Abstract:
A method and an apparatus for releasably attaching a polishing pad to a support surface under the polishing pad. In one embodiment of the invention, a polishing pad has a first surface for planarizing a substrate assembly, a second surface contacting the support surface, and an interlocking element. The support surface has a retaining member configured to engage the interlocking element on the polishing pad. The interlocking element and retaining member can be any one of several configurations, including: tongue and groove, protuberance and depression, reciprocal elongated ridges, or teeth.

Description:
TECHNICAL FIELD 
     The present invention relates to methods and devices for releasably coupling a polishing pad to a support surface of a planarizing machine used in mechanical and/or chemical-mechanical planarization of microelectronic-device substrate assemblies. 
     BACKGROUND OF THE INVENTION 
     Mechanical and chemical-mechanical planarizing processes (collectively “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 is a schematic isometric view of a web-format planarizing machine  100  that has a support table  102  with a support surface  110  at a workstation defining a planarizing zone. The support surface  110  is generally a rigid panel or plate attached to the table  102  to provide a flat, solid surface to which a portion of a web-format planarizing pad  140  is supported during planarization. The planarizing machine  100  also has a plurality of rollers to guide, position, and hold the web-format pad  140  over the support surface  110 . The rollers generally include a supply roller  120 , first and second idler rollers  121   a  and  121   b , first and second guide rollers  122   a  and  122   b , and a take-up roller  123 . As explained below, a motor (not shown) drives the take-up roller  123 , and possibly the supply roller  120 , to advance the pad  140  across the support surface  110  along a travel axis T—T. The first idler roller  12  la and the first guide roller  122   a  also stretch the pad  140  over the support surface  110  to hold the pad  140  during operation. 
     The planarizing machine  100  also has a carrier assembly  130  to translate a substrate assembly  12  across the pad  140 . In one embodiment, the carrier assembly  130  has a substrate assembly holder  132  to pick up, hold and release the substrate assembly  12  at appropriate stages of the planarizing process. The carrier assembly  130  also has a support gantry  134  and a drive assembly  135  that can move along the gantry  134 . The drive assembly  135  has an actuator  136 , a drive shaft  137  coupled to the actuator  136 , and an arm  138  projecting from the drive shaft  137 . The aim  138  carries the substrate assembly holder  132  via another shaft  139 . The actuator  136  orbits the substrate assembly holder  132  about an axis B—B to move the substrate assembly  12  across the pad  140 . 
     The polishing pad  140  may be a non-abrasive polymeric web (e.g., a polyurethane sheet), or it may be a fixed abrasive polishing pad having abrasive particles fixedly dispersed in a suspension medium. During planarization of the substrate assembly  12 , a planarizing fluid  144  flows from a plurality of nozzles  145 . The planarizing fluid  144  may be a conventional CMP slurry with abrasive particles and chemicals that etch and/or oxidize the substrate assembly  12 , or the planarizing fluid  144  may be a nonabrasive planarizing( solution without abrasive particles. In most CMP applications, abrasive slurries are used on non-abrasive polishing pads, and non-abrasive planarizing solutions are used on fixed abrasive polishing pads. 
     The planarizing machine  100  incrementally moves the pad  140  across the support surface  110  either during or between planarizing cycles to change the particular portion of the polishing pad  140  in the planarizing zone. For example, the supply and take-up rollers  120  and  123  can drive the polishing pad  140  such that a point P moves incrementally across the support surface  110  to a number of intermediate locations I 1 , I 2 , etc. Alternatively, the rollers  120  and  123  may drive the polishing pad  140  such that the point P moves all the way across the support surface  110  to completely remove a used portion of the pad  140  from the planarizing zone on the support surface  110 . The rollers may also continuously drive the polishing pad at a slow rate such that the point P moves continuously across the support surface  110 . Thus, the polishing pad  140  should be free to move axially over the length of the support surface  110  along the travel axis T—T. 
     CMP processes should consistently and accurately produce a uniform, planar surface on the substrate assembly to enable circuit and device patterns to be formed with photolithography techniques. As the density of integrated circuits increases, it is often necessary to accurately focus the critical dimensions of the photo-patterns to within a tolerance of approximately 0.1 μm. Focusing photo-patterns to such small tolerances, however, is difficult when the planarized surface of the wafer is not uniformly planar. Thus, CMP processes should create a highly uniform, planar surface to be effective. 
     One processing concern associated with web-format planarizing machines is that the polishing pad  140  may move transversely to the travel axis T—T during a planarizing cycle of the substrate assembly  12 . For example, although the first idler roller  121   a  and the first guide roller  122   a  stretch the pad  140  over the support surface  110 , the orbital motion of the substrate assembly  12  and the friction between the substrate assembly  12  and the pad  140  may cause the pad  140  to move transverse to the travel axis T—T. Such transverse movement of the polishing pad  140  can produce inconsistent planarizing results because it stretches and/or damages the polishing pad  140 . The transverse movement of the polishing pad  140  may also allow the slurry to seep underneath the polishing pad  140 , which causes uneven wear of the pad  140  and contamination of the planarizing machine  200 . Moreover, if the pad wears unevenly, the topography of the pad may cause vibrations in the CMP machine that further affect the planarity of the finished surface and the consistency of the CMP process. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward methods and apparatuses for releasably securing a polishing pad to a support surface in mechanical and/or chemical-mechanical planarization of microelectronic-device substrate assemblies. In one embodiment of the invention, a polishing pad for planarizing microelectronic-device substrate assemblies has a first surface configured to engage a substrate assembly and a second surface configured to releasably engage the support surface of a planarizing machine. The second surface of the polishing pad, for example, can have an interlocking element configured to engage a corresponding retaining member on the support surface to inhibit relative movement between the polishing pad and the support surface. In a particular embodiment of the invention, the interlocking element and the retaining member are configured so that the pad can move over the support surface along a travel path or axis, but relative movement between the pad and the support surface transverse to the travel axis is at least substantially inhibited. 
     The interlocking element and the retaining member can have several embodiments. For example, the interlocking element can be an elongated tongue on the second surface of the polishing pad extending along the travel axis and the retaining member can be an elongated groove in the support surface. The interlocking element and the retaining member can alternatively be another type of a protuberance and a reciprocal depression combination, such as elongated ridges or teeth extending along the travel axis. In the above embodiments, the support surface can further include one or more apertures coupled with a fluid pump to draw together or blow apart the interlocking elements and the retaining members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic isometric view of a web-format planarizing machine with a web-format polishing pad in accordance with the prior art. 
     FIG. 2A is a schematic isometric exploded view of a web-format planarizing machine including a sub-pad and a polishing pad having elongated ridges in accordance with an embodiment of the invention. 
     FIG. 2B is a partial cross-sectional isometric view of the polishing pad and the sub-pad of FIG. 2A along line  2 B— 2 B. 
     FIG. 3A is a schematic isometric exploded view of a web-format planarizing machine including a sub-pad having a plurality of teeth and a polishing pad having a plurality of reciprocal teeth in accordance with another embodiment of the invention. 
     FIG. 3B is a partial cross-sectional isometric view of the polishing pad and the sub-pad of FIG. 3A taken along line  3 B— 3 B. 
     FIG. 4A is a schematic isometric exploded view of a web-format planarizing machine including a sub-pad having depressions and a polishing pad having reciprocal protuberances in accordance with still another embodiment of the invention. 
     FIGS. 4B and 4C are partial cross-sectional isometric views of alternative embodiments of the polishing pad and the sub-pad with depressions and reciprocal protuberances. 
     FIG. 5A is a schematic isometric exploded view of a web-format planarizing machine including a sub-pad having a groove and a polishing pad having a reciprocal tongue in accordance with yet another embodiment of the invention. 
     FIGS. 5B and 5C are partial cross-sectional isometric views of alternative embodiments of the polishing pad and the sub-pad with grooves and reciprocal tongues. 
     FIG. 6 is a schematic isometric view of a web-format planarizing machine with a support surface having guide rials in accordance with still another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed toward the methods and apparatuses for releasably engaging a polishing pad with a support surface of a planarizing machine to restrict movement of the polishing pad in mechanical and/or chemical-mechanical planarization of microelectronic-device substrate assemblies. Several embodiments of the invention are directed toward polishing pads having interlocking elements that engage reciprocal retaining members on the support surface in a manner that restricts the pad from moving transversely to a travel axis but allows the pad to move along the travel axis. Many specific details of certain embodiments of the invention are set forth in the following description and in FIGS. 2A-6 to provide a thorough understanding of such embodiments. One skilled in the air, 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. 2A is a schematic isometric view partially illustrating a web-format CMP apparatus  200  having a support surface  210  defined by an upper surface of a sub-pad  212  and a web-format polishing pad  240  in accordance with one embodiment of the invention. The planarizing machine  200  may also have a carrier assembly  230  and a plurality of rollers for selectively moving the polishing pad  240  over the support surface  210  along a travel axis T—T. The carrier assembly  230  and the rollers  220 ,  221   a ,  221   b ,  222   a ,  222   b , and  223  can be similar to those described above with reference to FIG.  1 . The support surface  210  and the polishing pad  240  of this embodiment, however, interlock with one another to allow the pad  240  to slide along the travel axis T—T, but to at least substantially inhibit the polishing pad  240  from moving transversely to the travel axis T—T during a planarizing,j cycle. For the purposes of the present disclosure, “transverse” is defined as any non-parallel movement or configuration. 
     FIG. 2B is a partial cross-sectional view illustrating the polishing pad  240  and the support surface  210  of the sub-pad  212  in greater detail. Referring to FIGS. 2A and 2B together, the polishing pad  240  of this embodiment has a body  241  with a planarizing surface  242  configured to engage the substrate assembly  12  and a backside surface  243  configured to engage the support surface  210 . The planarizing surface  242  can be a highly planar surface, or it can have grooves, wells or other surface topographies to transport or hold a planarizing solution under the substrate assembly. The backside surface  243  of the pad  240  can have at least one, and preferably a plurality, of interlocking elements  246 . In this embodiment, for example, the interlocking elements  246  are elongated ridges extending along the backside  243  in a direction at least substantially parallel to the pad travel axis T—T. The support surface  210  of sub-pad  212  can have at least one, and preferably a plurality, of retaining members  213  configured to releasably engage the interlocking elements  246 . In this embodiment, the retaining members  213  are elongated ridges extending along the support surface  210  to interlock with the interlocking elements  246 . The elongated ridges defining the interlocking elements  246  and the retaining members  213  preferably have a plurality of alternating peaks  247  and troughs  248  with substantially similar dimensions. In one embodiment, the peaks  247  have a height of approximately 10-1000 μm. The representation of the peaks  247  and troughs  248  in FIG. 2, therefore, is exaggerated for purposes of illustration. 
     The sub-pad  212  interlocks with the polishing pad  240  to control the motion of the polishing pad  240  relative to the travel axis T—T. The sub-pad  212  is preferably attached to a rigid, flat panel or plate  214 , such as a table. The sub-pad  212 , for example, can be attached to the panel  214  with an adhesive, tape or other suitable compound typically used to adhere circular polishing pads to rotary planarizing machines. The fixed sub-pad  212  at least substantially inhibits the polishing pad  240  from moving in a direction transverse to the travel axis T—T because the intermeshing of the elongated ridges  213  and the interlocking elements  246  impedes transverse movement between the sub-pad  212  and the pad  214 . The interlocking elements  246  and the retaining members  213 , however, allow the polishing pad  240  to move freely over the support surface  210  along the travel axis T—T. 
     FIG. 2A best illustrates an embodiment of planarizing the substrate assembly  12  with the planarizing apparatus  200 . During planarization of the substrate assembly  12 , the actuator  236  orbits the substrate assembly holder  232  about the axis B—B to move the substrate assembly  12  across the pad  240 . The first idler roller  221   a  and the first guide roller  222   a  stretch the polishing pad  240  over the sub-pad  212  to intermesh the interlocking elements  246  and the retaining members  213 . Thus, as the actuator  236  orbits the substrate assembly  12  across the polishing pad  240 , the interlocking elements  246  and the retaining members  213  impede the pad  240  from moving transversely to the travel axis T—T. After the substrate assembly  12  is planarized and removed from the pad  240 , the supply and take up rollers  220  and  223  slide the polishing pad  240  over the sub-pad  212  along the travel axis T—T. The interlocking elements  246  and retaining members  213  accordingly allow the pad  240  to move axially along the travel axis T—T because they extend at least substantially parallel to the travel axis T—T. 
     This embodiment of the planarizing apparatus  200  is expected to prolong the pad life and provide consistent planarizing results. Unlike existing vacuum designs or adhesives, the planarizing apparatus  200  engages the interlocking elements  246  of the polishing pad  240  with the retaining members  213  of the sub-pad  212  to allow relative movement in a first direction (e.g., along the travel axis T—T) but to inhibit relative movement transverse to the first direction. One expected result of inhibiting such transverse movement of the polishing pad  240  is to reduce wear or damage to the polishing pad  240  caused by stretching and/or twisting the pad transversely to the travel axis T—T. Additionally, by reducing such wear of the polishing pad  240 , the planarizing surface  242  is expected to wear more evenly to produce more consistent planarizing results. Another expected result of inhibiting such transverse movement of the polishing pad  240  is to reduce the volume of planarizing solution that seeps underneath the polishing pad  240 , which is expected to further reduce uneven wear of the pad and contamination of the planarizing machine  200 . Thus, the planarizing apparatus  200  is expected to prolong the pad life and to more consistently planarize substrate assemblies. 
     In another embodiment of the planarizing apparatus  200 , the polishing pad  240  can be directly supported by the table  214  without the sub-pad  212 . The top surface of the table  214 , therefore, can have at least one, and preferably a plurality, of retaining members configured to releasably engage the interlocking elements of the polishing pad  240 . In one embodiment, the retaining members are elongated ridges extending along the table  214  similar to the retaining members  213  on the sub-pad. The polishing pad  240  can thus engage the top surface of the table  214  directly such that the support surface is defined by the top surface of the table  214 . 
     FIG. 3A is a schematic isometric view partially illustrating a web-format CMP apparatus  300  having a support surface  310  defined by an upper surface of a sub-pad  312  and a web-format polishing pad  340  in accordance with another embodiment of the invention. The planarizing machine  300  may also have a carrier assembly  330  and a plurality of rollers for selectively moving the polishing pad  340  over the support surface  310  along a travel axis T—T. In this embodiment, the support surface  310  and the polishing pad  340  can interlock with one another to substantially inhibit the polishing pad  340  from moving in any direction during a planarizing cycle 
     FIG. 3B is a partial cross-sectional view illustrating the polishing pad  340  and the support surface  310  of the sub-pad  312  in greater detail. Referring to FIGS. 3A and 3B together, several aspects of the polishing pad  340  of this embodiment can be similar to the polishing pad described above with reference to FIGS. 2A and 2B. In this embodiment, polishing pad  340  has a planarizing surface  342  configured to planarize a microelectronic-device substrate, a backside  343  opposite the planarizing surface  342 , and a plurality of pyramidal interlocking elements  344  projecting from the backside  343 . The support surface  310  of the sub-pad  312  can have at least one, and preferably a plurality, of pyramidal retaining members  316  configured to releasably engage the interlocking elements  344 . The pyramidal interlocking elements  344  and retaining members  316  preferably have a plurality of alternating peaks  347  and depressions  348  with substantially similar dimensions such that the depressions of one receives the peaks of the other. In one embodiment, the pyramidal interlocking elements  344  and retaining members  316  have a height from approximately 10-1000 μm, and more particularly from 30-50 μm. The representation of the interlocking elements  344  and the retaining members  316  in FIGS. 3A and 3B is thus exaggerated for purposes of illustration. 
     The sub-pad  312  interlocks with the polishing pad  340  to control the motion of the polishing pad  340  relative to the sub-pad  312 . The sub-pad  312  is preferably attached to a rigid, flat panel or plate  314 , such as a table in a manner similar to that described above with reference to FIGS. 2A and 2B. The table  314  and the sub-pad  312  may further include a plurality of fluid apertures  352  in fluid communication with a fluid passageway  354 . The fluid apertures  352  may have a circular cross-sectional shape, comprise slots or have other shapes in other embodiments. The fluid passageway  354  is connected to a conduit  358  that is in turn coupled to a pump  356  that can draw a fluid or blow a fluid through the passageway  354 . A liquid trap may be positioned in the conduit  358  and apart from the base to separate liquid from the fluid drawn by the pump  356 . In another embodiment, the liquid trap  359  may form an integral component of the pump  356 . 
     In operation, the polishing, pad  340  is rolled up on the supply roller  320  and one end is extended over the table  314  and attached to the take-up roller  323 . The pump  356  draws a fluid against the backside  343  of the pad  340  to draw the polishing pad  340  tightly against the sub-pad  312 . The carrier assembly  330  moves relative to the polishing pad  340  and presses the substrate  12  against the planarizing surface  342  to planarize the semiconductor substrate assembly  12 . Periodically, either during the planarization of a single substrate assembly  12  or after a substrate has been planarized, the carrier assembly  330  disengages the substrate assembly  12  from the pad  340  and the pump  356  reverses the flow to blow fluid through the passageway  354 . The positive pressure in the passageway  354  disengages the interlocking elements  344  from the retaining member  316  so that the rollers  320  and  323  can advance the polishing pad  340  over the sub-pad  312 . Once the polishing pad  340  has been advanced, the pump  356  may draw the fluid against the pad  340  to reengage the interlocking elements  344  and the retaining members  316 . 
     In an alternative embodiment (not shown) the pump  356  can be replaced with a source of electrical current to apply a charge to the table  314  and attract the polishing pad  340  toward the table  314  via electrostatic forces. In one aspect of this alternative embodiment, the polishing pad  340  can include a conductive layer adjacent the table  314 , and in another aspect of this alternative embodiment the polishing pad  340  can include particles capable of receiving an induced electrostatic force. In addition to web-for-mat machines, the polishing pad  340  and sub-pad  312  can be cut in circular sheets for use on rotary planarizing machines, such as those disclosed in U.S. Pat. Nos. 5,486,131; 5,456,627; and 5,020,283, all of which are herein incorporated by reference. 
     The CMP apparatus  300  shown in FIG. 3A can securely engage the polishing pad  340  with the sub-pad  312  to prevent the pad  340  from wrinkling or folding when the semiconductor substrate assembly  12  is planarized. The CMP apparatus  300  shown in FIG. 3A also releasably attaches the polishing pad  340  to the sub-pad  312  without the need for tensioning the polishing pad  340 . Accordingly, the polishing pad  340  may be less likely to stretch or otherwise deform. 
     FIG. 4A is a schematic isometric view illustrating a web-format CMP apparatus  400  having a support surface  410  defined by an upper surface of a sub-pad  412  and a web-format polishing pad  440  in accordance with still another embodiment of the invention. The carrier assembly  430  and rollers can be similar to those described above with reference to FIG.  1 . The support surface  410  may also have a plurality of apertures (not shown) similar to those shown in FIG. 3A to draw a fluid to create a vacuum or blow the fluid to apply a positive pressure against the pad  440 . 
     FIGS. 4B and 4C are partial cross-sectional views illustrating different aspects of the polishing pad  440  and the support surface  410  of the sub-pad  412  in greater detail. The support surface  410  has a plurality of retaining members  416  defined by hemispherical depressions in the support surface  410 . The pad  440  in FIG. 4B has a flat planarizing surface  442  and a plurality of hemispherical interlocking elements  447  projecting from its backside. The planarizing surface  442  of the polishing pad  440  in FIG. 4C also has a plurality of depressions to receive the interlocking elements  447  when the pad  440  is rolled on the supply and take up rollers  420  and  423 . In operation, the interlocking elements  447  mate with the retaining members  416  to inhibit relative movement between the pad  440  and the sub-pad  412 . 
     FIG. 5A is a schematic isometric view illustrating a web-format CMP apparatus  500  having a support surface  510  defined by an upper surface of a sub-pad  512  and a web-format polishing pad  540  in accordance with yet another embodiment of the invention. The carrier assembly  530  and rollers can be similar to those described above with reference to FIG.  1 . 
     FIGS. 5B and 5C are partial cross-sectional views illustrating different aspects of the polishing pad  540  and the sub-pad  512  in greater detail. The support surface  5   10  of FIG. 5B has a plurality of retaining members  518  defined by elongated tongues extending in the direction of the travel path T—T. The polishing pad  540  of FIG. 5B has a flat planarizing surface  542  and a backside  543  with a plurality of interlocking elements  548  defined by elongated grooves. The sub-pad  512  and polishing pad  540  of FIG. 5C have an inverse tongue and groove arrangement from FIG.  5 B. In this embodiment, the polishing pad  540  has at least one interlocking element  548  that is an elongated tongue configured to fit in a groove type retaining member  518 . The planarizing surface  542  of the pad  540  shown in FIG. 5C also has at least one groove indentation  549  to receive a corresponding interlocking element  548  when the pad is rolled-up on the rollers  520  and  523 . 
     The sub-pad  512  interlocks with the polishing pad  540  to control the motion of the polishing pad  540  relative to the sub-pad  512 . The sub-pad  512  is preferably attached to a rigid, flat panel or plate  514 , such as a table in a manner similar to that described with reference to FIGS. 2A and 2B. Alternatively, in applications without a sub-pad, the table  514  has at least one retaining member  518 , such as an elongated groove or tongue, that interlocks with the interlocking element  548  to inhibit relative movement between the pad  540  and the table  514  transverse to the travel path T—T. 
     FIG. 6 is a schematic isometric view of a web-format CMP apparatus  600  having a support surface  610 , a sub-pad  612 , and a web-format polishing pad  640  similar to those described above with reference to FIG.  1 . During planarization, the supply rollers  620  and the take up rollers  623  may provide a positive tension on the polishing pad  640  in the direction of travel T—T. In this embodiment, a guide wall  650  projects upwardly from each edge of the support surface  610  and extends substantially parallel to the direction of travel T—T. The guide walls  650  generally have a height above the thickness of the polishing pad  640  and are generally spaced apart the width of the polishing pad  640 . The guide walls  650  permit the web-format polishing pad  640  to move freely in the direction of travel T—T, but inhibit the polishing pad  640  from moving transversely to the direction of travel path T—T. 
     In yet another alternate embodiment, the fluid pump components of FIG. 3A can be combined with any one of the above embodiments to engage the interlocking surfaces prior to planarization or to disengage the interlocking surfaces upon completion of the planarization cycle. In still another embodiment, the guide walls  650  of FIG. 6 can be combined with any one of the above embodiments to further restrict transverse movement of the polishing pad relative to the travel path T—T. 
     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, many embodiments of the invention can be used with rotary planarizing machines that have circular polishing pads and rotating platens. Accordingly, the invention is not limited except as by the appended claims.