjacent to the substrate  112 . Accordingly, the planarizing pad  140  can have recesses  170  that are unlike the recesses of some printing plates, which are deliberately made deeper than those of the planarizing pad  140  to prevent ink from filling the recesses and blurring the printed images. 
       FIG. 4  is a partially schematic, partial cross-sectional side elevational view of a planarizing pad  240  formed in accordance with another embodiment of the invention. In one aspect of this embodiment, the planarizing pad  240  can include a layer of photopolymer resist material  253  formed in general accordance with the steps outlined above with reference to  FIGS. 3A–3D , but which includes a plurality of fixed abrasive elements  273 . The fixed abrasive elements  273  can be selected from alumina, titania, ceria, silica, calcium carbonate or other substances that are effective at removing material from the microelectronic substrate  112  ( FIG. 3D ), and are also compatible with both the photopolymer resist material  253  and the processes discussed above with reference to  FIGS. 3A–3D . 
     In one embodiment, the photopolymer resist material  253  can include additives, such as chalk, to improve the uniformity of the distribution of the abrasive elements  273 . In other embodiments, the photopolymer resist material  253  can include chalk or other additives, such as carbonaceous materials, to control the hardness of the planarizing pad  240 . For example, the photopolymer resist material  253  can include a suspension of graphite particles to soften the planarizing pad  240  or an amorphous carbon material to harden the planarizing pad  240 . In one aspect of this embodiment, the planarizing pad  240  can have a hardness of from about 50 to about 80 on the Shore D hardness scale. In other embodiments, the photopolymer resist material  253  can include other substances to control specific characteristics of the abrasive elements  273  and/or the overall characteristics of the planarizing pad  240 . 
     One feature of the planarizing pad  240  shown in  FIG. 4  is that the fixed abrasive elements  273  can eliminate the need for abrasive particles in the planarizing liquid  244  disposed on the planarizing pad  240 . And advantage of this feature is that it generally provides a desired distribution of fixed abrasive elements  273  in contact with the planarized surface of the substrate  112 . This is an improvement over providing abrasive particles in a slurry because the slurry can be squeezed out from between the substrate  112  and the planarizing pad  240  such that distribution of abrasive particle contacting the substrate assembly  112  is not easily controlled. 
     Another feature of the planarizing pad  240  shown in  FIG. 4  is that it can include a backing layer  256  attached with an adhesive  274  to a support layer  275 . An advantage of this arrangement is that the support layer  275  can provide additional rigidity and support for the photopolymer resist material  253 . In one embodiment, the support layer  275  can be sized to allow the planarizing pad  240  to bend around the rollers of a web-format planarizing machine, or the support layer  275  can be relatively thick and the planarizing pad  240  can remain flat for either web-format or rotary planarizing machines (discussed in greater detail below with reference to  FIG. 7 ). Where the support layer  275  is not included, the planarizing pad  240  can rest directly on a top-panel, or platen of a planarizing machine. 
     Another feature of the planarizing pad  240  shown in  FIG. 4  is that the spacing between adjacent recesses  270  and/or the size of the recess  270  can vary across the pad  240  either uniformly or non-uniformly. In one aspect of this embodiment, the spacing between adjacent recesses  270  can be random. Alternatively, the spacing can be closer in one portion of the planarizing pad  240  than in another. In other embodiments, the recesses can have other spacing or other size arrangements. Regardless of the spacing and/or size of the recesses  270  on the planarizing pad  240 , an advantage of the mask  160  ( FIG. 3B ) used to define the spacing between the recesses  270  is that the mask  160  can accurately control the spacing between the recesses  270 . 
     Another advantage is that the same mask  160  can be used repeatedly to place the same pattern of recesses  270  on a series of planarizing pads  240 . Accordingly, worn planarizing pads can be removed and replaced with identical fresh planarizing pads, reducing or eliminating the need for adjusting the operating characteristics of the planarizing machine on which the planarizing pads to account for variations from one planarizing pad  240  to the next. 
       FIG. 5  is a side elevational view of a planarizing pad  340  formed in accordance with another embodiment of the invention. The planarizing pad  340  can include a thermoplastic or uncured thermoset material that is embossed with a pattern of recesses  370   a  and roughness elements  376   a  arranged either randomly, variably, or uniformly, as discussed above. The recesses  370   a  and the roughness elements  376   a  can be formed by a mold  380  which includes an embossing wheel  381  having an embossing surface  382  defined by a layer of photopolymer resist material  353 . Accordingly, the photopolymer resist material  353  can include recesses  370  and protrusions or texture elements  376  formed in generally the same manner as discussed above with reference to  FIGS. 3A–4 . As the embossing wheel  381  rotates about an axis  385  generally transverse to the plane of  FIG. 5 , the protrusions  376  press into the planarizing pad  340  to form the recesses  370   a  and the roughness elements  376   a . When the polishing pad  340  includes a thermoset material, the polishing pad  340  can be cured after the recesses  370   a  and roughness elements  376   a  are formed to harden the definition of these features. The polishing pad  340  can also include abrasive elements generally similar to those discussed above with reference to  FIG. 4 . 
     An advantage of the process discussed above with reference to  FIG. 5  is that a single surface formed with the photopolymer resist material  353  can generate a large number of planarizing pads  340 . A further advantage is that the embossing wheel  381  can easily generate a single elongated planarizing pad  340  for use with a web-format planarizing machine. 
       FIG. 6  is a side elevational view of a planarizing pad  440  formed in accordance with another embodiment of the invention. The planarizing pad  440  can be formed from a thermoplastic or uncured thermoset material that is embossed with a mold  480  that includes a flat embossing plate  481 . The embossing plate  481  has protrusions  476  and recesses  470  formed in a layer of photopolymer resist material  453  in a manner generally similar to that discussed above with reference to  FIGS. 3A–4 . The mold  480  can be lowered and raised as indicated by arrows D and E, respectively, to form recesses  470   a  by pressing the protrusions  476  into the planarizing pad  440 . In one embodiment, the flat plate  481  can be sized to produce a single planarizing pad  440  with one pressing cycle. Alternatively, the flat plate  481  can be repeatedly pressed into successive portions of an elongated planarizing pad, as the pad and the flat plate  481  move laterally relative to one another, to emboss the entire length of the planarizing pad  440 . 
       FIG. 7  is a partially schematic, partial cross-sectional side elevational view of a planarizing machine  510  with a generally circular platen or table  520 , a carrier assembly  530 , a planarizing pad  540  positioned on the table  520 , and a planarizing fluid  544  on the planarizing pad  540 . The planarizing machine  510  may also have an under-pad  525  attached to an upper surface  522  of the platen  520  for supporting the planarizing pad  540 . A drive assembly  526  rotates (arrow F) and/or reciprocates (arrow G) the platen  520  to move the planarizing pad  540  during planarization. 
     The carrier assembly  530  controls and protects the substrate  112  during planarization. The carrier assembly  530  typically has a substrate holder  532  with a pad  534  that holds the substrate  112  via suction. A drive assembly  536  of the carrier assembly  530  typically rotates and/or translates the substrate holder  532  (arrows H and I, respectively). Alternatively, the substrate holder  532  may include a weighted, free-floating disk (not shown) that slides over the planarizing pad  540 . 
     The planarizing pad  540  can have recesses and roughness elements formed by any of the methods discussed above with reference to  FIGS. 3A–6 . To planarize the substrate  112  with the planarizing machine  510 , the carrier assembly  530  presses the substrate  112  against a planarizing surface  542  of the planarizing pad  540  in the presence of the planarizing fluid  544 . The platen  520  and/or the substrate holder  532  then move relative to one another to translate the substrate  112  across the planarizing surface  542 . As a result, the abrasive particles and/or the chemicals in the planarizing medium remove material from the surface of the substrate  112 . 
     From the foregoing, it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. For example, the process steps discussed above with reference to  FIGS. 3A–3D  can be performed in a batch operation or in a continuous or semi-continuous operation as the polishing pad material moves from one process station to the next. Accordingly, the invention is not limited except as by the appended claims.