Abstract:
A subpad support for use in a web format or belt format polishing apparatus for polishing one or more layers of semiconductor device structures. The subpad support includes a subpad retention element for nonadhesively securing the subpad thereto. The subpad support may also include one or more lips protruding therefrom so as to at least substantially inhibit lateral movement of the subpad relative to the subpad support. Polishing apparatus including the subpad support are also disclosed. The polishing pads of such polishing apparatus may be at least partially moved away from the subpad or subpad support so as to facilitate assembly of a subpad with the subpad support or removal of the subpad from the subpad support without damaging the polishing pad. Methods of removably securing a subpad to the subpad support, removing the subpad from the subpad support, and replacing another subpad on the subpad support, as well as polishing methods are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a divisional of application Ser. No. 09/652,878, filed Aug. 31, 2000, pending. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to subpad supports in web format and belt format polishing apparatus. Particularly, the present invention relates to subpad supports including nonadhesive subpad securing elements and to polishing apparatus including the subpad supports. The present invention also relates to assemblies including a subpad and a subpad support of the present invention, as well as to methods of assembling a subpad with, securing a subpad to, removing a subpad from, and replacing a subpad on a subpad support of the present invention.  
           [0004]    2. State of the Art  
           [0005]    Web format polishing apparatus typically include a wafer support and a polishing pad. The wafer support is typically configured to hold a semiconductor wafer, to bring the wafer into contact with the polishing pad, and to rotate the wafer while the wafer is in contact with the polishing pad so as to create friction between the wafer and the polishing pad and, thereby, effect polishing of one or more layers on the wafer. As used herein, the term “polishing” encompasses removal of material from a semiconductor wafer. “Polishing,” as used herein, need not achieve a certain surface finish or planarity. A subpad, located on the opposite side of the polishing pad from the wafer support, is configured to prevent the formation of defects on a wafer secured to the wafer support during polishing thereof, as well as to cushion the polishing pad and wafer being polished so as to prevent damage to the wafer during polishing. The subpad is held in place by a subpad support and, conventionally, has been secured to the subpad supports by way of an adhesive material.  
           [0006]    Fresh portions of a web format, film-type polishing pad are supplied by a supply reel of the web format polishing apparatus, while used portions of the web format polishing pad are taken up on a take-up reel of the apparatus. Typically, the positions of supply reels and take-up reels on conventional web format polishing apparatus are fixed relative to the remainder of these apparatus.  
           [0007]    As a subpad wears, it must be replaced. Typically, in order to remove a subpad from a web format polishing apparatus, the web format polishing pad must either be cut or slack formed in the polishing pad by, for example, loosening the web format pad from the supply reel of the polishing apparatus without winding the pad around the take-up reel. Creating slack in a web format polishing pad facilitates pulling of the polishing pad away from the subpad. When a web format polishing pad is cut or given slack, it is common that a portion of the polishing pad is damaged and, thus, that portion of the polishing pad is wasted. In addition, as the subpad is typically secured to the subpad support with an adhesive material, removal of the subpad from the subpad support is often very difficult since the subpad may rip or need to be scraped from the subpad support.  
           [0008]    Belt format polishing apparatus are very similar to web format polishing apparatus, with the major exception being that the polishing pad is in the format of a continuous belt that may be recycled, rather than a web that is supplied from a supply reel and, after use, taken away on a take-up reel. In order to gain access to a subpad of a belt format polishing apparatus, the belt format polishing pad is removed from the polishing apparatus, which is time consuming and may result in damage to the pad, or the pad may be stretched, which may also damage the pad. Damage to a belt format polishing pad to remove and replace a subpad is, however, even more costly than damage to a web format polishing pad because a damaged belt format polishing pad must be completely replaced.  
           [0009]    The inventor is not aware of a subpad support to which a subpad may be nonadhesively secured and from which a subpad may be readily removed. Moreover, the inventor is not aware of a web format or belt format polishing apparatus configured to facilitate subpad removal and replacement without a significant potential for damaging the polishing pad.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    The present invention includes a subpad support with a retention element for removably, nonadhesively securing a subpad thereto, as well as web format and belt format polishing apparatus including the subpad support.  
           [0011]    The subpad support of the present invention includes a subpad supporting surface and a subpad retention element. The subpad supporting surface is configured to receive a backing of a subpad. The subpad retention element is configured to nonadhesively secure a subpad to the subpad support. The subpad retention element may be configured to at least partially engage a periphery of a subpad, mechanically engage a backing of a subpad, apply a negative pressure to a backing of a subpad through the subpad support, or otherwise nonadhesively secure a subpad to the subpad support.  
           [0012]    The subpad support may also include one or more lips, columns, or other lateral confinement structures protruding from the supporting surface thereof and that are configured and located so as to at least partially prevent lateral movement of a subpad relative to the subpad support to which the subpad is secured.  
           [0013]    To facilitate the releasable securing of a subpad to the subpad support, the subpad may include a substantially rigid structure on the backing thereof. The substantially rigid structure may be secured to the backing of the subpad or formed by a denser region of the material of the subpad. If the substantially rigid structure is secured to the backing of the subpad, a material such as a polymer, a metal, a glass, or a ceramic may be used as the substantially rigid structure.  
           [0014]    Polishing apparatus including the subpad of the present invention are also within the scope of the present invention. A polishing apparatus incorporating teachings of the present invention may include a component that at least partially moves the polishing pad of the apparatus away from the subpad support thereof, as well as a subpad secured to the subpad support. In a web format polishing apparatus, such a component may include, by way of example only and not to limit the scope of the present invention, a releasable latch that secures one or both of the supply reel and the take-up reel to the remainder of the polishing apparatus. In addition, such an exemplary polishing apparatus may also include a member that effects the controlled movement of one or both of the supply and take-up reels and, thus, the polishing pad away from the remainder of the polishing apparatus. Exemplary members include, but are not limited to, one or more hydraulic pistons, gear drive mechanisms, and screw drive mechanisms.  
           [0015]    Methods of assembling and securing a subpad to the subpad support, removing a subpad from the subpad support, and replacing a subpad on the subpad support are also within the scope of the present invention, as are methods of at least partially moving a polishing pad away from a subpad support so as to facilitate such assembly, securing, removal, and replacing.  
           [0016]    Other features and advantages of the present invention will become apparent to those of skill in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a perspective assembly view illustrating an exemplary embodiment of a subpad support incorporating teachings of the present invention and a subpad configured to be secured to the subpad support by way of complementary threads on the subpad and the subpad support;  
         [0018]    [0018]FIG. 2 is a perspective view of another exemplary embodiment of an assembly of a subpad support that includes a clamping member configured to engage at least a portion of a periphery of a subpad;  
         [0019]    [0019]FIG. 3 is a cross-sectional representation of an embodiment of a subpad support-subpad assembly wherein the subpad support includes clamping members configured to engage recessed portions of a complementary subpad;  
         [0020]    [0020]FIG. 4 is a cross-sectional representation of yet another exemplary embodiment of an assembly including a subpad support and a subpad of the present invention, wherein the subpad support is configured to apply a relatively negative pressure to the backside of the subpad to secure the subpad thereto;  
         [0021]    [0021]FIG. 5 is a partial perspective view of an embodiment of a subpad support configured to slidingly engage a complementarily configured subpad;  
         [0022]    [0022]FIG. 6 is a partial top view of an embodiment of subpad support with recesses and slots configured to receive tabs protruding from the periphery of a complementarily configured subpad;  
         [0023]    [0023]FIGS. 7A and 7B illustrate still another embodiment of subpad support and subpad incorporating teachings of the present invention, wherein the subpad support includes keyhole-shaped recesses configured to receive headed studs protruding from the backing of the subpad;  
         [0024]    [0024]FIGS. 8 and 8A are schematic representations of a belt format polishing apparatus incorporating teachings of the present invention, depicting at least partial movement of the polishing pad thereof away from the subpad support thereof; and  
         [0025]    [0025]FIGS. 9 and 9A are schematic representations of a belt format polishing apparatus incorporating teachings of the present invention, depicting movement of the polishing pad thereof away from the subpad support thereof. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    Referring to FIG. 1, a first exemplary embodiment of a subpad support  10  incorporating teachings of the present invention is illustrated. Subpad support  10  includes a supporting surface  12  and a retention element  14 . Supporting surface  12  is configured to engage a backing  22  of a subpad  20 . Retention element  14  is configured to secure subpad  20  to subpad support  10 . Subpad support  10  may also include one or more lips  16  protruding therefrom and positioned so as to facilitate the alignment of subpad  20  with subpad support  10  during assembly thereof or to at least partially prevent lateral movement of subpad  20  relative to supporting surface  12  during use.  
         [0027]    Retention element  14 , as illustrated, is configured to mechanically engage a corresponding, complementary structure of a known type, such as the illustrated threaded locking element  24 , on backing  22  of subpad  20 . Upon interconnecting retention element  14  and locking element  24  and rotating locking element  24  relative to retention element  14 , retention element  14  and locking element  24  interlock so as to secure subpad  20  to subpad support  10 .  
         [0028]    As illustrated, locking element  24  is secured to a backing  22  of subpad  20  by known means, such as with a suitable adhesive. Alternatively, locking element  24  may be integral with backing  22 . Backing  22  may be formed from a relatively denser region of the same material as the remainder of subpad  20 , which may be formed from a material such as closed-cell polyurethane foam, and may be integral therewith, or may comprise a separate element secured to the remainder, or contact surface  23 , of subpad  20 . Alternatively, backing  22  may be formed from another polymer (e.g., polycarbonate), a metal, a ceramic, or any other suitable material, different from the material of contact surface  23 , which cushions a wafer during polishing thereof. A backing  22  that is separate from the remainder of subpad  20  may be secured thereto as known in the art, such as by use of adhesives or by thermally bonding contact surface  23  of subpad  20  to backing  22  thereof.  
         [0029]    Turning now to FIG. 2, another embodiment of a subpad support  10 ′ according to the present invention is illustrated. Subpad support  10 ′ includes a supporting surface  12 ′ and a retention element  14 ′. Again, supporting surface  12 ′ is configured to engage a backing  22 ′ of a subpad  20 ′ to be assembled with subpad support  10 ′. In addition, retention element  14 ′ is configured to mechanically secure a subpad  20 ′ to subpad support  10 ′.  
         [0030]    Retention element  14 ′ of subpad support  10 ′ includes a clamping member  15 ′ that is configured to be positioned around the periphery  21 ′ of at least a rigid backing  22 ′ of subpad  20 ′ upon assembly of subpad  20 ′ with subpad support  10 ′ and to be biased against periphery  21 ′ so as to secure backing  22 ′ against supporting surface  12 ′ while substantially maintaining the planarity of contact surface  23 ′ of subpad  20 ′ and, thus, the planarity of an area of a polishing pad to be supported by subpad  20 ′. In addition, clamping element  15 ′ at least partially prevents lateral movement of subpad  20 ′ relative to supporting surface  12 ′.  
         [0031]    Again, subpad  20 ′ includes a cushioning contact surface  23 ′ and a substantially rigid backing  22 ′. Backing  22 ′ may be formed from a dense region of the same material as contact surface  23 ′ or from another material, such as another polymer, a metal, a ceramic, or another suitable material. If backing  22 ′ is formed from the same material as contact surface  23 ′, backing  22 ′ may be integral with contact surface  23 ′ or a separate element that is secured to contact surface  23 ′. Of course, if another material is used to form backing  22 ′, backing  22 ′ is secured to contact surface  23 ′. Backing  22 ′ and contact surface  23 ′ of subpad  20 ′ may be secured to one another by known means, such as by use of a suitable adhesive material or by thermally bonding backing  22 ′ and contact surface  23 ′ to one another.  
         [0032]    Another embodiment of subpad support  10 ″ is shown in FIG. 3. Subpad support  10 ″ includes a supporting surface  12 ″ that is configured to engage a backing  22 ″ of a subpad  20 ″. Subpad support  10 ″ also includes retention elements  14 ″ that are configured to clamp onto corresponding receptacles  26 ″ recessed in periphery  21 ″ of subpad  20 ″. Each receptacle  26 ″, along with backing  22 ″, forms a lip  27 ″, which a corresponding retention element  14 ″ engages upon being disposed in a clamping position. Upon engaging lips  27 ″ with retention elements  14 ″, backing  22 ″ of subpad  20 ″ is held against supporting surface  12 ″ of subpad support  10 ″.  
         [0033]    [0033]FIG. 4 illustrates yet another embodiment of a subpad support  10 ′″ incorporating teachings of the prevent intention. As the previously described subpad support embodiments, subpad support  10 ′″ includes a supporting surface  12 ′″ and a retention element  14 ′″. Subpad support  10 ′″ may also include one or more columns  16 ′″, lips, or other structures protruding from supporting surface  12 ′″. Columns  16 ′″ are preferably configured so as to laterally surround a periphery  21 ′″ of subpad  20 ′″ upon assembly thereof with subpad support  10 ′″. Columns  16 ′″ are configured to align a subpad  20 ′″ with subpad support  10 ′″, to substantially laterally surround a subpad  20 ′″ assembled with subpad support  10 ′″, or to at least substantially inhibit subpad  20 ′″ from moving laterally relative to supporting surface  12 ′″.  
         [0034]    Supporting surface  12 ′″ is configured to engage a backing  22 ′″ of a subpad  20 ′″ upon assembly of subpad  20 ′″ with subpad support  10 ′″.  
         [0035]    Retention element  14 ′″ employs a negative pressure to secure a subpad  20 ′″ to subpad support  10 ′″. Retention element  14 ′″ includes one or more apertures  30  formed through subpad support  10 ′″ from supporting surface  12 ′″ to an opposite surface  18 ′″. Apertures  30  communicate with a negative pressure, or vacuum, source  34  by way of a negative pressure conduit  32  between apertures  30  and negative pressure source  34 . As illustrated in FIG. 4, retention element  14 ′″ also includes a chamber  35  formed within subpad support  10 ′″ and communicating with each aperture  30 . In turn, chamber  35  communicates with conduit  32  by way of a connection port  37  on subpad support  10 ′″. Alternatively, each aperture  30  of a retention element  14 ′″ incorporating teachings of the present invention may communicate with negative pressure source  34  by way of separate conduits  32 . In any event, retention element  14 ′″ secures a subpad  20 ′″ to supporting surface  12 ′″ of subpad support  10 ′″ by applying a negative pressure to backing  22 ′″ of subpad  20 ′″ through apertures  30  formed in subpad support  10 ′″.  
         [0036]    With reference to FIG. 5, a subpad support  110  configured to receive a rectangular subpad  120  is illustrated. Subpad support  110  includes a recessed retention element  114  that is continuous with at least one end of subpad support  110 . Retention element  114  includes elongated retention slots  115  at opposite sides thereof. Retention slots  115  are configured to engage corresponding, opposite ends of a complementarily configured subpad  120  upon sliding subpad  120  in the direction of arrow A to position backing  122  of subpad  120  in substantial contact with supporting surface  112  of subpad support  110  and to effect engagement of subpad  120  by retention element  114 . Accordingly, retention slots  115  may extend laterally beneath a supporting surface  112  of subpad support  110  so as to engage thin or tapered edges  125  of subpad  120 .  
         [0037]    As shown in FIG. 6, a subpad support  110 ′ incorporating teachings of the present invention may include a subpad receptacle  115 ′ formed in a supporting surface  112 ′ of subpad support  110 ′ and configured to receive at least a backing (not shown) of a complementarily configured subpad  120 ′. In the illustrated embodiment of subpad support  110 ′, retention elements  114 ′ are disposed around the periphery  116 ′ of receptacle  115 ′ and include recesses  114   a ′ and slots  114   b ′ that are continuous with receptacle  115 ′. Recesses  114   a ′ are formed in supporting surface  112 ′ and, upon introduction of the backing of subpad  120 ′ into receptacle  115 ′, are configured to receive tabs  128 ′ that protrude laterally from periphery  121 ′ of subpad  120 ′, in a plane substantially parallel to the plane of subpad  120 ′, and are located proximate the backing of subpad  120 ′. Retention elements  114 ′ also include slots  114   b ′ that are continuous with recesses  114   a ′ and that underlie supporting surface  112 ′. Upon sliding of subpad  120 ′ in the direction of arrow B relative to subpad support  110 ′, retention tabs  128 ′ are positioned within slots  114   b ′ and subpad  120 ′ is engaged by subpad support  110 ′.  
         [0038]    Another embodiment of subpad support  110 ″ and complementary subpad  120 ″ incorporating teachings of the present invention is illustrated in FIGS. 7A and 7B. Subpad support  110 ″ includes a supporting surface  112 ″ with a series of keyhole-shaped retention elements  114 ″ formed therein. Retention elements  114 ″ include an enlarged end  114   a ″ and a narrower, elongated slot  114   b ″ formed through and continuous with supporting surface  112 ″, as well as a receptacle  114   c ″ underlying supporting surface  112 ″, enlarged end  114   a ″, and elongated slot  114   b ″. Enlarged end  114   a ″ of each retention element  114 ″ is configured to receive a head  128   a ″ of a corresponding retention stud  128 ″ that protrudes from a backing  122 ″ of subpad  120 ″. Slot  114   b ″ is narrower than end  114   a ″ and is configured to receive a neck  128   b ″ of retention stud  128 ″ as head  128   a ″ is positioned within the portion of receptacle  114   c ″ that underlies slot  114   b ″. As shown in FIGS. 7A and 7B, retention elements  114 ″, including slot  114   b ″ and receptacle  114   c ″ thereof, may be slightly curved so as to facilitate engagement of a subpad  120 ″ by subpad support  110 ″ upon slight rotation of subpad  120 ″ in the direction of arrow C relative to subpad support  110 ″. Alternatively, the slot and receptacle of a retention element  114 ″ may be angled so as to facilitate the retention of a complementary retention stud  128 ″ therein.  
         [0039]    Referring now to FIGS. 8, 8A,  9 , and  9 A, subpad support  10  may be included in a web format polishing apparatus  40 , illustrated in FIGS. 8 and 8A, or in a belt-type polishing apparatus  40 ′, shown in FIGS. 9 and 9A.  
         [0040]    As shown in FIG. 8, subpad support  10  of polishing apparatus  40  is positioned adjacent a web format polishing pad, which is referred to herein and known in the art as a “web”  42 . Polishing apparatus  40  also includes a supply reel  44  from which fresh portions of web  42  are supplied, as well as a take-up reel  46 , which receives previously used portions of web  42 . In use of polishing apparatus  40 , a semiconductor device structure  1  is brought into frictional contact with web  42 , on an opposite side thereof from subpad support  10 . As semiconductor device structure  1  is polished at least in part by web  42 , the portion of web  42  that is being used to polish semiconductor device structure  1  is supported from beneath by a subpad  20  assembled with subpad support  10 .  
         [0041]    Web  42  and subpad  20  of polishing apparatus  40  are positioned in close proximity to one another. Polishing apparatus  40  includes a polishing pad movement element  50 , which is also referred to herein as a subpad access element, to effect the movement of web  42  at least partially away from subpad  20  so as to avoid physical contact of an operator with web  42  while facilitating access to a worn or damaged subpad  20 . As illustrated in FIGS. 8 and 8A, polishing pad movement element  50  is associated with at least one of supply reel  44  and take-up reel  46  of polishing apparatus  40 . Polishing pad movement element  50  preferably effects the movement of web  42  away from subpad support  10  in a controlled manner and at a controlled rate to minimize stress on web  42 . By way of example, and not to limit the scope of the present invention, known apparatus that may be used as polishing pad movement element  50  include hydraulic pistons, screw drive motors, gear drive motors, and the like. Polishing apparatus  40  may also include a latch  52  or other known releasable locking element that is configured to prevent movement of web  42  away from subpad  20  and subpad support  10  when such movement is not desired. In addition, if polishing pad movement element  50  moves one end  42   a  of web  42  while the other end  42   b  of web  42  remains substantially stationary, end  42   b  may be pivotally connected to apparatus  40 , such as by a pivot pin  54  that connects one conveyor support  48  to a fixed structure of apparatus  40  or otherwise, as known in the art (see FIGS. 9 and 9A).  
         [0042]    Referring now to FIGS. 9 and 9A, polishing apparatus  40 ′ includes a belt format polishing pad, which is referred to herein and known in the art as a “belt”  42 ′. Belt  42 ′ may be continually moved around conveyor supports  48  to supply fresh or newly conditioned portions of belt  42 ′ for use in polishing a semiconductor device structure  1 . As semiconductor device structure  1  is brought into frictional contact with belt  42 ′ to effect polishing of semiconductor device structure  1 , the portion of belt  42 ′ that is being used to polish semiconductor device structure  1  is supported from beneath by a subpad  20  assembled with subpad support  10 .  
         [0043]    As shown in FIG. 9, belt  42 ′ and subpad  20  are positioned very closely to one another. In order to avoid physical contact by an operator with belt  42 ′ to gain access to a worn or damaged subpad  20  to remove and replace the same on subpad support  10 , polishing apparatus  40 ′ is supplied with a polishing pad movement element  50 ′ that effects the movement of belt  42 ′ at least partially away from subpad  20 . As illustrated in FIGS. 9 and 9A, polishing pad movement element  50 ′ is associated with at least one conveyor support  48  of polishing apparatus  40 ′. Polishing pad movement element  50 ′ preferably effects the movement of belt  42 ′ away from subpad support  10  in a controlled manner and at a controlled rate. Examples of known apparatus that are useful as polishing pad movement element  50 ′ include hydraulic cylinders, pneumatic cylinders, screw drive motors, gear drive motors, and the like. Polishing apparatus  40 ′ may also include a latch  52 ′ configured to prevent movement of belt  42 ′ away from subpad  20  and subpad support  10  when such movement is not desired. In addition, if polishing pad movement element  50 ′ moves one end  42   a ′ of belt  42 ′ while the other end  42   b ′ of belt  42 ′ remains substantially stationary, end  42   b ′ may be pivotally connected to apparatus  40 ′, such as by a pivot pin  54 ′ that connects one conveyor support  48  to a fixed structure of apparatus  40 ′ or otherwise, as known in the art.  
         [0044]    An example of the manner in which a subpad  20  is removed from subpad support  10  of polishing apparatus  40 ′ and replaced on subpad support  10  is described with continued reference to FIGS. 9 and 9A. Latch  52 ′ of polishing apparatus  40 ′ is positioned so as to facilitate the movement end  42   a ′ of belt  42 ′ while end  42   b ′ of belt  42 ′ pivots around pivot pin  54 ′, thereby at least partially moving belt  42 ′ away from subpad  20  and subpad support  10  so as to facilitate access to subpad  20 . Belt  42 ′ is then at least partially moved away from subpad  20  and subpad support  10  with the assistance of or by way of polishing pad movement element  50 ′. Of course, apparatus  40 ′ could be configured such that both ends  42   a ′,  42   b ′ of belt  42 ′ may be moved so as to effect movement of belt  42 ′ away from subpad support  10 . Next, subpad  20  is released by retention element  14  (see, e.g., FIGS.  1 - 3 ) and disassembled from subpad support  10 . Another subpad  20  may be assembled with subpad support  10  and secured thereto by retention element  14 . Belt  42 ′ may then be repositioned adjacent subpad  20  and subpad support  10  with the assistance or by way of polishing pad movement element  50 ′. Latch  52 ′ may be repositioned so as to secure belt  42 ′ in place.  
         [0045]    Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the present invention, but merely as providing illustrations of some of the presently preferred embodiments. Similarly, other embodiments of the invention may be devised which do not depart from the spirit or scope of the present invention. Features from different embodiments may be employed in combination. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions and modifications to the invention as disclosed herein which fall within the meaning and scope of the claims are to be embraced thereby.