Abstract:
The present invention generally provides a polishing article that is easy to clean, reduces debris and by product accumulation and reduces amount of polishing solution needed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention generally relate to a processing apparatus for planarizing or polishing a substrate. More particularly, the invention relates to polishing pad design for planarizing or polishing a semiconductor substrate by electrochemical mechanical planarization. 
         [0003]    2. Description of the Related Art 
         [0004]    In the fabrication of integrated circuits and other electronic devices on substrates, multiple layers of conductive, semiconductive, and dielectric materials are deposited on or removed from a substrate, such as a semi conductor substrate. As layers of materials are sequentially deposited and removed, the substrate may become non-planar and require planarization, in which previously deposited material is removed from the substrate to form a generally even, planar or level surface. The process is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage and scratches. The planarization process is also useful in forming features on the substrate by removing excess deposited material used to fill the features and to provide an even or level surface for subsequent deposition and processing. 
         [0005]    Electrochemical Mechanical Planarization (ECMP) is one exemplary process which is used to remove materials from the substrate. ECMP typically uses a pad having conductive properties and combines physical abrasion with electrochemical activity that enhances the removal of materials. The pad is attached to an apparatus having a rotating platen assembly that is adapted to couple the pad to a power source. The apparatus also has a substrate carrier, such as a polishing head, that is mounted on a carrier assembly above the pad that holds a substrate. The polishing head places the substrate in contact with the pad and is adapted to provide downward pressure, controllably urging the substrate against the pad. The pad is moved relative to the substrate by an external driving force and the polishing head typically moves relative to the moving pad. A chemical composition, such as an electrolyte, is typically provided to the surface of the pad which enhances electrochemical activity between the pad and the substrate. The ECMP apparatus may affect abrasive and/or polishing activity from frictional movement while the electrolyte combined with the conductive properties of the pad selectively removes material from the substrate. 
         [0006]    Although ECMP has produced good results in recent years, there is an ongoing effort to develop pads that improve polishing qualities, require less conditioning, and consume less polishing solution. For example, a conductive polishing pad used in an ECMP process generally includes an anode and a cathode (or counter electrode) separated by an insulating layer and porous foam pad. The foam pad provides mechanical cushion for global flexibility. The insulating layer and porous foam pad are exposed to polishing solution and tend to trap debris and byproducts during polishing. The debris and byproducts may scratch the substrate surface if not removed. Generally, renewing the polishing solution and rinsing the polishing pad may reduce the debris and byproducts. However, the foam pad makes it difficult to rinse the polishing pad and adds consumption of polishing solution. 
         [0007]    Therefore, there exists a need in the art for a processing article or pad that is easy to clean and reduces amount of polishing solution used. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention generally provides a polishing article that is easy to clean, reduces debris and byproduct accumulation and reduces amount of polishing solution needed. 
         [0009]    One embodiment of the present invention provides a pad assembly for processing a substrate comprising a first conductive layer having an upper surface adapted to contact the substrate, a second conductive layer disposed below the first conductive layer with an insulative layer therebetween, and a compressive layer disposed below the second conductive layer opposite the first conductive layer, wherein a plurality of recesses are formed above the second conductive layer. 
         [0010]    Another embodiment of the present invention provides a pad assembly for processing a substrate comprising a first electrode, a compressive layer disposed on one side of the first electrode, and a plurality of discrete members coupled to the first electrode opposite the compressive layer, wherein the plurality of discrete members and the first electrode define a plurality of recesses configured to retain a processing solution therein, each of the plurality of discrete members comprises a conductive layer adapted to contact the substrate and an insulative layer disposed between the first electrode and the conductive layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0012]      FIG. 1  schematically illustrates a sectional side view of an exemplary ECMP station. 
           [0013]      FIG. 2A  schematically illustrates a top view of a pad assembly in accordance with one embodiment of the present invention. 
           [0014]      FIG. 2B  schematically illustrates an enlarged portion of a processing surface of the pad assembly shown in  FIG. 2A . 
           [0015]      FIG. 3  schematically illustrates a sectional side view of a portion of a polishing assembly in accordance with one embodiment of the present invention. 
           [0016]      FIG. 4  schematically illustrates a sectional side view of a portion of a polishing assembly in accordance with another embodiment of the present invention. 
       
    
    
       [0017]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. 
       DETAILED DESCRIPTION 
       [0018]    The words and phrases used in the present invention should be given their ordinary and customary meaning in the art by one skilled in the art unless otherwise further defined. The embodiments described herein may relate to removing material from a substrate, but may be equally effective for electroplating a substrate by adjusting the polarity of an electrical source. Common reference numerals may be used in the Figures, where possible, to denote similar elements depicted in the Figures. 
         [0019]      FIG. 1  schematically illustrates a sectional side view of an exemplary ECMP station  102 . The ECMP station  102  comprises a carrier head assembly  152  positioned over a platen assembly  230 . The carrier head assembly  152  generally comprises a drive system  202  coupled to a carrier head  186 . The drive system  202  may be coupled to a controller that provides a signal to the drive system  202  for controlling the rotational speed and direction of the carrier head  186 . 
         [0020]    A processing pad assembly  222  is disposed on the platen assembly  230 . The processing pad assembly  222  is configured to receive an electrical bias to perform a plating process and/or an electrochemical mechanical polishing/planarizing process. 
         [0021]    The drive system  202  generally provides at least a rotational motion to the carrier head  186  and additionally may be actuated toward the ECMP station  102  such that a device side  115  of the substrate  114  retained in the carrier head  186 , may be disposed against a processing surface  125  of the pad assembly  222  during processing. 
         [0022]    Typically, the substrate  114  and the processing pad assembly  222  are rotated relatively to one another in an ECMP process to remove material from the device side  115  of the substrate  114 . Depending on process parameters, the carrier head  186  is rotated at a rotational speed greater than, less than, or equal to, the rotational speed of the platen assembly  230 . The carrier head assembly  152  is also capable of remaining fixed and may move in a path indicated by arrow  107  during processing. The carrier head assembly  152  may also provide an orbital or a sweeping motion across the processing surface  125  during processing. 
         [0023]    In one embodiment, the processing pad assembly  222  may be adapted to releasably couple to an upper surface  260  of the platen assembly  230 . The pad assembly  222  may be bound to the upper surface  260  by the use of pressure and/or temperature sensitive adhesives, allowing replacement of the pad assembly  222  by peeling the pad assembly from the upper surface  260  and applying fresh adhesive prior to placement of a new pad assembly  222 . In another embodiment, the upper surface  260  of the platen assembly  230 , having the processing pad assembly  222  coupled thereto, may be adapted to releasably couple to the platen assembly  230  via fasteners, such as screws. 
         [0024]    The platen assembly  230  is typically rotationally disposed on a base  108  and is typically supported above the base  108  by a bearing  238  so that the platen assembly  230  may be rotated relative to the base  108 . The platen assembly  230  may be fabricated from a rigid material, such as a metal or rigid plastic, and in one embodiment the platen assembly  230  has an upper surface  260  that is fabricated from or coated with a dielectric material, such as CPVC. The platen assembly  230  may have a circular, rectangular or other plane form and the upper surface  260  may resemble that plane form. 
         [0025]    An electrolyte  204  may be provided from the source  248 , through appropriate plumbing and controls, such as a conduit  241 , to a nozzle  255  above the processing pad assembly  222  of the ECMP station  102 . Optionally, an enclosure  206  may be defined in the platen assembly  230  for containing an electrolyte and facilitating ingress and egress of the electrolyte to the pad assembly  222 . 
         [0026]    In the embodiment shown in  FIG. 1 , the electrolyte  204  is provided from the nozzle  255 . The electrolyte  204  may form a bath that is bounded by a platen lip  258  adapted to contain a suitable processing level of the electrolyte  204  while rotating. Alternatively, the electrolyte  204  may be provided by the nozzle  255  continuously or at intervals to maintain a suitable level of electrolyte in the processing pad assembly  222 . After the electrolyte  204  has reached its processing capacity and is ready for replacement, the platen assembly  230  may be rotated at a higher rotational speed and the spent electrolyte  204  is released by the action of centrifugal force over the platen lip  258 . In another embodiment, the platen assembly  230  is rotated at a higher rotational speed the spent electrolyte is released through perforations in the platen lip  258  that may be opened and closed by an operator or controlled by rotational speed. Alternatively or additionally, the spent electrolyte may be released through at least one perforation performing as a drain formed through various layers of the pad assembly  222  and the platen assembly  230 . 
         [0027]    The pad assembly  222  comprises a first conductive layer  211 , a second conductive layer  212 , an insulative layer  214  disposed between the first conductive layer  211  and the second conductive layer  212 , and a compressive layer  216 . In one embodiment, the pad assembly  222  may comprise a pad base  210  on which the rest of the layers are stacked. 
         [0028]    In one embodiment, the first conductive layer  211  and the insulative layer  214  may form a plurality of posts or discrete members  205  extending from the second conductive layer  212 . 
         [0029]    The discrete members  205  may include any geometrical shape, such as ovals, rectangles, triangles, hexagons, octagons, or combinations thereof. A processing surface  125  is generally defined by an upper portion of each of the plurality of discrete members  205 , and the plurality of apertures  209 . The plurality of apertures  209  are generally defined by the open areas between the plurality of discrete members  205 . 
         [0030]    Each of the plurality of apertures  209  defines a functional cell  207  which is configured to receive an electrolyte. Each of the functional cells  207  are adapted to perform as an electrochemical cell when the electrolyte  204  is provided to the pad assembly  222 , and a differential electrical bias is applied to the first conductive layer  211  and the second conductive layer  212 . The second conductive layer  212  may have a continuous body, for example a whole disk, preventing the electrolyte from contacting the compressive layer  216 . 
         [0031]    In one embodiment, the plurality of apertures  209 , define an open area between about 10 percent to about 90 percent, for example, between about 20 percent to about 70 percent. 
         [0032]    The compressive layer  216  may be made of a soft material that is configured to provide compressibility to the pad assembly  222 . 
         [0033]      FIG. 2A  schematically illustrates a top view of the pad assembly  222  The pad assembly  222  is exemplarily shown here having a circular processing surface  125 . The processing surface  125  includes the plurality of discrete members  205  adjacent the plurality of apertures  209 . Also shown is a first connector  264  coupled to the first conductive layer  211  and a second connector  262  coupled to the second conductive layer  212 . The first and second connectors  264 ,  262  include a hole  261 ,  263  respectively, for coupling to a mating electrical connection on the platen assembly  230  and may also facilitate coupling of the pad assembly  222  to the platen assembly  230 . 
         [0034]      FIG. 2B  schematically illustrates an enlarged portion of the processing surface  125  of the pad assembly  222  shown in  FIG. 2A . The plurality of apertures  209  are interspersed within the plurality of discrete members  205 . Each of the plurality of apertures  209  are surrounded by a plurality of channels  252 . In one embodiment, the plurality of channels  252  may be formed in the first conductive layer  211  by such methods as embossing or compression molding. 
         [0035]      FIG. 3  schematically illustrates a sectional side view of a portion of a pad assembly  322  in accordance with one embodiment of the present invention. 
         [0036]    The pad assembly  322  comprises a first conductive layer  311 , a second conductive layer  312 , an insulative layer  314  disposed between the first conductive layer  311  and the second conductive layer  312 . The insulative layer  314  is configured to electrically isolate the first conductive layer  311  from the second conductive layer  312 . The pad assembly  322  further comprises a compressive layer  316  disposed on one side of the second conductive layer  312  opposing the insulative layer  314 . The pad assembly  322  further comprises a pad base  310  on which the rest of the layers are stacked. 
         [0037]    In one embodiment, the first conductive layer  311  and the insulative layer  314  may form a plurality of discrete members  305  extending from the second conductive layer  312 . The plurality of discrete members  305  may include any geometrical shape, such as ovals, rectangles, triangles, hexagons, octagons, or combinations thereof. 
         [0038]    A plurality of apertures  309  are formed between the plurality of discrete members  305 . The plurality of apertures  309  are generally defined by the open areas between the plurality of discrete members  305 . The plurality of apertures  309  are connected to one another and are configured to retain an electrolyte therein. A processing surface  325  is generally defined by an upper portion of each of the discrete members  305 . 
         [0039]    The first conductive layer  311  and second conductive layer  312  may be connected to a power source  320  during processing. The electrolyte, when retained in the plurality of apertures  309 , may form an electrochemical cell with the first and second conductive layers  311 ,  312  to remove or deposit a conductive material from or onto a surface in contact with the process surface  325 . 
         [0040]    The second conductive layer  312  is stacked on the compressive layer  316  which is stacked on a pad base  310 . The compressive layer  316  is configured to provide compressibility to the pad assembly  322 . The compressive layer  316  is not in fluid communication with the plurality of apertures  309 , therefore, not in contact with the electrolyte during processing. The pad base  310  is configured to support the pad assembly  322 . 
         [0041]    When used in an electrochemical processing, such as electrochemical mechanical polishing or electroplating, the pad assembly  322  presents several advantages over the state of the art pad assemblies. 
         [0042]    First, the pad assembly  322  has a reduced resistance between electrodes, i.e. between the first conductive layer  311  and the second conductive layer  312 . This may be a result of the second conductive layer  312  being a whole piece instead of being distributed in a plurality of discrete members. Additionally, less electrolyte is disposed between the first and second conductive layers  311 ,  312  because height of the plurality of apertures  309  is reduced. In this embodiment, only thickness of the first conductive layer  311  and the insulative layer  314  contributes to the height of the plurality of apertures  309 . 
         [0043]    Second, volume of electrolyte used during processing may be reduced. Again, this may be contributed to the reduced height of the plurality of apertures  309 . The reduced volume of electrolyte used makes it possible to replace the electrolyte and rinse the pad assembly more often without increasing product costs and reducing system throughput. In one embodiment, the electrolyte may be replaced for every substrate during polishing. 
         [0044]    Third, defects on substrates being processed may be reduced because there is less room for storing particles and by products because less layers are exposed to the electrolyte during processing. Particularly, porous layers, such as the compressive layer  316 , are not in fluid communication with the electrolyte. 
         [0045]    Fourth, chemical decomposition is also reduced because less layers are exposed to the electrolyte during processing. Particularly, the compressive layer  316 , which is more prone to decomposition, is not in contact with the electrolyte. 
         [0046]    The first conductive layer  311  may comprise a conductive polymer material. In one embodiment, the first conductive layer  311  comprises a conventional polishing material, such as polymer based pad materials compatible with the process chemistry, examples of which include polyurethane, polycarbonate, fluoropolymers, polytetraflouroethylene(PTFE), polytetraflouroacrylate (PTFA), polyphenylene sulfide (PPS), or combinations thereof. The conventional polishing material may be coated, doped, or impregnated with a process compatible conductive material and/or particles. Alternatively, the first conductive layer  311  may be a conductive polymer, such as a conductive filler material disposed in a conductive polymer matrix, such as fine tin particles in a polyurethane binder, or a conductive fabric, such as carbon fibers in a polyurethane binder. 
         [0047]    In one embodiment, the first conductive layer  311  comprises removal particles adapted to facilitate material removal from the device side of the substrate. In one embodiment, the removal particles are conductive particles, such as particles of tin, copper, nickel, silver, gold, or combinations thereof, in a conductive polymer matrix. In another embodiment, the removal particles are abrasive particles, such as aluminum, ceria, oxides thereof and derivatives thereof, and combinations thereof, in a conductive polymer matrix. In yet another embodiment, the removal particles are a combination of abrasive and conductive particles as described herein and are interspersed within the first conductive layer  311 . The first conductive layer  311  may further include a chamfer, a bevel, a square groove, or combinations thereof, which is adapted to facilitate electrolyte and polishing byproduct transportation. 
         [0048]    The second conductive layer  312  may be fabricated from a conductive material, such as stainless steel, aluminum, gold, silver, copper, tin, nickel, among others. For example, the second conductive layer  312  may be a metal foil, a mesh made of metal wire or metal-coated wire, or a laminated metal layer on a polymer material compatible with the electrolyte, such as a polyimide, polyester, flouroethylene, polypropylene, or polyethylene sheet. In one embodiment, the second conductive layer  312  is configured to provide conformity and sufficient stiffness to allow the pad assembly to remain substantially flat alone, or in combination with the pad base  310 . In one embodiment, the second conductive layer  312  comprises a copper mesh. 
         [0049]    The insulative layer  314  may be fabricated from polymeric materials, such as polyurethane and polyurethane mixed with fillers, polycarbonate, polyphenylene sulfide (PPS), ethylene-propylene-diene-methylene (EPDM), Teflon™ polymers, or combinations thereof, and other polishing materials used in polishing substrate surfaces, such as open or closed-cell foamed polymers, elastomers, felt, impregnated felt, plastics, and like materials compatible with the processing chemistries. 
         [0050]    The compressive layer  316  may be made of a polymer material, such as an open cell foamed polymers, closed cell foamed polymers, a MYLAR® material, heat activated adhesives, or combinations thereof. In one embodiment, the compressive layer  316  may have a hardness of about 20 Shore A to about 90 Shore A. In one embodiment, the foam layer  316  comprises open cell foam, such as a urethane material sold under the trade name PORON®, which is available from the Rogers Corporation. In one embodiment, the foam layer  316  comprises a material under the trade name PORON® 30 or PORON® 35. 
         [0051]    In one embodiment, binding layers  321   a - d  may be used in between the above described layers. The binding layers  321   a - d  may be made of an adhesive that is compatible with process chemistry, such as heat and/or pressure sensitive adhesives known in the art. 
         [0052]      FIG. 4  schematically illustrates a sectional side view of a portion of a pad assembly  422  in accordance with another embodiment of the present invention. 
         [0053]    The pad assembly  422  is similar to the pad assembly  322  illustrated in  FIG. 3  except that the pad assembly  422  comprises a conductive carrier layer  415  between the first conductive layer  311  and the insulative layer  314 . A plurality of discrete members  405  may extend from the second conductive layer  312 . A plurality of apertures  409  may be formed in the space separating the plurality of the discrete members  405 . A processing surface  425  is generally defined by an upper portion of each of the discrete members  405 . 
         [0054]    The conductive carrier layer  415  is configured to improve uniformity across a substrate being processed. In one embodiment, the conductive carrier layer  415  comprises a conductive material, such as stainless steel, aluminum, gold, silver, copper, tin, nickel, among others. For example, the conductive carrier layer  415  may be a metal foil, a mesh made of metal wire or metal coated wire, metal coated fabric, or a laminated metal layer on a polymer material compatible with the electrolyte used in processing, such as a polyimide, polyester, flouroethylene, polypropylenen, or polyethylene sheet. 
         [0055]    While the foregoing is directed to the illustrative embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.